JP2706940B2 - Manufacturing method of non-heat treated steel for nitriding - Google Patents
Manufacturing method of non-heat treated steel for nitridingInfo
- Publication number
- JP2706940B2 JP2706940B2 JP62335374A JP33537487A JP2706940B2 JP 2706940 B2 JP2706940 B2 JP 2706940B2 JP 62335374 A JP62335374 A JP 62335374A JP 33537487 A JP33537487 A JP 33537487A JP 2706940 B2 JP2706940 B2 JP 2706940B2
- Authority
- JP
- Japan
- Prior art keywords
- steel
- nitriding
- strength
- present
- heat treated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は熱間鍛造後、焼入焼もどし等の熱処理を行わ
ずに製造される機械構造用の熱間鍛造用非調質鋼の製造
方法に関するものである。本発明は特に、疲労強度、耐
摩耗性向上のために、窒化処理（ガス窒化、塩浴窒化、
イオン窒化、ガス軟窒化、塩浴軟窒化等）を施して使用
される自動車クランクシャフト、産業車両用リングギヤ
等の機械構造部品に適したものである。
［従来の技術］
従来、自動車用クランクシャフト、産業車両用リング
ギヤ等の機械構造部品に使用されている鋼は、高強度が
要求され、さらに一層の疲労強度、耐摩耗性を得るため
に窒化処理を行う必要があり、窒化性も合わせて要請さ
れる。
そのため、JIS SCM440、SCM445等の中炭素低合金鋼を
熱間でプレス、ハンマー等により成形加工した後に、高
強度を持たせるために焼入焼もどし等の熱処理を行い、
切削加工等で所定の形状に仕上げた後、窒化処理を行い
部品が製造される。
しかし、これらに対して次の問題点が挙げられる。
（１） 焼入、焼もどし処理に大幅なコストがかかる。
（２） 焼入、焼もどし後切削加工がされるために、加
工性が悪く、工具費が増加し、かつ生産性の低下とな
る。
（３） 現用鋼では窒化性がまだ不十分で、窒化処理に
長時間要す。
そこで、これらの問題点が解決できるような鋼が可能
であれば、大幅なコスト低減が図れるとともに、省エネ
ルギー等の社会的要請に応えることができる。
［発明が解決しようとする問題点］
本発明は上記した実状を鑑みてなされたものであり、
その目的は、熱間鍛造のままで焼入、焼もどし処理する
ことなく、熱間鍛造後焼入焼もどし処理したSCM445等の
中炭素低合金鋼と同等もしくは同等以上の強度を確保
し、さらにSCM445等の焼入焼もどし処理材より優れた切
削性を有し、窒化性も良好な窒化用非調質の製造方法を
提供することにある。
［問題点を解決するための手段］
本発明者は、上記目的の下に窒化用非調質鋼の製造方
法について鋭意研究した結果、熱間鍛造のままでは強度
が低く、切削性が良好で、窒化処理によって、母材が時
効硬化し、SCM445等の中炭素低合金鋼の焼入焼もどし材
と同等以上の強度が確保でき、さらに窒化性が良好であ
る窒化用非調質鋼の製造方法を発明した。
特徴としては、第１に低炭素化による靭性向上、第２
にMn、Cr、Moの添加により焼入性を向上させ、熱間鍛造
後放冷するだけで強度と靭性の優れたベイナイト組織を
得る。第３に、ベイナイト組織は一般的に加熱の冷却速
度が変化すると強度も変化し、扱いにくい組織であった
が、これにＶを添加することにより、冷却速度の変化に
対する強度の変化が小さくすることができる。
第４に、Mo、Ｖを複合添加することにより、熱間鍛造
後、放冷のままである程度ベイナイト組織中に固溶して
いたMo、Ｖが窒化処理時の温度にて炭化物として微細析
出し、強度が増加させる時効硬化能が得られる。第５に
低炭素ベイナイト組織はSCM445等の焼入焼もどし材のソ
ルバイト組織に比べて、窒化性に優れ、さらにＶ、Crの
添加により、窒化性を大幅に向上する、という点が上げ
られる。
本発明はこれらの知見によりなされたものである。す
なわち、本発明である窒化用非調質鋼の製造方法のう
ち、第１発明は、重量比でC;0.05〜0.20％、Si;0.10〜
0.50％、Mn;1.50〜2.50％、Cr;0.30〜1.50％、Mo;0.05
〜0.30％、V;0.05〜0.30％を含有し、残部がFeおよび不
純物元素からなり、熱間鍛造後の放冷によりベイナイト
組織とし、その後の窒化処理により表面から深さ0.3mm
の位置でHv510以上となることを要旨とする。
第２発明は、第１発明の製造方法で用いる鋼にさらに
S;0.04〜0.12％、Pb;0.05〜0.30％のうち１種または２
種を含有せしめ、被削性を改善したものであり、第３発
明は、第１発明の製造方法で用いる鋼にNi;0.2％以下を
含有せしめ焼入れ性を改善したものであり、第４発明
は、第３発明の製造方法で用いる鋼にさらにS;0.04〜0.
12％、Pb;0.05〜0.30％のうち１種ないし２種以上を添
加して被削性と同時に焼入れ性を改善するものである。
［作用］
本発明の製造方法の効果について説明すると、本発明
で規定した範囲内の成分を有する鋼を熱間鍛造後放冷す
るだけである程度の強度が確保できるが、強度がSCM445
等の焼入焼もどし材に比べて低いため、切削加工は容易
である。切削加工後、時効処理することにより、強度が
増加し、所定の強度が確保できる。時効処理は単独で行
っても良く、窒化処理と同時に進行させても良い。ま
た、窒化性は良好で、同一窒化条件であれば、従来鋼に
比較して約２倍の窒化層深さが得られ、硬さもビッカー
スで約200〜300上昇し800程度が得られる。そのため従
来鋼と同一の窒化深さを得るのであれば、1/5以下の処
理時間で達成できる。しかしながら、本発明は優れた疲
労強度、耐摩耗性を得ることを特徴としており、熱間鍛
造後の放冷によりベイナイト組織とし、さらに従来とほ
ぼ同程度の時間の窒化処理を施すことにより、窒化処理
後において、表面から深さ0.3mmの位置でHv510以上の高
い硬さの達成を可能としたものである。
次に本発明にかかる窒化用非調質鋼の製造方法の成分
組成を限定理由について説明する。
C;0.05〜0.20％
Ｃは強度を確保するために必要な元素であり0.05％未
満であると強度が不足するので下限を0.05％とした。ま
た、Ｃが0.20％を越えると靭性が低下するので、上限を
0.20％とした。
Si;0.10〜0.50％
Siは製鋼時の脱酸剤として添加されるものであり、0.
10％は必要である。しかし、0.50％を越えると靭性が低
下するので、上限を0.50％とした。
Mn;1.50〜2.50％
Mnは焼入れ性を向上させて組織をベイナイト化するの
に必要な元素である。Mnが1.50％未満であると焼入れ性
が不足しベイナイトの生成が不足し、強度が不足するの
で、下限を1.50％とした。しかし、2.50％を越えると焼
入れ性が向上し過ぎてマルテンサイトが生成され、靭性
が低下するので、上限を2.50％とした。
Cr;0.30〜1.50％
Crは組織をベイナイト化するのに必要な元素であると
共に、窒化層の硬さに寄与するため多いほど良い。0.30
％未満であると前記効果が不充分であるので、下限を0.
30％とした。しかし、1.50％を越えると前記効果が飽和
するとともに、コスト的に高くなるので、上限を1.50％
とした。
Mo;0.05〜0.30％
Moは組織をベイナイト化するために必要であって、さ
らに時効硬化を得るために必要な元素である。Moが0.05
％未満であるとベイナイト化が不充分であるので、下限
を0.05％とした。Moは高価な元素であり、0.30％を越え
ると前記効果が飽和すると共にコスト高となるので、上
限を0.30％とした。
V;0.05〜0.30％
ＶはMoと共に微細な炭化物を析出し時効硬化を起こす
のに必要な元素であり、熱間鍛造後の冷却速度の変化に
対して強度を安定化させる効果がある。0.05％未満では
その効果が不充分なので、下限を0.05％とした。しか
し、0.30％を越えて含有させてもその効果が飽和すると
共にコスト高となるので、上限を0.30％とした。
S;0.04〜0.12％
Ｓは被削性を一層改善するため必要な元素であり、そ
の効果を得るためには0.04％以上が必要である。しか
し、0.12％を越えて含有されてもその効果が飽和し靭性
を低下させるので上限を0.12％とした。
Pb;0.05〜0.30％
Pbは被削性を一層改善するため必要な元素であり、そ
の効果を得るためには0.05％以上が必要である。しか
し、0.30％を越えて含有されてもその被削性改善の効果
の向上が少なくなるので上限を0.30％とした。
Ni;2.0％以下
Niは焼入れ性を一層向上するのに必要な元素である。
しかし、2.0％を越えて含有されても前記効果が飽和し
コスト高となるので、上限を2.0％とした。
［実施例］
本発明の実施例を比較鋼および従来鋼と比較しつつ説
明し本発明の特徴を明らかにする。
（実施例１）
第１表は、本発明の製造方法の成分範囲内の鋼（以
下、本発明鋼又は発明鋼と記す。）、比較鋼および従来
鋼の化学成分を示したものである。第１表においてＡ〜
Ｍ鋼は本発明鋼であって、Ａ〜Ｄ鋼は第１発明、Ｅ〜Ｇ
鋼は第２発明、Ｈ〜Ｊ鋼は第３発明、Ｋ〜Ｍ鋼は第４発
明の各製造方法の成分範囲内の鋼である。Ｎ〜Ｑ鋼は比
較鋼であって、Ｎ鋼はＣが本発明の組成範囲より高い比
較鋼、Ｏ鋼は他の元素は本発明の組成範囲であるがMoを
含有しない比較鋼、Ｐ鋼はMnが本発明の組成範囲より低
い比較鋼、Ｑ鋼は他の元素は本発明の組成範囲であるが
Ｖを含有しない比較鋼である。また、Ｒ鋼は従来鋼であ
ってその組成はSCM445に相当する。
第１表の発明鋼および比較鋼をを50mm直径の棒鋼と
し、これを1250℃に加熱した後、約1100℃で熱間鍛造を
行い、これより30mm直径の棒鋼を形成し、その後自然冷
却した。この棒鋼からJIS4号試験片を作製し、この試験
片について引張強さ、0.2％耐力および硬度を測定し
た。また、従来鋼のＲ鋼は、30mm直径の棒鋼に形成した
後850℃にて油焼入後、620℃にて焼もどしを行い、同様
に試験片を製作して引張強さ、0.2％耐力および硬度を
測定した。続いて前記の30mm直径の棒鋼を550℃で30時
間の時効処理を施し、同様に試験片を製作して引張強
さ、0.2％耐力および硬度を測定した。測定した結果は
第２表に示した。
（実施例２）
第１表の発明鋼および比較鋼を50mm直径の棒鋼とし、
これを1250℃に加熱した後、約1100℃で熱間鍛造を行
い、これより30mm直径の棒鋼を形成し、その後自然冷却
した。また、従来鋼Ｒ鋼は、実施例１と同様の焼入焼も
どしを行った。この棒鋼から10mm角のブロックを切削加
工し、N2:H2＝1:1のガス組成の条件のもとで550℃で30
時間イオン窒化処理を行い、表面から0.3mmの距離の硬
度を測定し、第２表に合わせて示した。また、窒化層の
深さを比較するため、本発明鋼のＤ鋼と従来鋼Ｒ鋼につ
いて表面から0.05mm毎に硬度を測定し、結果を第１図に
示した。
第１図から明らかなように、本発明鋼は従来鋼に比較
して、約２倍の窒化深さが得られ、表面硬さもビッカー
スで約200〜300上昇していることが確認された。その結
果、表面から0.3mmの位置における硬さは従来に比べ著
しく向上し、Hv510以上という従来では得られない高い
硬さを得ることができる。
（実施例３）
第１表に示した発明鋼および比較鋼について、実施例
１の鍛造を施したままの状態で、従来鋼Ｒ鋼については
実施例１と同様の焼入焼もどしを行った状態で、ドリル
穿孔試験を行った。なお、ドリルの材質はSKH9、ドリル
回転数は1710rpm、切削油なし、荷重75kg、ドリルは5mm
φストレートシャンクを用いた。測定した結果は第２表
に示したが、従来鋼のＲ鋼の定荷重単位時間穿孔距離を
100とし、それぞれの穿孔距離を整数比で示した。
第２表に示した実施例１、実施例２および実施例３の
結果から、本発明鋼はいずれも鍛造のままでは引張強
さ、硬さは従来鋼Ｒ鋼に比べて低いが、時効処理後は引
張強さ、0.2％耐力、硬さのいずれも増加しており、特
に張引強さは90kgf/mm2以上を確保しており、従来鋼Ｒ
鋼と同等以上の強度を有することが分かる。また、窒化
性は第２表の窒化後強度および第１図の窒化層硬さ分布
より、本発明鋼は従来鋼Ｒ鋼に比べて非常に優れている
ことがわかる。
切削性にいても従来鋼Ｒ鋼に比べて、本発明鋼は非常
に良好で、特にＳ、Pbを添加した第２発明、第４発明は
その効果が大きく表れている。比較鋼Ｎ鋼は強度が高す
ぎて切削性が悪い、Ｏ鋼およびＰ鋼はいずれも焼入性が
不足しており、フェライト・ベイナイト組織となり、強
度が低い。また、Ｑ鋼は時効硬化せずに時効処理により
軟化して、強度が不足している。
［発明の効果］
本発明の窒化用非調質鋼の製造方法は以上説明したよ
うに、従来のSCM445等の中炭素低合金構造用鋼の熱処理
コストを低減し、切削加工性および窒化性の改善すべく
なされたもので、低炭素化により靭性を向上し、Mn、C
r、Moの添加により焼入性を向上して熱間鍛造後の放冷
によって強度と靭性を優れたベイナイト組織とし、Ｖを
添加することにより冷却速度の変化に対する強度の変化
を小さくし、MoとＶとの複合添加によって窒化処理時の
微細炭化物の析出により時効硬化能を付与し、Ｖ、Crに
より窒化性を大幅に改善したものであって、熱間鍛造後
放冷するだけである程度の強度を確保し、その強度はSC
M445材の焼入焼もどし材より低いので切削加工が容易で
あり、その後の窒化処理または時効処理により強度は増
加するが、同一窒化条件であれば従来鋼に比較して約２
倍の窒化深さが得られ、硬さもビッカースで約200〜300
上昇し800程度が得られ、従来鋼で得られる硬さと同一
の硬さを得るのであれば、窒化処理時間を大幅に短縮す
ることができる。本発明では、従来とほぼ同程度の処理
条件で窒化処理を施すことによって、表面から0.3mmの
位置における硬さをHv510以上とすることができ、従来
鋼に窒化処理を施した場合に比べ、大幅に優れた疲労強
度と耐摩耗性が得られるものである。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the production of non-heat treated steel for hot forging for machine structures manufactured without performing heat treatment such as quenching and tempering after hot forging. It is about the method. In particular, the present invention provides a nitriding treatment (gas nitriding, salt bath nitriding,
It is suitable for mechanical structural parts such as automobile crankshafts and ring gears for industrial vehicles which are used after being subjected to ion nitriding, gas nitrocarburizing, salt bath nitrocarburizing, etc. [Prior art] Steels conventionally used for mechanical structural parts such as crankshafts for automobiles and ring gears for industrial vehicles are required to have high strength, and are subjected to nitriding treatment in order to obtain further fatigue strength and wear resistance. And nitridation is also required. Therefore, medium-carbon low-alloy steel such as JIS SCM440, SCM445 is hot pressed, formed by a hammer, etc., and then subjected to heat treatment such as quenching and tempering to have high strength.
After finishing to a predetermined shape by cutting or the like, a part is manufactured by performing a nitriding treatment. However, there are the following problems. (1) Quenching and tempering treatments require significant costs. (2) Since cutting is performed after quenching and tempering, workability is poor, tool cost is increased, and productivity is reduced. (3) The nitriding property of the working steel is still insufficient, and it takes a long time for the nitriding treatment. Therefore, if steel capable of solving these problems is possible, it is possible to significantly reduce costs and meet social demands such as energy saving. [Problems to be Solved by the Invention] The present invention has been made in view of the above situation,
The purpose is to maintain the strength equal to or higher than that of medium carbon low alloy steel such as SCM445 which has been quenched and tempered after hot forging without quenching and tempering with hot forging, and An object of the present invention is to provide a non-refining method for nitriding, which has superior machinability and a good nitriding property than a quenched and tempered material such as SCM445. [Means for Solving the Problems] The present inventor has conducted intensive studies on a method for producing a non-heat treated steel for nitriding under the above-mentioned object. Manufacture of non-heat treated steel for nitriding, in which the base metal age hardens by nitriding treatment, ensuring the same or higher strength as the quenched and tempered material of medium carbon low alloy steel such as SCM445, and good nitriding properties. Invented a method. The features are: first, improvement in toughness due to low carbon;
By adding Mn, Cr, and Mo, the hardenability is improved, and a bainite structure excellent in strength and toughness is obtained only by cooling after hot forging. Third, in general, the bainite structure is difficult to handle because the strength changes when the cooling rate of heating changes, but by adding V to the bainite structure, the change in strength with respect to the change in cooling rate is reduced. be able to. Fourth, by adding Mo and V in a complex manner, after hot forging, Mo and V which had been solid-dissolved in the bainite structure to some extent while leaving to cool were finely precipitated as carbides at the temperature during the nitriding treatment. Age hardening ability to increase the strength is obtained. Fifth, the low carbon bainite structure is superior to the sorbite structure of a quenched and tempered material such as SCM445 in that the nitriding property is excellent, and the addition of V and Cr significantly improves the nitriding property. The present invention has been made based on these findings. That is, in the method for producing a non-heat treated steel for nitriding according to the present invention, the first invention is such that, by weight ratio, C; 0.05 to 0.20%, and Si;
0.50%, Mn; 1.50 to 2.50%, Cr; 0.30 to 1.50%, Mo; 0.05
0.30%, V; 0.05 to 0.30%, the balance being Fe and impurity elements, leaving a bainite structure by cooling after hot forging, and a depth of 0.3 mm from the surface by subsequent nitriding.
The point is that it becomes Hv510 or more at the position of. The second invention further relates to the steel used in the production method of the first invention.
S; 0.04 to 0.12%, Pb; one or two of 0.05 to 0.30%
The third invention is to improve the machinability by containing a seed, and the third invention is to improve the hardenability by containing Ni; 0.2% or less in the steel used in the production method of the first invention. Is further added to the steel used in the production method of the third invention by S;
One or two or more of 12% and Pb; 0.05 to 0.30% are added to improve machinability and hardenability at the same time. [Operation] To explain the effect of the production method of the present invention, a steel having a component within the range specified in the present invention can be secured to a certain degree of strength only by being allowed to cool after hot forging.
Cutting is easy because it is lower than quenched and tempered materials such as. By performing aging treatment after cutting, the strength is increased and a predetermined strength can be secured. The aging treatment may be performed alone or may proceed simultaneously with the nitriding treatment. In addition, the nitriding properties are good, and under the same nitriding conditions, a nitride layer depth approximately twice as large as that of conventional steel is obtained, and the hardness is increased by about 200 to 300 by Vickers to about 800. Therefore, if the same nitriding depth as that of the conventional steel is obtained, it can be achieved in a processing time of 1/5 or less. However, the present invention is characterized by obtaining excellent fatigue strength and abrasion resistance.It is characterized by obtaining a bainite structure by cooling after hot forging, and further performing a nitriding treatment for substantially the same time as the conventional one. After the treatment, a high hardness of Hv510 or more can be achieved at a depth of 0.3 mm from the surface. Next, the reasons for limiting the component composition of the method for producing a non-heat treated steel for nitriding according to the present invention will be described. C: 0.05 to 0.20% C is an element necessary for securing the strength, and if it is less than 0.05%, the strength is insufficient, so the lower limit was made 0.05%. If C exceeds 0.20%, the toughness decreases.
0.20%. Si: 0.10 to 0.50% Si is added as a deoxidizing agent during steel making.
10% is needed. However, if it exceeds 0.50%, the toughness decreases, so the upper limit was made 0.50%. Mn: 1.50 to 2.50% Mn is an element necessary for improving hardenability and turning the structure into bainite. If Mn is less than 1.50%, the hardenability is insufficient, the formation of bainite is insufficient, and the strength is insufficient, so the lower limit was set to 1.50%. However, when the content exceeds 2.50%, the hardenability is excessively improved, and martensite is generated, and the toughness is reduced. Therefore, the upper limit is set to 2.50%. Cr; 0.30 to 1.50% Cr is an element necessary for turning the structure into bainite, and contributes to the hardness of the nitrided layer. 0.30
%, The effect is insufficient.
30%. However, if the content exceeds 1.50%, the effect is saturated and the cost increases, so the upper limit is set to 1.50%.
And Mo; 0.05 to 0.30% Mo is an element necessary to bainite the structure and is also necessary to obtain age hardening. Mo is 0.05
%, Bainitization is insufficient, so the lower limit was made 0.05%. Mo is an expensive element, and if it exceeds 0.30%, the above effect is saturated and the cost increases, so the upper limit was made 0.30%. V: 0.05 to 0.30% V is an element necessary for precipitating fine carbides together with Mo and causing age hardening, and has an effect of stabilizing strength against a change in cooling rate after hot forging. If it is less than 0.05%, the effect is insufficient, so the lower limit was made 0.05%. However, if the content exceeds 0.30%, the effect is saturated and the cost increases, so the upper limit is set to 0.30%. S: 0.04 to 0.12% S is an element necessary for further improving the machinability, and 0.04% or more is required to obtain the effect. However, if the content exceeds 0.12%, the effect is saturated and the toughness is reduced, so the upper limit is made 0.12%. Pb: 0.05 to 0.30% Pb is an element necessary for further improving machinability, and 0.05% or more is required to obtain its effect. However, if the content exceeds 0.30%, the effect of improving machinability is reduced, so the upper limit is set to 0.30%. Ni: 2.0% or less Ni is an element necessary for further improving the hardenability.
However, if the content exceeds 2.0%, the effect is saturated and the cost increases, so the upper limit was made 2.0%. [Examples] Examples of the present invention will be described in comparison with comparative steels and conventional steels to clarify the features of the present invention. (Example 1) Table 1 shows the chemical components of steel (hereinafter referred to as steel of the present invention or steel of the present invention), comparative steel and conventional steel within the component range of the production method of the present invention. In Table 1, A ~
M steel is the present invention steel, A to D steel are the first invention, EG
Steel is the second invention, H to J steels are the third inventions, and K to M steels are steels within the composition ranges of the respective manufacturing methods of the fourth invention. N to Q steels are comparative steels, N steel is a comparative steel in which C is higher than the composition range of the present invention, O steel is a comparative steel in which other elements are in the composition range of the present invention but do not contain Mo, and P steel is Is a comparative steel in which Mn is lower than the composition range of the present invention, and Q steel is a comparative steel in which other elements are in the composition range of the present invention but do not contain V. The R steel is a conventional steel and its composition corresponds to SCM445. The invention steels and comparative steels in Table 1 were 50 mm diameter steel bars, which were heated to 1250 ° C., hot forged at about 1100 ° C. to form 30 mm diameter steel bars, and then naturally cooled. . A JIS No. 4 test piece was prepared from this steel bar, and the tensile strength, 0.2% proof stress and hardness of this test piece were measured. The conventional R steel is formed into a 30 mm diameter steel bar, then oil quenched at 850 ° C, tempered at 620 ° C, and similarly prepares test specimens to obtain tensile strength and 0.2% proof stress. And hardness were measured. Subsequently, the aforementioned 30 mm diameter steel bars were subjected to aging treatment at 550 ° C. for 30 hours, and test pieces were prepared in the same manner, and the tensile strength, 0.2% proof stress and hardness were measured. The measured results are shown in Table 2. (Example 2) Inventive steel and comparative steel in Table 1 were 50 mm diameter steel bars,
After heating this to 1250 ° C, hot forging was performed at about 1100 ° C to form a 30 mm diameter steel bar, which was then naturally cooled. Further, the conventional steel R steel was subjected to the same quenching and tempering as in Example 1. A 10 mm square block is cut from this steel bar and subjected to 30 ° C at 550 ° C under the conditions of N 2 : H 2 = 1: 1 gas composition.
The hardness was measured at a distance of 0.3 mm from the surface by performing the ion nitriding treatment for a time, and the hardness is shown in Table 2. Further, in order to compare the depths of the nitrided layers, the hardness was measured every 0.05 mm from the surface of the steel D of the present invention and the conventional steel R, and the results are shown in FIG. As is clear from FIG. 1, it was confirmed that the steel of the present invention had about twice the nitriding depth as compared with the conventional steel, and the surface hardness was increased by about 200 to 300 by Vickers. As a result, the hardness at a position of 0.3 mm from the surface is remarkably improved as compared with the related art, and a high hardness of Hv510 or more, which cannot be obtained by the related art, can be obtained. (Example 3) With respect to the inventive steel and comparative steel shown in Table 1, the same quenching and tempering as in Example 1 was performed on the conventional steel R steel in a state where the forging of Example 1 was performed. In this state, a drilling test was performed. The drill material is SKH9, the drill speed is 1710rpm, no cutting oil, load is 75kg, drill is 5mm
φ straight shank was used. Table 2 shows the measurement results.
The perforation distance was indicated by an integer ratio with 100. From the results of Example 1, Example 2 and Example 3 shown in Table 2, the steel of the present invention has a lower tensile strength and hardness as forged as compared with the conventional steel R, but the aging treatment. After that, the tensile strength, 0.2% proof stress, and hardness have all increased. In particular, the tensile strength has secured 90 kgf / mm 2 or more.
It turns out that it has strength equal to or higher than steel. Further, from the strength after nitriding in Table 2 and the hardness distribution of the nitrided layer in FIG. 1, the nitriding property shows that the steel of the present invention is much superior to the conventional steel R. As for the machinability, the steel of the present invention is very good as compared with the conventional steel R, and the effects of the second and fourth inventions to which S and Pb are added are particularly remarkable. Comparative steel N steel has too high strength and poor machinability, and both O steel and P steel have insufficient hardenability, have a ferrite bainite structure, and have low strength. Further, the Q steel is not age-hardened, but is softened by the aging treatment, and has insufficient strength. [Effect of the Invention] As described above, the method for producing a non-heat treated steel for nitridation of the present invention reduces the heat treatment cost of conventional medium carbon low alloy structural steels such as SCM445, and reduces the machinability and nitriding property. Mn, C
r, the addition of Mo enhances the hardenability and allows the bainite structure to have excellent strength and toughness by cooling after hot forging, and the addition of V reduces the change in strength with respect to the change in cooling rate. The addition of V and V gives age hardening ability by precipitation of fine carbides at the time of nitriding, and significantly improves nitriding by V and Cr. Secure the strength, the strength is SC
Since it is lower than the quenched and tempered M445 material, cutting is easy, and the strength is increased by the subsequent nitriding or aging treatment.
Double nitriding depth is obtained, and hardness is about 200-300 by Vickers
If the hardness is increased to about 800 and the same hardness as that obtained by the conventional steel is obtained, the nitriding time can be significantly reduced. In the present invention, the hardness at a position of 0.3 mm from the surface can be set to Hv510 or more by performing the nitriding treatment under substantially the same processing conditions as the conventional, and compared with the case where the conventional steel is subjected to the nitriding treatment. It can provide significantly superior fatigue strength and wear resistance.
【図面の簡単な説明】
第１図は本発明の製造方法の範囲内の成分であるＤ鋼と
従来鋼であるＲ鋼に対し、同一の窒化処理を施した場合
における表面からの距離と硬さの関係を示す図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the distance from the surface and the hardness when the same nitriding treatment is applied to D steel, which is a component within the production method of the present invention, and R steel, which is a conventional steel. It is a figure which shows the relationship of a height.
Claims (1)
1.50〜2.50％、Cr;0.3〜1.5％、Mo;0.05〜0.30％、V;0.
05〜0.30％を含有し、残部Feおよび不純物元素からなる
鋼を熱間鍛造後冷却してベイナイト組織と、その後の窒
化処理により表面から深さ0.3mmの位置でHv510以上とな
ることを特徴とする窒化用非調質鋼の製造方法。 ２．重量比で、C;0.05〜0.20％、Si;0.10〜0.50％、Mn;
1.50〜2.50％、Cr;0.3〜1.5％、Mo;0.05〜0.30％、V;0.
05〜0.30％を含有し、さらにS;0.04〜0.12％、Pb;0.05
〜0.30％のうち１種ないし２種以上を含有し、残部Feお
よび不純物元素からなる鋼を熱間鍛造後冷却してベイナ
イト組織とし、その後の窒化処理により表面から深さ0.
3mmの位置でHv510以上となることを特徴とする窒化用非
調質鋼の製造方法。 ３．重量比で、C;0.05〜0.20％、Si;0.10〜0.50％、Mn;
1.50〜2.50％、Cr;0.3〜1.5％、Mo;0.05〜0.30％、V;0.
05〜0.30％、Ni;2.0％以下を含有し、残部Feおよび不純
物元素からなる鋼を熱間鍛造後放冷してベイナイト組織
とし、その後の窒化処理により表面から深さ0.3mmの位
置でHv510以上となることを特徴とする窒化用非調質鋼
の製造方法。 ４．重量比で、C;0.05〜0.20％、Si;0.10〜0.50％、Mn;
1.50〜2.50％、Cr;0.3〜1.5％、Mo;0.05〜0.30％、V;0.
05〜0.30％、Ni;2.0％以下を含有し、さらにS;0.04〜0.
12％、Pb;0.05〜0.30％のうち１種ないし２種以上を含
有し、残部Feおよび不純物元素からなる鋼を熱間鍛造後
冷却してベイナイト組織とし、その後の窒化処理により
表面から深さ0.3mmの位置でHv510以上となることを特徴
とする窒化用非調質鋼の製造方法。(57) [Claims] By weight, C; 0.05-0.20%, Si; 0.10-0.50%, Mn;
1.50-2.50%, Cr; 0.3-1.5%, Mo; 0.05-0.30%, V;
A steel containing 0.05 to 0.30%, with the balance being Fe and impurity elements, is hot forged and then cooled to have a bainite structure, and the nitriding treatment makes it Hv 510 or more at a depth of 0.3 mm from the surface. Of producing non-heat treated steel for nitriding. 2. By weight, C; 0.05-0.20%, Si; 0.10-0.50%, Mn;
1.50-2.50%, Cr; 0.3-1.5%, Mo; 0.05-0.30%, V;
0.05-0.30%, S; 0.04-0.12%, Pb; 0.05
The steel containing one or more of 0.30% and the balance of Fe and impurity elements is hot forged and then cooled to form a bainite structure.
A method for producing a non-heat treated steel for nitriding, wherein Hv 510 or more is obtained at a position of 3 mm. 3. By weight, C; 0.05-0.20%, Si; 0.10-0.50%, Mn;
1.50-2.50%, Cr; 0.3-1.5%, Mo; 0.05-0.30%, V;
A steel containing 0.05 to 0.30%, Ni; 2.0% or less, and the balance consisting of Fe and impurity elements is allowed to cool and then allowed to cool to a bainite structure. A method for producing a non-heat treated steel for nitriding characterized by the above. 4. By weight, C; 0.05-0.20%, Si; 0.10-0.50%, Mn;
1.50-2.50%, Cr; 0.3-1.5%, Mo; 0.05-0.30%, V;
0.05-0.30%, Ni; contains 2.0% or less, and further contains S; 0.04--0.
12%, Pb; containing one or two or more of 0.05 to 0.30%, the steel consisting of the balance Fe and impurity elements is hot forged and then cooled to form a bainite structure. A method for producing a non-heat treated steel for nitriding, wherein Hv 510 or more is obtained at a position of 0.3 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62335374A JP2706940B2 (en) | 1987-12-30 | 1987-12-30 | Manufacturing method of non-heat treated steel for nitriding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62335374A JP2706940B2 (en) | 1987-12-30 | 1987-12-30 | Manufacturing method of non-heat treated steel for nitriding |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01177338A JPH01177338A (en) | 1989-07-13 |
| JP2706940B2 true JP2706940B2 (en) | 1998-01-28 |
Family
ID=18287823
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62335374A Expired - Lifetime JP2706940B2 (en) | 1987-12-30 | 1987-12-30 | Manufacturing method of non-heat treated steel for nitriding |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2706940B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2743116B2 (en) * | 1990-07-27 | 1998-04-22 | 愛知製鋼 株式会社 | Non-heat treated steel for hot forging |
| US6083455A (en) * | 1998-01-05 | 2000-07-04 | Sumitomo Metal Industries, Ltd. | Steels, steel products for nitriding, nitrided steel parts |
| JP3527154B2 (en) * | 1999-11-05 | 2004-05-17 | 株式会社住友金属小倉 | Non-heat treated nitrocarburized steel parts |
| EP3115477B1 (en) | 2014-03-05 | 2020-04-08 | Daido Steel Co.,Ltd. | Age hardening non-heat treated bainitic steel |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6040504B2 (en) * | 1979-06-02 | 1985-09-11 | 大同特殊鋼株式会社 | Resistance alloy soft chamber steel with excellent machinability |
| JPS5916949A (en) * | 1982-07-16 | 1984-01-28 | Sumitomo Metal Ind Ltd | Soft-nitriding steel |
| JPS5950158A (en) * | 1982-09-13 | 1984-03-23 | Sanyo Tokushu Seikou Kk | Soft-nitriding low alloy steel |
| JPS59179759A (en) * | 1983-03-31 | 1984-10-12 | Daido Steel Co Ltd | Soft-nitriding steel |
-
1987
- 1987-12-30 JP JP62335374A patent/JP2706940B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01177338A (en) | 1989-07-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4385019B2 (en) | Manufacturing method for steel nitrocarburized machine parts | |
| KR101726251B1 (en) | Steel for nitrocarburizing and nitrocarburized component, and methods for producing said steel for nitrocarburizing and said nitrocarburized component | |
| EP2444511A1 (en) | Steel for nitriding and nitrided steel components | |
| JP5258458B2 (en) | Gears with excellent surface pressure resistance | |
| JP4737601B2 (en) | High temperature nitriding steel | |
| JP6225965B2 (en) | Soft nitriding steel and parts, and methods for producing them | |
| JPH09324241A (en) | Steel for sort-nitriding, soft-nitrided parts and its production | |
| JPH10219393A (en) | Steel material for soft-nitriding, soft-nitrided parts, and their production | |
| JP2706940B2 (en) | Manufacturing method of non-heat treated steel for nitriding | |
| JP2007146233A (en) | Method for manufacturing structural parts for automobile made from steel | |
| JPH10226817A (en) | Production of steel for soft-nitriding and soft-nitrided parts using this steel | |
| JPH11229032A (en) | Production of steel for soft-nitriding and soft-nitrided parts using the steel | |
| JP2019104972A (en) | Carburized component | |
| JP6447064B2 (en) | Steel parts | |
| JPH10226818A (en) | Production of steel for soft-nitriding and soft-nitrided parts using this steel | |
| JP2006292108A (en) | Crank shaft and its manufacturing method | |
| JPH04154936A (en) | Precipitation hardening nitriding steel | |
| JP2003113419A (en) | Method for manufacturing hot forged component of non- heat treated steel, and hot forged component of non- heat treated steel | |
| JP3901504B2 (en) | Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability | |
| JP3849296B2 (en) | Method of manufacturing steel for nitrocarburizing and nitrocarburized component using the steel | |
| JP3855418B2 (en) | Method of manufacturing nitrocarburizing steel material and nitrocarburized component using the steel material | |
| JP4723338B2 (en) | Steel for induction-hardened gears excellent in impact characteristics, bending fatigue characteristics, and surface fatigue characteristics, and a manufacturing method of gears | |
| CN115026517B (en) | Planetary gear shaft, special material for planetary gear shaft and hot forging forming process of special material | |
| WO2021090799A1 (en) | Crankshaft,and method for manufacturing rough-shape material for crankshaft | |
| JPH07102340A (en) | Production of non-heattreated steel excellent in fatigue characteristic |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20081017 Year of fee payment: 11 |
|
| EXPY | Cancellation because of completion of term | ||
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20081017 Year of fee payment: 11 |