JPH09227992A - Soft-nitriding steel for structural purpose - Google Patents
Soft-nitriding steel for structural purposeInfo
- Publication number
- JPH09227992A JPH09227992A JP5411496A JP5411496A JPH09227992A JP H09227992 A JPH09227992 A JP H09227992A JP 5411496 A JP5411496 A JP 5411496A JP 5411496 A JP5411496 A JP 5411496A JP H09227992 A JPH09227992 A JP H09227992A
- Authority
- JP
- Japan
- Prior art keywords
- hardness
- nitriding
- soft
- steel
- fatigue strength
- 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.)
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、ギヤ、シャフト
等高強度精密部品をはじめとする様々な機械構造用部品
用としての軟窒化用構造用鋼に関し、とくに軟窒化処理
によって硬化層を形成させた後、ショットピーニングを
施して使用するための優れた疲労強度と、良好な被削性
を有し、熱処理歪みの小さい軟窒化用構造用鋼に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structural steel for soft nitriding for various mechanical structural parts such as high strength precision parts such as gears and shafts. The present invention relates to a structural steel for soft nitriding, which has excellent fatigue strength for use after shot peening and has good machinability and has a small heat treatment strain.
【０００２】[0002]
【従来の技術】従来、表面硬化処理方法としては、浸炭
処理と、ガス窒化、軟窒化等をはじめとする窒化処理と
が代表的なものである。2. Description of the Related Art Conventionally, carburizing treatment and nitriding treatment such as gas nitriding and soft nitriding have been representatively used as a surface hardening treatment method.
【０００３】ギヤ、シャフト等高負荷のかかる機械構造
用精密部品には、小型軽量化、高強度化の目的で深い硬
化層を持つ浸炭材が使用されるのが一般的である。Carburizing materials having a deep hardened layer are generally used for precision parts for mechanical structures, such as gears and shafts, which are subject to high loads, in order to reduce the size and weight and increase the strength.
【０００４】浸炭処理は高温のγ域において、炭素を侵
入、拡散させるため、深い硬化深さが得られるが、浸炭
後に焼入れ焼戻しの熱処理が必要なために熱処理歪みが
大きくなり、厳しい寸法精度の要求されるギヤ等の機械
構造用部品に使用するには問題があった。また、耐焼付
性や耐かじり性にも難点があった。In the carburizing treatment, carbon penetrates and diffuses in the high temperature γ range, so that a deep hardening depth can be obtained. However, since heat treatment for quenching and tempering is required after carburizing, heat treatment distortion becomes large, and strict dimensional accuracy is required. There was a problem in using it for required mechanical parts such as gears. In addition, there are problems in seizure resistance and galling resistance.
【０００５】これに対し、窒化処理は、Ａ1 変態点以下
の温度域での処理であり、必ずしも焼入を必要としない
ため、熱処理歪みが少なく、また高い表面硬さの硬化層
が得られ、耐磨耗性、耐焼付性にも優れている。特に軟
窒化は、ガス窒化に比べ化合物層や処理時間の点で有利
なため、低熱処理歪性を生かし機械構造用部品や金型な
どに急速に普及しつつある。On the other hand, the nitriding treatment is a treatment in a temperature range below the A 1 transformation point and does not necessarily require quenching, so that a heat treatment distortion is small and a hardened layer having a high surface hardness can be obtained. It also has excellent wear resistance and seizure resistance. In particular, soft nitriding is more advantageous than gas nitriding in terms of a compound layer and a treatment time, so that it is rapidly spreading to machine structural parts, dies, etc. by taking advantage of low heat treatment distortion.
【０００６】しかし、従来より、軟窒化処理に用いられ
ている構造用炭素鋼や低合金鋼では、十分な硬化深さと
深部硬さが得られず、耐ピッチング性や耐スポーリング
性、疲労強度が大きな問題となっていた。However, conventional structural carbon steels and low alloy steels used for soft nitriding cannot provide sufficient hardening depth and deep hardness, resulting in pitting resistance, spalling resistance and fatigue strength. Was a big problem.
【０００７】また、軟窒化処理は、鍛造のまま、あるい
は焼きならし後に行われることが多く、部品強度を上げ
るために芯部強度を上げることはそのまま軟窒化前の素
材硬さを上げることにつながり、特に機械構造用鋼とし
ては素材状態での加工性が問題となっていた。Further, the soft nitriding treatment is often performed as it is forged or after normalizing. Therefore, increasing the core strength to increase the strength of parts directly increases the material hardness before soft nitriding. In particular, workability in the material state has been a problem for steel for machine structural use.
【０００８】一方、ショットピーニング処理は比較的容
易にしかも低コストで疲労強度を向上させる処理として
浸炭歯車などに適用されつつある。ところが窒化部品に
ショットピーニング処理を施すと、表面にクラックが生
じてしまい疲労強度を十分高めることができないことが
知られていた。On the other hand, the shot peening treatment is being applied to carburized gears and the like as a treatment for improving fatigue strength relatively easily and at low cost. However, it has been known that when the nitrided component is subjected to shot peening, cracks occur on the surface and the fatigue strength cannot be sufficiently increased.
【０００９】そこで、この問題を解決するための技術が
特開平２−１４９６１６で提案されている。この方法
は、鋼を熱間鍛造後冷却或いは前処理によりベイナイト
を主体とする金属組織とし、窒化処理又は軟窒化処理を
施した後、ショット径／窒化化合物膜厚＝１５〜６０、
ショット硬さ＝４５〜６０HRC 、ショット速度＝５０〜
１２０ｍ／ｓｅｃのショット条件でショットピーニング
を施すものである。Therefore, a technique for solving this problem is proposed in Japanese Patent Laid-Open No. 2-149616. According to this method, steel is made into a metal structure mainly composed of bainite by cooling or pretreatment after hot forging, and after nitriding treatment or soft nitriding treatment, shot diameter / nitride compound film thickness = 15 to 60,
Shot hardness = 45-60 HRC, shot speed = 50-
Shot peening is performed under a shot condition of 120 m / sec.
【００１０】ところで、さらにこの方法において、機械
構造用の高強度精密部品の製造上から鋼の被削性を向上
させる必要がある。しかし、被削性などの加工性を向上
させるためには、一般にＳ、Ｐｂ等の快削性元素を添加
する手法が広く用いられている。しかし、Ｐｂを添加す
ることにより、特に軟窒化材にショットピーニングを施
したときの疲労強度が、非Ｐｂ鋼に対して低下してしま
う問題があることを、発明者らは見いだした。そして、
化学成分と不純物を十分にコントロールすることによっ
て良好な被削性と優れた疲労強度を併せ持たせること
が、可能となることを発見した。By the way, in this method, it is necessary to improve the machinability of steel from the viewpoint of manufacturing high strength precision parts for machine structures. However, in order to improve machinability such as machinability, a method of adding a free-machining element such as S or Pb is generally widely used. However, the inventors have found that the addition of Pb causes a problem that the fatigue strength, particularly when shot peening is applied to the soft nitride material, is reduced as compared with the non-Pb steel. And
It has been discovered that it is possible to combine good machinability and excellent fatigue strength by adequately controlling chemical components and impurities.
【００１１】[0011]
【発明が解決しようとする課題】本発明が解決しようと
する課題は、上記問題点を解消することであり、良好な
被削性と優れた疲労強度を有し、熱処理歪の小さい軟窒
化用構造用鋼を提供することである。The problem to be solved by the present invention is to solve the above-mentioned problems, and it has good machinability and excellent fatigue strength, and is used for nitrocarburizing with a small heat treatment strain. The purpose is to provide structural steel.
【００１２】[0012]
【課題を解決するための手段】上記の課題を解決するた
めの本発明の手段は、重量比で、Ｃ：０．２０〜０．５
０％、Ｓｉ：０．０３〜０．５０％、Ｍｎ：０．３０〜
３．００％、Ｃｒ：０．１０〜１．００％、Ｍｏ：０．
０３〜１．００％、Ａｌ：０．０１〜０．１０％、Ｖ：
０．０３〜０．５０％、Ｓ：０．０１５〜０．０７０
％、Ｐｂ：０〜０．０４０％、Ｏ：１５ｐｐｍ以下を含
有すると共に、Ｓ、Ｐｂの含有量が、式 1.5S(%)+Pb(%)≧(9/10000) ×目標素材硬さ(HB)-0.22 但し、目標素材硬さ：２４０ＨＢ〜３３０ＨＢ を満足し、Ｓ、Ｐｂ、酸素の含有量が、式 0.5S(%)+Pb(%)+40酸素(%)≦(8/10000) ×目標芯部硬さ
(HV)-0.11 但し、目標芯部硬さ：２５０ＨＶ〜３５０ＨＶ を満足し、残部がＦｅおよび不可避不純物よりなり、圧
延まま、鍛造まま、焼きならし等の状態で機械加工を施
した後、軟窒化処理とショットピーニングを施すことに
適した、疲労強度と被削性に優れた軟窒化用構造用鋼を
用いることである。Means for Solving the Problems The means of the present invention for solving the above problems are C: 0.20 to 0.5 by weight ratio.
0%, Si: 0.03 to 0.50%, Mn: 0.30
3.00%, Cr: 0.10-1.00%, Mo: 0.
03-1.00%, Al: 0.01-0.10%, V:
0.03-0.50%, S: 0.015-0.070
%, Pb: 0 to 0.040%, O: 15 ppm or less, and the content of S and Pb is expressed by the formula 1.5S (%) + Pb (%) ≧ (9/10000) × target material hardness (HB) -0.22 However, the target material hardness: 240HB to 330HB is satisfied, and the contents of S, Pb and oxygen are calculated by the formula 0.5S (%) + Pb (%) + 40 oxygen (%) ≦ (8 / 10000) × target core hardness
(HV) -0.11 However, the target core hardness: 250HV to 350HV is satisfied, the balance consists of Fe and unavoidable impurities, and it is softened after being machined in as-rolled, as-forged, or-normalized state. It is to use structural steel for soft nitriding, which is suitable for nitriding and shot peening and has excellent fatigue strength and machinability.
【００１３】すなわち、重量比で、Ｃ：０．２０〜０．
５０％、Ｓｉ：０．０３〜０．５０％、Ｍｎ：０．３０
〜３．００％、Ｃｒ：０．１０〜１．００％、Ｍｏ：
０．０３〜１．００％、Ａｌ：０．０１〜０．１０％、
Ｖ：０．０３〜０．５０％となるように鋼に添加するこ
とによって、圧延まま、鍛造まま、焼きならし等の状態
で、例えば５７０℃×１０時間の軟窒化処理を施し、芯
部硬さ２５０ＨＶ以上、表面硬さ６５０ＨＶ以上９００
ＨＶ以下、０．４mm以上の有効効果深さ（４２０ＨＶ）
とする。That is, in a weight ratio, C: 0.20 to 0.
50%, Si: 0.03 to 0.50%, Mn: 0.30
~ 3.00%, Cr: 0.10-1.00%, Mo:
0.03 to 1.00%, Al: 0.01 to 0.10%,
V: 0.03 to 0.50% by adding to steel, as-rolled, as-forged, in a state of normalizing, etc., for example, subjected to nitrocarburizing treatment at 570 ° C. × 10 hours, Hardness 250 HV or higher, Surface hardness 650 HV or higher 900
Effective depth of HV or less, 0.4mm or more (420HV)
And
【００１４】さらにその後、ショット径０．２〜１．０
mm、ショット硬さ４２〜６２ＨＲＣ、ショット速度５０
〜１２０ｍ／sec の条件にてショットピーニングを施す
ことによって、従来の肌焼鋼と同等以上の疲労強度を得
ることができる。すなわちα＝１．９６、φ８切り欠き
試験片での回転曲げ疲労限が７０ kgf／mm2 （６８６Ｍ
Ｐａ）以上の強度特性を示す。この特性を保ちつつ、な
おかつ素材状態での被削性を向上させるために、さら
に、Ｓ：０．０１５〜０．０７０％、Ｐｂ：０〜０．０
４％に規定してＳとＰｂを添加し、Ｏ：１５ｐｐｍ以下
に酸素レベルを抑制し、しかもＳ、Ｐｂの含有量を、式 1.5S(%)+Pb(%)≧(9/10000) ×目標素材硬さ(HB)-0.22 但し、目標素材硬さ：２４０ＨＢ〜３３０ＨＢ を満足するように、Ｓ、Ｐｂ、酸素の含有量を、式 0.5S(%)+Pb(%)+40酸素(%)≦(8/10000) ×目標芯部硬さ
(HV)-0.11 但し、目標芯部硬さ：２５０ＨＶ〜３５０ＨＶ となるように制御することによって、熱処理歪が小さく
被削性と疲労強度に優れた軟窒化用構造用鋼を得ること
ができる。After that, the shot diameter is 0.2 to 1.0.
mm, shot hardness 42-62 HRC, shot speed 50
By performing shot peening under the condition of 120 m / sec, fatigue strength equal to or higher than that of the conventional case hardening steel can be obtained. That is, α = 1.96, the rotary bending fatigue limit of the φ8 notch test piece was 70 kgf / mm 2 (686M).
It exhibits strength characteristics above Pa). In order to maintain machinability in the raw material state while maintaining this property, S: 0.015 to 0.070%, Pb: 0 to 0.0
S and Pb are added to specify 4%, O: Oxygen level is suppressed to 15ppm or less, and the content of S and Pb is expressed by the formula 1.5S (%) + Pb (%) ≧ (9/10000) × Target material hardness (HB) -0.22 However, the content of S, Pb and oxygen is calculated by the formula 0.5S (%) + Pb (%) + 40 oxygen so as to satisfy the target material hardness: 240HB to 330HB. (%) ≤ (8/10000) x target core hardness
(HV) -0.11 However, by controlling the target core hardness to be 250 HV to 350 HV, it is possible to obtain a structural steel for nitrocarburizing having a small heat treatment strain and excellent machinability and fatigue strength.
【００１５】次いで、本発明の作用について説明する
と、本発明鋼は、圧延まま、鍛造まま、焼きならし等の
状態で軟窒化し、さらにその後、ショットピーニングを
施し圧縮の残留応力を付加することにより、従来の鋼に
軟窒化しただけでは得ることが出来なかった優れた疲労
強度特性を示す。Next, the operation of the present invention will be described. The steel of the present invention is soft-nitrided in the as-rolled, as-forged, or-normalized state, and then shot-peened to add residual stress of compression. Thus, it exhibits excellent fatigue strength characteristics that cannot be obtained only by nitrocarburizing conventional steel.
【００１６】本発明鋼の成分限定理由は、以下の通りで
ある。Ｃは、芯部強度を確保する上で最も重要な元素で
あり、芯部強度の確保のためには、０．２０％以上含有
させる必要がある。しかし、多すぎる場合には、靱性や
加工性を阻害するとともに、軟窒化後の硬化深さを著し
く減少する。０．５０％以下であれば、強度、靱性、加
工性、軟窒化性の点から、満足すべき水準となる。従っ
て、本発明鋼におけるＣ量は、上限を０．５０％とし、
下限を０．２０％とする。また、これらの特性をより充
足するには、０．２５％以上、０．４０％以下とするこ
とがさらに好ましい。The reasons for limiting the components of the steel of the present invention are as follows. C is the most important element for securing the core strength, and it is necessary to contain C by 0.20% or more in order to secure the core strength. However, if the amount is too large, the toughness and workability are impaired, and the hardening depth after soft nitriding is significantly reduced. If it is 0.50% or less, it is a satisfactory level in terms of strength, toughness, workability, and soft nitriding property. Therefore, the upper limit of the amount of C in the steel of the present invention is 0.50%,
The lower limit is 0.20%. Further, in order to satisfy these characteristics, it is more preferable that the content be 0.25% or more and 0.40% or less.
【００１７】Ｓｉは、溶製時の脱酸剤として用いられ、
また、芯部強度あるいは焼戻し軟化抵抗を上げるが、多
すぎる場合には、靱性、加工性を低下させ、特に軟窒化
後の硬化深さを減少させるので、上限を０．５０％とす
る。また、芯部強度確保のために下限を０．０３％とす
る。Si is used as a deoxidizing agent during melting,
Further, although the core strength or the temper softening resistance is increased, if it is too large, the toughness and workability are lowered, and especially the hardening depth after soft nitriding is decreased, so the upper limit is made 0.50%. In addition, the lower limit is made 0.03% to secure the core strength.
【００１８】Ｍｎは、Ｓｉと同様に、溶製時の脱酸剤と
して用いられ、芯部強度を確保する上で有効な元素であ
り、芯部硬さの確保のためには、他元素との関連におい
て０．３０％以上必要であるので下限を０．３０％とす
る。また、軟窒化性に対しては、硬化深さへの影響はほ
とんどないが、表面軟窒化層の硬さを向上させる。しか
し、３．００％を超えると、冷間加工性や被削性を害す
るので、上限を３．００％とする。また、この元素のこ
れらの効果を最も有効とするためには、１．００％以
上、２．００％以下とすることが好ましい。Mn, like Si, is used as a deoxidizing agent during melting and is an effective element for ensuring the strength of the core. In order to secure the hardness of the core, Mn is mixed with other elements. In this connection, 0.30% or more is required, so the lower limit is made 0.30%. Further, the soft nitriding property has almost no effect on the hardening depth, but it improves the hardness of the surface soft nitriding layer. However, if it exceeds 3.00%, cold workability and machinability are impaired, so the upper limit is made 3.00%. Further, in order to maximize these effects of this element, the content is preferably 1.00% or more and 2.00% or less.
【００１９】Ｃｒは、芯部強度を向上させるほか、軟窒
化性に対しては、多いほど軟窒化層の表面硬さを上昇さ
せる。しかし、Ｃｒ量が多くなりすぎた場合、表面に強
固な軟窒化層を形成するために、逆に硬化深さは減少す
る。本発明においては０．１０％未満では、必要とする
表面硬さが得られないために、下限を０．１０％とす
る。一方、１．００％を超えると、硬化硬さが浅くなる
ために、上限を１．００％とする。また、０．２０％以
上、０．６０％以下の領域で、この元素の効果はさらに
明確に現れるので、０．２０％以上、０．６０％以下と
するのが好ましい。In addition to improving the core strength, Cr increases the surface hardness of the soft nitriding layer with respect to the soft nitriding property. However, if the amount of Cr becomes too large, a strong soft nitriding layer is formed on the surface, and conversely the hardening depth decreases. In the present invention, if less than 0.10%, the required surface hardness cannot be obtained, so the lower limit is made 0.10%. On the other hand, if it exceeds 1.00%, the curing hardness becomes shallow, so the upper limit is made 1.00%. Further, the effect of this element becomes more apparent in the region of 0.20% or more and 0.60% or less, so it is preferable to set it to 0.20% or more and 0.60% or less.
【００２０】Ｍｏは、軟窒化層の硬度上昇、靱性の向上
に効果があるほか、窒化処理中、処理後の冷却中に生じ
る脆化を防止する作用を持つ。その効果を期待するには
０．０３％以上必要であり、また、１．００％を超える
とコスト的に不利である上その効果も飽和するため、下
限を０．０３％とし、上限を１．００％とする。さらに
好ましくは、０．０５％以上、０．５０％以下とするこ
とによりこの元素のより明らかな効果が期待できる。Mo has the effect of increasing the hardness and toughness of the soft nitriding layer, and also has the effect of preventing embrittlement that occurs during nitriding and cooling after the treatment. To expect the effect, 0.03% or more is necessary, and if it exceeds 1.00%, there is a cost disadvantage and the effect is saturated, so the lower limit is made 0.03% and the upper limit is made 1 0.00%. More preferably, if it is 0.05% or more and 0.50% or less, a more obvious effect of this element can be expected.
【００２１】Ａｌは、溶製時に強力な脱酸剤として用い
られ、軟窒化性に対してはＣｒと同様に、多いほど軟窒
化後の表面硬さは大きく上昇するため、０．０１％以上
を必要とする。しかし、多くなりすぎると、硬化深さが
著しく減少するようになり、また、熱間加工性や清浄度
なども悪化するので、上限を０．１０％、下限を０．０
１％とする。また、この弊害をさらに抑えるためには、
０．０５％未満添加することが望ましい。Al is used as a strong deoxidizing agent during melting and has a soft nitriding property similar to that of Cr, the surface hardness after soft nitriding increases greatly as it increases, so 0.01% or more. Need. However, if the amount is too large, the curing depth will be remarkably reduced, and the hot workability and cleanliness will be deteriorated, so the upper limit is 0.10% and the lower limit is 0.0.
1%. Moreover, in order to further suppress this adverse effect,
It is desirable to add less than 0.05%.
【００２２】Ｖは、軟窒化性に対して特に有効な元素で
あり、軟窒化層の表面硬さを上昇させ、硬化深さを著し
く増大させる。これは、Ｖが、圧延、鍛造、焼きなら
し、焼きなまし等の硬化熱処理のない状態の時、そのほ
ぼ全量あるいは一部がフェライト中に固溶し、軟窒化処
理によって浸入してきたＣやＮと結合して、微細な炭窒
化物を析出させるためと考えられる。このＶの効果は、
０．０３％未満では不十分であり、０．５０％を超える
と飽和してしまい、また、非常に高価な元素であるため
コスト的にも不利になる。従って、本発明鋼では、Ｖの
上限を０．５０％、下限を０．０３％とする。また、望
ましくは０．３０％以下の添加とすることによって、さ
らにコストを抑えることが可能である。V is an element that is particularly effective for soft nitriding, and increases the surface hardness of the soft nitride layer and significantly increases the hardening depth. This is because when V is in a state where there is no hardening heat treatment such as rolling, forging, normalizing, annealing, etc., almost all or part of it is solid-solved in ferrite, and C and N that have penetrated by soft nitriding treatment. It is considered that this is because they bond to precipitate fine carbonitrides. The effect of this V is
If it is less than 0.03%, it is insufficient, and if it exceeds 0.50%, it is saturated, and it is disadvantageous in terms of cost because it is an extremely expensive element. Therefore, in the steel of the present invention, the upper limit of V is 0.50% and the lower limit is 0.03%. Moreover, it is possible to further suppress the cost by adding 0.30% or less.
【００２３】Ｓは、鋼の被削性を向上させる元素であ
り、素材状態での加工性を確保するためには、０．０１
５％必要であり、また、多すぎると疲労強度を低下さ
せ、特に硫化物系介在物の影響で歯車など部品の疲労強
度に異方性を生じさせる。発明者らは、回転曲げ疲労限
（α＝１．９６、φ８切り欠き試験片使用）７０kgf ／
mm2 （６８６MPa ）以上の特性を保つためには、０．０
７０％添加しても差し支えないことを発見した。そのた
め、Ｓ添加の下限を０．０１５％、上限を０．０７０％
とする。しかし、硫化物系介在物による機械的性質にお
ける異方性を考慮し、上限を０．０４０％とすることが
さらに望ましい。S is an element that improves the machinability of steel, and is 0.01 in order to secure the machinability in the raw material state.
5% is required, and if it is too large, the fatigue strength is reduced, and the fatigue strength of parts such as gears is anisotropy due to the influence of sulfide inclusions. The inventors have found that the fatigue limit of rotary bending (α = 1.96, using φ8 notch test piece) is 70 kgf /
To maintain the characteristics of mm 2 (686 MPa) or more, 0.0
It has been discovered that 70% addition is acceptable. Therefore, the lower limit of S addition is 0.015% and the upper limit is 0.070%.
And However, it is more desirable to set the upper limit to 0.040% in consideration of anisotropy in mechanical properties due to sulfide-based inclusions.
【００２４】Ｐｂは、鋼の被削性を向上させる元素であ
り、特に切り屑処理性の向上に有効である。一方、特開
平２−１４９６１６で提案されたとおり、軟窒化後ショ
ットピーニングを施すことにより、疲労強度が大幅に向
上する。しかしながら発明者らは、軟窒化後ショットピ
ーニングを施し高強度化した場合は、Ｐｂを添加した材
料の疲労強度がＰｂ無添加のそれよりも劣ること、そし
て、Ｐｂを多量に添加すれば目標の疲労特性である回転
曲げ疲労限（α＝１．９６、φ８切り欠き試験片使用）
７０kgf ／mm2 （６８６MPa ）以上を満足できなくなる
ことを見出し、さらに、Ｐｂは酸化物系介在物との複合
作用で疲労強度低下の要因になるという事実を明らかに
した。さらにこの場合、Ｐｂを０．０４０％以内添加
し、同時に酸素量を１５ｐｐｍ以下に抑えることによ
り、上記の高疲労強度特性と良好な被削性を併せ持つこ
とが出来るという知見を得た。またＰｂは、Ｓを多量添
加することなく被削性を向上させるために必要であるた
め、下限はＳ量との兼ね合いから決めるべきものであ
る。そのため、Ｐｂ添加の下限を０、上限を０．０４％
とする。Ｐｂは０．０１０％以上であればより明確にそ
の効果が現れるので、好ましくは下限を０．０１０％と
する。Pb is an element that improves the machinability of steel, and is particularly effective in improving the chip disposability. On the other hand, as proposed in JP-A-2-149616, by performing shot peening after soft nitriding, fatigue strength is significantly improved. However, the inventors have found that when shot peening is performed after soft nitriding to increase the strength, the fatigue strength of the Pb-added material is inferior to that of the Pb-free material, and if a large amount of Pb is added, the target Rotational bending fatigue limit, which is the fatigue characteristic (α = 1.96, φ8 notch test piece used)
It has been found that 70 kgf / mm 2 (686 MPa) or more cannot be satisfied, and it is further clarified that Pb causes fatigue strength to decrease due to its combined action with oxide inclusions. Furthermore, in this case, it was found that by adding Pb within 0.040% and simultaneously suppressing the oxygen content to 15 ppm or less, it is possible to have both the above high fatigue strength characteristics and good machinability. Further, Pb is necessary in order to improve the machinability without adding a large amount of S, so the lower limit should be determined in consideration of the S amount. Therefore, the lower limit of Pb addition is 0 and the upper limit is 0.04%.
And If Pb is 0.010% or more, the effect is more clearly exhibited, so the lower limit is preferably made 0.010%.
【００２５】Ｏは、上記のとおり、Ｐｂを０．０４０％
以下添加し、同時に酸素量を１５ｐｐｍ以下とすること
により、高疲労強度特性と良好な被削性を併せ持つこと
ができる。従ってＯの上限を１５ｐｐｍとする。さら
に、優れた疲労強度特性を得るには、酸素含有量を１２
ｐｐｍ以下に抑えることがより望ましい。As described above, O contains 0.040% of Pb.
By adding below and simultaneously setting the oxygen content to 15 ppm or less, it is possible to have both high fatigue strength characteristics and good machinability. Therefore, the upper limit of O is set to 15 ppm. Furthermore, in order to obtain excellent fatigue strength characteristics, the oxygen content should be 12
It is more desirable to suppress the content to below ppm.
【００２６】Ｓ、Ｐｂは、上記の通り、ともに被削性を
向上させる元素である。また、圧延まま、鍛造まま、焼
きならし後等の特別な硬化熱処理のない素材状態ではフ
ェライト・パーライト、ベイナイト、或いはそれらの混
合組織となり、素材硬さの上昇とともに被削性が低下す
る。Ｓ、Ｐｂ、Ｏは、上記のとおり、疲労強度を低下さ
せる元素である。又、窒化は変態点以下の処理であるた
め、窒化前の素材硬さで窒化後の芯部硬さが決定する。
そして、窒化後の芯部硬さが低下すると、疲労強度も低
下する。これらの兼ね合いから、被削性確保のために
は、Ｓ、Ｐｂのトータル量の下限を、疲労強度確保のた
めには、Ｓ、Ｐｂ、Ｏのトータル量の上限を、それぞ
れ、素材硬さ、芯部硬さとの関係より規定する必要があ
る。As described above, S and Pb are both elements that improve machinability. Further, in a material state without special hardening heat treatment such as as-rolled, as-forged or after normalizing, it becomes ferrite / pearlite, bainite, or a mixed structure thereof, and the machinability decreases as the material hardness increases. As described above, S, Pb, and O are elements that reduce fatigue strength. Further, since nitriding is a treatment below the transformation point, the hardness of the material before nitriding determines the hardness of the core after nitriding.
If the core hardness after nitriding decreases, the fatigue strength also decreases. From these balances, in order to secure machinability, the lower limit of the total amount of S, Pb is set, and in order to secure the fatigue strength, the upper limit of the total amount of S, Pb, O is set. It is necessary to specify it in relation to the core hardness.
【００２７】Ｓ、Ｐｂのトータル量の下限は、それぞれ
単独の成分範囲が上記範囲内で、しかも式 1.5S(%)+Pb(%)≧(9/10000) ×目標素材硬さ(HB)-0.22 但し、目標素材硬さ：２４０ＨＢ〜３３０ＨＢ を満足するように添加しなければならない。なお、目標
素材硬さは強度と被削性のバランスを考慮して上記値に
限定する。The lower limit of the total amount of S and Pb is such that the individual component ranges are within the above range, and the formula 1.5S (%) + Pb (%) ≧ (9/10000) × target material hardness (HB) -0.22 However, it must be added so as to satisfy the target material hardness: 240HB to 330HB. The target material hardness is limited to the above value in consideration of the balance between strength and machinability.
【００２８】また、Ｓ、Ｐｂ、Ｏのトータル量の上限
は、それぞれ単独の成分範囲が上記範囲内で、しかも式 0.5S(%)+Pb(%)+40酸素(%)≦(8/10000) ×目標芯部硬さ
(HV)-0.11 但し、目標芯部硬さ：２５０ＨＶ〜３５０ＨＶ を満足するように添加しなければならない。なお、目標
芯部硬さは、疲労強度と靱性を考慮して上記値に限定す
る。In addition, the upper limit of the total amount of S, Pb, and O is such that the individual component ranges are within the above ranges and the formula 0.5S (%) + Pb (%) + 40 oxygen (%) ≦ (8 / 10000) × target core hardness
(HV) -0.11 However, it must be added so as to satisfy the target core hardness: 250 HV to 350 HV. The target core hardness is limited to the above value in consideration of fatigue strength and toughness.
【００２９】次に、窒化処理方法およびショットピーニ
ング処理方法は以下の通りである。窒化の方法は、鋼の
合金組成を前記のように限定しているため、ガス軟窒
化、タフトライドあるいはイオン軟窒化、または、ガス
窒化、イオン窒化いずれの方法を使用しても良い。例え
ば、５７０℃×１０ｈｒ、処理雰囲気：ＮＨ3 ／ＲＸ＝
１／１でガス軟窒化処理する。ショットピーニング処理
方法は、十分な最大圧縮応力と圧縮残留応力深さを得る
ためと、ショットにより発生したクラックによる疲労強
度低下をおさえるために以下の通りとする。Next, the nitriding treatment method and the shot peening treatment method are as follows. As for the nitriding method, since the alloy composition of steel is limited as described above, any of gas nitrocarburizing, tuftride or ion nitrocarburizing, or gas nitriding or ion nitriding may be used. For example, 570 ° C. × 10 hr, processing atmosphere: NH 3 / RX =
Gas soft nitriding is performed at 1/1. The shot peening method is as follows in order to obtain a sufficient maximum compressive stress and a sufficient compressive residual stress depth and to suppress the fatigue strength reduction due to the crack generated by the shot.
【００３０】ショット径０．２〜１．０mm、ショット硬
さ４２〜６２ＨＲＣ、ショット速度５０〜１２０ｍ／se
c である。Shot diameter 0.2-1.0 mm, shot hardness 42-62 HRC, shot speed 50-120 m / se
c.
【００３１】以上述べたとおり、本発明鋼は芯部強度確
保のためにＣ、Ｍｎ、Ｃｒ、Ｍｏ量を規定し、軟窒化層
の特性を調整するためにＣｒ、Ａｌ、Ｖ、Ｍｏ量を規定
し、素材状態での被削性の向上と、処理後の高疲労強度
の確保を両立させるために、Ｓ、Ｓｂの添加量および酸
素含有量を規定した鋼を、圧延まま、鍛造まま、焼きな
らし等の状態でＡ1 変態点以下の低熱処理歪表面硬化処
理である軟窒化処理の後、圧縮の残留応力を付加するた
めにショットピーニングを施すことによって、小野式回
転曲げ疲労限（α＝１．９６、φ８切り欠き試験片使
用）７０kgf/mm2（６８６MPa ）という高疲労強度特性
を獲得した、軟窒化前の素材状態では高硬さでもドリル
穿孔時間１３sec 以下という肌焼鋼並みかそれ以上の被
削性を持ち、熱処理歪が肌焼鋼の１／３以下となる被削
性と疲労強度に優れた軟窒化構造用鋼である。As described above, in the steel of the present invention, the amounts of C, Mn, Cr and Mo are specified to secure the core strength, and the amounts of Cr, Al, V and Mo are adjusted to adjust the characteristics of the soft nitrided layer. In order to achieve both improvement in machinability in the raw material state and securing of high fatigue strength after treatment, steel with specified S and Sb addition amounts and oxygen content is rolled, forged, After soft nitriding, which is a low heat treatment strain surface hardening treatment at a temperature below the A 1 transformation point in a state such as normalizing, shot peening is applied to add compressive residual stress, and the Ono-type rotary bending fatigue limit ( α = 1.96, φ8 notch test piece used) 70kgf / mm 2 (686MPa) high fatigue strength property acquired, same as case hardening steel with high hardness in the material state before nitrocarburizing and drilling time of 13sec or less. It has machinability of more than that, and heat treatment strains the skin Is an excellent soft-nitriding structural steel in machinability and fatigue strength to be less than 1/3 of the steel.
【００３２】[0032]
【発明の実施の形態】本発明の効果を明らかにするた
め、以下に実施例を示す。BEST MODE FOR CARRYING OUT THE INVENTION In order to clarify the effects of the present invention, examples will be shown below.
【００３３】[0033]
【表１】 [Table 1]
【００３４】表１に示す化学成分の鋼を、小型真空溶解
炉で溶製し、１２００℃で直径２０mmの丸棒に鍛造し、
９００℃焼きならしを施した後、機械加工によって小野
式回転曲げ疲労試験片（α＝１．９６、φ８切り欠き）
を作製し、ガス軟窒化処理の後、ショットピーニングを
施し、試験を行った。ガス軟窒化およりびショットピー
ニングの条件は下記に示す通りである。Steel having the chemical composition shown in Table 1 was melted in a small vacuum melting furnace and was forged into a round bar having a diameter of 20 mm at 1200 ° C.
Ono-type rotary bending fatigue test piece (α = 1.96, φ8 notch) by machining after normalizing at 900 ℃
Was prepared, and after the gas soft nitriding treatment, shot peening was performed and a test was conducted. The conditions for gas soft nitriding and shot peening are as shown below.
【００３５】ガス軟窒化処理条件： 処理温度 ：５７０℃ 処理時間 ：１０ｈ 処理雰囲気 ：ＮＨ3 ／ＲＸ＝１／１Gas soft nitriding processing conditions: processing temperature: 570 ° C. processing time: 10 h processing atmosphere: NH 3 / RX = 1/1
【００３６】ショットピーニング条件： ショット速度：９０m/sec ショット径 ：０．６mm ショット硬さ：５４HRC 照射時間 ：３０secShot peening conditions: Shot speed: 90 m / sec Shot diameter: 0.6 mm Shot hardness: 54 HRC Irradiation time: 30 sec
【００３７】また、試験片加工前の素材状態で被削性を
調査するため、鋼塊を１２００℃で直径６５mmに鍛造
し、ドリル穿孔性試験を行なった。この試験は、材料の
被削性を下記の条件で深さ１０mmのドリル穴を穿孔する
ために要する時間（sec ）（２５個の穴を穿孔するとき
の平均）で評価するものである。 ドリル穿孔試験条件 方式 ：乾式自由落下式 工具 ：ＳＫＨ５１ φ８ストレートドリル 周速 ：２３ｍ／min 荷重 ：６８６ＮFurther, in order to investigate the machinability in the material state before processing the test piece, the steel ingot was forged to a diameter of 65 mm at 1200 ° C., and a drill piercing test was conducted. This test evaluates the machinability of the material by the time (sec) required to drill a 10 mm deep drill hole under the following conditions (average when drilling 25 holes). Drilling test conditions Method: Dry free-fall tool: SKH51 φ8 straight drill Peripheral speed: 23m / min Load: 686N
【００３８】本発明鋼の、素材状態でのドリル穿孔性、
軟窒化特性、芯部強度、および、軟窒化とショットピー
ニングを施すことによって得られる疲労強度は表２に示
すとおりである。The drilling property of the steel of the present invention in the material state,
Table 2 shows soft nitriding characteristics, core strength, and fatigue strength obtained by performing soft nitriding and shot peening.
【００３９】図１に素材状態でのドリル穿孔性試験の結
果を、硬さとドリル穿孔時間で整理したものを示す。こ
の結果より、Ｓ、Ｐｂを添加することによって、高硬さ
でも肌焼鋼並みのレベルを示すことが分かる。FIG. 1 shows the results of the drill piercing test in the raw material state, organized by hardness and drill piercing time. From this result, it can be seen that the addition of S and Pb shows a level comparable to case hardening steel even with high hardness.
【００４０】また、図２、図３にほぼ同一硬さの素材の
ドリル穿孔時間をＳ、Ｐｂ量で整理したものを示す。
Ｓ、Ｐｂはともに被削性に対して有効な作用があること
が分かる。Further, FIGS. 2 and 3 show the drilling times of materials having substantially the same hardness arranged by the amounts of S and Pb.
It can be seen that both S and Pb have an effective effect on machinability.
【００４１】図４に、軟窒化後にショットピーニングを
施した材料の、小野式回転曲げ疲労強度（α＝１．９
６、φ８切り欠き試験片使用）を疲労限（１０7 寿命強
度）と酸素、Ｐｂ量との関係で示す。酸素含有量とＰｂ
添加量をともに抑えるほど、疲労強度は向上する。ま
た、疲労限７０ｋｇｆ／mm2 （６８６MPa ）という高疲
労強度特性を得るには、酸素含有量を１５ppm 以下に抑
え、Ｐｂ添加量を０．０４％以下にする必要があること
が分かる。FIG. 4 shows the Ono-type rotary bending fatigue strength (α = 1.9) of the material subjected to shot peening after nitrocarburizing.
6 and φ8 notch test pieces are shown by the relationship between the fatigue limit (10 7 life strength) and the amounts of oxygen and Pb. Oxygen content and Pb
The fatigue strength is improved as the addition amount is suppressed. Further, it is necessary to suppress the oxygen content to 15 ppm or less and the Pb content to 0.04% or less in order to obtain the high fatigue strength characteristics of the fatigue limit of 70 kgf / mm 2 (686 MPa).
【００４２】[0042]
【表２】 [Table 2]
【００４３】図５に、Ｓ：０．０１５％以上０．０７０
％以下、Ｐｂ：０％以上０．０４０％以下の範囲におけ
るＳ、Ｐｂのトータル量と切削前の素材硬さに対する、
ドリル穿孔時間の関係を示す。ドリル穿孔時間が１３ s
ec以下となるには、 1.5S(%)+Pb(%)≧(9/10000) ×目標素材硬さ(HB)-0.22 とする必要があることが分かる。In FIG. 5, S: 0.015% or more and 0.070
% Or less, Pb: relative to the total amount of S and Pb in the range of 0% to 0.040% and the material hardness before cutting,
The relation of drilling time is shown. Drilling time is 13 s
It can be seen that it is necessary to satisfy 1.5S (%) + Pb (%) ≧ (9/10000) × target material hardness (HB) −0.22 in order to be ec or less.
【００４４】さらに、Ｓ、Ｐｂの影響を明らかにするた
め、図７に、ほぼ同一な窒化特性を持つ試験片の軟窒化
後と、さらにその後ショットピーニングを施した場合の
小野式回転曲げ疲労強度（α＝１．９６、φ８切り欠き
試験片使用）を示す。疲労限とＳ量の関係を座標にと
り、Ｐｂ量によって層別した。Further, in order to clarify the effect of S and Pb, FIG. 7 shows the Ono-type rotary bending fatigue strength after soft nitriding of a test piece having almost the same nitriding characteristics and then after shot peening. (Α = 1.96, using φ8 notch test piece) is shown. The relationship between the fatigue limit and the S content was taken as coordinates and stratified by the Pb content.
【００４５】窒化材にショットを施すことにより、疲労
限は著しく向上することが分かる。Ｐｂの疲労強度への
悪影響は、軟窒化処理のままではほとんど現れず、ショ
ットを施すことにより顕著となる。この時、０．０６％
Ｐｂ添加鋼の破断した試験片のほとんどがフィッシュア
イ起点であり、起点にはＰｂが付着した酸化物系介在物
の存在が認められた。Ｐｂと酸素の複合作用の影響が、
疲労強度低下の原因の一つであることが明らかとなっ
た。It can be seen that the fatigue limit is remarkably improved by subjecting the nitride material to shots. The adverse effect of Pb on the fatigue strength hardly appears when the soft nitriding treatment is performed as it is, and becomes more remarkable when shot. At this time, 0.06%
Most of the fractured test pieces of the Pb-added steel were at the fish eye origin, and the presence of oxide inclusions with Pb adhering to the origin was recognized. The effect of the combined action of Pb and oxygen is
It was clarified that this is one of the causes of the decrease in fatigue strength.
【００４６】また、ＳもＰｂほど明確ではないものの、
疲労強度を低下させる傾向を示すことが分かる。Although S is not so clear as Pb,
It can be seen that the fatigue strength tends to decrease.
【００４７】図６に、Ｓ：０．０１５％以上０．０７０
％以下、Ｐｂ：０％以上０．０４０％以下、酸素量１５
ppm 以下の範囲におけるＳ、Ｐｂ、Ｏのトータル量と窒
化後の芯部硬さに対する、小野式回転曲げ疲労試験での
疲労限の関係を示す。疲労限７０ｋｇｆ／mm2 （６８６
MPa ）となるには、 0.5S(%)+Pb(%)+40酸素(%)≦(8/10000) ×目標芯部硬さ
(HV)-0.11 とする必要があることが分かる。In FIG. 6, S: 0.015% or more and 0.070
% Or less, Pb: 0% or more and 0.040% or less, oxygen amount 15
The relationship between the total amount of S, Pb, and O and the hardness of the core after nitriding in the range of ppm or less and the fatigue limit in the Ono-type rotary bending fatigue test is shown. Fatigue limit 70 kgf / mm 2 (686
MPa), 0.5S (%) + Pb (%) + 40 oxygen (%) ≤ (8/10000) x target core hardness
It turns out that it is necessary to set (HV) -0.11.
【００４８】図８に本発明鋼と従来浸炭材のＵ．Ｓ．Ｎ
ａｂｙ歪試験による熱処理歪の大きさの違いを示す。本
発明鋼の軟窒化後の熱処理歪は、従来浸炭材の１／３以
下と非常に小さいことが分かる。FIG. 8 shows U.V. of the steel of the present invention and the conventional carburized material. S. N
The difference in the magnitude of heat treatment strain by an aby strain test is shown. It can be seen that the heat treatment strain of the steel of the present invention after soft nitriding is as small as 1/3 or less of that of the conventional carburized material.
【００４９】第３表にショットピーニング条件の違いに
よる疲労強度への影響を示す。本発明鋼１を用いて、焼
ならし後、５７０℃×１０時間のガス軟窒化処理を施
し、それぞれの条件でショットピーニングを施した。Table 3 shows the effect of different shot peening conditions on fatigue strength. Using the steel 1 of the present invention, after normalizing, gas soft nitriding treatment was performed at 570 ° C. for 10 hours, and shot peening was performed under each condition.
【００５０】[0050]
【表３】 [Table 3]
【００５１】本発明鋼に適用するショットピーニング条
件ａ〜ｅでは、最大圧縮残留応力が９８０〜１１２７MP
a 、圧縮残留応力深さ０．２５〜０．３０mmとなり、切
欠き回転曲げ疲労限は６９５〜７２０MPa と優れた特性
を示す。Under the shot peening conditions a to e applied to the steel of the present invention, the maximum compressive residual stress is 980 to 1127 MP.
a, the compressive residual stress depth is 0.25 to 0.30 mm, and the notch rotary bending fatigue limit is 695 to 720 MPa, which is excellent characteristics.
【００５２】それに対して適用範囲外のショットピーニ
ング条件ｆ〜ｊでは、ピーニング強度が大きすぎる場合
（ｆ，ｈ，ｊ）、圧縮残留応力深さは深いが、表面の化
合物層に発生したクラックのために回転曲げ疲労強度は
低くなっている。また、ピーニング強度が小さい場合
（ｇ，ｉ）は、圧縮残留応力深さが０．１５mmと浅く、
回転曲げ疲労限も低くなっていることが分かる。On the other hand, under the shot peening conditions f to j out of the applicable range, when the peening strength is too large (f, h, j), the compressive residual stress depth is deep, but cracks generated in the compound layer on the surface are generated. Therefore, the rotational bending fatigue strength is low. When the peening strength is small (g, i), the depth of compressive residual stress is as shallow as 0.15 mm,
It can be seen that the rotational bending fatigue limit is also low.
【００５３】[0053]
【発明の効果】以上説明したように、本発明鋼は、これ
を従来浸炭材の使用されていた部品に使用する際、熱処
理歪を小さくしつつ、優れた疲労強度と良好な部品の加
工性を備えた機械構造部品用軟窒化用鋼として、従来の
軟窒化用構造用鋼では得られなかった優れた部品性能、
低コスト性を実現したものである。As described above, when the steel of the present invention is used for a part which has been conventionally used as a carburized material, it has excellent fatigue strength and good workability of the part while reducing heat treatment strain. As soft nitriding steel for machine structural parts equipped with, excellent part performance not obtained with conventional soft nitriding structural steel,
It realizes low cost.
【図１】素材状態でのドリル穿孔試験の結果を示す図で
ある。FIG. 1 is a diagram showing the results of a drilling test in a raw material state.
【図２】同一硬さの素材のドリル穿孔時間をＳ量で整理
した図である。FIG. 2 is a diagram in which drilling times of materials having the same hardness are arranged by S amount.
【図３】同一硬さの素材のドリル穿孔時間をＰｂ量で整
理した図である。FIG. 3 is a diagram in which drilling times of materials having the same hardness are arranged by Pb amount.
【図４】軟窒化後にショットピーニングした供試材の回
転曲げ疲労強度と酸素及びＰｂ添加量の関係を示す図で
ある。FIG. 4 is a diagram showing a relationship between rotary bending fatigue strength and oxygen and Pb addition amounts of a test material shot-peened after nitrocarburizing.
【図５】Ｓ、Ｐｂのトータル量と切削前の目標素材硬さ
に対するドリル穿孔時間の関係を示す図である。FIG. 5 is a diagram showing a relationship between a total amount of S and Pb and a target material hardness before cutting with respect to a drilling time.
【図６】Ｓ、ＰｂとＯのトータル量と窒化後の目標芯部
硬さに対する小野式回転曲げ疲労試験での疲労限の関係
を示す図である。FIG. 6 is a diagram showing a relationship between a total amount of S, Pb and O and a target core hardness after nitriding with respect to a fatigue limit in an Ono-type rotary bending fatigue test.
【図７】軟窒化後にショットピーニングした供試材の回
転曲げ疲労強度とＰｂおよびＳ添加量の関係を示す図で
ある。FIG. 7 is a diagram showing the relationship between the rotational bending fatigue strength and the Pb and S addition amounts of the test material that was shot peened after soft nitriding.
【図８】本発明鋼と従来浸炭材の熱処理歪の違いを示す
図である。FIG. 8 is a diagram showing a difference in heat treatment strain between the steel of the present invention and a conventional carburized material.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２３Ｃ 8/26 Ｃ２３Ｃ 8/26 8/80 8/80 (72)発明者 細田 賢一 兵庫県姫路市飾磨区中島字一文字3007番地 山陽特殊製鋼株式会社内 (72)発明者 有見 幸夫 広島県安芸郡府中町新地３番１号 マツダ 株式会社内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification number Reference number within the agency FI Technical display location C23C 8/26 C23C 8/26 8/80 8/80 (72) Inventor Kenichi Hosoda Himeji City, Hyogo Prefecture 3007 Nakajima, Nakajima, Shikama-ku, Sanyo Special Steel Co., Ltd. (72) Inventor Yukio Arimi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Corporation
Claims (1)
Ｓｉ：０．０３〜０．５０％、Ｍｎ：０．３０〜３．０
０％、Ｃｒ：０．１０〜１．００％、Ｍｏ：０．０３〜
１．００％、Ａｌ：０．０１〜０．１０％、Ｖ：０．０
３〜０．５０％、Ｓ：０．０１５〜０．０７０％、Ｐ
ｂ：０〜０．０４０％、Ｏ：１５ｐｐｍ以下を含有する
と共に、Ｓ、Ｐｂの含有量が、式 1.5S(%)+Pb(%)≧(9/10000) ×目標素材硬さ(HB)-0.22 但し、目標素材硬さ：２４０ＨＢ〜３３０ＨＢ を満足し、なおかつＳ、Ｐｂ、酸素の含有量が、式 0.5S(%)+Pb(%)+40酸素(%)≦(8/10000) ×目標芯部硬さ
(HV)-0.11 但し、目標芯部硬さ：２５０ＨＶ〜３５０ＨＶ を満足し、残部がＦｅおよび不可避不純物よりなり、圧
延まま、鍛造まま、焼きならし等の状態で機械加工を施
した後、軟窒化処理とショットピーニングを施して使用
するための、疲労強度と被削性に優れた軟窒化用構造用
鋼。1. A weight ratio of C: 0.20 to 0.50%,
Si: 0.03 to 0.50%, Mn: 0.30 to 3.0
0%, Cr: 0.10 to 1.00%, Mo: 0.03 to
1.00%, Al: 0.01 to 0.10%, V: 0.0
3 to 0.50%, S: 0.015 to 0.070%, P
b: 0 to 0.040%, O: 15 ppm or less, and the content of S and Pb is expressed by the formula 1.5S (%) + Pb (%) ≧ (9/10000) × target material hardness (HB ) -0.22 However, the target material hardness: 240HB to 330HB is satisfied, and the contents of S, Pb and oxygen are calculated by the formula 0.5S (%) + Pb (%) + 40 oxygen (%) ≦ (8/10000 ) × Target core hardness
(HV) -0.11 However, the target core hardness: 250HV to 350HV is satisfied, the balance consists of Fe and unavoidable impurities, and it is softened after being machined in the as-rolled, as-forged, or-normalized state. Structural steel for soft nitriding with excellent fatigue strength and machinability for nitriding and shot peening.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05411496A JP3340016B2 (en) | 1996-02-17 | 1996-02-17 | Structural steel for soft nitriding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05411496A JP3340016B2 (en) | 1996-02-17 | 1996-02-17 | Structural steel for soft nitriding |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09227992A true JPH09227992A (en) | 1997-09-02 |
| JP3340016B2 JP3340016B2 (en) | 2002-10-28 |
Family
ID=12961577
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP05411496A Expired - Fee Related JP3340016B2 (en) | 1996-02-17 | 1996-02-17 | Structural steel for soft nitriding |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3340016B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003253422A (en) * | 2002-03-04 | 2003-09-10 | Sanyo Special Steel Co Ltd | Method for prolonging service life of tool such as mandrel and forming die, and tool of prolonged service life such as mandrel and forming die |
| JP2006291310A (en) * | 2005-04-12 | 2006-10-26 | Daido Steel Co Ltd | Crankshaft and producing method therefor |
| JP2007332421A (en) * | 2006-06-15 | 2007-12-27 | Sumitomo Metal Ind Ltd | Method of manufacturing soft-nitride part |
| JP2011236452A (en) * | 2010-05-07 | 2011-11-24 | Daido Steel Co Ltd | Bainite steel |
| JP2015143169A (en) * | 2013-12-25 | 2015-08-06 | 日立造船株式会社 | Carbon nano-tube creation substrate, production method thereof, and reuse method thereof |
-
1996
- 1996-02-17 JP JP05411496A patent/JP3340016B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003253422A (en) * | 2002-03-04 | 2003-09-10 | Sanyo Special Steel Co Ltd | Method for prolonging service life of tool such as mandrel and forming die, and tool of prolonged service life such as mandrel and forming die |
| JP2006291310A (en) * | 2005-04-12 | 2006-10-26 | Daido Steel Co Ltd | Crankshaft and producing method therefor |
| JP2007332421A (en) * | 2006-06-15 | 2007-12-27 | Sumitomo Metal Ind Ltd | Method of manufacturing soft-nitride part |
| JP2011236452A (en) * | 2010-05-07 | 2011-11-24 | Daido Steel Co Ltd | Bainite steel |
| JP2015143169A (en) * | 2013-12-25 | 2015-08-06 | 日立造船株式会社 | Carbon nano-tube creation substrate, production method thereof, and reuse method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3340016B2 (en) | 2002-10-28 |
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