JPH0633189A - Spring steel with excellent delayed fracture resistance - Google Patents
Spring steel with excellent delayed fracture resistanceInfo
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- JPH0633189A JPH0633189A JP18662692A JP18662692A JPH0633189A JP H0633189 A JPH0633189 A JP H0633189A JP 18662692 A JP18662692 A JP 18662692A JP 18662692 A JP18662692 A JP 18662692A JP H0633189 A JPH0633189 A JP H0633189A
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Abstract
(57)【要約】
【目的】耐遅れ破壊性に優れ、かつ 110kgf/mm2 以上の
引張強さを有するばね用鋼の提供。
【構成】重量％で、Ｃ：0.50％を超え0.90％以下、Si：
0.05〜0.50％、Mn：0.5％未満、Cu：0.10〜1.00％、C
r：0.10〜5.00％、Mo：0.05〜1.00％、Al：0.01〜0.10
％を含有し、かつCu＋Mo≧ 0.4％を満たし、残部はFeお
よび不純物（Ｐ： 0.015％未満、Ｓ：0.01％未満）から
なり、焼入れ焼き戻し組織を有する鋼。成分元素とし
て、更にNi（0.05〜0.50重量％）、および／またはNb
（0.01〜0.10重量％）、Ti（0.01〜0.10重量％）、Ｖ
（0.01〜0.10重量％）の１種以上を含有させてもよく、
それらの鋼にさらにＢ（0.0002〜 0.002重量％）を含有
させてもよい。
【効果】耐遅れ破壊性に優れた安価な低合金高強度鋼と
して、特に、自動車の板ばねやコイルばね等の素材とし
て好適である。(57) [Summary] [Purpose] To provide spring steel with excellent delayed fracture resistance and tensile strength of 110 kgf / mm 2 or more. [Composition] C: 0.50% to 0.90% by weight, Si:
0.05 to 0.50%, Mn: less than 0.5%, Cu: 0.10 to 1.00%, C
r: 0.10-5.00%, Mo: 0.05-1.00%, Al: 0.01-0.10
%, Cu + Mo ≧ 0.4%, the balance Fe and impurities (P: less than 0.015%, S: less than 0.01%), and a quenched and tempered structure. Ni (0.05 to 0.50% by weight) and / or Nb as a constituent element
(0.01 to 0.10% by weight), Ti (0.01 to 0.10% by weight), V
(0.01 to 0.10% by weight) may be contained.
The steels may further contain B (0.0002 to 0.002% by weight). [Effect] It is suitable as an inexpensive low-alloy high-strength steel excellent in delayed fracture resistance, particularly as a material for leaf springs and coil springs of automobiles.
Description
【０００１】[0001]
【産業上の利用分野】本発明は 110kg/mm2以上の引張強
さを有し、かつ耐遅れ破壊性に優れた板ばね、コイルば
ね等に用いられるばね用鋼に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spring steel used for leaf springs, coil springs, etc. having a tensile strength of 110 kg / mm 2 or more and excellent delayed fracture resistance.
【０００２】[0002]
【従来の技術】近年、特に自動車やトラックなどの軽量
化に伴い今まで以上に高強度の自動車部品用鋼、特に板
ばねやコイルばね等に用いられるばね用鋼の開発が必要
とされてきている。2. Description of the Related Art In recent years, with the reduction in weight of automobiles and trucks in particular, it has become necessary to develop steel for automobile parts having higher strength than ever, especially for springs used for leaf springs and coil springs. There is.
【０００３】従来、一般の高強度ばね用鋼は、例えば、
JIS G 4801(1977)に規定された 0.5％Ｃ−0.95％Cr−0.
20％Ｖの組成を有する SUP10などの低合金鋼の熱間圧延
材に焼入れ焼戻し処理を施すことによって製造されてい
る。Conventionally, general high-strength spring steels are, for example,
0.5% C-0.95% Cr-0 specified in JIS G 4801 (1977).
It is manufactured by subjecting a hot rolled material of a low alloy steel such as SUP10 having a composition of 20% V to quench hardening and tempering.
【０００４】しかし、これらのばね用鋼を自動車部品の
素材として用いた場合、使用中に遅れ破壊を生じること
があり、品質の安定性に欠けるという問題があった。そ
のため、この用途に用いられるばね用鋼は、強度レベル
が引張強さで 110kgf/mm2 以下のものに制限されてい
る。なお、遅れ破壊とは、鋼が限界強度以内の静荷重下
においてある時間経過後に突然脆性的に破断する現象で
あり、外部環境から鋼中に侵入した水素による一種の水
素脆性とされている。However, when these spring steels are used as materials for automobile parts, there is a problem that delayed fracture may occur during use, resulting in lack of stability of quality. Therefore, the spring steel used for this purpose is limited to a strength level of 110 kgf / mm 2 or less in tensile strength. The delayed fracture is a phenomenon in which the steel suddenly breaks brittle after a certain time under a static load within the limit strength, and is a kind of hydrogen embrittlement due to hydrogen invading the steel from the external environment.
【０００５】一方、上記の SUP10などの低合金鋼より耐
遅れ破壊性の優れた鋼として、例えば、 0.1％Ｃ−13％
Cr−0.6 ％Moの組成を有する13Cr系ステンレス鋼が実用
されている。この鋼は引張強さが 140kgf/mm2 程度のも
のまで遅れ破壊の発生のおそれなく使用できるが、高価
であるため限られた用途にしか用いられておらず、自動
車部品用の素材としては未だ一般的に使用されるには至
っていない。On the other hand, as a steel having a delayed fracture resistance superior to the above low alloy steel such as SUP10, for example, 0.1% C-13%
13Cr-based stainless steel having a composition of Cr-0.6% Mo is in practical use. This steel can be used up to a tensile strength of about 140 kgf / mm 2 without fear of delayed fracture, but it is expensive and is used only for a limited number of applications, so it is still a material for automobile parts. It has not been used commonly.
【０００６】上記のばね用鋼の他に、例えば特開昭57−
169062号、特開昭57−171648号、特開昭61− 60832号お
よび特開昭63−227748号等の各公報に、種々の化学組成
を有し、高強度で、かつ耐遅れ破壊性に優れたばね用鋼
と、その製造方法が開示されている。しかしながら、こ
れらの鋼は、品質における安定性は必ずしも高いとは言
えず、自動車用鋼として取り替えの必要なしに使用でき
るような優れた耐遅れ破壊性を有してはいない。In addition to the above spring steel, for example, Japanese Patent Laid-Open No. 57-
169062, JP-A-57-171648, JP-A-61-60832, JP-A-63-227748, etc., have various chemical compositions, high strength, and delayed fracture resistance. Excellent spring steels and methods of making the same are disclosed. However, these steels do not necessarily have high stability in quality and do not have excellent delayed fracture resistance that can be used as automobile steels without the need for replacement.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、耐遅れ破壊
性に優れたばね用鋼であって、恒久的に使用するのでは
なく、取り替えを前提とするが、所定の期間中、遅れ破
壊の発生のおそれがなく、しかも 110kgf/mm2 以上の引
張強さを有するばね用鋼を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention is a spring steel excellent in delayed fracture resistance, and is intended to be replaced, not permanently used, but to prevent delayed fracture during a predetermined period. It is an object of the present invention to provide a spring steel which has no possibility of occurrence and has a tensile strength of 110 kgf / mm 2 or more.
【０００８】[0008]
【課題を解決するための手段】本発明者らは、上記の目
的を達成するために研究を重ねた結果、下記の知見を得
た。すなわち、 (1) Ｃ含有量を低くし、Cuを添加した耐遅れ破壊性に優
れた構造用鋼が既に開発されているが、このCu添加の効
果は、鋼の腐食速度を低下させることによって水素の鋼
中への侵入を抑制し、遅れ破壊の原因である水素脆化を
防止することによるものである。Means for Solving the Problems The present inventors have obtained the following findings as a result of repeated studies for achieving the above-mentioned object. That is, (1) a structural steel with a low C content and excellent Cu resistance to delayed fracture has already been developed, but the effect of Cu addition is that the corrosion rate of the steel decreases. This is because hydrogen is prevented from entering the steel and hydrogen embrittlement, which causes delayed fracture, is prevented.
【０００９】(2) 鋼を更に高強度とするためにＣの含有
量を高めると、Cuの添加だけでは水素の鋼中への侵入を
抑制する効果、すなわち水素透過量を下げる効果が十分
ではない。しかし、更にMoを添加すると水素侵入抑制効
果は著しく向上する。Moの水素侵入抑制効果は鋼の水素
過電圧を低下させることによるもので、鋼中への水素の
侵入に対する抑制機構の異なるCuとMoを複合添加するこ
とにより、耐遅れ破壊性は飛躍的に向上する。(2) If the content of C is increased in order to further increase the strength of the steel, the effect of suppressing the penetration of hydrogen into the steel, that is, the effect of lowering the hydrogen permeation amount, is not sufficient only by adding Cu. Absent. However, when Mo is further added, the effect of suppressing hydrogen penetration is significantly improved. The effect of Mo to suppress hydrogen penetration is due to the reduction of hydrogen overvoltage in steel. By adding Cu and Mo that have different suppression mechanisms for hydrogen penetration into steel, delayed fracture resistance is dramatically improved. To do.
【００１０】本発明は上記の知見に基づいてなされたも
ので、その要旨は、下記〜の耐遅れ破壊性に優れた
ばね用鋼にある。なお、これまでに低Ｐ、低Ｓ化による
Ｐ、Ｓの粒界偏析の軽減および清浄化と、低Mn化が耐遅
れ破壊性の改善に有効であることが見出され、本出願人
により開示されているが（特開平３−243744号公報）、
本発明鋼においても、低Ｓ、低MnとすることによりMnＳ
の析出を低減させ、耐遅れ破壊性の向上を図った。粒界
偏析の軽減および清浄化によって局部腐食が抑制され、
水素の発生が抑えられて鋼表面における固溶水素濃度が
低下し、鋼中への水素透過量が減少する。The present invention has been made on the basis of the above findings, and the gist thereof is the following steels for springs having excellent delayed fracture resistance. It has been found that reduction of P and S grain boundary segregation and cleaning by lowering P and S and reduction of Mn are effective for improving delayed fracture resistance. Although disclosed (JP-A-3-243744),
Even in the steel of the present invention, MnS can be obtained by using low S and low Mn.
The precipitation was reduced and the delayed fracture resistance was improved. Local corrosion is suppressed by reducing grain boundary segregation and cleaning,
Generation of hydrogen is suppressed, the concentration of solid solution hydrogen on the steel surface is reduced, and the amount of hydrogen permeation into the steel is reduced.
【００１１】 重量％で、Ｃ：0.50％を超え0.90％以
下、Si：0.05〜0.50％、Mn： 0.5％未満、Cu：0.10〜1.
00％、Cr：0.10〜5.00％、Mo：0.05〜1.00％、Al：0.01
〜0.10％を含有し、かつCu＋Mo≧ 0.4％を満たし、残部
はFeおよび不可避不純物からなり、不純物中のＰが 0.0
15％未満、Ｓが0.01％未満であって、焼入れ焼き戻し組
織を有することを特徴とする耐遅れ破壊性に優れたばね
用鋼。In weight%, C: more than 0.50% and 0.90% or less, Si: 0.05 to 0.50%, Mn: less than 0.5%, Cu: 0.10 to 1.
00%, Cr: 0.10 to 5.00%, Mo: 0.05 to 1.00%, Al: 0.01
Content of 0.10% and Cu + Mo ≧ 0.4%, the balance consisting of Fe and unavoidable impurities, and P in the impurities is 0.0
A spring steel excellent in delayed fracture resistance, characterized by having a quenching and tempering structure with less than 15% and S less than 0.01%.
【００１２】 前記の成分に加えて、更にNi：0.05
〜0.50重量％（以下、「％」は「重量％」を意味する）
を含有する耐遅れ破壊性に優れたばね用鋼。In addition to the above components, Ni: 0.05
~ 0.50% by weight (hereinafter "%" means "% by weight")
Steel for springs with excellent resistance to delayed fracture.
【００１３】 前記またはの成分に加えて、更に
Nb：0.01〜0.10％、Ti：0.01〜0.10％およびＶ：0.01〜
0.10％の中の１種以上を含有する耐遅れ破壊性に優れた
ばね用鋼。In addition to the above components or
Nb: 0.01 to 0.10%, Ti: 0.01 to 0.10% and V: 0.01 to
Spring steel with excellent delayed fracture resistance containing one or more of 0.10%.
【００１４】 前記、またはの成分に加えて、
更にＢ：0.0002〜 0.002％を含有する耐遅れ破壊性に優
れたばね用鋼。In addition to the above or or
Furthermore, spring steel containing B: 0.0002 to 0.002% and excellent in delayed fracture resistance.
【００１５】[0015]
【作用】以下に、本発明鋼の化学組成および組織を上記
のように定めた理由を説明する。The function of the chemical composition and structure of the steel of the present invention will be described below.
【００１６】（Ａ）化学組成 Ｃ：Ｃは鋼の焼入性を向上させ、強度を増加させるとと
もに、組織を細粒化する作用を有する成分である。しか
し、その含有量が0.50％以下では焼入性が劣化し、必要
とする強度を得ることができない。一方、0.90％を超え
て含有させると焼入れ時の焼割れ感受性が増大し、ま
た、鋼が著しく硬化して靱性が劣化する。従って、Ｃの
含有量は0.50％を超え0.90％以下と定めた。(A) Chemical composition C: C is a component which has the action of improving the hardenability of steel and increasing the strength, and also of refining the structure. However, if the content is 0.50% or less, the hardenability deteriorates and the required strength cannot be obtained. On the other hand, if the content exceeds 0.90%, the susceptibility to quench cracking during quenching increases, and the steel remarkably hardens to deteriorate the toughness. Therefore, the content of C is determined to be more than 0.50% and 0.90% or less.
【００１７】Si：Siは脱酸剤として添加される。また、
鋼の強度を増加させるのに有効な元素である。しかし、
その含有量が0.05％未満では前記の効果は十分ではな
く、一方、0.50％を超えると偏析して靱性が劣化する場
合がある。従って、Siの含有量は0.05〜0.50％と定め
た。Si: Si is added as a deoxidizer. Also,
It is an effective element for increasing the strength of steel. But,
If the content is less than 0.05%, the above effect is not sufficient, while if it exceeds 0.50%, segregation occurs and the toughness may deteriorate. Therefore, the content of Si is set to 0.05 to 0.50%.
【００１８】Mn：Mnは脱酸作用を有するとともに、焼入
性の向上にも有効な元素である。しかし、多量に含有さ
せると粒界脆化現象が生じ、遅れ破壊が発生しやすくな
る。更に、MnはＳと結合してMnＳを生成し、これが割れ
の起点となる。従って、耐遅れ破壊性を改善するために
はその含有量を極力低下させなければならない。よっ
て、Mnの含有量は 0.5％未満とした。Mn: Mn is an element that has a deoxidizing effect and is effective for improving hardenability. However, if contained in a large amount, a grain boundary embrittlement phenomenon occurs and delayed fracture easily occurs. Furthermore, Mn combines with S to generate MnS, which is the starting point of cracking. Therefore, in order to improve delayed fracture resistance, its content must be reduced as much as possible. Therefore, the Mn content is set to less than 0.5%.
【００１９】Cu：Cuは前記のように鋼の腐食速度を低下
させることによって水素の鋼中への侵入を抑制し、遅れ
破壊の原因である水素脆化を防止する。また、Nb、Moお
よびCrと複合添加することによって鋼の焼戻し軟化抵抗
を著しく増大させることができるので、焼戻し温度を高
めることができ、耐遅れ破壊性を向上させる。しかし、
Cuの含有量が0.10％未満ではその効果が小さく、一方、
1.00％を超えて含有させると熱間加工性および靱性が劣
化する。従って、Cuの含有量は0.10〜1.00％の範囲が適
当である。Cu: Cu suppresses the penetration of hydrogen into the steel by lowering the corrosion rate of steel as described above, and prevents hydrogen embrittlement which is a cause of delayed fracture. Further, since the temper softening resistance of steel can be remarkably increased by adding Nb, Mo and Cr in combination, the tempering temperature can be increased and the delayed fracture resistance is improved. But,
If the Cu content is less than 0.10%, its effect is small, while
If the content exceeds 1.00%, hot workability and toughness deteriorate. Therefore, the Cu content is appropriately in the range of 0.10 to 1.00%.
【００２０】Cr：Crは鋼の焼入性を向上させ、かつ鋼の
焼戻し軟化抵抗を高める作用を有する。Cr: Cr has the effects of improving the hardenability of steel and increasing the resistance to temper softening of steel.
【００２１】特に、Mo、Nb、Cuとの複合添加により鋼の
焼戻し軟化抵抗は著しく増大する。しかし、その含有量
が0.10％未満では前記の効果は十分ではなく、また、Cr
は高価な合金元素であるため経済性を考慮し、その含有
量を0.10〜5.00％と定めた。In particular, the combined addition of Mo, Nb and Cu significantly increases the temper softening resistance of steel. However, if the content is less than 0.10%, the above effect is not sufficient, and Cr
Since is an expensive alloying element, its content was set to 0.10-5.00% in consideration of economy.
【００２２】Mo：Moは前記のように水素の鋼中への侵入
を抑制する。また、鋼の焼入性を向上させ、かつ焼戻し
軟化抵抗を高める作用を有し、特にCu、Nb、Crとの複合
添加によって焼戻し軟化抵抗は著しく増大するので、高
い焼戻し温度の設定が可能となり、耐遅れ破壊性を向上
させる。しかし、その含有量が0.05％未満では前記の効
果は十分ではなく、一方1.00％を超えて添加してもその
効果は飽和し、経済的にも不利である。従って、Moの含
有量は0.05〜1.00％と定めた。Mo: Mo suppresses the penetration of hydrogen into the steel as described above. In addition, it has the effects of improving the hardenability of steel and increasing the temper softening resistance, and since the temper softening resistance is remarkably increased by the combined addition of Cu, Nb and Cr, it is possible to set a high tempering temperature. , Improves delayed fracture resistance. However, if the content is less than 0.05%, the above effect is not sufficient, while if added over 1.00%, the effect is saturated and it is economically disadvantageous. Therefore, the content of Mo is set to 0.05 to 1.00%.
【００２３】Al：Alは脱酸作用を有し、また組織の細粒
化を図る上で有効であるが、0.01％未満ではその効果は
十分ではない。一方、0.10％を超えて含有させてもその
効果は飽和し、また介在物の増大により疵が発生しやす
く、靱性も劣化する。従って、Alの含有量は0.01〜0.10
％と定めた。Al: Al has a deoxidizing effect and is effective in achieving fine grain structure, but if it is less than 0.01%, the effect is not sufficient. On the other hand, even if the content exceeds 0.10%, the effect is saturated, and the increase of inclusions easily causes flaws and deteriorates the toughness. Therefore, the content of Al is 0.01-0.10
Defined as%.
【００２４】Cu＋Mo：CuとMoとを複合添加することは、
本発明鋼における重要な要件である。Cu + Mo: The combined addition of Cu and Mo is
This is an important requirement for the steel of the present invention.
【００２５】図１は、0.70％Ｃ−0.30％Si−0.35％Mn−
2.00％Cr−0.05％Alの組成の鋼をベースとし、（Cu＋M
o）含有量を変えた鋼について、（Cu＋Mo）含有量と水
素透過係数（μＣ/cm ）の関係を示した図である。水素
透過係数が小さい方が鋼中への水素侵入量が少ない。こ
の図１から明らかなように、（Cu＋Mo）含有量が 0.4％
未満では鋼中への水素の侵入に対する抑制効果は十分で
はないが、 0.4％以上になると水素侵入量が急激に低下
する。つまり、鋼中への水素の侵入に対する抑制作用の
機構はそれぞれ異なるが、これらの合金元素を組合わ
せ、複合添加することによって、図２および図３に示す
ように、それぞれ単独に添加する場合に比べ、その効果
を相乗的に高めることができる。従って、（Cu＋Mo）含
有量を 0.4％以上とした。なお、図２と図３は、上記の
基本組成の鋼を用いてCuとMoをそれぞれ単独添加した試
料についての試験結果である。FIG. 1 shows 0.70% C-0.30% Si-0.35% Mn-
Based on steel with a composition of 2.00% Cr-0.05% Al, (Cu + M
FIG. 5 is a diagram showing the relationship between the (Cu + Mo) content and the hydrogen permeation coefficient (μC / cm 2) for steels with different contents. The smaller the hydrogen permeability coefficient, the smaller the amount of hydrogen penetration into the steel. As is clear from Fig. 1, the content of (Cu + Mo) is 0.4%.
If it is less than 0.4%, the effect of suppressing the penetration of hydrogen into the steel is not sufficient, but if it exceeds 0.4%, the amount of hydrogen penetration sharply decreases. That is, although the mechanism of suppressing action on the penetration of hydrogen into the steel is different from each other, when these alloy elements are combined and added in combination, as shown in FIG. 2 and FIG. In comparison, the effect can be enhanced synergistically. Therefore, the (Cu + Mo) content is set to 0.4% or more. 2 and 3 are the test results of the samples in which Cu and Mo were individually added using the steel having the above basic composition.
【００２６】本発明鋼（前記の鋼）は、前述の成分の
ほか、残部はFeと不可避的不純物からなる鋼である。不
純物として代表的なものはＰ、Ｓである。The steel of the present invention (the above-mentioned steel) is a steel containing the above components, and the balance being Fe and inevitable impurities. Typical impurities are P and S.
【００２７】Ｐはどのような熱処理を施してもその粒界
偏析を完全に消滅させることはできず、粒界強度を低下
させ、耐遅れ破壊性を劣化させる。従って、その含有量
は低いほど望ましく、 0.015％未満とする。P cannot completely eliminate the grain boundary segregation by any heat treatment, which lowers the grain boundary strength and deteriorates the delayed fracture resistance. Therefore, the lower the content, the better, and the content is less than 0.015%.
【００２８】Ｓは前述のようにMnと結合してMnＳを生成
し、割れの起点となる。また、単独でも粒界に偏析して
脆化を促進させるので、その含有量はＰと同様極力低く
することが必要であり、0.01％未満とする。As described above, S combines with Mn to generate MnS, which becomes the starting point of cracking. In addition, since it segregates to the grain boundaries and promotes embrittlement alone, its content needs to be as low as possible like P, and is less than 0.01%.
【００２９】上記の各成分のほかに、必要に応じて、Ni
を添加してもよく（前記の鋼）、あるいは、の鋼も
しくはの鋼にNb、TiおよびＶの中の１種以上を添加し
てもよく（の鋼）、あるいはまた、の鋼、の鋼も
しくはの鋼にＢを添加してもよい（の鋼）。なお、
不純物のＰ、Ｓについては、の鋼の場合と同様、それ
ぞれ 0.015％未満、0.01％未満とする。必要に応じて添
加する成分の限定理由は以下のとおりである。In addition to the above components, if necessary, Ni
Steel (the above steel), or one or more of Nb, Ti and V (the steel), or the steel of Alternatively, B may be added to the steel (the steel). In addition,
The impurities P and S are less than 0.015% and less than 0.01%, respectively, as in the case of steel. The reasons for limiting the components added as necessary are as follows.
【００３０】Ni：Niは鋼の靱性を高める作用を有すると
共に、Cuの添加による熱間加工性の低下を改善する効果
がある。しかし、その含有量が0.05％未満では十分な効
果が得られず、また、必要以上に添加することは経済的
にも不利であるので、その含有量を0.05〜 0.5％とし
た。Ni: Ni has the effect of increasing the toughness of steel and has the effect of improving the deterioration of hot workability due to the addition of Cu. However, if the content is less than 0.05%, a sufficient effect cannot be obtained, and it is economically disadvantageous to add more than necessary, so the content was made 0.05 to 0.5%.
【００３１】Nb、TiおよびＶ：Nb、TiおよびＶの１種以
上を添加することにより、組織の細粒化が促進され、耐
遅れ破壊性を一段と向上させることができる。しかし、
Nb、TiおよびＶのいずれについても、0.01％未満ではそ
の効果は十分ではなく、また高価な合金元素であるため
経済性を考慮して、これらの元素の含有量は、いずれも
0.01〜 0.1％とした。Nb, Ti and V: Addition of one or more of Nb, Ti and V promotes grain refinement of the structure and further improves delayed fracture resistance. But,
For any of Nb, Ti, and V, if less than 0.01%, the effect is not sufficient, and since they are expensive alloy elements, considering the economic efficiency, the content of each of these elements is
It was set to 0.01 to 0.1%.
【００３２】Ｂ：Ｂは鋼の焼入性を向上させて強度を高
め、かつ粒界を強化して耐遅れ破壊性を向上させる作用
を有している。しかし、0.0002％未満では十分な効果が
得られず、また 0.002％を超えて含有させると鋼の靱性
および耐遅れ破壊性の劣化につながる。従って、Ｂの含
有量は0.0002〜 0.002％とした。B: B has the effect of improving the hardenability of steel to increase its strength, and strengthening the grain boundaries to improve delayed fracture resistance. However, if it is less than 0.0002%, a sufficient effect cannot be obtained, and if it exceeds 0.002%, the toughness and delayed fracture resistance of the steel are deteriorated. Therefore, the content of B is set to 0.0002 to 0.002%.
【００３３】（Ｂ）組織 上記の化学組成を有する鋼であっても、 110kg/mm2以上
の引張強さと良好な耐遅れ破壊性とを具備させるには、
焼入れ焼戻し組織とすることが必要である。これは、焼
ならし材、焼戻し材、焼ならし焼戻し材、圧延のまま材
等が有する高温ベイナイト、フェライト、パーライトを
主とする組織では、安定して 110kg/mm2以上の引張強さ
を有する高強度材を得ることは難しく、一方、焼入れま
まの鋼は引張強さは高いが、降伏点が低く、ばね用鋼と
して使用すると、使用中に応力緩和が生じるからであ
る。また、焼入れままの組織では、耐遅れ破壊性、靱
性、加工性などが良好でないという問題がある。(B) Microstructure Even in the case of steel having the above chemical composition, in order to have tensile strength of 110 kg / mm 2 or more and good delayed fracture resistance,
It is necessary to have a quenched and tempered structure. This is because the normal tempered material, tempered material, tempered tempered material, as-rolled material and other high temperature bainite, ferrite, and pearlite have a stable tensile strength of 110 kg / mm 2 or more. This is because it is difficult to obtain the high-strength material it has, while on the other hand, the as-quenched steel has a high tensile strength but a low yield point, and when used as spring steel, stress relaxation occurs during use. Further, the as-quenched structure has a problem that delayed fracture resistance, toughness, workability, etc. are not good.
【００３４】従って、所定の強度と、優れた耐遅れ破壊
性を有する鋼を得るためには、通常の熱間圧延を行った
後直ちに焼入れするか、または再加熱してから焼入れ処
理を施して、鋼の組織を低温変態生成物（マルテンサイ
トやベイナイト）からなる組織とし、これを焼戻した、
いわゆる焼入れ焼戻し組織（主として焼戻しマルテンサ
イト組織）とすることが必要である。Therefore, in order to obtain a steel having a predetermined strength and an excellent delayed fracture resistance, quenching is performed immediately after usual hot rolling or after reheating and then quenching treatment. , The structure of the steel was made of low-temperature transformation products (martensite and bainite) and tempered,
It is necessary to have a so-called quenched and tempered structure (mainly tempered martensite structure).
【００３５】[0035]
【実施例】表１に示す化学組成の鋼(No.１〜30) を通常
の方法によって溶製した。 No.１〜26は本発明で定める
組成を有する鋼であり、 No.27〜30は本発明鋼の組成か
ら外れる比較鋼である。また、 No.31および32は従来鋼
で、それぞれJIS G 4801で規定されたSUP9およびSUP10
鋼である。 No.１〜30の溶製鋼については、得られたイ
ンゴットを1050〜1150℃に45分間加熱保持した後、 950
〜1100℃で熱間鍛造および熱間圧延して厚さ15mmの板材
とし、 900℃で45分間加熱して油焼入れし、次いで 420
℃で45分間焼戻して空冷することにより、その組織が焼
入れ焼戻し組織となり、引張強さが 110kg/mm2以上とな
るように調整した。 No.31および32の従来鋼についても
同様の焼入れ焼戻し処理を行った。EXAMPLES Steels (Nos. 1 to 30) having the chemical compositions shown in Table 1 were melted by a usual method. Nos. 1 to 26 are steels having the composition defined in the present invention, and Nos. 27 to 30 are comparative steels deviating from the composition of the steel of the present invention. Nos. 31 and 32 are conventional steels, SUP9 and SUP10 specified in JIS G 4801, respectively.
It is steel. For molten steel Nos. 1 to 30, the obtained ingot was heated and held at 1050 to 1150 ° C for 45 minutes, and then 950
Hot forged and hot rolled at ~ 1100 ℃ to 15mm thick plate, heated at 900 ℃ for 45 minutes for oil quenching, then 420
By tempering at 45 ° C. for 45 minutes and air cooling, the structure was adjusted to a quenched and tempered structure with a tensile strength of 110 kg / mm 2 or more. The same quenching and tempering treatment was performed on the conventional steels of Nos. 31 and 32.
【００３６】これらの鋼について、定荷重試験方法によ
り遅れ破壊性を調査した。すなわち、図４に示す形状お
よび寸法の試験片を切り出し、これを図５に示す定荷重
試験機に取り付け、pH＝２のワルポール液（塩酸と酢酸
ナトリウム水溶液の混合液、液温：25℃）中でおもり６
により静荷重（引張応力：50■f/mm2 ）をかけるととも
に試験片１と白金製の対極２の間にポテンシオスタット
３を用いて試験片１を陰極として定電流（１mA/cm2）を
流し、 200時間経過後の破断の発生の有無を調べた。The delayed fracture properties of these steels were investigated by the constant load test method. That is, a test piece having the shape and dimensions shown in FIG. 4 was cut out, attached to a constant load tester shown in FIG. 5, and a pH = 2 Walpol liquid (mixture of hydrochloric acid and sodium acetate aqueous solution, liquid temperature: 25 ° C.) Weight 6 in
Static load (tensile stress: 50 f / mm 2 ) is applied by using the potentiostat 3 between the test piece 1 and the platinum counter electrode 2, and the test piece 1 is used as a cathode at a constant current (1 mA / cm 2 ). Then, it was examined whether or not breakage occurred after 200 hours.
【００３７】試験結果を表１に示す。なお、同表には各
供試鋼の強度レベルを付記した。試験環境のpH＝２とい
うのは、材料が実際に使用される環境において生じる可
能性のある最も厳しい環境に相当する。したがって、こ
の試験結果は実際の使用環境のうちで最も厳しい環境下
における耐遅れ破壊性を評価できるものと考えられる。The test results are shown in Table 1. In addition, the strength level of each test steel is additionally shown in the table. A pH of 2 in the test environment corresponds to the most severe environment that may occur in the environment in which the material is actually used. Therefore, it is considered that this test result can evaluate the delayed fracture resistance under the most severe environment in the actual use environment.
【００３８】表１の結果から明らかなように、本発明鋼
は耐遅れ破壊性に優れており、かつ110kg/mm2以上の引
張強さを有している。As is clear from the results shown in Table 1, the steels of the present invention are excellent in delayed fracture resistance and have a tensile strength of 110 kg / mm 2 or more.
【００３９】[0039]
【表１（１）】 [Table 1 (1)]
【００４０】[0040]
【表１（２）】 [Table 1 (2)]
【００４１】[0041]
【発明の効果】本発明鋼は耐遅れ破壊性に優れ、かつ 1
10kg/mm2以上の引張強さを有しており、安価な低合金高
強度鋼として、特に、自動車の板ばねやコイルばね等の
素材として好適である。The steel of the present invention is excellent in delayed fracture resistance and
It has a tensile strength of 10 kg / mm 2 or more, and is suitable as an inexpensive low-alloy high-strength steel, particularly as a material for automobile leaf springs, coil springs, and the like.
【図１】鋼の（Cu＋Mo）含有量と水素透過係数の関係を
示す図である。FIG. 1 is a diagram showing a relationship between a (Cu + Mo) content of steel and a hydrogen permeation coefficient.
【図２】鋼のCu含有量と水素透過係数の関係を示す図で
ある。FIG. 2 is a diagram showing the relationship between the Cu content of steel and the hydrogen permeation coefficient.
【図３】鋼のMo含有量と水素透過係数の関係を示す図で
ある。FIG. 3 is a diagram showing the relationship between the Mo content of steel and the hydrogen permeation coefficient.
【図４】実施例の定荷重試験で用いた試験片の形状およ
び寸法（単位：mm）を示す図で、（イ）は試験片の全体
図、（ロ）は試験片のノッチ部（（イ）図のＡ部）の形
状の詳細図である。FIG. 4 is a view showing the shape and dimensions (unit: mm) of a test piece used in the constant load test of the example, (a) is an overall view of the test piece, and (b) is a notch part (( (A) It is a detailed view of the shape of A part of the figure.
【図５】定荷重試験機の概略構成図である。FIG. 5 is a schematic configuration diagram of a constant load tester.
【符号の説明】 １：試験片、２：対極、３：ポテンシオスタット、４：
ポンプ、５：恒温槽、６：おもり、７：加熱炉（部分）[Explanation of symbols] 1: test piece, 2: counter electrode, 3: potentiostat, 4:
Pump, 5: constant temperature bath, 6: weight, 7: heating furnace (part)
【手続補正書】[Procedure amendment]
【提出日】平成４年７月２１日[Submission date] July 21, 1992
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】００３６[Correction target item name] 0036
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【００３６】これらの鋼について、定荷重試験方法によ
り遅れ破壊性を調査した。すなわち、図４に示す形状お
よび寸法の試験片を切り出し、これを図５に示す定荷重
試験機に取り付け、pH＝２のワルポール液（塩酸と酢酸
ナトリウム水溶液の混合液、液温：25℃）中でおもり６
により静荷重（引張応力：50kgf/mm2 ）をかけるととも
に試験片１と白金製の対極２の間にポテンシオスタット
３を用いて試験片１を陰極として定電流（１mA/cm2）を
流し、 200時間経過後の破断の発生の有無を調べた。The delayed fracture properties of these steels were investigated by the constant load test method. That is, a test piece having the shape and dimensions shown in FIG. 4 was cut out and attached to the constant load tester shown in FIG. Weight 6 in
A static load (tensile stress: 50 kgf / mm 2 ) is applied to the test piece 1 and a constant current (1 mA / cm 2 ) is passed between the test piece 1 and the platinum counter electrode 2 using the potentiostat 3 as the cathode. After 200 hours, the presence or absence of breakage was examined.
Claims (4)
Si：0.05〜0.50％、Mn： 0.5％未満、Cu：0.10〜1.00
％、Cr：0.10〜5.00％、Mo：0.05〜1.00％、Al：0.01〜
0.10％を含有し、かつCu＋Mo≧ 0.4％を満たし、残部は
Feおよび不可避不純物からなり、不純物中のＰが 0.015
％未満、Ｓが0.01％未満であって、焼入れ焼き戻し組織
を有することを特徴とする耐遅れ破壊性に優れたばね用
鋼。1. By weight%, C: more than 0.50% and 0.90% or less,
Si: 0.05 to 0.50%, Mn: less than 0.5%, Cu: 0.10 to 1.00
%, Cr: 0.10 to 5.00%, Mo: 0.05 to 1.00%, Al: 0.01 to
Containing 0.10% and satisfying Cu + Mo ≧ 0.4%, the balance is
Consists of Fe and unavoidable impurities, and P in the impurities is 0.015
%, S is less than 0.01%, and has a quenched and tempered structure, which is a spring steel excellent in delayed fracture resistance.
％を含有することを特徴とする請求項１に記載の耐遅れ
破壊性に優れたばね用鋼。2. A spring steel excellent in delayed fracture resistance according to claim 1, further comprising Ni: 0.05 to 0.50% by weight as a constituent element.
％、Ti：0.01〜0.10重量％およびＶ：0.01〜0.10重量％
の中の１種以上を含有することを特徴とする請求項１ま
たは２に記載の耐遅れ破壊性に優れたばね用鋼。3. Nb: 0.01 to 0.10% by weight, Ti: 0.01 to 0.10% by weight and V: 0.01 to 0.10% by weight as constituent elements.
The spring steel excellent in delayed fracture resistance according to claim 1 or 2, containing at least one of the above.
重量％を含有することを特徴とする請求１、２または３
に記載の耐遅れ破壊性に優れたばね用鋼。4. B: 0.0002 to 0.002 as a constituent element
%, 5% or 3% by weight
Spring steel with excellent delayed fracture resistance as described in.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18662692A JP3232666B2 (en) | 1992-07-14 | 1992-07-14 | Spring steel with excellent delayed fracture resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18662692A JP3232666B2 (en) | 1992-07-14 | 1992-07-14 | Spring steel with excellent delayed fracture resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0633189A true JPH0633189A (en) | 1994-02-08 |
| JP3232666B2 JP3232666B2 (en) | 2001-11-26 |
Family
ID=16191876
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18662692A Expired - Lifetime JP3232666B2 (en) | 1992-07-14 | 1992-07-14 | Spring steel with excellent delayed fracture resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3232666B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2532761A (en) * | 2014-11-27 | 2016-06-01 | Skf Ab | Bearing steel |
| US9427091B2 (en) | 2008-04-18 | 2016-08-30 | Dreamwell, Ltd. | Microalloyed spring |
| CN106222578A (en) * | 2016-08-31 | 2016-12-14 | 宁国市华丰耐磨材料有限公司 | A kind of ferrum body spheroidal graphite cast-iron steel forging difficult to understand |
| US9573432B2 (en) | 2013-10-01 | 2017-02-21 | Hendrickson Usa, L.L.C. | Leaf spring and method of manufacture thereof having sections with different levels of through hardness |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101795278B1 (en) | 2016-06-21 | 2017-11-08 | 현대자동차주식회사 | Ultra high strength spring steel |
-
1992
- 1992-07-14 JP JP18662692A patent/JP3232666B2/en not_active Expired - Lifetime
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9427091B2 (en) | 2008-04-18 | 2016-08-30 | Dreamwell, Ltd. | Microalloyed spring |
| EP2286107B1 (en) * | 2008-04-18 | 2016-11-30 | Dreamwell, Ltd. | Microalloyed spring |
| EP3147532A1 (en) * | 2008-04-18 | 2017-03-29 | Dreamwell, Ltd. | Microalloyed spring |
| US9573432B2 (en) | 2013-10-01 | 2017-02-21 | Hendrickson Usa, L.L.C. | Leaf spring and method of manufacture thereof having sections with different levels of through hardness |
| US9890440B2 (en) | 2013-10-01 | 2018-02-13 | Hendrickson Usa, L.L.C. | Leaf spring and method of manufacture thereof having sections with different levels of through hardness |
| GB2532761A (en) * | 2014-11-27 | 2016-06-01 | Skf Ab | Bearing steel |
| CN106222578A (en) * | 2016-08-31 | 2016-12-14 | 宁国市华丰耐磨材料有限公司 | A kind of ferrum body spheroidal graphite cast-iron steel forging difficult to understand |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3232666B2 (en) | 2001-11-26 |
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