JP2686755B2 - High-strength steel with excellent fatigue strength - Google Patents
High-strength steel with excellent fatigue strengthInfo
- Publication number
- JP2686755B2 JP2686755B2 JP62334211A JP33421187A JP2686755B2 JP 2686755 B2 JP2686755 B2 JP 2686755B2 JP 62334211 A JP62334211 A JP 62334211A JP 33421187 A JP33421187 A JP 33421187A JP 2686755 B2 JP2686755 B2 JP 2686755B2
- Authority
- JP
- Japan
- Prior art keywords
- steel
- fatigue strength
- less
- strength
- present
- 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］
本発明は構造用部材、特に産業用車両のシャフト、足
回り部品等に用いられる疲労強度、焼入性、被削性に優
れた安価な強靭鋼に関するものである。
［従来の技術］
従来、産業車両のシャフト、足廻り部品等に用いられ
る構造用鋼としては、SCM440またはSCr440等の強靭鋼が
使用されていた。しかしながら、最近自動車に見られる
エンジン出力の増大により、従来に比べて高荷重下で使
用され、前記の従来材の耐久限が47kgf/mm2、硬さがHv2
90程度では疲労強度が若干不足するという問題が生じて
きた。また、従来材であるSCM440はMoを含有しているた
め、Mo資源の入手難と高騰により、コスト高になるとい
う問題がある。
［発明が解決しようとする問題点］
本発明は強靭鋼の前記のごとき問題点に鑑み、疲労強
度を改善し、省Mo化によりコストの低減を図るべくなさ
れたものであって、耐久限50kgf/mm2、硬さHv320程度で
疲労強度に優れ、かつ焼入性および切削性にも優れ、さ
らに高価なMoを含有せずコスト的に安価な強靭鋼を提供
することを目的とする。
［問題点を解決するための手段］
本発明者等は強靭鋼に及ぼす各種添加元素の影響につ
き鋭意従研究を重ねた。その結果疲労強度を向上させる
にはＣおよびMn添加量を増加すること、また微量のＢを
添加することが効果的であることを見出だした。さら
に、Tiを添加すると共に、ＮおよびＯの含有量を低減し
清浄度を増し、Ti/Nの比を規制することにより、Ｂ添加
の有効性を確保し疲労強度の増加することを見出だし
た。そして、MnとＢの添加は同時に焼入性をも改善する
ものである。
しかして、本発明は前記のごとき発明者等の新たな知
見に基づき完成されたものであって、本発明の第１発明
の疲労強度が優れた強靭鋼は、重量％でC;0.30〜0.55
％、Si;0.15〜0.35％、Mn;1.00〜2.00％、S;0.040％以
下、B;0.0010〜0.0040％、Ti;0.02〜0.05％、N;0.0080
％以下、O;0.0030％以下、Al;0.020％〜0.040％を含有
し、Ti/Nが３以上であり、残部がFeならびに不純物元素
からなり、焼入焼戻し処理することを要旨とする。
また、第２発明の疲労強度が優れた強靭鋼は、重量％
でC;0.30〜0.55％、Si;0.15〜0.35％、Mn;1.00〜2.00
％、S;0.040％以下、B;0.0010〜0.0040％、Ti;0.02〜0.
05％、N;0.0080％以下、O;0.0030％以下、Al;0.020％〜
0.040％を含有し、Ti/Nが３以上であり、さらにCr;0.40
％以下を含有し、残部がFeならびに不純物元素からな
り、焼入焼戻し処理することを要旨とする。
［作用］
本発明の疲労強度が優れた強靭鋼は、ＣおよびMn量を
増加することにより、疲労強度が向上している。また、
Ｂを添加することにより焼入性と併せて疲労強度の向上
が図られている。また、Tiの添加がさらに疲労強度を増
加させると共に、ＮおよびＯ量の上限を規制することに
より鋼の清浄度を保ち、Ti/Nを規制することによりＢ添
加の有効性が確保される。以下に本発明の成分限度理由
について説明する。
C;0.30〜0.55％
Ｃはシャフト等の構造部材として必要な疲労強度を得
るために0.30％以上が必要である。しかし、Ｃ含有量が
0.55％を越えると高周波焼入れ時に焼き割れが発生しや
すくなり、さらに切削等の加工性が悪くなるので上限を
0.55％とした。
Si;0.15〜0.35％
Siは製鋼時の脱酸のために0.15％以上が必要である。
しかし、0.35％を越えるとフェライトを強化して加工性
を害し、かつ酸化物系の介在物が増加するので、上限を
0.35％とした。
Mn;1.00〜2.00％
Mnは疲労強度と焼入性を確保するために1.00％以上が
必要である。しかし、2.00％を越えて含有されると圧延
後の硬さが上昇し、シヤ切断時に割れが発生しやすくな
り、切削性を害し、さらに焼なまし後の硬さが上昇する
等の欠点が出るので、上限を2.00％とした。
Cr;0.40％以下
Crは焼入性を改善するために必要な元素であるが、0.
40％を越えるとその効果は飽和しコストも上昇するの
で、上限を0.40％とした。B;0.0010〜0.0040％
Ｂは焼入性を改善するために添加されるが、0.0010％
未満であると充分な焼入性が得られず疲労強度が低下す
るので下限を0.0010％とした。しかし、0.0040％を越え
るとBCが粒界に生成し衝撃特性が低下するので、その上
限を0.0040％とした。
Ti;0.02〜0.05％
TiはＮを固定しBNの生成を防止するために0.02％以上
が添加される。しかし、Tiの添加が0.05％を越えると清
浄度を害し却って疲労強度を低下させるので、上限を0.
05％以上とした。N;0.0080％以下
Ｎは不純物元素として鋼に含まれるが、多量に存在す
るとBNを生成しＢ添加の効果を無効化するので、その上
限を0.0080％とした。
Ti/N;3以上
Ti/NはＢの添加に影響を及ぼすＮがどれだけTiによっ
て固定されたかを示す数値であり、Ti/Nの比が３未満で
あると有効Ｂの確保が困難となるのでその比の下限を３
とした。
O;0.0030％以下
ＯはAl2O3、TiO2等の酸化物系の介在物を生成し、清
浄度を害するので、その上限を0.0030％とした。
S;0.040％以下
Ｓは切削性を改善するために必要な元素であるが、0.
040％を越えて添加すると清浄度を害し疲労強度を低下
させるので、上限を0.040％とした。
Al;0.020〜0.040％
Alは製鋼時の脱酸のための結晶粒を微細化するために
0.020％以上が添加される。しかし、あまり多く添加す
ると清浄度を害するので、上限を0.040％とした。
［実施例］
次に本発明の特徴を従来鋼、比較鋼と比べて実施例で
もって明らかにする。
第１表はこれら供試鋼の化学成分を示すものである。
第１表において、供試鋼のＡ〜Ｅ鋼は第１発明の鋼、Ｆ
鋼は第２発明の鋼、Ｇ鋼はSCM440に相当する従来鋼、同
じくＨ鋼はSCr440に相当する従来鋼、Ｉ鋼は本発明鋼の
組成でMn含有量だけが低い比較鋼、Ｊ鋼は本発明鋼の組
成でＢ含有量だけが低い比較鋼、Ｋ鋼は本発明鋼の組成
でＮ含有量だけが高い比較鋼である。 第２表は第１表の供試鋼について硬さ、耐久限をしめ
したものである。硬さについては焼入れ焼戻しした後ビ
ッカー硬度（Hv）を測定し結果を第２表に示した。耐久
限については、小野式回転曲げ疲れ試験機を測定した。
第２表から明らかなように、Mn含有量の低い比較例Ｉ
鋼、Ｂ含有量の低かった比較例Ｊ鋼およびＮ含有量の高
かった比較例Ｋ鋼のビッカース硬さHv260から320の平滑
耐久限は34.0〜46.0kgf/mm2であり、切欠耐久限は17.6
〜21.0kgf/mm2であって、SCM440に相当する従来鋼のＧ
鋼の平滑耐久限47.8〜59.4kgf/mm2、切欠耐久限24.7〜2
7.0kgf/mm2およびSCr440に相当する従来鋼であるＨ鋼の
平滑耐久限44.0〜56.0kgf/mm2、切欠耐久限22.8〜25.5k
gf/mm2に比較して低い値を示した。
これに対して本発明鋼であるＡ〜Ｆ鋼は平滑耐久限で
43.5〜60.0kgf/mm2、切欠耐久限で22.5〜27.5kgf/mm2で
あって、従来鋼であるＧ鋼およびＨ鋼と同等またはそれ
以上の耐久限を示し、本発明の効果が確認された。
［発明の効果］
本発明の疲労強度の優れた強靭鋼は以上説明したよう
に、ＣおよびMn添加量を増加すると共に、微量のＢを添
加することにより疲労強度を改善したものである。さら
に、Tiを添加すると共に、ＮおよびＯの含有量を低減し
清浄度を増し、Ti/Nの比を規制することにより、Ｂ添加
の有効性を確保し、焼入性を改善するものであって、従
来鋼よりも優れた疲労強度を示すと共に、Cr量を低減し
Moの添加を省略できるという効果がある。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is an inexpensive and excellent in fatigue strength, hardenability and machinability used for structural members, particularly shafts and undercarriage parts of industrial vehicles. It relates to tough steel. [Prior Art] Conventionally, as structural steel used for shafts, suspension parts and the like of industrial vehicles, tough steels such as SCM440 or SCr440 have been used. However, due to the increase in engine power recently seen in automobiles, it is used under higher loads than before, and the durability of the above-mentioned conventional materials is 47 kgf / mm 2 , and the hardness is Hv2
At about 90, there is a problem that the fatigue strength is slightly insufficient. In addition, since SCM440, which is a conventional material, contains Mo, there is a problem that the cost becomes high due to difficulty in obtaining Mo resources and soaring. [Problems to be Solved by the Invention] The present invention has been made in view of the above problems of a tough steel to improve fatigue strength and reduce cost by saving Mo, and has a durability limit of 50 kgf. / mm 2, excellent fatigue strength at about hardness Hv320, and also excellent in hardenability and cuttability, further an object to provide a cost-expensive tough steel does not contain expensive Mo. [Means for Solving Problems] The inventors of the present invention have earnestly conducted research on the influence of various additive elements on tough steel. As a result, it has been found that it is effective to increase the amounts of C and Mn added and to add a small amount of B to improve the fatigue strength. Further, it was found that by adding Ti, by reducing the contents of N and O to increase cleanliness and regulating the Ti / N ratio, the effectiveness of B addition is secured and the fatigue strength is increased. It was The addition of Mn and B simultaneously improves hardenability. Therefore, the present invention has been completed based on the above-mentioned new findings of the inventors, and the toughness steel having excellent fatigue strength of the first invention of the present invention is C; 0.30 to 0.55% by weight.
%, Si; 0.15-0.35%, Mn; 1.00-2.00%, S; 0.040% or less, B; 0.0010-0.0040%, Ti; 0.02-0.05%, N; 0.0080
% Or less, O: 0.0030% or less, Al: 0.020% to 0.040%, Ti / N is 3 or more, and the balance is Fe and impurity elements. In addition, the high strength steel of the second invention having excellent fatigue strength is
At C; 0.30 to 0.55%, Si; 0.15 to 0.35%, Mn; 1.00 to 2.00
%, S; 0.040% or less, B; 0.0010 to 0.0040%, Ti; 0.02 to 0.
05%, N; 0.0080% or less, O; 0.0030% or less, Al; 0.020% ~
Contains 0.040%, Ti / N is 3 or more, and Cr; 0.40
% Or less, the balance consisting of Fe and impurity elements, and the main point is to perform quenching and tempering. [Operation] In the high-strength steel of the present invention having excellent fatigue strength, the fatigue strength is improved by increasing the amounts of C and Mn. Also,
By adding B, the hardenability and the fatigue strength are improved. Further, the addition of Ti further increases the fatigue strength, maintains the cleanliness of the steel by regulating the upper limits of the amounts of N and O, and secures the effectiveness of the addition of B by regulating Ti / N. The reasons for limiting the components of the present invention will be described below. C: 0.30 to 0.55% C is required to be 0.30% or more in order to obtain the fatigue strength required as a structural member such as a shaft. However, the C content
If it exceeds 0.55%, quenching cracks are likely to occur during induction hardening, and workability such as cutting deteriorates.
0.55%. Si: 0.15 to 0.35% Si needs to be 0.15% or more for deoxidation during steelmaking.
However, if it exceeds 0.35%, ferrite is strengthened, workability is impaired, and oxide-based inclusions increase, so the upper limit is set.
0.35%. Mn: 1.00 to 2.00% Mn needs to be 1.00% or more to ensure fatigue strength and hardenability. However, if the content exceeds 2.00%, the hardness after rolling increases, cracks tend to occur during shear cutting, the machinability is impaired, and the hardness after annealing further increases. Since it comes out, the upper limit was set to 2.00%. Cr: 0.40% or less Cr is an element necessary for improving hardenability.
If it exceeds 40%, the effect will be saturated and the cost will increase, so the upper limit was set to 0.40%. B: 0.0010-0.0040% B is added to improve hardenability, but 0.0010%
If it is less than 30%, sufficient hardenability cannot be obtained and the fatigue strength decreases, so the lower limit was made 0.0010%. However, when the content exceeds 0.0040%, BC is formed at the grain boundary and the impact characteristics deteriorate, so the upper limit is made 0.0040%. Ti: 0.02 to 0.05% Ti is added in an amount of 0.02% or more to fix N and prevent generation of BN. However, if the addition of Ti exceeds 0.05%, the cleanliness is impaired and the fatigue strength is reduced, so the upper limit is set to 0.
05% or more. N; 0.0080% or less N is contained in steel as an impurity element, but if it is present in a large amount, it forms BN and nullifies the effect of B addition, so the upper limit was made 0.0080%. Ti / N; 3 or more Ti / N is a numerical value that shows how much N that influences the addition of B is fixed by Ti. If the Ti / N ratio is less than 3, it is difficult to secure effective B. Therefore, the lower limit of the ratio is 3
And O: 0.0030% or less O generates oxide-based inclusions such as Al 2 O 3 and TiO 2 and impairs cleanliness. Therefore, the upper limit is made 0.0030%. S: 0.040% or less S is an element necessary for improving machinability, but
If added in excess of 040%, cleanliness will be impaired and fatigue strength will be reduced, so the upper limit was made 0.040%. Al; 0.020-0.040% Al is used to refine the crystal grains for deoxidation during steelmaking.
0.020% or more is added. However, if too much is added, the cleanliness is impaired, so the upper limit was made 0.040%. [Examples] Next, the features of the present invention will be clarified by examples in comparison with conventional steels and comparative steels. Table 1 shows the chemical composition of these test steels.
In Table 1, the test steels A to E are steels of the first invention, F.
The steel is the steel of the second invention, the G steel is the conventional steel corresponding to SCM440, the H steel is the conventional steel corresponding to SCr440, the I steel is the comparative steel with the composition of the invention steel and only the Mn content is low, and the J steel is The comparative steel having a low B content only in the composition of the present invention, and the K steel are comparative steels having a high N content in the composition of the present invention. Table 2 shows the hardness and durability of the test steels in Table 1. Regarding hardness, Vickers hardness (Hv) was measured after quenching and tempering, and the results are shown in Table 2. The Ono type rotary bending fatigue tester was used to measure the endurance limit. As is clear from Table 2, Comparative Example I having a low Mn content
Steel, Comparative Example J with low B content and Comparative Example K with high N content have Vickers hardness of Hv 260 to 320 of 34.0 to 46.0 kgf / mm 2 , smoothness limit of 17.6, and notch durability of 17.6.
A ~21.0kgf / mm 2, G of conventional steel equivalent to SCM440
Steel smooth endurance 47.8-59.4 kgf / mm 2 , notch endurance 24.7-2
The conventional steel H steel equivalent to 7.0kgf / mm 2 and SCr440 has a smooth durability of 44.0 to 56.0kgf / mm 2 and a notch durability of 22.8 to 25.5k.
The value was lower than that of gf / mm 2 . On the other hand, the steels A to F, which are the steels of the present invention, have a smooth durability limit.
43.5 to 60.0 kgf / mm 2 and a notch durability limit of 22.5 to 27.5 kgf / mm 2 , exhibiting a durability limit equal to or higher than that of conventional steels G steel and H steel, confirming the effect of the present invention. It was [Effects of the Invention] As described above, the tough steel having excellent fatigue strength according to the present invention has improved fatigue strength by increasing the amounts of C and Mn added and adding a small amount of B. Furthermore, by adding Ti, reducing the contents of N and O to increase cleanliness and controlling the Ti / N ratio, the effectiveness of B addition is secured and the hardenability is improved. Therefore, the fatigue strength is superior to that of conventional steel and the Cr content is reduced.
The effect is that the addition of Mo can be omitted.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 内山 雅夫 愛知県東海市荒尾町ワノ割１番地 愛知 製鋼株式会社内 (56)参考文献 特開 昭55−104456（ＪＰ，Ａ) 特開 昭60−230960（ＪＰ，Ａ) ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Uchiyama 1 Wano Wari, Arao-cho, Tokai-shi, Aichi Aichi Steelmaking Co., Ltd. (56) References JP-A-55-104456 (JP, A) JP-A-60-230960 (JP, A)
Claims (1)
00〜2.00％、S;0.040％以下、B;0.0010〜0.0040％、Ti;
0.02〜0.05％、N;0.0080％以下、O;0.0030％以下、Al;
0.020％〜0.040％を含有し、Ti/Nが３以上であり、残部
がFeならびに不純物元素からなり、焼入焼戻し処理する
ことを特徴とする疲労強度が優れた強靭鋼。 ２．重量％でC;0.30〜0.55％、Si;0.15〜0.35％、Mn;1.
00〜2.00％、S;0.040％以下、B;0.0010〜0.0040％、Ti;
0.02〜0.05％、N;0.0080％以下、O;0.0030％以下、Al;
0.020％〜0.040％を含有し、Ti/Nが３以上であり、さら
にCr;0.40％以下を含有し、残部がFeならびに不純物元
素からなり、焼入焼戻し処理することを特徴とする疲労
強度が優れた強靭鋼。(57) [Claims] %; C; 0.30 to 0.55%, Si; 0.15 to 0.35%, Mn; 1.
00-2.00%, S; 0.040% or less, B; 0.0010-0.0040%, Ti;
0.02-0.05%, N; 0.0080% or less, O; 0.0030% or less, Al;
A tough steel with excellent fatigue strength, characterized by containing 0.020% to 0.040%, Ti / N of 3 or more, the balance consisting of Fe and impurity elements, and being quenched and tempered. 2. %; C; 0.30 to 0.55%, Si; 0.15 to 0.35%, Mn; 1.
00-2.00%, S; 0.040% or less, B; 0.0010-0.0040%, Ti;
0.02-0.05%, N; 0.0080% or less, O; 0.0030% or less, Al;
It contains 0.020% to 0.040%, Ti / N is 3 or more, Cr: 0.40% or less, the balance is Fe and impurity elements, and the fatigue strength is characterized by quenching and tempering. Excellent tough steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62334211A JP2686755B2 (en) | 1987-12-29 | 1987-12-29 | High-strength steel with excellent fatigue strength |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62334211A JP2686755B2 (en) | 1987-12-29 | 1987-12-29 | High-strength steel with excellent fatigue strength |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01176056A JPH01176056A (en) | 1989-07-12 |
| JP2686755B2 true JP2686755B2 (en) | 1997-12-08 |
Family
ID=18274785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62334211A Expired - Lifetime JP2686755B2 (en) | 1987-12-29 | 1987-12-29 | High-strength steel with excellent fatigue strength |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2686755B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2725747B2 (en) * | 1990-11-16 | 1998-03-11 | 大同特殊鋼株式会社 | Steel for induction hardening |
| KR940002139B1 (en) * | 1991-11-30 | 1994-03-18 | 삼성중공업 주식회사 | Carburized boron steels for gears |
| FR2780984B1 (en) * | 1998-07-09 | 2001-06-22 | Lorraine Laminage | COATED HOT AND COLD STEEL SHEET HAVING VERY HIGH RESISTANCE AFTER HEAT TREATMENT |
| KR100392469B1 (en) * | 2000-05-17 | 2003-07-22 | 임효빈 | liquid discharge apparatus of flexible receptacle |
| JP4738842B2 (en) * | 2005-02-28 | 2011-08-03 | 株式会社吉野工業所 | Dispensing container |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55104456A (en) * | 1979-02-01 | 1980-08-09 | Sumitomo Metal Ind Ltd | Machine structural boron steel |
| JPS60230960A (en) * | 1984-04-27 | 1985-11-16 | Daido Steel Co Ltd | Steel for cold forging |
| JPS61257457A (en) * | 1985-05-07 | 1986-11-14 | Kobe Steel Ltd | Steel sheet for laser processing having superior fatigue characteristic |
-
1987
- 1987-12-29 JP JP62334211A patent/JP2686755B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01176056A (en) | 1989-07-12 |
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