JP2003073769A - High strength mechanical structural steel - Google Patents
High strength mechanical structural steelInfo
- Publication number
- JP2003073769A JP2003073769A JP2001264399A JP2001264399A JP2003073769A JP 2003073769 A JP2003073769 A JP 2003073769A JP 2001264399 A JP2001264399 A JP 2001264399A JP 2001264399 A JP2001264399 A JP 2001264399A JP 2003073769 A JP2003073769 A JP 2003073769A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- strength
- tempering
- delayed fracture
- structural steel
- 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.)
- Granted
Links
- 229910000746 Structural steel Inorganic materials 0.000 title claims abstract description 22
- 238000005496 tempering Methods 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 19
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 18
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 16
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 14
- 238000011282 treatment Methods 0.000 claims abstract description 13
- 238000005275 alloying Methods 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910000831 Steel Inorganic materials 0.000 claims description 83
- 239000010959 steel Substances 0.000 claims description 83
- 239000000463 material Substances 0.000 claims description 30
- 238000010791 quenching Methods 0.000 claims description 7
- 230000000171 quenching effect Effects 0.000 claims description 6
- 230000003111 delayed effect Effects 0.000 abstract description 37
- 229910052799 carbon Inorganic materials 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 abstract description 4
- 229910045601 alloy Inorganic materials 0.000 description 12
- 239000000956 alloy Substances 0.000 description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 11
- 229910052739 hydrogen Inorganic materials 0.000 description 11
- 239000001257 hydrogen Substances 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 229910001567 cementite Inorganic materials 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 7
- 150000001247 metal acetylides Chemical class 0.000 description 7
- 238000009792 diffusion process Methods 0.000 description 6
- 239000006104 solid solution Substances 0.000 description 5
- 239000002131 composite material Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 230000000930 thermomechanical effect Effects 0.000 description 4
- 229910000599 Cr alloy Inorganic materials 0.000 description 3
- 229910000676 Si alloy Inorganic materials 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910001182 Mo alloy Inorganic materials 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 229910001240 Maraging steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
(57)【要約】
【課題】 単純な組成からなるためにリサイクル性に優
れ、なおかつ複雑な加工熱処理を必要としない、耐遅れ
破壊特性に優れた新規な高強度機械構造用鋼を提供す
る。
【解決手段】 組成が、重量％で、Ｃ：０．２〜０．７
％、Ｓｉ：０．２〜２．５％、Ｍｎ：０．０５〜１．０
％、Ｃｒ：０．２〜１．５％、Ｍｏ：０．３〜１．５％
で、かつ合金元素の総量が、Ｓｉ＋Ｍｎ＋Ｃｒ＋Ｍｏ≦
５重量％を満たし、残部がＦｅおよび不可避的不純物か
らなる鋼材であって、５００℃〜Ａｅ1点以下の温度範
囲で、焼きもどしパラメーター：λが、λ＝Ｔ（２０＋
ｌｏｇｔ）≧１５８００（式中、Ｔは温度（Ｋ）、ｔは
時間（ｈ）を示す）となる条件で焼きもどし処理を施さ
れ、引張強さが１８００ＭＰａ以上である高強度機械構
造用鋼とする。
PROBLEM TO BE SOLVED: To provide a novel high-strength mechanical structural steel excellent in delayed fracture resistance, which is excellent in recyclability because it has a simple composition and does not require complicated working heat treatment. SOLUTION: The composition is represented by weight%, C: 0.2 to 0.7.
%, Si: 0.2-2.5%, Mn: 0.05-1.0
%, Cr: 0.2-1.5%, Mo: 0.3-1.5%
And the total amount of alloying elements is Si + Mn + Cr + Mo ≦
5% by weight, the balance being Fe and unavoidable impurities, and in a temperature range from 500 ° C. to 1 Ae or less, tempering parameter: λ is λ = T (20+
logt) ≧ 15800 (where T represents temperature (K) and t represents time (h)) and subjected to a tempering treatment and has a tensile strength of 1800 MPa or more for high-strength mechanical structural steel. I do.
Description
【０００１】[0001]
【発明の属する技術分野】この出願の発明は、高強度機
械構造用鋼に関するものである。さらに詳しくは、この
出願の発明は、単純な組成からなるためにリサイクル性
に優れ、なおかつ複雑な加工熱処理を必要としない、耐
遅れ破壊特性に優れた新規な高強度機械構造用鋼に関す
るものである。TECHNICAL FIELD The present invention relates to high-strength steel for mechanical structures. More specifically, the invention of this application relates to a new high-strength mechanical structural steel excellent in delayed fracture resistance, which is excellent in recyclability due to its simple composition, and does not require complicated thermomechanical treatment. is there.
【０００２】[0002]
【従来の技術とその課題】近年の構造物の大型化や自動
車部品等の軽量化に伴い、今まで以上に高い強度を有す
る機械構造用鋼の実現が求められている。それと同時
に、環境負荷の低減の観点から、材料設計の全般におい
ては、リサイクル性を考慮した単純かつ低合金組成の鋼
材の開発が望まれてもいる。2. Description of the Related Art With the recent increase in the size of structures and the weight reduction of automobile parts and the like, it is required to realize mechanical structural steel having higher strength than ever. At the same time, from the viewpoint of reducing the environmental load, it is desired to develop a steel material having a simple and low alloy composition in consideration of recyclability in the overall material design.
【０００３】しかしながら、鋼を１２００ＭＰａ以上に
高強度化すると、耐遅れ破壊特性が著しく低下すること
が一般に知られている。そして、１２００ＭＰａ以上で
優れた耐遅れ破壊特性を示す鋼材としては、高合金組成
のマルエージング鋼や特殊な加工熱処理を施したピアノ
線が知られている程度であり、汎用性のある高強度の機
械構造用鋼については実現されていないのが実状であ
る。高強度の機械構造用鋼について耐遅れ破壊特性を向
上させることができれば、構造物の安全性や信頼性を高
めるだけでなく、使用寿命の長期化や材料の省資源化に
もつながるため、社会的な貢献度は極めて大きい。すな
わち、汎用性のある高強度の機械構造用鋼の実現には、
遅れ破壊を克服することが最重要課題とされている。However, it is generally known that when the strength of steel is increased to 1200 MPa or more, the delayed fracture resistance is significantly deteriorated. As a steel material showing excellent delayed fracture resistance at 1200 MPa or more, a maraging steel having a high alloy composition and a piano wire that has been subjected to a special thermomechanical treatment are known, and have high versatility and high strength. The reality is that it has not been realized for machine structural steel. If the delayed fracture resistance of high-strength machine structural steel can be improved, it not only enhances the safety and reliability of the structure, but also prolongs the service life and saves resources of materials. Contribution is extremely large. In other words, in order to realize versatile and high-strength steel for machine structural use,
Overcoming delayed destruction is the most important issue.
【０００４】この課題を解決するために、従来より、遅
れ破壊の大半が旧γ粒界を起点とすることに着目して、
旧γ粒界の強度を高めることで遅れ破壊を抑制するよう
にした対策が講じられている。具体的には、旧γ粒界を
脆化させるＰ、Ｓ等の不純物元素を低減させ、高温焼き
もどしにより粒界セメンタイトを球状化させることで、
旧γ粒界の強度を高めるようにする方法がある。In order to solve this problem, attention has been paid to the fact that the majority of delayed fracture originates from the old γ grain boundary,
Measures have been taken to suppress delayed fracture by increasing the strength of the old γ grain boundary. Specifically, by reducing the impurity elements such as P and S that embrittle the old γ grain boundary and making the grain boundary cementite spherical by high temperature tempering,
There is a method of increasing the strength of the old γ grain boundary.
【０００５】この高温焼きもどしによる方法について
は、耐遅れ破壊特性に優れ、比較的高強度の鋼材が得ら
れる方法がいくつか提案されているのものの、焼きもど
し軟化抵抗を示す合金元素の複合添加が必要不可欠とさ
れ、低合金化は実現されていない。また、その加熱処理
については、強度低下を避けるため５００℃以下の温度
で焼きもどすか、あるいはオースフォーミングなどの複
雑な加工熱処理を必要としている。Regarding this method by high-temperature tempering, although several methods have been proposed for obtaining steel materials having excellent delayed fracture resistance and relatively high strength, composite addition of alloying elements exhibiting temper softening resistance is proposed. Is essential, and low alloying has not been realized. Further, regarding the heat treatment, in order to avoid a decrease in strength, it is necessary to temper at a temperature of 500 ° C. or lower, or to perform a complicated heat treatment such as ausforming.
【０００６】一方で、最近になって、Ｖ、Ｔｉ、Ｎｂ等
の炭化物の析出に関連する水素トラップを利用して遅れ
破壊を抑制することが注目されているが、これらの元素
の働きは必ずしも明確ではなく、また低合金化について
も有効な策とはなり得ていなかった。On the other hand, recently, attention has been focused on suppressing delayed fracture by utilizing a hydrogen trap associated with the precipitation of carbides such as V, Ti and Nb, but the functions of these elements are not always required. It is not clear, and it has not been an effective measure for low alloying.
【０００７】そこで、この出願の発明は、以上の通りの
事情に鑑みてなされたものであり、従来技術の問題点を
解消し、単純な組成からなるためにリサイクル性に優
れ、なおかつ複雑な加工熱処理を必要としない、高強度
を有する耐遅れ破壊特性に優れた新規な機械構造用鋼を
提供することを課題としている。Therefore, the invention of this application has been made in view of the circumstances as described above, and solves the problems of the prior art and is excellent in recyclability due to its simple composition, and complicated processing. An object of the present invention is to provide a new steel for machine structural use, which does not require heat treatment and has high strength and excellent in delayed fracture resistance.
【０００８】[0008]
【課題を解決するための手段】そこで、この出願の発明
は、以上の通りの事情に鑑みてなされたものであり、従
来技術の問題点を解消し、以下の通りの発明を提供す
る。The invention of this application has been made in view of the circumstances as described above, and solves the problems of the prior art and provides the following invention.
【０００９】すなわち、まず第１には、この出願の発明
は、組成が、重量％で、Ｃ ：０．２〜０．７％、Ｓ
ｉ：０．２〜２．５％、Ｍｎ：０．０５〜１．０％、Ｃ
ｒ：０．２〜１．５％、Ｍｏ：０．３〜１．５％で、か
つ合金元素の総量が、
Ｓｉ＋Ｍｎ＋Ｃｒ＋Ｍｏ≦５重量％
を満たし、残部がＦｅおよび不可避的不純物からなる鋼
材であって、５００℃〜Ａｅ1点以下の温度範囲で、焼
きもどしパラメーター：λが、
λ＝Ｔ（２０＋ｌｏｇｔ）≧１５８００
（式中、Ｔは温度（Ｋ）、ｔは時間（ｈ）を示す）とな
る条件で焼きもどし処理が施され、引張強さ（σB）が
１８００ＭＰａ以上であることを特徴とする高強度機械
構造用鋼を提供する。That is, first of all, according to the invention of this application, the composition is% by weight, C: 0.2 to 0.7%, S.
i: 0.2 to 2.5%, Mn: 0.05 to 1.0%, C
r: 0.2 to 1.5%, Mo: 0.3 to 1.5%, the total amount of alloying elements satisfies Si + Mn + Cr + Mo ≦ 5 wt%, and the balance is Fe and inevitable impurities. Then, in the temperature range of 500 ° C. to Ae 1 point or less, the tempering parameter: λ is λ = T (20 + logt) ≧ 15800 (wherein T represents temperature (K) and t represents time (h)). Provided is a high-strength mechanical structural steel which is subjected to a tempering treatment under the following conditions and has a tensile strength (σ B ) of 1800 MPa or more.
【００１０】また、この出願の発明は、上記第１の発明
について、第２には、焼入れ処理の前に、鍛錬成形比で
４以上の鍛造を施されていることを特徴とする高強度機
械構造用鋼を、第３には、不純物としてのＰ、Ｓの含有
量が、０．０１重量％以下であることを特徴とする高強
度機械構造用鋼を、第４には、Ｍｏの代わりにＷが０．
３〜１．５重量％含まれていることを特徴とする高強度
機械構造用鋼を提供する。The invention of this application is, with respect to the above-mentioned first invention, secondly, a high-strength machine characterized by being forged by a wrought forming ratio of 4 or more before quenching. Structural steel, third, high strength mechanical structural steel, characterized in that the content of P, S as impurities is 0.01 wt% or less, fourth, instead of Mo W is 0.
Provided is a high-strength steel for machine structural use, which is characterized by containing 3 to 1.5% by weight.
【００１１】[0011]
【発明の実施の形態】この出願の発明は、上記の通りの
特徴を持つものであるが、以下にその実施の形態につい
て詳しく説明する。BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the characteristics as described above, and the embodiments thereof will be described in detail below.
【００１２】この出願の発明者らは、鋼の高強度化と耐
遅れ破壊特性の向上をより単純な組成で実現するため
に、まず、５００℃以上での焼きもどしにおけるＭｏ炭
化物の超微細析出による鋼材の２次硬化に着目した。そ
してさらに、多数の合金元素の中から、複合添加元素と
して鉄炭化物に固溶しないＳｉおよび固溶するＣｒを選
定して、Ｍｏ、ＳｉおよびＣｒの合金元素の複合添加が
鉄の強度と遅れ破壊特性に及ぼす影響を詳細に調査し
た。[0012] In order to realize high strength of steel and improvement of delayed fracture resistance with a simpler composition, the inventors of this application first superfinely precipitate Mo carbide in tempering at 500 ° C or higher. Attention was paid to the secondary hardening of the steel material. Furthermore, Si and Cr which are not solid-dissolved in iron carbide are selected as a composite additive element from a large number of alloy elements, and the composite addition of Mo, Si and Cr alloy elements causes the strength and delayed fracture of iron. The effect on properties was investigated in detail.
【００１３】その結果、この出願の発明者らは、Ｍｏ、
Ｓｉ、Ｃｒ合金元素の複合添加により、（１）Ｍｏ添加
による鋼材の硬さの極大が５００〜６００℃付近に現わ
れること、また（２）Ｓｉはおよそ３５０℃以下の低温
域、Ｃｒはおよそ４００℃以上の高温域での焼きもどし
による軟化を顕著に抑制できること、そして焼きもどし
処理後の鋼材についても、（３）１８００ＭＰａ以上と
いう強度レベルを維持することができることを見出し
た。そして更なる検討を重ねた結果、上記の高温焼きも
どしの条件と効果、および、Ｍｏ、Ｓｉ、Ｃｒ、Ｍｎ元
素の複合添加による効果を巧みに組み合わせることによ
り、（４）耐遅れ破壊特性を大幅に向上させることがで
きるという全く新しい知見を得るに至った。As a result, the inventors of the present application have found that Mo,
By the combined addition of Si and Cr alloy elements, (1) the maximum hardness of the steel material due to the addition of Mo appears in the vicinity of 500 to 600 ° C, and (2) Si is in the low temperature range of about 350 ° C or less, and Cr is about 400. It was found that softening due to tempering in a high temperature range of ℃ or more can be remarkably suppressed, and that the strength level of (3) 1800 MPa or more can be maintained even for the steel material after the tempering treatment. As a result of further studies, by skillfully combining the above-mentioned conditions and effects of high-temperature tempering and the effects of the combined addition of Mo, Si, Cr, and Mn elements, (4) delayed fracture resistance is significantly improved. We have gained a completely new finding that it can be improved.
【００１４】すなわち、この出願の発明の提供する高強
度機械構造用鋼は、Ｓｉ、Ｍｎ、ＣｒおよびＭｏのみを
合金元素とする単純な組成を有し、それぞれが重量％
で、Ｃ ：０．２〜０．７％、Ｓｉ：０．２〜２．５
％、Ｍｎ：０．０５〜１．０％、Ｃｒ：０．２〜１．５
％、Ｍｏ：０．３〜１．５％で、かつその総量が、
Ｓｉ＋Ｍｎ＋Ｃｒ＋Ｍｏ≦５重量％
を満たし、残部がＦｅおよび不可避的不純物からなる鋼
材であって、５００℃〜Ａｅ1点以下の温度範囲で、焼
きもどしパラメーター：λが、
λ＝Ｔ（２０＋ｌｏｇｔ）≧１５８００
（式中、Ｔは温度（Ｋ）、ｔは時間（ｈ）を示す）とな
る条件で焼きもどし処理を施され、引張強さ（σB）が
１８００ＭＰａ以上であることを特徴としている。なお
この出願の発明では特にことわりのない限り、％表示は
全て重量％を示すものとする。That is, the high-strength mechanical structural steel provided by the invention of this application has a simple composition in which only Si, Mn, Cr, and Mo are alloy elements, and each of them has a weight percentage.
C: 0.2-0.7%, Si: 0.2-2.5
%, Mn: 0.05 to 1.0%, Cr: 0.2 to 1.5
%, Mo: 0.3 to 1.5%, the total amount of which satisfies Si + Mn + Cr + Mo ≦ 5% by weight, the balance being Fe and inevitable impurities, and a temperature of 500 ° C. to Ae 1 point or less. Within the range, the tempering parameter: λ is tempered under the condition that λ = T (20 + logt) ≧ 15800 (wherein T is temperature (K) and t is time (h)) The strength (σ B ) is characterized by being 1800 MPa or more. In the invention of this application, all percentages are by weight unless otherwise specified.
【００１５】この出願の発明の高強度機械構造用鋼は、
Ｍｏ添加による鋼材の２次硬化を積極的に利用するよう
にしている。そして、この出願の発明者らにより、Ｍｏ
鋼には、図１に□で例示したように、５５０〜６００℃
（８２３〜８７３Ｋ）付近にＭｏの添加による硬度の極
大が認められることが見出された。The high-strength mechanical structural steel of the invention of this application is
The secondary hardening of the steel material due to the addition of Mo is actively utilized. Then, the inventors of this application
For steel, as illustrated by □ in FIG. 1, 550 to 600 ° C.
It was found that the maximum hardness was observed due to the addition of Mo near (823-873K).
【００１６】さらに、このＭｏ鋼に対するＳｉ、Ｃｒ元
素の添加は、Ｍｏ添加鋼の焼きもどし硬さに以下のよう
な影響を及ぼすことが見出された。図１において、前述
の□は０．６％Ｃ−０．２％Ｍｎ−１％Ｍｏ鋼を、△は
１％Ｃｒ添加Ｍｏ鋼を、▲は２％Ｓｉ添加Ｍｏ鋼を、○
は２％Ｓｉ−１％Ｃｒ添加Ｍｏ鋼を示している。すなわ
ち、たとえば０．６％Ｃ−０．２％Ｍｎ−１％Ｍｏ鋼の
焼入れ硬さ（ａｓ−Ｑｕｅｎｃｈｅｄ）は、Ｓｉおよび
Ｃｒの添加に依らずいずれの場合でもＨｖ８４０程度で
ほぼ同じである。そして、Ｓｉの添加により３５０℃
（６２３Ｋ）以下の低温域で、Ｃｒの添加により４５０
℃（７２３Ｋ）以上の高温域で、焼きもどしによる軟化
が顕著に遅滞されるのである。さらにＳｉとＣｒの複合
添加は、５５０〜６００℃（８２３〜８７３Ｋ）の高温
域での焼きもどし後も１８００ＭＰａ超級の強度（Ｈｖ
５３０以上）を維持するのに有効であることが見出され
た。Further, it has been found that the addition of Si and Cr elements to this Mo steel has the following effects on the temper hardness of Mo-added steel. In FIG. 1, □ represents 0.6% C-0.2% Mn-1% Mo steel, Δ represents 1% Cr-added Mo steel, ▲ represents 2% Si-added Mo steel, and ○.
Shows 2% Si-1% Cr addition Mo steel. That is, for example, the quenching hardness (as-Quenched) of 0.6% C-0.2% Mn-1% Mo steel is almost the same at Hv840 regardless of the addition of Si and Cr. And by adding Si, 350 ℃
In the low temperature range below (623K), the addition of Cr causes 450
In the high temperature range above ℃ (723K), the softening due to tempering is significantly delayed. Furthermore, the combined addition of Si and Cr shows that after tempering in the high temperature range of 550 to 600 ° C. (823 to 873 K), the strength (Hv
530) and above) have been found effective.
【００１７】加えて、この出願の発明の高強度機械構造
用鋼における複合添加元素として選定されたＳｉおよび
Ｃｒは、たとえば、鉄中のＭｏ、ＣｒおよびＳｉ合金元
素の１時間あたりの拡散移動距離を例示した図２からわ
かるように、Ｓｉは４００℃（６７３Ｋ）以上で、Ｃｒ
は４５０℃（７２３Ｋ）以上で、Ｍｏは５５０℃（８２
３Ｋ）以上で格子拡散量が顕著になるという特性を示
す。すなわち、これらの合金元素の拡散は鋼材中で炭化
物の生成と成長とに密接に関係しており、換言すると、
炭化物の生成および成長はこれらの合金元素の拡散に律
速されることになる。従って、ＳｉおよびＣｒの添加
は、高温域における析出強化を促し、炭化物が均一かつ
微細に分散した組織を有する鋼材の実現にも寄与するこ
とがわかった。In addition, Si and Cr selected as the composite additive elements in the high-strength mechanical structural steel of the invention of the present application are, for example, the diffusion migration distance of Mo, Cr and Si alloy elements in iron per hour. As can be seen from FIG. 2 exemplifying the above, when Si is 400 ° C. (673 K) or higher,
Is 450 ° C (723K) or higher, and Mo is 550 ° C (82K).
The characteristic is that the lattice diffusion amount becomes remarkable at 3 K) or more. That is, the diffusion of these alloying elements is closely related to the formation and growth of carbides in the steel material, in other words,
The formation and growth of carbides will be limited by the diffusion of these alloying elements. Therefore, it was found that the addition of Si and Cr promotes precipitation strengthening in a high temperature region and contributes to the realization of a steel material having a structure in which carbides are uniformly and finely dispersed.
【００１８】これらの新たな知見を基に、各元素の含有
量についてさらに詳細に調査した結果、その含有量は以
下の範囲とすることが好適なものとして考慮することが
できる。
＜Ｃ＞ Ｃは炭化物を形成し、析出強化によって鋼の強
度を高める必須元素であり、その含有量は０．２〜０．
７％とする。Ｃが０．２％未満では炭化物の析出量が少
なくなってしまい、焼きもどしにより十分な強度が得ら
れないため好ましくない。一方、０．７％を超える場合
には、焼入れ時の焼き割れ感受性が増大すると共に靭性
の低下を招いてしまうために好ましくない。
＜Ｓｉ＞ Ｓｉは鋼の脱酸および強度上昇に必要不可欠
な合金元素であり、その含有量は０．２〜２．５％とす
る。とくにＳｉは、フェライト中に固溶して基地の強度
を高める作用が強い上に、セメンタイト粒にはほとんど
固溶せず、セメンタイトの生成を抑制し、低温域での焼
きもどしによる軟化を遅滞させる作用が強い元素であ
る。従って、脱酸剤として添加したもので鋼中に残るも
のも含め、他の合金元素とのバランスから含有量を０．
２％以上とする。また、過剰な添加は鋼と脆化させてし
まうため、その上限は２．５％とする。
＜Ｃｒ＞ Ｃｒは焼入れ性の向上に必要な合金元素であ
り、その含有量は０．２〜１．５％とする。Ｃｒはセメ
ンタイト中に固溶して高温域での焼きもどしによる軟化
を遅滞させる作用が強い元素である。従って、少なくと
も０．２％以上含有させる必要がある。好ましくは１％
以上を含有させるが、過剰になるとその効果が飽和する
と共に靭性が低下してしまうため、上限は１．５％とし
ている。
＜Ｍｎ＞ Ｍｎは鋼材中に存在するＳの害を阻止し、焼
入れ性を高めるために必要な合金元素であり、その含有
量は０．０５〜１．０量％とする。含有量が０．０５％
未満ではこの効果が少ないが、１％を超えて含有される
と靭性を劣化させるとともに、焼き戻し後の鋼材の水素
透過性を高め、その結果として遅れ破壊を起こしやすく
してしまう。したがって、Ｍｎ量は０．０５〜１．０％
とする。
＜Ｍｏ＞ Ｍｏは焼入れ性の向上に有効な元素であり、
拡散速度が遅く、比較的少量を添加することで、セメン
タイト中に固溶して高温域でのセメンタイトの成長を抑
制し、焼きもどしによる軟化を遅滞できる元素である。
しかしＭｏはセメンタイト中への固溶量が少なく、Ｆｅ
よりも炭化物形成能が強いという性質があるため、多量
に添加した場合には新しく別個の炭化物を形成し、鋼を
２次硬化させる効果をも得ることができる。それゆえ、
高温焼きもどしで鋼の高強度化を図るこの出願の発明に
おいて、Ｍｏの含有量は０．３％以上を必要とする。
１．５％以上となるとその効果は飽和し、また、過剰な
添加は経済性の観点から好ましくない。従って、Ｍｏ量
は０．３〜１．５％としている。またＭｏの代わりに、
Ｍｏと同様の特性を示すＷを用いることもできる。Based on these new findings, as a result of further detailed investigation of the content of each element, it can be considered that the content is preferably in the following range. <C> C is an essential element that forms carbides and enhances the strength of steel by precipitation strengthening, and the content thereof is 0.2 to 0.
7%. If C is less than 0.2%, the precipitation amount of carbides will be small and sufficient strength cannot be obtained by tempering, which is not preferable. On the other hand, if it exceeds 0.7%, the susceptibility to quench cracking during quenching increases and the toughness decreases, which is not preferable. <Si> Si is an alloy element essential for deoxidizing steel and increasing strength, and its content is 0.2 to 2.5%. In particular, Si has a strong action to form a solid solution in ferrite to enhance the strength of the matrix, and it hardly forms a solid solution in cementite grains, suppresses the formation of cementite, and delays softening due to tempering at low temperatures. It is an element with a strong action. Therefore, the content of the deoxidizing agent added to the steel is 0.10 from the balance with other alloy elements, including those added in the steel and remaining in the steel.
2% or more. Further, excessive addition causes embrittlement with steel, so the upper limit is made 2.5%. <Cr> Cr is an alloy element necessary for improving hardenability, and the content thereof is 0.2 to 1.5%. Cr is an element that has a strong action to form a solid solution in cementite and delay the softening due to tempering in a high temperature range. Therefore, it is necessary to contain at least 0.2% or more. Preferably 1%
The above content is included, but if it becomes excessive, the effect is saturated and the toughness decreases, so the upper limit is made 1.5%. <Mn> Mn is an alloy element necessary for preventing the damage of S existing in the steel material and improving the hardenability, and the content thereof is 0.05 to 1.0% by weight. Content is 0.05%
If it is less than 1%, this effect is small, but if it exceeds 1%, the toughness is deteriorated and the hydrogen permeability of the steel material after tempering is increased, and as a result, delayed fracture is likely to occur. Therefore, the Mn content is 0.05 to 1.0%
And <Mo> Mo is an element effective in improving hardenability,
It is an element that has a slow diffusion rate and, by adding a relatively small amount, forms a solid solution in cementite to suppress the growth of cementite in the high temperature range and delay the softening due to tempering.
However, Mo has a small solid solution amount in cementite,
Since it has a property of forming carbides stronger than the above, when added in a large amount, it is possible to form a new and separate carbide and also obtain the effect of secondarily hardening the steel. therefore,
In the invention of this application, which aims to increase the strength of steel by high temperature tempering, the content of Mo needs to be 0.3% or more.
If it is 1.5% or more, the effect is saturated, and excessive addition is not preferable from the economical viewpoint. Therefore, the amount of Mo is set to 0.3 to 1.5%. Also, instead of Mo,
It is also possible to use W that exhibits the same characteristics as Mo.
【００１９】さらに、上記の合金元素の総量は、経済
性、リサイクル性の観点から、Ｓｉ＋Ｍｎ＋Ｃｒ＋Ｍｏ
≦５を満足する単純組成であることが好ましい。Further, the total amount of the above alloying elements is Si + Mn + Cr + Mo from the viewpoint of economical efficiency and recyclability.
A simple composition that satisfies ≦ 5 is preferable.
【００２０】このような極めて限定された単純組成で、
炭化物が均一かつ微細に分散した焼き戻し組織を有し、
１８００ＭＰａ以上の強度レベルの鋼材に対し、この出
願の発明においては、５００℃以上かつＡｅ1点以下の
温度で、Ｔ（２０＋ｌｏｇＴ）≧１５８００の条件で焼
き戻し処理することで優れた耐遅れ破壊特性を付与する
ようにしている。ここで、前式中のＴは焼きもどし温度
（単位：Ｋ）を、ｔは焼きもどし時間（単位：ｈ）を示
している。この発明の高強度機械構造用鋼は、このよう
な条件で焼きもどし処理を施せばよく、従来のような複
雑な加工熱処理を必要としない。With such a very limited simple composition,
Has a tempered structure in which carbide is uniformly and finely dispersed,
In the invention of this application, in the invention of this application, for the steel material having a strength level of 1800 MPa or more, excellent delayed fracture resistance is obtained by tempering at a temperature of 500 ° C. or more and Ae 1 point or less under the condition of T (20 + logT) ≧ 15800 Is given. Here, T in the above equation represents the tempering temperature (unit: K), and t represents the tempering time (unit: h). The high-strength mechanical structural steel of the present invention may be tempered under such conditions and does not require complicated thermomechanical treatment as in the prior art.
【００２１】さらに、この出願の発明の高強度機械構造
用鋼は、焼入れ処理の前に鍛錬成形比で４以上の鍛造を
行うこと、より好適には１０以上、さらには５０以上の
鍛造を行うことが好ましい。このような処理を行うこと
で、鋼材に含まれる合金元素の偏析帯の幅を狭めること
ができ、偏析による機械的性質への悪影響が抑制され
て、さらに遅れ破壊特性を向上させることができる。こ
れによって、例えば、負荷応力を０．９σBとする遅れ
破壊試験において、遅れ破壊の発生する拡散性水素量の
限界値（Ｈｃ）を０．１ｐｐｍレベル、さらには０．２
ｐｐｍ、より好適には、０．４ｐｐｍ以上に高めること
ができる。Further, the high-strength mechanical structural steel of the invention of this application is forged by a wrought forming ratio of 4 or more, preferably 10 or more, more preferably 50 or more before quenching. It is preferable. By performing such a treatment, the width of the segregation zone of the alloy elements contained in the steel material can be narrowed, the adverse effect on the mechanical properties due to segregation can be suppressed, and the delayed fracture property can be further improved. As a result, for example, in a delayed fracture test with a load stress of 0.9σ B , the limit value (Hc) of the amount of diffusible hydrogen at which delayed fracture occurs is 0.1 ppm level, and further 0.2.
ppm, and more preferably 0.4 ppm or more.
【００２２】また、遅れ破壊特性をさらに向上させるた
めには、不純物としてのＰおよびＳの量をそれぞれ０．
０１％以下と、極力減らすことが望ましい。In order to further improve the delayed fracture characteristics, the amounts of P and S as impurities are set to 0.
It is desirable to reduce it to 01% or less as much as possible.
【００２３】このように、この出願の発明は、引張り強
さが１８００ＭＰａ以上で耐遅れ破壊に優れた高強度機
械構造用鋼を実現するものであって、しかもリサイクル
性を考慮した単純組成を有している。すなわち、この出
願の発明の高強度機械構造用鋼は、全く新しい合金設計
の指針を与えるものとなる。そしてこの発明の高強度機
械構造用鋼の実用化により、構造物や自動車材料の軽量
化や安全性が向上されることになり、社会的、経済的貢
献度は極めて高いものになると期待される。As described above, the invention of this application realizes a high-strength mechanical structural steel having a tensile strength of 1800 MPa or more and excellent in delayed fracture resistance, and has a simple composition in consideration of recyclability. is doing. That is, the high-strength mechanical structural steel of the invention of this application provides a completely new guideline for alloy design. It is expected that the practical use of the high-strength mechanical structural steel of the present invention will reduce the weight and safety of structures and automobile materials, and will make an extremely high social and economic contribution. .
【００２４】以下に実施例を示し、この発明の実施の形
態についてさらに詳しく説明する。The embodiments of the present invention will be described in more detail below with reference to examples.
【００２５】[0025]
【実施例】（実施例１）Ａ：引張り強さ
表１に示したとおりの組成を有し、各種の焼きもどし処
理を施したＳｉ−Ｃｒ−Ｍｎ−Ｍｏ鋼（鋼１〜鋼７）の
丸棒試験片について引張り試験を行い、その結果を併せ
て示した。Examples (Example 1) A: Tensile strength of Si-Cr-Mn-Mo steels (steels 1 to 7) having the compositions shown in Table 1 and subjected to various tempering treatments A tensile test was performed on the round bar test piece, and the results are also shown.
【００２６】なお、鋼１〜鋼７はいずれもＳｉ＋Ｃｒ＋
Ｍｎ＋Ｍｏ≦５重量％を満たしているが、鋼３〜７はこ
の出願の発明の鋼材の組成から外れている。なお、鋼４
は従来鋼のＳＵＰ１２鋼に、鋼５はＳＣＭ４４０鋼に相
当している。Steel 1 to Steel 7 are all Si + Cr +
Although Mn + Mo ≦ 5 wt% is satisfied, Steels 3 to 7 are out of the composition of the steel material of the invention of this application. Steel 4
Corresponds to the conventional steel SUP12 steel, and steel 5 corresponds to the SCM440 steel.
【００２７】[0027]
【表１】 [Table 1]
【００２８】表中のλは焼きもどしパラメータであっ
て、焼きもどし温度Ｔ（Ｋ）および焼きもどし時間ｔ
（ｈ）より、λ＝Ｔ（２０＋ｌｏｇｔ）で求められた値
である。Ｈｖはビッカース硬さを、σBは引張強さ（Ｍ
Ｐａ）を示している。また、評価欄における、○は、前
記λ≧１５８００かつσB≧１８００を満たす鋼材を、
×は満たさない鋼材を示している。In the table, λ is a tempering parameter, which is the tempering temperature T (K) and the tempering time t.
From (h), it is a value obtained by λ = T (20 + logt). Hv is Vickers hardness, σ B is tensile strength (M
Pa) is shown. In the evaluation column, ◯ indicates a steel material satisfying the above λ ≧ 15800 and σ B ≧ 1800,
X shows the steel material which is not satisfied.
【００２９】表１から、この出願の発明の単純組成を有
する鋼１、鋼２に対し、５００℃〜Ａｅ1点以下の高温
焼きもどしをλ≧１５８００の条件で施すことで、σB
≧１８００を満たす鋼材が得られることが示された。From Table 1, it can be seen that by subjecting Steel 1 and Steel 2 having the simple composition of the invention of this application to high temperature tempering at 500 ° C. to Ae 1 point or less under the condition of λ ≧ 15800, σ B
It was shown that a steel material satisfying ≧ 1800 was obtained.
【００３０】一方、従来鋼の鋼４（ＳＵＰ１２鋼）およ
び鋼５（ＳＣＭ４４０鋼）に５００℃以上の高温焼きも
どし処理を施しても、σB≧１８００を達成することは
できない。また、この出願の発明の鋼材の組成よりもＭ
ｏ量の少ない鋼３、Ｓｉ量の少ない鋼６、ＳｉおよびＣ
ｒ量の少ない鋼７については、５００℃以上の高温焼き
もどし処理によりσB≧１８００を達成することはでき
ない。従って、５００℃以上の高温焼きもどし処理によ
りσB≧１８００を示すこの出願の発明の鋼材を得るに
は、適切な量のＳｉ，Ｃｒ，Ｍｏの複合添加が必要であ
ることが示された。Ｂ：遅れ破壊特性
遅れ破壊特性を、前記の表１の備考欄に※印で示した鋼
材について評価した。評価方法は、応力集中係数４．９
あるいは３．６の切欠き試験片を用意し、負荷荷重を上
記Ａで測定した引張強さの０．９倍とする定荷重試験法
により行った。On the other hand, even if the conventional steels, Steel 4 (SUP12 steel) and Steel 5 (SCM440 steel), are subjected to a high temperature tempering treatment at 500 ° C. or higher, σ B ≧ 1800 cannot be achieved. In addition, the composition of steel of the invention of this application is M
Steel 3 with a small amount of o, Steel 6 with a small amount of Si, Si and C
For steel 7 with a small amount of r, σ B ≧ 1800 cannot be achieved by high temperature tempering treatment at 500 ° C. or higher. Therefore, in order to obtain the steel material of the invention of this application exhibiting σ B ≧ 1800 by the high temperature tempering treatment of 500 ° C. or more, it is necessary to add an appropriate amount of Si, Cr and Mo in combination. B: Delayed Fracture Property The delayed fracture property was evaluated for the steel materials indicated by * in the remarks column of Table 1 above. The evaluation method is a stress concentration factor of 4.9.
Alternatively, a notch test piece of 3.6 was prepared, and a constant load test method was performed in which the applied load was 0.9 times the tensile strength measured in A above.
【００３１】なお、遅れ破壊試験に際し、陰極チャージ
によって試験片中の平均水素量を変化させ、Ｃｄメッキ
を施すことによって、試験片中の水素が散逸しないよう
な状態にした上で荷重を負荷し、試験片が破断するまで
の時間を測定した。また、３００℃までに放出される水
素量を鋼中の拡散性水素量と定義して、この拡散性水素
量を四重極質量分析計を用いた昇温分析法により測定し
た。この昇温分析は、試験片からＣｄメッキを除去した
後に行った。In the delayed fracture test, the average amount of hydrogen in the test piece was changed by cathode charging, and Cd plating was performed so that the hydrogen in the test piece did not dissipate and a load was applied. The time until the test piece broke was measured. Further, the amount of hydrogen released up to 300 ° C. was defined as the amount of diffusible hydrogen in steel, and this amount of diffusible hydrogen was measured by the temperature rising analysis method using a quadrupole mass spectrometer. This temperature increase analysis was performed after removing the Cd plating from the test piece.
【００３２】表２に遅れ破壊試験の結果を示した。表中
の定荷重試験の結果は、荷重の負荷１００時間後に試験
片が破断したか破断しなかった（未破断）かを示してい
る。また、備考欄に示した鋼材（ａ）（ｂ）（ｃ）につ
いての遅れ破壊特性を図３に示した。Table 2 shows the results of the delayed fracture test. The result of the constant load test in the table indicates whether the test piece broke or did not break (unbroken) 100 hours after the load was applied. Further, the delayed fracture characteristics for the steel materials (a), (b) and (c) shown in the remarks column are shown in FIG.
【００３３】[0033]
【表２】 [Table 2]
【００３４】表２および図３より、鋼材中の拡散性水素
量が少ないほど遅れ破壊が発生しにくいことがわかる。
そして、遅れ破壊が発生する拡散性水素量の限界値（Ｈ
ｃ）は、鋼材（ａ）：１％Ｍｏ、鋼材（ｂ）：０．５％
Ｍｏでそれぞれ０．４ｐｐｍ、０．２１ｐｐｍであり、
鋼材（ｃ）：０％Ｍｏの０．０５ｐｐｍよりも４倍以上
高いことがわかった。この結果から、Ｍｏの添加が１８
００ＭＰａ強度レベルの耐遅れ破壊特性の向上に有効で
あることが示された。From Table 2 and FIG. 3, it is understood that delayed fracture is less likely to occur as the amount of diffusible hydrogen in the steel material is smaller.
Then, the limit value of the diffusible hydrogen amount (H
c) is steel (a): 1% Mo, steel (b): 0.5%
Mo is 0.4 ppm and 0.21 ppm,
Steel material (c): It was found to be 4 times or more higher than 0.05 ppm of 0% Mo. From this result, the addition of Mo is 18
It was shown to be effective in improving the delayed fracture resistance at the 00 MPa strength level.
【００３５】また、鋼４（ＳＵＰ１２相当）のＨｃも
０．０４ｐｐｍときわめて低い値であり、耐遅れ破壊特
性が劣ることが示された。一方の、鋼５（ＳＣＭ４４０
相当）のＨｃは、応力集中係数が３．６、引張強さが１
６００ＭＰａレベルの鋼材で０．１３ｐｐｍ、引張強さ
１８００ＭＰａ以上のレベルになると０．１ｐｐｍ未満
と、比較的高めではあるものの、鋼１および鋼２に比較
すると１／２以下の低い値となることが示された。Further, Hc of Steel 4 (equivalent to SUP12) was 0.04 ppm, which was an extremely low value, indicating that the delayed fracture resistance was inferior. On the other hand, steel 5 (SCM440
Equivalent) Hc has a stress concentration factor of 3.6 and a tensile strength of 1
At a level of 600 MPa steel, 0.13 ppm, and at a tensile strength of 1800 MPa or higher, less than 0.1 ppm, which is a relatively high value, but is as low as 1/2 or less compared to Steel 1 and Steel 2. Was shown.
【００３６】以上のことから、Ｓｉ、Ｃｒ、Ｍｎ、Ｍｏ
（Ｓｉ＋Ｃｒ＋Ｍｎ＋Ｍｏ≦５重量％）の単純合金組成
でも、これらを適切な量だけ複合添加し、かつ５００℃
以上で高温焼きもどしを施した鋼は、引張強さが１８０
０ＭＰａ以上の強度レベルでも優れた耐遅れ破壊特性を
示すことが示された。
（実施例２）０．６Ｃ−２Ｓｉ−１Ｃｒ−０．２Ｍｎ−
１Ｍｏ鋼について、焼入れ処理前に鍛錬成形比が４の熱
間鍛造を施した鋼材と、鍛錬成形比が５０の鋼材とを用
意し、遅れ破壊特性を評価した。その結果を図４に示し
た。From the above, Si, Cr, Mn, Mo
Even with a simple alloy composition of (Si + Cr + Mn + Mo ≦ 5% by weight), an appropriate amount of them is added in combination and the temperature is 500 ° C.
The high-temperature tempered steel has a tensile strength of 180.
It was shown that excellent delayed fracture resistance is exhibited even at a strength level of 0 MPa or more. (Example 2) 0.6C-2Si-1Cr-0.2Mn-
For 1Mo steel, a steel material that was hot forged with a wrought forming ratio of 4 before quenching and a steel material with a wrought forming ratio of 50 were prepared, and the delayed fracture characteristics were evaluated. The results are shown in Fig. 4.
【００３７】熱間鍛錬成形比が４の鋼では、遅れ破壊が
発生する拡散性水素量の限界値（Ｈｃ）が０．２ｐｐｍ
であるのに対し、鍛錬成形比が５０の鋼では０．４ｐｐ
ｍと２倍程度高くなることがわかった。この結果は、鍛
造が耐遅れ破壊特性の向上に有効であることを示してい
る。In the steel having the hot forging ratio of 4, the limit value (Hc) of the diffusible hydrogen amount at which delayed fracture occurs is 0.2 ppm.
On the other hand, for steel with a wrought forming ratio of 50, 0.4 pp
It was found that it was about twice as high as m. This result indicates that forging is effective in improving delayed fracture resistance.
【００３８】もちろん、この発明は以上の例に限定され
るものではなく、細部については様々な態様が可能であ
ることは言うまでもない。Of course, the present invention is not limited to the above examples, and it goes without saying that various details can be made.
【００３９】[0039]
【発明の効果】以上詳しく説明した通り、この発明によ
って、単純な組成からなるためにリサイクル性に優れ、
なおかつ複雑な加工熱処理を必要としない、耐遅れ破壊
特性に優れた新規な高強度機械構造用鋼が提供される。As described in detail above, according to the present invention, since it has a simple composition, it has excellent recyclability,
Further, a novel high-strength mechanical structural steel excellent in delayed fracture resistance that does not require complicated thermomechanical treatment is provided.
【図１】０．６％Ｃ−０．２％Ｍｎ−１％Ｍｏ鋼の焼き
もどし硬さに及ぼすＳｉ、Ｃｒ添加の影響を例示した図
である。図中のマーカーの、□はＳｉ、Ｃｒ添加なしの
０．６％Ｃ−０．２％Ｍｎ−１％Ｍｏ鋼を、△は１％Ｃ
ｒ添加を、▲は２％Ｓｉ添加を、○は２％Ｓｉ−１％Ｃ
ｒ添加を示している。FIG. 1 is a diagram exemplifying an effect of addition of Si and Cr on a temper hardness of 0.6% C-0.2% Mn-1% Mo steel. In the markers in the figure, □ is 0.6% C-0.2% Mn-1% Mo steel without addition of Si and Cr, and Δ is 1% C.
r addition, ▲ 2% Si addition, ○ 2% Si-1% C
r addition is shown.
【図２】鉄材における各合金元素の１時間あたりの拡散
移動距離を例示した図である。FIG. 2 is a diagram exemplifying a diffusion movement distance of each alloy element in an iron material per hour.
【図３】実施例における鋼材（ａ）（ｂ）（ｃ）につい
ての遅れ破壊特性を例示した図である。FIG. 3 is a diagram exemplifying delayed fracture characteristics for steel materials (a), (b), and (c) in an example.
【図４】鍛錬成形比と遅れ破壊特性の関係を例示した図
である。FIG. 4 is a diagram illustrating a relationship between a wrought forming ratio and a delayed fracture characteristic.
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4K032 AA05 AA06 AA11 AA12 AA16 AA19 AA20 AA31 AA32 AA37 CB00 CH04 ─────────────────────────────────────────────────── ─── Continued front page F term (reference) 4K032 AA05 AA06 AA11 AA12 AA16 AA19 AA20 AA31 AA32 AA37 CB00 CH04
Claims (4)
材であって、５００℃〜Ａｅ1点以下の温度範囲で、焼
きもどしパラメーター：λが、 λ＝Ｔ（２０＋ｌｏｇｔ）≧１５８００ （式中、Ｔは温度（Ｋ）、ｔは時間（ｈ）を示す）とな
る条件で焼きもどし処理が施され、引張強さが１８００
ＭＰａ以上であることを特徴とする高強度機械構造用
鋼。1. The composition is% by weight, C: 0.2 to 0.7%, Si: 0.2 to 2.5%, Mn: 0.05 to 1.0%, Cr: 0.2. ~ 1.5%, Mo: 0.3-1.5%, the total amount of alloying elements satisfies Si + Mn + Cr + Mo ≤ 5% by weight, the balance is Fe and inevitable impurities steel material, 500 ℃ ~ Ae Tempering parameter: λ in the temperature range of 1 point or less, λ = T (20 + logt) ≧ 15800 (where T represents temperature (K) and t represents time (h)) Treated, tensile strength 1800
Steel for high-strength mechanical structures characterized by having a pressure of at least MPa.
の鍛造を施されていることを特徴とする請求項１記載の
高強度機械構造用鋼。2. The high-strength machine structural steel according to claim 1, which is forged with a wrought forming ratio of 4 or more before the quenching treatment.
０１重量％以下であることを特徴とする請求項１または
２記載の高強度機械構造用鋼。3. The content of P and S as impurities is 0.
The high-strength mechanical structural steel according to claim 1 or 2, wherein the content is 01% by weight or less.
％含まれていることを特徴とする請求項１ないし３いず
れかに記載の高強度機械構造用鋼。4. The high-strength mechanical structural steel according to any one of claims 1 to 3, wherein W is contained in an amount of 0.3 to 1.5% by weight instead of Mo.
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| CN106795598A (en) * | 2014-08-29 | 2017-05-31 | 日产自动车株式会社 | High-strength bolt steel and high-strength bolt |
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| JP5334769B2 (en) * | 2009-09-10 | 2013-11-06 | 独立行政法人物質・材料研究機構 | High strength bolt |
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| CN106795598A (en) * | 2014-08-29 | 2017-05-31 | 日产自动车株式会社 | High-strength bolt steel and high-strength bolt |
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| CN106350748A (en) * | 2016-08-31 | 2017-01-25 | 云南德胜钢铁有限公司 | Slag fetching rake and machining process thereof |
| RU2779102C1 (en) * | 2021-11-17 | 2022-08-31 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Российский государственный аграрный университет - МСХА имени К.А. Тимирязева" (ФГБОУ ВО РГАУ - МСХА имени К.А. Тимирязева) | Method for producing high-strength chromium-molybdenum steel |
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