JPH0222140B2 - - Google Patents
Info
- Publication number
- JPH0222140B2 JPH0222140B2 JP14879181A JP14879181A JPH0222140B2 JP H0222140 B2 JPH0222140 B2 JP H0222140B2 JP 14879181 A JP14879181 A JP 14879181A JP 14879181 A JP14879181 A JP 14879181A JP H0222140 B2 JPH0222140 B2 JP H0222140B2
- Authority
- JP
- Japan
- Prior art keywords
- strength
- steel
- toughness
- tempered
- 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
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 34
- 239000010959 steel Substances 0.000 claims description 34
- 239000012535 impurity Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000005496 tempering Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
本発明は、非調質高強度靭性鋼に関し、特に本
発明は、機械構造用の非調質高強度高靭性鋼に関
するものである。
自動車、建設機械等の部品として広く用いられ
ている機械構造用炭素鋼、合金鋼は通常、鍛造、
圧延などの熱間加工後、焼ならしあるいは焼入れ
焼もどし処理を行つて使用されている。このよう
な焼ならし、焼入れ焼もどしなどの調質処理は、
結晶粒を微細にし必要な強度靭性を確保するため
に重要である。しかし、最近、省エネルギーの観
点から、これら熱処理工程の省略が可能であれば
工業的利益は大であると考えられる。このような
意味から熱間加工のままで使用することができる
非調質鋼の開発が要望されている。
本発明は、上記従来要望されていた熱間加工の
ままで使用することができる非調質高強度靭性鋼
を提供することを目的とするものであり、特許請
求の範囲記載の鋼を提供することによつて前記目
的を達成することができる。すなわち本発明は、
C0.27超え〜0.55％、Si0.14超え〜0.60％、Mn1.2
超え〜2.5％、P0.02％以下、S0.05％以下、
Al0.005〜0.05％、V0.08〜0.15％、N0.002〜0.008
％未満を含み、残部Feと不可避的不純物よりな
り熱間加工のまま使用することを特徴とする非調
質高強度靭性鋼に関するものである。
次に本発明を詳細に説明する。
焼入れ焼もどし処理は強度が高く微細な組織を
生成させ、さらに炭（窒）化物の微細分散を可能
にし、鋼材に強靭性を付与する処理である。しか
し、熱間加工のまま使用する非調質鋼では、高温
加熱高温仕上による加工後の冷却速度が遅いこと
もあり、組織が粗大であり、強度靭性ともに低い
という欠点があつた。そこで、本発明者らは、こ
のような非調質鋼の欠点を補うべく種々の検討を
行つた。
本発明者らは、Ｖの析出硬化およびMnの母相
強化を併せ利用することにより、調質処理材と同
等以上の強度を有し、しかも高靭化を達成するこ
とができることを新規に知見して本発明を完成し
た。
ところで、Ｖを添加し、高温から冷却中に析出
する炭（窒）化物の析出硬化を利用し強度上昇を
計る手法はすでに非調質低炭素低合金高張力鋼で
利用されている。母相と、整合性を有した析出物
の微細分散が強度増加と密接に関係することが前
記手法において利用されているのである。しか
し、Ｖを多量に添加すると、強度増加は著しい
が、靭性は逆に劣化するようになる。このような
炭（窒）化物形成元素を中炭素鋼に含有させて非
調質高強度鋼として利用することは引張強度の点
のみについてみると非常に容易なことである。し
かし従来使用されている調質材の代替として上記
非調質材を用いることは靭性と降伏強さが低く、
また降伏比（降伏強さ／引張強さ）も低いという
欠点があるため実用することはできなかつた。
本発明者らは比較的多量のＶを添加し、さらに
Mnを添加し、析出硬化に加えて、母相の固溶硬
化により降伏強さの増加を試みた。その結果、第
１図に示すごとく降伏強さの増加とともに、衝撃
値が増加することを見い出した。しかしＶの多量
添加のみでは、衝撃値は強度とともに低減する。
かかる本発明者らの試みにより衝撃値が増加する
理由はMnとＶの多量添加の相互作用によるもの
と考えられる。すなわち、粒内フエライト形成の
促進と微細フエライト＋パーライト組織とするた
め、Mnによる変態点の低下と共にフエライトの
形成を促進するＶの多量添加が必要条件である。
本発明の主旨は、強度増加にかかわらず、靭性
の向上が得られる鋼を提供することであり、例え
ば第２図に示すように0.09Vを含有し、Mn量を
変化させてゆくと、1.0％以上で著しい衝撃値の
増加がみられ、1.5％Mn付近で飽和する。2.5％
Mn以上は靭性の劣化が著しい。また、この範囲
であれば、通常使用されるもつともおそい冷却条
件（10℃／min）も0.45％Ｃで降伏強さ50Kgｆ／
mm2以上が得られている。0.45％Ｃの焼入れ焼もど
し処理材（25φ）の降伏強さは50Kgｆ／mm2以上で
あるから、本発明鋼は焼入れ焼もどし処理材の代
替品として十分利用することができることが判
る。
本発明は、このような知見をもとに構成された
ものであり、本発明の鋼は熱間加工のまま使用
し、従来の調質処理構造用鋼とほぼ、同等の強度
と靭性を有する鋼である。
つぎに本発明鋼の成分組成を限定する理由を説
明する。
Ｃは強度とくに表面硬さを得るために0.27％超
えが必要であり、0.55％を超えると硬さが高くな
りすぎ靭性が害されるので、Ｃは0.27超え〜0.55
の範囲内にする必要がある。
Siは製鋼の脱酸剤および強度確保のため必要な
元素であり強度確保上0.14超えの必要があり、一
方0.60％を超えると靭性が劣化するのでSiは0.14
超え〜0.60％の範囲内にする必要がある。
MnはＶとともに本発明の主要元素で靭性向上
のための元素であり、1.2％以下では靭性の著し
い向上が得られず、一方2.5％を超えると靭性が
かえつて劣化するのでMnは1.2超え〜2.5％の範
囲内にする必要がある。
Ｐは鋼の材質を脆化させる元素であるので靭性
を確保するためには0.020％以下にする必要があ
り、0.015％以下のときさらによい結果が得られ
る。
Ｓは靭性を劣化させるが、一方切削性を向上さ
せる元素であるので機械構造用鋼としてはＳはあ
る程度含有されることが好ましいが、靭性も重視
する点からＳは0.05％以下にする必要がある。
Alは脱酸剤として添加するが、一方Alは鋼中
に金属Alとして残存するとＮ結合してAlNとな
り、結晶粒の微細化あるいは粗大化を左右する作
用を有する元素であり、Alが0.005％より少ない
と前記結晶粒を微細化する作用が少なく、一方
0.05％より多いと逆に結晶粒の粗大化を促進する
のでAlは0.005〜0.05％の範囲内にする必要があ
る。
Ｖは強度靭性確保の主要元素であり、0.08％以
下では調質材の代替のための強度確保が困難であ
り、粒内フエライトの形成の度合も少なく靭性の
改善が少ない。また、0.15％を超えると強度増加
が著しく靭性も劣化するのでＶは0.08〜0.15％の
範囲内にする必要がある。
ＮはAlと共存し結晶粒を微細化する作用を有
する元素であり、0.0020％より少ないと前記微細
化の作用が少なく、一方0.0080％上になると機械
的特性がかえつて劣化するのでＮは0.0020〜
0.0080％未満の範囲内にする必要がある。
次に本発明を実施例について説明する。
実施例
1250℃に加熱して圧延により作製した50mm直径
の棒鋼の熱間加工のままの機械的性質と成分組成
を第１表に示す。
The present invention relates to a non-tempered high-strength, high-toughness steel, and particularly the present invention relates to a non-tempered high-strength, high-toughness steel for mechanical structures. Carbon steel and alloy steel for machine structures, which are widely used as parts for automobiles, construction machinery, etc., are usually forged,
After hot working such as rolling, it is used after being normalized or quenched and tempered. Such tempering treatments such as normalizing, quenching and tempering are
This is important for making crystal grains finer and ensuring the necessary strength and toughness. However, recently, from the viewpoint of energy saving, it has been considered that there would be great industrial benefits if these heat treatment steps could be omitted. In this sense, there is a demand for the development of non-tempered steel that can be used as is after hot working. The object of the present invention is to provide a non-tempered high-strength toughness steel that can be used as it is after hot working, which has been desired in the past, and provides the steel described in the claims. By this, the above object can be achieved. That is, the present invention
Over C0.27~0.55%, Over Si0.14~0.60%, Mn1.2
Exceed ~2.5%, P0.02% or less, S0.05% or less,
Al0.005~0.05%, V0.08~0.15%, N0.002~0.008
The present invention relates to a non-tempered, high-strength, tough steel that is characterized in that it contains less than % of Fe and the remainder is Fe and unavoidable impurities, and is used as is after hot working. Next, the present invention will be explained in detail. Quenching and tempering is a process that generates a fine structure with high strength, and also enables fine dispersion of carbon(nitride), thereby imparting toughness to the steel material. However, non-tempered steel used as hot-worked has the drawback of having a coarse structure and low strength and toughness, partly because the cooling rate after processing due to high-temperature heating and high-temperature finishing is slow. Therefore, the present inventors conducted various studies in order to compensate for such drawbacks of non-tempered steel. The present inventors have newly found that by combining the precipitation hardening of V and the matrix strengthening of Mn, it is possible to achieve strength equal to or higher than that of heat-treated materials and high toughness. The present invention was completed. By the way, a method of increasing strength by adding V and utilizing precipitation hardening of carbon(nitride) which precipitates during cooling from high temperature has already been used in non-tempered low carbon low alloy high tensile strength steel. The fact that the fine dispersion of precipitates that are consistent with the parent phase is closely related to the increase in strength is utilized in the above method. However, when a large amount of V is added, the strength increases significantly, but the toughness deteriorates. It is very easy to incorporate such carbon (nit)-forming elements into medium carbon steel and use it as a non-thermal high strength steel, considering only the tensile strength. However, using the above-mentioned non-tempered materials as a substitute for the conventionally used tempered materials has low toughness and yield strength.
Furthermore, the yield ratio (yield strength/tensile strength) was low, which made it impossible to put it into practical use. The present inventors added a relatively large amount of V, and further
An attempt was made to increase the yield strength by adding Mn and solid solution hardening of the matrix in addition to precipitation hardening. As a result, as shown in FIG. 1, it was found that as the yield strength increased, the impact value increased. However, if only a large amount of V is added, the impact value decreases along with the strength.
The reason why the impact value increases as a result of the attempts made by the present inventors is considered to be due to the interaction between the addition of large amounts of Mn and V. That is, in order to promote the formation of intragranular ferrite and create a fine ferrite + pearlite structure, it is necessary to lower the transformation point by Mn and to add a large amount of V, which promotes the formation of ferrite. The gist of the present invention is to provide a steel that can improve toughness regardless of the increase in strength. % or more, a significant increase in impact value is seen, and it becomes saturated around 1.5% Mn. 2.5%
Above Mn, the toughness deteriorates significantly. In addition, within this range, the normally used very slow cooling conditions (10°C/min) can also yield a yield strength of 50 kgf/min at 0.45%C.
mm 2 or more has been obtained. Since the yield strength of the 0.45% C quenched and tempered material (25φ) is 50 Kgf/mm 2 or more, it can be seen that the steel of the present invention can be fully used as a substitute for the quenched and tempered material. The present invention was constructed based on such knowledge, and the steel of the present invention can be used as hot-worked and has almost the same strength and toughness as conventional heat-treated structural steel. It is steel. Next, the reason for limiting the composition of the steel of the present invention will be explained. C exceeds 0.27% to obtain strength, especially surface hardness, and if it exceeds 0.55%, the hardness becomes too high and toughness is impaired, so C exceeds 0.27 to 0.55.
Must be within the range. Si is a necessary element for steelmaking as a deoxidizing agent and for ensuring strength, and to ensure strength, it must exceed 0.14%.On the other hand, if it exceeds 0.60%, toughness will deteriorate, so Si should be 0.14%.
Must be within the range of 0.60%. Mn is a main element of the present invention along with V and is an element for improving toughness. If it is less than 1.2%, no significant improvement in toughness can be obtained, while if it exceeds 2.5%, the toughness will deteriorate instead, so Mn should be more than 1.2 ~ Must be within 2.5%. Since P is an element that embrittles the material of steel, it must be kept at 0.020% or less in order to ensure toughness, and even better results are obtained when it is 0.015% or less. S deteriorates toughness, but on the other hand, it is an element that improves machinability, so it is preferable for steel for machine structures to contain S to some extent, but since toughness is also important, S should be kept at 0.05% or less. be. Al is added as a deoxidizing agent, but on the other hand, when Al remains as metallic Al in steel, it bonds with N to become AlN, which is an element that affects the refinement or coarsening of crystal grains, and Al is an element with 0.005% If the amount is less, the effect of refining the crystal grains will be small; on the other hand,
If it exceeds 0.05%, coarsening of crystal grains will be promoted, so Al should be in the range of 0.005 to 0.05%. V is a main element for ensuring strength and toughness, and if it is less than 0.08%, it is difficult to ensure the strength to replace tempered materials, and the degree of formation of intragranular ferrite is small, resulting in little improvement in toughness. Further, if it exceeds 0.15%, the strength increases significantly and the toughness deteriorates, so V needs to be within the range of 0.08 to 0.15%. N is an element that coexists with Al and has the effect of refining crystal grains, and if it is less than 0.0020%, the refining effect will be small, while if it exceeds 0.0080%, the mechanical properties will deteriorate, so N is 0.0020%. ~
Must be within the range of less than 0.0080%. Next, the present invention will be explained with reference to examples. Example Table 1 shows the mechanical properties and composition of a 50 mm diameter steel bar as hot worked, which was produced by heating to 1250°C and rolling.
【表】【table】
【表】
なお同表中に記載の鋼は何れも転炉−連鋳−圧
延の諸工程を経て作製したものである。
鋼１〜３は本発明の範囲の鋼であり、鋼７，８
は比較鋼であり鋼９は従来の焼入焼もどし処理を
行つた鋼（50φ）棒鋼）である。
本発明鋼１〜３は比較鋼７，８にくらべ強度、
衝撃値ともに高く、強度靭性ともにすぐれている
ことがわかる。
また従来鋼９と比較しても十分な性能を有して
いる。
以上本発明により従来使用されている調質鋼に
優るとも劣らない高強度で高靭性の非調質鋼を提
供することができる。[Table] All of the steels listed in the table were produced through the various processes of converter, continuous casting, and rolling. Steels 1 to 3 are steels within the scope of the present invention, and Steels 7 and 8
is a comparative steel, and Steel 9 is a steel bar (50φ) that has been subjected to conventional quenching and tempering treatment. Invention steels 1 to 3 have higher strength than comparative steels 7 and 8.
It can be seen that both impact value is high and both strength and toughness are excellent. Furthermore, it has sufficient performance compared to conventional steel 9. As described above, according to the present invention, it is possible to provide a non-tempered steel with high strength and high toughness that is at least superior to conventionally used tempered steels.
第１図は鋼の降伏強さと衝撃値との関係を示す
図、第２図はMn含有量と降伏強さ、衝撃値との
関係を示す図である。
FIG. 1 is a diagram showing the relationship between yield strength and impact value of steel, and FIG. 2 is a diagram showing the relationship between Mn content, yield strength, and impact value.
Claims (1)
Mn1.2超え〜2.5％、P0.012％以下、S0.05％以下、
Al0.005〜0.05％、V0.08〜0.15％、N0.002〜0.008
％未満を含み、残部Feと不可避的不純物よりな
り熱間加工のまま使用することを特徴とする非調
質高強度靭性鋼。1 Over C0.27~0.55%, over Si0.14~0.60%,
Mn over 1.2 ~ 2.5%, P 0.012% or less, S 0.05% or less,
Al0.005~0.05%, V0.08~0.15%, N0.002~0.008
A non-tempered, high-strength, tough steel that is characterized by containing less than % Fe and the remainder being Fe and unavoidable impurities, and is characterized by being used as hot-worked.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14879181A JPS5852458A (en) | 1981-09-22 | 1981-09-22 | Nonquenched and tempered steel with high strength and toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14879181A JPS5852458A (en) | 1981-09-22 | 1981-09-22 | Nonquenched and tempered steel with high strength and toughness |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27239185A Division JPS61235541A (en) | 1985-12-05 | 1985-12-05 | Untempered hot-worked steel stock having high strength and toughness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5852458A JPS5852458A (en) | 1983-03-28 |
| JPH0222140B2 true JPH0222140B2 (en) | 1990-05-17 |
Family
ID=15460769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14879181A Granted JPS5852458A (en) | 1981-09-22 | 1981-09-22 | Nonquenched and tempered steel with high strength and toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5852458A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62199750A (en) * | 1986-02-27 | 1987-09-03 | Nippon Steel Corp | Unrefined steel bar having superior toughness and its manufacture |
| JPS6379940A (en) * | 1986-07-05 | 1988-04-09 | テイツセン・エ−デルシユタ−ルヴエルケ・アクチエンゲゼルシヤフト | Micro-alloyed structural steel |
| JPH0674482B2 (en) * | 1987-02-16 | 1994-09-21 | 株式会社神戸製鋼所 | Non-heat treated steel for hot forging with excellent fatigue resistance and machinability |
| JPH01290751A (en) * | 1988-05-19 | 1989-11-22 | Topy Ind Ltd | High-strength non-heattreated steel bar |
| US5221373A (en) * | 1989-06-09 | 1993-06-22 | Thyssen Edelstahlwerke Ag | Internal combustion engine valve composed of precipitation hardening ferritic-pearlitic steel |
| CN103589970B (en) * | 2013-10-24 | 2016-03-30 | 南京钢铁股份有限公司 | The excellent Materials And Manufacturing Processes of Micro Alloying axial workpiece |
| CN104593671B (en) * | 2015-02-28 | 2017-04-19 | 南京工程学院 | Application of high-strength tough non-quenched and tempered steel in compound forge forming |
-
1981
- 1981-09-22 JP JP14879181A patent/JPS5852458A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5852458A (en) | 1983-03-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2341667C (en) | Cold workable steel bar or wire and process | |
| JP3139876B2 (en) | Method of manufacturing non-heat treated steel for hot forging and non-heat treated hot forged product, and non-heat treated hot forged product | |
| JPH0741856A (en) | Manufacturing method of high strength steel pipe with excellent resistance to sulfide stress corrosion cracking | |
| JPH039168B2 (en) | ||
| JPH0222140B2 (en) | ||
| US20240052467A1 (en) | High-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, heat-treated component, and method for manufacturing same | |
| JP3228986B2 (en) | Manufacturing method of high strength steel sheet | |
| JPH01176055A (en) | Non-heat treated steel for hot forging having excellent machinability | |
| JPH0159333B2 (en) | ||
| JPS6156235A (en) | Manufacturing method of high toughness non-thermal steel | |
| JPH026828B2 (en) | ||
| JP3098366B2 (en) | Air-cooled martensitic non-heat treated steel for tough hot forging | |
| JPH0425343B2 (en) | ||
| JPS589816B2 (en) | Manufacturing method of non-thermal rolled steel bar | |
| JPH0813028A (en) | Production of precipitation hardening steel material having high tensile strength and high toughness | |
| JP3543581B2 (en) | Ferrite / pearlite non-heat treated steel | |
| JPH0152461B2 (en) | ||
| JPS6137333B2 (en) | ||
| JPH07310118A (en) | Method for manufacturing case hardening steel suitable for cold working | |
| JPH0219175B2 (en) | ||
| JP3042574B2 (en) | Hot forged product having high fatigue strength and method of manufacturing the same | |
| JPH0530883B2 (en) | ||
| JP2767254B2 (en) | Method for producing Cr-Mo case hardened steel | |
| JPH10265891A (en) | Ferrite / pearlite non-heat treated steel | |
| JP2829510B2 (en) | Method for producing high-strength hot-rolled steel sheet with excellent ductility and workability |