JPH01129953A - High strength non-heat treated steel and its manufacture - Google Patents
High strength non-heat treated steel and its manufactureInfo
- Publication number
- JPH01129953A JPH01129953A JP28899487A JP28899487A JPH01129953A JP H01129953 A JPH01129953 A JP H01129953A JP 28899487 A JP28899487 A JP 28899487A JP 28899487 A JP28899487 A JP 28899487A JP H01129953 A JPH01129953 A JP H01129953A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- bainite
- martensite
- strength
- toughness
- 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.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 68
- 239000010959 steel Substances 0.000 title claims abstract description 68
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 22
- 238000005242 forging Methods 0.000 claims abstract description 21
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 20
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 11
- 229910052796 boron Inorganic materials 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 9
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 9
- 229910052745 lead Inorganic materials 0.000 claims abstract description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 6
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 6
- 229910052714 tellurium Inorganic materials 0.000 claims abstract description 6
- 229910052711 selenium Inorganic materials 0.000 claims abstract 3
- 238000001816 cooling Methods 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 7
- 241000282342 Martes americana Species 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 abstract description 5
- 230000001105 regulatory effect Effects 0.000 abstract 2
- 239000000470 constituent Substances 0.000 abstract 1
- 229910052759 nickel Inorganic materials 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 10
- 230000007423 decrease Effects 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000002542 deteriorative effect Effects 0.000 description 3
- 229910001562 pearlite Inorganic materials 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
（産業上の利用分野）
本発明は非調質鋼の製造に係り、より詳細には、熱間で
プレス外とにより成形加工した後、調質処理を施すこと
なく、そのまま機械加工によって仕上げられる鍛造品、
例えば、自動車用部品、各種機械部品用に好適な高強度
非調質鋼並びにその製造方法に関するものである。
（従来の技術及び解決しようとする問題点）従来より、
ナックルスピンドル、ナックルアーム等々の主として足
回り部品などの自動車用部品や各種機械部品に用いられ
る熱間鍛造又は圧延部品には、熱間加工後、焼入れ一焼
もどし処理を施して所定の強度を確保する。いわゆる調
質型の鋼が用いられているが、近年の省エネルギー化、
低コスト化の要請から、か）る調質処理を必要とせずに
熱間加工後、そのまま利用できる非調質鋼の開発が進め
られている゛。
このような非調質鋼の一例として１例えば、熱間鍛造部
品の場合、中炭素鋼にＶを添加したものを熱間鍛造部品
冷し、組織をフェライト−パーライトとし、■炭化物の
析出強化により強度向上を狙ったタイプの非調質鋼が一
部、利用されるようになった（例、特公昭５８−５３７
０９号、同６１−２８７４２号）、シかし、このような
非調質鋼を用いた熱間鍛造品は、一般に強度が十分でな
く。
ますます増大する高強度化の要請化の要請には十分応え
られない。
本発明は、従来の非調質鋼の欠点である強度劣化の問題
を解決し、熱間鍛造後に調質処理を施すことなく、高強
度を確保すると共に疲労寿命を有し、併せて非調質鋼の
利点である郷関鍛造に際して省エネルギー、コスト低減
化を可能とする非調質鋼を提供することを目的とし、ま
たその製造方法を提供することを目的とするものである
。
（問題点を解決するための手段）
上記目的を達成するため、本発明者は、従来のこの種の
非調質鋼が中炭素鋼であることが優れた靭性の確保に支
障となっており、特に引張り強さが８０ｋｇｆ／ａｍ”
を超えると靭性の低下が著しいことが問題である点に鑑
みて、その原因を究明すると共に新たな解決策を見い出
すべく鋭意研究を重ねた。
その結果、従来の非調質鋼は中炭素鋼を熱間鍛造後、空
冷乃至放冷等の徐冷を行、い１組織を初析フェライト＋
パーライトとするため十分な強度が得られないので１強
度率足を補うため、■の析出強化を利用しているが、フ
ェライト＋パーライト組織では高強度化に限界があり、
またＶの析出強化は更に靭性を低下させてしまうことが
判明した。
そこで１本発明者は、初析フェライトを析出せしめない
組成及び熱履歴により優れた強度の確保と靭性の維持を
可能とする非調質鋼として、比較的低Ｃ（０，０４〜０
．２０％）とすることによってＭｓ点を高めてセルフテ
ンパーの効果を狙い、これをベースに適量のＣｒ、Ｍｏ
、Ｂ等を添加することによって良好な焼入性を確保し、
熱間鍛造後の冷却の際に容易にマルテンサイト又はベイ
ナイト或いはマルテンサイトとベイナイトの混合組織を
主体とし、初析フェライトを実質的に含まない組織が得
られるようにすることにより、高強度と共に良好な靭性
を保持できることを見い出した。そして、この知見に基
づいて更に非調質鋼の化学成分を詳細に検討し、ここに
本発明をなしたものである。
すなわち、本発明に係る高強度非調質鋼は、Ｃ：０．０
４〜０．２０％、Ｓｉ：０．０２〜１．０％、Ｍｎ：１
．０〜３．０％、Ｃｒ：０．５〜３．０％１Ｍｎ：０．
０５〜１．０％、Ｎｂ：０．０１〜０．２％、Ｔｉ：０
．０１〜０．０５％及びＢ：Ｏ，０Ｏ０３〜０．００５
％を含有し、必要に応じて、Ｎｉ≦３．０％、及び／又
は、Ｓ≦０．１５％、Ｐｂ≦０．３％、Ｃａ≦０．０１
％、Ｓｓ≦０．３％、Ｔｅ≦０．３％及びＢｉ≦０．３
％のうちの１種又は２種以上を含有し、残部が実質的に
Ｆｅからなり、熱間鍛造後の組織の主体がマルテンサイ
ト又はベイナイト或いはマルテンサイトとベイナイトの
混合組織であることを特徴とするものである。
また、高強度非調質鋼の製造方法に係る本発明は、上記
化学成分を有する鋼につき、９００〜１３００℃の温度
で熱間鍛造を行った後、冷却することにより、組織の主
体をマルテンサイト又はベイナイト或いはマルテンサイ
トとベイナイトの混合組織とすることを特徴とするもの
である。 □以下に本発明を実施例に基づいて詳細
に説明する。
まず、本発明における化学成分の限定理由を説明する。
Ｃ：
Ｃは低Ｃの高強度鋼として必要な強度を確保するために
必要な元素であり、そのためには０．０４％以上を含有
させることが必要である。但し、０．２０％を超えて多
量に含有させると、Ｍｓ点が低下し、セルフテンパーの
効果が減少し、靭性が低下して実用的でなくなる。した
がって、Ｃ量は０．０４〜０．２０％の範囲とする。
Ｓｉ：
ＳＬは溶製時の脱酸効果のほか、基地の強化に有効な元
素であり、そのためには０６０２％以上を添加する必要
がある。しかし、１．０％を超えて多量に添加すると被
削性が低下する。したがって、Ｓｉ量は０．０２〜１．
０％の範囲とする。
Ｍｎ：
ＭｎはＳｉと同様、溶製時の脱酸効果のほか、基地の強
化に有効な元素であり、そのために１．０％以上を添加
する必要がある。しかし、３．０％を超えて多量に添加
すると介在物が増加し、被削性が低下する。したがって
、Ｍｎ量は１．０〜３．０％の範囲とする。
Ｃｒ：
Ｃｒは良好な焼入性を確保するために必要な元素であり
、更には基地を強靭化し、耐摩耗性及び耐食性の向上に
有効な元素である。そのためには０．５％以上を添加す
る必要があるが、３．０％を超えて多量に添加すると靭
性が低下する。したがって、Ｃｒ量は０．５〜３．０％
の範囲とする。
ＭＯ：
Ｍｏは良好な焼入性を確保するために必要な元素であり
、更には基地を強靭化し、耐摩耗性の向上に有効な元素
である。そのためには０．０５％以上を添加する必要が
あるが、１．０％を超えて多量に添加すると靭性が低下
する。したがって、Ｍｏ量は０．０５〜１．０％の範囲
とする。
Ｎｂ：
Ｎｂの添加は、Ｎｂが高温までオーステナイト中へ固溶
せず、結晶粒成長を抑制して微細な組織を得ることがで
きるので、高い靭性が得られる。しかし、０．０１％未
満ではそのような効果が得られないので、０．０１％以
上を添加する必要があるが、Ｎｂは高価な元素であるの
で０．２％以下とする。
Ｔｉ：
Ｔｉは窒素をオーステナイト中で固定し、Ｂ添加による
焼入性を高めるために添加する必要がある。しかし、０
．０１％未満ではその効果が得られず、一方、０．０５
％を超えて多すぎると巨大な窒化物や炭化物が生じ、靭
性を低下する。したがって、Ｔｉ量は０．０１〜０．０
５％の範囲とする。
Ｂ：
Ｂは亜供析鋼において焼入性を向上させるのに効果のあ
る元素である。特にオーステナイト粒径が小さいときの
焼入性を向上させる効果が大きく。
その最大効果の得られる成分範囲が０．０００３〜０．
００５％であることが判明した。したがって、Ｂ量は０
．０００３〜０．００５％の範囲とする。
本発明鋼は、以上の元素を必須成分とするが、以下に説
明するように、更に必要に応じて、（１）Ｎｉを添加し
、（２）或いはＳ、Ｐｂ、Ｃａ、Ｓｅ、Ｔｅ及びＢｉの
うちの１種又は２種以上を添加することができる。勿論
、これらの（１）と（２）を複合添加することもできる
。
Ｎｉ：
Ｎｉは基地を強靭化すると共に焼入性を向上させるが、
３．０％を超えて多量に添加すると被剛性が低下するの
で、添加するときのＮｉ量は３．０％以下とする。
Ｓ、Ｐｂ％Ｃａ、Ｓｅ、Ｔｅ、Ｂｉ：
本発明鋼の使用用途を考慮すると被削性は重要な因子で
あり、Ｓ、Ｐｂ、Ｃａ、Ｓｓ、Ｔａ及びＢｉはいずれも
被削性を向上させるのに有効な元素である。しかし、多
すぎると熱間加工性を低下させ。
かつ、靭性を低下させるので、これらの元素を添加すル
トキハ、Ｓｉ２０．１５％Ｄ下、Ｐｂは０．３％以下、
Ｃａは０．０１％以下、Ｓｓは０．３％以下。
Ｔｅは０．３％以下、Ｂｉは０．２％以下とする。もっ
とも、Ｓを添加するときは１通常の不純物量を超えて上
記限度内で添加することは云うまでもない。
なお、本発明鋼には製造上、Ｐ等々の不可避的不純物が
随伴され得るが、それらは本発明の効果を損わない限度
で許容される。
以上の化学成分を有する本発明鋼は、従来と同様の製造
工程により熱間鍛造品の製造に供される。
但し、熱間鍛造は、通常、９００〜１３００℃の温度に
加熱して行い、熱間鍛造後、大気中で、或いは油、水又
は適当な冷媒を用いて適当な冷却速度（強冷、徐冷）で
冷却を行うことにより、組織の主体がマルテンサイト又
はベイナイト或いは両者の混合組織であって、殆ど或い
は全く初析フェ ″ライトを含まず、靭性の劣化を招く
ことなく高強度の熱間鍛造品を製造することができる。
鍛造温度が９００℃未満では組織が完全に均一なオース
テナイトにならず、また１３００℃を超えて加熱すると
熱間脆性を生じ、鍛造の際に割れが発生する原因となる
。従来の熱間鍛造用の調質鋼や非調質鋼は引張強さがせ
いぜい９０ｋｇｆ／＋ｕ＋”程度であるのに対し、本発
明鋼はｌ ＯＯｋｇｆ／ｓ＋■２以上の高強度を有し、
しかも従来の調質鋼と同等乃至より優れた靭性を有し、
優れた強度−靭性バランスを具備することが可能である
。
次に本発明の実施例を示す。
（実施例）
第１表に示す化学成分（ｗｔ％）を有する各種の鋼を常
法により溶解、鋳造し、圧延により鍛造用素材を製造し
た。なお、第１表中の従来鋼のうち、供試鋼Ｖは熱間鍛
造後焼入焼もどし処理を施して使用されている調質鋼で
あり、供試鋼Ｗは熱間鍛造用として使用されている非調
質鋼である。
次いで、この鍛造用素材を熱間鍛造により６０１履φの
丸棒の形状或いは断面４０ｍｒａ”Ｘ ７０ｍｍ’（７
）板状にした。その後、これらの材料を用いて、第２表
に示す処理条件にて加熱後冷却し、或いは加熱後熱間加
工を行い冷却し、試料とした。
各試料の機械的性質を調べるために、室温において引張
試験、硬さ測定並びにシャルピー衝撃試験を行った。そ
の結果を第２表乃至第４表に示す。
なお、引張試験にはＪＩＳ４号り型引張試験片を用い、
シャルピー衝撃試験にはＪＩＳａ号フルサイズ試験片を
用いた。
第２表乃至第４表に示すとおり、本発明鋼の場合、加熱
後空冷のみの材料は、いずれの比較鋼に比べても、靭性
を劣化させることなしに高強度を有しており、また加熱
後水冷した材料の強度は格段に増加している。更に、熱
間加工後冷却を行った材料においても、高強度が得られ
ている。
以上の結果を明確に示すため、本発明鋼の一部（供試鋼
Ａ、Ｂ、Ｃ）と各比較鋼の強度−靭性バランスを第１図
に示す、同図から明らかなとおり、本発明鋼は比較鋼に
比べて強度−靭性バランスが優れている。すなわち、本
発明鋼は、比較鋼に比べ、靭性を劣化させずに高強度化
が可能であり、かつ、非調質でこれを製造することがで
きる。これは、前述のとおり、Ｃ量を低減し、更に焼入
性を高めるＭｎ、Ｃｒ、Ｍｏ、Ｂ等を添加することによ
って組織の主体をマルテンサイト又はベイナイト或いは
これらの混合組織としたことによるものである。なお、
本発明鋼の上記処理後のミクロ組織は、すべてマルテン
サイト及びベイナイトを主体とした組織となっていた。
また、適量のＳ、Ｃａ、Ｐｂ、Ｓｓ、Ｔｅ又はＢｉを添
加した本発明鋼は、高強度及び高靭性に悪影響を及ぼす
ことなく良好な被剛性を有することを切削試験により確
認した。(Industrial Application Field) The present invention relates to the production of non-tempered steel, and more specifically, it is formed by hot forming outside of a press and then finished by machining as it is without being heat-treated. forged products,
For example, the present invention relates to high-strength non-temperature steel suitable for automobile parts and various mechanical parts, and a method for producing the same. (Conventional technology and problems to be solved) Conventionally,
Hot forged or rolled parts used for automobile parts and various mechanical parts, mainly undercarriage parts such as knuckle spindles and knuckle arms, are quenched and tempered after hot working to ensure the specified strength. do. So-called tempered steel is used, but in recent years energy saving and
In response to the demand for lower costs, progress is being made in the development of non-heat treated steels that can be used as is after hot working without the need for such heat treatment. An example of such non-tempered steel is 1. For example, in the case of hot forged parts, medium carbon steel with V added is cooled to create a ferrite-pearlite structure, and ■ hardened by precipitation of carbides. Some types of non-tempered steel aimed at improving strength have come into use (for example,
(No. 09, No. 61-28742), but hot forged products using such non-tempered steel generally do not have sufficient strength. It is not possible to adequately meet the ever-increasing demand for higher strength. The present invention solves the problem of strength deterioration, which is a drawback of conventional non-tempered steel, and achieves high strength and long fatigue life without undergoing heat treatment after hot forging. The purpose of this invention is to provide non-thermal steel that enables energy saving and cost reduction during forging, which is an advantage of quality steel, and also to provide a method for producing the same. (Means for Solving the Problem) In order to achieve the above object, the present inventor discovered that the conventional non-thermal steel of this type is a medium carbon steel, which is an obstacle to ensuring excellent toughness. , especially the tensile strength is 80kgf/am”
Considering that the problem is that the toughness decreases significantly when the temperature exceeds 100 mm, we conducted extensive research to investigate the cause and find a new solution. As a result, conventional non-temperature steels are made by hot forging medium carbon steel and then slowly cooling it by air cooling or standing to cool it to change the microstructure to pro-eutectoid ferrite +
Since sufficient strength cannot be obtained due to the pearlite structure, precipitation strengthening (■) is used to compensate for one strength factor, but there is a limit to increasing the strength with the ferrite + pearlite structure.
It has also been found that the precipitation strengthening of V further reduces the toughness. Therefore, the present inventor developed a relatively low C (0.04 to 0.04
．． 20%) to raise the Ms point and aim for the self-tempering effect, and based on this, appropriate amounts of Cr and Mo
, B, etc. ensure good hardenability,
By making it easy to obtain a structure consisting mainly of martensite, bainite, or a mixed structure of martensite and bainite, and substantially free of pro-eutectoid ferrite, during cooling after hot forging, it has high strength and good performance. We have discovered that it is possible to maintain a high degree of toughness. Based on this knowledge, the chemical composition of non-tempered steel was further studied in detail, and the present invention was hereby accomplished. That is, the high-strength non-tempered steel according to the present invention has C: 0.0
4-0.20%, Si: 0.02-1.0%, Mn: 1
．． 0-3.0%, Cr: 0.5-3.0% 1Mn: 0.
05-1.0%, Nb: 0.01-0.2%, Ti: 0
．． 01-0.05% and B:O,0O03-0.005
%, and if necessary, Ni≦3.0% and/or S≦0.15%, Pb≦0.3%, Ca≦0.01
%, Ss≦0.3%, Te≦0.3% and Bi≦0.3
%, the remainder substantially consists of Fe, and the main structure after hot forging is martensite, bainite, or a mixed structure of martensite and bainite. It is something to do. In addition, the present invention, which relates to a method for producing high-strength non-tempered steel, hot forges steel having the above chemical composition at a temperature of 900 to 1300°C and then cools it, thereby converting the main structure of the steel into marten. It is characterized by having a structure of site, bainite, or a mixed structure of martensite and bainite. □The present invention will be explained in detail below based on examples. First, the reason for limiting the chemical components in the present invention will be explained. C: C is an element necessary to ensure the strength required as a low C high strength steel, and for this purpose it is necessary to contain 0.04% or more. However, if it is contained in a large amount exceeding 0.20%, the Ms point decreases, the self-tempering effect decreases, and the toughness decreases, making it impractical. Therefore, the amount of C is set in the range of 0.04 to 0.20%. Si: SL is an element that is effective in strengthening the base as well as having a deoxidizing effect during melting, and for this purpose it is necessary to add 0.602% or more. However, when added in a large amount exceeding 1.0%, machinability decreases. Therefore, the amount of Si is 0.02 to 1.
The range is 0%. Mn: Like Si, Mn is an element effective in strengthening the base as well as having a deoxidizing effect during melting, and for this purpose it is necessary to add 1.0% or more. However, when added in a large amount exceeding 3.0%, inclusions increase and machinability deteriorates. Therefore, the Mn content is in the range of 1.0 to 3.0%. Cr: Cr is an element necessary to ensure good hardenability, and furthermore, it is an element effective in toughening the matrix and improving wear resistance and corrosion resistance. For this purpose, it is necessary to add 0.5% or more, but if it is added in a large amount exceeding 3.0%, the toughness will decrease. Therefore, the amount of Cr is 0.5-3.0%
The range shall be . MO: Mo is an element necessary to ensure good hardenability, and furthermore, it is an element effective in toughening the matrix and improving wear resistance. For this purpose, it is necessary to add 0.05% or more, but if it is added in a large amount exceeding 1.0%, the toughness will decrease. Therefore, the amount of Mo is set in the range of 0.05 to 1.0%. Nb: When Nb is added, high toughness can be obtained because Nb does not dissolve into austenite until high temperatures and suppresses grain growth to obtain a fine structure. However, such an effect cannot be obtained if the content is less than 0.01%, so it is necessary to add 0.01% or more, but since Nb is an expensive element, it is limited to 0.2% or less. Ti: Ti needs to be added in order to fix nitrogen in austenite and improve the hardenability due to the addition of B. However, 0
．． If it is less than 0.01%, the effect cannot be obtained; on the other hand, if it is less than 0.05
If the amount exceeds 5%, giant nitrides and carbides will be formed, reducing toughness. Therefore, the amount of Ti is 0.01 to 0.0
The range shall be 5%. B: B is an element that is effective in improving the hardenability of sub-deposited steel. It is particularly effective in improving hardenability when the austenite grain size is small. The range of ingredients where the maximum effect can be obtained is 0.0003~0.
It turned out to be 0.005%. Therefore, the amount of B is 0
．． The range is 0003% to 0.005%. The steel of the present invention has the above elements as essential components, but as described below, (1) Ni may be added, (2) or S, Pb, Ca, Se, Te, and One or more types of Bi can be added. Of course, these (1) and (2) can also be added in combination. Ni: Ni strengthens the base and improves hardenability, but
If added in a large amount exceeding 3.0%, the stiffness will decrease, so the amount of Ni added should be 3.0% or less. S, Pb%Ca, Se, Te, Bi: Considering the intended use of the steel of the present invention, machinability is an important factor, and S, Pb, Ca, Ss, Ta, and Bi all improve machinability. It is an effective element for However, if the amount is too high, hot workability will be reduced. In addition, since these elements reduce the toughness, Si is 20.15% D, Pb is 0.3% or less,
Ca is 0.01% or less, Ss is 0.3% or less. The content of Te is 0.3% or less, and the content of Bi is 0.2% or less. However, it goes without saying that when S is added, it should be added in an amount exceeding the normal impurity amount and within the above-mentioned limit. Incidentally, the steel of the present invention may be accompanied by unavoidable impurities such as P during manufacturing, but these are allowed as long as they do not impair the effects of the present invention. The steel of the present invention having the above-mentioned chemical components is used to manufacture hot forged products through the same manufacturing process as conventional ones. However, hot forging is usually carried out by heating to a temperature of 900 to 1300°C, and after hot forging, cooling is performed at an appropriate cooling rate (strong cooling, slow cooling) in the air, or using oil, water, or an appropriate coolant. By cooling with cold), the main structure is martensite, bainite, or a mixture of both, and contains little or no pro-eutectoid ferrite, resulting in high-strength hot steel without deterioration of toughness. Forged products can be manufactured. If the forging temperature is less than 900°C, the structure will not become completely uniform austenite, and if heated above 1300°C, hot embrittlement will occur, which will cause cracks to occur during forging. While conventional heat-treated steel and non-heat-treated steel for hot forging have a tensile strength of about 90 kgf/+u+'' at most, the steel of the present invention has a high strength of more than lOOkgf/s+■2. have,
Moreover, it has the same or better toughness than conventional tempered steel,
It is possible to have an excellent strength-toughness balance. Next, examples of the present invention will be shown. (Example) Various steels having the chemical compositions (wt%) shown in Table 1 were melted and cast by conventional methods, and forging materials were produced by rolling. Of the conventional steels in Table 1, sample steel V is a heat-treated steel that has been quenched and tempered after hot forging, and sample steel W is used for hot forging. It is a non-tempered steel. Next, this forging material is hot forged into a round bar shape of 601mm diameter or a cross section of 40mra" x 70mm' (7
) It was made into a plate shape. Thereafter, these materials were heated and cooled under the treatment conditions shown in Table 2, or heated and then hot worked and cooled to give samples. To examine the mechanical properties of each sample, tensile tests, hardness measurements, and Charpy impact tests were conducted at room temperature. The results are shown in Tables 2 to 4. In addition, a JIS No. 4 type tensile test piece was used for the tensile test.
A JISa full size test piece was used for the Charpy impact test. As shown in Tables 2 to 4, in the case of the steel of the present invention, the material that is only air-cooled after heating has high strength without deteriorating toughness, compared to any of the comparative steels. The strength of the material that has been water-cooled after heating is significantly increased. Furthermore, high strength has been obtained even in materials that have been cooled after hot working. In order to clearly show the above results, the strength-toughness balance of some of the inventive steels (test steels A, B, and C) and each comparative steel is shown in Fig. 1.As is clear from the figure, the inventive steel The steel has a better strength-toughness balance than comparison steels. That is, compared to comparative steels, the steel of the present invention can be increased in strength without deteriorating toughness, and can be manufactured without heat refining. This is because, as mentioned above, the main structure of the structure is martensite, bainite, or a mixture thereof by reducing the amount of C and adding Mn, Cr, Mo, B, etc., which further improve the hardenability. It is. In addition,
The microstructure of the steel of the present invention after the above treatment was entirely composed of martensite and bainite. Further, it was confirmed through a cutting test that the steel of the present invention to which an appropriate amount of S, Ca, Pb, Ss, Te, or Bi was added had good rigidity without adversely affecting high strength and high toughness.
（発明の効果）
以上詳述したように、本発明に係る非調質鋼は、低Ｃに
てＣｒ、Ｍｏと共にＮｂ、Ｔｉ、Ｂ等の元素を適量添加
して化学成分を調整して、鍛造後の組織の主体を低Ｃの
マルテンサイト又はベイナイト或いはこれらの混合組織
としたので、従来の調質鋼及び非調質鋼よりも靭性を劣
化させることなく高強度が得られ、強度−靭性バランス
の優れた非調質鋼を得ることができる。更に、非調質鋼
であるため、調質鋼に比べて焼入−焼もどしの調質処理
を省略でき、生産性の向上並びに低コスト化の効果が顕
著であり、高強度が得られることからも、本発明鋼は自
動車、産業機械などで高強度が要求される各種部品の材
料としての利用価値は極めて大きい。(Effects of the Invention) As detailed above, the non-tempered steel according to the present invention has a chemical composition adjusted by adding appropriate amounts of elements such as Nb, Ti, and B along with Cr and Mo at low C. Since the main structure of the structure after forging is low C martensite, bainite, or a mixed structure of these, higher strength can be obtained without deteriorating toughness than conventional heat-treated steel and non-heat-treated steel, and the strength-toughness ratio is It is possible to obtain well-balanced non-thermal steel. Furthermore, since it is a non-thermal treated steel, compared to tempered steel, the thermal treatment of quenching and tempering can be omitted, and the effects of improved productivity and cost reduction are significant, and high strength can be obtained. Therefore, the steel of the present invention has extremely high utility value as a material for various parts that require high strength in automobiles, industrial machinery, etc.
第１図は本発明鋼（非調質鋼）及び従来鋼（調質鋼、非
調質鋼）における引張強さとｉ撃値（シャルピー衝撃値
）の関係を示す図である。FIG. 1 is a diagram showing the relationship between tensile strength and i-impact value (Charpy impact value) in the steel of the present invention (non-tempered steel) and conventional steel (tempered steel, non-tempered steel).
Claims (5)
０％、Ｓｉ：０．０２〜１．０％、Ｍｎ：１．０〜３．
０％、Ｃｒ：０．５〜３．０％、Ｍｏ：０．０５〜１．
０％、Ｎｂ：０．０１〜０．２％、Ｔｉ：０．０１〜０
．０５％及びＢ：０．０００３〜０．００５％を含有し
、残部が実質的にＦｅからなり、熱間鍛造後の組織の主
体がマルテンサイト又はベイナイト或いはマルテンサイ
トとベイナイトの混合組織であることを特徴とする高強
度非調質鋼。(1) In weight% (the same applies hereinafter), C: 0.04 to 0.2
0%, Si: 0.02-1.0%, Mn: 1.0-3.
0%, Cr: 0.5-3.0%, Mo: 0.05-1.
0%, Nb: 0.01-0.2%, Ti: 0.01-0
．． 05% and B: 0.0003 to 0.005%, the remainder substantially consists of Fe, and the main structure after hot forging is martensite, bainite, or a mixed structure of martensite and bainite. High-strength non-thermal steel featuring
．０％、Ｍｎ：１．０〜３．０％、Ｃｒ：０．５〜３．
０％、Ｍｏ：０．０５〜１．０％、Ｎｂ：０．０１〜０
．２％、Ｔｉ：０．０１〜０．０５％及びＢ：０．００
０３〜０．００５％を含有し、更にＮｉ≦３．０％を含
有し、残部が実質的にＦｅからなり、熱間鍛造後の組織
の主体がマルテンサイト又はベイナイト或いはマルテン
サイトとベイナイトの混合組織であることを特徴とする
高強度非調質鋼。(2) C: 0.04-0.20%, Si: 0.02-1
．． 0%, Mn: 1.0-3.0%, Cr: 0.5-3.
0%, Mo: 0.05-1.0%, Nb: 0.01-0
．． 2%, Ti: 0.01-0.05% and B: 0.00
03 to 0.005%, further contains Ni≦3.0%, the remainder substantially consists of Fe, and the main body of the structure after hot forging is martensite, bainite, or a mixture of martensite and bainite. High-strength non-thermal steel characterized by its structure.
．０％、Ｍｎ：１．０〜３．０％、Ｃｒ：０．５〜３．
０％、Ｍｏ：０．０５〜１．０％、Ｎｂ：０．０１〜０
．２％、Ｔｉ：０．０１〜０．０５％及びＢ：０．００
０３〜０．００５％を含有し、更にＳ≦０．１５％、Ｐ
ｂ≦０．３％、Ｃａ≦０．０１％、Ｓｅ≦０．３％、Ｔ
ｅ≦０．３％及びＢｉ≦０．３％のうちの１種又は２種
以上を含有し、残部が実質的にＦｅからなり、熱間鍛造
後の組織の主体がマルテンサイト又はベイナイト或いは
マルテンサイトとベイナイトの混合組織であることを特
徴とする高強度非調質鋼。(3) C: 0.04-0.20%, Si: 0.02-1
．． 0%, Mn: 1.0-3.0%, Cr: 0.5-3.
0%, Mo: 0.05-1.0%, Nb: 0.01-0
．． 2%, Ti: 0.01-0.05% and B: 0.00
03 to 0.005%, and further contains S≦0.15%, P
b≦0.3%, Ca≦0.01%, Se≦0.3%, T
Contains one or more of e≦0.3% and Bi≦0.3%, the remainder substantially consists of Fe, and the main body of the structure after hot forging is martensite, bainite, or marten. A high-strength non-thermal steel characterized by a mixed structure of site and bainite.
．０％、Ｍｎ：１．０〜３．０％、Ｃｒ：０．５〜３．
０％、Ｍｏ：０．０５〜１．０％、Ｎｂ：０．０１〜０
．２％、Ｔｉ：０．０１〜０．０５％及びＢ：０．００
０３〜０．００５％を含有し、更にＮｉ≦３．０％と、
Ｓ≦０．１５％、Ｐｂ≦０．３％、Ｃａ≦０．０１％、
Ｓｅ≦０．３％、Ｔｅ≦０．３％及びＢｉ≦０．３％の
うちの１種又は２種以上とを含有し、残部が実質的にＦ
ｅからなり、熱間鍛造後の組織の主体がマルテンサイト
又はベイナイト或いはマルテンサイトとベイナイトの混
合組織であることを特徴とする高強度非調質鋼。(4) C: 0.04-0.20%, Si: 0.02-1
．． 0%, Mn: 1.0-3.0%, Cr: 0.5-3.
0%, Mo: 0.05-1.0%, Nb: 0.01-0
．． 2%, Ti: 0.01-0.05% and B: 0.00
03 to 0.005%, and further Ni≦3.0%,
S≦0.15%, Pb≦0.3%, Ca≦0.01%,
Contains one or more of Se≦0.3%, Te≦0.3%, and Bi≦0.3%, and the remainder is substantially F.
A high-strength non-heat treated steel characterized in that the main structure after hot forging is martensite, bainite, or a mixed structure of martensite and bainite.
０％、Ｍｎ：１．０〜３．０％、Ｃｒ：０．５〜３．０
％、Ｍｏ：０．０５〜１．０％、Ｎｂ：０．０１〜０．
２％、Ｔｉ：０．０１〜０．０５％及びＢ：０．０００
３〜０．００５％を含有し、更に必要に応じて、Ｎｉ≦
３．０％、及び／又は、Ｓ≦０．１５％、Ｐｂ≦０．３
％、Ｃａ≦０．０１％、Ｓｅ≦０．３％、Ｔｅ≦０．３
％及びＢｉ≦０．３％のうちの１種又は２種以上を含有
し、残部が実質的にＦｅからなる鋼につき、９００〜１
３００℃で熱間鍛造を行った後、冷却することにより、
組織の主体をマルテンサイト又はベイナイト或いはマル
テンサイトとベイナイトの混合組織とすることを特徴と
する高強度非調質鋼の製造方法。(5) C: 0.4-0.20%, Si: 0.02-1.
0%, Mn: 1.0-3.0%, Cr: 0.5-3.0
%, Mo: 0.05-1.0%, Nb: 0.01-0.
2%, Ti: 0.01-0.05% and B: 0.000
3 to 0.005%, and if necessary, Ni≦
3.0% and/or S≦0.15%, Pb≦0.3
%, Ca≦0.01%, Se≦0.3%, Te≦0.3
% and Bi≦0.3%, and the remainder is substantially Fe, 900 to 1
By hot forging at 300℃ and then cooling,
1. A method for producing high-strength non-tempered steel, characterized in that the structure is mainly martensite, bainite, or a mixed structure of martensite and bainite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28899487A JPH01129953A (en) | 1987-11-16 | 1987-11-16 | High strength non-heat treated steel and its manufacture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28899487A JPH01129953A (en) | 1987-11-16 | 1987-11-16 | High strength non-heat treated steel and its manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01129953A true JPH01129953A (en) | 1989-05-23 |
Family
ID=17737468
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28899487A Pending JPH01129953A (en) | 1987-11-16 | 1987-11-16 | High strength non-heat treated steel and its manufacture |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01129953A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20020053398A (en) * | 2000-12-27 | 2002-07-05 | 이계안 | A microalloyed steel with high strength bainitic structure |
| KR20030008852A (en) * | 2001-07-20 | 2003-01-29 | 현대자동차주식회사 | High strength bainitic microalloyed steel for automotive chassy component |
| WO2009057731A1 (en) | 2007-10-29 | 2009-05-07 | Nippon Steel Corporation | Martensitic non-heat-treated steel for hot forging and non-heat-treated steel hot forgings |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5524932A (en) * | 1978-08-08 | 1980-02-22 | Nippon Steel Corp | Manufacture of bainite tough hardening steel |
| JPS5983722A (en) * | 1982-11-05 | 1984-05-15 | Kawasaki Steel Corp | Preparation of low carbon equivalent unnormalized high tensile steel plate |
| JPS61238941A (en) * | 1985-04-15 | 1986-10-24 | Kobe Steel Ltd | Untempered steel for hot forging |
| JPS61279656A (en) * | 1985-06-05 | 1986-12-10 | Daido Steel Co Ltd | Non-heattreated steel for hot forging |
| JPS61284553A (en) * | 1985-06-12 | 1986-12-15 | Kobe Steel Ltd | Steel material for unnormalized bolt or the like having excellent toughness |
| JPS6456821A (en) * | 1987-08-27 | 1989-03-03 | Kobe Steel Ltd | Production of high-toughness, high-fatigue strength, warm-forged, and non-heat treated steel |
-
1987
- 1987-11-16 JP JP28899487A patent/JPH01129953A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5524932A (en) * | 1978-08-08 | 1980-02-22 | Nippon Steel Corp | Manufacture of bainite tough hardening steel |
| JPS5983722A (en) * | 1982-11-05 | 1984-05-15 | Kawasaki Steel Corp | Preparation of low carbon equivalent unnormalized high tensile steel plate |
| JPS61238941A (en) * | 1985-04-15 | 1986-10-24 | Kobe Steel Ltd | Untempered steel for hot forging |
| JPS61279656A (en) * | 1985-06-05 | 1986-12-10 | Daido Steel Co Ltd | Non-heattreated steel for hot forging |
| JPS61284553A (en) * | 1985-06-12 | 1986-12-15 | Kobe Steel Ltd | Steel material for unnormalized bolt or the like having excellent toughness |
| JPS6456821A (en) * | 1987-08-27 | 1989-03-03 | Kobe Steel Ltd | Production of high-toughness, high-fatigue strength, warm-forged, and non-heat treated steel |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20020053398A (en) * | 2000-12-27 | 2002-07-05 | 이계안 | A microalloyed steel with high strength bainitic structure |
| KR20030008852A (en) * | 2001-07-20 | 2003-01-29 | 현대자동차주식회사 | High strength bainitic microalloyed steel for automotive chassy component |
| WO2009057731A1 (en) | 2007-10-29 | 2009-05-07 | Nippon Steel Corporation | Martensitic non-heat-treated steel for hot forging and non-heat-treated steel hot forgings |
| US9376738B2 (en) | 2007-10-29 | 2016-06-28 | Nippon Steel & Sumitomo Metal Corporation | Hot forging use non-heat-treated steel and hot forged non-heat-treated steel part |
| US9487848B2 (en) | 2007-10-29 | 2016-11-08 | Nippon Steel & Sumitomo Metal Corporation | Hot forging use non-heat-treated steel and hot forged non-heat-treated steel part |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4629816B2 (en) | High strength bolt excellent in delayed fracture resistance and method for producing the same | |
| JPH0441616A (en) | Production of low-hardness water-resistant steel excellent in wear resistance and bendability | |
| JPS5853709B2 (en) | As-forged high-strength forging steel | |
| JPH0772323B2 (en) | Non-heat treated steel bar for hot forging | |
| JPS589813B2 (en) | Manufacturing method for non-thermal forged steel products | |
| JP4328924B2 (en) | Manufacturing method of high-strength shaft parts | |
| JPH039168B2 (en) | ||
| JPS6159379B2 (en) | ||
| JP2768062B2 (en) | Manufacturing method of high strength tough steel | |
| JPH01176055A (en) | Non-heat treated steel for hot forging having excellent machinability | |
| JP2000336460A (en) | Hot rolled wire rod and steel bar for machine structure and manufacture of the same | |
| JPH0425343B2 (en) | ||
| JPH01129953A (en) | High strength non-heat treated steel and its manufacture | |
| JPS582572B2 (en) | Method for manufacturing strong steel bars with little anisotropy | |
| JPH04297548A (en) | High strength and high toughness non-heat treated steel and its manufacture | |
| JPH10265841A (en) | Production of high strength cold forging parts | |
| JPH07310118A (en) | Production of case hardening steel suitable for cold-working | |
| JPS6137333B2 (en) | ||
| JPH01225751A (en) | Work roll for heavy-load cold rolling excellent in spalling resistance and its production | |
| JPH0526850B2 (en) | ||
| JPS59159971A (en) | Steel for cold forging with superior hardenability | |
| JP2000160285A (en) | High-strength and high-toughness non-heat treated steel | |
| JPS63312949A (en) | Non-refining steel for hot forging having high toughness | |
| JPH10280036A (en) | Wire rod for high strength bolt excellent in strength and ductility and its production | |
| JPH0572442B2 (en) |