JPS63312949A - Non-refining steel for hot forging having high toughness - Google Patents
Non-refining steel for hot forging having high toughnessInfo
- Publication number
- JPS63312949A JPS63312949A JP14868287A JP14868287A JPS63312949A JP S63312949 A JPS63312949 A JP S63312949A JP 14868287 A JP14868287 A JP 14868287A JP 14868287 A JP14868287 A JP 14868287A JP S63312949 A JPS63312949 A JP S63312949A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- toughness
- hot forging
- bainite
- martensite
- 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 58
- 239000010959 steel Substances 0.000 title claims abstract description 58
- 238000005242 forging Methods 0.000 title claims abstract description 33
- 238000007670 refining Methods 0.000 title description 4
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 17
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052714 tellurium Inorganic materials 0.000 claims abstract description 6
- 229910052745 lead Inorganic materials 0.000 claims abstract description 5
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 3
- 229910052711 selenium Inorganic materials 0.000 claims description 3
- 229910052797 bismuth Inorganic materials 0.000 abstract description 5
- 239000000203 mixture Substances 0.000 abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 15
- 229910001566 austenite Inorganic materials 0.000 description 7
- 239000000126 substance Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910001562 pearlite Inorganic materials 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000007669 thermal treatment Methods 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 241000282342 Martes americana Species 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002826 coolant Substances 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
- 238000009863 impact test Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
（産業上の利用分野）
本発明は熱間鍛造用非調質鋼に係り、より詳細には、熱
間でプレスなど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上仕
上げられる鍛造品１例えば、船舶、自動車などの各種機
械部品用に好適な非調質鋼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、
船舶用部品や、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に用いられ
る熱間鍛造部品には、熱間鍛造後、焼入れ一焼もどし処
理を施して強度。
靭性を確保する、いわゆる調質型の鍛造用鋼が用いられ
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Ｎる調質処理を必要とせずに熱間鍛造後、そのま
ま利用できる非調質型の鍛造用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、例えば、中炭素鋼に
Ｖを添加したものを熱間鍛造後空冷し、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５８−５３７０９号、同６１−２８７
４２号）、シかし、このような非調質鋼を用いた熱間鍛
造品は、一般に靭性が劣るという問題がある。
本発明は、従来の熱間鍛造用非調質鋼の欠点である靭性
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、優れた靭性を確保すると共に高強度を維持し、併
せて非調質鋼の利点である熱間鍛造に際して省エネルギ
ー、コスト低減化を可能とする熱間鍛造用非調質鋼を提
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８０ ｋｇｆ ／
ｍｉｄ”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、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、強度
不足を補うため、■の析出強化を利用しているが、フェ
ライト＋パーライト組織の靭性は本来十分高くなく、■
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、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及び靭性を得ることが
できる非調質鋼として、まず低炭素鋼（Ｃ：０．０４〜
０．２０％）を対象として一応の強度を確保すると共に
靭性の低下を防止し、更に熱間鍛造後に直接水冷するこ
とにより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にし、初析フェライトを
含まない組織とすることにより１強度と共に特にＮｂ添
加によりオーステナイト結晶粒の微細化による高靭性化
を図ることが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、本発明に係る高靭性熱間鍛造用非調質鋼は、
Ｃ：０．０４〜０．２０％、Ｓｉ：０．０５〜１．０％
、Ｍｎ：０．８〜２．０％、Ｎｂ：０．０１〜０１１５
％、Ｔｉ：０．０１〜０．０５％、Ｂ：Ｏ，０．０００
３〜０．００５％及びＡｌ：０．００５〜０．１０％を
含有し、必要に応じて、Ｓ≦０．１５％、Ｐｂ≦０．３
０％、Ｃａ≦０．０１％、Ｓｅ≦０．３０％、Ｔｅ≦０
．３０％及びＢｉ≦０．３０％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
直接水冷により得られる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は強度、靭性を支配する重要な因子であり、従来の熱
間鍛造用非調質鋼では比較的多くのＣを含有させて強度
を確保しているが、靭性の劣化を招いている。一方、本
発明においては、低Ｃ鋼とすることが特徴の１つであり
、熱間鍛造後水冷により特定の組織とすることにより、
低Ｃでも比較的高い強度及び靭性を得ることができるこ
とに着目し、Ｃ量を低く規制したものである。しかし。
Ｃ量を低くしすぎ、ると強度が充分確保できなくなるの
で、０．０４％以上が必要である。一方、Ｃ量が増すと
強度上昇には有効であるものの、靭性を低下させるので
、０．２０％以下とする必要がある。したがって、Ｃ量
は０．０４〜０．２０％の範囲とする。
Ｓｉ：
Ｓｉは脱酸剤として不可欠の元素であり、そのために０
．０５％以上が必要である。一方、Ｓｉは強化元素とし
ても有効であるが、１．０％を超える過剰な添加は靭性
を劣化させる。したがって、Ｓｉ量は０．０５〜１．０
％の範囲とする。
Ｍｎ：
Ｍｎは鋼の焼入性を増す元素として有効な元素であり、
本発明のように低Ｃ鋼でＣによる強化機構を充分に発揮
させるためには、Ｍｎ量は０．８％未満では不充分であ
るので、０．８％以上添加する必要がある。しかし、２
．０％を超えて添加しても、その効果は少なく、却って
被削性を劣化させる。したがって、Ｍｎ量は０．８〜２
．０％の範囲とする。
Ｎｂ：
Ｎｂを添加することは本発明の最も大きな特徴とする点
である。すな力ち、Ｎｂは、Ｎｂの炭窒化物がオーステ
ナイト結晶粒の粗大化を防止するので、靭性の向上に有
効である。また、１１００℃以上の高温加熱に際し、Ｎ
ｂはオーステナイト中に固溶して焼入性を向上させ、強
度を上昇させる効果もある。Ｎｂの添加量が０．０１％
未満ではオーステナイト粒微細化効果が少なく、多いほ
ど上記効果のためには望ましい、しかし、Ｎｂは高価な
元素であり、０．１５％を超えるとコスト高となり、好
ましくない、したがって、Ｎｂ量は０．０１〜０．１５
％の範囲とする。
Ｔｉ：
Ｔ１はＮをオーステナイト中に固定し、Ｂの焼入性効果
を高めるために添加するが、０．０１％未満ではその効
果が不充分であるので、０．０１％以上必要である。し
かし、０．０５％を超えて添加しても、その効果は増加
しない。したがって、Ｔｉ量は０．０１〜０．０５％の
範囲とする。
Ｂ：
Ｂは低Ｃ鋼の焼入性を増す元素であり、強度、靭性の向
上に有効である。添加量がｏ、ｏ ｏ ｏ ａ％未満で
はその効果がなく、一方、０．００５％を超えて過剰に
添加するとＢの析出物が生成して靭性が劣化する。した
がって、Ｂ量はｏ、ｏ ｏ 。
３〜０．００５％の範囲とする。
ＡＱ：
Ａｆｉは有効な脱酸剤であると共にオーステナイト結晶
粒の微細化に有効で、靭性の向上効果がある元素である
。靭性向上を図るためには０．００５％以上の添加が必
要であるが、０．１０％以下で充分であり、０．１０％
を超えて添加すると被削性の低下を招く、シたがって、
ΔΩ量は０．００５〜０．１０％の範囲とする。
本発明鋼は１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、被削性改善の
ために適量の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。
Ｓ、Ｐｂ、Ｃａ、Ｓｅ、Ｔｅ、Ｂｉ：
Ｓ、Ｐｂ、Ｃａ、Ｓｅ、Ｔｅ及びＢｉは被削性の改善に
効果がある元素であり、単独又は複合で添加できる。こ
れらの元素の添加量は、鋼の基本的な性質に及ぼす影響
を考慮して、Ｓは０．１５％以下、ｐｂは０．３０％以
下、Ｃａは０．０１％以下。
Ｓｅは０．３０％以下、Ｔｅは０．３０％以下、 Ｂｉ
は０．３０％以下とし、この範囲内であれば強度。
靭性に格別の影響を与えることがない、もつとも、Ｓを
添加するときは、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１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部品の製造に供される。熱間鍛造は
、９００〜１３００’Ｃの温度に加熱してプレスなどに
より鍛造成形を行い、その後。
冷却される。
但し、熱間鍛造後の冷却に際しては、直接水又は水に近
い冷却能を有する冷却媒体（本発明では。
これらを「水」と定義する）中で冷却し、鋼の組織の主
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必要がある。これは、
上記化学成分を有する低Ｃ鋼におけるマルテンサイト又
はベイナイト或いはこれらの混合組織は、比較的高い強
度を有し、従来の熱間鍛造用調質鋼で必須とされている
焼もどし処理を施すことなく、高い靭性を有しているこ
とが判明したためである。また、従来の中炭素の熱間鍛
造用非調質鋼は靭性が不充分であり、特に引張り強さが
８０ ｋｇｆ ／ ｍｍ”を超えると靭性低下が著しい
のに対し、本発明によれば、上記組織に初析フェライト
が殆ど含まれていないこともあって、靭性を顕著に改善
することができると共に強度も向上でき、従来の熱間鍛
造用調質鋼と同等の強度。
靭性を得ることができる。しかも、調質処理が不要であ
るので、生産性の向上とコスト低減の効果が顕著である
。
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２５〜５０ｍｍφの
鍛造用素材を製造した。これを鍛造温度に相当する９０
０〜１２５０℃に加熱し、その後。
直接水冷した。得られた鋼材について硬さくビッカース
硬さ）を調べると共に、室温で２ｍｍＵノツチのフルサ
イズ試験片によりシャルピー衝撃試験を行って靭性を評
価した。その結果を第２表及び第３表に示す・
また、第１表に示した鋼の一部について、同様にして得
た素材を１０００℃又は１２００℃に加熱後、熱間加工
（加工率５０％）し、その後、直接水冷した鋼材につい
ても、同様にして硬さと靭性を調べた。その結果を第４
表に示す。
なお、第１表中のＮα２７は従来の焼入れ−焼きもどし
による調質鋼であり、Ｎａ ２８は熱間鍛造後空冷する
非調質鋼であり、これらについても硬さ及び靭性を調べ
、その結果を併記した。
第２表、第３表及び第４表並びに一部の供試鋼について
の結果を図示した第１図から明らかなように１本発明鋼
はいずれも優れた強度と靭性を兼ね備えており、特に従
来の非調質鋼Ｎα２８よりも靭性が顕著に改善され且つ
強度も高く、従来の調質ｔｌＮａ２７と同等の強度、靭
性を有している。
なお、被削性の改善に効果のある元素を添加した本発明
鋼について切削試験を行ったところ、優れた被削性を備
えていることを確認した。(Industrial Application Field) The present invention relates to non-tempered steel for hot forging, and more specifically, after hot forming by pressing or the like. The present invention relates to a forged product 1 that can be finished by machining as it is without being heat treated, such as non-heat treated steel suitable for various mechanical parts such as ships and automobiles. (Conventional technology and problems to be solved) Conventionally,
Hot forged parts used for marine parts and automotive parts, mainly undercarriage parts such as knuckle spindles and knuckle arms, are hardened by quenching and tempering after hot forging. So-called heat-treated forging steel is used to ensure toughness, but due to recent demands for energy saving and cost reduction, it is now possible to use it as is after hot forging without the need for heat treatment. The development of non-thermal forging steel that can be used for forging is progressing. An example of such non-tempered steel is, for example, a medium carbon steel with V added, which is air-cooled after hot forging to create a ferrite-pearlite structure. Some non-tempered steels have come into use (e.g., Japanese Patent Publications No. 58-53709, No. 61-287)
No. 42), hot forged products using such non-tempered steel generally have a problem of poor toughness. The present invention solves the problem of toughness deterioration, which is a drawback of conventional non-thermal treatment steel for hot forging, and ensures excellent toughness and maintains high strength without performing thermal treatment after hot forging. Another object of the present invention is to provide a non-temperature steel for hot forging that enables energy saving and cost reduction during hot forging, which are the advantages of non-temperature steel. (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 80 kgf/
Considering that the problem is that the toughness decreases significantly when the toughness exceeds "mid", we conducted intensive research to investigate the cause and find a new solution.As a result, we found that conventional non-tempered steel After hot forging carbon steel, slow cooling such as air cooling or natural cooling is performed to create a structure of pro-eutectoid ferrite + pearlite, so sufficient strength cannot be obtained. To compensate for the lack of strength, precipitation strengthening is used. However, the toughness of the ferrite + pearlite structure is originally not high enough, and ■
It was found that precipitation strengthening further reduced the toughness. Therefore, the present inventor first developed a low carbon steel (C: 0.04~
0.20%) to ensure a certain level of strength and prevent a decrease in toughness, and further, by directly water cooling after hot forging, it is made into martensite, bainite, or a mixed structure of martensite and bainite, and pro-eutectoid ferrite is created. It has been found that by creating a structure that does not contain Nb, it is possible to improve not only strength but also high toughness due to the refinement of austenite crystal grains by adding Nb. 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 toughness non-temperature steel for hot forging according to the present invention is
C: 0.04-0.20%, Si: 0.05-1.0%
, Mn: 0.8-2.0%, Nb: 0.01-0115
%, Ti: 0.01-0.05%, B: O, 0.000
3 to 0.005% and Al: 0.005 to 0.10%, as necessary, S≦0.15%, Pb≦0.3
0%, Ca≦0.01%, Se≦0.30%, Te≦0
．． 30% and Bi≦0.30%, the remainder substantially consists of Fe, and the main body of the structure obtained by direct water cooling after hot forging is martensite, bainite, or marten. It is characterized by having a mixed structure of site 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 important factor governing strength and toughness, and conventional non-temperature steel for hot forging uses a relatively large amount of C to ensure strength, but this leads to deterioration of toughness. There is. On the other hand, one of the characteristics of the present invention is that it is a low C steel, and by forming a specific structure by water cooling after hot forging,
Focusing on the fact that relatively high strength and toughness can be obtained even with low C, the amount of C is regulated low. but. If the C content is too low, sufficient strength cannot be ensured, so it is required to be 0.04% or more. On the other hand, although increasing the amount of C is effective in increasing strength, it reduces toughness, so it must be kept at 0.20% or less. Therefore, the amount of C is set in the range of 0.04 to 0.20%. Si: Si is an essential element as a deoxidizing agent, and therefore 0
．． 0.05% or more is required. On the other hand, although Si is effective as a reinforcing element, excessive addition of more than 1.0% deteriorates toughness. Therefore, the amount of Si is 0.05 to 1.0
% range. Mn: Mn is an effective element that increases the hardenability of steel.
In order to fully exhibit the strengthening mechanism by C in a low C steel as in the present invention, an amount of Mn of less than 0.8% is insufficient, so it is necessary to add 0.8% or more. However, 2
．． Even if it is added in an amount exceeding 0%, the effect will be small and machinability will deteriorate on the contrary. Therefore, the amount of Mn is 0.8 to 2
．． The range is 0%. Nb: Adding Nb is the most significant feature of the present invention. In other words, Nb is effective in improving toughness because Nb carbonitride prevents austenite crystal grains from becoming coarser. In addition, when heating at a high temperature of 1100°C or higher, N
b dissolves in solid solution in austenite, improves hardenability, and also has the effect of increasing strength. Added amount of Nb is 0.01%
If it is less than 0.15%, the austenite grain refining effect will be small, and if it is more than 0.15%, it is desirable for the above effect. .01~0.15
% range. Ti: T1 is added to fix N in austenite and enhance the hardenability effect of B, but if it is less than 0.01%, the effect is insufficient, so it is required to be 0.01% or more. However, adding more than 0.05% does not increase the effect. Therefore, the amount of Ti is in the range of 0.01 to 0.05%. B: B is an element that increases the hardenability of low C steel and is effective in improving strength and toughness. If the amount added is less than o, o o o a%, there is no effect, while if it is added in excess of more than 0.005%, precipitates of B will be formed and the toughness will deteriorate. Therefore, the amount of B is o, o o. The range is 3 to 0.005%. AQ: Afi is an element that is an effective deoxidizer, is effective in refining austenite crystal grains, and has the effect of improving toughness. In order to improve toughness, it is necessary to add 0.005% or more, but 0.10% or less is sufficient, and 0.10%
Adding more than
The amount of ΔΩ is in the range of 0.005 to 0.10%. The steel of the present invention contains one or more elements as essential components. As explained below, if necessary, an appropriate amount of one or more of s, pb%Ca%Se, Te, and Bi can be added to improve machinability. S, Pb, Ca, Se, Te, Bi: S, Pb, Ca, Se, Te, and Bi are elements that are effective in improving machinability, and can be added singly or in combination. The amounts of these elements to be added are 0.15% or less for S, 0.30% or less for Pb, and 0.01% or less for Ca, considering their influence on the basic properties of steel. Se is 0.30% or less, Te is 0.30% or less, Bi
is 0.30% or less, and if it is within this range, it is considered strong. It does not have a particular effect on toughness, but it goes without saying that when S is added, it is added within the above-mentioned limits in excess of the usual amount of impurities. 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 chemical components is used to manufacture hot forged parts through the same manufacturing process as conventional ones. Hot forging involves heating to a temperature of 900 to 1300'C and forging with a press or the like, and then. cooled down. However, when cooling after hot forging, cooling is performed directly in water or a cooling medium with a cooling ability close to water (in the present invention, these are defined as "water"), and the main structure of the steel is changed to martensite. Alternatively, it is necessary to use bainite or a mixed structure of martensite and bainite. this is,
The martensite, bainite, or mixed structure of these in the low C steel having the above chemical composition has relatively high strength, and can be used without the need for tempering, which is essential for conventional hot forging tempered steels. This is because it was found to have high toughness. In addition, conventional medium-carbon non-heat-treated steel for hot forging has insufficient toughness, and particularly when the tensile strength exceeds 80 kgf/mm, the toughness decreases significantly, but according to the present invention, Because the above structure contains almost no pro-eutectoid ferrite, it is possible to significantly improve toughness and strength, which is equivalent to the strength of conventional heat-treated steel for hot forging. Moreover, since refining treatment is not required, the effect of improving productivity and reducing costs is remarkable.Examples of the present invention are shown below. (Example) Chemical components shown in Table 1 ( wt%) was melted and cast using a conventional method, and rolled to produce a forging material with a diameter of 25 to 50 mm.
Heat to 0-1250°C and then. Directly water cooled. The obtained steel material was examined for hardness (Vickers hardness) and Charpy impact test was conducted at room temperature using a full size test piece with a 2 mm U notch to evaluate toughness. The results are shown in Tables 2 and 3. Also, for some of the steels shown in Table 1, the materials obtained in the same manner were heated to 1000°C or 1200°C, then hot worked (working rate 50°C). %), and then the hardness and toughness of steel materials that were directly water-cooled were examined in the same manner. The result is the fourth
Shown in the table. In addition, Na27 in Table 1 is a heat-treated steel that is conventionally quenched and tempered, and Na28 is a non-heat-treated steel that is air-cooled after hot forging.The hardness and toughness of these were also investigated, and the results were Also listed. As is clear from Tables 2, 3, and 4, as well as Figure 1, which shows the results for some of the test steels, all of the steels of the present invention have excellent strength and toughness, and especially The toughness is significantly improved and the strength is higher than that of the conventional non-tempered steel Nα28, and it has the same strength and toughness as the conventional tempered tlNa27. In addition, when a cutting test was conducted on the steel of the present invention to which elements effective in improving machinability were added, it was confirmed that the steel had excellent machinability.
（発明の効果）
以上詳述したように、本発明に係る熱間鍛造用非調質鋼
は、低Ｃ鋼にて化学成分を調整し、特にＮｂの添加によ
りオーステナイト結晶粒の微細化を図ると共に、熱間鍛
造後直接水冷して得られる組織の主体を低Ｃのマルテン
サイト又はベイナイト或いはマルテンサイトとベーナイ
トの混合組織としたので、従来の非調質鋼に比べて高強
度、高靭性を有し、殊に靭性の改善効果は顕著であり。
しかも従来の調質鋼と同等の強度、靭性を有している。
また、非調質鋼であるため、調質鋼に比べて焼入れ−焼
きもどしの熱処理を省略でき、生産性の向上並びに低コ
スト化の効果が顕著である。(Effects of the Invention) As detailed above, the non-heat-treated steel for hot forging according to the present invention is a low C steel whose chemical composition is adjusted, and in particular, by adding Nb, the austenite grains are refined. At the same time, since the main structure obtained by direct water cooling after hot forging is low C martensite, bainite, or a mixed structure of martensite and bainite, it has higher strength and toughness than conventional non-tempered steel. In particular, the effect of improving toughness is remarkable. Moreover, it has the same strength and toughness as conventional tempered steel. Furthermore, since it is a non-tempered steel, the heat treatment of quenching and tempering can be omitted compared to tempered steel, and the effects of improved productivity and cost reduction are significant.
第１図は本発明鋼（非調質）及び従来１（調質鋼、非調
質鋼）におけるビッカース硬さと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 the Vickers hardness and the Charpy impact value of the steel of the present invention (non-tempered steel) and conventional steel 1 (tempered steel, non-tempered steel).
Claims (2)
０％、Ｓｉ：０．０５〜１．０％、Ｍｎ：０．８〜２０
０％、Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．０１〜
０．０５％、Ｂ：０．０００３〜０．００５％及びＡｌ
：０．００５〜０．１０％を含有し、残部が実質的にＦ
ｅからなり、熱間鍛造後直接水冷して得られる組織の主
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靭
性熱間鍛造用非調質鋼。(1) In weight% (the same applies hereinafter), C: 0.04 to 0.2
0%, Si: 0.05-1.0%, Mn: 0.8-20
0%, Nb: 0.01~0.15%, Ti: 0.01~
0.05%, B: 0.0003-0.005% and Al
: Contains 0.005 to 0.10%, with the remainder being substantially F.
1. A high-toughness non-temperature steel for hot forging, characterized in that the main structure obtained by direct water cooling after hot forging is martensite, bainite, or a mixed structure of martensite and bainite.
．０％、Ｍｎ：０．８〜２．０％、Ｎｂ：０．０１〜０
１１５％、Ｔｉ：０．０１〜０．０５％、Ｂ：０．００
０３〜０．００５％及びＡｌ：０．００５〜０．１０％
を含有し、更にＳ≦０．１５％、Ｐｂ≦０．３０％、Ｃ
ａ≦０．０１％、Ｓｅ≦０．３０％、Ｔｅ≦０．３０％
及びＢｉ≦０．３０％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、熱間鍛造後直接水冷
して得られる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靭性熱間鍛造用非調質鋼。(2) C: 0.04-0.20%, Si: 0.05-1
．． 0%, Mn: 0.8-2.0%, Nb: 0.01-0
115%, Ti: 0.01-0.05%, B: 0.00
03-0.005% and Al: 0.005-0.10%
further contains S≦0.15%, Pb≦0.30%, C
a≦0.01%, Se≦0.30%, Te≦0.30%
and Bi≦0.30%, the remainder substantially consists of Fe, and the main body of the structure obtained by direct water cooling after hot forging is martensite, bainite, or martensite. A high-toughness non-thermal steel for hot forging characterized by a mixed structure of bainite and bainite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14868287A JPS63312949A (en) | 1987-06-15 | 1987-06-15 | Non-refining steel for hot forging having high toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14868287A JPS63312949A (en) | 1987-06-15 | 1987-06-15 | Non-refining steel for hot forging having high toughness |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS63312949A true JPS63312949A (en) | 1988-12-21 |
Family
ID=15458242
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14868287A Pending JPS63312949A (en) | 1987-06-15 | 1987-06-15 | Non-refining steel for hot forging having high toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63312949A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20010066190A (en) * | 1999-12-31 | 2001-07-11 | 이계안 | Martensitic carbon steel and it's manufacture |
| KR100475943B1 (en) * | 2002-04-04 | 2005-03-10 | 현대자동차주식회사 | Method for manufacturing hot-forged parts with high strength and high toughness and hot-forged parts |
| WO2007026515A1 (en) * | 2005-08-29 | 2007-03-08 | Ntn Corporation | Uniform speed universal joint |
Citations (2)
| 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 |
| JPS61238941A (en) * | 1985-04-15 | 1986-10-24 | Kobe Steel Ltd | Untempered steel for hot forging |
-
1987
- 1987-06-15 JP JP14868287A patent/JPS63312949A/en active Pending
Patent Citations (2)
| 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 |
| JPS61238941A (en) * | 1985-04-15 | 1986-10-24 | Kobe Steel Ltd | Untempered steel for hot forging |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20010066190A (en) * | 1999-12-31 | 2001-07-11 | 이계안 | Martensitic carbon steel and it's manufacture |
| KR100475943B1 (en) * | 2002-04-04 | 2005-03-10 | 현대자동차주식회사 | Method for manufacturing hot-forged parts with high strength and high toughness and hot-forged parts |
| WO2007026515A1 (en) * | 2005-08-29 | 2007-03-08 | Ntn Corporation | Uniform speed universal joint |
| JP2007064262A (en) * | 2005-08-29 | 2007-03-15 | Ntn Corp | Constant velocity universal joint |
| JP4562620B2 (en) * | 2005-08-29 | 2010-10-13 | Ｎｔｎ株式会社 | Constant velocity universal joint and method of manufacturing the outer ring of the joint |
| US7942750B2 (en) * | 2005-08-29 | 2011-05-17 | Ntn Corporation | Constant velocity joint |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4702778A (en) | Method for softening rolled medium carbon machine structural steels | |
| US4753691A (en) | Method of directly softening rolled machine structural steels | |
| JPS589813B2 (en) | Manufacturing method for non-thermal forged steel products | |
| US4806178A (en) | Non-heat refined steel bar having improved toughness | |
| JPH01176055A (en) | Non-heat treated steel for hot forging having excellent machinability | |
| JPH1129842A (en) | Ferrite-pearlite type non-heat treated steel | |
| JPS6156235A (en) | Manufacture of high toughness nontemper steel | |
| JP2768062B2 (en) | Manufacturing method of high strength tough steel | |
| JPH11181542A (en) | Steel product for induction hardening, excellent in cold workability and induction hardenability, and its production | |
| JPH01116032A (en) | Production of high-strength-high-toughness un-tempered steel | |
| JPS63312949A (en) | Non-refining steel for hot forging having high toughness | |
| JPS5852458A (en) | Nonquenched and tempered steel with high strength and toughness | |
| JPH01176031A (en) | Manufacture of non-heattreated steel for hot forging | |
| JP2735161B2 (en) | High-strength, high-toughness non-heat treated steel for hot forging | |
| JPH0159333B2 (en) | ||
| JPS582572B2 (en) | Method for manufacturing strong steel bars with little anisotropy | |
| JP3214731B2 (en) | Method for producing non-heat treated steel bar with excellent low temperature toughness | |
| JPH04297548A (en) | High strength and high toughness non-heat treated steel and its manufacture | |
| JPH07310118A (en) | Production of case hardening steel suitable for cold-working | |
| JPH0621319B2 (en) | Non-heat treated steel for hot forging | |
| JPH0213004B2 (en) | ||
| JPS63277721A (en) | Manufacture of rail combining high strength with high toughness | |
| JPH01129953A (en) | High strength non-heat treated steel and its manufacture | |
| JPH10265891A (en) | Ferrite/pearlite type non-heat treated steel | |
| JP3584726B2 (en) | High strength non-heat treated steel |