JPH07118732A - Production of high strength steel for machine structure excellent in cold forgeability - Google Patents

Production of high strength steel for machine structure excellent in cold forgeability

Info

Publication number
JPH07118732A
JPH07118732A JP26355593A JP26355593A JPH07118732A JP H07118732 A JPH07118732 A JP H07118732A JP 26355593 A JP26355593 A JP 26355593A JP 26355593 A JP26355593 A JP 26355593A JP H07118732 A JPH07118732 A JP H07118732A
Authority
JP
Japan
Prior art keywords
steel
cold forgeability
cold
rolling
less
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
Application number
JP26355593A
Other languages
Japanese (ja)
Other versions
JP3371490B2 (en
Inventor
Nobuyuki Ishikawa
信行 石川
Tetsuo Shiragami
哲夫 白神
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Engineering Corp
Original Assignee
NKK Corp
Nippon Kokan Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NKK Corp, Nippon Kokan Ltd filed Critical NKK Corp
Priority to JP26355593A priority Critical patent/JP3371490B2/en
Publication of JPH07118732A publication Critical patent/JPH07118732A/en
Application granted granted Critical
Publication of JP3371490B2 publication Critical patent/JP3371490B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Abstract

PURPOSE:To provide a method for producing a high strength steel for cold forging capable of cold forging as hot-rolled and having excellent deformability and high hardenability. CONSTITUTION:A steel contg., by weight, 0.30 to 0.060% C, <=0.15% Si, 0.20 to 0.50% Mn, <=0.01% S and 2.0 to 3.0% Cr, and the balance Fe with inevitable impurities is subjected to finish rolling at <=1000 deg.C, and its metallic structure after the hot rolling is formed of a ferritic-pearlitic one having <=10%, ferrite areal fraction.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は、熱間圧延ままで冷間鍛
造が可能で、しかも優れた変形能と高い焼入性を有する
冷間鍛造性に優れた機械構造用強靭鋼の製造方法に関す
る。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a tough steel for machine structural use which is capable of cold forging without being hot-rolled and which has excellent deformability and high hardenability and is excellent in cold forgeability. Regarding

【0002】[0002]

【従来の技術】一般に、機械構造用部品は、切削、鍛造
等によって所定の形状に加工された後に、焼入・焼戻し
処理や高周波焼入等の表面硬化処理を施す場合が多い
が、冷間鍛造は製品の寸法精度がよく、また切削加工に
比べ生産性が高いことから、機械部品の製造に広く用い
られている。
2. Description of the Related Art Generally, mechanical structural parts are often subjected to surface hardening treatment such as quenching / tempering treatment or induction hardening after being processed into a predetermined shape by cutting, forging, etc. Forging is widely used for manufacturing machine parts because it has good dimensional accuracy of products and has higher productivity than cutting.

【0003】通常、冷間鍛造に供される機械構造用強靭
鋼は、高い焼入性が要求されることから、JISに規定
されたSCM440等を素材として、軟化焼きなまし処
理により冷間鍛造性を改善したものが使用されている。
しかし、軟化焼きなまし処理には、高温でしかも長時間
の加熱が必要であることから、製造コストの増大と生産
性の低下をまねいており、熱間圧延ままで使用可能な冷
間鍛造用鋼への要求が高まっている。
[0003] Usually, high strength hardenable steel for machine structural use, which is used for cold forging, is required to have high hardenability. Therefore, cold forgeability is improved by softening and annealing using SCM440 or the like specified in JIS as a material. The improved one is used.
However, since softening annealing requires heating at high temperature for a long time, it leads to an increase in manufacturing cost and a decrease in productivity, making it a cold forging steel that can be used as hot rolled. The demand for is increasing.

【0004】また、冷間鍛造により複雑な形状を有する
機械部品を製造する場合は、数回に分けて冷間鍛造を行
う必要があり、製造工程の省略のために、より変形能の
高い冷間鍛造用鋼が望まれている。
Further, when a mechanical part having a complicated shape is manufactured by cold forging, it is necessary to carry out cold forging several times, and because of the omission of the manufacturing process, the cold forging having a higher deformability is performed. Steel for forgings is desired.

【0005】そこで、軟化焼きなまし処理の省略を目的
として、特開平4−228519号公報に記載されたよ
うに、圧延後直ちに鋼材表面を冷却する中間冷却を有
し、その後700〜800℃で圧延を行い、0.05〜
0.7℃/秒で徐冷する方法等が提案されている。
Therefore, for the purpose of omitting the softening / annealing treatment, as described in JP-A-4-228519, there is an intermediate cooling for cooling the surface of the steel material immediately after rolling, and then rolling at 700 to 800 ° C. Done, 0.05 ~
Methods such as slow cooling at 0.7 ° C./second have been proposed.

【0006】また、焼入性を確保した上で、冷間鍛造性
を高めることを目的として、特開平5−59486号公
報や特開昭59−13048号公報に記載されているよ
うに、フェライト強化元素であるSi、Mn、Crを低
減することで変形抵抗を低下させ、焼入性の低下をT
i,Bの添加により補った冷間鍛造用鋼が提案されてい
る。
Further, as described in JP-A-5-59486 and JP-A-59-13048 for the purpose of enhancing the cold forgeability while ensuring the hardenability, ferrite is used. By reducing the strengthening elements Si, Mn, and Cr, the deformation resistance is reduced and the hardenability is reduced by T
Cold forging steel supplemented by the addition of i and B has been proposed.

【0007】[0007]

【発明が解決しようとする課題】しかし、特開平4−2
28519号公報に記載された方法は、製造工程が複雑
になるだけでなく、熱間圧延後の徐冷において、保温カ
バー等の設備が必要となることから、素材コストの上昇
をまねき、またこの方法で得られる冷間鍛造用鋼は、低
温圧延によるフェライト分率の増大により変形抵抗は低
下するが、変形能(割れが発生するまでの限界の圧縮率
で示される)は十分とはいえなかった。
However, Japanese Unexamined Patent Publication (Kokai) No. 4-2.
The method described in Japanese Patent No. 28519 not only complicates the manufacturing process, but also requires equipment such as a heat insulating cover in gradual cooling after hot rolling, which leads to an increase in material cost. The cold forging steel obtained by the method has a low deformation resistance due to an increase in the ferrite fraction due to low temperature rolling, but the deformability (indicated by the limit compressibility until cracking) is not sufficient. It was

【0008】また、特開平5−59486号公報や特開
昭59−13048号公報に記載された方法では、得ら
れる冷間鍛造用鋼は、フェライト強化元素であるSi、
Mn、の低減により変形抵抗が低下し、冷間鍛造性に優
れているが、軟化焼きなまし処理を前提としたものであ
るため熱間圧延のままでは冷間鍛造性が劣り、また軟化
焼きなまし処理を施しても変形能は十分ではなかった。
本発明の目的は、熱間圧延ままで冷間鍛造が可能で、し
かも優れた変形能と高い焼入性を有する冷間鍛造用強靭
鋼の製造方法を提供するものである。
Further, in the method described in JP-A-5-59486 and JP-A-59-13048, the cold forging steel obtained is Si, which is a ferrite strengthening element,
Deformation resistance decreases due to the reduction of Mn, and it is excellent in cold forgeability, but since it is premised on softening annealing treatment, cold forgingability is inferior in hot rolling as it is, and softening annealing treatment is performed. Even if it was applied, the deformability was not sufficient.
An object of the present invention is to provide a method for producing a tough steel for cold forging, which can be cold forged as hot-rolled and has excellent deformability and high hardenability.

【0009】[0009]

【課題を解決するための手段】本発明者らは、熱間圧延
後の金属組織と冷間鍛造性の関係を詳細に研究した結
果、冷間鍛造性、特に変形能を高めるにはフェライト−
パ−ライト鋼においてはフェライト分率の低減が効果が
大きいとの知見を得るに至った。
As a result of detailed research on the relationship between the metal structure after hot rolling and the cold forgeability, the present inventors have found that ferrite-
In pearlite steel, we have come to the knowledge that the reduction of the ferrite fraction has a great effect.

【0010】熱間圧延後の強度を低下させるためにはフ
ェライト分率の増加が有効であるが、軟質なフェライト
相は微少クラックの伝播経路となり、割れが発生する限
界の圧縮率、すなわち変形能を低下させる原因となる。
よって、微少クラックの伝播を防ぐためにはCrを多量
添加してフェライト分率を低下すればよく、フェライト
分率の低下によって変形能が著しく向上する。また、C
rの多量添加によって冷間鍛造後の焼入・焼戻し処理や
高周波焼入等の表面効果処理における焼入性の向上も同
時に可能となるものである。
To reduce the strength after hot rolling, it is effective to increase the ferrite fraction, but the soft ferrite phase serves as a propagation path for minute cracks, and the compressibility at the limit of cracking, that is, the deformability. Cause to decrease.
Therefore, in order to prevent the propagation of minute cracks, a large amount of Cr may be added to reduce the ferrite fraction, and the deformability is significantly improved by the reduction of the ferrite fraction. Also, C
By adding a large amount of r, it is possible to improve the hardenability at the time of quenching / tempering after cold forging and surface effect treatment such as induction hardening.

【0011】しかし、Crを多量添加すると、熱間圧延
ままの組織でベーナイトが生成し、冷間鍛造性が低下す
ることになる。そこで、低温圧延による結晶微細化によ
り・フェライト・パーライト変態を促進させることでベ
ーナイトの生成を抑制し、熱間圧延後の組織が微細なパ
ーライトを主体としたフェライト・パーライト組織とす
ることが可能となる。
However, when a large amount of Cr is added, bainite is formed in the as-hot-rolled structure, and cold forgeability is deteriorated. Therefore, it is possible to suppress the formation of bainite by accelerating the ferrite-pearlite transformation by refining the crystal by low-temperature rolling, and to make the structure after hot rolling a ferrite-pearlite structure mainly composed of fine pearlite. Become.

【0012】本発明は以上の知見に基いてなされたもの
で、第一発明は、重量%で、C:0.30〜0.60
%、Si:0.15%以下、Mn:0.20〜0.50
%、S:0.01%以下、Cr:2.0〜3.0%を含
有し、残部がFe及び不可避不純物からなる鋼を、10
00℃以下の温度で仕上げ圧延を行うことを特徴とする
冷間鍛造性に優れた機械構造用強靭鋼の製造方法であ
り、第二発明は、重量%で、C:0.30〜0.60
%、Si:0.15%以下、Mn:0.20〜0.50
%、S:0.01%以下、Cr:2.0〜3.0%、T
i:0.01〜0.03%、B:0.0005〜0.0
030%を含有し、残部がFe及び不可避不純物からな
る鋼を、1000℃以下の温度で仕上げ圧延を行うこと
を特徴とする冷間鍛造性に優れた機械構造用強靭鋼の製
造方法である。
The present invention has been made on the basis of the above findings. The first invention, in% by weight, is C: 0.30 to 0.60.
%, Si: 0.15% or less, Mn: 0.20 to 0.50
%, S: 0.01% or less, Cr: 2.0 to 3.0%, with the balance being Fe and inevitable impurities.
A second aspect of the present invention is a method for producing a tough steel for machine structural use having excellent cold forgeability, which comprises performing finish rolling at a temperature of 00 ° C. or less. 60
%, Si: 0.15% or less, Mn: 0.20 to 0.50
%, S: 0.01% or less, Cr: 2.0 to 3.0%, T
i: 0.01 to 0.03%, B: 0.0005 to 0.0
A method for producing a tough steel for machine structural use having excellent cold forgeability, which comprises performing finish rolling of a steel containing 030% and the balance being Fe and unavoidable impurities at a temperature of 1000 ° C or less.

【0013】[0013]

【作用】本発明における限定理由を説明する。まず成分
限定理由は以下の通りである。 (1) C:0.30〜0.60重量%(以下%は重量%を
示す) Cは冷間鍛造後の焼入・焼戻し処理又は各種表面硬化熱
処理による表面硬さを確保するために必要な元素であ
る。0.3%未満では必要な硬さが得られず、0.60
%を超えると冷間鍛造後の熱処理で焼割れの原因になる
ため、0.30〜0.60%の含有とする。
The reason for limitation in the present invention will be described. First, the reasons for limiting the components are as follows. (1) C: 0.30 to 0.60% by weight (hereinafter% indicates% by weight) C is necessary to secure surface hardness by quenching / tempering treatment after cold forging or various surface hardening heat treatments. Is an element. If it is less than 0.3%, the required hardness cannot be obtained and 0.60
%, It causes quench cracking in the heat treatment after cold forging, so the content is made 0.30 to 0.60%.

【0014】(2) Si:0.15%以下 Siは脱酸材として必要であるが、0.15%を越える
とフェライトに固溶し変形抵抗を高め冷間鍛造性を劣化
させるため、上限を0.15%とする。
(2) Si: 0.15% or less Si is necessary as a deoxidizing material, but if it exceeds 0.15%, it forms a solid solution with ferrite to increase the deformation resistance and deteriorate the cold forgeability. Is 0.15%.

【0015】(3) Mn:0.20〜0.50% Mnは強度を確保し、また焼入性を向上させるため必要
な元素である。しかし0.20%未満ではその効果が不
十分で、0.50%を超えるとSiと同様に変形抵抗を
高め冷間鍛造性を劣化させるため、0.20〜0.50
%の含有とする。
(3) Mn: 0.20 to 0.50% Mn is an element necessary for securing strength and improving hardenability. However, if it is less than 0.20%, the effect is insufficient, and if it exceeds 0.50%, the deformation resistance is increased and the cold forgeability is deteriorated similarly to Si, so 0.20 to 0.50.
% Is included.

【0016】(4) S:0.01%以下 Sは変形能に悪影響を与えるMnSを形成するため少な
いほどよいが、0.01%以下であれば実用上問題は生
じないので0.01%以下とする。
(4) S: 0.01% or less Since S forms MnS which adversely affects the deformability, the smaller the content, the better. However, if the content is 0.01% or less, practically no problem occurs, so 0.01%. Below.

【0017】(5) Cr:2.0〜3.0% Crは焼入性を向上する元素であり、またパ−ライト変
態温度を上昇させることでフェライト分率を低下させ、
且つパーライトラメラ間隔を狭める元素である。しか
し、2.0%未満の含有ではこれらの効果が不十分で十
分な焼入性が得られず、3.0%を超えて含有すると低
温圧延によってもベイナイトを生成し冷間鍛造性を低下
させるので、2.0〜3.0%の含有とする。
(5) Cr: 2.0 to 3.0% Cr is an element for improving hardenability, and the ferrite fraction is lowered by increasing the pearlite transformation temperature.
It is also an element that narrows the pearlite lamella spacing. However, if the content is less than 2.0%, these effects are insufficient and sufficient hardenability cannot be obtained, and if the content exceeds 3.0%, bainite is generated even at low temperature rolling and cold forgeability is deteriorated. Therefore, the content is set to 2.0 to 3.0%.

【0018】(6) 本発明は、冷間鍛造後に行う焼入・焼
戻し処理において焼入性を高めるために上記成分にさら
にTi:0.01〜0.03%、B:0.0005〜
0.0030%を含有することができる。
(6) In the present invention, Ti: 0.01 to 0.03%, B: 0.0005 to the above components in order to enhance the hardenability in the quenching and tempering treatment performed after cold forging.
It can contain 0.0030%.

【0019】Ti:0.01〜0.03% Tiは鋼中のNをTiNとして固定しBの焼入れ性向上
効果を確保するために添加する。Nを固定するためには
0.01%以上の含有が必要であるが、0.03%を超
えて含有させてもその効果は飽和するため、0.01〜
0.03%の含有とする。
Ti: 0.01 to 0.03% Ti is added to fix N in the steel as TiN and to secure the effect of improving the hardenability of B. In order to fix N, it is necessary to contain 0.01% or more, but even if the content exceeds 0.03%, the effect is saturated, so 0.01-
The content is 0.03%.

【0020】B:0.0005〜0.0030% BはTiと組み合わせて添加することにより焼入れ性を
著しく向上させる元素であるが、効果を発揮するには
0.0005%以上の含有が必要である。しかし0.0
030%を超えるとその効果は飽和するため、0.00
05〜0.0030%の含有とする。
B: 0.0005 to 0.0030% B is an element that improves the hardenability remarkably when added in combination with Ti, but 0.0005% or more is required to exert the effect. is there. But 0.0
If it exceeds 030%, the effect is saturated, so 0.00
The content is set to 05 to 0.0030%.

【0021】なお本発明鋼には脱酸の目的で添加される
Al、不可避的に存在するPなどを含有してもよく、こ
れらの含有により本発明の目的とする性能が損なわれる
ものではない。
The steel of the present invention may contain Al, which is added for the purpose of deoxidation, and P, which is inevitably present, and the inclusion thereof does not impair the intended performance of the present invention. .

【0022】つぎに、仕上げ圧延温度の限定理由につい
て説明する。 (7) 仕上げ圧延温度:1000℃以下 本発明に係る鋼は、Crを多量に含有する鋼であり、1
000℃を越える温度で仕上げ圧延を行なうと、熱間圧
延後の組織がベーナイトとなり、冷間鍛造性が低下す
る。このため仕上げ圧延温度の上限を1000℃とし
た。
Next, the reason for limiting the finish rolling temperature will be described. (7) Finish rolling temperature: 1000 ° C. or less The steel according to the present invention is a steel containing a large amount of Cr, and 1
When finish rolling is performed at a temperature exceeding 000 ° C., the structure after hot rolling becomes bainite and cold forgeability deteriorates. Therefore, the upper limit of the finish rolling temperature is set to 1000 ° C.

【0023】本発明鋼の製造法としては、上に述べた成
分範囲に溶製した鋼を熱間圧延により棒鋼に製造する。
熱間圧延においては特開昭62−196327号公報、
特開平4−228519号公報のような低温圧延や圧延
時に中断冷却を行うことは必要とせず、ごく一般的な熱
間圧延でかまわない。
As the method for producing the steel of the present invention, the steel melted in the above-mentioned composition range is manufactured into a steel bar by hot rolling.
In hot rolling, JP-A-62-196327,
It is not necessary to perform low-temperature rolling as described in Japanese Patent Laid-Open No. 4-228519 or interruption cooling at the time of rolling, and a very general hot rolling may be used.

【0024】本発明方法で得られる機械構造用強靭鋼
は、フェライトの面積分率が小さく、通常10%以下で
ある。このことにより、冷間鍛造時の割れの発生を阻止
して、変形能を向上することができる。
The tough steel for machine structural use obtained by the method of the present invention has a small area fraction of ferrite, usually 10% or less. This can prevent the occurrence of cracks during cold forging and improve the deformability.

【0025】[0025]

【実施例】次に、本発明の実施例について説明する。供
試鋼は表1に示す成分組成の鋼を溶製し、熱間圧延によ
り直径55mmの丸棒を製造した。熱間圧延での仕上げ
温度は950℃(本発明方法)と1050℃(比較方
法)で行なった(表2参照)。
EXAMPLES Next, examples of the present invention will be described. As the test steel, the steel having the chemical composition shown in Table 1 was melted and hot rolled to manufacture a round bar having a diameter of 55 mm. The finishing temperature in hot rolling was 950 ° C. (inventive method) and 1050 ° C. (comparative method) (see Table 2).

【0026】これら圧延ままの丸棒から機械加工により
切り出した試験片を用いて冷間鍛造性を評価した。試験
片形状は図1に示すように直径14mm、高さ21mm
の円筒型で、上下面に拘束溝及び側面にV溝を有する切
欠き付円筒試験片である。図1において(a)は上面
図、(b)は側面図で1はV字状の溝、2は被圧縮面、
(c)はV字状の溝の詳細寸法を示す。
Cold forgeability was evaluated using test pieces cut out from these as-rolled round bars by machining. The shape of the test piece is 14mm in diameter and 21mm in height as shown in FIG.
Is a cylindrical test piece with a notch, which has restraint grooves on the upper and lower surfaces and V grooves on the side surfaces. In FIG. 1, (a) is a top view, (b) is a side view, 1 is a V-shaped groove, 2 is a compressed surface,
(C) shows detailed dimensions of the V-shaped groove.

【0027】冷間鍛造性の評価はこの試験片の上下面を
拘束した状態で被圧縮面に圧縮荷重を加えて圧縮試験を
行い、変形能と変形抵抗を測定した。変形能は、V溝1
の溝底から割れが発生するまでの最大圧縮率(限界圧縮
率と呼ぶ)で評価し、変形抵抗は圧縮率30%のときの
変形荷重(30%変形抵抗と呼ぶ)で評価した。焼入性
試験は直径30mmの試験片に高周波焼入・焼戻しを実
施して表面硬度(表層より2mmの位置)を測定した。
No.10(従来鋼)については、1050℃で熱間圧
延をし、760℃で6時間保持後炉冷の軟化焼きなまし
処理をおこない、上記と同様の試験をおこなった。これ
らの試験結果を表2にまとめて示す。
The cold forgeability was evaluated by applying a compressive load to the surface to be compressed while restraining the upper and lower surfaces of the test piece, and performing a compression test to measure the deformability and the deformation resistance. Deformability is V groove 1
The maximum compression ratio (called the limit compression ratio) from the groove bottom to the occurrence of cracking was evaluated, and the deformation resistance was evaluated by the deformation load (called 30% deformation resistance) when the compression ratio was 30%. In the hardenability test, a test piece having a diameter of 30 mm was subjected to induction hardening / tempering to measure the surface hardness (a position 2 mm from the surface layer).
No. 10 (conventional steel) was hot-rolled at 1050 ° C., held at 760 ° C. for 6 hours, then subjected to furnace-cooling softening annealing treatment, and the same test as above was performed. The results of these tests are summarized in Table 2.

【0028】表2から分かるように、No.1〜4(本
発明方法)はすべてフェライト面積分率が10%以下の
フェライト・パーライト組織となっており、No.9及
びNo.10(JIS規格SCr440及びSCM44
0相当の従来鋼)の圧延材に比べ変形抵抗は同程度であ
るが、限界圧縮率が著しく高くなっており、高周波焼入
・焼戻し後の表面硬さも高くなっている。またNo.1
0の軟化焼きなまし処理材と比べても限界圧縮性が著し
く高い。このことから本発明による鋼は熱間圧延のまま
で冷間鍛造性に優れており、且つ高い焼入性があること
が分かる。
As can be seen from Table 2, No. Nos. 1 to 4 (the method of the present invention) all have a ferrite / pearlite structure with a ferrite area fraction of 10% or less. 9 and No. 10 (JIS standard SCr440 and SCM44
Although the deformation resistance is similar to that of the rolled material of conventional steel (corresponding to 0), the critical compressibility is remarkably high and the surface hardness after induction hardening / tempering is also high. In addition, No. 1
Even when compared with the softened and annealed material of 0, the critical compressibility is remarkably high. From this, it can be seen that the steel according to the present invention is excellent in cold forgeability as hot rolled and has high hardenability.

【0029】なお、No.5(比較鋼)の950℃圧延
材は、Cr含有量が本発明範囲を越えているために圧延
後の組織がベーナイトとなり、限界圧縮率が低く、変形
抵抗が大きくなっている。No.6(比較鋼)の950
℃圧延材は冷間鍛造性はよいが、Cr含有量が本発明範
囲より低いため、高周波焼入・焼戻し後の硬さが低く、
焼入性が不足している。No7(比較鋼)の950℃圧
延材はS含有量が多いため、MnSの量も多くなり、限
界圧縮率が低下している。No.8(比較鋼)の950
℃圧延材はSi含有量が多いため、変形抵抗が高くなっ
ている。また、No.1及びNo.2(本発明鋼)を1
050℃(本発明を越える仕上げ圧延温度)で仕上げ圧
延を行なったものは、圧延後の組織がベーナイトとな
り、限界圧縮率が低く、変形抵抗は大きくなっている。
No.5(比較鋼)の1050℃圧延材は、Cr含有量
が本発明範囲を越えているために950℃圧延材と同様
に圧延後の組織がベーナイトとなり、限界圧縮率が低
く、変形抵抗が大きくなっている。No.6(比較鋼)
の1050℃圧延材は、950℃圧延材と同様に冷間鍛
造性はよいが、Cr含有量が本発明範囲より低いため、
高周波焼入・焼戻し後の硬さが低くなっている。
No. In the 950 ° C rolled material of No. 5 (comparative steel), the Cr content exceeds the range of the present invention, so the structure after rolling becomes bainite, the critical compressibility is low, and the deformation resistance is large. No. 6 (Comparative Steel) 950
The ℃ rolled material has good cold forgeability, but since the Cr content is lower than the range of the present invention, the hardness after induction hardening / tempering is low,
Hardenability is insufficient. Since the No. 7 (comparative steel) 950 ° C. rolled material has a large S content, the amount of MnS also increases and the critical compressibility decreases. No. 8 (Comparative Steel) 950
Since the ℃ rolled material has a high Si content, the deformation resistance is high. In addition, No. 1 and No. 2 (inventive steel) 1
In the case of finish rolling at 050 ° C. (finish rolling temperature exceeding the present invention), the structure after rolling becomes bainite, the critical compressibility is low, and the deformation resistance is large.
No. The 1050 ° C. rolled material of No. 5 (comparative steel) had a Cr content exceeding the range of the present invention, so that the structure after rolling became bainite like the 950 ° C. rolled material, the critical compressibility was low, and the deformation resistance was large. Has become. No. 6 (comparative steel)
The 1050 ° C. rolled material of No. 1 has good cold forgeability like the 950 ° C. rolled material, but since the Cr content is lower than the range of the present invention,
Hardness after induction hardening and tempering is low.

【0030】[0030]

【発明の効果】以上説明したように、本発明によれば熱
間圧延ままで従来鋼に比べ著しく冷間鍛造性が優れ且つ
高い焼入性を有する鋼を提供でき、工業上非常に有用な
発明である。
As described above, according to the present invention, it is possible to provide a steel which has excellent cold forgeability and high hardenability as hot rolled as compared with the conventional steel, and is industrially very useful. It is an invention.

【0031】[0031]

【表1】 [Table 1]

【0032】[0032]

【表2】 [Table 2]

【図面の簡単な説明】[Brief description of drawings]

【図1】冷間鍛造性評価のために使用した切欠き付き円
筒試験片形状を示す図で、(a)は上面図、(b)は側
面図、(c)はV字状の溝の詳細寸法を示す図。
FIG. 1 is a view showing a shape of a cylindrical test piece with a notch used for evaluation of cold forgeability. (A) is a top view, (b) is a side view, and (c) is a V-shaped groove. The figure which shows a detailed dimension.

【符号の説明】[Explanation of symbols]

1…V字状の溝、2…被圧縮面 1 ... V-shaped groove, 2 ... compressed surface

Claims (2)

【特許請求の範囲】[Claims] 【請求項1】重量%で、C:0.30〜0.60%、S
i:0.15%以下、Mn:0.20〜0.50%、
S:0.01%以下、Cr:2.0〜3.0%を含有
し、残部がFe及び不可避不純物からなる鋼を、100
0℃以下の温度で仕上げ圧延を行うことを特徴とする冷
間鍛造性に優れた機械構造用強靭鋼の製造方法。
1. C: 0.30 to 0.60% by weight, S
i: 0.15% or less, Mn: 0.20 to 0.50%,
Steel containing S: 0.01% or less, Cr: 2.0 to 3.0%, and the balance being Fe and inevitable impurities is 100
A method for producing a tough steel for machine structural use, which is excellent in cold forgeability, characterized in that finish rolling is performed at a temperature of 0 ° C or lower.
【請求項2】重量%で、C:0.30〜0.60%、S
i:0.15%以下、Mn:0.20〜0.50%、
S:0.01%以下、Cr:2.0〜3.0%、Ti:
0.01〜0.03%、B:0.0005〜0.003
0%を含有し、残部がFe及び不可避不純物からなる鋼
を、1000℃以下の温度で仕上げ圧延を行うことを特
徴とする冷間鍛造性に優れた機械構造用強靭鋼の製造方
法。
2. By weight%, C: 0.30 to 0.60%, S
i: 0.15% or less, Mn: 0.20 to 0.50%,
S: 0.01% or less, Cr: 2.0 to 3.0%, Ti:
0.01-0.03%, B: 0.0005-0.003
A method for producing a tough steel for machine structural use, which is excellent in cold forgeability, characterized in that the steel containing 0% and the balance being Fe and unavoidable impurities is subjected to finish rolling at a temperature of 1000 ° C or lower.
JP26355593A 1993-10-21 1993-10-21 Method of manufacturing tough steel for machine structure with excellent cold forgeability Expired - Fee Related JP3371490B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP26355593A JP3371490B2 (en) 1993-10-21 1993-10-21 Method of manufacturing tough steel for machine structure with excellent cold forgeability

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Application Number Priority Date Filing Date Title
JP26355593A JP3371490B2 (en) 1993-10-21 1993-10-21 Method of manufacturing tough steel for machine structure with excellent cold forgeability

Publications (2)

Publication Number Publication Date
JPH07118732A true JPH07118732A (en) 1995-05-09
JP3371490B2 JP3371490B2 (en) 2003-01-27

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Country Status (1)

Country Link
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0867521A1 (en) * 1997-03-26 1998-09-30 Imatra Steel Oy Ab Steel for cold forging and a method using the steel
JP2010236005A (en) * 2009-03-31 2010-10-21 Jfe Steel Corp Steel for machine structure excellent in cold forgeability and method of manufacturing the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0867521A1 (en) * 1997-03-26 1998-09-30 Imatra Steel Oy Ab Steel for cold forging and a method using the steel
JP2010236005A (en) * 2009-03-31 2010-10-21 Jfe Steel Corp Steel for machine structure excellent in cold forgeability and method of manufacturing the same

Also Published As

Publication number Publication date
JP3371490B2 (en) 2003-01-27

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