JP2000119809A - Steel wire capable of rapid spheroidizing and excellent in cold forgeability, and its manufacture - Google Patents

Steel wire capable of rapid spheroidizing and excellent in cold forgeability, and its manufacture

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Publication number
JP2000119809A
JP2000119809A JP29107998A JP29107998A JP2000119809A JP 2000119809 A JP2000119809 A JP 2000119809A JP 29107998 A JP29107998 A JP 29107998A JP 29107998 A JP29107998 A JP 29107998A JP 2000119809 A JP2000119809 A JP 2000119809A
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Japan
Prior art keywords
steel wire
less
cold
vpf
sec
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JP29107998A
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Japanese (ja)
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JP3742232B2 (en
Inventor
Hiroshi Kako
浩 家口
Hideo Hatake
英雄 畠
Original Assignee
Kobe Steel Ltd
株式会社神戸製鋼所
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Priority to JP29107998A priority Critical patent/JP3742232B2/en
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Abstract

PROBLEM TO BE SOLVED: To provide a steel wire capable of combinedly attaining rapid spheroidizing before cold forging and excellent cold forgeability improved in deformability, and to provide a useful method for manufacturing it. SOLUTION: In a hot rolled steel wire rod or a cold drawn steel wire, containing, by mass, 0.2-0.6% C, <=0.3% Si, and 0.2-1.5% Mn, a structure composed essentially of pro-eutectoid ferrite and pearlite is provided. Moreover, average grain size is regulated to 6-15 μm. Further, the ratio of pro-eutectoid ferrite volume ratio (Vf) to equilibrium pro-eutectoid ferrite volume ratio (Vpf1) represented by equation Vpf1=(0.8-Ceq1)×129, Vf/Vpf1, is regulated to 0.05-0.75. In the equation, Ceq1(%)=[C%]+0.10[Si%]+0.06[Mn%] is satisfied and also [C%], [Si%], and [Mn%] represent respective contents (mass%) of C, Si, and Mn, respectively.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【0001】[0001]
【発明の属する技術分野】本発明は、中炭素鋼や低合金
鋼を球状化焼鈍後に冷間鍛造により部品に加工される様
な鋼線材およびその製造方法に関し、殊に球状化焼鈍の
際に迅速球状化が可能で冷間鍛造性にも優れた鋼線材、
およびその様な鋼線材を製造する為の有用な方法に関す
るものである。尚本発明で対象とする鋼線材は、主に熱
間圧延によって作られ、通常9.0mmφ以下の断面の
丸い鋼材をコイル状にしたものを意味するが、直径9.
5mmφ以上の棒鋼をコイル状に巻き取った「バーイン
コイル」をも含むものである。また熱間圧延した後に冷
間伸線した鋼線材も含む趣旨である。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire rod in which a medium carbon steel or a low alloy steel is processed into parts by cold forging after spheroidizing annealing, and a method of manufacturing the same. A steel wire rod that can be rapidly spheroidized and has excellent cold forgeability.
And a useful method for producing such a steel wire. Note that the steel wire rod to be used in the present invention is mainly made by hot rolling, and usually means a round steel rod having a cross section of 9.0 mmφ or less, and has a diameter of 9.10 mm.
It also includes a "bar-in-coil" in which a steel bar having a diameter of 5 mm or more is wound into a coil shape. It is also intended to include a steel wire rod that has been cold drawn after hot rolling.
【0002】[0002]
【従来の技術】鋼材を冷間で加工する冷間鍛造は、生産
性が高いことから幅広い分野で利用されている。冷間鍛
造に供される素材は、局部的に激しい変形を受けるため
に、材料割れによる不良の発生や、工具ダイスの破損な
どの事故が起こりやすい。こうしたことから、比較的高
硬度で成形性の悪い中炭素鋼や低合金鋼を素材として冷
間鍛造する場合には、冷間加工性を向上させるために鋼
中の炭化物を球状化するための球状化焼鈍が行なわれる
のが一般的である。
2. Description of the Related Art Cold forging for cold working of steel is widely used in various fields because of its high productivity. Since the material subjected to cold forging is locally severely deformed, accidents such as occurrence of defects due to material cracking and breakage of tool dies are likely to occur. Therefore, when cold forging is performed using a medium-carbon steel or a low-alloy steel with relatively high hardness and low formability, it is necessary to spheroidize carbides in steel to improve cold workability. Generally, spheroidizing annealing is performed.
【0003】上記の様な球状化焼鈍を施すことによっ
て、鋼材の変形能の向上が図れると共に、ダイス寿命の
延伸に効果がある変形抵抗低減が達成されるのである
が、球状化焼鈍は10〜50時間と長時間を要する処理
であることが知られており、迅速に球状化が可能な素材
が求められているのが実状である。またこうした迅速球
状化を行なう際には、球状化焼鈍処理における基本的な
機能である優れた冷間鍛造性を得ること、特に変形能を
劣化させないことが重要な要件である。
[0003] By performing spheroidizing annealing as described above, it is possible to improve the deformability of the steel material and to reduce the deformation resistance that is effective in extending the life of the die. It is known that the process requires a long time as long as 50 hours, and in fact, a material capable of rapidly spheroidizing is demanded. When performing such rapid spheroidization, it is an important requirement to obtain excellent cold forgeability, which is a basic function in the spheroidizing annealing, and not to deteriorate the deformability.
【0004】鋼材の迅速球状化に関する技術はこれまで
にも様々開発されており、例えば特公昭56−3728
8号や同59−35410号等には、球状化処理前の組
織を硬質相のマルテンサイトやベイナイトにする方法が
提案されている。これらの方法によれば、比較的短時間
に球状化が達成されるのであるが、球状化焼鈍後も鋼材
の硬度が低くならずに変形抵抗が高く、工具ダイスの寿
命低下という問題は依然として解消されない。
Various techniques relating to rapid spheroidization of steel have been developed so far, for example, Japanese Patent Publication No. 56-3728.
No. 8, No. 59-35410 and the like propose a method of converting the structure before spheroidizing treatment to a hard phase of martensite or bainite. According to these methods, spheroidization can be achieved in a relatively short time. However, even after spheroidizing annealing, the hardness of the steel material does not decrease, the deformation resistance is high, and the problem of shortening the life of the tool die is still solved. Not done.
【0005】またフェライト・パーライト組織で微細化
を図り迅速球状化を狙う手段がいくつか開示されている
が、十分な効果が得られているとは言い難い。例えば特
公昭63−45441号、特公平2−6809号、特開
昭60−255922等には、熱間圧延時の塑性歪を残
したまま変態させて、迅速球状化させる技術が開示され
ている。しかしながらこれらの技術では、迅速球状化は
達成できても、変態後の組織は圧延方向に展伸されてい
るので、変形能はむしろ劣化している。
[0005] In addition, although there are disclosed several means for achieving a fine spheroid with a ferrite-pearlite structure to achieve a rapid spheroidization, it is hard to say that a sufficient effect has been obtained. For example, JP-B-63-45441, JP-B-2-6809, and JP-A-60-255922 disclose a technique for rapidly spheroidizing by transforming while retaining plastic strain during hot rolling. . However, with these techniques, even though rapid spheroidization can be achieved, the deformability is rather deteriorated because the transformed structure is expanded in the rolling direction.
【0006】更に、特開昭62−139817号や同6
3−20419号では、フェライト粒径を5〜6μm以
下とすることで迅速球状化を図っているが、このように
前組織を超微細化すると、硬さを十分に低下させるのに
却って長時間の球状化時間が必要となり、本発明が想定
する迅速球状化条件(処理時間5〜15時間程度)で
は、むしろ変形抵抗が高く工具寿命が低下する問題があ
る。
Further, Japanese Patent Application Laid-Open No. Sho 62-139817 and
In No. 3-20419, rapid spheroidization is achieved by reducing the ferrite particle size to 5 to 6 μm or less. However, if the prestructure is made ultrafine, it takes a long time to sufficiently reduce the hardness. Spheroidization time is required, and the rapid spheroidization condition (processing time of about 5 to 15 hours) assumed by the present invention has a problem that the deformation resistance is rather high and the tool life is shortened.
【0007】一方、特開昭47−8503号において
は、最終圧延後の冷却において、初析フェライトの生成
を抑制するに足る速さで冷却することで迅速球状化を図
っている。しかしながら、初析フェライトを極端に抑制
すると、硬質相であるパーライトやベイナイトの量が増
大し、圧延後の硬さ上昇が問題となるだけでなく、球状
化焼鈍後も硬さ低下が不十分となる。従って、本発明が
想定している迅速球状化条件では、変形抵抗が高く工具
寿命の低下の問題がある。
On the other hand, in JP-A-47-8503, rapid spheroidization is achieved by cooling after final rolling at a speed sufficient to suppress the formation of proeutectoid ferrite. However, when proeutectoid ferrite is extremely suppressed, the amount of pearlite and bainite, which are hard phases, increases, and not only is the hardness increase after rolling problematic, but also the hardness decrease after spheroidizing annealing is insufficient. Become. Therefore, under the rapid spheroidizing condition assumed by the present invention, there is a problem that the deformation resistance is high and the tool life is shortened.
【0008】また、例えば特公平2−6809号で開示
されている一般的な圧延終了後の冷却速度である0.1
5〜10℃/秒では、初析フェライトとパーライトを主
体とする組織となるが、必要な初析フェライト量を規定
した技術はこれまで提案されていない。即ち、これまで
の技術では、同一コイル内または異なったコイル間で初
析セメンタイト量を一定とすることを想定したものでは
なく、その結果として鋼線材中の球状化程度が異なるこ
とが多かった。そして冷間鍛造時の変形能が最も悪い場
所で全体の変形能が律速されるので、組織のばらつき
は、冷間鍛造時の変形能の低下を意味する。
Further, for example, a cooling rate of 0.1 after the end of the general rolling disclosed in Japanese Patent Publication No. 2-6809 is 0.1.
At 5 to 10 ° C./sec, a structure mainly composed of pro-eutectoid ferrite and pearlite is formed, but no technique has been proposed so far in which a necessary amount of pro-eutectoid ferrite is regulated. That is, the conventional techniques do not assume that the amount of proeutectoid cementite is constant in the same coil or between different coils, and as a result, the degree of spheroidization in the steel wire is often different. And, since the entire deformability is rate-determined at the place where the deformability during cold forging is the worst, the variation in the structure means a decrease in the deformability during cold forging.
【0009】[0009]
【発明が解決しようとする課題】本発明はこうした状況
の下でなされたものであって、その目的は、冷間鍛造前
の迅速球状化と、変形能を向上して優れた冷間鍛造性を
併せて実現することができる鋼線材、およびその為の有
用な方法を提供するものである。
DISCLOSURE OF THE INVENTION The present invention has been made under such a circumstance, and aims at rapid spheroidization before cold forging and excellent cold forgeability by improving deformability. And a useful method therefor.
【0010】[0010]
【課題を解決するための手段】上記目的を達成し得た本
発明の鋼線材とは、C:0.2〜0.6%、Si:0.
3%以下、Mn:0.2〜1.5%を夫々含む熱間圧延
鋼線材または冷間伸線された鋼線材において、初析フェ
ライトとパーライトを主体とする組織を有すると共に、
平均結晶粒径が6〜15μmであり、且つ下記(1)式
で表される平衡初析フェライト体積率(Vpf1 )に対
する初析フェライト体積率Vfの比(Vf/Vpf1
が0.05〜0.75である点に要旨を有するものであ
る。 Vpf1 =(0.8−Ceq1)×129 …(1) 但し、Ceq1(%)=[C%]+0.10[Si%]
+0.06[Mn%]であり、[C%]、[Si%]お
よび[Mn%]は、夫々C、SiおよびMnの含有量
(質量%)を示す。
The steel wire of the present invention, which has achieved the above object, is as follows: C: 0.2 to 0.6%;
A hot-rolled steel wire or a cold-drawn steel wire containing 3% or less and Mn: 0.2 to 1.5%, respectively, having a structure mainly composed of proeutectoid ferrite and pearlite,
The average crystal grain size is 6 to 15 μm, and the ratio (Vf / Vpf 1 ) of the volume fraction of pro-eutectoid ferrite Vf to the volume fraction of equilibrium pro-eutectoid ferrite (Vpf 1 ) represented by the following formula ( 1 ).
Is in the range of 0.05 to 0.75. Vpf 1 = (0.8−Ceq1) × 129 (1) where Ceq1 (%) = [C%] + 0.10 [Si%]
+0.06 [Mn%], and [C%], [Si%] and [Mn%] indicate the contents (% by mass) of C, Si and Mn, respectively.
【0011】上記本発明ではC,SiおよびMnを基本
成分として含む熱間圧延鋼線材または冷間伸線された鋼
線材を対象とするのであるが、これらの成分の他、C
r:2%以下(0%を含まない)、Mo:1%以下(0
%を含まない)およびNi:3%以下(0%を含まな
い)よりなる群から選ばれる1種以上の元素を含む含む
熱間圧延鋼線材または冷間伸線された鋼線材において、
初析フェライトとパーライトを主体とする組織を有する
と共に、平均結晶粒径が6〜15μmであり、且つ下記
(2)式で表される平衡初析フェライト体積率(Vpf
2 )に対する初析フェライト体積率Vfの比(Vf/V
pf2 )が0.05〜0.75である様な鋼線材におい
ても上記目的を達成することができる。 Vpf2 =(0.8−Ceq2)×129 …(2) 但し、Ceq2(%)=[C%]+0.10[Si%]
+0.06[Mn%]+0.11[Cr%]−0.16
[Mo%]+0.04[Ni%]であり、[C%]、
[Si%]、[Mn%]、[Cr%]、[Mo%]およ
び[Ni%]は、夫々C、Si、Mn、Cr、Moおよ
びNiの含有量(質量%)を示す。
The present invention is directed to a hot-rolled steel wire or a cold-drawn steel wire containing C, Si and Mn as basic components.
r: 2% or less (excluding 0%), Mo: 1% or less (0%
%) And Ni: 3% or less (excluding 0%) in a hot-rolled steel wire or a cold-drawn steel wire containing one or more elements selected from the group consisting of:
It has a structure mainly composed of proeutectoid ferrite and pearlite, has an average crystal grain size of 6 to 15 μm, and has a volume fraction of equilibrium proeutectoid ferrite (Vpf) represented by the following formula (2).
2 ) Ratio of proeutectoid ferrite volume fraction Vf to (Vf / V)
The above object can be achieved even with a steel wire having a pf 2 ) of 0.05 to 0.75. Vpf 2 = (0.8−Ceq2) × 129 (2) where Ceq2 (%) = [C%] + 0.10 [Si%]
+0.06 [Mn%] + 0.11 [Cr%]-0.16
[Mo%] + 0.04 [Ni%], [C%],
[Si%], [Mn%], [Cr%], [Mo%] and [Ni%] indicate the contents (% by mass) of C, Si, Mn, Cr, Mo and Ni, respectively.
【0012】上記本発明の鋼線材においては、上記化学
成分の他、Al:0.01〜0.06%を含有すると共
に、P:0.02%以下(0%を含む)、S:0.02
以下(0%を含む)およびN:0.01%以下(0%を
含む)に夫々抑制することも有効であり、これによって
鋼線材の特性を更に向上させることができる。
The steel wire of the present invention contains, in addition to the above chemical components, Al: 0.01 to 0.06%, P: 0.02% or less (including 0%), and S: 0. .02
It is also effective to suppress the content to below 0.01% (including 0%) and N: 0.01% or less (including 0%), respectively, whereby the properties of the steel wire can be further improved.
【0013】一方、本発明の鋼線材を製造するに当たっ
ては、上記各化学成分組成を満足する鋼材を用い、
(1)750〜950℃の温度で熱間仕上げ圧延した
後、5℃/秒以上の冷却速度で600〜650℃まで冷
却し、引き続き1℃/秒以下の冷却速度で徐冷するか、
または(2)750〜950℃の温度で熱間仕上げ圧延
した後、50℃/秒以上の冷却速度で700〜800℃
まで冷却し、その後5℃/秒以上の冷却速度で600〜
650℃まで冷却し、引き続き1℃/秒以下の冷却速度
で徐冷する様にすれば良い。
On the other hand, in producing the steel wire rod of the present invention, a steel rod satisfying the above-mentioned chemical composition is used.
(1) After hot finish rolling at a temperature of 750 to 950 ° C., cool to 600 to 650 ° C. at a cooling rate of 5 ° C./sec or more, and then gradually cool at a cooling rate of 1 ° C./sec or less,
Or (2) after hot finish rolling at a temperature of 750 to 950 ° C., and at a cooling rate of 50 ° C./sec or more, 700 to 800 ° C.
And then at a cooling rate of 5 ° C./sec.
It may be cooled to 650 ° C. and then gradually cooled at a cooling rate of 1 ° C./sec or less.
【0014】[0014]
【発明の実施の形態】本発明者らは、球状化時間を短縮
させても変形抵抗の低減と変形能向上の両方を満足させ
ることのできる最適な前組織を検討した。その結果、フ
ェライトとパーライトを主体とする組織において、その
平均結晶粒径を調整すると共に、パーライト体積率を増
大して初析フェライト体積率を低減させることが有効で
あることが判明した。即ち、平均結晶粒径を6〜15μ
mに調整し、且つ化学成分に応じた上記(1)式または
(2)式で表される平衡初析フェライト体積率(Vpf
1 またはVpf2 )に対する初析フェライト体積率Vf
の比(Vf/Vpf1 またはVf/Vpf2 )が0.0
5〜0.75である様な鋼線材においては、上記目的が
見事に達成されることを見出し、本発明を完成した。
DETAILED DESCRIPTION OF THE INVENTION The present inventors have reduced the sphering time.
Even if it does, it will satisfy both the reduction of deformation resistance and the improvement of deformability
The best pre-organization that can be done was examined. As a result,
In organizations that are primarily cellulite and perlite
Adjust the average crystal grain size and increase the pearlite volume ratio
It is effective to reduce the volume fraction of proeutectoid ferrite
It turned out to be. That is, the average crystal grain size is 6 to 15 μm.
m, and the above formula (1) or
The equilibrium proeutectoid ferrite volume fraction (Vpf) expressed by the equation (2)
1 Or VpfTwo ) To proeutectoid ferrite volume fraction Vf
Ratio (Vf / Vpf1 Or Vf / VpfTwo ) Is 0.0
In the case of a steel wire having a diameter of 5 to 0.75,
The inventors have found that the present invention has been accomplished brilliantly, and completed the present invention.
【0015】上記比(Vf/Vpf1 またはVf/Vp
2 )の値が0.05未満となると、初析フェライトの
体積割合が小さくなり、圧延後の硬さ上昇が問題となる
だけでなく、球状化焼鈍後も硬さ低下が不十分であるの
で、変形抵抗が高く工具寿命の低下の問題が生じる。一
方、上記比(Vf/Vpf1 またはVf/Vpf2 )の
値が0.75よりも大きくなると、球状化時間も長くか
かると同時に、迅速球状化条件では変形能が低下する。
尚上記比の値の好ましい範囲は、0.15〜0.60程
度であり、この範囲内では本発明の効果が最も有効に達
成される。また本発明の鋼線材は、前述の如く初析フェ
ライトとパーライトを主体とするものであるが、その他
微量であればベイナイトやマルテンサイト等の組織が混
在していても良い。但し、これらマルテンサイトやベイ
ナイトの組織が多量に生成すると、球状化焼鈍後も硬さ
が低下せず、冷間鍛造時の工具寿命が低下するので、そ
の量は10%以下にすべきである。
The above ratio (Vf / Vpf 1 or Vf / Vp
When the value of f 2 ) is less than 0.05, the volume ratio of proeutectoid ferrite becomes small, and not only the hardness increase after rolling becomes a problem, but also the hardness decrease after spheroidizing annealing is insufficient. Therefore, there is a problem that the deformation resistance is high and the tool life is shortened. On the other hand, the value of the ratio (Vf / Vpf 1 or Vf / Vpf 2) is the greater than 0.75, and at the same time takes longer spheronization time, the rapid spheroidization conditions deformability decreases.
The preferable range of the value of the above ratio is about 0.15 to 0.60, and within this range, the effect of the present invention is most effectively achieved. The steel wire of the present invention is mainly composed of proeutectoid ferrite and pearlite as described above, but may have other microstructures such as bainite and martensite if they are trace amounts. However, when a large amount of such a martensite or bainite structure is formed, the hardness does not decrease even after spheroidizing annealing, and the tool life during cold forging decreases. Therefore, the amount should be 10% or less. .
【0016】本発明の鋼線材においては、その平均結晶
粒径を6〜15μmに調整する必要がある。この平均結
晶粒径が15μmを超えて粗い組織となると、球状化時
間が長くかかると共に、線材の変形能も十分でなくな
る。逆に、平均結晶粒径が6μm未満となって微細にな
ると変形能は向上するが、硬さの低下に時間がかかり、
迅速球状化に適しない。この平均結晶粒径の好ましい範
囲は、7〜12μmである。尚通常の熱間圧延材のフェ
ライト・パーライト組織の平均結晶粒径は15〜25μ
m程度である。
In the steel wire of the present invention, it is necessary to adjust the average crystal grain size to 6 to 15 μm. When the average crystal grain size exceeds 15 μm to form a coarse structure, the spheroidizing time is long and the wire has insufficient deformability. Conversely, when the average crystal grain size becomes less than 6 μm and becomes finer, the deformability improves, but it takes time to lower the hardness,
Not suitable for rapid spheroidization. The preferred range of the average crystal grain size is 7 to 12 μm. The average grain size of the ferrite-pearlite structure of a normal hot-rolled material is 15 to 25 μm.
m.
【0017】本発明の鋼線材において、その平均結晶粒
径が6〜15μm(好ましくは7〜12μm)である
(フェライト+パーライト)組織にする為には、熱間圧
延条件の制御、特に最終圧延温度の制御が重要な要件と
なる。こうした観点からして、熱間仕上げ圧延温度を7
50〜950℃とする必要がある。熱間仕上げ圧延温度
が750〜950℃の温度範囲となる様にすれば、線材
断面内の全てで平均結晶粒径が6〜15μmとなる(フ
ェライト+パーライト)組織を生成し得る。
In order to obtain a (ferrite + pearlite) structure having an average crystal grain size of 6 to 15 μm (preferably 7 to 12 μm) in the steel wire rod of the present invention, control of hot rolling conditions, particularly final rolling Temperature control is an important requirement. From this viewpoint, the hot finish rolling temperature is set to 7
The temperature must be 50 to 950 ° C. When the hot finish rolling temperature is in the temperature range of 750 to 950 ° C., a (ferrite + pearlite) structure in which the average crystal grain size becomes 6 to 15 μm in the entire cross section of the wire can be generated.
【0018】熱間仕上げ圧延温度が950℃を超える
と、組織の粗大化が起こる。またこの温度が750℃未
満となると、平均結晶粒径が6μm未満となる可能性が
ある。この場合、前述した様に硬さの低下が不十分で、
冷間鍛造時の工具寿命低下の問題が生ずる。また圧延時
の塑性歪を有したまま変態し、圧延方向に展伸された結
晶粒が生成する可能性も高くなり、このときには変態後
の組織は圧延方向に展伸されているので、変形能が低下
する。尚本発明における熱間仕上げ圧延温度とは、最終
仕上圧延機出側での線材表面温度を意味する。
If the hot finish rolling temperature exceeds 950 ° C., the structure becomes coarse. If the temperature is lower than 750 ° C., the average crystal grain size may be lower than 6 μm. In this case, the decrease in hardness is insufficient as described above,
The problem of a reduction in tool life during cold forging occurs. In addition, there is a high possibility that the crystal is transformed while having the plastic strain at the time of rolling, and crystal grains expanded in the rolling direction are formed. At this time, since the transformed structure is expanded in the rolling direction, the deformability Decrease. The hot finish rolling temperature in the present invention means the surface temperature of the wire at the exit side of the final finishing mill.
【0019】初析フェライト体積率Vpfを調整するに
は、550〜650℃程度の温度で恒温変態して、硬質
相であるベイナイトやマルテンサイトの生成を抑制する
ことによって可能となる。また、圧延後に前記比(Vf
/Vpf1 またはVf/Vpf2 )の値を0.05〜
0.75にする為には、圧延後の冷却条件の制御が必要
である。特に、微細な(フェライト+パーライト)結晶
粒を得るために上記のように圧延条件を制御してオース
テナイト結晶粒を微細化すると、変態が促進されるの
で、初析フェライト分率が増加する傾向がある。従っ
て、微細結晶粒を得るときには特に、ベイナイトやマル
テンサイトが生成しない程度の急冷が必要となる。
The volume fraction of pro-eutectoid ferrite Vpf can be adjusted by isothermal transformation at a temperature of about 550 to 650 ° C. to suppress the formation of bainite and martensite, which are hard phases. After rolling, the ratio (Vf
0.05 the value of / Vpf 1 or Vf / Vpf 2)
In order to make it 0.75, it is necessary to control cooling conditions after rolling. In particular, when the austenite crystal grains are refined by controlling the rolling conditions as described above in order to obtain fine (ferrite + pearlite) crystal grains, the transformation is promoted, and the pro-eutectoid ferrite fraction tends to increase. is there. Therefore, particularly when obtaining fine crystal grains, rapid cooling is required to the extent that bainite and martensite are not generated.
【0020】線材圧延においては、最適冷却条件は成分
によって異なるが、熱間仕上げ圧延した後、600〜6
50℃まで冷却速度5℃/秒以上の冷却速度で冷却し、
引き続き1℃/秒以下の冷却速度で徐冷することによ
り、フェライト分率を低下させながらベイナイトやマル
テンサイトの生成を抑制することが可能となる。このと
きの徐冷終了温度は、(フェライト+パーライト)変態
がほぼ終了するまで行なう。尚この冷却工程において、
650℃を超える温度で徐冷を開始すると、初析フェラ
イトが多量に生成するので迅速球状化に適しない。また
600℃未満の温度で徐冷を開始すると、ベイナイトや
マルテンサイトが生成する恐れがある。更に、600〜
650℃までを5℃/秒未満の冷却速度で冷却すると、
初析フェライトが多量に生成する恐れがある。それ以降
の温度を1℃/秒を超える冷却速度で冷却するとベイナ
イトやマルテンサイトが生成する恐れがある。
In the wire rod rolling, the optimum cooling conditions vary depending on the components.
Cooling to 50 ° C at a cooling rate of 5 ° C / sec or more,
Subsequently, by slow cooling at a cooling rate of 1 ° C./second or less, it is possible to suppress the formation of bainite and martensite while reducing the ferrite fraction. The slow cooling end temperature at this time is performed until the (ferrite + pearlite) transformation is almost completed. In this cooling step,
When slow cooling is started at a temperature exceeding 650 ° C., a large amount of pro-eutectoid ferrite is generated, which is not suitable for rapid spheroidization. Also, if slow cooling is started at a temperature lower than 600 ° C., bainite and martensite may be generated. In addition, 600-
Cooling to 650 ° C. at a cooling rate of less than 5 ° C./sec.
Proeutectoid ferrite may be produced in large quantities. If the subsequent temperature is cooled at a cooling rate exceeding 1 ° C./sec, bainite and martensite may be formed.
【0021】上記製造工程において、上記熱間仕上げ圧
延後、一旦700〜800℃まで冷却速度50℃/秒以
上で冷却し、その後600〜650℃まで冷却速度5℃
/秒以上で冷却し、それに引き続き1℃/秒以下で徐冷
する様にしても良い。この方法によって、仕上圧延後の
結晶粒粗大化を防止できると同時に、初析フェライトの
生成を抑制することが出来る。この方法を採用するとき
には、600〜650℃までを冷却速度50℃/秒以上
で急冷すると、温度バラツキによって部分的にはベイナ
イトやマルテンサイトが生成する可能性があることと、
断面内の温度分布が付いたまま変態して、断面内で組織
が大きく異なる可能性が生じるので、700〜800℃
で冷却速度を変更することが望ましい。
In the above manufacturing process, after the hot finish rolling, the steel sheet is once cooled to 700 to 800 ° C. at a cooling rate of 50 ° C./sec or more, and then cooled to 600 to 650 ° C. at a cooling rate of 5 ° C.
/ Sec or more, followed by slow cooling at 1 ° C / sec or less. By this method, it is possible to prevent coarsening of crystal grains after finish rolling, and at the same time, it is possible to suppress generation of pro-eutectoid ferrite. When adopting this method, when quenching from 600 to 650 ° C. at a cooling rate of 50 ° C./sec or more, bainite or martensite may be partially generated due to temperature variation,
Transformation is performed with the temperature distribution in the cross section, and the structure may be significantly different in the cross section.
It is desirable to change the cooling rate by using.
【0022】本発明の鋼線材は、C,SiおよびMnを
基本成分として含む熱間圧延鋼線材または冷間伸線され
た鋼線材を対象とするのであるが、これらの成分の他、
Cr:2%以下(0%を含まない)、Mo:1%以下
(0%を含まない)およびNi:3%以下(0%を含ま
ない)よりなる群から選ばれる1種以上の元素を含む含
む熱間圧延鋼線材または冷間伸線された鋼線材を対象と
する。これらの元素の範囲限定理由は下記の通りであ
る。尚、前述した如く、鋼線材の化学成分組成に応じ
て、前記(1)式または(2)式で表される平衡初析フ
ェライト体積率(Vpf1 )または(Vpf2 )を採用
する必要がある。
The steel wire of the present invention is intended for a hot-rolled steel wire or a cold-drawn steel wire containing C, Si and Mn as basic components.
At least one element selected from the group consisting of Cr: 2% or less (excluding 0%), Mo: 1% or less (excluding 0%), and Ni: 3% or less (excluding 0%) Including hot rolled steel wire or cold drawn steel wire. The reasons for limiting the range of these elements are as follows. As described above, it is necessary to adopt the equilibrium proeutectoid ferrite volume fraction (Vpf 1 ) or (Vpf 2 ) represented by the above formula (1) or (2) depending on the chemical composition of the steel wire. is there.
【0023】C:0.2〜0.6% Cは、強度付与元素であり、0.2%未満では必要な強
度が得られない。一方、0.6%を超えると冷間加工性
の低下、靱性の低下があるので、これを上限とする。尚
C含有量の好ましい下限は、0.3%であり、好ましい
上限は0.5%である。
C: 0.2-0.6% C is a strength-imparting element, and if it is less than 0.2%, required strength cannot be obtained. On the other hand, if it exceeds 0.6%, there is a decrease in cold workability and a decrease in toughness. The preferred lower limit of the C content is 0.3%, and the preferred upper limit is 0.5%.
【0024】Si:0.3%以下 Siは、脱酸剤として添加されるが、多量に添加すると
強度上昇が著しく、冷間加工性が低下するので、上限を
0.3%にする。尚Si含有量の好ましい上限は0.2
5%である。
Si: not more than 0.3% Si is added as a deoxidizing agent, but if added in a large amount, the strength is significantly increased and the cold workability is reduced, so the upper limit is made 0.3%. The preferred upper limit of the Si content is 0.2
5%.
【0025】Mn:0.2〜1.5% Mnは、脱酸・脱硫剤および焼入れ性向上元素として添
加されるが、その効果を発揮させるためには0.2%以
上含有させる必要がある。しかしながら、その含有量が
過剰になると、偏析による組織の不均一性が生じ、冷間
加工性や靱性の低下を招くので、上限を1.5%とする
必要がある。尚Mn含有量の好ましい下限は、0.4%
であり、好ましい上限は1.0%である。
Mn: 0.2-1.5% Mn is added as a deoxidizing / desulfurizing agent and an element for improving hardenability, but it is necessary to contain Mn at 0.2% or more in order to exert its effects. . However, if the content is excessive, the structure becomes non-uniform due to segregation, which causes a reduction in cold workability and toughness. Therefore, it is necessary to set the upper limit to 1.5%. The preferred lower limit of the Mn content is 0.4%
And a preferable upper limit is 1.0%.
【0026】Cr:2%以下(0%を含まない)、M
o:1%以下(0%を含まない)およびNi:3%以下
(0%を含まない)よりなる群から選ばれる1種以上の
元素 Cr、MoおよびNiは、焼入れ性確保に有効である
が、過剰に含有させると冷間鍛造性や靱性を劣化させる
ので、上限をそれぞれ2%、1%、3%とする必要があ
る。尚これらの元素による上記効果は、上記範囲内では
その含有量を増加させるにつれておおきくなるが、上記
効果を発揮させる為には、Crで0.10%以上、Mo
で0.05%以上、Niで0.20%以上含有させるこ
とが好ましい。
Cr: 2% or less (excluding 0%), M
o: 1% or less (excluding 0%) and Ni: 3% or less
(Not including 0%) at least one member selected from the group consisting of
The elements Cr, Mo and Ni are effective in ensuring quenchability, but if contained excessively, they deteriorate the cold forgeability and toughness. Therefore, the upper limits must be 2%, 1% and 3%, respectively. The effect of these elements increases as the content increases within the above range. However, in order to exhibit the above effect, the content of Cr is 0.10% or more, and
Is preferably 0.05% or more and Ni is preferably 0.20% or more.
【0027】本発明の鋼線材においては、Al:0.0
1〜0.06%を含有すると共に、P:0.02%以下
(0%を含む)、S:0.02以下(0%を含む)およ
びN:0.01%以下(0%を含む)に夫々抑制するこ
とも有効であり、これによって鋼線材の特性を更に向上
させることができる。また本発明の鋼線材における上記
の基本的な化学成分組成の他は、Feおよび不可避不純
物からなるものであるが、必要によってV,Ti,B,
Ca等を含有させることも有効である。これらの元素の
範囲限定理由は、下記の通りである。尚これらの成分以
外にも、本発明の鋼線材には、その特性を阻害しない程
度の微量成分を含み得るものであり、こうした鋼線材も
本発明の範囲に含まれるものである。
In the steel wire of the present invention, Al: 0.0
P: 0.02% or less (including 0%), S: 0.02 or less (including 0%) and N: 0.01% or less (including 0%) It is also effective to suppress each of them, and the characteristics of the steel wire can be further improved. In addition to the above-mentioned basic chemical composition in the steel wire rod of the present invention, the steel wire rod is composed of Fe and unavoidable impurities.
It is also effective to contain Ca and the like. The reasons for limiting the range of these elements are as follows. In addition, besides these components, the steel wire of the present invention may contain a trace component that does not impair its properties, and such a steel wire is also included in the scope of the present invention.
【0028】Al:0.01〜0.06% Alは脱酸剤であると同時に、窒素の固定による冷間鍛
造中の動的歪時効を抑制して、変形抵抗の低減を図る働
きがある。こうした効果を発揮させる為には、少なくと
も0.01%含有させる必要があるが、過剰になると却
って靱性を低下させるので、上限を0.06%とした。
尚Al含有量の好ましい下限は0.02%であり、好ま
しい上限は0.04%である。
Al: 0.01 to 0.06% Al is a deoxidizing agent, and at the same time, has a function of suppressing dynamic strain aging during cold forging by fixing nitrogen to reduce deformation resistance. . In order to exert such effects, it is necessary to contain at least 0.01%, but if it is excessive, the toughness is rather reduced, so the upper limit was made 0.06%.
The preferred lower limit of the Al content is 0.02%, and the preferred upper limit is 0.04%.
【0029】P:0.02%以下(0%を含む)、S:
0.02%以下(0%を含む) PとSは、冷間加工性、特に変形能を低下させるので、
いずれも0.02%以下に抑制する必要がある。尚これ
らの元素は、いずれも0.01%以下に抑制することが
好ましい。
P: 0.02% or less (including 0%), S:
0.02% or less (including 0%) P and S reduce cold workability, particularly deformability,
In any case, it is necessary to suppress the content to 0.02% or less. It is preferable that any of these elements is suppressed to 0.01% or less.
【0030】N:0.01%以下(0%を含む) Nは、冷間鍛造中の動的歪時効を起こし、変形抵抗上昇
と変形能の低下を招くので、上限を0.01%とする。
尚N含有量は、0.006%以下に抑制することが好ま
しいV:0.5%以下(0%を含まない) Vは析出強化を目的として添加しても良いが、多量に添
加すると冷間鍛造性や靱性を劣化させるので、その上限
を0.5%とする。
N: 0.01% or less (including 0%) N causes dynamic strain aging during cold forging and causes an increase in deformation resistance and a decrease in deformability, so the upper limit is made 0.01%. I do.
Incidentally, the N content is preferably suppressed to 0.006% or less V: 0.5% or less (excluding 0%) V may be added for the purpose of strengthening the precipitation, but when added in a large amount, it is possible to cool down. Since the forgeability and toughness deteriorate, the upper limit is made 0.5%.
【0031】Ti:0.1%以下(0%を含まない) Tiは固溶Nの固定による動的歪時効抑制効果によっ
て、冷間鍛造時の変形抵抗低減に有効な元素であるので
添加して良い。特にBを添加した場合は、冷鍛後の調質
時の焼入れ性を安定させるためにN添加が不可欠であ
り、Ti添加がN固定に効果を発揮する。但し、過剰に
含有させると、粗大なTiNが析出して機械的性質を損
なうので、上限を0.1%とする。
Ti: 0.1% or less (not including 0%) Ti is added because it is an element effective in reducing deformation resistance during cold forging due to the effect of suppressing dynamic strain aging by fixing solid solution N. Good. In particular, when B is added, N addition is indispensable to stabilize the hardenability during refining after cold forging, and Ti addition has an effect on N fixation. However, if it is contained excessively, coarse TiN will precipitate and impair the mechanical properties, so the upper limit is made 0.1%.
【0032】B:0.01%以下(0%を含まない) Bは少量でも焼入れ性を上昇させるのに有効な元素であ
るので、必要により添加しても良い。但し、過剰に含有
させると靱性を劣化させるので、上限を0.01%とす
る。
B: 0.01% or less (excluding 0%) B is an element effective for improving hardenability even in a small amount, and may be added as necessary. However, if it is contained excessively, the toughness is degraded, so the upper limit is made 0.01%.
【0033】Ca:0.01%以下(0%を含まない) Caは、MnSの形態を球状化して、横方向の靱性を向
上させる効果があるので添加しても良いが、過剰に含有
させると大型介在物を生成して、機械的性質を損なうの
で、上限を0.01%とする。
Ca: 0.01% or less (excluding 0%) Ca may be added because it has the effect of spheroidizing the form of MnS and improving the toughness in the lateral direction, but may be added in excess. And large inclusions are generated to impair the mechanical properties, so the upper limit is made 0.01%.
【0034】以下、本発明を実施例によって更に詳細に
説明するが、下記実施例は本発明を限定する性質のもの
ではなく、前・後記の趣旨に徴して設計変更することは
いずれも本発明の技術的範囲に含まれるものである。
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are not intended to limit the present invention, and any change in the design based on the above and following points is not limited to the present invention. It is included in the technical range of.
【0035】[0035]
【実施例】実施例1 S45C相当鋼(C:0.45%、Si:0.17%、
Mn:0.75%)を用い、熱間加工シミュレーターで
800℃と1000℃で加工後、500℃、600℃、
700℃まで急冷して、その温度で恒温保持した。組織
はすべてフェライト+パーライト組織となっていたが、
初析フェライト体積率Vf、および初析フェライト体積
率Vfと平衡初析フェライト体積率Vpf1 との比(V
f/Vpf1 )は、下記表1に示すような値となった。
このとき球状化焼鈍は、180℃/hで740℃まで昇
温し、この温度で4時間保持した後、680℃まで12
℃/hで徐冷し、その後放冷する方法で球状化処理を標
準条件とした。迅速球状化条件としては、680℃まで
の冷却を24℃/hで行った。
EXAMPLES Example 1 S45C equivalent steel (C: 0.45%, Si: 0.17%,
(Mn: 0.75%) using a hot working simulator at 800 ° C and 1000 ° C, then 500 ° C, 600 ° C,
It was rapidly cooled to 700 ° C. and kept at that temperature. The structure was all ferrite + pearlite structure,
Proeutectoid ferrite volume fraction Vf, and the ratio of proeutectoid ferrite volume fraction Vf to equilibrium proeutectoid ferrite volume fraction Vpf 1 (V
f / Vpf 1 ) was a value as shown in Table 1 below.
At this time, in the spheroidizing annealing, the temperature was raised to 740 ° C. at 180 ° C./h, and was maintained at this temperature for 4 hours.
The spheroidizing treatment was performed under a standard condition by slowly cooling at a rate of ° C./h and then allowing to cool. As rapid spheroidizing conditions, cooling to 680 ° C. was performed at 24 ° C./h.
【0036】変形能は、冷間鍛造性との相関が確認され
ている微小サンプルを変形し、割れが発生するまでの変
形量で評価した。変形量値が大きいほど変形能は良好と
なる。硬さは、荷重5kgでビッカース硬さを測定し
た。
The deformability was evaluated based on the amount of deformation until a crack was formed by deforming a micro sample that had been confirmed to have a correlation with cold forgeability. The larger the deformation value, the better the deformability. As for hardness, Vickers hardness was measured under a load of 5 kg.
【0037】その結果を、下記表1に併記するが、この
結果から明らかな様に、前記比(Vf/Vpf1 )の値
を適切な範囲に調整することによって、短時間の球状化
条件でも十分に低い硬さと良好な変形能が得られている
ことが分かる。
The results are also shown in Table 1 below. As is clear from the results, by adjusting the value of the ratio (Vf / Vpf 1 ) to an appropriate range, even under a short-time spheroidizing condition, It can be seen that sufficiently low hardness and good deformability are obtained.
【0038】[0038]
【表1】 [Table 1]
【0039】実施例2 供試材の成分を表2に示す。これらを下記表3に示す種
々の条件で、線径8〜16mmの線材に熱間圧延した。
尚このときの圧延温度は最表層で評価している。熱間圧
延後の組織観察は、最表層より0.3mm内部に入った
表層部で評価した。
Example 2 Table 2 shows the components of the test materials. These were hot-rolled under various conditions shown in Table 3 below into wires having a wire diameter of 8 to 16 mm.
The rolling temperature at this time was evaluated for the outermost layer. Microstructure observation after hot rolling was evaluated at a surface portion 0.3 mm inside the outermost layer.
【0040】上記圧延材を、180℃/hで(Ac1
20℃)まで昇温し、その温度で4時間保持した。その
後、680℃まで迅速化条件である18℃/hで徐冷
し、その後放冷する方法で球状化処理を行った。
The above-mentioned rolled material was heated at 180 ° C./h (Ac 1 +
(20 ° C.) and kept at that temperature for 4 hours. Thereafter, the spheroidizing treatment was performed by gradually cooling to 680 ° C. at a speed of 18 ° C./h, and then allowing to cool.
【0041】球状化程度は、夫々の試料の表面とD/4
の位置で、球状化した炭化物の割合と、硬さで評価し
た。球状化した炭化物の観察では、25μm四方の領域
を2000倍の走査型電子顕微鏡(SEM)で観察し、
個々の炭化物の個数とアスペクト比を求めた。アスペク
ト比が3以下の物を球状化した炭化物とし、全数に占め
る割合を求め、10視野での平均を計算した。硬さは、
荷重5kgのビッカース硬さを5点測定して平均を求め
た。冷間鍛造性は、切り欠き付きの据え込み試験で評価
した。その結果を、下記表4に示す。
The degree of spheroidization was determined by comparing the surface of each sample with D / 4
At the position, the ratio of the spheroidized carbide and the hardness were evaluated. In the observation of the spheroidized carbide, an area of 25 μm square was observed with a 2000 × scanning electron microscope (SEM).
The number and aspect ratio of individual carbides were determined. An object having an aspect ratio of 3 or less was regarded as a spheroidized carbide, the ratio of the carbide to the total number was determined, and the average in 10 visual fields was calculated. The hardness is
The Vickers hardness at a load of 5 kg was measured at five points and averaged. The cold forgeability was evaluated by a notched upsetting test. The results are shown in Table 4 below.
【0042】[0042]
【表2】 [Table 2]
【0043】[0043]
【表3】 [Table 3]
【0044】[0044]
【表4】 [Table 4]
【0045】これらの結果から、次の様に考察できる。
まずNo.2,3,5,13,15,21〜25のもの
は、本発明で規定する要件を外れるものである。No.
2は、低めの温度で圧延した後、600℃より低い温度
まで冷却したため、上記比(Vf/Vpf1 またはVf
/Vpf2 )の値が0.05よりも小さくなり、球状化
度は良いが、硬さが高くなっている。No.3のもの
は、圧延後の徐冷を650℃よりも高い温度から徐冷を
始めたので、上記比(Vf/Vpf1 またはVf/Vp
2 )の値が0.75よりも大きくなっており、硬さは
低いが、据え込み限界が低くなっている。
From these results, the following can be considered.
First, no. The items 2, 3, 5, 13, 15, 21 to 25 fall outside the requirements defined in the present invention. No.
2 was rolled at a lower temperature and then cooled to a temperature lower than 600 ° C., so that the above ratio (Vf / Vpf 1 or Vf
/ Vpf 2 ) is smaller than 0.05, and the degree of spheroidization is good, but the hardness is high. No. For sample No. 3, since the slow cooling after rolling was started from a temperature higher than 650 ° C., the ratio (Vf / Vpf 1 or Vf / Vp
The value of f 2 ) is greater than 0.75, and the hardness is low, but the upsetting limit is low.
【0046】No.5のものは、圧延温度が950℃よ
りも高くなっており、平均結晶粒径が15μmよりも大
きくなって、球状化率と据え込み率の両方とも悪くなっ
ている。No.13のものは、圧延温度が750℃より
も低くなっており、粒径が5μm以下になり、圧延方向
に伸びた結晶粒になっており、硬さが高く、据え込み限
界も低くなっている。No.15のものは、1℃/s以
下での徐冷開始温度が低くなっており、ベイナイト組織
となり、球状化後も硬さが高くなっている。
No. In No. 5, the rolling temperature was higher than 950 ° C., the average crystal grain size was larger than 15 μm, and both the spheroidization rate and the upsetting rate were poor. No. In the case of No. 13, the rolling temperature is lower than 750 ° C., the grain size is 5 μm or less, the grains are elongated in the rolling direction, the hardness is high, and the upsetting limit is low. . No. In the case of No. 15, the slow cooling start temperature at 1 ° C./s or less is low, the bainite structure is obtained, and the hardness is high even after spheroidization.
【0047】No.21のものは、Mnが多くベイナイ
トが生成しており、特性が劣化している。No.22の
ものは、Siが多く硬さが高い。No.23はAlが多
いために据え込み限界が低くなっている。No.24の
ものは、Alを無添加のため、また、No.25はN量
が多いため、Nによる歪時効を抑制できず、据え込み限
界が低くなっている。
No. 21 has a large amount of Mn, bainite is generated, and the characteristics are deteriorated. No. 22 has much Si and high hardness. No. No. 23 has a low upsetting limit due to a large amount of Al. No. In the case of No. 24, Al was not added. 25 has a large N content, so that strain aging due to N cannot be suppressed, and the upsetting limit is low.
【0048】これに対して、上記以外のNo.1,4,
6〜12,14,16〜20のものでは、迅速球状化が
達成され、球状化率と据え込み率の両方とも良好な値を
示していることが分かる。
On the other hand, No. other than the above 1,4,4
It can be seen that in the case of 6 to 12, 14, 16 to 20, rapid spheroidization was achieved, and both the spheroidization rate and the upsetting rate showed favorable values.
【0049】[0049]
【発明の効果】本発明は以上の様に構成されており、鋼
線材における冷間鍛造前の迅速球状化と、変形抵抗を向
上して優れた冷間鍛造性を併せて実現することができ
た。
The present invention is configured as described above, and can realize both rapid spheroidization of steel wires before cold forging and excellent cold forgeability by improving deformation resistance. Was.
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Claims (5)

    【特許請求の範囲】[Claims]
  1. 【請求項1】 C:0.2〜0.6%(質量%の意味、
    以下同じ)、Si:0.3%以下、Mn:0.2〜1.
    5%を夫々含む熱間圧延鋼線材または冷間伸線された鋼
    線材において、初析フェライトとパーライトを主体とす
    る組織を有すると共に、平均結晶粒径が6〜15μmで
    あり、且つ下記(1)式で表される平衡初析フェライト
    体積率(Vpf1 )に対する初析フェライト体積率Vf
    の比(Vf/Vpf1 )が0.05〜0.75であるこ
    とを特徴とする迅速球状化可能で冷間鍛造性の優れた鋼
    線材。 Vpf1 =(0.8−Ceq1)×129 …(1) 但し、Ceq1(%)=[C%]+0.10[Si%]
    +0.06[Mn%]であり、[C%]、[Si%]お
    よび[Mn%]は、夫々C、SiおよびMnの含有量
    (質量%)を示す。
    1. C: 0.2 to 0.6% (meaning by mass%,
    The same applies hereinafter), Si: 0.3% or less, Mn: 0.2 to 1.
    A hot-rolled steel wire or a cold-drawn steel wire containing 5% each has a structure mainly composed of proeutectoid ferrite and pearlite, has an average crystal grain size of 6 to 15 μm, and has the following (1) ) The volume fraction of pro-eutectoid ferrite Vf relative to the volume fraction of pro-eutectoid ferrite (Vpf 1 ) expressed by the formula
    The ratio of (Vf / Vpf 1 ) is from 0.05 to 0.75. A steel wire rod which can be rapidly spheroidized and has excellent cold forgeability. Vpf 1 = (0.8−Ceq1) × 129 (1) where Ceq1 (%) = [C%] + 0.10 [Si%]
    +0.06 [Mn%], and [C%], [Si%] and [Mn%] indicate the contents (% by mass) of C, Si and Mn, respectively.
  2. 【請求項2】 C:0.2〜0.6%、Si:0.3%
    以下、Mn:0.2〜1.5%を夫々含む他、Cr:2
    %以下(0%を含まない)、Mo:1%以下(0%を含
    まない)およびNi:3%以下(0%を含まない)より
    なる群から選ばれる1種以上の元素を含む含む熱間圧延
    鋼線材または冷間伸線された鋼線材において、初析フェ
    ライトとパーライトを主体とする組織を有すると共に、
    平均結晶粒径が6〜15μmであり、且つ下記(2)式
    で表される平衡初析フェライト体積率(Vpf2 )に対
    する初析フェライト体積率Vfの比(Vf/Vpf2)が
    0.05〜0.75であることを特徴とする迅速球状化
    可能で冷間鍛造性の優れた鋼線材。 Vpf2 =(0.8−Ceq2)×129 …(2) 但し、Ceq2(%)=[C%]+0.10[Si%]
    +0.06[Mn%]+0.11[Cr%]−0.16
    [Mo%]+0.04[Ni%]であり、[C%]、
    [Si%]、[Mn%]、[Cr%]、[Mo%]およ
    び[Ni%]は、夫々C、Si、Mn、Cr、Moおよ
    びNiの含有量(質量%)を示す。
    2. C: 0.2-0.6%, Si: 0.3%
    Hereinafter, in addition to Mn: 0.2 to 1.5%, Cr: 2
    % Or less (excluding 0%), Mo: 1% or less (excluding 0%), and Ni: heat containing at least one element selected from the group consisting of 3% or less (excluding 0%). In cold rolled steel wire or cold drawn steel wire, while having a structure mainly composed of proeutectoid ferrite and pearlite,
    The average crystal grain size is 6 to 15 μm, and the ratio (Vf / Vpf 2 ) of the volume fraction of pro-eutectoid ferrite Vf to the volume fraction of equilibrium eutectoid ferrite (Vpf 2 ) represented by the following formula ( 2 ) is 0.05. A steel wire rod which can be rapidly spheroidized and has excellent cold forgeability, characterized by having a diameter of 0.75 to 0.75. Vpf 2 = (0.8−Ceq2) × 129 (2) where Ceq2 (%) = [C%] + 0.10 [Si%]
    +0.06 [Mn%] + 0.11 [Cr%]-0.16
    [Mo%] + 0.04 [Ni%], [C%],
    [Si%], [Mn%], [Cr%], [Mo%] and [Ni%] indicate the contents (% by mass) of C, Si, Mn, Cr, Mo and Ni, respectively.
  3. 【請求項3】 Al:0.01〜0.06%を含有する
    と共に、P:0.02%以下(0%を含む)、S:0.
    02以下(0%を含む)およびN:0.01%以下(0
    %を含む)に夫々抑制したものである請求項1または2
    に記載の鋼線材。
    3. Al: 0.01 to 0.06%, P: 0.02% or less (including 0%), S: 0.
    02 or less (including 0%) and N: 0.01% or less (0%
    % Or 2%).
    The steel wire rod according to the above.
  4. 【請求項4】 請求項1〜3のいずれかに記載の鋼線材
    を製造するに当たり、750〜950℃の温度で熱間仕
    上げ圧延した後、5℃/秒以上の冷却速度で600〜6
    50℃まで冷却し、引き続き1℃/秒以下の冷却速度で
    徐冷することを特徴とする迅速球状化可能で冷間鍛造性
    の優れた鋼線材の製造方法。
    4. The steel wire according to claim 1, which is hot-finish rolled at a temperature of 750 to 950 ° C., and then cooled at a cooling rate of 5 ° C./sec.
    A method for producing a steel wire rod which can be rapidly spheroidized and has excellent cold forgeability, characterized in that it is cooled to 50 ° C. and then gradually cooled at a cooling rate of 1 ° C./second or less.
  5. 【請求項5】 請求項1〜3のいずれかに記載の鋼線材
    を製造するに当たり、750〜950℃の温度で熱間仕
    上げ圧延した後、50℃/秒以上の冷却速度で700〜
    800℃まで冷却し、その後5℃/秒以上の冷却速度で
    600〜650℃まで冷却し、引き続き1℃/秒以下の
    冷却速度で徐冷することを特徴とする迅速球状化可能で
    冷間鍛造性の優れた鋼線材の製造方法。
    5. In producing the steel wire according to any one of claims 1 to 3, after hot finish rolling at a temperature of 750 to 950 ° C., and at a cooling rate of 50 ° C./sec or more, 700 to 500 ° C./sec.
    It is cooled to 800 ° C., then cooled to 600 to 650 ° C. at a cooling rate of 5 ° C./sec or more, and then slowly cooled at a cooling rate of 1 ° C./sec or less, and can be rapidly spheroidized and cold forged. Method for producing steel wire with excellent resistance.
JP29107998A 1998-10-13 1998-10-13 Steel wire rod capable of rapid spheroidization and excellent cold forgeability and method for producing the same Expired - Lifetime JP3742232B2 (en)

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TWI711708B (en) * 2019-11-27 2020-12-01 中國鋼鐵股份有限公司 Method for increasing spheroidization rate of chrome molybdenum steel material

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