JPH06287685A - High strength hot rolled sheet excellent in elongation flanging property and fatigue characteristic - Google Patents
High strength hot rolled sheet excellent in elongation flanging property and fatigue characteristicInfo
- Publication number
- JPH06287685A JPH06287685A JP9547093A JP9547093A JPH06287685A JP H06287685 A JPH06287685 A JP H06287685A JP 9547093 A JP9547093 A JP 9547093A JP 9547093 A JP9547093 A JP 9547093A JP H06287685 A JPH06287685 A JP H06287685A
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- Japan
- Prior art keywords
- strength hot
- hot rolled
- rolled steel
- flangeability
- added
- Prior art date
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は伸びフランジ性及び疲労
特性の優れた高強度熱延鋼板に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high strength hot rolled steel sheet having excellent stretch flangeability and fatigue characteristics.
【０００２】[0002]
【従来の技術及び発明が解決しようとする課題】近年、
自動車、建築等の多くの産業分野における部材の軽量化
の傾向が高まり、それに伴い高強度の熱延鋼板が用いら
れているが、熱延鋼板が用いられる用途においては、優
れた伸びフランジ性が要求されることが多い。特に、自
動車部材に関しては、疲労特性も要求される材料も多
い。2. Description of the Related Art In recent years,
In many industrial fields such as automobiles and construction, the trend toward weight reduction of members is increasing, and high strength hot-rolled steel sheets are used accordingly, but in applications where hot-rolled steel sheets are used, excellent stretch flangeability is Often required. In particular, many automobile parts are required to have fatigue properties.
【０００３】従来、かゝる加工用高強度熱延鋼板として
は、フェライト・マルテンサイト組織或いはフェライト
・ベイナイト組織からなる混合組織が広く知られてい
る。Conventionally, as such a high-strength hot-rolled steel sheet for working, a mixed structure having a ferrite-martensite structure or a ferrite-bainite structure is widely known.
【０００４】しかし、フェライト・マルテンサイト組織
は、変形の初期からマルテンサイトの周囲にミクロ・ボ
イドが発生して割れを生じるため、伸びフランジ性に劣
る問題がある。However, the ferrite-martensite structure has a problem that the stretch flangeability is inferior because micro voids are generated around the martensite from the initial stage of deformation to cause cracking.
【０００５】また、フェライト・ベイナイト組織は、伸
びフランジ性は優れており、これまでに特開昭５７−１
０１６４９号公報及び特開昭６１−１３０４５４号公報
で、伸びフランジ性が優れたフェライト・ベイナイト組
織高強度熱延鋼板が既に提案されているが、この組織を
用いて伸びフランジ性を確保しながら７０kgf／mm2以上
の強度を得るのは困難である。Further, the ferrite bainite structure is excellent in stretch-flangeability, and has been disclosed in Japanese Patent Laid-Open No. 57-1.
No. 01649 and Japanese Patent Laid-Open No. 61-130454 propose a high strength hot-rolled steel sheet having a ferrite bainite structure which is excellent in stretch flangeability. It is difficult to obtain a strength of / mm 2 or more.
【０００６】一方、特開平２−８３４９号公報では、冷
間加工性及び溶接性に優れた５５kgf／mm2以上の高張力
熱延鋼帯が既に提案されているが、７０kgf／mm2以上の
強度では第２相体積率が高く、厳しい曲げ加工及び伸び
フランジ加工を行うのは困難である。また、特公平３−
６９９７６号公報で冷間加工性の極めて優れた高強度熱
延鋼板が既に提案されているが、Ｃ量が低く、７０kgf
／mm2以上の強度を得るのは困難である。その他、これ
までの析出強化による高強度熱延鋼板はパーライト等の
セメンタイトが多量に存在したために優れた伸びフラン
ジ性を得ることができなかった。On the other hand, in Japanese Unexamined 2-8349, JP-but good 55 kgf / mm 2 or more high tensile hot rolled steel strip in cold workability and weldability has been proposed, 70 kgf / mm 2 or more In terms of strength, the volume fraction of the second phase is high, and it is difficult to perform severe bending and stretch flanging. In addition, special fair 3-
Although high-strength hot-rolled steel sheets with extremely excellent cold workability have already been proposed in Japanese Patent No. 69976, the C content is low and 70 kgf
It is difficult to obtain a strength of / mm 2 or more. In addition, the high-strength hot-rolled steel sheet obtained by precipitation strengthening up to now cannot obtain excellent stretch-flange formability due to the large amount of cementite such as pearlite.
【０００７】本発明は、上記従来技術の問題点を解決し
て、７０kgf／mm2以上の強度で優れた伸びフランジ性と
疲労特性を有する高強度熱延鋼板を提供することを目的
とするものである。An object of the present invention is to solve the above problems of the prior art and to provide a high-strength hot-rolled steel sheet having strength of 70 kgf / mm 2 or more and excellent stretch-flangeability and fatigue characteristics. Is.
【０００８】[0008]
【課題を解決するための手段】本発明者らは、上記課題
を解決するために鋭意研究した結果、ベイナイト、マル
テンサイト及びパーライト等のセメンタイトを最小限に
し、かつ、組織の大部分を固溶Ｃの少ないフェライトに
し、ＴiとＣu添加量を制御することによってＴiＣ及び
Ｃuを中心とした析出強化と固溶強化によって引張強度
が７０kgf／mm2以上で優れた伸びフランジ性が得られる
ことを見い出した。また、セメンタイトを減少させ、Ｃ
uによるフェライトの固溶強化及び析出強化は、疲労亀
裂の発生を抑制し、優れた疲労強度が得られることも見
い出し、ここに本発明に至ったものである。Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that cementite such as bainite, martensite and pearlite is minimized and most of the structure is dissolved. It was found that ferrite with a small amount of C is used, and by controlling the amounts of Ti and Cu added, excellent stretch flangeability can be obtained at tensile strengths of 70 kgf / mm 2 or more due to precipitation strengthening and solid solution strengthening centered on TiC and Cu. It was It also reduces cementite and reduces C
It was also found that the solid solution strengthening and precipitation strengthening of ferrite by u suppress the occurrence of fatigue cracks and obtain excellent fatigue strength, and the present invention has been achieved here.
【０００９】すなわち、本発明は、Ｃ：０.０２〜０.１
０％、Ｓi≦２.０％、Ｍn：０.５〜２.０％、Ｃu：０.
１〜２.０％、Ｎi：０.１〜２.０％、Ｐ≦０.０８％、
Ｓ≦０.００６％、Ｎ≦０.００５％、Ａl：０.０１〜
０.１％、を含有し、更に、Ｔi：０.０６〜０.３％で、
かつ、０.１≦Ｔi／Ｃu≦１.０及び０.５０＜Ｔi／(４
Ｃ＋３.４３Ｎ＋１.５Ｓ)の関係を満たす量のＴiを含有
し、残部がＦe及び他の不可避的不純物よりなる組成を
有し、面積比率が８５％以上のフェライトからなる組織
を有することを特徴とする伸びフランジ性及び疲労特性
の優れた高強度熱延鋼板を要旨としている。That is, in the present invention, C: 0.02 to 0.1
0%, Si ≦ 2.0%, Mn: 0.5-2.0%, Cu: 0.0.
1 to 2.0%, Ni: 0.1 to 2.0%, P ≦ 0.08%,
S ≦ 0.006%, N ≦ 0.005%, Al: 0.01-
0.1%, and Ti: 0.06 to 0.3%,
And 0.1 ≦ Ti / Cu ≦ 1.0 and 0.50 <Ti / (4
C + 3.43N + 1.5S) in an amount satisfying the relationship of (C + 3.43N + 1.5S), the balance being Fe and other unavoidable impurities, and having an area ratio of 85% or more ferrite. The main point is a high-strength hot-rolled steel sheet having excellent stretch-flangeability and fatigue characteristics.
【００１０】また、他の本発明は、更に、Ｎb：０.００
５〜０.２％で、かつ、０.５０＜〔(Ｔi−３.４３Ｎ−
１.５Ｓ)／４＋Ｎb／７.７５〕／Ｃの関係を満たす量の
Ｎbを含有していることを特徴としている。Further, another invention of the present invention further comprises Nb: 0.00
5 to 0.2% and 0.50 <[((Ti-3.43N-
It is characterized by containing Nb in an amount satisfying the relationship of 1.5S) /4+Nb/7.75] / C.
【００１１】また、他の本発明は、更に、Ｍo：０.０５
〜０.５％、Ｖ：０.０１〜０.２％、Ｚr：０.０１〜０.
２％、Ｃr：０.１〜２.０％、Ｃa：０.０１％以下より
なる群から選ばれる少なくとも１種を含有していること
を特徴としている。The present invention also provides Mo: 0.05.
.About.0.5%, V: 0.01 to 0.2%, Zr: 0.01 to 0.0.
2%, Cr: 0.1 to 2.0%, Ca: 0.01% or less, and at least one selected from the group is characterized.
【００１２】また、他の本発明は、Ｎb：０.００５〜
０.２％で、かつ、０.５０＜〔(Ｔi−３.４３Ｎ−１.５
Ｓ)／４＋Ｎb／７.７５〕／Ｃの関係を満たす量のＮb
と、Ｍo：０.０５〜０.５％、Ｖ：０.０１〜０.２％、
Ｚr：０.０１〜０.２％、Ｃr：０.１〜２.０％、Ｃa：
０.０１％以下よりなる群から選ばれる少なくとも１種
を含有していることを特徴としている。Another aspect of the present invention is Nb: 0.005
0.2% and 0.50 <[((Ti-3.43N-1.5
S) /4+Nb/7.75] / C relationship of Nb
And Mo: 0.05 to 0.5%, V: 0.01 to 0.2%,
Zr: 0.01 to 0.2%, Cr: 0.1 to 2.0%, Ca:
It is characterized by containing at least one kind selected from the group consisting of 0.01% or less.
【００１３】[0013]
【作用】以下に本発明を更に詳細に説明する。まず、本
発明における鋼の化学成分の限定理由について説明す
る。The present invention will be described in more detail below. First, the reasons for limiting the chemical composition of steel in the present invention will be described.
【００１４】Ｃ：Ｃは鋼の強化を高めるために添加さ
れ、かゝる効果を有効に発揮させるためには少なくとも
０.０２％を添加する必要がある。しかし、過多に添加
すると、炭化物を形成するのに必要なＴi或いはＮbの添
加量が増加し、コストアップとなるばかりか、伸びフラ
ンジ性が劣化するので、添加量の上限を０.１０％とす
る。C: C is added to enhance the strengthening of the steel, and it is necessary to add at least 0.02% in order to effectively exert such an effect. However, if added excessively, the amount of Ti or Nb necessary for forming carbides increases, which not only increases the cost but also deteriorates the stretch flangeability, so the upper limit of the amount added is 0.10%. To do.
【００１５】Ｓi：Ｓiはフェライトの生成を促し、フェ
ライトの固溶Ｃ量を低減させ、更に伸びフランジ性をあ
まり劣化させずに強度を上げるのに有効な元素であるの
で、必要量を添加するが、過多に添加すれば溶接部の脆
化を招くのみならず、表面性状が劣化するので、本発明
鋼においては、２.０％以下に規制する。Si: Si is an element effective for promoting the formation of ferrite, reducing the amount of dissolved C in ferrite, and further increasing the strength without significantly deteriorating the stretch flangeability, so the necessary amount is added. However, if added in excess, not only does the weld become brittle, but the surface quality deteriorates. Therefore, in the steel of the present invention, the content is limited to 2.0% or less.
【００１６】Ｍn：Ｍnは鋼の固溶強化に有効な元素であ
るが、その効果を得るには少なくとも０.５％の添加を
必要とするが、過多に添加すれば焼入れ性が高くなり、
変態生成物を多量に生成し、高い伸びフランジ性を得る
ことが困難となるので、その上限を２.０％とする。Mn: Mn is an element effective for solid solution strengthening of steel, and at least 0.5% must be added to obtain the effect, but if added in excess, the hardenability becomes high,
Since it is difficult to produce a large amount of transformation products and obtain high stretch flangeability, the upper limit is set to 2.0%.
【００１７】Ｃu：Ｃuは本発明においても最も重要な元
素の一つであり、鋼の析出強化に有効な元素である。ま
た、疲労特性を向上させる有効な元素でもあり、これら
の効果を発揮させるには少なくとも０.１％を添加する
必要がある。しかし、過多に添加すればその効果が飽和
し、コストアップを招く。したがって、上限を２.０％
とする。Cu: Cu is one of the most important elements in the present invention and is an element effective for precipitation strengthening of steel. It is also an effective element for improving fatigue properties, and it is necessary to add at least 0.1% in order to exert these effects. However, if added too much, the effect will be saturated and the cost will increase. Therefore, the upper limit is 2.0%
And
【００１８】Ｎi：ＮiはＣu添加による熱間脆性を防止
する元素として有効である。その効果を発揮させるには
少なくとも０.１％が必要であるが、過多に添加すれば
その効果が飽和し、コストアップを招く。したがって、
上限を２.０％とする。Ni: Ni is effective as an element for preventing hot embrittlement due to addition of Cu. At least 0.1% is required to exert the effect, but if added in excess, the effect is saturated and the cost is increased. Therefore,
The upper limit is 2.0%.
【００１９】Ｐ：Ｐは延性を劣化させずに固溶強化する
有効な元素であるが、過多に添加すると加工後、遷移温
度を上昇させるので、０.０８％以下とする。P: P is an effective element for solid solution strengthening without deteriorating ductility, but if added in excess, it raises the transition temperature after processing, so it is made 0.08% or less.
【００２０】Ｓ：Ｓはこれを０.００６％を超えて多量
に含有させると、伸びフランジ性を劣化させるので、
０.００６％を上限とする。S: If S is contained in a large amount in excess of 0.006%, the stretch flangeability is deteriorated.
The upper limit is 0.006%.
【００２１】Ａl：Ａlは鋼の溶製時の脱酸剤として添加
され、その範囲は０.０１〜０.１％が好ましい。Al: Al is added as a deoxidizer during the melting of steel, and the range is preferably 0.01 to 0.1%.
【００２２】Ｔi：Ｔiは鋼中のＣ及びＮを析出物にして
析出強化し、フェライト中の固溶Ｃ量及びセメンタイト
を低減させ、伸びフランジ性を向上させる効果がある。
その効果を発揮させるには少なくとも０.０６％の添加
が必要で、かつ、０.５０＜Ｔi／(４Ｃ＋３.４３Ｎ＋
１.５Ｓ)となる量のＴiの添加が必要である。この関係
式を満たすことを規定した理由は、Ｔi／(４Ｃ＋３.４
３Ｎ＋１.５Ｓ)が０.５０未満になると鋼中のセメンタ
イトが増加かつ粗大になり、伸びフランジ性を低下させ
るためである。しかし、過多にＴi添加すると延性が劣
化し、或いは上記効果が飽和して経済的にも不利である
ので、上限を０.３％とする。Ti: Ti has the effect of making C and N in the steel precipitates and strengthening the precipitation, reducing the amount of solid solution C and cementite in the ferrite, and improving stretch flangeability.
In order to exert its effect, at least 0.06% must be added, and 0.50 <Ti / (4C + 3.43N +
It is necessary to add Ti in an amount of 1.5 S). The reason for defining that this relational expression is satisfied is Ti / (4C + 3.4
This is because if (3N + 1.5S) is less than 0.50, cementite in the steel increases and becomes coarse, and the stretch-flange formability deteriorates. However, if Ti is added excessively, the ductility is deteriorated, or the above effects are saturated and it is economically disadvantageous, so the upper limit is made 0.3%.
【００２３】Ｎb：また、本発明においては、Ｎbを添加
することによりＴiと同様の効果を得ることができるの
で、必要に応じてＮbを添加する。すなわち、Ｎbの析出
の効果を得るには、少なくとも０.００５％の添加が必
要で、かつ、Ｔi添加量との関係で０.５０＜〔(Ｔi−
３.４３Ｎ−１.５Ｓ)／４＋Ｎb／７.７５〕／Ｃとなる
量のＮbを添加する必要がある。この関係式を満たすこ
とを規定した理由は、〔(Ｔi−３.４３Ｎ−１.５Ｓ)／
４＋Ｎb／７.７５〕／Ｃが０.５０未満になると鋼中の
セメンタイトが増加かつ粗大になり、伸びフランジ性を
低下させるためである。しかし、過多にＮbを添加する
と延性が劣化し、或いは上記効果が飽和して経済的にも
不利であるので、上限を０.２％とする。Nb: In the present invention, the same effect as Ti can be obtained by adding Nb, so Nb is added if necessary. That is, in order to obtain the effect of Nb precipitation, at least 0.005% must be added, and 0.50 <[(Ti-
It is necessary to add Nb in an amount of 3.43N-1.5S) /4+Nb/7.75] / C. The reason for defining that this relational expression is satisfied is [(Ti-3.43N-1.5S) /
This is because if 4 + Nb / 7.75] / C is less than 0.50, the cementite in the steel increases and becomes coarse, and the stretch flange formability deteriorates. However, if Nb is added excessively, the ductility is deteriorated, or the above effect is saturated and it is economically disadvantageous, so the upper limit is made 0.2%.
【００２４】Ｍo、Ｖ、Ｚr、Ｃr、Ｃa：更に、本発明に
おいては、Ｍo、Ｖ、Ｚr、Ｃr及びＣaよりなる群から選
ばれる少なくとも１種の元素を必要に応じて添加するこ
とができる。Ｖ及びＺrは炭化物を形成し、フェライト
中の固溶Ｃ量を低減し、伸びフランジ性を向上させ、強
化する。これらの効果を発揮するにはそれぞれ少なくと
も０.０１％の添加が必要である。しかし、それぞれ過
多に添加すると上記効果が飽和して経済的にも不利であ
るので、それぞれの上限を０.２％とする。Mo, V, Zr, Cr, Ca: Furthermore, in the present invention, at least one element selected from the group consisting of Mo, V, Zr, Cr and Ca can be added if necessary. . V and Zr form carbides, reduce the amount of solute C in ferrite, improve stretch flangeability, and strengthen. In order to exert these effects, at least 0.01% of each must be added. However, if each is added excessively, the above effect is saturated and it is economically disadvantageous, so the respective upper limits are made 0.2%.
【００２５】また、Ｍo及びＣrは固溶強化元素として有
効であるが、その効果を発揮するには、Ｍoは少なくと
も０.０５％の添加が必要であり、Ｃrは少なくとも０.
１％の添加が必要である。しかし、それぞれ過多に添加
すると低温変態生成物を多量に生成するので、Ｍoの上
限を０.５％、Ｃrの上限を２.０％とする。Further, Mo and Cr are effective as solid solution strengthening elements, but in order to exert their effects, it is necessary to add Mo at least 0.05% and Cr is at least 0.05.
Addition of 1% is required. However, if they are added in excessive amounts, a large amount of low-temperature transformation products are produced, so the upper limit of Mo is set to 0.5% and the upper limit of Cr is set to 2.0%.
【００２６】また、Ｃaは硫化物を球状化する効果があ
り、伸びフランジ性を向上させるが、０.０１％を超え
るとその効果が飽和し、コストアップとなるので、これ
を上限とした。これら元素は単独で添加してもよく、ま
た複合添加してもよいが、複合添加することにより相乗
的な効果を得ることができるので有利である。Further, Ca has the effect of spheroidizing the sulfide and improves the stretch-flangeability, but if it exceeds 0.01%, the effect saturates and the cost increases, so this was made the upper limit. These elements may be added alone or in combination, but it is advantageous to add them in combination because a synergistic effect can be obtained.
【００２７】Ｔi／Ｃu：本発明では、上記化学成分にお
いてＴi／Ｃu比が重要である。すなわち、Ｔi／Ｃu＜
０.１の場合、ＴiＣを析出させる時に多量のＣuが析出
し、著しく伸びフランジ性が低下する。また、１.０＜
Ｔi／Ｃuの場合は、疲労強度比が低くなり、良好な疲労
特性を得ることができない。したがって、Ｔi／Ｃu比の
範囲を０.１≦Ｔi／Ｃu≦１.０とする。Ti / Cu: In the present invention, the Ti / Cu ratio is important in the above chemical composition. That is, Ti / Cu <
In the case of 0.1, a large amount of Cu is deposited when TiC is deposited, and the stretch flangeability is significantly deteriorated. Also, 1.0 <
In the case of Ti / Cu, the fatigue strength ratio becomes low, and good fatigue characteristics cannot be obtained. Therefore, the range of the Ti / Cu ratio is set to 0.1 ≦ Ti / Cu ≦ 1.0.
【００２８】本発明では、上記化学成分の鋼を通常の熱
間圧延工程において、面積比率が８５％以上のフェライ
トからなる組織にすることによって、伸びフランジ性に
優れた高強度熱延鋼板を得ることができる。In the present invention, a steel having the above chemical composition is formed into a structure composed of ferrite having an area ratio of 85% or more in a normal hot rolling process to obtain a high strength hot rolled steel sheet having excellent stretch flangeability. be able to.
【００２９】次に本発明の実施例を示す。Next, examples of the present invention will be described.
【００３０】表１に示す化学成分を有する鋼を１２００
℃に加熱し、通常の熱間圧延工程によって仕上温度８５
０〜９２０℃で、２.０mm厚に仕上げた。この後、冷却
速度と巻取温度を変化させて種々の組織の鋼板を製造し
た。このようにして得られた熱延鋼板について、ＪＩＳ
５号による圧延方向の引張試験、両振り平面曲げ疲労試
験、穴広げ試験及び組織観察を行った。その結果を表２
及び図１に示す。1200 steels having the chemical composition shown in Table 1 were prepared.
It is heated to ℃ and the finishing temperature is 85 by normal hot rolling process.
Finished to a thickness of 2.0 mm at 0-920 ° C. Then, the cooling rate and the coiling temperature were changed, and the steel plate of various structures was manufactured. Regarding the hot rolled steel sheet thus obtained, JIS
A tensile test in the rolling direction, a double-sided plane bending fatigue test, a hole expanding test, and a microstructure observation according to No. 5 were performed. The results are shown in Table 2.
And shown in FIG.
【００３１】両振り平面曲げ疲労試験は、１０7サイク
ルでの耐久応力を求めた。穴広げ試験は、径１０mmの打
ち抜き穴を６０°円錐ポンチにて押し広げ、割れが鋼板
を貫通した時点での穴径ｄを測定し、穴広げ率λを次式
にて計算した。λ＝〔(ｄ−１０)／１０〕×１００
(％)。組織は、ナイタール腐食後、走査電子顕微鏡にて
フェライト、ベイナイト、マルテンサイト及びパーライ
トを同定し、それぞれの面積比率を画像解析装置によっ
て測定した。In the both-sided plane bending fatigue test, the endurance stress at 10 7 cycles was obtained. In the hole expansion test, a punched hole having a diameter of 10 mm was expanded with a 60 ° conical punch, the hole diameter d when the crack penetrated the steel plate was measured, and the hole expansion ratio λ was calculated by the following formula. λ = [(d-10) / 10] × 100
(%). As for the structure, after nital corrosion, ferrite, bainite, martensite and pearlite were identified by a scanning electron microscope, and the area ratios of each were measured by an image analyzer.
【００３２】本発明鋼Ｎo.１〜Ｎo.６は、いずれも８５
％以上のフェライトからなる組織で、析出及び固溶強化
等により引張強度が７０kgf／mm2以上で高いλを有し、
優れた伸びフランジ性を有し、かつ、σｗ／ＴＳ比が
０.５以上の優れた疲労特性を有している。The steels No. 1 to No. 6 of the present invention are all 85
%, Which has a high λ of 70 kgf / mm 2 or more in tensile strength due to precipitation and solid solution strengthening.
It has excellent stretch-flangeability and excellent fatigue properties with a σw / TS ratio of 0.5 or more.
【００３３】これらに対し、比較鋼Ｎo.７はＴi／Ｃu比
が０.１未満でＣu添加量が多く、多量のＣuが析出した
ために延性が低い。比較鋼Ｎo.８〜Ｎo.１３は、Ｃu及
びＮiを殆ど含有しないため、本発明鋼に比べ、疲労特
性が低い。比較鋼Ｎo.１４は、〔(Ｔi−３.４３Ｎ−１.
５Ｓ)／４＋Ｎb／７.７５〕／Ｃを満足することができ
ず、低温変態生成物及びパーライトの面積率が高く、優
れた伸びフランジ性が得られない。On the other hand, in Comparative Steel No. 7, the Ti / Cu ratio was less than 0.1, the Cu addition amount was large, and a large amount of Cu was deposited, so that the ductility was low. The comparative steels No. 8 to No. 13 contain almost no Cu and Ni, and therefore have lower fatigue properties than the steels of the present invention. Comparative steel No. 14 is [(Ti-3.43N-1.
5S) /4+Nb/7.75] / C cannot be satisfied, the area ratio of the low temperature transformation product and pearlite is high, and excellent stretch flangeability cannot be obtained.
【００３４】[0034]
【表１】 [Table 1]
【００３５】[0035]
【表２】 [Table 2]
【００３６】[0036]
【発明の効果】以上詳述したように、本発明によれば、
７０kgf／mm2以上の強度で優れた伸びフランジ性と疲労
特性を有する高強度熱延鋼板を提供することができる。As described in detail above, according to the present invention,
It is possible to provide a high-strength hot-rolled steel sheet having strength of 70 kgf / mm 2 or more and excellent stretch-flangeability and fatigue characteristics.
【図１】Ｔi／Ｃuの質量比と穴広げ率λの関係、及びＴ
i／Ｃuの質量比とσw／ＴＳ比との関係を示す図であ
る。FIG. 1 shows the relationship between the Ti / Cu mass ratio and the hole expansion ratio λ, and T
It is a figure which shows the relationship between the mass ratio of i / Cu and (sigma) w / TS ratio.
Claims (4)
１≦Ｔi／Ｃu≦１.０及び０.５０＜Ｔi／(４Ｃ＋３.４
３Ｎ＋１.５Ｓ)の関係を満たす量のＴiを含有し、残部
がＦe及び他の不可避的不純物よりなる組成を有し、面
積比率が８５％以上のフェライトからなる組織を有する
ことを特徴とする伸びフランジ性及び疲労特性の優れた
高強度熱延鋼板。1. In weight% (hereinafter, the same), C: 0.02 to 0.10%, Si ≤ 2.0%, Mn: 0.5 to 2.0%, Cu: 0.1 to 2 0.0%, Ni: 0.1 to 2.0%, P ≦ 0.08%, S ≦ 0.006%, N ≦ 0.005%, Al: 0.01 to 0.1%, Further, Ti: 0.06 to 0.3%, and 0.0.
1 ≦ Ti / Cu ≦ 1.0 and 0.50 <Ti / (4C + 3.4)
(3N + 1.5S) Ti in an amount satisfying the relation of (3N + 1.5S), the balance being Fe and other inevitable impurities, and an area ratio of 85% or more. High-strength hot-rolled steel sheet with excellent flangeability and fatigue properties.
２％で、かつ、０.５０＜〔(Ｔi−３.４３Ｎ−１.５Ｓ)
／４＋Ｎb／７.７５〕／Ｃの関係を満たす量のＮbを含
有している請求項１に記載の伸びフランジ性及び疲労特
性の優れた高強度熱延鋼板。2. The steel further comprises Nb: 0.005-0.
2% and 0.50 <[((Ti-3.43N-1.5S))
The high-strength hot-rolled steel sheet having excellent stretch-flange formability and fatigue characteristics according to claim 1, containing Nb in an amount satisfying the relationship of /4+Nb/7.75]/C.
％、Ｖ：０.０１〜０.２％、Ｚr：０.０１〜０.２％、
Ｃr：０.１〜２.０％、Ｃa：０.０１％以下よりなる群
から選ばれる少なくとも１種を含有している請求項１に
記載の伸びフランジ性及び疲労特性の優れた高強度熱延
鋼板。3. The steel further comprises Mo: 0.05 to 0.5.
%, V: 0.01 to 0.2%, Zr: 0.01 to 0.2%,
The high-strength heat with excellent stretch-flangeability and fatigue characteristics according to claim 1, containing at least one selected from the group consisting of Cr: 0.1 to 2.0% and Ca: 0.01% or less. Rolled steel sheet.
２％で、かつ、０.５０＜〔(Ｔi−３.４３Ｎ−１.５Ｓ)
／４＋Ｎb／７.７５〕／Ｃの関係を満たす量のＮbと、
Ｍo：０.０５〜０.５％、Ｖ：０.０１〜０.２％、Ｚr：
０.０１〜０.２％、Ｃr：０.１〜２.０％、Ｃa：０.０
１％以下よりなる群から選ばれる少なくとも１種を含有
している請求項１に記載の伸びフランジ性及び疲労特性
の優れた高強度熱延鋼板。4. The steel further comprises Nb: 0.005-0.
2% and 0.50 <[((Ti-3.43N-1.5S))
/4+Nb/7.75]/C, and
Mo: 0.05 to 0.5%, V: 0.01 to 0.2%, Zr:
0.01-0.2%, Cr: 0.1-2.0%, Ca: 0.0
The high-strength hot-rolled steel sheet having excellent stretch-flangeability and fatigue characteristics according to claim 1, containing at least one selected from the group consisting of 1% or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09547093A JP3247194B2 (en) | 1993-03-30 | 1993-03-30 | High strength hot rolled steel sheet with excellent stretch flangeability and fatigue properties |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09547093A JP3247194B2 (en) | 1993-03-30 | 1993-03-30 | High strength hot rolled steel sheet with excellent stretch flangeability and fatigue properties |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06287685A true JPH06287685A (en) | 1994-10-11 |
| JP3247194B2 JP3247194B2 (en) | 2002-01-15 |
Family
ID=14138538
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP09547093A Expired - Fee Related JP3247194B2 (en) | 1993-03-30 | 1993-03-30 | High strength hot rolled steel sheet with excellent stretch flangeability and fatigue properties |
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| Country | Link |
|---|---|
| JP (1) | JP3247194B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998020180A1 (en) * | 1996-11-05 | 1998-05-14 | Pohang Iron & Steel Co., Ltd. | Method for manufacturing high strength and high formability hot-rolled transformation induced plasticity steel containing copper |
| JP2002105596A (en) * | 2000-09-29 | 2002-04-10 | Pohang Iron & Steel Co Ltd | Hot rolled steel sheet having high weather resistance and high workability and its production method |
| JP2009084643A (en) * | 2007-09-28 | 2009-04-23 | Kobe Steel Ltd | Hot rolled steel sheet having excellent fatigue property and stretch flange formability balance |
| JP2010024547A (en) * | 2008-06-16 | 2010-02-04 | Nippon Steel Corp | Hot rolled steel sheet having excellent hole expansibility and method for producing the same |
| US7828912B2 (en) | 2003-03-24 | 2010-11-09 | Nippon Steel Corporation | High-strength hot-rolled steel shaft excellent in hole expandability and ductility and production method thereof |
-
1993
- 1993-03-30 JP JP09547093A patent/JP3247194B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998020180A1 (en) * | 1996-11-05 | 1998-05-14 | Pohang Iron & Steel Co., Ltd. | Method for manufacturing high strength and high formability hot-rolled transformation induced plasticity steel containing copper |
| JP2002105596A (en) * | 2000-09-29 | 2002-04-10 | Pohang Iron & Steel Co Ltd | Hot rolled steel sheet having high weather resistance and high workability and its production method |
| US7828912B2 (en) | 2003-03-24 | 2010-11-09 | Nippon Steel Corporation | High-strength hot-rolled steel shaft excellent in hole expandability and ductility and production method thereof |
| JP2009084643A (en) * | 2007-09-28 | 2009-04-23 | Kobe Steel Ltd | Hot rolled steel sheet having excellent fatigue property and stretch flange formability balance |
| JP2010024547A (en) * | 2008-06-16 | 2010-02-04 | Nippon Steel Corp | Hot rolled steel sheet having excellent hole expansibility and method for producing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3247194B2 (en) | 2002-01-15 |
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