JP6189819B2 - High strength high ductility steel sheet - Google Patents
High strength high ductility steel sheet Download PDFInfo
- Publication number
- JP6189819B2 JP6189819B2 JP2014236929A JP2014236929A JP6189819B2 JP 6189819 B2 JP6189819 B2 JP 6189819B2 JP 2014236929 A JP2014236929 A JP 2014236929A JP 2014236929 A JP2014236929 A JP 2014236929A JP 6189819 B2 JP6189819 B2 JP 6189819B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel
- strength
- steel sheet
- pearlite
- 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.)
- Expired - Fee Related
Links
Description
本発明は、自動用薄鋼板などとして有用な高強度高延性鋼板に関し、詳しくは、鋼板の強度・延性バランス向上技術に関するものである。 The present invention relates to a high-strength, high-ductility steel plate useful as an automatic thin steel plate and the like, and more particularly to a technique for improving the strength / ductility balance of a steel plate.
自動車用鋼板は一般にスポット溶接性が要求されるため、Ｃ含有量が０．２質量％以下の低炭素鋼で製造されていた。しかしながら、接合技術として、摩擦撹拌接合（ＦＳＷ）や、機械締結に代表される非溶融系接合技術や、異種材料としてアルミニウムまたはアルミニウム合金を用いる場合は、鋼板側の機械的特性（以下、単に「特性」ともいう。）を劣化させない温度域での接合しか実施されないため、従来用いられていなかったＣ含有量が０．２質量％超の鋼板についても利用できる状況が生まれつつある。 Since steel plates for automobiles are generally required to have spot weldability, they have been manufactured from low carbon steel having a C content of 0.2% by mass or less. However, as a joining technique, friction stir welding (FSW), non-melting joining technique represented by mechanical fastening, or when using aluminum or an aluminum alloy as a dissimilar material, the mechanical characteristics on the steel sheet side (hereinafter simply “ Since the bonding is only performed in a temperature range that does not deteriorate the “characteristic”.), A situation that can be used even for a steel sheet having a C content of more than 0.2% by mass, which has not been used conventionally, is now emerging.
一方で、自動車用鋼板への成形性に対する要望は非常に強い。一般に超高強度鋼板（超ハイテン）に対しては、降伏強度（ＹＳ）、引張強度（ＴＳ）、伸び（ＥＬ）、伸びフランジ性（λ）といった特性が要求され、それらのバランス向上が進められているが、引張強度（ＴＳ）を一定にした場合に降伏強度（ＹＳ）と伸びフランジ性（λ）は両立できるが、伸び（ＥＬ）と降伏強度（ＹＳ）または伸びフランジ性（λ）を両立させることは難しい。 On the other hand, there is a strong demand for formability on steel sheets for automobiles. In general, for ultra-high strength steel sheets (super high tensile strength), properties such as yield strength (YS), tensile strength (TS), elongation (EL), stretch flangeability (λ) are required, and the balance between them is being improved. However, when the tensile strength (TS) is constant, the yield strength (YS) and stretch flangeability (λ) can be compatible, but the elongation (EL) and yield strength (YS) or stretch flangeability (λ) It is difficult to achieve both.
具体的な要求特性として、引張強度（ＴＳ）が９８０ＭＰａ以上において、降伏比ＹＲ（＝ＹＳ／ＴＳ）が０．８以上、引張強度（ＴＳ）×伸び（ＥＬ）が１４０００ＭＰａ・％以上で、伸びフランジ性（λ）が３５％以上を確保しうる鋼板の開発が要望されている。 As specific required characteristics, when the tensile strength (TS) is 980 MPa or more, the yield ratio YR (= YS / TS) is 0.8 or more, and the tensile strength (TS) × elongation (EL) is 14000 MPa ·% or more. There is a demand for the development of a steel sheet that can secure a flangeability (λ) of 35% or more.
９８０ＭＰａ級以上の高強度鋼板において、高強度化と高延性確保を両立させるため、これまでは残留オーステナイトによるＴＲＩＰ効果を活用したＴＲＩＰ鋼やＴＢＦ鋼等を用いる手段が検討されてきた（例えば、特許文献１〜３参照）。 In order to achieve both high strength and high ductility in a high-strength steel sheet of 980 MPa class or higher, means using TRIP steel, TBF steel, etc. utilizing the TRIP effect of retained austenite has been studied so far (for example, patents). References 1-3).
たとえば、特許文献１には、鋼組織を、フェライト、マルテンサイト、残留オーステナイトに加えて、焼き戻しマルテンサイトを含有させたものとすることで、ＴＳ−ＥＬバランスが高く、伸びフランジ性に優れた高強度溶融亜鉛めっき鋼板が提案されている。しかしながら、この技術は、高いＹＲを兼備させることを技術的思想とする本発明とは異なり、ＹＲをむしろ低下させることで加工性を確保することを意図したものであり、ＴＳ×ＥＬで２００００ＭＰａ％を超えつつ、６０％を超えるλを実現しうるものの、０．８以上のＹＲは兼備しておらず、上記要望レベルを満足させるものでない。 For example, Patent Document 1 discloses that the steel structure contains tempered martensite in addition to ferrite, martensite, and retained austenite, so that the TS-EL balance is high and the stretch flangeability is excellent. High strength hot dip galvanized steel sheets have been proposed. However, this technique is intended to ensure workability by reducing YR rather than the present invention, which has a technical idea of combining high YR. TS × EL is 20000 MPa%. Λ exceeding 60% can be realized while exceeding Y, but YR of 0.8 or more is not combined and does not satisfy the above desired level.
また、特許文献２には、Ｍｎ、ＳｉおよびＡｌの含有量を適正に制御しつつ、板厚の１／４深さにおける鋼組織を制御することで、高強度・高延性と伸びフランジ性を向上させた高強度冷延鋼板が提案されている。しかしながら、この技術も、上記特許文献１と同じく、ＹＲを低下させることで加工性を確保することを意図したものであり、少なくとも、０．８以上のＹＲは兼備しておらず、やはり上記要望レベルを満足させるものでない。 Patent Document 2 also provides high strength, high ductility and stretch flangeability by controlling the steel structure at a quarter depth of the plate thickness while appropriately controlling the contents of Mn, Si and Al. An improved high strength cold rolled steel sheet has been proposed. However, this technique is also intended to ensure workability by lowering YR, as in the above-mentioned Patent Document 1. At least YR of 0.8 or more is not used, and the above-mentioned demand is also achieved. It does not satisfy the level.
また、特許文献３には、フェライト主体の鋼組織にＴｉ、ＭｏおよびＶを含有させることで、上記要望レベルを満足する、伸びと伸びフランジ性と高降伏比を兼備した高張力冷延鋼板が提案されている。しかしながら、この技術は、フェライト主体の鋼組織をベースとするものであり、パーライト主体の鋼組織をベースとする本発明とは、そもそも技術的思想が全く異なるものである。 Patent Document 3 discloses a high-tensile cold-rolled steel sheet that combines elongation, stretch flangeability, and high yield ratio by satisfying the above-mentioned required level by including Ti, Mo, and V in a steel structure mainly composed of ferrite. Proposed. However, this technology is based on a steel structure mainly composed of ferrite, and the technical idea is completely different from the present invention based on a steel structure mainly composed of pearlite.
そこで本発明の目的は、引張強度（ＴＳ）が９８０ＭＰａ以上で、降伏比ＹＲ（＝ＹＳ／ＴＳ）が０．８以上、引張強度（ＴＳ）×伸び（ＥＬ）が１４０００ＭＰａ・％以上で、伸びフランジ性（λ）が３５％以上を確保しうる、強度−延性バランスに優れた高強度高延性鋼板を提供することにある。 Therefore, the object of the present invention is that the tensile strength (TS) is 980 MPa or more, the yield ratio YR (= YS / TS) is 0.8 or more, and the tensile strength (TS) × elongation (EL) is 14000 MPa ·% or more. An object of the present invention is to provide a high-strength, high-ductility steel sheet having an excellent balance between strength and ductility, which can ensure a flangeability (λ) of 35% or more.
本発明の第１発明に係る高強度高延性鋼板は、
成分組成が、質量％で、
Ｃ：０．４〜０．８％、
Ｓｉ：０．８〜３．０％、
Ｍｎ：０．１〜０．６％
を含み、残部が鉄および不可避的不純物からなり、
鋼組織が、全組織に対する面積率で、
パーライトを８０％以上、
残留オーステナイトを５％以上
含むとともに、
前記パーライトの平均ラメラ間隔が０．５μｍ以下であり、
方位差１５°以上の大角粒界で囲まれたフェライトの有効結晶粒径が２０μｍ以下であり、かつ、
円相当直径０．１μｍ以上の炭化物が４００μｍ２当たり５個以下である
ことを特徴とする。
The high strength and high ductility steel sheet according to the first invention of the present invention is
Ingredient composition is mass%,
C: 0.4-0.8%
Si: 0.8 to 3.0%,
Mn: 0.1 to 0.6%
The balance consists of iron and inevitable impurities,
The steel structure is the area ratio of the whole structure,
More than 80% perlite,
Containing more than 5% residual austenite,
An average lamellar spacing of the pearlite is 0.5 μm or less,
The effective crystal grain size of the ferrite surrounded by the large-angle grain boundary with an orientation difference of 15 ° or more is 20 μm or less, and
The number of carbides having an equivalent circle diameter of 0.1 μm or more is 5 or less per 400 μm 2 .
本発明の第２発明に係る高強度高延性鋼板は、
上記第１発明において、
成分組成が、質量％で、さらに、
Ｃｕ、Ｎｉ、ＣｒおよびＭｏの１種または２種以上を合計で０．５％以下含むものである。
The high strength and high ductility steel sheet according to the second invention of the present invention is
In the first invention,
Ingredient composition is mass%, and
One or two or more of Cu, Ni, Cr and Mo are included in total of 0.5% or less.
本発明の第３発明に係る高強度高延性鋼板は、
上記第１または第２発明において、
成分組成が、質量％で、さらに、
Ｖ、ＴｉおよびＮｂの１種または２種以上を合計で０．２％以下含むものである。
The high strength and high ductility steel sheet according to the third aspect of the present invention is
In the first or second invention,
Ingredient composition is mass%, and
One or more of V, Ti, and Nb is included in a total of 0.2% or less.
本発明によれば、パーライトを主要組織としつつ、そのラメラ間隔を小さくして降伏強度（ＹＳ）を高めるとともに、有効フェライト粒を微細化することで伸びフランジ性（λ）を高め、さらに残留オーステナイトを分散させることで伸び（ＥＬ）を高めることによって、引張強度（ＴＳ）が９８０ＭＰａ以上で、降伏比ＹＲ（＝ＹＳ／ＴＳ）が０．８以上、引張強度（ＴＳ）×伸び（ＥＬ）が１４０００ＭＰａ・％以上で、伸びフランジ性（λ）が３５％以上を確保しうる、強度−延性バランスに優れた高強度高延性鋼板を提供できるようになった。 According to the present invention, while the pearlite is a main structure, the lamella spacing is reduced to increase the yield strength (YS), and the effective ferrite grains are refined to increase the stretch flangeability (λ) and further to retained austenite. The tensile strength (TS) is 980 MPa or more, the yield ratio YR (= YS / TS) is 0.8 or more, and the tensile strength (TS) × elongation (EL) is increased by increasing the elongation (EL) by dispersing It has become possible to provide a high-strength, high-ductility steel sheet excellent in strength-ductility balance that can ensure stretch flangeability (λ) of 35% or more at 14000 MPa ·% or more.
本発明者らは、上記課題を解決するために、パーライト鋼からなる鋼板において、その機械的特性として、引張強度（ＴＳ）が９８０ＭＰａ以上で、降伏比（ＹＲ［＝ＹＳ／ＴＳ］）が０．８以上、引張強度（ＴＳ）×伸び（ＥＬ）が１４０００ＭＰａ・％以上で、伸びフランジ性（λ）が３５％以上を確保しうる方策について種々検討を重ねてきた。 In order to solve the above-mentioned problems, the inventors of the present invention have a tensile strength (TS) of 980 MPa or more and a yield ratio (YR [= YS / TS]) of 0 in a steel plate made of pearlite steel. Various studies have been made on measures that can ensure that the tensile strength (TS) × elongation (EL) is 14000 MPa ·% or more and the stretch flangeability (λ) is 35% or more.
上記検討の結果、微細なラメラ状のセメンタイトとフェライトで構成されるために降伏強度（ＹＳ）、引張強度（ＴＳ）および伸びフランジ性（λ）に優れるパーライト組織を母相組織としつつ、そのラメラ間隔を微細にして特に降伏強度（ＹＳ）を高めるとともに、パーライトの局部変形能を支配する有効フェライト径を微細にすることで伸びフランジ性（λ）を高め、さらに残留オーステナイト（以下、「残留γ」とも表記する。）を分散させることで伸び（ＥＬ）を高めることが可能なことを見出した。 As a result of the above studies, the lamellae is composed of a pearlite structure that is excellent in yield strength (YS), tensile strength (TS) and stretch flangeability (λ) because it is composed of fine lamellar cementite and ferrite. In addition to increasing the yield strength (YS) by reducing the spacing and increasing the effective ferrite diameter that governs the local deformability of the pearlite, the stretch flangeability (λ) is improved, and residual austenite (hereinafter referred to as “residual γ” It was also found that the elongation (EL) can be increased by dispersing.
そして、本発明者らは、上記知見に基づいてさらに検討を進めた結果、本発明を完成するに至った。 Then, as a result of further investigation based on the above findings, the present inventors have completed the present invention.
以下、まず本発明に係る高強度高延性鋼板（以下、「本発明鋼板」ともいう。）を特徴づける鋼組織（以下、単に「組織」ということもある。）について説明する。 Hereinafter, a steel structure (hereinafter sometimes simply referred to as “structure”) that characterizes the high-strength and highly ductile steel sheet (hereinafter also referred to as “the steel sheet of the present invention”) according to the present invention will be described.
〔本発明鋼板の鋼組織〕
上述したとおり、本発明鋼板は、パーライトを主要組織として残留γを所定量含有するものであるが、パーライトのラメラ間隔、有効フェライト粒径および炭化物の存在密度が制御されている点に特徴を有するものである。
[Steel structure of the steel sheet of the present invention]
As described above, the steel sheet of the present invention contains pearlite as a main structure and contains a predetermined amount of residual γ, and is characterized in that the pearlite lamellar spacing, the effective ferrite grain size, and the abundance of carbides are controlled. Is.
＜パーライト：全組織に対する面積率で８０％以上＞
均一かつ微細なラメラ状のフェライトとセメンタイトが混在する組織であるパーライトを母相とすることで、降伏強度（ＹＳ）、引張強度（ＴＳ）および伸びフランジ性（λ）を高めることができる。このような作用を有効に発揮させるためには、パーライトは全組織に対する面積率で８０％以上、好ましくは８５％以上、さらに好ましくは９０％以上存在させることが必要である。
<Perlite: 80% or more in area ratio with respect to the whole structure>
Yield strength (YS), tensile strength (TS), and stretch flangeability (λ) can be improved by using pearlite, which is a structure in which uniform and fine lamellar ferrite and cementite are mixed, as a parent phase. In order to effectively exhibit such an action, it is necessary that pearlite is present in an area ratio of 80% or more, preferably 85% or more, more preferably 90% or more with respect to the entire structure.
＜残留γ：全組織に対する面積率で５％以上＞
残留γは延性の向上に有用であり、このような作用を有効に発揮させるためには、全組織に対する面積率で５％以上、好ましくは５．５％以上、さらに好ましくは６％以上存在させることが必要である。
なお、パーライトおよび残留γ以外の残部組織として、初析フェライトの他、ベイナイトやマルテンサイトおよびそれらの焼戻し組織の混入が許容できる。
<Residual γ: Area ratio of 5% or more with respect to all tissues>
Residual γ is useful for improving ductility, and in order to effectively exhibit such action, the area ratio with respect to the whole tissue is 5% or more, preferably 5.5% or more, more preferably 6% or more. It is necessary.
In addition to the proeutectoid ferrite, bainite, martensite and their tempered structures can be mixed as the remaining structure other than pearlite and residual γ.
＜パーライトの平均ラメラ間隔：０．５μｍ以下＞
パーライトを構成するフェライトとセメンタイトの間隔を微細化することで、フェライト中に存在する転位の平均自由行程を短くすることによって降伏強度（ＹＳ）を高めることができる。所要の降伏強度（ＹＳ）を得るためには、パーライトの平均ラメラ間隔は０．５μｍ以下、好ましくは０．４μｍ以下、さらに好ましくは０．３μｍ以下とする必要がある。
<Average lamella spacing of pearlite: 0.5 μm or less>
Yield strength (YS) can be increased by reducing the mean free path of dislocations present in ferrite by reducing the distance between ferrite and cementite constituting pearlite. In order to obtain the required yield strength (YS), it is necessary that the average lamella spacing of pearlite is 0.5 μm or less, preferably 0.4 μm or less, more preferably 0.3 μm or less.
＜方位差１５°以上の大角粒界で囲まれたフェライトの有効結晶粒径が２０μｍ以下＞
変形の単位となる同じ結晶方位を向いた領域（「ブロック」または「ノジュール」とも呼ばれる。）のサイズを微細化することで、破壊を防止し、伸びフランジ性（λ）を向上させることができる。所要の伸びフランジ性（λ）を得るためには、方位差１５°以上の大角粒界で囲まれたフェライトの有効結晶粒径（「有効フェライト粒径」ともいう。）は２０μｍ以下、好ましくは１８μｍ以下、さらに好ましくは１６μｍ以下とする必要がある。
<Effective crystal grain size of ferrite surrounded by large-angle grain boundaries with an orientation difference of 15 ° or more is 20 μm or less>
By reducing the size of a region (also referred to as “block” or “nodule”) facing the same crystal orientation as a unit of deformation, breakage can be prevented and stretch flangeability (λ) can be improved. . In order to obtain the required stretch flangeability (λ), the effective crystal grain size (also referred to as “effective ferrite grain size”) of ferrite surrounded by a large-angle grain boundary having an orientation difference of 15 ° or more is preferably 20 μm or less, preferably It is necessary to make it 18 μm or less, more preferably 16 μm or less.
＜円相当直径０．１μｍ以上の炭化物：４００μｍ２当たり５個以下＞
破壊の起点となる粗大な球状炭化物を減少させることで、破壊を防止することができる。このような作用を有効に発揮させるためには、円相当直径０．１μｍ以上の炭化物は４００μｍ２当たり５個以下、好ましくは４個以下、さらに好ましくは３個以下とする必要がある。
<Carbide with equivalent circle diameter of 0.1 μm or more: 5 or less per 400 μm 2 >
By reducing the coarse spherical carbide that is the starting point of the destruction, the destruction can be prevented. In order to effectively exhibit such an action, it is necessary to reduce the number of carbides having an equivalent circle diameter of 0.1 μm or more to 5 or less, preferably 4 or less, more preferably 3 or less per 400 μm 2 .
〔パーライトおよび残留γの面積率、パーライトの平均ラメラ間隔、有効フェライト粒径、ならびに、球状炭化物のサイズおよびその存在密度の各測定方法〕
ここで、パーライトおよび残留γの面積率、パーライトの平均ラメラ間隔、有効フェライト粒径、ならびに、球状炭化物のサイズおよびその存在密度の各測定方法について説明する。
[Measurement method of area ratio of pearlite and residual γ, average lamella spacing of pearlite, effective ferrite particle size, and size and density of spherical carbide]
Here, each measuring method of the area ratio of pearlite and residual γ, the average lamella spacing of pearlite, the effective ferrite particle size, and the size and density of the spherical carbide will be described.
＜パーライト面積率の測定方法＞
パーライトの面積率は、鋼板を切断して板厚方向断面を鏡面研磨した試料をピクラール（ピクリン酸５％＋エタノール）でエッチングし、板厚の１／４位置における組織を倍率１５００倍で５視野のＳＥＭ（走査型電子顕微鏡）観察を行い、点算法によって求めた。
<Measurement method of pearlite area ratio>
The area ratio of pearlite was determined by etching a steel plate cut and mirror-polished the cross section in the thickness direction with picral (5% picric acid + ethanol), and viewing the structure at 1/4 position of the plate thickness at a magnification of 1500 times for 5 fields of view. Was observed by SEM (scanning electron microscope) and obtained by a point arithmetic method.
＜残留γの面積率の測定方法＞
残留γの面積率は、鋼板の１／４の厚さまで研削した後、化学研磨してからＸ線回折法により測定した（ＩＳＩＪ Ｉｎｔ．Ｖｏｌ．３３，（１９３３），Ｎｏ．７，ｐ．７７６）。なお、本発明においては、Ｘ線回折装置として、（株）リガク製 ２次元微小部Ｘ線回折装置（ＲＩＮＴ−ＲＡＰＩＤII）を用い、Ｘ線としてＣｏ−Ｋα線を用いた。
<Measurement method of area ratio of residual γ>
The area ratio of residual γ was measured by X-ray diffraction after grinding to a thickness of ¼ of the steel sheet (ISIJ Int. Vol. 33, (1933), No. 7, p. 776). ). In the present invention, a two-dimensional micro part X-ray diffractometer (RINT-RAPIDII) manufactured by Rigaku Corporation was used as the X-ray diffractometer, and a Co-Kα ray was used as the X-ray.
＜パーライトの平均ラメラ間隔の測定方法＞
パーライトの平均ラメラ間隔は、上記パーライトの面積率の測定と同様にして板厚方向断面試料を作製し、板厚の１／４位置を倍率５０００倍で１０枚写真撮影し、各写真において最も微細なラメラを決定し、このラメラに直角となるように線分を引き、その線分の長さと線分を横切るラメラの数からラメラ間隔を求め、合計１０本の線分について測定したラメラ間隔を平均することによって求めた。
<Measuring method of average lamella spacing of pearlite>
The average lamella spacing of the pearlite is the same as the measurement of the area ratio of the pearlite. A cross-sectional sample in the plate thickness direction is prepared, and 10 photographs are taken at a magnification of 5000 times at a 1/4 position of the plate thickness. The lamella spacing is determined from the length of the line segment and the number of lamellas crossing the line segment, and the lamella spacing measured for a total of 10 line segments is determined. Obtained by averaging.
＜有効フェライト粒径の測定方法＞
有効フェライト粒径は、上記パーライトの面積率の測定と同様にして板厚方向断面試料を作製し、板厚１／４位置について、ＥＢＳＰ解析装置およびＦＥ−ＳＥＭを用いてステップ間隔０．２５μｍの測定条件にて３視野測定し、以下のようにして求めた。すなわち、フェライト−フェライト間の結晶方位差が１５°以上となる点を有効結晶粒界としてフェイズマップ上にマッピングし、有効結晶粒界で囲まれたフェライト相の面積を画像解析ソフトを用いて測定し、各粒の面積から円相当直径を求め、その平均値を有効フェライト粒径とした。なお、本発明の実施例においては、ＥＢＳＰ解析装置として、テクセムラボラトリーズ製ＯＩＭシステム（ｖｅｒ．４．０）を、ＦＥ−ＳＥＭとして、フィリップス社製ＸＬ３０Ｓ−ＦＥＧを、画像解析ソフトとして、フィリップス社製Ｉｍａｇｅ−Ｐｒｏを、それぞれ用いた。
<Measurement method of effective ferrite particle size>
The effective ferrite particle size was prepared in the same manner as in the measurement of the area ratio of pearlite, and a cross-sectional sample in the plate thickness direction was prepared. At the plate thickness 1/4 position, the step interval was 0.25 μm using an EBSP analyzer and FE-SEM. Three fields of view were measured under the measurement conditions and determined as follows. In other words, the point where the crystal orientation difference between ferrite and ferrite is 15 ° or more is mapped on the phase map as an effective grain boundary, and the area of the ferrite phase surrounded by the effective grain boundary is measured using image analysis software The equivalent circle diameter was determined from the area of each grain, and the average value was defined as the effective ferrite grain diameter. In the embodiment of the present invention, as an EBSP analyzer, an OIM system (ver. 4.0) manufactured by Texemra Laboratories is used, as an FE-SEM, XL30S-FEG manufactured by Philips is used as image analysis software, and Philips is used. Image-Pro made by each was used.
＜球状炭化物のサイズおよびその存在密度の測定方法＞
球状炭化物のサイズおよびその存在密度については、鋼板の抽出レプリカサンプルを作製し、０．８μｍ×１μｍの領域３視野について倍率１０００００倍のＴＥＭ（透過型電子顕微鏡）像を観察した。そして、画像のコントラストから白い部分を炭化物粒子と判別してマーキングし、画像解析ソフトにて、前記マーキングした各炭化物粒子の面積から円相当直径を算出するとともに、４００μｍ２当りに存在する、円相当直径０．１μｍ以上の炭化物粒子の個数を求めた。なお、複数個の炭化物粒子が重なり合う部分は観察対象から除外した。なお、本発明の実施例においては、画像解析ソフトとして、上記と同じく、フィリップス社製Ｉｍａｇｅ−Ｐｒｏを用いた。
<Method for Measuring Size of Spherical Carbide and Its Abundance>
As for the size of the spherical carbide and its density, an extraction replica sample of a steel plate was prepared, and a TEM (transmission electron microscope) image with a magnification of 100,000 was observed with respect to three fields of 0.8 μm × 1 μm. Then, the white portion is marked by marking from the contrast of the image as carbide particles, and with the image analysis software, the equivalent circle diameter is calculated from the area of each marked carbide particle, and the circle equivalent exists per 400 μm 2. The number of carbide particles having a diameter of 0.1 μm or more was determined. In addition, the part which a some carbide particle overlaps was excluded from the observation object. In the embodiment of the present invention, Image-Pro manufactured by Philips was used as the image analysis software as described above.
次に、本発明鋼板を構成する成分組成について説明する。以下、化学成分の単位はすべて質量％である。また、各成分の「含有量」を単に「量」と記載することもある。 Next, the component composition which comprises this invention steel plate is demonstrated. Hereinafter, all the units of chemical components are mass%. In addition, “content” of each component may be simply referred to as “amount”.
〔本発明鋼板の成分組成〕
Ｃ：０．４〜０．８％
Ｃは、パーライト組織および残留オーステナイト組織を実現するため、従来鋼より多量に含有させる必要がある。このような作用を有効に発揮させるためには、Ｃを０．４％以上、好ましくは０．４５％以上、さらに好ましくは０．５％以上含有させる必要がある。ただし、Ｃ量が過剰になると、過共析領域となり、粗大なセメンタイトが形成されて延性を劣化させるので、Ｃ量は０．８％以下、好ましくは０．７５％以下、さらに好ましくは０．７％以下とする。
[Component composition of the steel sheet of the present invention]
C: 0.4 to 0.8%
In order to realize a pearlite structure and a retained austenite structure, C needs to be contained in a larger amount than conventional steel. In order to effectively exhibit such an action, it is necessary to contain C by 0.4% or more, preferably 0.45% or more, and more preferably 0.5% or more. However, if the amount of C becomes excessive, it becomes a hypereutectoid region, and coarse cementite is formed and ductility is deteriorated. Therefore, the amount of C is 0.8% or less, preferably 0.75% or less, more preferably 0.8. 7% or less.
Ｓｉ：０．８〜３．０％
Ｓｉは、残留オーステナイトが分解して炭化物が生成するのを有効に抑制する元素である。このような作用を有効に発揮させるためには、Ｓｉを０．８％以上、好ましくは０．９％以上、さらに好ましくは１．０％以上含有させる必要がある。ただし、Ｓｉを過剰に含有させても、上記効果が飽和してしまい、経済的に無駄であるばかりでなく、熱間脆性を引き起こすため、Ｓｌは３．０％以下、好ましくは２．５％以下、さらに好ましくは２．０％以下とする。
Si: 0.8-3.0%
Si is an element that effectively suppresses the decomposition of retained austenite and the formation of carbides. In order to effectively exhibit such an action, it is necessary to contain Si by 0.8% or more, preferably 0.9% or more, and more preferably 1.0% or more. However, even if Si is contained excessively, the above effect is saturated and not only is economically wasteful but also causes hot brittleness. Therefore, Sl is 3.0% or less, preferably 2.5%. Hereinafter, it is more preferably 2.0% or less.
Ｍｎ：０．１〜０．６％
Ｍｎは、フェライトの形成を防止するために一定量の含有が必要である。このような作用を有効に発揮させるためには、Ｍｎを０．１％ 以上、好ましくは０．１５％以上、さらに好ましくは０．２％以上含有させることが必要である。ただし、Ｍｎ量が過剰になると、パーライトの形成を抑制してベイナイトが形成されるため、Ｍｎ量は従来鋼より低減する必要があり、０．６％以下、好ましくは０．５５％以下、さらに好ましくは０．５％以下とする。
Mn: 0.1 to 0.6%
Mn needs to be contained in a certain amount in order to prevent the formation of ferrite. In order to effectively exhibit such an action, it is necessary to contain Mn in an amount of 0.1% or more, preferably 0.15% or more, more preferably 0.2% or more. However, when the amount of Mn becomes excessive, the formation of pearlite is suppressed and bainite is formed. Therefore, the amount of Mn needs to be reduced from that of the conventional steel, and is 0.6% or less, preferably 0.55% or less. Preferably it is 0.5% or less.
本発明の鋼は上記元素を必須の成分として含有し、残部は鉄および不可避的不純物であるが、不可避的不純物のうち、Ｐは０．０５％以下、さらには０．０３％以下、特に０．０２％以下に、Ｓは０．０１％以下、さらには０．００５％以下、特に０．００３％以下に、Ａｌは０．２％以下、さらには０．１５％以下、特に０．１％以下に、それぞれ制限するのが推奨される。 The steel of the present invention contains the above elements as essential components, and the balance is iron and unavoidable impurities. Among the unavoidable impurities, P is 0.05% or less, further 0.03% or less, particularly 0. 0.02% or less, S is 0.01% or less, further 0.005% or less, particularly 0.003% or less, Al is 0.2% or less, further 0.15% or less, particularly 0.1% or less. It is recommended to limit each to below%.
本発明の鋼は、その他、本発明の作用を損なわない範囲で、以下の許容成分を含有させることができる。 In addition, the steel of the present invention can contain the following permissible components as long as the effects of the present invention are not impaired.
Ｃｕ、Ｎｉ、ＣｒおよびＭｏの１種または２種以上：合計で０．５％以下
これらの元素は、鋼の強化元素として有用であるとともに、残留γの安定化や所定量の確保に有効な元素である。このような作用を有効に発揮させるためには、これらの元素は合計量で０．００１％以上、さらには０．０１％以上含有させることが推奨される。ただし、これらの元素を過剰に含有させても上記効果が飽和してしまい、経済的に無駄であるので、これらの元素は合計量で０．５％以下、さらには０．３％以下とするのが好ましい。
One or more of Cu, Ni, Cr and Mo: 0.5% or less in total These elements are useful as steel strengthening elements and are effective for stabilizing residual γ and securing a predetermined amount. It is an element. In order to effectively exhibit such an action, it is recommended that these elements are contained in a total amount of 0.001% or more, and further 0.01% or more. However, even if these elements are contained excessively, the above effect is saturated and is economically wasteful. Therefore, these elements are added in a total amount of 0.5% or less, and further 0.3% or less. Is preferred.
Ｖ、ＴｉおよびＮｂの１種または２種以上：合計で０．２％以下
これらの元素は、析出強化および組織微細化の効果があり、高強度化に有用な元素である。このような作用を有効に発揮させるためには、これらの元素を合計量で０．０１％以上、さらには０．０２％以上含有させることが推奨される。ただし、これらの元素を過剰に含有させても、上記効果が飽和してしまい、経済的に無駄であるので、これらの元素は合計量で０．２％以下、さらには０．１％以下とするのが好ましい。
One or more of V, Ti and Nb: 0.2% or less in total These elements have effects of precipitation strengthening and refinement of the structure, and are useful elements for increasing the strength. In order to effectively exhibit such an action, it is recommended that these elements are contained in a total amount of 0.01% or more, and further 0.02% or more. However, even if these elements are contained excessively, the above effects are saturated and economically useless. Therefore, these elements are 0.2% or less in total amount, and further 0.1% or less. It is preferable to do this.
次に、上記本発明鋼板を得るための好ましい製造条件を以下に説明する。 Next, preferable production conditions for obtaining the steel sheet of the present invention will be described below.
〔本発明鋼板の好ましい製造方法〕
本発明鋼板は、上記成分組成を満足する鋼材を、熱間圧延し、ついで冷間圧延した後、例えば下記の工程（１）〜（３）の条件にて熱処理を行って製造することができる（図２参照）。
[Preferred production method of the steel sheet of the present invention]
The steel sheet of the present invention can be manufactured by hot-rolling a steel material satisfying the above component composition, followed by cold rolling, and then performing a heat treatment, for example, under the conditions of the following steps (1) to (3). (See FIG. 2).
［熱処理条件］
（１）冷延板を均熱温度Ｔ１：Ａｃ３〜［Ａｃ３＋１００℃］に加熱してその温度で均熱時間ｔ１：５〜３６００ｓ保持した後、
（２）上記均熱温度Ｔ１から後記冷却停止温度Ｔ２までを平均冷却速度ＣＲ：１０℃／ｓ以上で冷却した後、
（３）冷却停止温度Ｔ２：３００〜５００℃で保持時間ｔ２：１０〜１２００ｓ保持後、室温まで冷却する。
[Heat treatment conditions]
(1) After heating the cold-rolled plate to a soaking temperature T1: Ac3 to [Ac3 + 100 ° C.] and keeping the soaking time t1: 5 to 3600 s,
(2) After cooling from the soaking temperature T1 to the cooling stop temperature T2 described below at an average cooling rate CR: 10 ° C./s or more,
(3) Cooling stop temperature T2: Hold at 300 to 500 ° C. and hold time t2: 10 to 1200 s, and then cool to room temperature.
以下、上記熱処理条件が推奨される理由について説明する。 Hereinafter, the reason why the heat treatment conditions are recommended will be described.
＜均熱温度Ｔ１：Ａｃ３〜［Ａｃ３＋１００℃］で均熱時間ｔ１：５〜３６００ｓ保持＞
鋼組織をオーステナイト化するためにオーステナイト単相域の温度で所定時間加熱（均熱）する必要があるので、均熱温度Ｔ１はＡｃ３以上、さらには［Ａｃ３＋１０℃］以上、特に「Ａｃ３＋２０℃」以上で、均熱時間ｔ１は５ｓ以上、さらには２０ｓ以上、特に６０ｓ以上とするのが推奨される。ただし、均熱温度Ｔ１を高くしすぎたり、均熱時間ｔ１を長くしすぎたりすると、オーステナイト粒が粗大化してその後の冷却過程で形成されるパーライトの有効フェライト粒径が過大となり局部延性が劣化するので、均熱温度Ｔ１は［Ａｃ３＋１００℃］以下、さらには［Ａｃ３＋９０℃］以下、特に［Ａｃ３＋８０℃］以下で、均熱時間ｔ１は３６００ｓ以下、さらには１２００ｓ以下、特に３００ｓ以下とするのが推奨される。なお、均熱時間ｔ１を長くしすぎることには生産性が低下する問題も生じる。
なお、Ａｃ３は、鋼板の化学成分から、レスリー著、「鉄鋼材料科学」、幸田成靖 訳、丸善株式会社、１９８５年、ｐ．２７３に記載の式より、下記式（１）を用いて求めることができる。
Ａｃ３（℃）＝９１０−２０３√［Ｃ］＋４４．７［Ｓｉ］−３０［Ｍｎ］＋７００［Ｐ］＋４００［Ａｌ］＋４００［Ｔｉ］＋１０４［Ｖ］−１１［Ｃｒ］＋３１．５［Ｍｏ］−２０［Ｃｕ］−１５．２［Ｎｉ］・・・式（１）
ただし、［ ］は、各元素の含有量（質量％）を示す。
<Soaking temperature T1: Ac3 to [Ac3 + 100 ° C.] soaking time t1: 5 to 3600 s>
Since it is necessary to heat (soak) for a predetermined time at the temperature of the austenite single phase region in order to austenitize the steel structure, the soaking temperature T1 is Ac3 or higher, further [Ac3 + 10 ° C.] or higher, particularly “Ac3 + 20 ° C.” or higher. Thus, it is recommended that the soaking time t1 is 5 s or more, further 20 s or more, and particularly 60 s or more. However, if the soaking temperature T1 is set too high or the soaking time t1 is set too long, the austenite grains become coarse and the effective ferrite grain size of the pearlite formed in the subsequent cooling process becomes excessive, and the local ductility deteriorates. Therefore, the soaking temperature T1 is [Ac3 + 100 ° C.] or less, further [Ac3 + 90 ° C.] or less, particularly [Ac3 + 80 ° C.] or less, and the soaking time t1 is 3600 s or less, further 1200 s or less, particularly 300 s or less. Recommended. If the soaking time t1 is too long, there is a problem that productivity is lowered.
Ac3 is derived from the chemical composition of the steel sheet, by Lesley, “Iron & Steel Materials Science”, translated by Koda Narumi, Maruzen Co., Ltd., 1985, p. From the equation described in H.273, the following equation (1) can be used.
Ac3 (° C.) = 910−203√ [C] +44.7 [Si] −30 [Mn] +700 [P] +400 [Al] +400 [Ti] +104 [V] −11 [Cr] +31.5 [Mo] −20 [Cu] -15.2 [Ni] (1)
However, [] shows content (mass%) of each element.
＜（２）均熱温度Ｔ１から冷却停止温度Ｔ２までを平均冷却速度ＣＲ：１０℃／ｓ以上で冷却＞
フェライトの形成を防止するために一定以上の冷却速度で冷却を行う必要があるので、平均冷却速度ＣＲは１０℃／ｓ以上、さらには１５℃／ｓ以上、特に２０℃／ｓ以上とするのが推奨される。
<(2) Cooling from the soaking temperature T1 to the cooling stop temperature T2 at an average cooling rate CR: 10 ° C./s or higher>
In order to prevent the formation of ferrite, it is necessary to perform cooling at a constant cooling rate or more, so the average cooling rate CR is 10 ° C./s or more, more preferably 15 ° C./s or more, particularly 20 ° C./s or more. Is recommended.
＜（３）冷却停止温度Ｔ２：３００〜５００℃で保持時間ｔ２：１０〜１２００ｓ保持＞
パーライトを形成させるとともに、残留γを残存させるためにパーライト変態を促進させて、均一な組織を形成しつつ、その際に形成されるパーライトのラメラ間隔を微細化して降伏応力を高める。また、変態時間を適正に調整することで、残留γを残存させて伸びを確保するとともに、パーライト中の炭化物（セメンタイト）の球状化を防止し、球状炭化物の形成を防止する。このような作用を有効に発揮させるため、冷却停止温度Ｔ２は３００〜５００℃、さらには３２０〜４８０℃、特に３４０〜４６０℃とし、保持時間ｔ２は１０〜１２００ｓ、さらには１５〜１０００ｓ、特に２０〜８００ｓとするのが推奨される。
<(3) Cooling stop temperature T2: 300 to 500 ° C. and holding time t2: 10 to 1200 s>
In addition to forming pearlite, pearlite transformation is promoted to leave residual γ to form a uniform structure, and the lamella spacing of the pearlite formed at that time is refined to increase yield stress. Further, by appropriately adjusting the transformation time, the residual γ remains to ensure elongation, and the carbide (cementite) in the pearlite is prevented from being spheroidized, thereby preventing the formation of the spherical carbide. In order to effectively exhibit such an action, the cooling stop temperature T2 is 300 to 500 ° C., further 320 to 480 ° C., particularly 340 to 460 ° C., and the holding time t2 is 10 to 1200 s, further 15 to 1000 s, particularly 20 to 800 s is recommended.
以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することももちろん可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
下記表１に示す成分の鋼を真空溶製で製造した後、熱間鍛造で板厚２５ｍｍの鋼板にした後、熱間圧延を施した。熱間圧延の条件は、本発明鋼板の最終組織および特性に本質的な影響を及ぼさないが、本実施例では１１５０℃に加熱し３０ｍｉｎ保持した後、２．５ｍｍまで圧延して熱延板とした。この熱延板に酸洗を施して表面のスケールを除去した後、１．６ｍｍまで冷間圧延を施して冷延板とした。 Steels having the components shown in Table 1 below were manufactured by vacuum melting, and then steel plates having a thickness of 25 mm were formed by hot forging, followed by hot rolling. The hot rolling conditions do not substantially affect the final structure and properties of the steel sheet of the present invention, but in this example, after heating to 1150 ° C. and holding for 30 min, rolling to 2.5 mm and hot rolling did. The hot-rolled sheet was pickled to remove the surface scale, and then cold-rolled to 1.6 mm to obtain a cold-rolled sheet.
そして、上記冷延板を出発材として、下記表２に示す条件で熱処理を施した。 And it heat-processed on the conditions shown in following Table 2 by using the said cold rolled sheet as a starting material.
上記熱処理後の各鋼板について、上記［発明を実施するための形態］の項で説明した測定方法により、パーライトおよび残留γの面積率、パーライトの平均ラメラ間隔、有効フェライト粒径、ならびに、球状炭化物のサイズおよびその存在密度を測定した。 For each steel plate after the heat treatment, the area ratio of pearlite and residual γ, the average lamella spacing of pearlite, the effective ferrite particle size, and the spherical carbide were measured according to the measurement method described in the above section [Mode for Carrying Out the Invention]. The size and the density of existence were measured.
また、上記熱処理後の各鋼板について、強度−延性バランスを評価するために、引張試験により、降伏強度ＹＳ、引張強度ＴＳおよび伸び（全伸び）ＥＬを測定した。なお、引張試験は、ＪＩＳ ５号試験片を作製して、ＪＩＳ Ｚ ２２４１に従って実施した。また、各鋼板の伸びフランジ性λを評価するため、日本鉄鋼連盟規格ＪＦＳＴ１００１に準じて穴広げ率を測定した。 Moreover, in order to evaluate the strength-ductility balance for each steel plate after the heat treatment, the yield strength YS, the tensile strength TS, and the elongation (total elongation) EL were measured by a tensile test. In addition, the tension test produced the JIS No. 5 test piece and implemented according to JISZ2241. Further, in order to evaluate the stretch flangeability λ of each steel plate, the hole expansion ratio was measured according to the Japan Iron and Steel Federation standard JFST1001.
測定結果を下記表３に示す。同表において、上記熱処理後の鋼板の特性が、引張強度（ＴＳ）が９８０ＭＰａ以上で、降伏比ＹＲ（＝ＹＳ／ＴＳ）が０．８以上、引張強度（ＴＳ）×伸び（ＥＬ）が１４０００ＭＰａ・％以上で、伸びフランジ性（λ）が３５％以上のものを合格（○）とし、それ以外のものを不合格（×）とした。 The measurement results are shown in Table 3 below. In the table, the properties of the steel plate after the heat treatment are as follows: tensile strength (TS) is 980 MPa or more, yield ratio YR (= YS / TS) is 0.8 or more, tensile strength (TS) × elongation (EL) is 14000 MPa. When the stretch flangeability (λ) was 35% or more with% or more, it was determined to be acceptable (◯), and the others were determined to be unacceptable (×).
上記表３に示すように、発明鋼（評価が○のもの）である鋼Ｎｏ．１〜３、１３〜２３は、本発明の成分規定の要件を満足する鋼種を用い、推奨の条件で熱処理した結果、本発明の組織規定の要件を充足する発明鋼であり、機械的特性が合格基準を満たしており、強度−延性バランスに優れた高強度強延性鋼板が得られることを確認できた。 As shown in Table 3 above, the steel No., which is an inventive steel (evaluation is ○). 1-3, 13-23 are invention steels that satisfy the requirements of the structure provision of the present invention as a result of heat treatment under the recommended conditions using steel types that satisfy the requirements of the composition provision of the present invention, and have mechanical properties. It has been confirmed that a high-strength and ductile steel sheet satisfying the acceptance criteria and having an excellent strength-ductility balance can be obtained.
これに対して、比較鋼（評価が×のもの）である鋼Ｎｏ．４〜１２は、本発明の成分規定および組織規定の要件の少なくともいずれかを充足せず、特性が合格基準を満たしていない。 On the other hand, steel No. which is a comparative steel (evaluation of x) Nos. 4 to 12 do not satisfy at least one of the component provision and the structure provision of the present invention, and the characteristics do not satisfy the acceptance criteria.
すなわち、鋼Ｎｏ．６、７、１０〜１２は、本発明の成分規定の要件を満足する鋼種を用いているものの、推奨の製造条件を一部外れる条件で製造しているため、組織規定の要件を充足せず、特性が劣っている。 That is, Steel No. Although 6, 7, and 10-12 use steel types that satisfy the requirements of the component provisions of the present invention, they are manufactured under conditions that partially deviate from the recommended production conditions, so the requirements of the organization provisions are not met. The characteristics are inferior.
一方、鋼Ｎｏ．４、５、８、９は、推奨の製造条件で製造しているものの、本発明の成分規定の要件を一部外れる鋼種を用いているため、組織規定の要件を充足せず、特性が劣っている。 On the other hand, Steel No. Although 4, 5, 8, and 9 are manufactured under the recommended manufacturing conditions, steel grades that partially deviate from the requirements of the component provision of the present invention are used, so the requirements of the structure provision are not satisfied and the characteristics are inferior. ing.
以上より、本発明の適用性が確認された。 From the above, the applicability of the present invention was confirmed.
Claims (3)
Ｃ：０．４〜０．８％、
Ｓｉ：０．８〜３．０％、
Ｍｎ：０．１〜０．６％
を含み、残部が鉄および不可避的不純物からなり、
鋼組織が、全組織に対する面積率で、
パーライトを８０％以上、
残留オーステナイトを５％以上
含むとともに、
前記パーライトの平均ラメラ間隔が０．５μｍ以下であり、
方位差１５°以上の大角粒界で囲まれたフェライトの有効結晶粒径が２０μｍ以下であり、かつ、
円相当直径０．１μｍ以上の炭化物が４００μｍ２当たり５個以下である
ことを特徴とする高強度高延性鋼板。 Ingredient composition is mass%,
C: 0.4-0.8%
Si: 0.8 to 3.0%,
Mn: 0.1 to 0.6%
The balance consists of iron and inevitable impurities,
The steel structure is the area ratio of the whole structure,
More than 80% perlite,
Containing more than 5% residual austenite,
An average lamellar spacing of the pearlite is 0.5 μm or less,
The effective crystal grain size of the ferrite surrounded by the large-angle grain boundary with an orientation difference of 15 ° or more is 20 μm or less, and
A high-strength, high-ductility steel sheet characterized by having 5 or less carbides having an equivalent circle diameter of 0.1 μm or more per 400 μm 2 .
Ｃｕ、Ｎｉ、ＣｒおよびＭｏの１種または２種以上を合計で０．５％以下含むものである請求項１に記載の高強度高延性鋼板。 Ingredient composition is mass%, and
The high-strength and high-ductility steel sheet according to claim 1, comprising one or more of Cu, Ni, Cr and Mo in a total of 0.5% or less.
Ｖ、ＴｉおよびＮｂの１種または２種以上を合計で０．２％以下含むものである請求項１または２に記載の高強度高延性鋼板。 Ingredient composition is mass%, and
The high-strength and high-ductility steel sheet according to claim 1 or 2, comprising one or more of V, Ti, and Nb in a total of 0.2% or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2014236929A JP6189819B2 (en) | 2014-11-21 | 2014-11-21 | High strength high ductility steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2014236929A JP6189819B2 (en) | 2014-11-21 | 2014-11-21 | High strength high ductility steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2016098414A JP2016098414A (en) | 2016-05-30 |
| JP6189819B2 true JP6189819B2 (en) | 2017-08-30 |
Family
ID=56076291
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2014236929A Expired - Fee Related JP6189819B2 (en) | 2014-11-21 | 2014-11-21 | High strength high ductility steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP6189819B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101999012B1 (en) | 2017-12-22 | 2019-07-10 | 주식회사 포스코 | Hot rolled high carbon steel sheet and method for manufacturing thereof |
| JP7288177B2 (en) * | 2019-02-20 | 2023-06-07 | 日本製鉄株式会社 | Steel plate and steel plate manufacturing method |
| WO2020179737A1 (en) | 2019-03-06 | 2020-09-10 | 日本製鉄株式会社 | Hot-rolled steel sheet and production method therefor |
| EP4116446A1 (en) | 2020-03-02 | 2023-01-11 | Nippon Steel Corporation | Hot rolled steel sheet |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61217529A (en) * | 1985-03-22 | 1986-09-27 | Nippon Steel Corp | Manufacture of high strength steel sheet superior in ductility |
| JPH01116031A (en) * | 1987-10-29 | 1989-05-09 | Nippon Steel Corp | Manufacture of hot rolled high si-high carbon steel sheet having superior toughness |
| JP4375615B2 (en) * | 2004-06-15 | 2009-12-02 | 日新製鋼株式会社 | Steel plate for door parts |
| KR101445868B1 (en) * | 2007-06-05 | 2014-10-01 | 주식회사 포스코 | High carbon steel sheet superior in fatiugue lifeand manufacturing method thereof |
-
2014
- 2014-11-21 JP JP2014236929A patent/JP6189819B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2016098414A (en) | 2016-05-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP6762868B2 (en) | High-strength steel sheet and its manufacturing method | |
| CN109563586B (en) | Steel sheet and plated steel sheet | |
| JP5162382B2 (en) | Low yield ratio high toughness steel plate | |
| JP4575893B2 (en) | High strength steel plate with excellent balance of strength and ductility | |
| KR102284770B1 (en) | Steel sheet hot-dip-coated with zn-al-mg-based system having excellent workability and method for manufacturing same | |
| JP6875916B2 (en) | High-strength steel plate and its manufacturing method | |
| WO2017179372A1 (en) | High strength steel sheet and manufacturing method therefor | |
| WO2015151827A1 (en) | High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability | |
| JP6682785B2 (en) | Steel plate having excellent sour resistance and method of manufacturing the same | |
| WO2018043456A1 (en) | High strength cold-rolled steel sheet and method for manufacturing same | |
| WO2012036309A1 (en) | High-strength hot-rolled steel sheet having excellent bending workability and method for producing same | |
| JP6223905B2 (en) | High strength galvannealed steel sheet with excellent yield strength and workability | |
| JPH11323494A (en) | High strength hot rolled steel plate excellent in formability | |
| US11098392B2 (en) | Hot rolled steel sheet for cold rolled steel sheet, hot rolled steel sheet for galvanized steel sheet, and method for producing the same | |
| WO2015151826A1 (en) | High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability | |
| JP5888181B2 (en) | Hot rolled steel sheet | |
| JP2014037595A (en) | Method for producing hot-rolled steel sheet | |
| JP2005213595A (en) | Method for manufacturing super-fine grain hot-rolled steel plate | |
| JP5533146B2 (en) | Cold rolled steel sheet and method for producing the same | |
| JP2005330584A (en) | High-strength cold rolled steel sheet having excellent formability, and plated steel sheet | |
| JP6189819B2 (en) | High strength high ductility steel sheet | |
| JP2010013700A (en) | High strength hot dip galvanized steel sheet having excellent workability, and method for producing the same | |
| JPH07252592A (en) | Hot rolled high strength steel sheet excellent in formability, low temperature toughness and fatigue property | |
| JP2020059881A (en) | Steel material and method for manufacturing the same | |
| WO2017169329A1 (en) | High-strength steel sheet and method for manufacturing same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20160603 |
|
| RD04 | Notification of resignation of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7424 Effective date: 20160713 |
|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20160901 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20170706 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20170801 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20170803 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 6189819 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| LAPS | Cancellation because of no payment of annual fees |