JP6846522B2 - High-strength cold-rolled steel sheets with excellent yield strength, ductility, and hole expansion properties, hot-dip galvanized steel sheets, and methods for manufacturing these. - Google Patents

High-strength cold-rolled steel sheets with excellent yield strength, ductility, and hole expansion properties, hot-dip galvanized steel sheets, and methods for manufacturing these. Download PDF

Info

Publication number
JP6846522B2
JP6846522B2 JP2019531765A JP2019531765A JP6846522B2 JP 6846522 B2 JP6846522 B2 JP 6846522B2 JP 2019531765 A JP2019531765 A JP 2019531765A JP 2019531765 A JP2019531765 A JP 2019531765A JP 6846522 B2 JP6846522 B2 JP 6846522B2
Authority
JP
Japan
Prior art keywords
steel sheet
hot
cold
rolled steel
strength
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.)
Active
Application number
JP2019531765A
Other languages
Japanese (ja)
Other versions
JP2020509177A (en
Inventor
ジェ−ヒョン カク、
ジェ−ヒョン カク、
ハン−シク チョ、
ハン−シク チョ、
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Posco Holdings Inc
Original Assignee
Posco Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Publication of JP2020509177A publication Critical patent/JP2020509177A/en
Application granted granted Critical
Publication of JP6846522B2 publication Critical patent/JP6846522B2/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Description

本発明は、自動車車体に用いられる高強度鋼板に関し、より詳細には、高強度であるとともに、降伏強度及び成形性に優れ、プレス成形性に優れた高強度冷延鋼板、溶融亜鉛めっき鋼板、及びこれらの製造方法に関する。 The present invention relates to a high-strength steel sheet used for an automobile body, and more specifically, a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, which has high strength, excellent yield strength and formability, and excellent press formability. And these manufacturing methods.

建材、自動車、汽車などの輸送手段の構造部材に適用される鋼板の厚さを下げることで、軽量化を達成するために、従来の鋼材の強度を向上させようとする試みが多くなされている。しかし、このように強度を高める場合、降伏強度が比較的低くなり、延性及び穴拡げ性も低下するという欠点が発見された。 Many attempts have been made to improve the strength of conventional steel materials in order to achieve weight reduction by reducing the thickness of steel plates applied to structural members of transportation means such as building materials, automobiles, and trains. .. However, it has been discovered that when the strength is increased in this way, the yield strength is relatively low, and the ductility and hole expansion property are also reduced.

そこで、強度と延性の間の関係を向上するための研究が多く行われ、その結果、低温組織であるマルテンサイト、ベイナイトに加えて、残留オーステナイト相を活用する変態組織鋼が開発され、適用されているのが実情である。 Therefore, many studies have been conducted to improve the relationship between strength and ductility, and as a result, in addition to the low-temperature structures martensite and bainite, transformational steels that utilize the retained austenite phase have been developed and applied. The reality is that.

変態組織鋼は、いわゆる、ＤＰ（Ｄｕａｌ Ｐｈａｓｅ）鋼、ＴＲＩＰ（Ｔｒａｎｓｆｏｒｍａｔｉｏｎ Ｉｎｄｕｃｅｄ Ｐｌａｓｔｉｃｉｔｙ）鋼、ＣＰ（Ｃｏｍｐｌｅｘ Ｐｈａｓｅ）鋼などに区別され、これらそれぞれの鋼は、母相と第２相の種類及び分率に応じて、機械的性質、すなわち、引張強度及び伸びのレベルが異なり、特に残留オーステナイトを含有するＴＲＩＰ鋼の場合には、引張強度と伸びのバランス（ＴＳ×Ｅｌ）が最も高い値を示す。 Transformation structure steels are classified into so-called DP (Dual Phase) steels, TRIP (Transformation Induced Plasticity) steels, CP (Complex Phase) steels, etc., and each of these steels is classified into a matrix phase and a second phase type and fraction. The mechanical properties, that is, the levels of tensile strength and elongation, differ depending on the above, and in the case of TRIP steel containing retained austenite, the balance between tensile strength and elongation (TS × El) shows the highest value.

上記のような変態組織鋼のうち、ＣＰ鋼は、他の鋼に比べて伸びが低く、ロール成形などの単純加工に限って用いられ、高延性のＤＰ鋼及びＴＲＩＰ鋼は冷間プレス成形などに適用される。 Among the above-mentioned transformational structure steels, CP steel has lower elongation than other steels and is used only for simple machining such as roll forming, and high ductility DP steel and TRIP steel are cold press formed and the like. Applies to.

そこで、最近では、上記変態組織鋼であるＤＰ鋼及びＴＲＩＰ鋼よりも延性及び穴拡げ性能を高めることで、深絞り性、及びフランジ部のクラックを抑制しようとする技術が提案されている。一例として、特許文献２には、主組織として残留オーステナイト及びマルテンサイトを形成させる方法（Ｑｕｅｎｃｈｉｎｇ ａｎｄ Ｐａｒｔｉｔｉｏｎｉｎｇ Ｐｒｏｃｅｓｓ、Ｑ＆Ｐ）が開示されているが、これを活用したレポート（非特許文献１）によれば、炭素が０．２％レベルと低い場合には、降伏強度が４００ＭＰａ前後と低くなるという欠点があり、そして、最終製品で得られる伸びは、従来のＴＲＩＰ鋼のようなレベルだけが得られることが確認できる。Ｑ＆Ｐ方法での要旨は、マルテンサイト変態開始温度（Ｍｓ）と仕上げ温度（Ｍｆ）の間で焼入れしてから再加熱することにより、マルテンサイトとオーステナイトの界面で炭素拡散が起こり、オーステナイトを安定化させることで延性を確保するものである。しかし、焼入れ及びパーティショニング温度に応じて安定化しないオーステナイトが相当量存在し、フレッシュマルテンサイト（ＦＭ）が最終冷却段階で形成されるようになる。フレッシュマルテンサイトは、炭素含有量が高く、穴拡げ性を阻害する（特許文献３）。 Therefore, recently, a technique has been proposed in which deep drawing property and cracks in a flange portion are suppressed by improving ductility and hole expansion performance as compared with DP steel and TRIP steel which are the above-mentioned transformation structure steels. As an example, Patent Document 2 discloses a method of forming retained austenite and martensite as a main tissue (Quenching and Partitioning Process, Q & P), but according to a report utilizing this (Non-Patent Document 1). When the carbon content is as low as 0.2%, the yield strength is as low as around 400 MPa, and the elongation obtained in the final product is only the level of conventional TRIP steel. Can be confirmed. The gist of the Q & P method is that by quenching between the martensitic transformation start temperature (Ms) and the finishing temperature (Mf) and then reheating, carbon diffusion occurs at the interface between martensite and austenite, stabilizing austenite. The ductility is ensured by making it. However, there is a significant amount of austenite that is not stabilized with quenching and partitioning temperatures, resulting in the formation of fresh martensite (FM) during the final cooling stage. Fresh martensite has a high carbon content and inhibits hole expansion (Patent Document 3).

他の方法としては、マルテンサイト組織を再び熱処理し、二相域において熱処理することにより延性及び穴拡げ性を確保する方法が挙げられるが、これは熱処理を２回行うため経済的ではない（特許文献４）。 Another method is to heat-treat the martensite structure again and heat-treat it in the two-phase region to ensure ductility and hole expansion, but this is not economical because the heat treatment is performed twice (patented). Document 4).

最後に、一般の焼鈍方法で熱処理し、且つベイナイト形成区間まで急冷してから長時間恒温保持することでベイナイト組織を得る方法が開発されたが、恒温保持時間が非常に長く、十分に変態しないベイナイトは、最終冷却時にマルテンサイトを形成するため、穴拡げ性に優れない。 Finally, a method was developed in which a bainite structure was obtained by heat-treating with a general annealing method, quenching to the bainite forming section, and then holding the bainite structure at a constant temperature for a long time. Bainite does not have excellent hole-expandability because it forms martensite during final cooling.

韓国公開特許第１９９４−０００２３７０号公報Korean Publication No. 1994-0002370 米国公開特許第２００６−００１１２７４号公報US Publication No. 2006-0011274 特開平１４−１７７２７８号公報Japanese Unexamined Patent Publication No. 14-177278 特開平１３−３００５０３号公報Japanese Unexamined Patent Publication No. 13-300503 特開平２６−０１８４３１号公報Japanese Unexamined Patent Publication No. 26-018431

ＩＳＩＪ Ｉｎｔｅｒｎａｔｉｏｎａｌ，Ｖｏｌ．５１，２０１１，ｐ．１３７−１４４ISIJ International, Vol. 51, 2011, p. 137-144

本発明は、上述した従来技術の限界を解決するために提案されたものであって、従来のＴＷＩＰ鋼に比べて少ない合金コストを実現し、従来のＴＢＦ（Ｔｒｉｐ ａｉｄｅｄ Ｂａｉｎｉｔｉｃ Ｆｅｒｒｉｔｅ）、Ｑ＆Ｐ（Ｑｕｅｎｃｈｉｎｇ ａｎｄ Ｐａｒｔｉｔｉｏｎｉｎｇ）熱処理工程を適用した場合に比べてさらに優れた延性及び穴拡げ性を有するベイナイト主相の冷延鋼板、これを用いて製造した溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板、及びこれらの製造方法を提供することをその目的とする。 The present invention has been proposed to solve the limitations of the above-mentioned prior art, realizes a lower alloy cost than the conventional TWIP steel, and realizes a conventional TBF (Tripped Bainitic Ferrite) and Q & P (Quenching). And Partitioning) Cold-rolled steel sheet of bainite main phase, which has better ductility and hole expansion property than when heat treatment process is applied, hot-dip zinc-plated steel sheet, alloyed hot-dip zinc-plated steel sheet, and these. The purpose is to provide a method for producing the above.

また、本発明の課題は、上述した内容に限定されない。本発明の課題は、本明細書の内容全般から理解されることができ、本発明が属する技術分野における通常の知識を有する者であれば、本発明の追加的な課題を明確に理解するものである。 Moreover, the subject of the present invention is not limited to the above-mentioned contents. The subject of the present invention can be understood from the contents of the present specification in general, and a person having ordinary knowledge in the technical field to which the present invention belongs can clearly understand the additional subject of the present invention. Is.

上記目的を達成するための本発明は、重量％で、炭素（Ｃ）：０．０６〜０．２％、マンガン（Ｍｎ）：１．５〜３．０％、ケイ素（Ｓｉ）：０．３〜２．５％、アルミニウム（Ａｌ）：０．０１〜０．２％、ニッケル（Ｎｉ）：０．０１〜３．０％、モリブデン（Ｍｏ）：０．２％以下、チタン（Ｔｉ）：０．０１〜０．０５、アンチモン（Ｓｂ）：０．０２〜０．０５、ホウ素（Ｂ）：０．０００５〜０．００３、窒素（Ｎ）：０．０１％以下（０％は除く）、残部Ｆｅ及び不可避不純物を含み、その微細組織が、面積分率で、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下を含む降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板に関する。 In the present invention for achieving the above object, carbon (C): 0.06 to 0.2%, manganese (Mn): 1.5 to 3.0%, silicon (Si): 0. 3 to 2.5%, aluminum (Al): 0.01 to 0.2%, nickel (Ni): 0.01 to 3.0%, molybdenum (Mo): 0.2% or less, titanium (Ti) : 0.01 to 0.05, antimony (Sb): 0.02 to 0.05, boron (B): 0.0005 to 0.003, nitrogen (N): 0.01% or less (excluding 0%) ), The balance Fe and unavoidable impurities, and its microstructure is bainite 50% or more, tempered martensite (TM) 10% or more, fresh martensite (FM) 10% or less, retained austenite 20% or less in area fraction. , And a high-strength cold-rolled steel sheet containing 5% or less of ferrite and having excellent yield strength, ductility, and hole expansion property.

上記ＴＭ／ＦＭの比は２を超えることが好ましい。 The TM / FM ratio preferably exceeds 2.

また、本発明は、上記冷延鋼板の表面に溶融亜鉛めっき処理された溶融亜鉛めっき鋼板、及び合金化溶融亜鉛めっき処理された合金化溶融亜鉛めっき鋼板に関する。 The present invention also relates to a hot-dip galvanized steel sheet in which the surface of the cold-rolled steel sheet is hot-dip galvanized, and an alloyed hot-dip galvanized steel sheet in which an alloyed hot-dip galvanized steel sheet is treated.

また、本発明は、重量％で、炭素（Ｃ）：０．０６〜０．２％、マンガン（Ｍｎ）：１．５〜３．０％、ケイ素（Ｓｉ）：０．３〜２．５％、アルミニウム（Ａｌ）：０．０１〜０．２％、ニッケル（Ｎｉ）：０．０１〜３．０％、モリブデン（Ｍｏ）：０．２％以下、チタン（Ｔｉ）：０．０１〜０．０５、アンチモン（Ｓｂ）：０．０２〜０．０５、ホウ素（Ｂ）：０．０００５〜０．００３、窒素（Ｎ）：０．０１％以下（０％は除く）、残部Ｆｅ及び不可避不純物を含む鋼スラブを再加熱し、次いで、熱間圧延した後、巻取る工程と、上記巻取られた熱延鋼板を冷間圧延した後、Ｑ＆Ｐ連続焼鈍する工程と、を含み、上記Ｑ＆Ｐ連続焼鈍する工程は、上記製造された冷延鋼板をＡｃ３以上の温度で３０秒以上均熱し、次いで、５〜２０℃／秒の冷却速度で下記関係式１で定義される焼入れ温度（ＱＴ）±１０℃まで冷却する工程と、上記冷却された鋼板を下記関係式２で定義されるベイナイト温度（ＰＴ）±１０℃で再加熱し、次いで、ＰＴ−１００℃以上でありＰＴ以下の温度範囲内で１００秒以上保持した後、冷却する工程と、を含むことを特徴とする、降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板の製造方法に関する。
［関係式１］
ＱＴ＝４９３．４９７＋３６．２８７４×Ａｌ−３９４．０×Ｃ−４５．０×Ｍｎ−１１．４３３２×Ｍｏ−２０．８７７２×Ｎｉ−１３．０４３８×Ｓｉ−１２．８×Ｃｒ
［関係式２］
ＰＴ＝５９９．０８８＋１１．５２１４×Ａｌ−２２５．２×Ｃ−３５．０×Ｍｎ−１９．９４７４×Ｎｉ−２４．９３８５×Ｓｉ−５６．７１８×Ｍｏ−２２．１×Ｃｒ
Further, in the present invention, in% by weight, carbon (C): 0.06 to 0.2%, manganese (Mn): 1.5 to 3.0%, silicon (Si): 0.3 to 2.5. %, Aluminum (Al): 0.01 to 0.2%, Nickel (Ni): 0.01 to 3.0%, Molybdenum (Mo): 0.2% or less, Titanium (Ti): 0.01 to 0.05, Antimon (Sb): 0.02 to 0.05, Boron (B): 0.0005 to 0.003, Nitrogen (N): 0.01% or less (excluding 0%), balance Fe and The steel slab containing unavoidable impurities is reheated, then hot-rolled and then wound, and the wound hot-rolled steel sheet is cold-rolled and then Q & P continuously annealed. In the Q & P continuous annealing step, the cold-rolled steel sheet produced above is homogenized at a temperature of Ac3 or higher for 30 seconds or longer, and then the quenching temperature (QT) defined by the following relational expression 1 at a cooling rate of 5 to 20 ° C./sec. ) The step of cooling to ± 10 ° C. and the above-cooled steel sheet are reheated at the annealed temperature (PT) ± 10 ° C. defined by the following relational expression 2, and then the temperature is PT-100 ° C. or higher and PT or lower. The present invention relates to a method for producing a high-strength cold-rolled steel sheet having excellent yield strength, ductility, and hole expansion property, which comprises a step of holding the steel sheet within the range for 100 seconds or more and then cooling the steel sheet.
[Relationship formula 1]
QT = 493.497 + 36.2874 x Al-394.0 x C-45.0 x Mn-11.4332 x Mo-20.8772 x Ni-13.038 x Si-12.8 x Cr
[Relational expression 2]
PT = 599.088 + 11.5214 × Al-225.2 × C-35.0 × Mn-19.9474 × Ni-24.9385 × Si-56.718 × Mo-22.1 × Cr

上記Ｑ＆Ｐ連続焼鈍が完了した鋼板は、その微細組織が、面積分率で、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下を含むことができる。 The steel sheet for which the above Q & P continuous annealing has been completed has a microstructure of bainite 50% or more, tempered martensite (TM) 10% or more, fresh martensite (FM) 10% or less, and retained austenite 20% or less in terms of area fraction. , And 5% or less of ferrite can be contained.

上記ＴＭ／ＦＭの比が２を超えることが好ましい。 The TM / FM ratio preferably exceeds 2.

また、本発明は、上記Ｑ＆Ｐ連続焼鈍された冷延鋼板の表面に溶融亜鉛めっき処理する工程をさらに含む、溶融亜鉛めっき鋼板の製造方法、及び上記Ｑ＆Ｐ連続焼鈍された冷延鋼板の表面に合金化溶融亜鉛めっき処理する工程をさらに含む、合金化溶融亜鉛めっき鋼板の製造方法に関する。 The present invention further comprises a method for producing a hot-dip galvanized steel sheet, which further comprises a step of hot-dip galvanizing the surface of the Q & P continuously annealed cold-rolled steel sheet, and an alloy on the surface of the Q & P continuously annealed cold-rolled steel sheet. The present invention relates to a method for producing an alloyed hot-dip galvanized steel sheet, which further comprises a step of performing a hot-dip galvanized steel sheet.

上述した構成の本発明によると、従来のＤＰ鋼やＴＲＩＰ鋼のような高延性変態組織鋼、及び従来のＱ＆Ｐ（Ｑｕｅｎｃｈｉｎｇ＆Ｐａｒｔｉｔｉｏｎｉｎｇ）熱処理を経たＱ＆Ｐ鋼に比べて、正確なＴＭ量及びベイナイトを確保することができるため、降伏強度及び延性ならびに穴拡げ性に優れた引張強度９８０ＭＰａ以上の高強度冷延鋼板、溶融亜鉛めっき鋼板、及び合金化溶融亜鉛めっき鋼板を効果的に提供することができるようになる。 According to the present invention having the above-described configuration, accurate TM amount and bainite are ensured as compared with conventional high ductility transformational steels such as DP steel and TRIP steel, and conventional Q & P steels that have undergone Q & P (Quenching & Partitioning) heat treatment. Therefore, it is possible to effectively provide a high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more, a hot-dip zinc-plated steel sheet, and an alloyed hot-dip zinc-plated steel sheet, which are excellent in yield strength, ductility, and hole expansion property. Become.

これにより、本発明の冷延鋼板などは、建築部材、自動車鋼板などの産業分野において、活用可能性が高いという利点がある。 As a result, the cold-rolled steel sheet of the present invention has an advantage that it is highly likely to be used in industrial fields such as building materials and automobile steel sheets.

図１は、本発明による焼鈍工程の一例を示すものである（図１に示された熱処理線のうち、点線は溶融合金化めっき時の熱履歴を示すものである）。FIG. 1 shows an example of the annealing process according to the present invention (of the heat treatment lines shown in FIG. 1, the dotted line shows the thermal history during hot-dip alloying plating). 図２は、ＴＢＦ法及び本発明による方法の低温変態挙動を示すものである。FIG. 2 shows the low temperature transformation behavior of the TBF method and the method according to the present invention. 図３は、本発明により製造された発明例（Ｆ）鋼の微細組織を観察した写真である。FIG. 3 is a photograph of observing the microstructure of the steel of invention example (F) produced by the present invention. 図４は、本発明により製造された冷延鋼板の焼戻しマルテンサイト中の炭化物を観察した結果である。FIG. 4 shows the results of observing the carbides in the tempered martensite of the cold-rolled steel sheet produced according to the present invention. 図５は、比較例（Ｅ）鋼の微細組織を観察した写真である。FIG. 5 is a photograph of the microstructure of the steel of Comparative Example (E) observed.

本発明者らは、従来のＱ＆Ｐ（Ｑｕｅｎｃｈｉｎｇ＆Ｐａｒｔｉｔｉｏｎｉｎｇ）熱処理により製造される高強度鋼の低い延性を向上させる方法について深く研究した結果、Ｑ＆Ｐ熱処理時に、従来技術よりもさらに細かい特定の温度区間でベイナイト変態が促進され、ＦＭが著しく減少する熱処理条件を見つけた。焼入れによるマルテンサイト形成量及びベイナイト変態促進区間によってＱＴ及びＰＴを制御することにより、最終的なＱ＆Ｐ熱処理後の組織微細化、及び最終製品の物性向上が可能であることを確認し、本発明を提示した。 As a result of deep research on a method for improving the low ductility of high-strength steel produced by conventional Q & P (Quenching & Partitioning) heat treatment, the present inventors have conducted bainite transformation in a specific temperature section finer than the conventional technique during Q & P heat treatment. We found heat treatment conditions that promoted and significantly reduced FM. It was confirmed that by controlling QT and PT by the amount of martensite formed by quenching and the bainite transformation promoting section, it is possible to refine the structure after the final Q & P heat treatment and improve the physical properties of the final product. presentation.

以下、本発明について詳細に説明する。 Hereinafter, the present invention will be described in detail.

まず、本発明で提供される冷延鋼板などの合金成分組成及びその含有量を制限する理由について詳細に説明する。このとき、各成分の含有量は、特に記載しない限り、重量％を意味する。 First, the alloy component composition of the cold-rolled steel sheet provided in the present invention and the reason for limiting the content thereof will be described in detail. At this time, the content of each component means% by weight unless otherwise specified.

Ｃ：０．０６〜０．２％、
炭素（Ｃ）は、鋼を強化させるのに有効な元素であり、本発明では、残留オーステナイトの安定化及び強度確保のために添加される重要元素である。上述した効果を得るために、０．０６％以上添加することが好ましいが、その含有量が０．０６％未満である場合には、オーステナイト単相温度が非常に高くなって高温焼鈍が避けられず、強度及び延性の確保が難しくなりうる。また、０．２％を超えると、Ｍｓが低下して焼入れ温度が低くなり、精巧な熱処理が難しくなる。また、溶接性も大きく低下するという問題がある。したがって、本発明において、Ｃ含有量は、０．０６〜０．２％に制限することが好ましい。 C: 0.06 to 0.2%,
Carbon (C) is an element effective for strengthening steel, and in the present invention, it is an important element added for stabilizing retained austenite and ensuring strength. In order to obtain the above-mentioned effects, it is preferable to add 0.06% or more, but when the content is less than 0.06%, the austenite single-phase temperature becomes very high and high-temperature annealing can be avoided. However, it may be difficult to secure strength and ductility. On the other hand, if it exceeds 0.2%, Ms is lowered and the quenching temperature is lowered, which makes elaborate heat treatment difficult. In addition, there is a problem that the weldability is greatly reduced. Therefore, in the present invention, the C content is preferably limited to 0.06 to 0.2%.

Ｍｎ：１．５〜３．０％
マンガン（Ｍｎ）は、フェライトの変態を制御するとともに、残留オーステナイトの形成及び安定化に有効な元素である。かかるＭｎ含有量が１．５％未満である場合には、フェライト変態が大量に発生し、目標とする強度の確保が難しくなるという問題がある。これに対し、３．０％を超えると、本発明の二次焼鈍熱処理段階における相変態が遅すぎるようになってマルテンサイトが大量に形成されるため、意図する延性の確保が難しくなるという問題がある。したがって、本発明において、Ｍｎ含有量は、１．５〜３．０％に制限することが好ましい。 Mn: 1.5-3.0%
Manganese (Mn) is an element that controls the transformation of ferrite and is effective in forming and stabilizing retained austenite. When the Mn content is less than 1.5%, there is a problem that a large amount of ferrite transformation occurs and it becomes difficult to secure the target strength. On the other hand, if it exceeds 3.0%, the phase transformation in the secondary annealing heat treatment stage of the present invention becomes too slow and a large amount of martensite is formed, which makes it difficult to secure the intended ductility. There is. Therefore, in the present invention, the Mn content is preferably limited to 1.5 to 3.0%.

Ｓｉ：０．３〜２．５％
ケイ素（Ｓｉ）は、フェライト内において炭化物の析出を抑制するとともに、フェライト内の炭素がオーステナイトに拡散することを助長し、結果として、ベイナイトの形成及び残留オーステナイトの安定化に寄与する元素である。上述した効果を得るために、０．３％以上添加することが好ましいが、その含有量が２．５％を超えると、熱間及び冷間圧延性が非常に悪くなり、鋼の表面に酸化物を形成してめっき性を阻害するという問題がある。したがって、本発明において、Ｓｉ含有量は、０．３〜２．５％に制限することが好ましい。 Si: 0.3-2.5%
Silicon (Si) is an element that suppresses the precipitation of carbides in the ferrite and promotes the diffusion of carbon in the ferrite into austenite, and as a result, contributes to the formation of bainite and the stabilization of retained austenite. In order to obtain the above-mentioned effects, it is preferable to add 0.3% or more, but if the content exceeds 2.5%, the hot and cold rollability becomes very poor, and the steel surface is oxidized. There is a problem of forming an object and impairing the plating property. Therefore, in the present invention, the Si content is preferably limited to 0.3 to 2.5%.

Ａｌ：０．０１〜０．２％
アルミニウム（Ａｌ）は、鋼中の酸素と結合して脱酸作用をする元素であり、このため、その含有量を０．０１％以上に保持することが好ましい。また、Ａｌは、上記Ｓｉと同様に、フェライト内において炭化物の生成抑制を介して残留オーステナイトの安定化に寄与し、ベイナイト形成温度を高める。しかし、かかるＡｌ含有量が０．２％を超えると、Ａ３温度が増加するようになって、高温焼鈍が避けられないだけでなく、鋳造時のモールドプラスとの反応を介して健全なスラブの製造が難しくなり、さらには、表面酸化物を形成してめっき性を阻害するという問題がある。したがって、本発明において、Ａｌ含有量は、０．０１〜０．２％に制限することが好ましい。 Al: 0.01-0.2%
Aluminum (Al) is an element that combines with oxygen in steel to perform a deoxidizing action, and for this reason, it is preferable to maintain its content at 0.01% or more. Further, Al contributes to the stabilization of retained austenite through suppression of the formation of carbides in the ferrite, and raises the bainite formation temperature, similarly to the above-mentioned Si. However, when the Al content exceeds 0.2%, the A3 temperature increases, and not only high temperature annealing is unavoidable, but also a healthy slab through the reaction with Mold Plus during casting. There is a problem that the production becomes difficult, and further, a surface oxide is formed to hinder the plating property. Therefore, in the present invention, the Al content is preferably limited to 0.01 to 0.2%.

ニッケル（Ｎｉ）：０．０１〜３．０％
ニッケル（Ｎｉ）は、固溶強化により強度を確保するとともに、オーステナイトを安定化する元素であって、０．０１％以上を保持することが好ましい。しかし、ベイナイト変態を遅延させる効果が大きく、添加しすぎると、ベイナイト変態が完全に行われずＦＭが形成されるため、上限を３％に制限することが好ましい。 Nickel (Ni): 0.01-3.0%
Nickel (Ni) is an element that secures strength by strengthening the solid solution and stabilizes austenite, and preferably retains 0.01% or more. However, the effect of delaying the bainite transformation is large, and if it is added too much, the bainite transformation is not completely performed and FM is formed. Therefore, it is preferable to limit the upper limit to 3%.

モリブデン（Ｍｏ）：０．２％以下
モリブデン（Ｍｏ）も、固溶強化により強度を強化し、ＴｉＭｏ炭化物を形成してベイナイト組織を微細化するために添加するが、合金鉄の価格が高く、コストが上昇するという問題があるため、上限を０．２％に制限することが好ましい。 Molybdenum (Mo): 0.2% or less Molybdenum (Mo) is also added to enhance the strength by solid solution strengthening to form TiMo carbides and refine the bainite structure, but the price of ferroalloy is high. Due to the problem of increased cost, it is preferable to limit the upper limit to 0.2%.

チタン（Ｔｉ）：０．０１〜０．０５
チタン（Ｔｉ）は、ＴｉＮを優先的に形成するため、固溶ホウ素の添加による焼入性を向上させるためには必ず必要とする。本発明では、ＢＮよりも優先してＴｉＮが形成されるように、その下限を０．０１％とし、多くなりすぎると、ＴｉＮが晶出して連続鋳造におけるノズル詰まりを引き起こす可能性があるため、その上限を０．０５％に制限することが好ましい。 Titanium (Ti): 0.01 to 0.05
Since titanium (Ti) preferentially forms TiN, it is absolutely necessary to improve the hardenability by adding solid solution boron. In the present invention, the lower limit is set to 0.01% so that TiN is formed in preference to BN, and if it is too large, TiN may crystallize and cause nozzle clogging in continuous casting. It is preferable to limit the upper limit to 0.05%.

アンチモン（Ｓｂ）：０．０２〜０．０５
アンチモン（Ｓｂ）は、粒界偏析物質として粒界酸化物を形成し、粒界を通じた脱炭を抑制するとともに、Ｍｎ、Ｓｉなどの表面濃化による亜鉛めっき性の低下を抑制するための手段として０．０２％以上添加することが好ましい。しかし、多すぎると、粒界偏析が増加し、鋼の脆性を引き起こす可能性があるため、上限を０．０５％に制限する。 Antimony (Sb): 0.02-0.05
Antimon (Sb) is a means for forming a grain boundary oxide as a grain boundary segregating substance, suppressing decarburization through the grain boundaries, and suppressing a decrease in galvanizing property due to surface concentration of Mn, Si, etc. It is preferable to add 0.02% or more. However, if it is too large, grain boundary segregation increases and may cause brittleness of the steel, so the upper limit is limited to 0.05%.

ホウ素（Ｂ）：０．０００５〜０．００３
ホウ素（Ｂ）は、焼入れによる強度確保が簡単な安価の合金元素であるため、合金総量を減らすという効果を奏し、溶接性や高温脆性の抑制に有利な元素であるため、下限を０．００５％にし得る。しかし、多くなりすぎると、ＴｉＮよりもＢＮ形成温度が高くなり、鋼の高温脆性を引き起こす可能性があるため、上限を０．００３％に制限することが好ましい。 Boron (B): 0.0005 to 0.003
Boron (B) is an inexpensive alloy element whose strength can be easily secured by quenching, so it has the effect of reducing the total amount of alloy, and is an element that is advantageous in suppressing weldability and high-temperature brittleness. Therefore, the lower limit is 0.005. Can be%. However, if the amount is too large, the BN formation temperature becomes higher than that of TiN, which may cause high temperature brittleness of the steel. Therefore, it is preferable to limit the upper limit to 0.003%.

窒素（Ｎ）：０．０１％以下
窒素（Ｎ）は、ＢＮ、ＴｉＮの形成により、合金元素の合金効率を低減させるため、通常制御できる範囲である０．０１％以下に制限することが好ましい。 Nitrogen (N): 0.01% or less Nitrogen (N) is preferably limited to 0.01% or less, which is a normally controllable range, in order to reduce the alloy efficiency of alloying elements by forming BN and TiN. ..

本発明の他の成分は鉄（Ｆｅ）である。但し、通常の製造過程では、原料や周囲の環境から意図しない不純物が必然的に混入される可能性があるため、これを排除することはできない。これらの不純物は、通常の製造過程における技術者であれば誰でも分かるものであるため、そのすべての内容を具体的に言及することはしない。 Another component of the present invention is iron (Fe). However, in the normal manufacturing process, unintended impurities may inevitably be mixed in from the raw materials and the surrounding environment, so this cannot be excluded. Since these impurities can be understood by any engineer in a normal manufacturing process, all the contents thereof are not specifically mentioned.

一方、上述した鋼組成成分を満たす本発明の冷延鋼板は、面積分率で、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下を含む微細組織を有する。ここで、上記ベイナイトは、マルテンサイトの次に強度が高く、フェライトとマルテンサイトの中間特性を有する。さらに、微細な残留オーステナイトをベイナイト相の内部に分布させると、鋼の強度、延性バランスが非常に高くなる。 On the other hand, the cold-rolled steel sheet of the present invention satisfying the above-mentioned steel composition components has bainite of 50% or more, tempered martensite (TM) of 10% or more, fresh martensite (FM) of 10% or less, and retained austenite 20. It has a microstructure containing% or less and 5% or less ferrite. Here, the bainite has the second highest strength after martensite and has intermediate characteristics between ferrite and martensite. Furthermore, if fine retained austenite is distributed inside the bainite phase, the strength and ductility balance of the steel will be very high.

上述した微細組織を満たす本発明の冷延鋼板によると、引張強度が９８０ＭＰａ以上であり、従来のＱ＆Ｐ熱処理により製造された鋼板に比べて優れた降伏強度を有し、プレス成形性、延性、穴拡げ性に優れた高成形ギガ級高強度鋼板を提供することができる。 According to the cold-rolled steel sheet of the present invention that satisfies the above-mentioned fine structure, the tensile strength is 980 MPa or more, the yield strength is superior to that of the steel sheet manufactured by the conventional Q & P heat treatment, and the press formability, ductility, and holes It is possible to provide a highly formed giga-class high-strength steel sheet having excellent spreadability.

また、本発明によると、上記冷延鋼板の表面に溶融亜鉛めっき処理した溶融亜鉛めっき鋼板、及びその溶融亜鉛めっき鋼板を合金化熱処理した合金化溶融亜鉛めっき鋼板を提供することもできる。 Further, according to the present invention, it is also possible to provide a hot-dip galvanized steel sheet in which the surface of the cold-rolled steel sheet is hot-dip galvanized, and an alloyed hot-dip galvanized steel sheet in which the hot-dip galvanized steel sheet is alloyed and heat-treated.

次に、本発明の冷延鋼板などの製造方法について詳細に説明する。 Next, the manufacturing method of the cold-rolled steel sheet of the present invention will be described in detail.

本発明による冷延鋼板は、上述した鋼成分組成を満たす鋼スラブを再加熱−熱間圧延−巻取り−冷間圧延−焼鈍工程を経ることにより製造することができる。これについての詳細な説明は下記のとおりである。 The cold-rolled steel sheet according to the present invention can be produced by undergoing a reheating-hot rolling-winding-cold rolling-annealing process of a steel slab satisfying the above-mentioned steel composition. A detailed explanation of this is as follows.

（鋼スラブ再加熱工程）
本発明では、熱間圧延を行う前に、鋼スラブを再加熱して均質化処理する工程を経ることが好ましい。これは、１０００〜１３００℃の温度範囲で行うことがより好ましい。
上記再加熱時の温度が１０００℃未満である場合には、圧延荷重が急激に増加するという問題が発生する。これに対し、その温度が１３００℃を超えると、エネルギーコストが増加するだけでなく、表面スケールの量が多くなりすぎるという問題が発生する。したがって、本発明において、再加熱工程は、１０００〜１３００℃で行うことが好ましい。 (Steel slab reheating process)
In the present invention, it is preferable to go through a step of reheating the steel slab to homogenize it before hot rolling. This is more preferably done in the temperature range of 1000-1300 ° C.
If the temperature at the time of reheating is less than 1000 ° C., there arises a problem that the rolling load increases sharply. On the other hand, if the temperature exceeds 1300 ° C., not only the energy cost increases, but also the amount of surface scale becomes too large. Therefore, in the present invention, the reheating step is preferably performed at 1000 to 1300 ° C.

（熱間圧延工程）
上記再加熱された鋼スラブを熱間圧延して熱延鋼板を製造する。このとき、熱間仕上げ圧延は、８００〜９５０℃で行うことが好ましい。
上記熱間仕上げ圧延時の圧延温度が８００℃未満である場合には、圧延荷重が多く増加し、圧延が難しくなるという問題がある。これに対し、熱間仕上げ圧延温度が９５０℃を超えると、圧延ロールの熱疲労が多く増え、寿命短縮の原因となる。したがって、本発明では、熱間圧延時の熱間仕上げ圧延温度を８００〜９５０℃に制限することが好ましい。 (Hot rolling process)
The reheated steel slab is hot-rolled to produce a hot-rolled steel sheet. At this time, the hot finish rolling is preferably performed at 800 to 950 ° C.
When the rolling temperature during the hot finish rolling is less than 800 ° C., there is a problem that the rolling load increases a lot and rolling becomes difficult. On the other hand, when the hot finish rolling temperature exceeds 950 ° C., the thermal fatigue of the rolling roll increases a lot, which causes a shortening of the life. Therefore, in the present invention, it is preferable to limit the hot finish rolling temperature during hot rolling to 800 to 950 ° C.

（巻取り工程）
次に、上記によって製造された熱延鋼板を巻取る。このとき、巻取り温度は７５０℃以下であることが好ましい。
巻取り時の巻取り温度が高すぎると、熱延鋼板の表面にスケールが大量に発生して表面欠陥を誘発し、めっき性を劣化させる原因となる。したがって、巻取り工程は、７５０℃以下で行うことが好ましい。このとき、巻取り温度の下限は特に限定しないが、マルテンサイトの形成による熱延板の強度が高くなりすぎることに伴う、後続の冷間圧延工程の難しさを考慮して、Ｍｓ（マルテンサイト変態開始温度）〜７５０℃で行うことがより好ましい。 (Winding process)
Next, the hot-rolled steel sheet produced as described above is wound up. At this time, the winding temperature is preferably 750 ° C. or lower.
If the winding temperature at the time of winding is too high, a large amount of scale is generated on the surface of the hot-rolled steel sheet, which induces surface defects and causes deterioration of plating property. Therefore, the winding step is preferably performed at 750 ° C. or lower. At this time, the lower limit of the winding temperature is not particularly limited, but in consideration of the difficulty of the subsequent cold rolling process due to the strength of the hot-rolled plate becoming too high due to the formation of martensite, Ms (martensite) is taken into consideration. It is more preferable to carry out the transformation at (transformation start temperature) to 750 ° C.

（冷間圧延工程）
上記巻取られた熱延鋼板を酸洗処理して酸化層を除去した後、鋼板の形状及び厚さを合わせるために冷間圧延を行い、冷延鋼板を製造する。
一般に、冷間圧延は、顧客が要求する厚さを確保するために行う。このとき、圧下率の制限はないが、後続の焼鈍工程における再結晶時の粗大なフェライト結晶粒の生成を抑制するために、３０％以上の冷間圧下率で行うことが好ましい。 (Cold rolling process)
The wound hot-rolled steel sheet is pickled to remove the oxide layer, and then cold-rolled to match the shape and thickness of the steel sheet to produce a cold-rolled steel sheet.
Generally, cold rolling is performed to ensure the thickness required by the customer. At this time, there is no limitation on the reduction rate, but in order to suppress the formation of coarse ferrite crystal grains at the time of recrystallization in the subsequent annealing step, it is preferable to perform the reduction at a cold reduction rate of 30% or more.

（Ｑ＆Ｐ連続焼鈍工程）
本発明では、最終的な微細組織が、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％ 以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下を含む冷延鋼板を製造するために、後続の焼鈍工程の制御が重要である。特に、本発明では、焼鈍時の炭素、マンガンなどの元素の再分配（ｐａｒｔｉｔｉｏｎｉｎｇ）から目標とする微細組織を確保するために、一般の冷間圧延後のＱ＆Ｐ連続焼鈍工程を採用する。但し、後述のように、ＱＴ、ＰＴを合金元素に応じて制御することを特徴とする。
均熱及び急冷
まず、上記製造された冷延鋼板をＡｃ３以上の温度で３０秒以上均熱した後、５〜２０℃／秒の冷却速度で下記関係式１で定義される焼入れ温度（ＱＴ）±１０℃まで冷却することが好ましい（図１参照）。
これは、穴拡げ性に不利なフェライト組織を５％以内に得るためのものであり、本発明のフェライト未形成冷却速度は、５〜２０℃になるように設計した。冷却速度がこれより高くても問題はないが、冷却速度が遅いほどねじれがなく、板状が優れるため、さらに高める必要はない。
ＱＴは、２０〜５０％のマルテンサイトが形成される温度まで冷却する。Ｑ＆Ｐにおける焼入れ中に形成されるマルテンサイトは、ＰＴまで再加熱し、パーティショニング処理すると、焼戻しを起こし、強度がさらに低下するだけでなく、ベイナイトの形成を促進する役割をもたらす。図２に示すように、同一の温度でパーティショニング処理しても、ベイナイト域の温度まで急冷して恒温保持するＴＢＦは、６００秒経過してもベイナイト析出が完全に行われず、ＦＭが形成されるのに対し、十分なマルテンサイトを形成させると、短い時間でベイナイト変態が完全に行われてＦＭが形成されないことが分かる。このように、本発明において、ＦＭを最小限にする理由は、ベイナイト変態過程で残るオーステナイトに炭素、マンガンのような元素が濃化し、オーステナイトとして残らず、最終的な冷却中に変態するＦＭには、合金元素量が非常に高いマルテンサイトが残り、強度が非常に高く、穴拡げ中に界面分離を起こし、簡単に亀裂が生じて穴拡げ性を大幅に低下させるためである。
本発明では、このような特性を新たに発見し、これにより、ベイナイト主相を有する高成形性高強度鋼を新たに開発し、ベイナイトの形成を促進するとともに、ベイナイト面積率が最大となるＱＴを以下のように実験を介して求めた。
［関係式１］
ＱＴ＝４９３．４９７＋３６．２８７４×Ａｌ−３９４．０×Ｃ−４５．０×Ｍｎ−１１．４３３２×Ｍｏ−２０．８７７２×Ｎｉ−１３．０４３８×Ｓｉ−１２．８×Ｃｒ
パーティショニング熱処理
続いて、本発明では、上記冷却された鋼板を、下記関係式２で定義されるベイナイト温度（ＰＴ）±１０℃で再加熱し、次いで、ＰＴ−１００℃以上でありＰＴ以下の温度範囲内で１００秒以上保持した後、冷却する。
上述した焼入れ後に、ベイナイト温度（ＰＴ）で再加熱し、恒温保持するにあたり、ベイナイトが最も早く形成される温度を、実験を介して求めた。これよりも温度が高いと、ベイナイトの形成量が少なく、残留オーステナイトの安定化が不十分であり、ＦＭの形成が逆に増加するため、ＰＴは必ずＰＴ±１０℃まで加熱する必要がある。
［関係式２］
ＰＴ＝５９９．０８８＋１１．５２１４×Ａｌ−２２５．２×Ｃ−３５．０×Ｍｎ−１９．９４７４×Ｎｉ−２４．９３８５×Ｓｉ−５６．７１８×Ｍｏ−２２．１×Ｃｒ
従来技術とは異なり、本発明では、恒温保持を一定の温度に保持する必要がない。恒温保持は、ＰＴ−１００℃以上でありＰＴ以下の温度範囲内で、１００秒以上保持してから冷却すれば十分であるため、加熱保持装置がない恒温炉を有する設備への適用が簡単であるという利点を有する。
このようにＱ＆Ｐ熱処理すると、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下を含む鋼を製造することができ、強度差が大きいフェライト及びＦＭを最小限に抑えることにより、従来のＱ＆Ｐ熱処理により製造された鋼板に比べて、優れた降伏強度、延性、及び穴拡げ性に優れた高成形ギガ級高強度鋼板を製造することができる。
(Q & P continuous annealing process)
In the present invention, the final microstructure contains 50% or more bainite, 10% or more tempered martensite (TM), 10% or less fresh martensite (FM), 20% or less retained austenite, and 5% or less ferrite. In order to manufacture bainite, it is important to control the subsequent annealing process. In particular, in the present invention, a general Q & P continuous annealing step after cold rolling is adopted in order to secure a target microstructure from the redistributing (partitioning) of elements such as carbon and manganese during annealing. However, as will be described later, QT and PT are controlled according to the alloying elements.
Soaking and quenching First, after soaking the manufactured cold-rolled steel sheet at a temperature of Ac3 or higher for 30 seconds or longer, the quenching temperature (QT) defined by the following relational expression 1 at a cooling rate of 5 to 20 ° C./sec. It is preferable to cool to ± 10 ° C. (see FIG. 1).
This is for obtaining a ferrite structure which is disadvantageous for hole expansion within 5%, and the ferrite unformed cooling rate of the present invention is designed to be 5 to 20 ° C. There is no problem if the cooling rate is higher than this, but the slower the cooling rate, the less twisting and the better the plate shape, so there is no need to further increase it.
QT cools to a temperature at which 20-50% martensite is formed. Martensite formed during quenching in Q & P, when reheated to PT and partitioned, causes tempering, further reducing the strength, but also promotes the formation of bainite. As shown in FIG. 2, even if the partitioning treatment is performed at the same temperature, the TBF which is rapidly cooled to the temperature in the bainite region and maintained at a constant temperature does not completely precipitate bainite even after 600 seconds, and FM is formed. On the other hand, it can be seen that when sufficient martensite is formed, the bainite transformation is completely carried out in a short time and FM is not formed. As described above, the reason for minimizing FM in the present invention is that elements such as carbon and manganese are concentrated in austenite remaining in the bainite transformation process, and the FM does not remain as austenite and is transformed during final cooling. This is because martensite, which has a very high amount of alloying elements, remains, has a very high strength, causes interfacial separation during hole expansion, and easily cracks, which greatly reduces the hole expansion property.
In the present invention, such a property is newly discovered, thereby newly developing a high-formability high-strength steel having a bainite main phase, promoting the formation of bainite, and QT having the maximum bainite area ratio. Was obtained through experiments as follows.
[Relationship formula 1]
QT = 493.497 + 36.2874 x Al-394.0 x C-45.0 x Mn-11.4332 x Mo-20.8772 x Ni-13.038 x Si-12.8 x Cr
Partitioning heat treatment Subsequently, in the present invention, the cooled steel sheet is reheated at the bainite temperature (PT) ± 10 ° C. defined by the following relational expression 2, and then PT-100 ° C. or higher and PT or lower . After holding in the temperature range for 100 seconds or more, cool.
After the above-mentioned quenching, the temperature at which bainite was formed earliest was determined through an experiment when the bainite was reheated at the bainite temperature (PT) and kept at a constant temperature. If the temperature is higher than this, the amount of bainite formed is small, the stabilization of retained austenite is insufficient, and the formation of FM increases conversely, so that the PT must be heated to PT ± 10 ° C.
[Relational expression 2]
PT = 599.088 + 11.5214 × Al-225.2 × C-35.0 × Mn-19.9474 × Ni-24.9385 × Si-56.718 × Mo-22.1 × Cr
Unlike the prior art, in the present invention, it is not necessary to keep the constant temperature at a constant temperature. Since it is sufficient to maintain a constant temperature within a temperature range of PT-100 ° C. or higher and PT or lower for 100 seconds or longer before cooling, it is easy to apply to equipment having a constant temperature furnace without a heating and holding device. Has the advantage of being.
By the Q & P heat treatment in this way, a steel containing 50% or more of bainite, 10% or more of tempered martensite (TM), 10% or less of fresh martensite (FM), 20% or less of retained austenite, and 5% or less of ferrite can be produced. Highly formed giga-class high with excellent yield strength, ductility, and hole expansion compared to steel sheets manufactured by conventional Q & P heat treatment by minimizing ferrite and FM, which have a large difference in strength. A strong steel plate can be manufactured.

（めっき）
上記１次及び２次焼鈍熱処理された冷延鋼板をめっき処理することで、めっき鋼板を製造することができる。このとき、めっき処理は、溶融めっき法または合金化溶融めっき法を用いて行うことが好ましく、これによって形成されためっき層は亜鉛系であることが好ましい。
上記溶融めっき法を用いる場合には、亜鉛めっき浴に浸漬することで溶融めっき鋼板を製造することができ、合金化溶融めっき法の場合にも、一般の合金化溶融めっき処理を行うことで、合金化溶融めっき鋼板を製造することができる。 (Plating)
A plated steel sheet can be manufactured by plating the cold-rolled steel sheet that has undergone the primary and secondary annealing heat treatment. At this time, the plating treatment is preferably performed by using a hot-dip galvanizing method or an alloying hot-dip galvanizing method, and the plating layer formed thereby is preferably zinc-based.
When the above hot-dip galvanizing method is used, a hot-dip galvanized steel sheet can be manufactured by immersing it in a galvanized bath. An alloyed hot-dip galvanized steel sheet can be manufactured.

以下、本発明の実施例について詳細に説明する。 Hereinafter, examples of the present invention will be described in detail.

（実施例）
下記表１に示された成分組成を有する溶融金属で、真空溶解を介して、厚さ９０ｍｍ、幅１７５ｍｍのインゴットを製造した。次に、これを１２００℃で１時間再加熱して均質化処理した後、Ａｒ３以上の温度である９００℃以上で熱間仕上げ圧延して、熱延鋼板を製造した。その後、上記熱延鋼板を冷却した後、予め６００℃に加熱された炉に装入し、１時間保持した後、炉冷させることで、熱延巻取りを模写した。このように熱間圧延された板材を５０〜６０％の冷間圧下率で冷間圧延した後、下記表２の条件で焼鈍熱処理を行い、最終的な冷延鋼板を製造した。
上記のように製造されたそれぞれの冷延鋼板に対して、組織分率、降伏強度、引張強度、伸び、及びＨＥＲを測定し、その結果も表２に示した。 (Example)
An ingot having a thickness of 90 mm and a width of 175 mm was produced from the molten metal having the component compositions shown in Table 1 below through vacuum melting. Next, this was reheated at 1200 ° C. for 1 hour for homogenization treatment, and then hot-finished and rolled at 900 ° C. or higher, which is a temperature of Ar3 or higher, to produce a hot-rolled steel sheet. Then, after cooling the hot-rolled steel sheet, the hot-rolled steel sheet was placed in a furnace preheated to 600 ° C., held for 1 hour, and then cooled in the furnace to replicate the hot-rolled winding. The hot-rolled plate material was cold-rolled at a cold reduction ratio of 50 to 60%, and then annealed heat treatment was performed under the conditions shown in Table 2 below to produce a final cold-rolled steel sheet.
The microstructure fraction, yield strength, tensile strength, elongation, and HER were measured for each cold-rolled steel sheet manufactured as described above, and the results are also shown in Table 2.

Figure 0006846522
Figure 0006846522

Figure 0006846522
＊上記表２において、Ｂはベイナイト、ＴＭは焼戻しマルテンサイト、ＦＭはフレッシュマルテンサイト、Ａは残留オーステナイト、Ｆはフェライトを示す。
Figure 0006846522
 * In Table 2 above, B is bainite, TM is tempered martensite, FM is fresh martensite, A is retained austenite, and F is ferrite.

上記表１に示すように、鋼組成成分だけでなく、製造工程が本発明の範囲を満たす発明例（Ａ―Ｇ）はすべて、優れた降伏強度、延性、及び穴拡げ性を示すことが分かる。 As shown in Table 1 above, it can be seen that not only the steel composition components but also all the invention examples (AG) in which the manufacturing process satisfies the scope of the present invention show excellent yield strength, ductility, and hole expansion property. ..

図３は、本発明により製造された発明例（Ｆ）鋼の微細組織を観察した写真である。表２に示すように、発明例（Ｆ）鋼は、ベイナイトが７５％と主相であり、ＴＭ、ＦＭがそれぞれ１４％、５％とＴＭ／ＦＭが２を超え、Ｆが５％未満のベイナイト鋼を製造することができることが分かる。この点が本発明の技術的特徴であり、従来では、Ｑ＆Ｐ熱処理を通じてフェライト基地のＴＲＩＰ鋼を製造するか、焼戻しマルテンサイト鋼を製造することを主力としたが、本発明のように鋼組成成分及びＱＴ、ＰＴを特定すると、ベイナイト基地組織をＴＢＦ熱処理方法よりも簡単に実現することができる。 FIG. 3 is a photograph of observing the microstructure of the steel of invention example (F) produced by the present invention. As shown in Table 2, in the steel of Invention Example (F), bainite is the main phase with 75%, TM and FM are 14% and 5%, respectively, TM / FM is more than 2, and F is less than 5%. It can be seen that bainite steel can be produced. This point is a technical feature of the present invention. Conventionally, the main focus is to produce ferrite-based TRIP steel or tempered martensitic steel through Q & P heat treatment, but as in the present invention, the steel composition component. And by specifying QT and PT, the bainite matrix structure can be realized more easily than the TBF heat treatment method.

一方、図４は図３の組織のうちＴＭをＡＰＴで観察したものである。遷移炭化物と粗大なセメンタイトが混ざっていることから、焼戻しマルテンサイトであることが分かる。 On the other hand, FIG. 4 shows TM observed by APT in the tissue of FIG. The mixture of transitional carbides and coarse cementite indicates that it is tempered martensite.

これに対し、鋼組成成分や製造工程が本発明の範囲を外れる比較例（Ｈ−Ｌ、Ｂ、Ｅ、Ｇ）はすべて、本発明に比べて降伏強度、延性、及び穴拡げ性がよくないことが分かる。 On the other hand, all the comparative examples (HL, B, E, G) in which the steel composition component and the manufacturing process are out of the scope of the present invention have poor yield strength, ductility, and hole expansion property as compared with the present invention. You can see that.

特に、上記表２に示すように、鋼組成成分は本発明の範囲を満たしているが、製造工程が本発明によらない比較例（Ｂ、Ｅ、Ｇ）はすべて、必要な物性が得られないことが分かる。 In particular, as shown in Table 2 above, the steel composition components satisfy the scope of the present invention, but all the comparative examples (B, E, G) in which the manufacturing process is not based on the present invention can obtain the necessary physical properties. It turns out that there is no such thing.

図５は比較例（Ｅ）鋼の組織であって、成分は同一であるが、二相域焼鈍及びＴＢＦ熱処理により、フェライトとＦＭが形成され、強度及びＨＥＲが低いことが確認できる。 FIG. 5 shows the structure of the steel of Comparative Example (E), which has the same composition, but it can be confirmed that ferrite and FM are formed by two-phase region annealing and TBF heat treatment, and the strength and HER are low.

上記の結果をみると、本発明により製造される冷延鋼板は、９８０ＭＰａ以上の降伏強度、優れた伸び、及びＨＥＲを確保することができるとともに、従来のＱ＆Ｐ熱処理工程を経て製造された鋼材に比べて、構造部材に適用するための冷間成形を簡単に行うことができるという長所がある。 Looking at the above results, the cold-rolled steel sheet produced by the present invention can secure a yield strength of 980 MPa or more, excellent elongation, and HER, and is a steel material produced through a conventional Q & P heat treatment process. In comparison, it has the advantage that cold forming for application to structural members can be easily performed.

以上、本発明の実施形態について詳細に説明したが、本発明の範囲はこれに限定されず、特許請求の範囲に記載された本発明の技術的思想から外れない範囲内で多様な修正及び変形が可能であるということは、当技術分野の通常の知識を有する者には明らかである。 Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to this, and various modifications and modifications are made within the scope of the technical idea of the present invention described in the claims. It is clear to those with ordinary knowledge in the art that this is possible.

Claims (8)

重量％で、炭素（Ｃ）：０．０６〜０．２％、マンガン（Ｍｎ）：１．５〜３．０％、ケイ素（Ｓｉ）：０．３〜２．５％、アルミニウム（Ａｌ）：０．０１〜０．２％、ニッケル（Ｎｉ）：０．０１〜３．０％、モリブデン（Ｍｏ）：０．２％以下、チタン（Ｔｉ）：０．０１〜０．０５、アンチモン（Ｓｂ）：０．０２〜０．０５、ホウ素（Ｂ）：０．０００５〜０．００３、窒素（Ｎ）：０．０１％以下（０％は除く）、残部Ｆｅ及び不可避不純物を含み、
その微細組織が、面積分率で、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下からなる、降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板。 By weight%, carbon (C): 0.06 to 0.2%, manganese (Mn): 1.5 to 3.0%, silicon (Si): 0.3 to 2.5%, aluminum (Al) : 0.01 to 0.2%, nickel (Ni): 0.01 to 3.0%, molybdenum (Mo): 0.2% or less, titanium (Ti): 0.01 to 0.05, antimony ( Sb): 0.02 to 0.05, boron (B): 0.0005 to 0.003, nitrogen (N): 0.01% or less (excluding 0%), balance Fe and unavoidable impurities.
Its microstructure, in area fraction, bainite 50% or more, tempered martensite (TM) 10% or more, fresh martensite (FM) 10% or less, consisting of residual austenite of 20% or less, and ferrite 5%, the yield High-strength cold-rolled steel sheet with excellent strength, ductility, and hole expansion. 前記ＴＭ／ＦＭの比が２を超える、請求項１に記載の降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板。 The high-strength cold-rolled steel sheet having an excellent TM / FM ratio of more than 2 and having excellent yield strength, ductility, and hole expansion property according to claim 1. 請求項１又は２に記載の冷延鋼板の表面に溶融亜鉛めっき処理された、溶融亜鉛めっき鋼板。 A hot-dip galvanized steel sheet obtained by hot-dip galvanizing the surface of the cold-rolled steel sheet according to claim 1 or 2. 請求項１又は２に記載の冷延鋼板の表面に合金化溶融亜鉛めっき処理された、合金化溶融亜鉛めっき鋼板。 An alloyed hot-dip galvanized steel sheet obtained by subjecting the surface of the cold-rolled steel sheet according to claim 1 or 2 to an alloyed hot-dip galvanized steel sheet. 重量％で、炭素（Ｃ）：０．０６〜０．２％、マンガン（Ｍｎ）：１．５〜３．０％、ケイ素（Ｓｉ）：０．３〜２．５％、アルミニウム（Ａｌ）：０．０１〜０．２％、ニッケル（Ｎｉ）：０．０１〜３．０％、モリブデン（Ｍｏ）：０．２％以下、チタン（Ｔｉ）：０．０１〜０．０５、アンチモン（Ｓｂ）：０．０２〜０．０５、ホウ素（Ｂ）：０．０００５〜０．００３、窒素（Ｎ）：０．０１％以下（０％は除く）、残部Ｆｅ及び不可避不純物を含む鋼スラブを再加熱し、次いで、熱間圧延した後、巻取る工程と、
前記巻取られた熱延鋼板を冷間圧延した後、Ｑ＆Ｐ連続焼鈍する工程と、を含み、
前記Ｑ＆Ｐ連続焼鈍する工程は、
前記製造された冷延鋼板をＡｃ３以上の温度で３０秒以上均熱し、次いで、５〜２０℃／秒の冷却速度で下記関係式１で定義される焼入れ温度（ＱＴ）±１０℃まで冷却する工程と、
前記冷却された鋼板を下記関係式２で定義されるベイナイト温度（ＰＴ）±１０℃で再加熱し、次いで、ＰＴ−１００℃以上でありＰＴ以下の温度範囲内で１００秒以上保持した後、冷却する工程と、を含み、
前記Ｑ＆Ｐ連続焼鈍が完了した鋼板は、その微細組織が、面積分率で、ベイナイト５０％以上、焼戻しマルテンサイト（ＴＭ）１０％以上、フレッシュマルテンサイト（ＦＭ）１０％以下、残留オーステナイト２０％以下、及びフェライト５％以下からなる、降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板の製造方法。
［関係式１］
ＱＴ＝４９３．４９７＋３６．２８７４×Ａｌ−３９４．０×Ｃ−４５．０×Ｍｎ−１１．４３３２×Ｍｏ−２０．８７７２×Ｎｉ−１３．０４３８×Ｓｉ−１２．８×Ｃｒ
［関係式２］
ＰＴ＝５９９．０８８＋１１．５２１４×Ａｌ−２２５．２×Ｃ−３５．０×Ｍｎ−１９．９４７４×Ｎｉ−２４．９３８５×Ｓｉ−５６．７１８×Ｍｏ−２２．１×Ｃｒ By weight%, carbon (C): 0.06 to 0.2%, manganese (Mn): 1.5 to 3.0%, silicon (Si): 0.3 to 2.5%, aluminum (Al) : 0.01 to 0.2%, nickel (Ni): 0.01 to 3.0%, molybdenum (Mo): 0.2% or less, titanium (Ti): 0.01 to 0.05, antimony ( Sb): 0.02 to 0.05, boron (B): 0.0005 to 0.003, nitrogen (N): 0.01% or less (excluding 0%), steel slab containing the balance Fe and unavoidable impurities Reheated, then hot rolled and then wound.
Including a step of cold-rolling the wound hot-rolled steel sheet and then continuously annealing Q & P.
The step of continuous annealing of Q & P is
The produced cold-rolled steel sheet is soaked at a temperature of Ac3 or higher for 30 seconds or longer, and then cooled to a quenching temperature (QT) of ± 10 ° C. defined by the following relational expression 1 at a cooling rate of 5 to 20 ° C./sec. Process and
The cooled steel sheet is reheated at a bainite temperature (PT) of ± 10 ° C. defined by the following relational expression 2, and then held in a temperature range of PT-100 ° C. or higher and PT or lower for 100 seconds or longer. and the step of cooling, only including,
The steel sheet for which the Q & P continuous annealing has been completed has a fine structure of bainite of 50% or more, tempered martensite (TM) of 10% or more, fresh martensite (FM) of 10% or less, and retained austenite of 20% or less. A method for producing a high-strength cold-rolled steel sheet, which comprises 5% or less of ferrite and has excellent yield strength, ductility, and hole expansion property.
[Relationship formula 1]
QT = 493.497 + 36.2874 x Al-394.0 x C-45.0 x Mn-11.4332 x Mo-20.8772 x Ni-13.038 x Si-12.8 x Cr
[Relational expression 2]
PT = 599.088 + 11.5214 × Al-225.2 × C-35.0 × Mn-19.9474 × Ni-24.9385 × Si-56.718 × Mo-22.1 × Cr 前記ＴＭ／ＦＭの比が２を超える、請求項５に記載の降伏強度、延性、及び穴拡げ性に優れた高強度冷延鋼板の製造方法。 The method for producing a high-strength cold-rolled steel sheet having an excellent TM / FM ratio of more than 2 and excellent in yield strength, ductility, and hole expansion property according to claim 5. 請求項５又は６に記載の高強度冷延鋼板の製造方法にしたがって得られるＱ＆Ｐ連続焼鈍された冷延鋼板の表面に溶融亜鉛めっき処理する工程をさらに含む、降伏強度、延性、及び穴拡げ性に優れた溶融亜鉛めっき鋼板の製造方法。 Yield strength, ductility, and hole expandability further include a step of hot-dip galvanizing the surface of the Q & P continuously annealed cold-rolled steel sheet obtained according to the method for producing a high-strength cold-rolled steel sheet according to claim 5 or 6. An excellent method for manufacturing hot-dip galvanized steel sheets. 請求項５又は６に記載の高強度冷延鋼板の製造方法にしたがって得られるＱ＆Ｐ連続焼鈍された冷延鋼板の表面に合金化溶融亜鉛めっき処理する工程をさらに含む、降伏強度、延性、及び穴拡げ性に優れた合金化溶融亜鉛めっき鋼板の製造方法。 Yield strength, ductility, and holes further include a step of alloying hot dip galvanizing the surface of a Q & P continuously annealed cold-dip steel sheet obtained according to the method for producing a high-strength cold-rolled steel sheet according to claim 5 or 6. A method for manufacturing alloyed hot-dip galvanized steel sheets with excellent spreadability.
JP2019531765A 2016-12-16 2017-11-29 High-strength cold-rolled steel sheets with excellent yield strength, ductility, and hole expansion properties, hot-dip galvanized steel sheets, and methods for manufacturing these. Active JP6846522B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR1020160173006A KR101858852B1 (en) 2016-12-16 2016-12-16 Cold-rolled steel sheet and galvanized steel sheet having excelent elonggation, hole expansion ration and yield strength and method for manufacturing thereof
KR10-2016-0173006 2016-12-16
PCT/KR2017/013762 WO2018110867A1 (en) 2016-12-16 2017-11-29 High strength cold rolled steel plate having excellent yield strength, ductility, and hole expandability, hot dip galvanized steel plate, and method for producing same

Publications (2)

Publication Number Publication Date
JP2020509177A JP2020509177A (en) 2020-03-26
JP6846522B2 true JP6846522B2 (en) 2021-03-24

Family

ID=62558805

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2019531765A Active JP6846522B2 (en) 2016-12-16 2017-11-29 High-strength cold-rolled steel sheets with excellent yield strength, ductility, and hole expansion properties, hot-dip galvanized steel sheets, and methods for manufacturing these.

Country Status (6)

Country Link
US (1) US20200190612A1 (en)
EP (1) EP3556896B1 (en)
JP (1) JP6846522B2 (en)
KR (1) KR101858852B1 (en)
CN (1) CN110073026B (en)
WO (1) WO2018110867A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115161541A (en) * 2021-04-02 2022-10-11 宝山钢铁股份有限公司 780 MPa-grade high-formability hot-dip galvanized dual-phase steel and rapid heat treatment hot-dip galvanizing manufacturing method

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11753693B2 (en) 2018-09-28 2023-09-12 Posco Co., Ltd High-strength cold rolled steel sheet having high hole expansion ratio, highstrength hot-dip galvanized steel sheet, and manufacturing methods therefor
CN109576579A (en) 2018-11-29 2019-04-05 宝山钢铁股份有限公司 It is a kind of with high hole expansibility and compared with the 980MPa grade cold-rolled steel sheet and its manufacturing method of high-elongation
US11926881B2 (en) 2019-08-20 2024-03-12 Jfe Steel Corporation High-strength cold-rolled steel sheet and method for manufacturing the same
CN110964969B (en) * 2019-11-27 2021-09-21 本钢板材股份有限公司 High-strength hot-dip galvanized quenching distribution steel and production method thereof
WO2021123877A1 (en) * 2019-12-17 2021-06-24 Arcelormittal Hot rolled steel sheet and method of manufacturing thereof
CN115181895B (en) * 2021-04-02 2023-09-12 宝山钢铁股份有限公司 1180 MPa-level low-carbon low-alloy hot dip galvanized Q & P steel and rapid heat treatment hot dip galvanizing manufacturing method
CN113186459B (en) * 2021-04-08 2022-09-13 山东钢铁股份有限公司 Cold-rolled low-alloy steel strip with yield strength of 355MPa and preparation method thereof
KR20230073569A (en) * 2021-11-19 2023-05-26 주식회사 포스코 Cold rolled steel sheet having excellent strength and formability and method of manufacturing the same

Family Cites Families (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR940002370B1 (en) 1991-05-16 1994-03-23 주식회사 금성사 Cooking time control apparatus and method of microwave oven
KR940007374B1 (en) 1992-07-24 1994-08-16 포항종합제철 주식회사 Method of manufacturing austenite stainless steel
JP3942799B2 (en) 2000-04-27 2007-07-11 カルソニックカンセイ株式会社 Method and apparatus for separating insert metal fittings of resin molded product
JP2002177278A (en) 2000-12-15 2002-06-25 Hitachi Medical Corp Ultrasonic diagnostic device
US7090731B2 (en) * 2001-01-31 2006-08-15 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) High strength steel sheet having excellent formability and method for production thereof
WO2004022794A1 (en) 2002-09-04 2004-03-18 Colorado School Of Mines Method for producing steel with retained austenite
JP4729850B2 (en) * 2003-02-10 2011-07-20 Ｊｆｅスチール株式会社 Alloyed hot-dip galvanized steel sheet with excellent plating adhesion and method for producing the same
KR100928788B1 (en) * 2007-12-28 2009-11-25 주식회사 포스코 High strength steel sheet with excellent weldability and manufacturing method
JP5418047B2 (en) * 2008-09-10 2014-02-19 Ｊｆｅスチール株式会社 High strength steel plate and manufacturing method thereof
KR20100076409A (en) * 2008-12-26 2010-07-06 주식회사 포스코 A high strength steel sheet having high yield ratio and a method for producting the same
JP5446885B2 (en) * 2010-01-06 2014-03-19 新日鐵住金株式会社 Cold rolled steel sheet manufacturing method
WO2013051238A1 (en) * 2011-10-04 2013-04-11 Ｊｆｅスチール株式会社 High-strength steel sheet and method for manufacturing same
CN104245971B (en) * 2012-03-30 2017-09-12 奥钢联钢铁有限责任公司 High strength cold rolled steel plate and the method for producing the steel plate
JP5954011B2 (en) 2012-07-18 2016-07-20 凸版印刷株式会社 Microneedle penetration control device
JP5857909B2 (en) * 2012-08-09 2016-02-10 新日鐵住金株式会社 Steel sheet and manufacturing method thereof
KR101299896B1 (en) * 2013-05-30 2013-08-23 주식회사 포스코 METHOD FOR MANUFACTURING TENSILE STRENGTH 1.5GPa CLASS STEEL SHEET
JP5728108B2 (en) * 2013-09-27 2015-06-03 株式会社神戸製鋼所 High-strength steel sheet with excellent workability and low-temperature toughness, and method for producing the same
WO2015088523A1 (en) * 2013-12-11 2015-06-18 ArcelorMittal Investigación y Desarrollo, S.L. Cold rolled and annealed steel sheet
US10174396B2 (en) * 2014-01-29 2019-01-08 Jfe Steel Corporation High-strength cold-rolled steel sheet and method for manufacturing the same (as amended)
JP6306481B2 (en) * 2014-03-17 2018-04-04 株式会社神戸製鋼所 High-strength cold-rolled steel sheet and high-strength hot-dip galvanized steel sheet excellent in ductility and bendability, and methods for producing them
KR101594670B1 (en) * 2014-05-13 2016-02-17 주식회사 포스코 Cold-rolled steel sheet and galvanized steel sheet having excellent ductility and method for manufacturing thereof
WO2016001700A1 (en) * 2014-07-03 2016-01-07 Arcelormittal Method for producing a high strength steel sheet having improved strength, ductility and formability
WO2016020714A1 (en) * 2014-08-07 2016-02-11 Arcelormittal Method for producing a coated steel sheet having improved strength, ductility and formability
WO2016103535A1 (en) * 2014-12-22 2016-06-30 Ｊｆｅスチール株式会社 High-strength hot-dip galvanized steel sheet and manufacturing method thereof
EP3246425B1 (en) * 2015-01-16 2019-12-04 JFE Steel Corporation High-strength steel sheet and production method therefor
EP3276022B1 (en) * 2015-03-25 2019-09-04 JFE Steel Corporation Cold-rolled steel sheet and manufacturing method therefor
JP6586776B2 (en) * 2015-05-26 2019-10-09 日本製鉄株式会社 High strength steel plate with excellent formability and method for producing the same
KR102081361B1 (en) * 2015-06-11 2020-02-25 닛폰세이테츠 가부시키가이샤 Alloyed hot dip galvanized steel sheet and its manufacturing method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115161541A (en) * 2021-04-02 2022-10-11 宝山钢铁股份有限公司 780 MPa-grade high-formability hot-dip galvanized dual-phase steel and rapid heat treatment hot-dip galvanizing manufacturing method
CN115161541B (en) * 2021-04-02 2023-08-11 宝山钢铁股份有限公司 780 MPa-level high-formability hot dip galvanized dual phase steel and rapid heat treatment hot dip galvanizing manufacturing method

Also Published As

Publication number Publication date
EP3556896B1 (en) 2021-11-10
JP2020509177A (en) 2020-03-26
KR101858852B1 (en) 2018-06-28
EP3556896A4 (en) 2019-10-23
CN110073026B (en) 2021-09-07
WO2018110867A1 (en) 2018-06-21
US20200190612A1 (en) 2020-06-18
CN110073026A (en) 2019-07-30
EP3556896A1 (en) 2019-10-23
WO2018110867A8 (en) 2019-01-31

Similar Documents

Publication Publication Date Title
JP6846522B2 (en) High-strength cold-rolled steel sheets with excellent yield strength, ductility, and hole expansion properties, hot-dip galvanized steel sheets, and methods for manufacturing these.
JP6383808B2 (en) High-strength cold-rolled steel sheet having excellent ductility, hot-dip galvanized steel sheet, and production methods thereof
JP7275137B2 (en) Steel plate with excellent toughness, ductility and strength and method for producing the same
JP6766190B2 (en) Ultra-high-strength, high-ductility steel sheet with excellent yield strength and its manufacturing method
JP2019506530A (en) High strength steel plate having excellent formability and method of manufacturing the same
JP6093702B2 (en) Cold rolled flat steel product made from multiphase steel and its manufacturing method
JP6636962B2 (en) Method for producing high-strength steel sheet and steel sheet obtained by this method
JP5487215B2 (en) Manufacturing method of high-strength, high-stretched steel sheet, hot-rolled steel sheet, cold-rolled steel sheet, galvanized steel sheet and galvanized alloyed steel sheet
KR101786318B1 (en) Cold-rolled steel sheet and plated steel sheet having excellent yield strength and ductility and method for manufacturing thereof
JP2023093564A (en) Hot-forming member
JP6804566B2 (en) High-strength cold-rolled steel sheet with excellent workability and its manufacturing method
JP6619079B2 (en) Hot-dip galvanized steel sheet excellent in aging resistance and bake hardenability, alloyed hot-dip galvanized steel sheet, and method for producing the same
JP5280795B2 (en) Method for producing high-strength cold-rolled steel sheet with excellent mechanical property stability
JP2018502992A (en) Composite steel sheet with excellent formability and method for producing the same
JP5846113B2 (en) High strength thin steel sheet with excellent dent resistance and method for producing the same
JP2021502480A (en) Ultra-high-strength, high-ductility steel sheet with excellent cold formability and its manufacturing method
JP2022548259A (en) Steel sheet excellent in uniform elongation rate and work hardening rate and method for producing the same
KR101435251B1 (en) Method of manufacturing cold-rolled steel sheet
KR20100047000A (en) High-strength steel sheet having excellent galvanizing property, and method for producing the same
KR20130071208A (en) High strength steel sheet with excellent coatability and method for manufacturing the same

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20190805

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20200826

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20200901

A521 Request for written amendment filed

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20201130

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: 20210202

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20210301

R150 Certificate of patent or registration of utility model

Ref document number: 6846522

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R150

S531 Written request for registration of change of domicile

Free format text: JAPANESE INTERMEDIATE CODE: R313531

S533 Written request for registration of change of name

Free format text: JAPANESE INTERMEDIATE CODE: R313533

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

S111 Request for change of ownership or part of ownership

Free format text: JAPANESE INTERMEDIATE CODE: R313113

R371 Transfer withdrawn

Free format text: JAPANESE INTERMEDIATE CODE: R371

S111 Request for change of ownership or part of ownership

Free format text: JAPANESE INTERMEDIATE CODE: R313113

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

R250 Receipt of annual fees

Free format text: JAPANESE INTERMEDIATE CODE: R250