JP2000355735A - Hot rolled high strength steel sheet small in variation of material and excellent in workability and its production - Google Patents
Hot rolled high strength steel sheet small in variation of material and excellent in workability and its productionInfo
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- JP2000355735A JP2000355735A JP16807599A JP16807599A JP2000355735A JP 2000355735 A JP2000355735 A JP 2000355735A JP 16807599 A JP16807599 A JP 16807599A JP 16807599 A JP16807599 A JP 16807599A JP 2000355735 A JP2000355735 A JP 2000355735A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は自動車、産業機械等
に使用することを可能とする加工性が良好で、しかも材
質バラツキの小さい熱延高強度鋼板とその製造方法に関
するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled high-strength steel sheet which can be used in automobiles, industrial machines and the like, has good workability, and has a small variation in material.
【０００２】[0002]
【従来の技術】近年の自動車産業において自動車の燃費
改善対策の１つとして車体の軽量化を図る傾向にあり、
そのために使用鋼鈑の薄肉化によって軽量化する方法が
とられてきた。しかしながら薄肉化に伴い、鋼鈑強度が
低下するため安全性の面から課題があった。そこで薄肉
化加工性に優れた高強度鋼鈑、特に強度−延性バランス
としてＴＳ×Ｔ．Ｅｌ≧２００００（ＭＰａ・％）の要
求がなされて来ている。従来、加工性に優れた高強度熱
延鋼鈑を得る方法として特開平３−１８０４４５号公報
が提示されている。しかし、工業的に実使用する場合
は、強度−延性バランスとしてＴＳ×Ｔ．Ｅｌ≧２００
００（ＭＰａ）であるばかりでなく、その材質ばらつき
も小さいことが必要である。即ち強度−延性バランスの
バラツキが大きい場合、一定条件で実施される連続成形
にて、寸法変動等の製品での不具合が発生し、製品歩留
が低下する問題があるため、工業的に安定して製品を生
産するため需要家からの要望として強度−延性バランス
の変動を３０００（ＭＰａ・％）未満に制御する必要が
ある。しかし、このような強度−延性バランス及び強度
−延性バランスの変動を達成し、工業的に実使用できる
加工性に優れた高強度熱延鋼鈑は未だ提供されていない
のが現状である。2. Description of the Related Art In the recent automobile industry, there is a tendency to reduce the weight of a vehicle body as one of measures for improving fuel efficiency of an automobile.
Therefore, a method of reducing the weight by reducing the thickness of the steel plate used has been adopted. However, there is a problem in terms of safety because the strength of the steel sheet is reduced with the reduction in thickness. Therefore, a high strength steel sheet excellent in thinning workability, especially TS × T. There has been a demand for El ≧ 20000 (MPa ·%). Conventionally, JP-A-3-180445 has been proposed as a method for obtaining a high-strength hot-rolled steel sheet having excellent workability. However, in the case of industrial use, TS × T. El ≧ 200
It is necessary that the material has a small variation in material as well as 00 (MPa). That is, when the dispersion of the strength-ductility balance is large, there is a problem in the product such as a dimensional variation in continuous molding performed under a constant condition, and there is a problem that a product yield is reduced, so that it is industrially stable. It is necessary to control the fluctuation of the strength-ductility balance to be less than 3000 (MPa ·%) as a demand from customers to produce products. However, at present, a high-strength hot-rolled steel sheet which achieves such fluctuations in the strength-ductility balance and the strength-ductility balance and has excellent workability that can be used industrially has not yet been provided.
【０００３】従来、加工性に優れた熱延高強度鋼板を得
る方法として特開平０１−７９３４５号公報が提示され
ている。Hitherto, Japanese Patent Application Laid-Open No. 01-79345 has been proposed as a method for obtaining a hot-rolled high-strength steel sheet having excellent workability.
【０００４】しかし、工業的に実使用する場合は、加工
性に優れ、しかも、その材質バラツキが小さいことが必
要である。材質バラツキが大きい場合、一定条件で実施
される連続成形にて、寸法変動等の製品での不具合が発
生する。さらに、このような熱延高強度鋼板は、その用
途からして優れたスポット溶接性をも要求される。[0004] However, in the case of industrial use, it is necessary that the workability is excellent and the material variability is small. In the case where the material variation is large, problems such as dimensional fluctuations occur in products in continuous molding performed under constant conditions. Further, such a hot-rolled high-strength steel sheet is also required to have excellent spot weldability for its use.
【０００５】[0005]
【発明が解決しようとする課題】本発明は上記した従来
技術が持つ問題点を解消し、優れた加工性を持ち材質バ
ラツキの小さい熱延高強度鋼板、及び優れた加工性を持
ち材質バラツキが小さく、かつスポット溶接性に優れた
熱延高強度鋼板、並びにそれらの製造方法を提供するこ
とを課題としている。DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides a hot-rolled high-strength steel sheet having excellent workability and a small variation in material. It is an object of the present invention to provide a hot-rolled high-strength steel sheet which is small and has excellent spot weldability, and a method for producing the same.
【０００６】[0006]
【課題を解決するための手段】本発明者らは、上記課題
を解決するために、Ｂが材質特性及びそのバラツキに及
ぼす影響について種々の実験検討を重ねた結果、加工用
高強度熱延鋼板の化学成分の関係及び不純物として存在
するＢの上限を規定することにより、加工性に優れた材
質バラツキの小さい高強度熱延鋼板を得ることが出来る
ことを知見した。In order to solve the above-mentioned problems, the present inventors have conducted various experiments and studies on the effects of B on the material properties and its variation, and as a result, have found that high-strength hot-rolled steel sheets for processing. It has been found that a high-strength hot-rolled steel sheet excellent in workability and having small material variation can be obtained by defining the relationship between the chemical components and the upper limit of B present as an impurity.
【０００７】そして、この不純物として存在するＢの上
限を０．０００５重量％、好ましくは０．０００２重量
％以下とすることにより、フェライト変態を安定的に進
行させ、フェライト占積率やその粒径の変動を抑制する
ことが可能となり、その他元素とあいまって、成形性指
標である強度延性バランスの高レベル維持とそのバラツ
キ低減を果たし得ること、さらに、Ｃを０．０５〜０．
１５重量％未満迄低減しても、強度・延性バランスはも
とより高穴拡げ性の低下をみることなく、スポット溶接
性を向上させ得ることを見出して本発明を完成したので
ある。By setting the upper limit of B present as an impurity to 0.0005% by weight, preferably 0.0002% by weight or less, the ferrite transformation proceeds stably, and the ferrite space factor and the particle size thereof are increased. Can be suppressed, and, together with other elements, can maintain a high level of the strength-ductility balance, which is an index of formability, and can reduce the variation thereof.
The inventors have found that even when the content is reduced to less than 15% by weight, it is possible to improve the spot weldability without deteriorating the strength-ductility balance and the high hole expandability, and completed the present invention.
【０００８】本発明の要旨は、以下の通りである。The gist of the present invention is as follows.
【０００９】（１） 化学成分として重量％で、Ｃ：
０．０５〜０．４％、Ｓｉ：０．５〜３．０％、Ｍｎ：
０．５〜３．０％、Ｐ：０．１％以下、Ｓ：０．０５％
以下、Ａｌ：０．１％以下含み、不純物としてのＢ：
０．０００５％以下に制限し、残部Ｆｅ及び不可避的不
純物であり、特性として、強度−延性バランス（引張強
さ×全伸び）が２００００（ＭＰａ・％）以上で、か
つ、そのコイル内変動が３０００（ＭＰａ・％）未満で
あることを特徴とする材質バラツキの小さい加工性に優
れた熱延高強度鋼板。(1) C:
0.05-0.4%, Si: 0.5-3.0%, Mn:
0.5 to 3.0%, P: 0.1% or less, S: 0.05%
Hereinafter, Al: 0.1% or less, and B as an impurity:
0.0005% or less, the balance being Fe and unavoidable impurities. As a characteristic, the strength-ductility balance (tensile strength × total elongation) is 20,000 (MPa ·%) or more, and the variation in the coil is A hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized by being less than 3000 (MPa ·%).
【００１０】（２） 化学成分として重量％で、Ｃ：
０．０５〜０．４％、Ｓｉ：０．５〜３．０％、Ｍｎ：
０．５〜３．０％、Ｐ：０．１％以下、Ｓ：０．０５％
以下、Ａｌ：０．１％以下、Ｎ：０．１％以下含み、不
純物としてのＢ：０．０００５％以下に制限し、残部Ｆ
ｅ及び不可避的不純物であり、特性として、強度−延性
バランス（引張強さ×全伸び）が２００００（ＭＰａ・
％）以上で、かつ、そのコイル内変動が３０００（ＭＰ
ａ・％）未満であることを特徴とする材質バラツキの小
さい加工性に優れた熱延高強度鋼板。(2) C:
0.05-0.4%, Si: 0.5-3.0%, Mn:
0.5 to 3.0%, P: 0.1% or less, S: 0.05%
In the following, Al: 0.1% or less, N: 0.1% or less, B: 0.0005% or less as an impurity, and the balance F
e and unavoidable impurities, and as a characteristic, the strength-ductility balance (tensile strength × total elongation) is 20,000 (MPa ·
%) And the variation in the coil is 3000 (MP
a.%), a hot-rolled high-strength steel sheet excellent in workability with small material variation.
【００１１】（３） 化学成分として重量％で、Ｃ：
０．１５〜０．３％、Ｓｉ：０．５〜３．０％、Ｍｎ：
０．５〜３．０％、Ｐ：０．１％以下、Ｓ：０．０５％
以下、Ａｌ：０．１％以下、Ｎ：０．１％以下含み、不
純物としてのＢ：０．０００５％以下に制限し、残部Ｆ
ｅ及び不可避的不純物であり、ミクロ組織として、ポリ
ゴナルフェライト占積率ＶPF（％）とポリゴナルフェラ
イト平均粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でか
つ残留オーステナイトを体積比で５％以上含むフェライ
ト、ベイナイト及び残留オーステナイトの組織から構成
され、特性として、強度−延性バランスＴＳ×Ｔ．Ｅｌ
が２００００（ＭＰａ・％）以上で、かつ、そのコイル
内変動が３０００（ＭＰａ・％）未満であることを特徴
とする材質バラツキの小さい加工性に優れた熱延高強度
鋼板。(3) C:
0.15 to 0.3%, Si: 0.5 to 3.0%, Mn:
0.5 to 3.0%, P: 0.1% or less, S: 0.05%
In the following, Al: 0.1% or less, N: 0.1% or less, B: 0.0005% or less as an impurity, and the balance F
e and unavoidable impurities. As a microstructure, the ratio of polygonal ferrite space factor V PF (%) to polygonal ferrite average particle size d PF (μm) ratio V PF / d PF is 7 or more and residual austenite is It is composed of a structure of ferrite, bainite and retained austenite containing 5% or more by volume, and has a strength-ductility balance TS × T. El
A hot-rolled high-strength steel sheet excellent in workability with a small variation in material, characterized by having a variation of at least 20,000 (MPa ·%) and a coil variation of less than 3,000 (MPa ·%).
【００１２】（４） 化学成分として重量％で、Ｃ：
０．０５〜０．１５％未満、Ｓｉ：０．５〜２．５％、
Ｍｎ：０．５〜２．５％、Ｐ：０．０２％以下、Ｓ：
０．０１％以下、Ａｌ：０．００５〜０．１％を含み、
１．６％＜Ｓｉ＋Ｍｎ≦５．０％を満たし、不純物とし
てのＢ：０．０００５％以下に制限し、残部Ｆｅ及び不
可避的不純物であり、ミクロ組織はポリゴナルフェライ
ト占積率ＶPF（％）とポリゴナルフェライト粒径ｄ
PF（μｍ）の比ＶPF／ｄPFが２０以上、残留オーステナ
イトの占積率が５％以上で残部がベイナイトからなり、
特性として、強度−延性バランス（引張強さ×全伸び）
が２００００（ＭＰａ・％）以上で、かつ、そのコイル
内変動が３０００（ＭＰａ・％）未満であることを特徴
とする材質バラツキの小さい加工性とスポット溶接性に
優れた熱延高強度鋼板。(4) C:
0.05 to less than 0.15%, Si: 0.5 to 2.5%,
Mn: 0.5 to 2.5%, P: 0.02% or less, S:
0.01% or less, Al: 0.005 to 0.1%,
1.6% <Si + Mn ≦ 5.0%, B as an impurity is limited to 0.0005% or less, the balance is Fe and inevitable impurities, and the microstructure is polygonal ferrite space factor V PF (% ) And polygonal ferrite particle size d
The ratio V PF / d PF of PF (μm) is 20 or more, the space factor of retained austenite is 5% or more, and the balance is bainite,
Characteristic is strength-ductility balance (tensile strength x total elongation)
A hot-rolled high-strength steel sheet excellent in workability with small material variability and spot weldability, characterized by having a variance of 20,000 (MPa ·%) or more and a coil variation of less than 3000 (MPa ·%).
【００１３】（５） 化学成分として重量％で、さら
に、Ｃｕ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｃａ、
ＲＥＭの１種又は２種以上を含有し、その内Ｃｕ、Ｎ
ｉ、Ｃｒ、Ｍｏにおいては、それらの１種又は２種以上
を合計量で０．５％以下、Ｎｂ、Ｔｉ、Ｖにおいては、
それらの１種又は２種以上を合計量で０．３％以下、Ｃ
ａにおいては０．０１％以下、ＲＥＭにおいては０．０
５％以下であることを特徴とする前記（１）乃至（４）
項の内の何れか１つに記載の熱延高強度鋼板。(5) By weight percent as a chemical component, Cu, Ni, Cr, Mo, Nb, Ti, V, Ca,
Contains one or more REMs, of which Cu, N
In i, Cr and Mo, one or more of them are 0.5% or less in total, and in Nb, Ti and V,
One or two or more of them, in a total amount of 0.3% or less, C
0.01% or less in a, 0.0% in REM
(1) to (4), wherein the content is 5% or less.
Item 14. The hot-rolled high-strength steel sheet according to any one of the above items.
【００１４】（６） 前記（１）又は（２）項に記載の
化学成分の鋼を、仕上圧延終了温度Ａｒ3−５０℃〜Ａ
ｒ3＋５０℃、全圧下率８０％以上で熱間圧延を行い、
続いて３５０℃〜５００℃までを、冷却速度４０℃／ｓ
以上で冷却して巻取ることを特徴とする材質バラツキの
小さい加工性に優れた熱延高強度鋼板の製造方法。(6) The steel having the chemical composition described in the above (1) or (2) is subjected to finish rolling end temperature Ar 3 -50 ° C. to A
hot rolling at r 3 + 50 ° C., total reduction 80% or more,
Subsequently, a cooling rate of 40 ° C./s from 350 ° C. to 500 ° C.
A method for producing a hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized by cooling and winding as described above.
【００１５】（７） 前記（１）又は（２）項に記載の
化学成分の鋼を、仕上圧延開始温度をＡｒ3＋１００℃
以下、仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０
℃、全圧下率８０％以上で熱間圧延を行い、続いて３５
０℃〜５００℃までを、冷却速度４０℃／ｓ以上で冷却
して巻取り後、鋼板を３０℃／ｈｒ以上の冷却速度で２
００℃以下まで冷却することを特徴とする材質バラツキ
の小さい加工性に優れた熱延高強度鋼板の製造方法。(7) The steel having the chemical composition described in the above (1) or (2), the finish rolling start temperature is Ar 3 + 100 ° C.
Hereinafter, finish rolling temperature Ar 3 -50 ℃ ~Ar 3 +50
Hot rolling at 80 ° C. and a total draft of 80% or more.
After cooling from 0 ° C to 500 ° C at a cooling rate of 40 ° C / s or more and winding, the steel sheet is cooled at a cooling rate of 30 ° C / hr or more for 2 hours.
A method for producing a hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized in that the steel sheet is cooled to 00 ° C or less.
【００１６】（８） 前記（３）項に記載の化学成分の
鋼を、仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０
℃、全圧下率８０％以上で熱間圧延を行い、該温度から
４０℃／ｓ未満の冷却速度で冷却を開始し、その鋼のＡ
ｒ3以下でかつ前記圧延終了温度より低い温度からＡｒ1
より高い温度範囲内の任意の温度Ｔで前記冷却を終了
し、続いて冷却速度４０℃／ｓ以上で冷却して３５０℃
〜５００℃で巻取り、ポリゴナルフェライト占面率ＶPF
（％）とポリゴナルフェライト平均粒径ｄPF（μｍ）の
比ＶPF／ｄPFが７以上でかつ残留オーステナイトを体積
比で５％以上含むフェライト、ベイナイト及び残留オー
ステナイトの組織とすることを特徴とする材質バラツキ
の小さい加工性に優れた熱延高強度鋼板の製造方法。(8) The steel having the chemical composition described in the above (3) is subjected to finish rolling end temperature Ar 3 -50 ° C. to Ar 3 +50.
Hot rolling at 80 ° C. and a total reduction of 80% or more, starting cooling from the temperature at a cooling rate of less than 40 ° C./s,
r 3 Ar 1 from less and lower than the rolling end temperature Temperature
The cooling is terminated at an arbitrary temperature T within a higher temperature range, and then cooled at a cooling rate of 40 ° C./s or more to 350 ° C.
Winded at ~ 500 ° C, polygonal ferrite area coverage V PF
(%) And polygonal ferrite average particle diameter d PF (μm) VPF / dPF is 7 or more, and the structure is composed of ferrite, bainite and retained austenite containing 5% or more by volume of retained austenite. A method for producing a hot-rolled high-strength steel sheet having excellent workability with small material variations.
【００１７】（９） 前記（３）項に記載の化学成分の
鋼を、全圧下率８０％以上の熱間仕上圧延を行い、その
圧延終了温度をＡｒ3−５０℃〜Ａｒ3＋５０℃とし、続
いて前記鋼のＡｒ3以下でかつ前記圧延終了温度より低
い温度からＡｒ1より高い温度範囲内においてＴ1＞Ｔ2
なる２つの任意の温度を設定し、前記Ｔ1まで冷却速度
４０℃／ｓ以上で冷却し、続けて冷却速度４０℃／ｓ未
満で前記Ｔ2まで冷却し、さらに続けて冷却速度４０℃
／ｓ以上で冷却して３５０〜５００℃で巻取り、ポリゴ
ナルフェライト占積率ＶPF（％）とポリゴナルフェライ
ト平均粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でかつ
残留オーステナイトを体積比で５％以上含むフェライ
ト、ベイナイト及び残留オーステナイトの組織とするこ
とを特徴とする材質バラツキの小さい加工性に優れた熱
延高強度鋼板の製造方法。(9) The steel having the chemical composition described in the above (3) is subjected to hot finish rolling at a total draft of 80% or more, and the rolling end temperature is Ar 3 -50 ° C. to Ar 3 + 50 ° C. Then, T 1 > T 2 in a temperature range from a temperature lower than Ar 3 of the steel and lower than the rolling end temperature to a temperature higher than Ar 1.
The following two arbitrary temperatures are set, cooling is performed at a cooling rate of 40 ° C./s or more to T 1 , continuously cooling to T 2 at a cooling rate of less than 40 ° C./s, and continuously cooling at 40 ° C.
Cooling at 350/500 ° C. and winding at 350 to 500 ° C., and the ratio V PF / d PF of the polygonal ferrite space factor V PF (%) to the average particle size of the polygonal ferrite d PF (μm) is 7 or more and A method for producing a hot-rolled high-strength steel sheet having small workability and excellent workability, characterized by having a structure of ferrite, bainite and retained austenite containing 5% or more by volume of retained austenite.
【００１８】（１０） 前記（３）項に記載の化学成分
の鋼を、全圧下率８０％以上の熱間仕上圧延を行い、そ
の圧延終了温度をＡｒ3＋５０℃超とし、続いて前記鋼
のＡｒ3からＡｒ1超までの温度範囲内において、Ｔ1＞
Ｔ2なる２つの任意の温度を設定し、前記Ｔ1まで冷却速
度４０℃／ｓ以上で冷却し、続けて冷却速度４０℃／ｓ
未満で前記Ｔ2まで冷却し、さらに続けて冷却速度４０
℃／ｓ以上で冷却して３５０〜５００℃で巻取り、ポリ
ゴナルフェライト占積率ＶPF（％）とポリゴナルフェラ
イト平均粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でか
つ残留オーステナイトを体積比で５％以上含むフェライ
ト、ベイナイト及び残留オーステナイトの組織から構成
され、強度−延性バランスＴＳ×Ｔ．Ｅｌが２００００
（ＭＰａ・％）以上でかつ、そのコイル内変動が３００
０（ＭＰａ・％）未満であることを特徴とする材質バラ
ツキの小さい加工性に優れた熱延高強度鋼板の製造方
法。(10) The steel having the chemical composition described in the above item (3) is subjected to hot finish rolling at a total draft of 80% or more, and the rolling end temperature is set to more than Ar 3 + 50 ° C. Within the temperature range from Ar 3 to more than Ar 1 , T 1 >
Set T 2 consists of two arbitrary temperature, the cooling at a cooling rate 40 ° C. / s or higher to T 1, followed by a cooling rate 40 ° C. / s
The cooling to T 2 is less than the cooling rate 40 continues further
After cooling at 350 ° C./s or more and winding at 350 to 500 ° C., when the ratio V PF / d PF of the polygonal ferrite space factor V PF (%) to the average particle size d PF (μm) of the polygonal ferrite is 7 or more, And a structure of ferrite, bainite and retained austenite containing 5% or more by volume of retained austenite, and has a strength-ductility balance TS × T. El is 20000
(MPa.%) Or more and the variation in the coil is 300
A method for producing a hot-rolled high-strength steel sheet which is less than 0 (MPa ·%) and has excellent workability with small material variation.
【００１９】（１１） 熱間仕上圧延開始温度をＡｒ3
＋１００℃以下とすることを特徴とする前記（６）及び
（８）乃至（１０）項の内の何れか１つに記載の材質バ
ラツキの小さい加工性に優れた熱延高強度鋼板の製造方
法。(11) The hot finish rolling start temperature is set to Ar 3
The method for producing a hot-rolled high-strength steel sheet excellent in workability with small material variation according to any one of the above (6) and (8) to (10), wherein the temperature is set to + 100 ° C. or lower. .
【００２０】（１２） 熱間仕上圧延後の巻取り後の鋼
板を３０℃／ｈｒ以上の冷却速度で２００℃以下まで冷
却することを特徴とする前記（６）及び（８）乃至（１
１）項の内の何れか１つに記載の材質バラツキの小さい
加工性に優れた熱延高強度鋼板の製造方法。(12) The above (6) and (8) to (1), wherein the rolled steel sheet after hot finish rolling is cooled to 200 ° C. or less at a cooling rate of 30 ° C./hr or more.
(1) The method for producing a hot-rolled high-strength steel sheet according to any one of (1) and having excellent workability with small material variation.
【００２１】（１３） 前記（４）項に記載の化学成分
の鋼を、仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０
℃、全圧下率８０％以上で熱間圧延を行い、該圧延に続
いて該温度Ｔ11から４０℃／秒以上の冷却速度で冷却
し、５００℃以下３５０℃超で巻取って後放冷する事を
特徴とする材質バラツキの小さい加工性とスポット溶接
性に優れた熱延高強度鋼板の製造方法。(13) The steel having the chemical composition described in the above (4) is subjected to finish rolling end temperature Ar 3 -50 ° C. to Ar 3 +50.
Hot rolling at 80 ° C. and a total draft of 80% or more, and after the rolling, cooling at a cooling rate of 40 ° C./sec or more from the temperature T 11 , winding at 500 ° C. or more and over 350 ° C., and then cooling A method for producing a hot-rolled high-strength steel sheet having excellent workability with small material variations and excellent spot weldability.
【００２２】（１４） 前記（４）項に記載の化学成分
の鋼を、圧下率８０％以上で熱間圧延し、Ａｒ3−５０
℃以上で終了した該圧延に続いて該温度Ｔ21から４０℃
／秒未満の降温速度で３〜２５秒保定後、Ａｒ1超の温
度範囲内の温度Ｔ22から４０℃／秒以上の冷却速度で冷
却し、５００℃以下３５０℃超で巻取って後放冷する事
を特徴とする材質バラツキの小さい加工性とスポット溶
接性に優れた熱延高強度鋼板の製造方法。[0022] (14) (4) above the steel chemical composition according to claim, hot rolled at a reduction ratio of 80% or more, Ar 3 -50
The temperature T 21 to 40 ° C. following the rolling finished above
/ Sec less cooling rate at 3-25 Byohojogo, cooled at a cooling rate from the temperature T 22 of 40 ° C. / sec or more within a temperature range of Ar 1 greater, release post wound up at 500 ° C. or less 350 ° C. greater A method for producing a hot-rolled high-strength steel sheet that is characterized by cooling and has excellent workability with small material variations and excellent spot weldability.
【００２３】（１５） 前記（４）項に記載の化学成分
の鋼を、圧下率８０％以上で熱間圧延し、Ａｒ3−５０
℃以上で該圧延を終了し、続いて該温度Ｔ31から冷却速
度４０℃／秒以上でＴ32（Ａｒ3＞Ｔ32＞Ａｒ1）温度ま
で冷却し、続いて４０℃／秒未満の降温速度でＴ33（Ａ
ｒ3＞Ｔ32≧Ｔ33＞Ａｒ1）まで３〜２５秒保定後、冷却
速度４０℃／秒以上で冷却し、５００℃以下３５０℃超
で巻取って後放冷する事を特徴とする材質バラツキの小
さい加工性とスポット溶接性に優れた熱延高強度鋼板の
製造方法。(15) The steel having the chemical composition described in the above (4) is hot-rolled at a rolling reduction of 80% or more, and Ar 3 -50
The rolling is completed at a temperature of not lower than 40 ° C./sec, and then cooled from the temperature T 31 to a temperature of T 32 (Ar 3 > T 32 > Ar 1 ) at a cooling rate of 40 ° C./sec or more, and subsequently, a temperature drop of less than 40 ° C./sec. At speed T 33 (A
After holding for 3 to 25 seconds until r 3 > T 32 ≧ T 33 > Ar 1 ), cool at a cooling rate of 40 ° C./sec or more, wind up at 500 ° C. or more and over 350 ° C., and then let cool down. A method for manufacturing hot-rolled high-strength steel sheets with excellent workability and spot weldability with small material variations.
【００２４】（１６） 熱間仕上圧延前の加熱温度を１
１７０℃以下とすることを特徴とする前記（１３）乃至
（１５）項の内の何れか１つに記載の材質バラツキの小
さい加工性とスポット溶接性に優れた熱延高強度鋼板の
製造方法。(16) The heating temperature before hot finish rolling is 1
The method for producing a hot-rolled high-strength steel sheet according to any one of the above items (13) to (15), which is characterized in that the temperature is 170 ° C. or lower, and the material has small workability and excellent spot weldability. .
【００２５】（１７） 熱間仕上圧延開始温度をＡｒ3
＋１００℃以下とすることを特徴とする前記（１３）乃
至（１６）項の内の何れか１つに記載の材質バラツキの
小さい加工性とスポット溶接性に優れた熱延高強度鋼板
の製造方法。(17) The hot finish rolling start temperature is set to Ar 3
The method for producing a hot-rolled high-strength steel sheet according to any one of the above (13) to (16), which has a small workability and excellent spot weldability, wherein the temperature is + 100 ° C. or lower. .
【００２６】（１８） 熱間仕上圧延後の巻き取り後の
鋼板を３０℃／ｈｒ以上の冷却速度で２００℃以下まで
冷却して後放冷することを特徴とする前記（１３）乃至
（１７）項の内の何れか１つに記載の材質バラツキの小
さい加工性とスポット溶接性に優れた熱延高強度鋼板の
製造方法。(18) The above-mentioned (13) to (17), wherein the rolled steel sheet after hot finish rolling is cooled to 200 ° C. or less at a cooling rate of 30 ° C./hr or more, and then left to cool. The method for producing a hot-rolled high-strength steel sheet according to any one of the above items, which is excellent in workability with small material variation and excellent spot weldability.
【００２７】（１９） 熱間仕上圧延前の加熱温度を１
１７０℃以下とし、熱間仕上圧延開始温度をＡｒ3＋１
００℃以下とし、さらに前記熱間仕上圧延後の巻き取り
後の鋼板を３０℃／ｈｒ以上の冷却速度で２００℃以下
まで冷却することを特徴とする前記（１３）乃至（１
５）項の内の何れか１つに記載の材質バラツキの小さい
加工性とスポット溶接性に優れた熱延高強度鋼板の製造
方法。(19) The heating temperature before hot finish rolling is 1
170 ° C. or lower and the hot finish rolling start temperature is Ar 3 +1
(13) to (1), wherein the rolled steel sheet after the hot finish rolling is cooled to 200 ° C. or less at a cooling rate of 30 ° C./hr or more.
5) The method for producing a hot-rolled high-strength steel sheet according to any one of the items 5), which is excellent in workability with small material variation and excellent spot weldability.
【００２８】（２０） 鋼が化学成分として、さらに、
Ｃｕ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｃａ、ＲＥ
Ｍの１種又は２種以上を含有し、重量％で、その内Ｃ
ｕ、Ｎｉ、Ｃｒ、Ｍｏにおいては、それらの１種又は２
種以上を合計で０．５％以下、Ｎｂ、Ｔｉ、Ｖにおいて
は、それらの１種又は２種以上を合計量で０．３％以
下、Ｃａにおいては０．０１％以下、ＲＥＭにおいては
０．０５％以下であることを特徴とする前記（６）乃至
（１９）項の内の何れか１つに記載の熱延高強度鋼板の
製造方法。(20) Steel is a chemical component.
Cu, Ni, Cr, Mo, Nb, Ti, V, Ca, RE
M, containing one or more kinds thereof, and in% by weight thereof,
In u, Ni, Cr, Mo, one or two of them
0.5% or less in total for Nb, Ti and V, 0.3% or less in total for one or more of them, 0.01% or less for Ca, and 0% for REM The method for producing a hot-rolled high-strength steel sheet according to any one of the above (6) to (19), wherein the content is 0.05% or less.
【００２９】なお、Ｂの上限を規定することによる鋼材
特性に及ぼす影響としては、特開平８−１５８００５号
公報に述べられているように耐亜鉛めっき割れ性の改善
に関わる技術が知られているものの材質ばらつきに関わ
る技術ではない。As for the effect on the steel material properties by defining the upper limit of B, there is known a technique relating to improvement of galvanizing crack resistance as described in JP-A-8-158005. It is not a technology related to material variations.
【００３０】[0030]
【発明の実施の形態】以下に本発明を詳細に説明する。
まず、鋼の化学成分を規定した理由について説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the reason for defining the chemical composition of steel will be described.
【００３１】Ｃは鋼の強化に不可欠な元素であり、０．
０５％（ｗｔ％以下同じ）未満では本発明鋼の延性を向
上させている残留オーステナイトが充分に得られない。
また、０．４％超では溶接性を劣化させ、鋼を脆化させ
る。そこでＣ含有量を０．０５％〜０．４％としたが、
０．１５〜０．３％とすることが好ましい。また、良好
なスポット溶接性を得るためには、Ｃ含有量は０．０５
〜０．１５％未満が適する。C is an element indispensable for strengthening steel.
If it is less than 05% (same as wt% or less), sufficient austenite which improves the ductility of the steel of the present invention cannot be obtained.
On the other hand, if it exceeds 0.4%, the weldability deteriorates and the steel becomes brittle. Therefore, the C content is set to 0.05% to 0.4%.
It is preferable to be 0.15 to 0.3%. Further, in order to obtain good spot weldability, the C content is 0.05%.
~ 0.15% is suitable.
【００３２】Ｓｉは、その含有量の増加により延性向上
に寄与するフェライトの生成、純化に有利であり、ま
た、Ｃを未変態オーステナイト中へ濃化させて、残留オ
ーステナイトを得るのに有利となる。この効果は、０．
５％未満では充分発揮されず、また、３．０％を超える
と、効果は飽和し、かえってスケール性状、溶接性を劣
化させる。そこで０．５〜３．０％としたが、スポット
溶接性の悪化防止のためには０．５〜２．５％とするこ
とが好ましい。[0032] Si is advantageous for the generation and purification of ferrite which contributes to the improvement of ductility by increasing its content, and is also advantageous for concentrating C in untransformed austenite to obtain retained austenite. . This effect is 0.
If it is less than 5%, it will not be sufficiently exhibited, and if it exceeds 3.0%, the effect will be saturated and the scale properties and weldability will be rather deteriorated. Therefore, the content is set to 0.5 to 3.0%, but is preferably set to 0.5 to 2.5% to prevent deterioration of spot weldability.
【００３３】Ｍｎはよく知られている通りオーステナイ
トの安定化元素としてオーステナイトの残留に寄与す
る。その効果は０．５％未満では充分に発揮されず、ま
た３％を超えるとその効果は飽和し、かえって溶接性の
劣化等の悪い影響を発生する。そこで０．５％〜３．０
％としたが、良好なスポット溶接性の悪化防止のために
は０．５〜２．５％とすることが好ましい。As is well known, Mn contributes to austenite retention as an austenite stabilizing element. If the effect is less than 0.5%, the effect is not sufficiently exhibited, and if it exceeds 3%, the effect is saturated, and adverse effects such as deterioration of weldability are generated. Therefore, 0.5% to 3.0%
%, But preferably 0.5 to 2.5% in order to prevent deterioration of spot weldability.
【００３４】Ｐは高強度化に有効な元素であるが効果と
コストのかねあいから０．１％以下とする。しかし、２
次加工性、靭性、特にスポット溶接性の確保のために
は、０．０２％以下とする。P is an element effective for increasing the strength, but is set to 0.1% or less from the viewpoint of effect and cost. However, 2
In order to ensure secondary workability and toughness, particularly spot weldability, the content is made 0.02% or less.
【００３５】ＳはＭｎＳ系介在物の生成を少くし、穴拡
げ性向上を図るため０．０５％以下としたが、０．００
５％以下とすることが好ましい。S is set to 0.05% or less in order to reduce generation of MnS-based inclusions and improve hole expandability.
It is preferable that the content be 5% or less.
【００３６】Ａｌは脱酸元素であると共にフェライト強
化作用があり高強度化に寄与するが効果とコストのかね
あいから０．１％以下としたが、０．００５〜０．１％
とすることが好ましい。Al is a deoxidizing element and also has a ferrite strengthening action and contributes to high strength. However, from the viewpoint of effect and cost, the content is set to 0.1% or less.
It is preferable that
【００３７】Ｎも高強度化に寄与するが効果とコストの
かねあいから必要に応じて０．１％以下含有させる。N also contributes to an increase in strength, but it is contained in an amount of 0.1% or less as necessary from the viewpoint of effect and cost.
【００３８】不純物としてのＢはフェライト変態を安定
的に進行させ、フェライト占積率やその粒径の変動を抑
制し、その他添加元素等限定の作用とあいまって、成形
性指標である強度延性バランスの高レベル維持とそのば
らつき低減のため、その上限を０．０００５％、好まし
くは０．０００２％とする。B as an impurity stably promotes ferrite transformation, suppresses fluctuations in the ferrite space factor and its grain size, and, together with the effect of limiting the addition of other elements, etc., shows the strength-ductility balance as an index of formability. In order to maintain a high level and reduce the variation, the upper limit is made 0.0005%, preferably 0.0002%.
【００３９】さらに選択元素としてＣｕ、Ｎｉ、Ｃｒ、
Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｃａ、ＲＥＭの１種又は２種以
上を添加してもよい。Further, Cu, Ni, Cr,
One or more of Mo, Nb, Ti, V, Ca, and REM may be added.
【００４０】この際、Ｃｕ、Ｎｉ、Ｃｒ、Ｍｏは高強度
化に有効な元素であるが効果とコストのかねあいから、
それらの添加量は、１種又は２種以上を合計で０．５％
以下とする。At this time, Cu, Ni, Cr and Mo are effective elements for increasing the strength, but from the viewpoint of effect and cost,
Their addition amount is 0.5% in total of one or more.
The following is assumed.
【００４１】Ｎｂ、Ｔｉ、Ｖも同様の理由で１種又は２
種以上の添加量を合計で０．３％以下とする。Nb, Ti, and V may be of one type or two for the same reason.
The total amount of the seeds is set to 0.3% or less.
【００４２】Ｃａは硫化物系介在物の形態制御（球状
化）により、加工性（特に穴拡げ比）をより向上させる
ために０．０１％以下添加してもよい。また、ＲＥＭも
同様の理由から０．０５％以下添加してもよい。Ca may be added in an amount of 0.01% or less in order to further improve the workability (particularly the hole expansion ratio) by controlling the form of the sulfide-based inclusions (spheroidizing). Also, REM may be added at 0.05% or less for the same reason.
【００４３】次に本発明の組織上の制限とその理由を説
明する。後述する実施例における表１中のＡ鋼をベース
にして、前記の課題を解決するための手段としての各種
製造方法及びその製造条件の付近で製造された鋼板を整
理、検討した結果、次のことを確認した。製造条件とし
ては表１中のＡ鋼を用い、全圧下率８０〜９０％、圧延
終了温度を７５０〜８５０℃とし、該温度より２０〜３
５℃／ｓの冷却速度で６６０〜７２０℃まで冷却した
後、続けて４５〜８０℃／ｓの冷却して３５０〜５００
℃冷却速度で巻き取った。Next, the organizational restrictions of the present invention and the reasons therefor will be described. As a result of organizing and examining various manufacturing methods as means for solving the above-described problems and steel sheets manufactured in the vicinity of the manufacturing conditions based on the steel A in Table 1 in Examples described later, the following results were obtained. It was confirmed. As the production conditions, steel A in Table 1 was used, the total rolling reduction was 80 to 90%, the rolling end temperature was 750 to 850 ° C, and the temperature was 20 to 3 from this temperature.
After cooling to 660 to 720 ° C. at a cooling rate of 5 ° C./s, subsequently cooling to 45 to 80 ° C./s to 350 to 500
Winded at a cooling rate of ° C.
【００４４】図１は前記製造条件で製造した鋼板の強度
−延性バランスＴＳ×Ｔ．Ｅｌと残留オーステナイトの
特性を調査した結果を示している。図１から残留オース
テナイトの占積率が５％以上でＴＳ×Ｔ．Ｅｌで２００
００（ＭＰａ・％）が得られることから、オーステナイ
トがＣ等の元素の濃化により安定化されることが望まれ
る。このためにはフェライトを生成させることにより
オーステナイト中へのＣ等の元素の濃化を促進させ、オ
ーステナイトの残留に寄与せしめること、ベイナイト
変態の進行に伴い、オーステナイト中へのＣ等の元素の
濃化を促進させ、オーステナイトの残留に寄与せしめる
ことが必要である。FIG. 1 shows the strength-ductility balance TS × T. The result of having investigated the characteristic of El and retained austenite is shown. From FIG. 1, TS × T. 200 in El
Since 00 (MPa ·%) is obtained, it is desired that austenite is stabilized by concentration of elements such as C. For this purpose, the concentration of elements such as C in austenite is promoted by generating ferrite to contribute to the retention of austenite, and with the progress of bainite transformation, the concentration of elements such as C in austenite is increased. It is necessary to promote the formation of carbon and contribute to the retention of austenite.
【００４５】フェライトの生成によりオーステナイト中
へのＣ等の元素の濃化を促進させ、オーステナイトの残
留に寄与せしめようとする場合、フェライト占積率を増
加させ、フェライト粒を微細化することが必要である。
なぜならばＣ濃度が最も高く、オーステナイトとして残
留しやすい箇所はフェライトと未変態オーステナイトの
界面であり、その界面はフェライト占積率の増加とフェ
ライト粒の微細化により増加するからである。In order to promote the enrichment of elements such as C in austenite by producing ferrite and to contribute to the retention of austenite, it is necessary to increase the space factor of ferrite and to refine ferrite grains. It is.
This is because the portion where the C concentration is the highest and which is likely to remain as austenite is the interface between ferrite and untransformed austenite, and the interface increases due to an increase in the ferrite space factor and the refinement of ferrite grains.
【００４６】図１と同じ条件の実験結果を整理した図２
に示すように少なくともＴＳ×Ｔ．Ｅｌ≧２００００
（ＭＰａ・％）を確実に得るにはポリゴナルフェライト
占積率（ＶPF）％とポリゴナルフェライト粒径（ｄPF）
μｍの比ＶPF／ｄPFを７以上とすればよいことを見い出
した。（ポリゴナルフェライトの占積率及び平均粒径は
光学顕微鏡写真にて測定を行う。なおポリゴナルフェラ
イトとはフェライトの内で軸比（長軸／短軸）＝１〜３
のものと定義する。）FIG. 2 in which the experimental results under the same conditions as in FIG. 1 are arranged.
As shown in FIG. El ≧ 20,000
(MPa ·%) to obtain polygonal ferrite space factor (V PF )% and polygonal ferrite particle size (d PF )
It has been found that the ratio V PF / d PF of μm should be 7 or more. (The space factor and average particle size of polygonal ferrite are measured by an optical microscope photograph. Polygonal ferrite is an axis ratio (long axis / short axis) of ferrite = 1 to 3
Is defined as )
【００４７】フェライト、残留オーステナイト以外の残
部組織はオーステナイト中へのＣ等の濃化に寄与するベ
イナイトとし（ベイナイト変態の進行により未変態オー
ステナイトへＣが濃化し、オーステナイトを安定化し、
オーステナイトの残留に好ましい効果を発揮する。）、
残留オーステナイト量を減少させるパーライト、マルテ
ンサイトを生成させないことが必要である。The remaining structure other than the ferrite and the retained austenite is bainite which contributes to the enrichment of C and the like in the austenite.
It exerts a favorable effect on austenite retention. ),
It is necessary not to generate pearlite and martensite which reduce the amount of retained austenite.
【００４８】次に本発明の製造工程上の制限とその理由
について説明する。Next, the limitations on the manufacturing process of the present invention and the reasons therefor will be described.
【００４９】フェライト占積率を増加させる（即ちＶPF
を大きくする）製造技術としては低温圧延、高圧下圧
延、仕上圧延後の冷却テーブル上におけるフェライト変
態のノーズ温度付近（Ａｒ1超〜Ａｒ3）での徐冷（フェ
ライト変態のノーズ温度とは恒温フェライト変態が最小
時間で開始、終了する温度）が有効である。The ferrite space factor is increased (ie, V PF
The increase) the low temperature rolling as a manufacturing technique, under high pressure rolling and the nose temperature annealing (ferrite transformation in the vicinity nose temperature of ferrite transformation on the finish rolling after the cooling table (Ar 1 super to Ar 3) isothermal The temperature at which ferrite transformation starts and ends in a minimum time) is effective.
【００５０】フェライトを細粒化する（即ち、ｄPFを小
さくする）製造技術としては低温圧延、高圧下圧延、Ａ
ｒ3変態点近傍での急冷、フェライト変態後の急冷（粒
成長を避けるために）が有効である。Manufacturing techniques for refining ferrite (ie, reducing dPF ) include low-temperature rolling, high-pressure rolling, and A
Quenching near the r 3 transformation point and quenching after ferrite transformation (to avoid grain growth) are effective.
【００５１】従って、上記の前者の各手段及び後者のそ
れを組み合わせた製造方法が考えられる。Therefore, a manufacturing method combining the former means and the latter means can be considered.
【００５２】圧延温度：フェライト占積率を増加し、フ
ェライトを細粒化するためには低温圧延が有効である。
ただし、Ａｒ3−５０℃より低い温度では加工フェライ
トが増加し、延性を害する。また、Ａｒ3＋５０℃より
高い温度（実質的には８５０℃超の温度）ではフェライ
トが充分生成しない。従ってＡｒ3−５０℃〜Ａｒ3＋５
０℃が仕上圧延終了温度としては有効である。さらに仕
上圧延開始温度をＡｒ 3＋１００℃以下とすることによ
り、組織を微細化し、延性向上に有利なフェライトを生
成させ、オーステナイト中へＣ等の元素の濃化を促進さ
せ、オーステナイトの残留に寄与する効果は一層高ま
る。Rolling temperature: The ferrite space factor is increased
Low-temperature rolling is effective for refining ferrite.
Where ArThreeAt temperatures lower than -50 ° C,
Increase the ductility and impair ductility. Also, ArThreeFrom + 50 ° C
At high temperatures (essentially above 850 ° C)
Does not generate enough. Therefore ArThree-50 ° C to ArThree+5
0 ° C. is effective as the finish rolling end temperature. Further
Upper rolling start temperature is Ar ThreeBy keeping the temperature below + 100 ° C
Ferrite, which refines the structure and improves ductility.
Promotes the concentration of elements such as C into austenite
The effect of contributing to retained austenite
You.
【００５３】ただし、低温圧延は、薄物圧延（板厚≦２
mm）時、特に変形抵抗の高い高カーボン当量材もしくは
高合金材の圧延時には、圧延荷重の増大、形状確保の困
難等の操業上好ましからざる点がある。従って後述する
熱間仕上圧延後の冷却テーブル上での冷却をコントロー
ルすることによってフェライトの生成及び微細化を図る
ことも有効である。またその場合、Ａｒ3＋５０℃超の
熱間仕上圧延終了温度とすることは前記効果を高めはし
ないが、操業上、採用せざるを得ないことが多い。However, low-temperature rolling is a thin rolling (sheet thickness ≦ 2).
mm), especially when rolling a high carbon equivalent material or a high alloy material having a high deformation resistance, there are points that are not preferable in operation, such as an increase in rolling load and difficulty in securing the shape. Therefore, it is also effective to control the cooling on the cooling table after the hot finish rolling to be described later to produce ferrite and reduce the size of the ferrite. In this case, setting the hot finish rolling end temperature to a temperature exceeding Ar 3 + 50 ° C. does not enhance the above effect, but it is often unavoidable in operation.
【００５４】圧下率：熱間仕上圧延における合計圧下率
を８０％以上とするとフェライトの生成、微細化が促進
され、良好な材質が得られるため、下限を８０％以上と
した。Reduction rate: When the total reduction rate in hot finish rolling is set to 80% or more, the formation and miniaturization of ferrite are promoted, and a good material is obtained. Therefore, the lower limit is set to 80% or more.
【００５５】冷却：冷却速度は、オーステナイトの残留
に不利となるパーライトの生成を避け、組織の微細化を
助けるという点から４０℃／ｓ以上とする。しかし、特
に、熱間圧延後、Ａｒ3〜Ａｒ1超を４０℃／ｓ以上の冷
却速度で冷却してはオーステナイトの残留に必要なフェ
ライトの生成とＣ濃化が充分に進行しないため、図３に
示すような温度パターンに沿って、圧延後、Ｔ（Ａｒ1
＜Ｔ≦Ａｒ3）まで冷却速度４０℃／ｓ未満で冷却する
ことが望ましい。あるいは、さらに望ましい冷却方法と
して図４に示すパターンがあり、圧延後Ｔ1（Ａｒ1＜Ｔ
≦Ａｒ3かつＡｒ1＜Ｔ1＜圧延終了温度）まで冷却速度
４０℃／ｓ以上で冷却してフェライト変態により生成し
たフェライトの微細化と圧延中に生成したフェライトも
含めて粒成長の抑制を図り、さらに続いてＴ2（Ａｒ1＜
Ｔ2＜Ｔ1）まで冷却速度４０℃／ｓ未満で冷却すること
によりフェライト変態ノーズ付近でフェライト占積率を
増加させ、より良好な材質が得られる。Cooling: The cooling rate is set to 40 ° C./s or more from the viewpoint of avoiding the generation of pearlite which is disadvantageous for the austenite retention and assisting the micronization of the structure. However, in particular, after hot rolling, if Ar 3 to Ar 1 is cooled at a cooling rate of 40 ° C./s or more, ferrite formation and C enrichment required for austenite retention do not sufficiently proceed. After rolling along a temperature pattern as shown in FIG. 3, T (Ar 1
It is desirable to cool at a cooling rate of less than 40 ° C./s until <T ≦ Ar 3 ). Alternatively, as a more desirable cooling method, there is a pattern shown in FIG. 4, and after rolling, T 1 (Ar 1 <T 1)
≦ Ar 3 and Ar 1 <T 1 <rolling end temperature> Cool at a cooling rate of 40 ° C./s or more to reduce the size of ferrite formed by ferrite transformation and the suppression of grain growth including ferrite generated during rolling. And then T 2 (Ar 1 <
By cooling at a cooling rate of less than 40 ° C./s until T 2 <T 1 ), the ferrite space factor is increased near the ferrite transformation nose, and a better material can be obtained.
【００５６】Ａｒ3を超える温度では冷却速度４０℃／
ｓ未満で冷却してもフェライトは生成せず、Ａｒ1以下
の温度まで冷却速度４０℃／ｓ未満で冷却するとパーラ
イトを生成するため、Ａｒ1＜Ｔ≦Ａｒ3、Ａｒ1＜Ｔ2＜
Ｔ1≦Ａｒ3とする。At a temperature exceeding Ar 3 , the cooling rate is 40 ° C. /
Ferrite is not formed even when cooled at less than s, and pearlite is formed when cooled at a cooling rate of less than 40 ° C./s to a temperature of Ar 1 or less, so that Ar 1 <T ≦ Ar 3 , Ar 1 <T 2 <
It is assumed that T 1 ≦ Ar 3 .
【００５７】その後の巻取温度までの冷却速度はパーラ
イトの生成を避け、組織の微細化を助けるという観点か
ら４０℃／ｓ以上とする。The cooling rate to the subsequent winding temperature is set to 40 ° C./s or more from the viewpoint of avoiding the generation of pearlite and assisting the micronization of the structure.
【００５８】図１と同じ条件で圧延し、冷却した後、巻
取温度を変えて実験した結果を図５、図６に示す。After rolling under the same conditions as in FIG. 1, cooling, and changing the winding temperature, the results of experiments are shown in FIGS. 5 and 6.
【００５９】巻取温度は５００℃を超えると巻取り後ベ
イナイト変態が過度に進行し、あるいはパーライトが生
成し、図５に示す如く体積比で５％以上の残留オーステ
ナイトが得られなくなるため上限を５００℃以下とす
る。また、３５０℃未満では図６に示す如く、Ｃが０．
１５％以上の中炭素鋼では、マルテンサイトが生成し穴
拡げ性が劣化するため、下限を３５０℃以上とする。If the winding temperature exceeds 500 ° C., bainite transformation proceeds excessively after winding or pearlite is formed, and as shown in FIG. 5, residual austenite with a volume ratio of 5% or more cannot be obtained. 500 ° C. or less. When the temperature is lower than 350 ° C., as shown in FIG.
In a medium carbon steel of 15% or more, since the martensite is generated and the hole expandability deteriorates, the lower limit is set to 350 ° C. or more.
【００６０】また、過度のベイナイト変態を避けより多
量のオーステナイトを残留させるため図５に示す如く、
巻取り後、水中浸漬、ミスト噴霧等により３０℃／ｈｒ
以上の冷却速度で２００℃以下まで冷却することがより
有効である。Further, in order to avoid excessive bainite transformation and to leave a larger amount of austenite, as shown in FIG.
After winding, immersion in water, mist spraying, etc. at 30 ° C / hr
It is more effective to cool to 200 ° C. or lower at the above cooling rate.
【００６１】以上の各製造技術の組み合わせた技術とし
て図３及び図４に集約される。そして、仕上圧延終了温
度が低温範囲（Ａｒ3±５０℃）のものと高温範囲（Ａ
ｒ3＋５０℃超）のものの２種類がある。さらに、上記
４種類の製造方法に、熱間仕上圧延開始温度の上限をＡ
ｒ3＋１００℃以下と規制したもの、又は巻取り後の冷
却方法を規制したものの片方あるいは両方を組み合わせ
た製造方法がある。その組み合わせを重ねる程、効果も
大きくなることは当然である。FIGS. 3 and 4 show a combination of the above-described manufacturing techniques. The finish rolling finish temperature is in a low temperature range (Ar 3 ± 50 ° C.) and a high temperature range (A
r 3 + 50 ° C.). Further, the upper limit of the hot finish rolling start temperature is set to A in the above four types of manufacturing methods.
There is a manufacturing method in which one or both of those regulated to be r 3 + 100 ° C. or less and those regulated for the cooling method after winding are combined. It goes without saying that the effect increases as the combination increases.
【００６２】次に高穴拡げ性を低下させることなくスポ
ット溶接性を向上させた熱延高強度鋼板の製造方法につ
いて述べる。Next, a method for producing a hot-rolled high-strength steel sheet having improved spot weldability without deteriorating high hole expandability will be described.
【００６３】加熱温度はオーステナイト（γ）の細粒化
を経たフェライト（α）の細粒化と最良な表面性状の確
保のめに上限をもうけている。The upper limit of the heating temperature is set in order to reduce the grain size of ferrite (α) after austenite (γ) is reduced and to secure the best surface properties.
【００６４】仕上圧延の開始温度は、α占積率の増加と
α粒径の細粒化により、残留γをより増加させる効果を
維持するために上限をもうけている。The upper limit of the starting temperature of the finish rolling is set to maintain the effect of further increasing the residual γ by increasing the α space factor and refining the α grain size.
【００６５】仕上圧延の終了温度は、仕上圧延の開始温
度と同様の理由から規制しているが、加工組織による延
性劣化の防止から下限をもうけている。The end temperature of the finish rolling is regulated for the same reason as the start temperature of the finish rolling, but a lower limit is set in order to prevent ductility deterioration due to the working structure.
【００６６】圧下率はα占積率の増大、αの細粒化によ
る残留γの確保のため下限をもうけている。これらの熱
間圧延の条件は前述した通りである。The rolling reduction has a lower limit in order to increase the α space factor and to secure the residual γ by reducing α. The conditions for these hot rolling are as described above.
【００６７】冷却条件については、図７に示す１段冷却
の冷却速度はパーライトの生成防止のために下限を定め
ている。Regarding the cooling conditions, the lower limit of the cooling rate of the single-stage cooling shown in FIG. 7 is set in order to prevent the generation of pearlite.
【００６８】図７に示す２段冷却の初段の降温速度はα
占積率の確保のため上限を定め、２段目の冷却速度はパ
ーライトの生成防止のため下限を定め、保定時間は上記
した初段の作用が充分に達成される時間に規制してい
る。The temperature drop rate of the first stage of the two-stage cooling shown in FIG.
An upper limit is set for securing the space factor, and a lower limit is set for the cooling rate of the second stage to prevent generation of pearlite, and the holding time is regulated to a time at which the above-described operation of the first stage is sufficiently achieved.
【００６９】図７に示す３段冷却の初段の冷却速度はα
の細粒化のため下限を、２段目の降温速度はαの占積率
の確保のため上限を、３段目の冷却速度はパーライトの
生成防止のため下限を定め、保定時間は上記した２段目
の作用が充分に達成される時間に規制している。The cooling rate at the first stage of the three-stage cooling shown in FIG.
The lower limit is set for grain refinement, the upper limit is set for the cooling rate of the second stage, the upper limit is set for securing the space factor of α, and the lower limit is set for the cooling speed of the third stage to prevent pearlite generation. The time is regulated so that the second-stage action can be sufficiently achieved.
【００７０】巻取温度の下限はマルテンサイトの生成を
防止して残留γを確保し、併せて穴拡げ性の劣化を防止
するため定め、上限はパーライトの生成を防止して残留
γを確保し、併せて過度のベイナイト変態を抑制し、残
留γを確保するため定めている。The lower limit of the winding temperature is determined to prevent the formation of martensite and secure the residual γ, and also to prevent the deterioration of the hole expandability. The upper limit is set to prevent the generation of pearlite and secure the residual γ. In addition, it is determined to suppress excessive bainite transformation and secure residual γ.
【００７１】また巻取り後の強制冷却は過度のベイナイ
ト変態を抑制して残留γを確保するため、強制冷却終了
温度の下限と冷却速度の上限を定めている。In the forced cooling after winding, the lower limit of the forced cooling end temperature and the upper limit of the cooling rate are determined in order to suppress the excessive bainite transformation and secure the residual γ.
【００７２】本発明者等は特開昭６４−７９３４５号公
報で、優れた強度・延性バランスを有する、「加工性に
優れた高強度熱延鋼板」と「その製造方法」を提案し
た。該提案は前記した特開昭６０−４３４２５号公報と
同様に、残留γのＴＲＩＰ現象を利用したもので、α占
積率／α粒径を７以上とし、残留γを占積率５％以上確
保し、ＴＳ×Ｔ．Ｅｌ≧２００００を達成している。The present inventors have proposed in JP-A-64-79345, "a high-strength hot-rolled steel sheet excellent in workability" and "a method for producing the same" having an excellent balance between strength and ductility. This proposal utilizes the TRIP phenomenon of residual γ as in the above-mentioned Japanese Patent Application Laid-Open No. Sho 60-43425, in which α space factor / α particle size is 7 or more and residual γ is 5% or more. Secure, TS × T. El ≧ 20,000 is achieved.
【００７３】この提案は、延性を向上させＴＳ×Ｔ．Ｅ
ｌ≧２００００を得るため占積率５％以上の残留γを必
須とし、これを達成するためγをＣ等の元素の濃化によ
り安定させている。This proposal improves the ductility and improves the TS × T. E
In order to obtain l ≧ 20,000, a residual γ of a space factor of 5% or more is essential, and in order to achieve this, γ is stabilized by enriching elements such as C.
【００７４】そのため該提案は０．１５〜０．４０重量
％のＣを必要としている。The proposal therefore requires 0.15 to 0.40% by weight of C.
【００７５】しかしＣがこの様に高いと前記した様に現
在広く適用を見ているスポット溶接性の劣化を招き、ま
た、本発明の目標でもある穴拡げ比１．４以上の高穴拡
げ性の維持も期待出来ず、幾ら強度・延性バランスが優
れている鋼板であってもユーザーの要望を完全に満たす
に到らず、適用範囲が限られることを本発明者等は見出
した。However, if C is so high, the spot weldability, which is widely used at present, is deteriorated as described above, and the high hole spreadability of 1.4 or more, which is a target of the present invention, is also obtained. The present inventors have found that even if the steel sheet has an excellent balance between strength and ductility, it cannot fully satisfy the user's demand, and its application range is limited.
【００７６】本発明者等はこの事実を基に、種々の実験
検討を重ね、図８〜図１２の知見を得た。Based on this fact, the present inventors have conducted various experimental studies and obtained the findings shown in FIGS.
【００７７】本発明は上記の知見を基に、前記した手段
を構成したので、Ｃを０．０５〜０．１５重量％未満迄
低減しても、強度・延性バランスはもとより高穴拡げ性
の低下をみることなく、スポット溶接性を向上させ、本
発明の課題を達成するに到ったのである。In the present invention, based on the above findings, the above-mentioned means are constituted. Therefore, even if C is reduced to 0.05 to less than 0.15% by weight, not only the balance between strength and ductility but also the high hole expansion property is obtained. The spot weldability was improved without any decrease and the object of the present invention was achieved.
【００７８】以下図８〜図１２を基に本発明者等が得た
知見を説明する。The findings obtained by the present inventors will be described below with reference to FIGS.
【００７９】図８はα占積率／α粒径とＴＳ×Ｔ．Ｅｌ
の関係を示し、図９はＣ重量％とスポット溶接性の関係
を示し、第１０図はＳｉ重量％とＭｎ重量％と残留γ量
の関係を示し、図１１は加熱温度と熱延鋼板の表面性状
の関係を示し、図１２は巻取温度と穴拡げ比の関係を示
す。FIG. 8 shows α space factor / α particle size and TS × T. El
9 shows the relationship between C wt% and spot weldability, FIG. 10 shows the relationship between Si wt%, Mn wt%, and the residual γ content, and FIG. 11 shows the heating temperature and the hot rolled steel sheet. FIG. 12 shows the relationship between the winding temperature and the hole expansion ratio.
【００８０】これ等の図は、ＴＳ×Ｔ．Ｅｌ≧２００
００を確保するために必要な５％以上の残留γを得るに
は、第８図に示す如く、Ｃが０．１５％未満の低炭素鋼
ではＶPF／ｄPF≧２０の確保が必須要件であること、即
ち、０．１５％未満の母材Ｃ濃度で５％以上の残留γを
得るには、前記特開昭６４−７９３４５号公報で開示し
た以上に、さらにα占積率を高めるか、α粒径を微細化
するか、あるいは両者を同時に行うことが必須要件であ
ること、スポット溶接性の向上には、図９に示す如く
Ｃを０．１５％未満に低減することが必須要件であるこ
と、本発明で用いるようにＣの低い鋼種では、ＴＳ×
Ｔ．Ｅｌ≧２００００とスポット溶接性の両立は、図１
０に示すＳｉとＭｎの添加規制範囲の厳守が必須要件で
あること、また特に優れた表面性状を得るには、図１
１に示す如く加熱温度を１１７０℃以下とすることが必
須要件であること、ＴＳ×Ｔ．Ｅｌ≧２００００と並
んで当業分野で重要な加工性指標とされている、穴拡げ
比ｄ／ｄ0が１．４以上の高穴拡げ性を確保するには、
図１２に示す如く３５０℃超の巻取温度が必須要件であ
ることを知得せしめたのである。These figures show TS × T. El ≧ 200
In order to obtain a residual γ of 5% or more necessary to secure the value of 00, as shown in FIG. 8, it is essential to ensure that V PF / d PF ≧ 20 in low carbon steel with C of less than 0.15%. That is, in order to obtain a residual γ of 5% or more at a base material C concentration of less than 0.15%, the α space factor is further increased beyond that disclosed in JP-A-64-79345. In addition, it is essential to reduce the α grain size or to perform both simultaneously, and to improve spot weldability, it is essential to reduce C to less than 0.15% as shown in FIG. Requirements, for steel grades with low C as used in the present invention, TS ×
T. The compatibility between El ≧ 20,000 and spot weldability is shown in FIG.
In order that the strict adherence to the addition control range of Si and Mn shown in FIG. 0 is an essential requirement, and to obtain particularly excellent surface properties, FIG.
It is essential that the heating temperature be 1170 ° C. or lower as shown in FIG. To ensure high hole expandability with a hole expansion ratio d / d 0 of 1.4 or more, which is regarded as an important workability index in the field of industry along with El ≧ 20,000.
As shown in FIG. 12, the fact that a winding temperature exceeding 350 ° C. is an essential requirement was learned.
【００８１】本発明者等はこれ等の知見を基に本発明の
基本を確立すると共に付帯条件を調整して請求項４、５
及び１３〜２０に記載の本発明を完成するに到ったので
ある。Based on these findings, the present inventors have established the basics of the present invention and adjusted the incidental conditions.
And 13 to 20 of the present invention.
【００８２】[0082]
【実施例】以下、実施例の表中に記載の記号を説明する
と下記の通りである。 ＦＴ０：仕上圧延開始温度（℃） ＦＴ７：仕上圧延終了温度（℃） ＣＴ：捲取温度（℃） ＴＳ：引張強さ（ＭＰａ） ＹＳ：降伏強さ（ＭＰａ） Ｔ．Ｅｌ：全伸び（％） γＲ：残留オーステナイト体積比（％） ＶPF：ポリゴナルフェライト占積率（％） ｄPF：ポリゴナルフェライト粒径（μｍ）DESCRIPTION OF THE PREFERRED EMBODIMENTS The symbols used in the tables of the embodiments are described below. FT0: Finish rolling start temperature (° C) FT7: Finish rolling end temperature (° C) CT: Winding temperature (° C) TS: Tensile strength (MPa) YS: Yield strength (MPa) El: Total elongation (%) γR: Retained austenite volume ratio (%) V PF : Polygonal ferrite space factor (%) d PF : Polygonal ferrite particle size (μm)
【００８３】（実施例１）表１に示す化学成分を有する
鋼を用いて、表２に示す圧延条件で鋼板を製造した。得
られた鋼板の材質を表２に併記した。なお、材質の試験
では、コイル長手方向で９ケ所等間隔で評価用テストピ
ースを採取し、コイル内変動はそれらの最大値と最小値
の差とし、その他は長手方向中央での値である。(Example 1) A steel sheet having the chemical components shown in Table 1 was manufactured under the rolling conditions shown in Table 2. The material of the obtained steel plate is also shown in Table 2. In the test of the material, test pieces for evaluation were sampled at nine equally spaced points in the longitudinal direction of the coil, the variation in the coil was defined as the difference between the maximum value and the minimum value, and the others were values at the center in the longitudinal direction.
【００８４】本発明Ｎｏ．１〜Ｎｏ．１４及びＮｏ．２
２〜Ｎｏ．２４は、いずれも良好な材質を得ており、材
質バラツキも良好である。これに対し比較例であるＮ
ｏ．１５はＣが低いため、Ｎｏ．１６はＭｎが低いた
め、Ｎｏ．１７はＳｉが低いため、残留オーステナイト
が残らず材質が良くない。またＮｏ．１８はＢが多いた
めＴＳ×Ｅｌのバラツキが大きくなっている。さらにＮ
ｏ．１９は捲取温度が高すぎるため、Ｎｏ．２０は仕上
温度が高すぎるため、Ｎｏ．２１は仕上温度が低すぎる
ため、いずれも材質が良くない。According to the present invention No. 1 to No. 14 and No. 2
2-No. No. 24 has obtained a good material, and has good material variation. On the other hand, the comparative example N
o. No. 15 has a low C, and No. 16 has a low Mn. No. 17 has low Si, so that no residual austenite remains and the material is not good. No. 18 is large in B, so that the dispersion of TS × El is large. Further N
o. No. 19 has a too high winding temperature. No. 20 has a too high finishing temperature. Since the finishing temperature of 21 is too low, the material of each is not good.
【００８５】[0085]
【表１】 [Table 1]
【００８６】[0086]
【表２】 [Table 2]
【００８７】（実施例２）表３に示す化学成分を有する
鋼を図３、又は図４に従って、表４〜５に示す条件で鋼
板を製造した。なお、材質の試験では、コイル長手方向
で９ケ所等間隔で評価用テストピースを採取し、コイル
内変動はそれらの最大値と最小値の差とし、その他は長
手方向中央での値である。Example 2 A steel sheet having the chemical components shown in Table 3 was manufactured according to FIG. 3 or FIG. 4 under the conditions shown in Tables 4 and 5. In the test of the material, test pieces for evaluation were sampled at nine equally spaced points in the longitudinal direction of the coil, the variation in the coil was defined as the difference between the maximum value and the minimum value, and the others were values at the center in the longitudinal direction.
【００８８】ここで鋼ＣはＣ量が下限量を割ったもので
あり、鋼Ｅ及び鋼ＨはそれぞれＳｉ量及びＭｎ量が下限
量を割ったものであり、また鋼ＴはＢ量が上限を超えた
ものである。Here, steel C has the C content divided by the lower limit, steel E and steel H have the Si content and Mn content divided by the lower limit, and steel T has the B content at the upper limit. It is beyond.
【００８９】本発明に沿うものはＮｏ．１、Ｎｏ．２、
Ｎｏ．５、Ｎｏ．７、Ｎｏ．９、Ｎｏ．２２〜Ｎｏ．３
２、Ｎｏ．３７、Ｎｏ．３９、Ｎｏ．４１〜Ｎｏ．５４
及びＮｏ．５６〜Ｎｏ．５８であり、当初ＴＳ×Ｔ．Ｅ
ｌ≧２００００をめざしたが、複合効果により、第１３
図に示されるようにＴＳ×Ｔ．Ｅｌ＞２４０００という
非常に良好な強度・延性バランスを示す。No. 1 according to the present invention. 1, No. 2,
No. 5, no. 7, no. 9, No. 22-No. 3
2, No. 37, no. 39, no. 41-No. 54
And No. 56-No. 58 and initially TS × T. E
l ≧ 20000, but due to the combined effect, the thirteenth
As shown in FIG. It shows a very good strength-ductility balance of El> 24000.
【００９０】一方、比較例は各々以下の理由により、良
好な延性が得られていない。On the other hand, in the comparative examples, good ductility was not obtained for the following reasons.
【００９１】Ｎｏ．３、Ｎｏ．４０はＣが低すぎる。No. 3, No. 40 has too low C.
【００９２】Ｎｏ．５、Ｎｏ．３６はＳｉが低すぎる。No. 5, no. 36 has too low Si.
【００９３】Ｎｏ．８、Ｎｏ．３８はＭｎが低すぎる。No. 8, no. 38 has too low Mn.
【００９４】Ｎｏ．１０は仕上全圧下率が低すぎる。No. No. 10 has a too low finish total draft.
【００９５】Ｎｏ．１１は仕上圧延終了温度が低すぎ
る。No. In No. 11, the finish rolling end temperature is too low.
【００９６】Ｎｏ．１２は空冷終了温度が高すぎる。No. In No. 12, the air cooling end temperature is too high.
【００９７】Ｎｏ．１３、Ｎｏ．１４、Ｎｏ．１５は空
冷終了温度Ｔ、Ｔ2が低すぎる。No. 13, No. 14, No. 15 air cooling end temperature T, T 2 is too low.
【００９８】Ｎｏ．１６、Ｎｏ．３３は冷却速度が高
すぎる。No. 16, No. 33 has too high a cooling rate.
【００９９】Ｎｏ．１７、Ｎｏ．３４は冷却速度が低
すぎる。No. 17, No. 34 has too low cooling rate.
【０１００】Ｎｏ．１８は冷却速度’が高すぎる。No. No. 18 is too high in cooling rate.
【０１０１】Ｎｏ．１９は冷却速度’が低すぎる。No. 19, the cooling rate 'is too low.
【０１０２】Ｎｏ．２０、Ｎｏ．３５は捲取温度が高す
ぎる。No. 20, no. 35 is too high in winding temperature.
【０１０３】Ｎｏ．２１は捲取温度が低すぎる。No. No. 21 has too low a winding temperature.
【０１０４】Ｎｏ．５５はＢが高すぎるのでコイル内変
動が大きい。No. 55 has a large variation in the coil because B is too high.
【０１０５】また、Ｎｏ．２５、Ｎｏ．２８、Ｎｏ．３
１は圧延開始温度規制及び捲取後の冷却方法規制を行な
った例である。Also, No. 25, no. 28, no. 3
1 is an example in which the regulation of the rolling start temperature and the regulation of the cooling method after winding are performed.
【０１０６】[0106]
【表３】 [Table 3]
【０１０７】[0107]
【表４】 [Table 4]
【０１０８】[0108]
【表５】 [Table 5]
【０１０９】（実施例３）表６に示す化学成分を有する
鋼を用いて、図７に従って表７〜９に示す圧延条件で鋼
板を製造した。得られた鋼板の材質を表７〜９に併記し
た。なお、材質の試験では、コイル長手方向で９ケ所等
間隔で評価用テストピースを採取し、コイル内変動はそ
れらの最大値と最小値の差とし、その他は長手方向中央
での値である。(Example 3) A steel sheet having the chemical components shown in Table 6 was manufactured under the rolling conditions shown in Tables 7 to 9 in accordance with FIG. The materials of the obtained steel plates are shown in Tables 7 to 9. In the test of the material, test pieces for evaluation were sampled at nine equally spaced points in the longitudinal direction of the coil, the variation in the coil was defined as the difference between the maximum value and the minimum value, and the others were values at the center in the longitudinal direction.
【０１１０】なお、穴拡げ性は円錐ポンチで押広げクラ
ックが板厚を貫通した時点での穴径（ｄ）と初期穴径
（ｄ0）との比（ｄ／ｄ0）で示す。The hole expandability is represented by the ratio (d / d 0 ) of the hole diameter (d) at the time when the crack spreads through the plate thickness with a conical punch and the initial hole diameter (d 0 ).
【０１１１】表７に明らかな如く、本発明例の鋼番１〜
７、１５、１６、２０、２１、２５〜４９、５１〜６１
は、ＴＳ（ＭＰａ）は５１０〜９００を示し、Ｅｌ
（％）は２７〜４７の範囲にあり、ＴＳ×Ｔ．Ｅｌは２
２１００〜３０３６０を示し、ＴＳ×Ｔ．Ｅｌのコイル
内変動が３０００以下で穴拡げ比（ｄ／ｄ0）は１．４
以上を示した。As is clear from Table 7, the steel Nos.
7, 15, 16, 20, 21, 25-49, 51-61
Indicates that TS (MPa) indicates 510 to 900, and El indicates
(%) Is in the range of 27 to 47, and TS × T. El is 2
2100 to 30360, and TS × T. When the variation of El in the coil is 3000 or less, the hole expansion ratio (d / d 0 ) is 1.4.
The above is shown.
【０１１２】またスポット溶接試験を行った供試材の全
てにナゲット（スポット溶接時に溶融し、その後凝固し
た部分）内破断は見られなかった。No break in the nugget (the portion that was melted during spot welding and then solidified) was observed in all of the test materials subjected to the spot welding test.
【０１１３】一方比較例の鋼番８〜１４、１７〜１９、
２２〜２４、５０は何れも本発明の課題を達成する強度
・延性バランスと穴拡げ性とスポット溶接性の並立を示
すに到らなかった。On the other hand, steel numbers 8 to 14, 17 to 19, and
All of Nos. 22 to 24 and 50 did not show strength, ductility balance, hole expandability, and spot weldability at the same time to achieve the object of the present invention.
【０１１４】即ち、Ｃ量が本発明の下限に達しなかった
鋼番８は、残留オーステナイト占積率が本発明の規制を
満たさず、ＴＳ×Ｔ．Ｅｌが２００００を下廻った。That is, in steel No. 8 in which the C content did not reach the lower limit of the present invention, the retained austenite space factor did not satisfy the regulation of the present invention, and TS × T. El fell below 20,000.
【０１１５】巻取温度が本発明の規制を満たさず、マル
テンサイトの生成を見た鋼番１４は、残留γ占積率が本
発明の規制を満たさず、ＴＳ×Ｔ．Ｅｌが２００００を
下回ると共にｄ／ｄ0は１．４に達しなかった。Steel No. 14 in which the winding temperature did not satisfy the regulation of the present invention and the formation of martensite was observed, the residual γ space factor did not satisfy the regulation of the present invention, and TS × T. As El dropped below 20,000, d / d 0 did not reach 1.4.
【０１１６】冷却条件、ないしは巻取温度が本発明の規
制を満たさず、パーライトの生成を見た鋼番１３、１
９、２４は、残留γ占積率が本発明の規制を満たさず、
ＴＳ×Ｔ．Ｅｌが２００００を下回った。The cooling conditions or the winding temperature did not satisfy the regulation of the present invention, and the formation of pearlite was observed.
9, 24, the residual γ space factor does not satisfy the regulation of the present invention,
TS × T. El fell below 20,000.
【０１１７】仕上圧延温度、圧下率が本発明の規制を満
たさず、残留γ占積率とＶPF／ｄPFが共に本発明の規制
に達しなかった鋼番１１と、冷却条件が本発明の規制を
満たさなかった、鋼番１７、１８、２２、２３、仕上圧
延温度が本発明の規制を満たさず加工フェライトが生成
した鋼番１２等は何れもＴ．Ｅｌが低く、ＴＳ×Ｔ．Ｅ
ｌが１８０００以下を示し何れも本発明の課題を解決し
得なかった。The steel number 11 in which the finish rolling temperature and the rolling reduction did not satisfy the regulation of the present invention, and both the residual γ space factor and V PF / d PF did not satisfy the regulation of the present invention, and the cooling condition was the same as that of the present invention. The steel numbers 17, 18, 22, and 23, which did not satisfy the regulations, and the steel numbers 12 and the like, in which the finish rolling temperature did not satisfy the regulations of the present invention and the processed ferrite was formed, were all T.M. El is low, and TS × T. E
1 showed 18000 or less, and none of them could solve the problem of the present invention.
【０１１８】またＴＳ×Ｔ．Ｅｌが２６０００を示した
鋼番１０はＣ量が本発明の上限を上回るため、スポット
溶接試験でナゲット内破断が見られ、さらにｄ／ｄ0が
１．４に満たず、本発明の課題を解決し得なかった。Further, TS × T. Steel No. 10 having an El of 26000 has a C content exceeding the upper limit of the present invention, so that a breakage in the nugget is observed in a spot welding test, and d / d 0 is less than 1.4. I could not solve it.
【０１１９】また、鋼番５０はＢ含有量が上限を超えて
いるためＴＳ×Ｔ．Ｅｌのコイル内変動が３０００を超
えている。In steel No. 50, since the B content exceeds the upper limit, TS × T. The variation of El in the coil exceeds 3000.
【０１２０】[0120]
【表６】 [Table 6]
【０１２１】[0121]
【表７】 [Table 7]
【０１２２】[0122]
【表８】 [Table 8]
【０１２３】[0123]
【表９】 [Table 9]
【０１２４】[0124]
【発明の効果】本発明は上記の如く構成し、作用せしめ
ることにより、一例として示す実施例からも明らかな如
く、優れたスポット溶接性と、強度・延性バランス及び
加工性を備えた材質バラツキの小さい熱延鋼板とその製
造方法の提供を可能としたもので、この種鋼板を用いて
製品を製造する作業性の向上、生産性の向上、歩留の向
上は著しく、この種分野にもたらす経済的、工業的効果
は大きい。The present invention is constructed and operated as described above, and as is apparent from the embodiment shown as an example, it is possible to reduce the variation in material having excellent spot weldability, strength-ductility balance and workability. It has made it possible to provide small hot-rolled steel sheets and a method of manufacturing the same. The improvement in workability, productivity, and yield of manufacturing products using this kind of steel sheet is remarkable, and the economy brought to this kind of field The industrial and industrial effects are great.
【図１】残留オーステナイト体積比とＴＳ×Ｔ．Ｅｌの
関係を示した図である。FIG. 1. Volume ratio of retained austenite and TS × T. It is a figure showing the relation of El.
【図２】ＶPF／ｄPFとＴＳ×Ｔ．Ｅｌの関係を示した図
である。FIG. 2 shows V PF / d PF and TS × T. It is a figure showing the relation of El.
【図３】仕上圧延終了温度、冷却速度、Ｔ、冷却速度
の関係を示した温度パターン図である。FIG. 3 is a temperature pattern diagram showing a relationship among finish rolling end temperature, cooling rate, T, and cooling rate.
【図４】仕上圧延終了温度、冷却速度’、Ｔ1、冷却
速度’、Ｔ2、冷却速度’の関係を示した温度パタ
ーン図である。FIG. 4 is a temperature pattern diagram showing a relationship among finish rolling end temperature, cooling rate ', T 1 , cooling rate', T 2 , cooling rate '.
【図５】捲取温度と残留オーステナイト体積比の関係を
示した図である。FIG. 5 is a diagram showing a relationship between a winding temperature and a volume ratio of retained austenite.
【図６】捲取温度と穴拡げ比の関係を示した図である。FIG. 6 is a diagram showing a relationship between a winding temperature and a hole expansion ratio.
【図７】本発明で使用する冷却方法の説明図である。FIG. 7 is an explanatory diagram of a cooling method used in the present invention.
【図８】α占積率／α粒径と残留γ量の関係を示す図で
ある。FIG. 8 is a diagram showing a relationship between α space factor / α particle size and residual γ amount.
【図９】Ｃ重量％とスポット溶接性の関係を示す図であ
る。FIG. 9 is a diagram showing a relationship between C weight% and spot weldability.
【図１０】Ｓｉ重量％とＭｎ重量％と残留γ量の関係を
示す図である。FIG. 10 is a diagram showing a relationship between Si weight%, Mn weight%, and residual γ amount.
【図１１】加熱温度と鋼板の表面性状の関係を示す図で
ある。FIG. 11 is a diagram showing a relationship between a heating temperature and a surface property of a steel sheet.
【図１２】巻取温度と穴拡げ比の関係を示す図である。FIG. 12 is a diagram showing a relationship between a winding temperature and a hole expansion ratio.
【図１３】ＴＳとＴ．Ｅｌの関係を示した図である。FIG. 13 shows TS and T. It is a figure showing the relation of El.
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Claims (20)
〜０．４％、Ｓｉ：０．５〜３．０％、Ｍｎ：０．５〜
３．０％、Ｐ：０．１％以下、Ｓ：０．０５％以下、Ａ
ｌ：０．１％以下含み、不純物としてのＢ：０．０００
５％以下に制限し、残部Ｆｅ及び不可避的不純物であ
り、特性として、強度−延性バランス（引張強さ×全伸
び）が２００００（ＭＰａ・％）以上で、かつ、そのコ
イル内変動が３０００（ＭＰａ・％）未満であることを
特徴とする材質バラツキの小さい加工性に優れた熱延高
強度鋼板。C. 0.05 as a chemical component in weight%.
0.4%, Si: 0.5 to 3.0%, Mn: 0.5 to
3.0%, P: 0.1% or less, S: 0.05% or less, A
l: 0.1% or less, B: 0.000 as an impurity
5% or less, the balance being Fe and inevitable impurities. As a characteristic, the strength-ductility balance (tensile strength × total elongation) is 20,000 (MPa ·%) or more, and the variation in the coil is 3,000 (MPa ·%). (MPa ·%), a hot-rolled high-strength steel sheet excellent in workability with small material variation.
〜０．４％、Ｓｉ：０．５〜３．０％、Ｍｎ：０．５〜
３．０％、Ｐ：０．１％以下、Ｓ：０．０５％以下、Ａ
ｌ：０．１％以下、Ｎ：０．１％以下含み、不純物とし
てのＢ：０．０００５％以下に制限し、残部Ｆｅ及び不
可避的不純物であり、特性として、強度−延性バランス
（引張強さ×全伸び）が２００００（ＭＰａ・％）以上
で、かつ、そのコイル内変動が３０００（ＭＰａ・％）
未満であることを特徴とする材質バラツキの小さい加工
性に優れた熱延高強度鋼板。2. C: 0.05 by weight% as a chemical component.
0.4%, Si: 0.5 to 3.0%, Mn: 0.5 to
3.0%, P: 0.1% or less, S: 0.05% or less, A
l: 0.1% or less, N: 0.1% or less, B as an impurity is limited to 0.0005% or less, the balance is Fe and inevitable impurities, and as a characteristic, strength-ductility balance (tensile strength) (Total elongation) is 20,000 (MPa ·%) or more, and the variation in the coil is 3000 (MPa ·%).
A hot-rolled high-strength steel sheet excellent in workability with a small variation in material, characterized in that the steel sheet has a material variation of less than.
〜０．３％、Ｓｉ：０．５〜３．０％、Ｍｎ：０．５〜
３．０％、Ｐ：０．１％以下、Ｓ：０．０５％以下、Ａ
ｌ：０．１％以下、Ｎ：０．１％以下含み、不純物とし
てのＢ：０．０００５％以下に制限し、残部Ｆｅ及び不
可避的不純物であり、ミクロ組織として、ポリゴナルフ
ェライト占積率ＶPF（％）とポリゴナルフェライト平均
粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でかつ残留オ
ーステナイトを体積比で５％以上含むフェライト、ベイ
ナイト及び残留オーステナイトの組織から構成され、特
性として、強度−延性バランスＴＳ×Ｔ．Ｅｌが２００
００（ＭＰａ・％）以上で、かつ、そのコイル内変動が
３０００（ＭＰａ・％）未満であることを特徴とする材
質バラツキの小さい加工性に優れた熱延高強度鋼板。3. C: 0.15% by weight as a chemical component
0.3%, Si: 0.5-3.0%, Mn: 0.5-
3.0%, P: 0.1% or less, S: 0.05% or less, A
l: 0.1% or less, N: 0.1% or less, B as impurities: limited to 0.0005% or less, the balance being Fe and unavoidable impurities, and as a microstructure, polygonal ferrite space factor The ratio of V PF (%) to polygonal ferrite average particle diameter d PF (μm) V PF / d PF is 7 or more, and is composed of ferrite, bainite and retained austenite containing 5% or more by volume of retained austenite. As a characteristic, strength-ductility balance TS × T. El is 200
A hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized in that the variation in the coil is not less than 00 (MPa ·%) and the variation in the coil is less than 3000 (MPa ·%).
〜０．１５％未満、Ｓｉ：０．５〜２．５％、Ｍｎ：
０．５〜２．５％、Ｐ：０．０２％以下、Ｓ：０．０１
％以下、Ａｌ：０．００５〜０．１％を含み、１．６％
＜Ｓｉ＋Ｍｎ≦５．０％を満たし、不純物としてのＢ：
０．０００５％以下に制限し、残部Ｆｅ及び不可避的不
純物であり、ミクロ組織はポリゴナルフェライト占積率
ＶPF（％）とポリゴナルフェライト粒径ｄPF（μｍ）の
比ＶPF／ｄPFが２０以上、残留オーステナイトの占積率
が５％以上で残部がベイナイトからなり、特性として、
強度−延性バランス（引張強さ×全伸び）が２００００
（ＭＰａ・％）以上で、かつ、そのコイル内変動が３０
００（ＭＰａ・％）未満であることを特徴とする材質バ
ラツキの小さい加工性とスポット溶接性に優れた熱延高
強度鋼板。4. C: 0.05 by weight as a chemical component.
~ 0.15%, Si: 0.5-2.5%, Mn:
0.5 to 2.5%, P: 0.02% or less, S: 0.01
%, 1.6% including Al: 0.005 to 0.1%
<Si + Mn ≦ 5.0%, and B as an impurity:
It is limited to 0.0005% or less, the balance is Fe and inevitable impurities, and the microstructure is a ratio V PF / d PF between the polygonal ferrite space factor V PF (%) and the polygonal ferrite particle size d PF (μm). Is 20 or more, the space factor of the retained austenite is 5% or more, and the balance is bainite.
Strength-ductility balance (tensile strength x total elongation) of 20,000
(MPa.%) Or more and the variation in the coil is 30
A hot-rolled high-strength steel sheet excellent in workability with small material variation and spot weldability, characterized by being less than 00 (MPa ·%).
ｕ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｃａ、ＲＥＭ
の１種又は２種以上を含有し、その内Ｃｕ、Ｎｉ、Ｃ
ｒ、Ｍｏにおいては、それらの１種又は２種以上を合計
量で０．５％以下、Ｎｂ、Ｔｉ、Ｖにおいては、それら
の１種又は２種以上を合計量で０．３％以下、Ｃａにお
いては０．０１％以下、ＲＥＭにおいては０．０５％以
下であることを特徴とする前記請求項１乃至４の内の何
れか１つに記載の熱延高強度鋼板。5. The chemical component in weight%,
u, Ni, Cr, Mo, Nb, Ti, V, Ca, REM
Containing one or more of Cu, Ni, C
In r and Mo, one or more of them are 0.5% or less in total, and in Nb, Ti and V, one or two or more of them are 0.3% or less in total. The hot-rolled high-strength steel sheet according to any one of claims 1 to 4, wherein Ca is 0.01% or less and REM is 0.05% or less.
鋼を、仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０
℃、全圧下率８０％以上で熱間圧延を行い、続いて３５
０℃〜５００℃までを、冷却速度４０℃／ｓ以上で冷却
して巻取ることを特徴とする材質バラツキの小さい加工
性に優れた熱延高強度鋼板の製造方法。6. A finish-rolling finish temperature of Ar 3 -50 ° C. to Ar 3 +50, wherein the steel having the chemical composition according to claim 1 or 2 is used.
Hot rolling at 80 ° C. and a total draft of 80% or more.
A method for producing a hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized in that it is cooled at a cooling rate of 40 ° C./s or more from 0 ° C. to 500 ° C. and wound.
鋼を、仕上圧延開始温度をＡｒ3＋１００℃以下、仕上
圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０℃、全圧下率
８０％以上で熱間圧延を行い、続いて３５０℃〜５００
℃までを、冷却速度４０℃／ｓ以上で冷却して巻取り
後、鋼板を３０℃／ｈｒ以上の冷却速度で２００℃以下
まで冷却することを特徴とする材質バラツキの小さい加
工性に優れた熱延高強度鋼板の製造方法。7. A steel having the chemical composition according to claim 1 or 2, wherein a finish rolling start temperature is Ar 3 + 100 ° C. or less, a finish rolling end temperature Ar 3 -50 ° C. to Ar 3 + 50 ° C., and a total rolling reduction is 80. % Hot rolling at 350% to 500 ° C.
After cooling to 40 ° C. at a cooling rate of 40 ° C./s or more and winding, the steel sheet is cooled to 200 ° C. or less at a cooling rate of 30 ° C./hr or more, and excellent in workability with small material variation. Manufacturing method of hot-rolled high-strength steel sheet.
仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０℃、全圧
下率８０％以上で熱間圧延を行い、該温度から４０℃／
ｓ未満の冷却速度で冷却を開始し、その鋼のＡｒ3以下
でかつ前記圧延終了温度より低い温度からＡｒ1より高
い温度範囲内の任意の温度Ｔで前記冷却を終了し、続い
て冷却速度４０℃／ｓ以上で冷却して３５０℃〜５００
℃で巻取り、ポリゴナルフェライト占面率ＶPF（％）と
ポリゴナルフェライト平均粒径ｄPF（μｍ）の比ＶPF／
ｄPFが７以上でかつ残留オーステナイトを体積比で５％
以上含むフェライト、ベイナイト及び残留オーステナイ
トの組織とすることを特徴とする材質バラツキの小さい
加工性に優れた熱延高強度鋼板の製造方法。8. The steel of chemical composition according to claim 3,
Finish rolling finish temperature: Ar 3 -50 ° C. to Ar 3 + 50 ° C., hot rolling is performed at a total draft of 80% or more.
The cooling is started at a cooling rate of less than s, and the cooling is terminated at an arbitrary temperature T within a temperature range from a temperature lower than Ar 3 of the steel and lower than the rolling end temperature to a temperature higher than Ar 1. Cool at 40 ° C / s or more and 350 ° C to 500
C., and the ratio of polygonal ferrite area ratio V PF (%) to polygonal ferrite average particle size d PF (μm) V PF /
d PF is 7 or more and retained austenite is 5% by volume
A method for producing a hot-rolled high-strength steel sheet excellent in workability with small variation in material, characterized by having a structure of ferrite, bainite and retained austenite as described above.
全圧下率８０％以上の熱間仕上圧延を行い、その圧延終
了温度をＡｒ3−５０℃〜Ａｒ3＋５０℃とし、続いて前
記鋼のＡｒ3以下でかつ前記圧延終了温度より低い温度
からＡｒ1より高い温度範囲内においてＴ1＞Ｔ2なる２
つの任意の温度を設定し、前記Ｔ1まで冷却速度４０℃
／ｓ以上で冷却し、続けて冷却速度４０℃／ｓ未満で前
記Ｔ2まで冷却し、さらに続けて冷却速度４０℃／ｓ以
上で冷却して３５０〜５００℃で巻取り、ポリゴナルフ
ェライト占積率ＶPF（％）とポリゴナルフェライト平均
粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でかつ残留オ
ーステナイトを体積比で５％以上含むフェライト、ベイ
ナイト及び残留オーステナイトの組織とすることを特徴
とする材質バラツキの小さい加工性に優れた熱延高強度
鋼板の製造方法。9. The steel of chemical composition according to claim 3,
Hot finish rolling at a total draft of 80% or more is performed, and the rolling end temperature is set to Ar 3 -50 ° C. to Ar 3 + 50 ° C. Then, the temperature is reduced from Ar 3 or lower of the steel to a temperature lower than the rolling end temperature. T 1 in the temperature range higher than 1> T 2 becomes 2
One of setting an arbitrary temperature, the cooling rate 40 ° C. until the T 1
Cooled in / s or more, followed by cooling below the cooling rate of 40 ° C. / s until the T 2, coiling at 350 to 500 ° C. and further followed by cooling at a cooling rate 40 ° C. / s or higher, the polygonal ferrite occupied The structure of ferrite, bainite and retained austenite, in which the ratio V PF / d PF between the product moment V PF (%) and the average particle size of polygonal ferrite d PF (μm) is 7 or more and contains 5% or more of retained austenite by volume. A method for producing a hot-rolled high-strength steel sheet excellent in workability with small material variation.
を、全圧下率８０％以上の熱間仕上圧延を行い、その圧
延終了温度をＡｒ3＋５０℃超とし、続いて前記鋼のＡ
ｒ3からＡｒ1超までの温度範囲内において、Ｔ1＞Ｔ2な
る２つの任意の温度を設定し、前記Ｔ1まで冷却速度４
０℃／ｓ以上で冷却し、続けて冷却速度４０℃／ｓ未満
で前記Ｔ2まで冷却し、さらに続けて冷却速度４０℃／
ｓ以上で冷却して３５０〜５００℃で巻取り、ポリゴナ
ルフェライト占積率ＶPF（％）とポリゴナルフェライト
平均粒径ｄPF（μｍ）の比ＶPF／ｄPFが７以上でかつ残
留オーステナイトを体積比で５％以上含むフェライト、
ベイナイト及び残留オーステナイトの組織とすることを
特徴とする材質バラツキの小さい加工性に優れた熱延高
強度鋼板の製造方法。10. The steel having the chemical composition according to claim 3 is subjected to hot finish rolling at a total draft of 80% or more, and the rolling end temperature is set to be higher than Ar 3 + 50 ° C.
Within the temperature range from r 3 to more than Ar 1, two arbitrary temperatures T 1 > T 2 are set, and the cooling rate is 4 to T 1.
0 ° C. / s and cooled by more, followed by cooling below the cooling rate of 40 ° C. / s until the T 2, further followed by cooling rate 40 ° C. /
After cooling at 350-500 ° C, the ratio of polygonal ferrite space factor V PF (%) to polygonal ferrite average particle size d PF (μm) V PF / d PF is 7 or more and remains. Ferrite containing 5% or more by volume of austenite,
A method for producing a hot-rolled high-strength steel sheet having a small workability and excellent workability, characterized by having a structure of bainite and retained austenite.
０℃以下とすることを特徴とする前記請求項６及び８乃
至１０の内の何れか１つに記載の材質バラツキの小さい
加工性に優れた熱延高強度鋼板の製造方法。11. The hot finish rolling start temperature is Ar 3 +10.
The method for producing a hot-rolled high-strength steel sheet according to any one of Claims 6 and 8 to 10, characterized in that the temperature is set to 0 ° C or lower and the workability is small and the workability is small.
０℃／ｈｒ以上の冷却速度で２００℃以下まで冷却する
ことを特徴とする前記請求項６及び８乃至１１の内の何
れか１つに記載の材質バラツキの小さい加工性に優れた
熱延高強度鋼板の製造方法。12. The rolled steel sheet after hot finish rolling is 3
The hot-rolling height according to any one of claims 6 and 8 to 11, wherein the hot-rolling height is excellent in workability with a small material variation, wherein the cooling is performed at a cooling rate of 0 ° C / hr or more to 200 ° C or less. Manufacturing method of high strength steel sheet.
を、仕上圧延終了温度Ａｒ3−５０℃〜Ａｒ3＋５０℃、
全圧下率８０％以上で熱間圧延を行い、該圧延に続いて
該温度Ｔ11から４０℃／秒以上の冷却速度で冷却し、５
００℃以下３５０℃超で巻取って後放冷する事を特徴と
する材質バラツキの小さい加工性とスポット溶接性に優
れた熱延高強度鋼板の製造方法。13. The steel of the chemical composition according to claim 4, wherein a finish rolling end temperature Ar 3 -50 ° C. to Ar 3 + 50 ° C.
Subjected to hot rolling at a total reduction ratio of 80% or more, subsequent to the rolling and cooled in the temperature T 11 from 40 ° C. / sec or more cooling rate, 5
A method for producing a hot-rolled high-strength steel sheet excellent in workability with small material variation and excellent spot weldability, characterized in that it is wound at a temperature of not more than 00 ° C and more than 350 ° C and then left to cool.
を、圧下率８０％以上で熱間圧延し、Ａｒ3−５０℃以
上で終了した該圧延に続いて該温度Ｔ21から４０℃／秒
未満の降温速度で３〜２５秒保定後、Ａｒ1超の温度範
囲内の温度Ｔ22から４０℃／秒以上の冷却速度で冷却
し、５００℃以下３５０℃超で巻取って後放冷する事を
特徴とする材質バラツキの小さい加工性とスポット溶接
性に優れた熱延高強度鋼板の製造方法。14. The steel having the chemical composition according to claim 4, which is hot-rolled at a rolling reduction of 80% or more, followed by the rolling completed at Ar 3 -50 ° C. or more, and subsequently at the temperature T 21 to 40 ° C. / sec less cooling rate at 3-25 Byohojogo, cooled at a cooling rate from the temperature T 22 of 40 ° C. / sec or more within a temperature range of Ar 1 greater, release post wound up at 500 ° C. or less 350 ° C. greater A method for producing a hot-rolled high-strength steel sheet that is characterized by cooling and has excellent workability with small material variations and excellent spot weldability.
を、圧下率８０％以上で熱間圧延し、Ａｒ3−５０℃以
上で該圧延を終了し、続いて該温度Ｔ31から冷却速度４
０℃／秒以上でＴ32（Ａｒ3＞Ｔ32＞Ａｒ1）温度まで冷
却し、続いて４０℃／秒未満の降温速度でＴ33（Ａｒ3
＞Ｔ32≧Ｔ33＞Ａｒ1）まで３〜２５秒保定後、冷却速
度４０℃／秒以上で冷却し、５００℃以下３５０℃超で
巻取って後放冷する事を特徴とする材質バラツキの小さ
い加工性とスポット溶接性に優れた熱延高強度鋼板の製
造方法。The 15. Steel chemical components according to claim 4, hot-rolled at a reduction ratio of 80% or more, and terminates the rolling at Ar 3 -50 ° C. or higher, followed by cooling from the temperature T 31 Speed 4
Cool to a temperature of T 32 (Ar 3 > T 32 > Ar 1 ) at 0 ° C./sec or more, and then cool T 33 (Ar 3
> T 32 ≧ T 33 > Ar 1 ), after cooling for 3 to 25 seconds, cooling at a cooling rate of 40 ° C./sec or more, winding at a temperature of 500 ° C. or less and exceeding 350 ° C., and then allowing to cool. Of hot-rolled high-strength steel sheet with excellent workability and spot weldability.
℃以下とすることを特徴とする前記請求項１３乃至１５
の内の何れか１つに記載の材質バラツキの小さい加工性
とスポット溶接性に優れた熱延高強度鋼板の製造方法。16. The heating temperature before hot finish rolling is 1170.
The temperature is set to not more than ℃.
The method for producing a hot-rolled high-strength steel sheet according to any one of the above, which is excellent in workability with small material variation and spot weldability.
０℃以下とすることを特徴とする前記請求項１３乃至１
６の内の何れか１つに記載の材質バラツキの小さい加工
性とスポット溶接性に優れた熱延高強度鋼板の製造方
法。17. The hot finish rolling start temperature is Ar 3 +10
13. The method according to claim 13, wherein the temperature is 0 ° C. or less.
6. The method for producing a hot-rolled high-strength steel sheet according to any one of Nos. 6 and 7, which is excellent in workability with small material variation and excellent spot weldability.
３０℃／ｈｒ以上の冷却速度で２００℃以下まで冷却し
て後放冷することを特徴とする前記請求項１３乃至１７
の内の何れか１つに記載の材質バラツキの小さい加工性
とスポット溶接性に優れた熱延高強度鋼板の製造方法。18. The method according to claim 13, wherein the rolled steel sheet after hot finish rolling is cooled to 200 ° C. or less at a cooling rate of 30 ° C./hr or more, and then left to cool.
The method for producing a hot-rolled high-strength steel sheet according to any one of the above, which is excellent in workability with small material variation and spot weldability.
℃以下とし、熱間仕上圧延開始温度をＡｒ3＋１００℃
以下とし、さらに前記熱間仕上圧延後の巻き取り後の鋼
板を３０℃／ｈｒ以上の冷却速度で２００℃以下まで冷
却することを特徴とする前記請求項１３乃至１５の内の
何れか１つに記載の材質バラツキの小さい加工性とスポ
ット溶接性に優れた熱延高強度鋼板の製造方法。19. The heating temperature before hot finish rolling is 1170
° C or lower and the hot finish rolling start temperature is Ar 3 + 100 ° C
The method according to any one of claims 13 to 15, wherein the rolled steel sheet after the hot finish rolling is further cooled to 200 ° C or lower at a cooling rate of 30 ° C / hr or higher. A method for producing a hot-rolled high-strength steel sheet excellent in workability with small material variation and excellent spot weldability described in 1.
Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｃａ、ＲＥＭの１
種又は２種以上を含有し、重量％で、その内Ｃｕ、Ｎ
ｉ、Ｃｒ、Ｍｏにおいては、それらの１種又は２種以上
を合計で０．５％以下、Ｎｂ、Ｔｉ、Ｖにおいては、そ
れらの１種又は２種以上を合計量で０．３％以下、Ｃａ
においては０．０１％以下、ＲＥＭにおいては０．０５
％以下であることを特徴とする前記請求項６乃至１９の
内の何れか１つに記載の熱延高強度鋼板の製造方法。20. The steel further comprising, as a chemical component, Cu,
Ni, Cr, Mo, Nb, Ti, V, Ca, REM 1
Or two or more species, in% by weight of which Cu, N
For i, Cr, Mo, one or more of them are 0.5% or less in total, and for Nb, Ti, V, one or more of them are 0.3% or less in total. , Ca
, 0.01% or less in REM, 0.05 in REM
% Or less, the method for manufacturing a hot-rolled high-strength steel sheet according to any one of claims 6 to 19, wherein
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16807599A JP2000355735A (en) | 1999-06-15 | 1999-06-15 | Hot rolled high strength steel sheet small in variation of material and excellent in workability and its production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16807599A JP2000355735A (en) | 1999-06-15 | 1999-06-15 | Hot rolled high strength steel sheet small in variation of material and excellent in workability and its production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000355735A true JP2000355735A (en) | 2000-12-26 |
Family
ID=15861388
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16807599A Withdrawn JP2000355735A (en) | 1999-06-15 | 1999-06-15 | Hot rolled high strength steel sheet small in variation of material and excellent in workability and its production |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000355735A (en) |
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