JPH09241755A - Production of steel sheet excellent in deep drawability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet excellent in deep drawability with low energy by subjecting a steel stock of specific composition to hot rolling at respectively specified finishing temp. and draft and then to recrystallization treatment by self-annealing or soaking treatment. SOLUTION: A steel stock having a steel composition consisting of, by weight, <=0.01% C, <=2.0% Si, <=3.0% Mn, <=0.15% P, <=0.05% S, 0.01-0.2% Al, <=0.01% N, 0.0001-0.0080% B, either or both of 0.005-0.20% Ti and 0.015-0.20% Nb, and the balance Fe with inevitable impurities is used. This steel stock is finish-rolled at a temp. between the Ar3 transformation point and 500 deg.C at 50-95% total draft. Further, while applying high-degree lubrication to each stand where inlet thickness during rolling is <=10mm, rolling is carried out so that a pass draft X% satisfies the relation of X>=(4/3)×(expected TS)(kgf/mm<2> )-30. Then, hot rolled plate recrystallization treatment is performed by means of self-annealing or soaking and heating at 700-950 deg.C.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、薄鋼板の製造方法
に関し、特に自動車用鋼板の使途に有用な深絞り性に優
れた薄鋼板の製造に係わる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin steel sheet, and more particularly to the production of a thin steel sheet having excellent deep drawability, which is useful for use as a steel sheet for automobiles.

【０００２】[0002]

【従来の技術】一般に、自動車に用いられる鋼板には、
高加工性が要求され、また、機械特性として高いｒ値
（ランクフォード値）と良好な延性が要求される。その
ため、深絞り用（高加工性）薄鋼板は、比較的軟らかい
低炭素Ａｌキルド鋼あるいは極低炭素鋼に通常の熱間圧
延を施した後、冷間圧延、再結晶焼鈍を順次施して製造
されていた。2. Description of the Related Art Generally, steel sheets used for automobiles are
High workability is required, and high r value (Rankford value) and good ductility are required as mechanical properties. Therefore, a deep-drawing (high workability) thin steel sheet is manufactured by subjecting a relatively soft low carbon Al killed steel or an ultra-low carbon steel to normal hot rolling, followed by cold rolling and recrystallization annealing in sequence. It had been.

【０００３】ところで、該鋼板の深絞り性向上に関する
技術としては、特開平５−３３９６４３号公報が開示し
た「仕上圧延を変態点以下で潤滑を施しつつ行う方法」
がある。しかしながら、特開平５−３３９６４３号公報
記載の方法では、４０ｋｇｆ／ｍｍ² 以上のハイテンで
期待したほど、高ｒ値が得られない。また、軟鋼におい
ても仕上圧延全域を潤滑熱延をするのはコスト・エネル
ギがかかる。さらに、潤滑下での圧下率をどう最適化す
るかについての記載が無いが、例えば特開昭６４−３１
９３５号公報によると、従来から低温域すなわち後段で
かなりの強圧下が必要とされており、この点でもコスト
・エネルギ上不利である。By the way, as a technique for improving the deep drawability of the steel sheet, "a method of performing finish rolling while lubricating below a transformation point" disclosed in Japanese Patent Laid-Open No. 5-339643.
There is. However, the method described in JP-A-5-339643 cannot obtain a high r value as expected with a high tensile strength of 40 kgf / mm ² or more. Further, even in mild steel, it takes cost and energy to carry out lubrication hot rolling over the entire finish rolling. Further, there is no description on how to optimize the rolling reduction under lubrication, but for example, JP-A-64-31
According to Japanese Patent Laid-Open No. 935, it has been conventionally required to carry out a considerable reduction in a low temperature range, that is, in the latter stage, which is also disadvantageous in terms of cost and energy.

【０００４】[0004]

【発明が解決しようとする課題】本発明は、上記の課題
を有利に解決するものであり、鋼成分及び製造条件を特
定することにより、ＴＳ ４０ｋｇｆ／ｍｍ² 以上のハ
イテンでは、従来より格段に優れた深絞り性を有する鋼
板、軟鋼では、従来より格段に経済的に深絞り性を有す
る鋼板を製造する方法を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and by specifying the steel composition and manufacturing conditions, in the high tensile steel with TS of 40 kgf / mm ² or more, the present invention is remarkably higher than before. It is an object of the present invention to provide a method for manufacturing a steel sheet having excellent deep drawability, which is much more economical than conventional steel sheets and mild steel.

【０００５】[0005]

【課題を解決するための手段】発明者は、上記目的を達
成すべく鋭意研究し、以下の知見を得た。例えば、Ｃ：
０．００２０ｗｔ％、Ｓｉ：０．１〜２．０ｗｔ％、Ｍ
ｎ：０．１〜３．０ｗｔ％、Ｐ：０．０１〜０．１５ｗ
ｔ％、Ｓ：０．００５０ｗｔ％、Ａｌ：０．０６ｗｔ
％、Ｎ：０．００２５ｗｔ％、Ｎｂ：０．０２５ｗｔ
％、Ｂ：０．００３０ｗｔ％を含有し、残部はＦｅ及び
不可避的不純物よりなる鋼鋳片を１１５０℃に加熱〜均
熱後、熱間仕上げ温度を７００℃として合計仕上げ圧下
率（複数の仕上げスタンドでの）が８５％になるよう熱
間圧延を強潤滑、あるいは無潤滑で行った後、均熱温度
８５０℃で該熱延板に再結晶化処理を施した。そして、
仕上圧延前の板厚２３ｍｍ，仕上圧延出側の板厚３．５
ｍｍと一定にし、潤滑圧延時の各パス入側厚を８．８ｍ
ｍ以下とした。得られた薄鋼板のｒ値に及ぼす圧下率の
影響を調査したところ、図１に示す結果になった。この
図１の結果は、各パスの圧下率Ｘ（％）が次式，つま
り、Ｘ≧（４／３×ＴＳ（ｋｇｆ／ｍｍ² ）−３０）な
る関係を満たし、かつ強潤滑圧延を施すと、鋼板のｒ値
が１．５以上になることを示唆した。特に、ハイテンに
おいては、強度に応じた高圧下率で、従来より高ｒ値が
可能であり、軟鋼においては、低圧下率で入側板厚の薄
い場合のみ潤滑を施すことで十分高ｒ値が得られる。[Means for Solving the Problems] The inventor earnestly studied to achieve the above object and obtained the following findings. For example, C:
0.0020 wt%, Si: 0.1-2.0 wt%, M
n: 0.1 to 3.0 wt%, P: 0.01 to 0.15 w
t%, S: 0.0050 wt%, Al: 0.06 wt
%, N: 0.0025 wt%, Nb: 0.025 wt
%, B: 0.0030 wt% and the balance of the steel slab consisting of Fe and unavoidable impurities is heated to 1150 ° C. and soaked, and the hot finishing temperature is set to 700 ° C. After hot rolling was performed with strong lubrication or without lubrication so that the (on the stand) was 85%, the hot-rolled sheet was subjected to recrystallization treatment at a soaking temperature of 850 ° C. And
Plate thickness before finish rolling 23 mm, plate thickness at finish rolling exit side 3.5
mm, and the thickness on each pass entry side during lubrication rolling is 8.8 m.
m or less. When the influence of the rolling reduction on the r value of the obtained thin steel sheet was investigated, the results shown in FIG. 1 were obtained. The result of FIG. 1 is that the rolling reduction X (%) of each pass satisfies the following expression, that is, the relation of X ≧ (4/3 × TS (kgf / mm ² ) −30), and strong lubrication rolling is performed. It was suggested that the r value of the steel sheet was 1.5 or more. In particular, in high-tensile steel, a high r-value can be achieved at a higher pressure ratio depending on strength than in the past, and in mild steel, a sufficiently high r-value can be obtained by applying lubrication only at a low-pressure ratio and a small entry side plate thickness. can get.

【０００６】そこで、発明者は、図１の強潤滑の場合と
同様な結果を得る素材の鋼成分、圧延条件及び熱処理条
件をさらに詳細に検討し、本発明を完成させた。すなわ
ち、本発明は、Ｃ：０．０１ｗｔ％以下、Ｓｉ：２．０
ｗｔ％以下、Ｍｎ：３．０ｗｔ％以下、Ｐ：０．１５ｗ
ｔ％以下、Ｓ：０．０５ｗｔ％以下、Ａｌ：０．０１〜
０．２ｗｔ％、Ｎ：０．０１ｗｔ％以下、Ｂ：０．００
０１〜０．００８０ｗｔ％を含み、且つＴｉ：０．００
５〜０．２０ｗｔ％ Ｎｂ：０．０１５〜０．２０ｗｔ％の１種又は２種を含
有し，残部はＦｅ及び不可避的不純物よりなる鋼素材
に、Ａｒ₃ 変態点以下、５００℃以上の温度域にて合計
圧下率が５０％以上９５％以下の仕上げ圧延を施し、か
つ該圧延中の入側板厚が１０ｍｍ以下となる各スタンド
に強潤滑を施しつつパス圧下率Ｘ（％）が次式 Ｘ≧（４／３）×予想ＴＳ（ｋｇｆ／ｍｍ² ）−３０ の関係を満たす圧延を施し、その後自己焼鈍あるいは均
熱温度７００〜９５０℃に加熱して熱延再結晶化処理を
施すことを特徴とする深絞り性に優れた薄鋼板の製造方
法である。また、本発明は、Ｎｉ：１．５ｗｔ％以下、
Ｃｕ：１．５ｗｔ％以下及びＭｏ：１．５ｗｔ％以下の
１種又は２種以上を含有することを特徴とする深絞り性
に優れた薄鋼板の製造方法である。加えて、本発明は、
上記熱延板再結晶化処理後に、さらに冷間圧延を圧下率
５０〜９５％で施し、引続き７００〜９５０℃の温度域
にて再結晶化焼鈍を施すことを特徴とする深絞り性に優
れた薄鋼板の製造方法でもある。Therefore, the present inventor has completed the present invention by further studying the steel composition, rolling conditions and heat treatment conditions of the material which can obtain the same results as in the case of the strong lubrication of FIG. That is, in the present invention, C: 0.01 wt% or less, Si: 2.0
wt% or less, Mn: 3.0 wt% or less, P: 0.15w
t% or less, S: 0.05 wt% or less, Al: 0.01 to
0.2 wt%, N: 0.01 wt% or less, B: 0.00
01 to 0.0080 wt% and Ti: 0.00
5 to 0.20 wt% Nb: 0.015 to 0.20 wt% of 1 type or 2 types, the balance is a steel material consisting of Fe and unavoidable impurities, and a temperature not lower than Ar ₃ transformation point and not lower than 500 ° C. Finish rolling with a total rolling reduction of 50% or more and 95% or less in the zone, and the pass rolling reduction X (%) is given by the following formula while performing strong lubrication on each stand having an inlet side plate thickness of 10 mm or less during the rolling. Rolling satisfying the relation of X ≧ (4/3) × anticipated TS (kgf / mm ² ) −30, and then performing self-annealing or heating to a soaking temperature of 700 to 950 ° C. for hot rolling recrystallization treatment. Is a method of manufacturing a thin steel sheet having excellent deep drawability. In addition, the present invention is Ni: 1.5 wt% or less,
A method for producing a thin steel sheet having excellent deep drawability, which comprises one or more of Cu: 1.5 wt% or less and Mo: 1.5 wt% or less. In addition, the present invention
After the hot-rolled sheet recrystallization treatment, cold rolling is further performed at a rolling reduction of 50 to 95%, and subsequently recrystallization annealing is performed in a temperature range of 700 to 950 ° C., which is excellent in deep drawability. It is also a method of manufacturing thin steel sheets.

【０００７】本発明では、上記のような条件で鋼鋳片を
圧延するようにしたので、熱延材及び冷延材において、
従来より深絞り性が格段に優れた薄鋼板を製造できるよ
うになる。In the present invention, since the steel slab is rolled under the above-mentioned conditions, in the hot rolled material and the cold rolled material,
It becomes possible to manufacture a thin steel sheet having a far better deep drawability than before.

【０００８】[0008]

【発明の実施の形態】本発明の実施形態は、上記手段を
文字通り実施することであるので、ここでは各成分、仕
上げ圧延条件及び熱処理条件について範囲を限定した理
由を説明する。 １：組成 （１）Ｃ：０．０１ｗｔ％以下 Ｃ量が少ないほど深絞り性は向上するが、０．０１ｗｔ
％以下であれば如何なる値でも悪影響を及ぼさないの
で、このように限定した。BEST MODE FOR CARRYING OUT THE INVENTION The embodiment of the present invention is to literally carry out the above-mentioned means, and therefore the reasons for limiting the ranges of the respective components, finish rolling conditions and heat treatment conditions will be explained here. 1: Composition (1) C: 0.01 wt% or less Deep drawability improves as the C content decreases, but 0.01 wt%
If it is less than or equal to%, any value does not have an adverse effect, so it is limited as described above.

【０００９】（２）Ｓｉ：２．０ｗｔ％以下 所望の強度を得るために含有させる必要があるが、２．
０ｗｔ％以上含有させるとｒ値に悪影響を及ぼすので、
２．０ｗｔ％以下に限定した。 （３）Ｍｎ：３．０ｗｔ％以下 所望の強度を得るために含有させる必要があるが、３．
０ｗｔ％以上含有させるとｒ値に悪影響を及ぼすので、
３．０ｗｔ％以下に限定した。(2) Si: 2.0 wt% or less It is necessary to contain Si in order to obtain desired strength.
Since the r value is adversely affected if the content of 0 wt% or more is included,
It was limited to 2.0 wt% or less. (3) Mn: 3.0 wt% or less It is necessary to contain Mn to obtain a desired strength.
Since the r value is adversely affected if the content of 0 wt% or more is included,
It is limited to 3.0 wt% or less.

【００１０】（４）Ｐ：０．１５ｗｔ％以下 所望の強度を得るために含有させる必要があるが、０．
１５ｗｔ％以上含有させるとｒ値に悪影響を及ぼすの
で、０．１５ｗｔ％以下に限定した。 （５）Ｓ：０．０５ｗｔ％以下、 Ｓ量が少なければ少ないほど深絞り性は向上するが、
０．０５ｗｔ％以下であれば如何なる値でも悪影響を及
ぼさないので、このように限定した。(4) P: 0.15 wt% or less It is necessary to contain P in order to obtain a desired strength.
Since the r value is adversely affected if it is contained in an amount of 15 wt% or more, it is limited to 0.15 wt% or less. (5) S: 0.05 wt% or less, the smaller the amount of S, the better the deep drawability,
Any value of 0.05 wt% or less does not have any adverse effect, so the above limit is set.

【００１１】（６）Ａｌ：０．０１〜０．２ｗｔ％ Ａｌは、溶鋼段階で脱酸を行い、炭窒化物形成成分の歩
留りを向上させるために必要に応じて含有させるもので
あり、その含有量が０．０１ｗｔ％に満たないと効果が
なく、一方、０．２ｗｔ％を越えて含有させても、より
一層の効果は得られないため、０．０１〜０．２ｗｔ％
に限定した。(6) Al: 0.01 to 0.2 wt% Al is added as necessary in order to improve the yield of carbonitride forming components by performing deoxidation in the molten steel stage. If the content is less than 0.01 wt%, there is no effect, while if the content exceeds 0.2 wt%, no further effect can be obtained, so 0.01 to 0.2 wt%
Limited to.

【００１２】（７）Ｎ：０．０１ｗｔ％以下 Ｎ量が少なければ少ないほど深絞り性は向上するが、
０．０１ｗｔ％以下であれば、如何なる値でも悪影響を
及ぼさないので、このように限定した。 （８）Ｂ：０．０００１〜０．００８０ｗｔ％ Ｂは、耐二次加工脆性を改善させるために含有させる
が、その含有量が０．０００１ｗｔ％に満たないと効果
はなく、０．００８０ｗｔ％を超えて含有させると深絞
り性がかえって劣化するので、上記範囲に限定した。(7) N: 0.01 wt% or less Deep drawability improves as the N content decreases, but
If the content is 0.01 wt% or less, any value does not have an adverse effect, so the content is limited as described above. (8) B: 0.0001 to 0.0080 wt% B is contained in order to improve the secondary work embrittlement resistance, but if the content is less than 0.0001 wt%, there is no effect, and 0.0080 wt% If the content is exceeded, the deep drawability rather deteriorates, so the content is limited to the above range.

【００１３】（９）Ｔｉ：０．０１〜０．０５ｗｔ％ 鋼中の固溶Ｃ，Ｎを析出固定して減少し、深絞り性に有
利な｛１１１｝方位を優先的に形成させる効果がある
が、その含有量が０．０１ｗｔ％に満たないと効果はな
く、また０．０５ｗｔ％を超えて含有させても効果はな
い。したがって、０．０１〜０．０５ｗｔ％以下に限定
した。(9) Ti: 0.01 to 0.05 wt% Solid solution C and N in steel is precipitated and fixed to decrease the effect of preferentially forming {111} orientation advantageous to deep drawability. However, if the content is less than 0.01 wt%, there is no effect, and if the content exceeds 0.05 wt%, there is no effect. Therefore, it is limited to 0.01 to 0.05 wt% or less.

【００１４】（１０）Ｎｂ：０．０１５〜０．２０ｗｔ
％ Ｎｂは、本発明において重要な成分であり、鋼中の固溶
Ｃを炭化物として析出固定させて低減し、深絞り性に有
利な｛１１１｝方位の結晶粒を優先的に形成させる効果
がある。また、Ｎｂを含有させることにより仕上げ圧延
前組織が微細化し、熱延板焼鈍後に深絞り性に有利な
｛１１１｝方位の結晶粒を優先的に形成させる効果があ
る。そのためには、その含有量が０．０１５ｗｔ％に満
たないと効果はなく、０．２０ｗｔ％以上含有させても
効果の向上は見られないので、このように限定した。(10) Nb: 0.015 to 0.20 wt
% Nb is an important component in the present invention, and it has the effect of precipitating and fixing the solid solution C in the steel as carbides and reducing it, and preferentially forming crystal grains in the {111} orientation, which is advantageous for deep drawability. is there. Further, the inclusion of Nb has the effect of making the microstructure before finish rolling finer and preferentially forming crystal grains in the {111} orientation, which is advantageous for deep drawability, after annealing the hot-rolled sheet. For that purpose, if the content is less than 0.015 wt%, there is no effect, and even if the content is 0.20 wt% or more, the effect is not improved, so the above limit was made.

【００１５】なお、Ｔｉ及びＮｂの１種又は２種とした
のは、どちらか１方を含有していれば｛１１１｝方位の
結晶粒を優先的に形成するからである。さらに、本発明
では、上記の成分限定に加えて、下記成分をも考慮し
た。 （１１）Ｎｉ：１．５ｗｔ％以下 Ｎｉは、所望の強度を得るために含有してもよいが、
１．５ｗｔ％以上含有させるとｒ値に悪影響を及ぼすの
で、１．５ｗｔ％以下に限定した。The reason for using one or two of Ti and Nb is that crystal grains having a {111} orientation are preferentially formed if either one of Ti and Nb is contained. Furthermore, in the present invention, in addition to the above component limitations, the following components were also considered. (11) Ni: 1.5 wt% or less Ni may be contained in order to obtain a desired strength,
Since the r value is adversely affected if it is contained in an amount of 1.5 wt% or more, it is limited to 1.5 wt% or less.

【００１６】（１２）Ｃｕ：１．５ｗｔ％以下 Ｃｕは、所望の強度を得るために含有してもよいが、
１．５ｗｔ％以上含有させるとｒ値に悪影響を及ぼすの
で、１．５ｗｔ％以下に限定した。 （１３）Ｍｏ：１．５ｗｔ％以下 Ｍｏは、所望の強度を得るために含有してもよいが、
１．５ｗｔ％以上含有させるとｒ値に悪影響を及ぼすの
で、１．５ｗｔ％以下に限定した。(12) Cu: 1.5 wt% or less Cu may be contained in order to obtain a desired strength.
Since the r value is adversely affected if it is contained in an amount of 1.5 wt% or more, it is limited to 1.5 wt% or less. (13) Mo: 1.5 wt% or less Mo may be contained in order to obtain a desired strength,
Since the r value is adversely affected if it is contained in an amount of 1.5 wt% or more, it is limited to 1.5 wt% or less.

【００１７】なお、Ｎｉ，Ｃｕ及びＭｏは、いずれか１
種類の含有でも効果を発揮する。 ２：次に、仕上げ圧延条件及び熱処理条件の限定理由を
説明する。 （１）熱間圧延 熱間仕上圧延をＡｒ₃ 変態点より高い温度域で行うと、
圧延後にオーステナイト（γ）からフェライト（α）へ
変態し、集合組織がランダム化するため、熱延板に｛１
１１｝集合組織が形成されず、そのため冷延焼鈍後には
低いｒ値しか得られない。一方、５００℃未満に仕上圧
延温度を低下させても、より高いｒ値は望めず圧延荷重
が増大するのみであるので、仕上圧延温度はＡｒ₃ 変態
点以下５００℃以上に限定した。Any one of Ni, Cu and Mo can be used.
Effective even with the inclusion of different types. 2: Next, the reasons for limiting the finish rolling conditions and the heat treatment conditions will be described. (1) Hot rolling When hot finish rolling is performed in a temperature range higher than the Ar ₃ transformation point,
After rolling, it transforms from austenite (γ) to ferrite (α) and the texture becomes random.
11} texture is not formed, so that only a low r value is obtained after cold rolling annealing. On the other hand, even if the finish rolling temperature is lowered to less than 500 ° C., a higher r value cannot be expected and only the rolling load increases, so the finish rolling temperature was limited to 500 ° C. or higher below the Ar ₃ transformation point.

【００１８】また、仕上圧延（複数のスタンドでの）の
合計圧下率が５０％に満たないと、熱延板に｛１１１｝
集合組織が形成されず、一方、９５％を越えると、熱延
板にｒ値に好ましくない集合組織が形成するという不都
合が生じるので、５０％以上９５％以下に限定した。ハ
イテンで圧延素材が１０ｍｍ以下の場合、強度に応じて
１パス当たり高圧下率［ Ｘ≧（４／３）×（予想ＴＳ
／Ｋ）−３０ ］とし、仕上圧延すなわちＡｒ₃ 変態点
以下の圧延を潤滑圧延すると、無潤滑圧延に比較して板
厚方向に均一に歪みを蓄積し、かつ同時に表層における
剪断変形の抑制が可能となり、再結晶処理後に｛１１
１｝集合組織が発達するような集合組織が形成される。If the total reduction ratio of finish rolling (in a plurality of stands) is less than 50%, the hot-rolled sheet will have {111}.
No texture is formed. On the other hand, if it exceeds 95%, there is a disadvantage that an unfavorable texture is formed in the hot-rolled sheet, so the content is limited to 50% or more and 95% or less. When the rolling material is 10 mm or less in high tensile strength, the high-pressure reduction rate per pass [X ≧ (4/3) × (estimated TS
/ K) -30] and finish rolling, that is, rolling less than the Ar ₃ transformation point is lubricated, as compared with non-lubricated rolling, strain is uniformly accumulated in the plate thickness direction, and at the same time, shear deformation in the surface layer is suppressed. It becomes possible, after recrystallization treatment {11
1} A texture is formed so that the texture develops.

【００１９】軟鋼の場合、従来よりも１パス当たり低圧
下率で圧延素材が１０ｍｍ以下においてのみ仕上圧延す
なわちＡｒ₃ 変態点以下の圧延を潤滑圧延すると、ロー
ルと鋼板との間の摩擦力に起因する剪断変形が抑制可能
となり、高ｒ値が得られる。したがって、深絞り性を確
保するために、本発明では、積極的に強潤滑圧延するこ
とを採用した。ここでの強潤滑圧延とは、ロールと鋼板
表面の摩擦係数が０．１５未満、より好ましくは０．１
０未満である。In the case of mild steel, if the finish rolling, that is, the rolling having the Ar ₃ transformation point or less is lubricated and rolled only at a low pressure reduction rate per pass of less than 10 mm, a frictional force between the roll and the steel sheet is caused. It is possible to suppress the shear deformation due to the high r value. Therefore, in order to secure the deep drawability, in the present invention, the strongly lubricating rolling is positively adopted. The strong lubrication rolling here means that the coefficient of friction between the roll and the surface of the steel sheet is less than 0.15, more preferably 0.1.
It is less than 0.

【００２０】ここに、上記の仕上圧延前の工程について
は、特に限定をするものではなく、例えば圧延素材につ
いては、連続鋳造スラブを再加熱又は連続鋳造後、Ａｒ
₃ 変態点以下に降温することなく直ちに、又は保温処理
したものを粗圧延にてシートバーにしたものを使用する
のが好適である。また、潤滑剤は、例えば合成エステル
油、鉱物油等が挙げられるが、特に限定するものではな
い。Here, the above-mentioned steps before finish rolling are not particularly limited. For example, for a rolled material, after continuously heating or continuously heating the continuously cast slab, Ar
_It is preferable to use a sheet bar that has been subjected to a heat-insulating process immediately or without being cooled to a temperature not higher than ₃ transformation points and then rough-rolled into a sheet bar. Examples of the lubricant include synthetic ester oil and mineral oil, but are not particularly limited.

【００２１】なお、本願の実施には、ＴＳを予め予測す
る必要があるが、本願適用鋼の強度は通常固溶強化が支
配的因子であるため、成分から計算される予測強度、ま
たは、同一成分の鋼を予め通常工程で冷延焼鈍板とした
際の実測強度を用いればよい。本願における実施例の強
度は、全て後者により（ＳＲＴ １２００℃、ＦＤＴ９
００℃、冷延圧下率８０％、焼鈍温度 ８３０℃）求め
たものである。In order to carry out the present invention, it is necessary to predict the TS in advance, but since the strength of the steel to which the present invention is applied is usually dominated by solid solution strengthening, the predicted strength calculated from the components or the same strength. It is sufficient to use the measured strength when the component steels are previously cold-rolled and annealed in the normal process. The strengths of all the examples in the present application are (SRT 1200 ° C., FDT 9
00 ° C., cold rolling reduction 80%, annealing temperature 830 ° C.).

【００２２】（２）熱延板再結晶化の焼鈍条件 本発明の鋼は、熱延終了温度がＡｒ₃ 変態点以下である
ため、圧延板は加工組織を呈している。そのため、この
鋼板には次いで再結晶化処理を施して｛１１１｝方位の
結晶粒を形成させる必要がある。再結晶化処理を施さな
いと、圧延板に｛１１１｝集合組織は発達せず、熱延板
のｒ値は低く、したがって、最終の冷延焼鈍板のｒ値も
低くなるので、本発明では上記のように限定する。焼鈍
温度が７００℃より低い場合、再結晶組織は未発達であ
り、９５０℃より高い温度で焼鈍を施すと、変態過程を
経るためｒ値が低下する。(2) Annealing condition for recrystallization of hot-rolled sheet Since the hot-rolling end temperature of the steel of the present invention is not higher than the Ar ₃ transformation point, the rolled sheet has a work structure. Therefore, it is necessary to subsequently subject this steel sheet to recrystallization treatment to form crystal grains of {111} orientation. If the recrystallization treatment is not performed, the {111} texture does not develop in the rolled sheet, the r value of the hot rolled sheet is low, and therefore the r value of the final cold rolled annealed sheet is also low. Limit as above. If the annealing temperature is lower than 700 ° C., the recrystallization structure is undeveloped, and if annealing is performed at a temperature higher than 950 ° C., a transformation process will occur and the r value will decrease.

【００２３】なお、該再結晶化は、熱延板を７００℃以
上で巻取るだけでも行われるので、本発明では、それを
自己焼鈍と称した。以上述べた熱間圧延及び再結晶化処
理で所望の深絞り性に優れた薄鋼板が得られるが、本発
明では、さらに該熱延板を下記条件で冷間圧延及び焼鈍
を追加することで、一層深絞り性に優れた薄鋼板を製造
可能とした。Since the recrystallization is performed only by winding the hot-rolled sheet at 700 ° C. or higher, it is referred to as self-annealing in the present invention. Although a thin steel sheet excellent in desired deep drawability can be obtained by the hot rolling and the recrystallization treatment described above, in the present invention, the hot rolled sheet is further subjected to cold rolling and annealing under the following conditions. It has become possible to manufacture thin steel sheets with even better deep drawability.

【００２４】（３）冷間圧延 この工程は、高いｒ値を得るためには必要不可欠であ
り、本発明では、上記条件で得た熱延焼鈍板を、さらに
圧下率５０〜９５％で冷間圧延を行うようにした。該圧
下率の増加と共に、冷延焼鈍板のｒ値は向上するが、圧
下率９５％以上で冷間圧延を行うとｒ値はかえって劣化
するので、このように限定する。(3) Cold rolling This step is indispensable for obtaining a high r value, and in the present invention, the hot rolled annealed sheet obtained under the above conditions is further cooled at a rolling reduction of 50 to 95%. It was made to carry out hot rolling. The r value of the cold rolled annealed sheet is improved with the increase of the rolling reduction, but the r value is rather deteriorated when cold rolling is performed at a rolling reduction of 95% or more.

【００２５】（４）冷延板の焼鈍条件 加工組織となっている上記冷延板に、７００〜９５０℃
で焼鈍を施すことによって｛１１１｝再結晶集合組織が
発達し、高いｒ値が得られる。焼鈍温度が７００℃より
低い場合、再結晶組織は未発達であり、ｒ値は低い。ま
た、９５０℃より高い温度で焼鈍を施すと、冷却過程に
おいてオーステナイトからフェライトへの変態を生じる
ために｛１１１｝再結晶集合組織はランダム化し、低い
ｒ値しか得られない。特に、ＮｂＣが（Ｎｂ＋Ｃ）に分
解する温度域８３０〜９００℃が望ましく、ｒ値に好ま
しい｛１１１｝集合組織を形成後、固溶Ｃが生じるた
め、格段に優れた深絞り性が得られるのである。(4) Annealing Conditions for Cold Rolled Sheet The cold rolled sheet having a work structure is 700 to 950 ° C.
The {111} recrystallized texture is developed by annealing at 1, and a high r value is obtained. When the annealing temperature is lower than 700 ° C, the recrystallization structure is underdeveloped and the r value is low. Further, when annealing is performed at a temperature higher than 950 ° C., a transformation from austenite to ferrite occurs in the cooling process, so that the {111} recrystallization texture is randomized and only a low r value can be obtained. In particular, a temperature range of 830 to 900 ° C. in which NbC decomposes into (Nb + C) is desirable, and after solid solution C is formed after forming a {111} texture that is favorable for the r value, remarkably excellent deep drawability can be obtained. is there.

【００２６】[0026]

【実施例】表１に、本発明及び比較例で素材として使用
した鋼鋳片の組成を示す。表１には、本発明の範囲を外
れる値には下線を付して比較例であることを明示してあ
る。これらの鋳片を熱間で粗圧延し、表２に示す条件の
熱間仕上げ圧延、熱延板焼鈍、冷間圧延、そして冷延板
焼鈍を施し、その結果得た熱延及び冷延鋼板の材料特性
を引張試験により求めてｒ値等を表２に同時に示した。
なお、ｒ値の測定時、引張予歪みを１５％とし、３点法
により求め、Ｌ方向（圧延方向）、Ｄ方向（圧延方向と
４５度）そしてＣ方向（圧延方向と垂直）のｒ値を、ｒ
値＝（ｒＬ＋２ｒＤ＋ｒＣ）／４を用いて演算した。EXAMPLES Table 1 shows the composition of the steel slabs used as raw materials in the present invention and comparative examples. In Table 1, values outside the range of the present invention are underlined to clearly show that they are comparative examples. These slabs were roughly hot-rolled, hot-finish rolling under the conditions shown in Table 2, hot-rolled sheet annealing, cold rolling, and cold-rolled sheet annealing, and the resulting hot-rolled and cold-rolled steel sheets were obtained. The material properties of No. 1 were obtained by a tensile test, and r values and the like are shown in Table 2 at the same time.
When measuring the r value, the tensile prestrain was set to 15%, and the value was determined by the three-point method. The r value in the L direction (rolling direction), the D direction (45 ° with the rolling direction), and the C direction (perpendicular to the rolling direction). To r
Calculation was performed using the value = (rL + 2rD + rC) / 4.

【００２７】表２から明らかなように、本発明の条件下
においては、比較例（☆印）に比して優れた深絞り特性
が得られている。なお、表２のＮｏ．１〜２０までの圧
延における入側厚１０ｍｍ以下の全パス圧下率を表３に
一括して示しておく。As is clear from Table 2, under the conditions of the present invention, excellent deep drawing characteristics were obtained as compared with the comparative example (marked with *). In addition, in Table 2, No. Table 3 collectively shows the reduction ratios of all passes having an entrance side thickness of 10 mm or less in rolling from 1 to 20.

【００２８】[0028]

【表１】 [Table 1]

【００２９】[0029]

【表２】 [Table 2]

【００３０】[0030]

【表３】 [Table 3]

【００３１】[0031]

【発明の効果】本発明によれば、鋼成分及び製造条件を
限定することにより、ＴＳ ４０ｋｇｆ／ｍｍ² 以上、
特に５０ｋｇｆ／ｍｍ² 以上のハイテンにおいては、強
度に応じた高圧下率（１パス当たり）をとることによ
り、従来より高ｒ値化が可能となる。軟鋼においては、
従来考えられていたより（１パス当たり）低圧下率で、
しかも入側１０ｍｍ以下においてのみ潤滑を施すことで
十分高ｒ値が確保でき、低コスト、低エネルギで従来よ
りも格段に優れた深絞り性を有する薄鋼板の製造が可能
となる。According to the present invention, TS 40 kgf / mm ² or more,
In particular, in the case of high tensile strength of 50 kgf / mm ² or more, a high r value can be obtained as compared with the conventional one by taking a high pressure reduction rate (per pass) according to the strength. In mild steel,
At lower pressure ratio (per pass) than previously thought,
Moreover, by providing lubrication only on the entry side of 10 mm or less, a sufficiently high r value can be secured, and it becomes possible to manufacture a thin steel sheet having low cost, low energy, and far more excellent deep drawability than ever before.

【図面の簡単な説明】[Brief description of drawings]

【図１】仕上圧延の圧下率と熱延板のｒ値との関係を示
す図である。FIG. 1 is a diagram showing a relationship between a reduction ratio of finish rolling and an r value of a hot rolled sheet.

フロントページの続き (51)Int.Cl.⁶ 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/16 Ｃ２２Ｃ 38/16 (72)発明者 坂田 敬 千葉市中央区川崎町１番地 川崎製鉄株式 会社技術研究所内 (72)発明者 加藤 俊之 千葉市中央区川崎町１番地 川崎製鉄株式 会社技術研究所内Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location C22C 38/16 C22C 38/16 (72) Inventor Takashi Sakata 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Co., Ltd. (72) Inventor Toshiyuki Kato 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Technical Research Institute

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】 Ｃ：０．０１ｗｔ％以下、 Ｓｉ：２．０ｗｔ％以下、 Ｍｎ：３．０ｗｔ％以下、 Ｐ：０．１５ｗｔ％以下、 Ｓ：０．０５ｗｔ％以下、 Ａｌ：０．０１〜０．２ｗｔ％、 Ｎ：０．０１ｗｔ％以下、 Ｂ：０．０００１〜０．００８０ｗｔ％ を含み、且つ Ｔｉ：０．００５〜０．２０ｗｔ％ Ｎｂ：０．０１５〜０．２０ｗｔ％ の１種又は２種を含有し，残部はＦｅ及び不可避的不純
物よりなる鋼素材に、 Ａｒ₃ 変態点以下、５００℃以上の温度域にて合計圧下
率が５０％以上９５％以下の仕上げ圧延を施し、かつ該
圧延中の入側板厚が１０ｍｍ以下となる各スタンドに強
潤滑を施しつつパス圧下率Ｘ（％）が次式 Ｘ≧（４／３）×予想ＴＳ（ｋｇｆ／ｍｍ² ）−３０ の関係を満たす圧延を施し、その後自己焼鈍あるいは均
熱温度７００〜９５０℃に加熱して熱延板再結晶化処理
を施すことを特徴とする深絞り性に優れた薄鋼板の製造
方法。1. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, P: 0.15 wt% or less, S: 0.05 wt% or less, Al: 0.01 -0.2 wt%, N: 0.01 wt% or less, B: 0.0001-0.0080 wt% and Ti: 0.005-0.20 wt% Nb: 0.015-0.20 wt% 1 The steel material containing one or two kinds and the balance Fe and unavoidable impurities is subjected to finish rolling with a total reduction of 50% or more and 95% or less at a temperature range of Ar ₃ transformation point or less and 500 ° C. or more. And the pass reduction rate X (%) is given by the following formula X ≧ (4/3) × estimated TS (kgf / mm ² ) -30 while applying strong lubrication to each stand where the entrance side plate thickness during rolling is 10 mm or less. Rolling that satisfies the relationship of A method for producing a thin steel sheet excellent in deep drawability, which comprises subjecting a hot-rolled sheet recrystallization treatment to heating at a temperature of 700 to 950 ° C. 【請求項２】 Ｎｉ：１．５ｗｔ％以下、Ｃｕ：１．５
ｗｔ％以下及びＭｏ：１．５ｗｔ％以下の１種又は２種
以上を含有することを特徴とする請求項１記載の深絞り
性に優れた薄鋼板の製造方法。2. Ni: 1.5 wt% or less, Cu: 1.5
The method for producing a thin steel sheet excellent in deep drawability according to claim 1, characterized in that the steel sheet contains one or two or more of wt% or less and Mo: 1.5 wt% or less. 【請求項３】 上記熱延板再結晶化処理後に、さらに冷
間圧延を圧下率５０〜９５％で施し、引続き７００〜９
５０℃の温度域にて再結晶化焼鈍を施すことを特徴とす
る請求項１又は２記載の深絞り性に優れた薄鋼板の製造
方法。3. After the hot-rolled sheet recrystallization treatment, cold rolling is further performed at a rolling reduction of 50 to 95%, and then 700 to 9 is continued.
The method for producing a thin steel sheet having excellent deep drawability according to claim 1 or 2, wherein recrystallization annealing is performed in a temperature range of 50 ° C.