JP2860438B2 - Manufacturing method of high-strength thin steel sheet with extremely excellent workability - Google Patents
Manufacturing method of high-strength thin steel sheet with extremely excellent workabilityInfo
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- JP2860438B2 JP2860438B2 JP28150991A JP28150991A JP2860438B2 JP 2860438 B2 JP2860438 B2 JP 2860438B2 JP 28150991 A JP28150991 A JP 28150991A JP 28150991 A JP28150991 A JP 28150991A JP 2860438 B2 JP2860438 B2 JP 2860438B2
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- Heat Treatment Of Sheet Steel (AREA)
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Description
【０００１】[0001]
【産業上の利用分野】本発明は自動車用等に使用される
極めて加工成形性に優れた高強度薄鋼板の製造方法に係
わる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength steel sheet having excellent workability and being used for automobiles and the like.
【０００２】[0002]
【従来の技術】近年、自動車の軽量化が再び注目をあび
ている。最初の軽量化の引金は石油ショックであった。
化石燃料の枯渇への危機感があらゆる分野で省エネルギ
ーを促進した。自動車も例外ではなく、そのため多くの
努力が行われた。使用鋼板の軽量化のため多くの高強度
薄鋼板（ハイテン）が開発された。2. Description of the Related Art In recent years, attention has been paid to lightening of automobiles again. The first lightening trigger was the oil shock.
The sense of danger of fossil fuel depletion has promoted energy conservation in all areas. The car was no exception, and much effort was put into it. Many high-strength steel sheets (HITEN) have been developed to reduce the weight of the steel sheets used.
【０００３】最近の軽量化の背景はこれとはやや趣を異
にしている。アメリカでの燃費規制法案に代表される地
球規模の環境問題、特に温暖化対策としての二酸化炭素
の低減が背景にあり、単なる経済問題にとどまらない。
すなわち、何がなんでも軽量化が必要という状況になっ
た。このような環境の中、自動車材料として希求される
ものは耐久強度、一発強度、あるいは溶接強度といった
強さと、何にでも成形可能な加工成形性である。しかし
ながら、この両者は通常相反する性格を持っており両立
は困難なことであった。[0003] The background of recent weight reduction is somewhat different from this. It is not just an economic problem because of the background of global environmental problems typified by the fuel efficiency regulation bill in the United States, especially the reduction of carbon dioxide as a measure against global warming.
In other words, it became necessary to reduce the weight of anything. In such an environment, what is desired as an automobile material is strength such as durability strength, one-shot strength or welding strength, and workability that can be formed into anything. However, the two usually had conflicting characteristics, and it was difficult to achieve both.
【０００４】それでも薄鋼板の世界では過去幾多の開発
がなされてきている。有名なものにフェライトとマルテ
ンサイトの混合組織からなるいわゆるデュアルフェイズ
鋼がある。例えば、特公昭５６−１１７４１号公報など
に提案されている。このデュアルフェイズ鋼はそれまで
のハイテン材に比べ大幅に加工性を改良したが、それで
も軟鋼板にとって代わるというわけには行かず、その使
用範囲は限られている。Nevertheless, in the world of thin steel sheets, many developments have been made in the past. A famous one is a so-called dual phase steel made of a mixed structure of ferrite and martensite. For example, it is proposed in Japanese Patent Publication No. 56-11741. Although this dual-phase steel has significantly improved workability compared to previous high-tensile steels, it still does not replace mild steel and its use is limited.
【０００５】本発明は鋼中にオーステナイトを残留させ
ることで強度を高めかつ飛躍的に加工成形性を向上させ
ようとするものであるが、このようなオーステナイト相
を残留させることで高伸びを得ようとすること自体は、
低合金鋼においても公知である。特公昭５８−４２２４
６号公報には０．４〜０．８５％Ｃ−Ｓｉ−Ｍｎ鋼を用
いた技術が開示されている。しかし、この技術は高炭素
鋼を用いており、溶接が困難である、強度が１、０００
Ｎ／ｍｍ2 以上あり、加工性が軟鋼板に代替可能なほど
はよくない、局部変形能が劣る等々といった欠点を有し
ている。さらには特開昭６１−１５７６２５号公報記載
の技術がある。しかしこの技術もまた、比較的高炭素鋼
であり、成形加工性のレベルも十分とは言えない。[0005] The present invention aims to increase the strength by drastically improving the workability by leaving austenite in steel, but it is possible to obtain high elongation by leaving such austenite phase. The attempt itself is
It is also known for low alloy steels. Japanese Patent Publication No. 58-4224
No. 6 discloses a technique using 0.4-0.85% C-Si-Mn steel. However, this technique uses high carbon steel, is difficult to weld, and has a strength of 1,000.
N / mm 2 or more, and has drawbacks such as workability is not good enough to be replaced with mild steel sheet, local deformability is inferior, and the like. Further, there is a technique described in JP-A-61-157625. However, this technology is also a relatively high-carbon steel, and the level of formability is not sufficient.
【０００６】本発明は以上のような問題点を克服し、可
溶接でしかも破断伸びのみならず、局部伸び、すなわち
局部変形能にも優れた総合成形加工性を有し、さらにま
た製造の安定性をも確保している。なお、本発明の類似
成分の鋼、特に高Ａｌ含有鋼を用いた技術として、特公
昭５８−１０４４４号、特公昭６２−１８６０６号、お
よび特開平２−５０９１０号の各公報記載の技術があ
る。しかし、最初の技術は厚板の耐水素誘起割れ性を問
題としており、そこでのＡｌ添加は単にキルド鋼の脱酸
のためであり、実施例も高々０．０６２％の添加にとど
まる。次の技術は薄鋼板に関するものであるが、ランク
フォード値向上を目的としたもので、Ａｌはγ／α変態
点を高める目的で添加されており、本発明のような高強
度高延性を狙ったものではなく、また、炭素量も低い。
さらに３つ目の技術は熱疲労特性の向上を目的としてお
り、Ｃｒ、Ｍｏ添加鋼をベースとしている。いずれも本
発明とは直接関係しない。The present invention overcomes the above-mentioned problems, and has an overall formability that is weldable and has excellent local elongation, that is, local deformability, as well as elongation at break. The sex is also secured. In addition, as a technique using a steel having a similar component of the present invention, particularly a steel having a high Al content, there are techniques described in JP-B-58-10444, JP-B-62-18606, and JP-A-2-50910. . However, the first technique is concerned with the resistance to hydrogen-induced cracking of the thick plate, in which Al addition is merely for the deoxidation of the killed steel, and the example is limited to at most 0.062%. The following technology relates to a thin steel sheet, but is aimed at improving the Rankford value. Al is added for the purpose of increasing the γ / α transformation point, and aims at high strength and high ductility as in the present invention. And the carbon content is low.
The third technique is aimed at improving thermal fatigue properties and is based on Cr and Mo added steel. Neither is directly related to the present invention.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、低炭素、低
合金鋼の範囲で、残留オーステナイト相を確保すること
で強度と加工成形性を兼備した高強度薄鋼板を安定して
製造することを課題とする。すなわち、本発明は特性値
としては引張強度５９０Ｎ／ｍｍ2 級から７８５Ｎ／ｍ
ｍ2 級で、伸び３０％以上、穴拡げ比１．４以上を有す
る薄鋼板の製造方法の提供を課題とする。なお、ここで
穴拡げ比とは、局部変形能を表す指標である。SUMMARY OF THE INVENTION It is an object of the present invention to stably produce a high-strength thin steel sheet having both strength and workability by securing a retained austenite phase in the range of low carbon and low alloy steels. As an issue. That is, in the present invention, the characteristic value is from tensile strength 590 N / mm 2 class to 785 N / m 2.
It is an object of the present invention to provide a method for producing a thin steel sheet having an elongation of 30% or more and a hole expansion ratio of 1.4 or more in m 2 class. Here, the hole expansion ratio is an index representing local deformability.
【０００８】[0008]
【課題を解決するための手段】本発明の課題解決のため
の手段の特徴としては、成分とりわけＡｌ添加量を中心
とした調整と独自の熱処理条件にある。すなわち、本発
明の要旨とするところは、下記のとおりである。 （１）Ｃ：０．０８〜０．３０％、Ｍｎ：１．０〜２．
０％、Ｓｉ：０．５〜２．５％、Ａｌ：０．５〜１．５
％を含有し、残部Ｆｅおよび不可避的不純物からなる鋼
を熱延した後、７３０〜９００℃に１０〜３００秒加熱
し、続いて６６０〜７２０℃まで１０℃／ｓｅｃ以下で
冷却し、その後３０℃／ｓｅｃ以上で３５０〜４５０℃
まで急冷し、その温度で１〜１０分保持することを特徴
とする加工性の極めて優れた高強度薄鋼板の製造方法 （２）Ｃ：０．０８〜０．３０％、Ｍｎ：１．０〜２．
０％、Ｓｉ：０．５〜２．５％、Ａｌ：０．５〜１．５
％を含有し、さらにＣａ、Ｍｇ、ＲＥＭ、Ｚｒの１種以
上を合計で０．００１〜０．０５％含み、残部Ｆｅおよ
び不可避的不純物からなる鋼を熱延した後、７３０〜９
００℃に１０〜３００秒加熱し、続いて６６０〜７２０
℃まで１０℃／ｓｅｃ以下で冷却し、その後３０℃／ｓ
ｅｃ以上で３５０〜４５０℃まで急冷し、その温度で１
〜１０分保持することを特徴とする加工性の極めて優れ
た高強度薄鋼板の製造方法。The features of the means for solving the problems of the present invention are the adjustment centering on the addition amount of the components, especially the added amount of Al, and the unique heat treatment conditions. That is, the gist of the present invention is as follows. (1) C: 0.08 to 0.30%, Mn: 1.0 to 2.
0%, Si: 0.5 to 2.5%, Al: 0.5 to 1.5
%, The steel consisting of the balance Fe and unavoidable impurities is hot-rolled, heated to 730 to 900 ° C. for 10 to 300 seconds, then cooled to 660 to 720 ° C. at 10 ° C./sec or less, and then cooled to 30 ° C./sec. 350-450 ° C at ℃ / sec or more
(2) C: 0.08 to 0.30%, Mn: 1.0, characterized in that it is rapidly cooled to a temperature and maintained at that temperature for 1 to 10 minutes. ~ 2.
0%, Si: 0.5 to 2.5%, Al: 0.5 to 1.5
%, Further contains at least one of Ca, Mg, REM, and Zr in an amount of 0.001 to 0.05%, and after hot-rolling steel consisting of Fe and unavoidable impurities, 730 to 9
Heat to 00 ° C. for 10-300 seconds, followed by 660-720
Cool to 10 ° C / sec or less, then 30 ° C / s
The temperature is rapidly cooled to 350 to 450 ° C. at
A method for producing a high-strength thin steel sheet having extremely excellent workability, characterized by holding for 10 to 10 minutes.
【０００９】（３） 前記出発鋼を熱延し、さらに冷延
した後、７３０〜９００℃に１０〜３００秒加熱し、続
いて６６０〜７２０℃まで１０℃／ｓｅｃ以下で冷却
し、その後３０℃／ｓｅｃ以上で３５０〜４５０℃まで
急冷し、その温度で１〜１０分保持することを特徴とす
る前項１または２記載の加工性の極めて優れた高強度薄
鋼板の製造方法。(3) The starting steel is hot-rolled and further cold-rolled, heated to 730 to 900 ° C. for 10 to 300 seconds, and then cooled to 660 to 720 ° C. at 10 ° C./sec or less, and then cooled to 30 ° C./sec. 3. The method for producing a high-strength thin steel sheet having extremely excellent workability according to the above item 1 or 2, wherein the steel sheet is rapidly cooled to 350 to 450 ° C. at a temperature of at least 30 ° C./sec and maintained at that temperature for 1 to 10 minutes.
【００１０】[0010]
【作用】次に個々の構成要件の作用および数値限定理由
について述べる。 Ｃ：Ｃは残留オーステナイト相生成のためには重要な元
素で、０．０８％未満では十分な量の残留オーステナイ
トが得られず、そのため強度も加工性も所定の域まで達
しない。この意味でＣ量は高い方がよいが、０．３０％
を超えると溶接性が極度に劣化し、スポット溶接ですら
極めて困難になる。そのため０．３０％を上限とした。
より好ましくは０．１０〜０．２０％の範囲とすべきで
ある。Next, the operation of each component and the reason for limiting the numerical values will be described. C: C is an important element for formation of a retained austenite phase, and if it is less than 0.08%, a sufficient amount of retained austenite cannot be obtained, so that neither strength nor workability reaches a predetermined range. In this sense, the higher the C content, the better, but 0.30%
If it exceeds, the weldability is extremely deteriorated, and even spot welding becomes extremely difficult. Therefore, the upper limit is 0.30%.
More preferably, it should be in the range of 0.10 to 0.20%.
【００１１】Ｍｎ：Ｍｎはある程度の焼入れ性を付与さ
せるため添加する必要がある。その範囲は１．０〜２．
０％である。Ｍｎ量が下限値未満では本発明の熱処理条
件を採っても十分な残留オーステナイト相を得ることが
困難であり、一方、２．０％を超えると急冷後の変態が
遅滞し、所望の組織が得られず、やはり十分な量の残留
オーステナイトが得られない。Mn: Mn needs to be added in order to impart some hardenability. The range is 1.0 to 2.
0%. If the Mn content is less than the lower limit, it is difficult to obtain a sufficient retained austenite phase even under the heat treatment conditions of the present invention, while if it exceeds 2.0%, the transformation after quenching is delayed, and the desired structure cannot be obtained. However, a sufficient amount of retained austenite cannot be obtained.
【００１２】Ｓｉ：Ｓｉは、低合金鋼で４００℃付近の
保持にて残留オーステナイトを得るのに重要な作用をお
よぼすと考えられている。おそらくこの温度付近での変
態時にセメンタイトの析出を抑え、オーステナイトを安
定化させるためと考えられる。このようなＳｉの作用
は、本発明の条件にあっては０．５％未満では発現せ
ず、一方２．５％付近で効果は飽和し、これを超える添
加はいたずらに経済性を損なうだけであり、より好まし
くは０．７〜２．０％とすべきである。Si: Si is considered to play an important role in obtaining retained austenite in a low alloy steel at a temperature of about 400 ° C. Probably because of suppressing the precipitation of cementite at the time of transformation near this temperature and stabilizing austenite. Under the conditions of the present invention, such an effect of Si does not appear at less than 0.5%, while the effect saturates at around 2.5%, and an addition exceeding this only unnecessarily impairs economic efficiency. And more preferably 0.7 to 2.0%.
【００１３】Ａｌ：Ａｌの添加は従来の残留オーステナ
イトを含む薄鋼板の場合と決定的に異なる。Ｃ、Ｓｉ、
Ｍｎ量の特定に加え、このＡｌの添加と特定熱処理条件
の組合せが本発明の効果を発現させる。その効果のメカ
ニズムは必ずしも明かではないが、おそらく残留オース
テナイトの安定度に関係しているものと考えられる。す
なわち、本発明は単に変態誘起超塑性効果（ＴＲＩＰ：
ＴＲＡＮＳＦＯＲＭＡＴＩＯＮ ＩＮＤＵＣＥＤ ＰＬ
ＡＳＴＩＳＩＴＹ効果）にとどまらず、より安定なγ相
が混在することで局部伸びも大幅に向上せしめているも
のと考えられる。また、製造条件の変動に対する安定に
も寄与しているものと考えられる。こういったＡｌ添加
の効果は、０．５％未満では発揮されず、他方１．５％
を超える添加は、鋼のＡｒ3 変態点を上昇させ熱延を困
難にするので、その添加量を０．５〜１．５％の添加と
した。より好ましくは０．７％以上添加すべきである。Al: The addition of Al is crucially different from conventional thin steel sheets containing retained austenite. C, Si,
In addition to specifying the amount of Mn, the combination of the addition of Al and the specific heat treatment conditions brings about the effects of the present invention. The mechanism of the effect is not always clear, but is probably related to the stability of retained austenite. In other words, the present invention simply provides the transformation-induced superplastic effect (TRIP:
TRANSFORMATION INDUCED PL
It is considered that the local elongation is greatly improved by not only the ASTISITY effect) but also the more stable γ phase being mixed. Further, it is considered that this also contributes to stability against fluctuations in manufacturing conditions. The effect of such Al addition is not exhibited at less than 0.5%, while the effect of 1.5%
If the addition exceeds 0.5%, the Ar 3 transformation point of the steel is increased and hot rolling becomes difficult. More preferably, it should be added at 0.7% or more.
【００１４】鋼の局部延性には、介在物とりわけ長く伸
びたＡ系介在物もまた大いに悪影響をおよぼす。この意
味でこのＡ系介在物を極小化することが望ましい。その
ためにはＳを０．００５％未満に限定して硫化物系介在
物を減少させるとともに、Ｃａ、Ｍｇ、ＲＥＭ、Ｚｒの
１種以上を合計で０．００１〜０．０５％含む必要があ
る。これらの元素は鋼中Ｓと結び付き熱間圧延にて伸び
にくい、すなわち熱間可塑性の少ない硫化物を作り、Ａ
系介在物を減少させる。これら元素は１種以上を合計で
０．００１％以上添加しないと効果はなく、他方０．０
５％を超える添加はかえって鋼の清浄度を劣化させ、鋼
の延性を損なう。[0014] Inclusions, especially elongated A-type inclusions, also have a significant adverse effect on the local ductility of steel. In this sense, it is desirable to minimize the A-based inclusion. For that purpose, it is necessary to reduce S to less than 0.005% to reduce sulfide-based inclusions and to include at least one of Ca, Mg, REM, and Zr in a total amount of 0.001 to 0.05%. . These elements are combined with S in steel and hardly stretched by hot rolling, that is, sulfides having low hot plasticity are formed, and A
Reduce system inclusions. These elements have no effect unless at least one of them is added in a total amount of 0.001% or more.
Addition exceeding 5% rather deteriorates the cleanliness of the steel and impairs the ductility of the steel.
【００１５】このようにして溶製した鋼は熱延される。
熱延条件は特に限定するところではない。熱延コイルは
所望板厚が薄い時、あるいはより板厚精度の必要な場合
等には、さらに冷延される。続く熱処理条件は本発明を
得るための熱処理を行うところであり、これまた極めて
重要である。The steel thus melted is hot-rolled.
The hot rolling conditions are not particularly limited. The hot-rolled coil is further cold-rolled when the desired plate thickness is small, or when higher plate thickness accuracy is required. The subsequent heat treatment conditions are where the heat treatment for obtaining the present invention is performed, and this is also extremely important.
【００１６】熱延あるいは場合によっては冷延された鋼
は、まずα相／γ相の共存領域である７３０〜９００℃
に加熱されなければならない。加熱温度が７３０℃未満
ではγ相が十分得られず、γ相からの変態を利用する本
発明では所定の特性が得られない。加熱温度の上限は９
００℃である。この温度を超えるとγ相の体積率が増え
すぎて、次の徐冷中にも適正なγ相の体積率に調整する
ことが困難である。また、加熱保持時間については１０
秒未満では十分なγ化が達成されず、他方３００秒程度
でγ化は飽和するので、経済性も考え上限は３００秒と
した。The hot-rolled or cold-rolled steel is first heated to 730 to 900 ° C., which is a region where α / γ coexists.
Must be heated. If the heating temperature is lower than 730 ° C., the γ phase cannot be sufficiently obtained, and the present invention utilizing the transformation from the γ phase cannot obtain the predetermined characteristics. The upper limit of the heating temperature is 9
00 ° C. If the temperature is exceeded, the volume ratio of the γ phase is too large, and it is difficult to adjust the volume ratio of the γ phase to an appropriate volume ratio during the next slow cooling. The heating and holding time is 10
If the time is less than seconds, sufficient gamma-ization cannot be achieved, while the gamma-saturation will be saturated in about 300 seconds.
【００１７】この後、６６０〜７２０℃まで１０℃／ｓ
ｅｃ以下で徐冷する。これは適正なγ相／α相比率を得
るための重要な処理である。１０℃／ｓｅｃを超える急
冷では適正な比率を得られないばかりか、加熱保持温度
の変動がそのまま材質変動となるのでバラツキの原因と
なる。徐冷温度区間が７２０℃より高いとγ相の成分濃
縮が十分でなく、また６６０℃未満まで徐冷すると、γ
相がパーライト等好ましくない組織になるので徐冷・急
冷変更点は６６０〜７２０℃の範囲内とした。Thereafter, the temperature is increased to 660 to 720 ° C. by 10 ° C./s.
Cool slowly below ec. This is an important process for obtaining a proper γ phase / α phase ratio. A rapid cooling exceeding 10 ° C./sec not only does not provide an appropriate ratio, but also causes a variation because a change in the heating holding temperature directly changes the material. If the slow cooling temperature section is higher than 720 ° C., the component concentration of the γ phase is not sufficient.
Since the phase becomes an unfavorable structure such as pearlite, the slow cooling / rapid cooling change point is set in the range of 660 to 720 ° C.
【００１８】こうして得られた適正にγ／α分離した組
織中のγ相を４００℃付近で変態させるため３０℃／ｓ
ｅｃ以上で急冷する。急冷速度が３０℃／ｓｅｃ未満で
はやはりγ相がパーライト等好ましくない組織に変態す
る。急冷後の保持条件は、３５０〜４５０℃の温度域で
１〜１０分でなければならない。本発明鋼の場合、第１
段の徐冷中に成分調整されたγ相を、この保持中にベイ
ナイト相に変態させた際に一部残留したオーステナイト
相が極めて安定になり、製品の状態でもそのままオース
テナイトとして残留するものと考えられる。したがって
γ相を適当にベイナイト変態させることが本発明では重
要である。保持温度が３５０℃未満では過剰のマルテン
サイト相が生じ、強度は出るものの延性、加工性は大幅
に劣化し、他方、４５０℃を超えるとパーライト相が混
入し、やはり鋼の延性を害する。また１分未満の保持で
は適正なベイナイト変態が生じない。保持効果は１０分
程度で飽和するので保持時間の上限は１０分とした。In order to transform the thus obtained γ phase in the properly γ / α-separated structure at around 400 ° C., 30 ° C./s
Rapid cooling at ec or more. If the quenching rate is less than 30 ° C./sec, the γ phase is transformed into an undesired structure such as pearlite. The holding condition after quenching must be 1 to 10 minutes in a temperature range of 350 to 450 ° C. In the case of the steel of the present invention, the first
It is considered that the austenite phase, which partially remained when the γ phase whose components were adjusted during the slow cooling of the step, was transformed into the bainite phase during this holding, became extremely stable, and remained as austenite even in the product state. Therefore, it is important in the present invention to appropriately transform the γ phase into bainite. If the holding temperature is lower than 350 ° C., an excessive martensite phase is formed, and although the strength is obtained, ductility and workability are significantly deteriorated. If the holding time is less than 1 minute, appropriate bainite transformation does not occur. Since the holding effect is saturated in about 10 minutes, the upper limit of the holding time is set to 10 minutes.
【００１９】この熱処理は雰囲気制御された連続焼鈍で
行うのが適切であるが、他の熱処理設備でも本発明の条
件を満たす限り有効である。また、その場合０．５〜２
％の調質圧延が施されるが、これは本発明にとってなん
ら差障りのあるものではない。熱処理に先立つ熱延は特
に条件を限定するところではない。通常、スラブ加熱温
度１０５０〜１３００℃、仕上終了温度８００〜９５０
℃、巻取温度４００〜７００℃程度の条件が採られる。
また、場合によっては冷延されるが冷延率も通常の５０
〜８５％程度でよい。This heat treatment is suitably carried out by continuous annealing in a controlled atmosphere, but other heat treatment equipment is also effective as long as the conditions of the present invention are satisfied. In that case, 0.5 to 2
% Temper rolling is performed, but this does not hinder the present invention at all. The conditions of hot rolling prior to heat treatment are not particularly limited. Usually, the slab heating temperature is 1050 to 1300 ° C, and the finishing temperature is 800 to 950.
And a winding temperature of about 400 to 700 ° C.
In some cases, cold rolling is performed.
It may be about 85%.
【００２０】[0020]
【実施例】表１に示す化学成分の鋼を溶製した。鋼符号
Ａ〜Ｆが本発明に従ったもので、鋼Ｇは炭素量が低く従
来のいわゆるデュアルフェイズ鋼の成分である。鋼Ｈは
炭素量が高く、かつＡｌ量が低い。鋼ＩはＡｌ量が、鋼
ＪではＳｉ量、鋼ＫではＭｎ量がそれぞれ低い。鋼Ｉ
は、従って、どちらかと言うと従来残留オーステナイト
型ハイテン（従来γと記す）に近い。EXAMPLES Steel having the chemical components shown in Table 1 was melted. Steel symbols A to F are according to the present invention, and steel G has a low carbon content and is a component of a conventional so-called dual phase steel. Steel H has a high carbon content and a low Al content. Steel I has a low Al content, steel J has a low Si content, and steel K has a low Mn content. Steel I
Therefore, it is rather close to conventional retained austenite type high tensile steel (conventionally referred to as γ).
【００２１】これらの鋼を熱延し、あるいはさらに冷延
し、表２に示す熱処理条件で熱処理を行った。この熱処
理は連続焼鈍ラインにて行った。熱処理後、鋼帯は０．
８％の調質圧延が付加されている。引張試験はＪＩＳＺ
２２０１記載の５号試験片を用い、同Ｚ２２４１記載の
方法に従って行った。These steels were hot-rolled or cold-rolled, and heat-treated under the heat treatment conditions shown in Table 2. This heat treatment was performed in a continuous annealing line. After heat treatment, the steel strip has a.
8% temper rolling has been added. Tensile test is JISZ
The test was performed using the No. 5 test piece described in 2201 according to the method described in Z2241.
【００２２】ｎ値は、応力−ひずみ関係をｎ乗硬化則が
成り立つとし、１０％および２０％ひずみ時の荷重、Ｐ
１、Ｐ２より次式により求めた。Assuming that the stress-strain relationship satisfies the n-th power hardening rule, the n value is the load at 10% and 20% strain, P
1 and P2 were determined by the following equation.
【００２３】[0023]
【数１】 (Equation 1)
【００２４】ただし、本発明に従った鋼は特異な強化機
構を示し、応力−ひずみ関係も極めて特異なのでｎ乗硬
化則はあまり適合しない。しかし、上の定義に従ったｎ
値が、大きな加工性指標であることにはまちがいない。
また、局部変形能としては穴拡げ性（ｄ／ｄ0 ）を用い
た。これは打ち抜きクリアランス１０％で打ち抜いた直
径２０ｍｍの穴を３０°円錐ポンチで広げていき、割れ
が板厚を貫通した時点での穴径ｄを測定しこれを初期穴
径ｄ0 （＝２０ｍｍ）で除した値で表す。However, the steel according to the present invention exhibits a unique strengthening mechanism and the stress-strain relationship is extremely unique, so that the n-th power hardening law does not fit well. However, n according to the above definition
There is no doubt that the value is a large workability index.
The hole expandability (d / d 0 ) was used as the local deformability. In this method, a hole having a diameter of 20 mm punched with a punching clearance of 10% is spread with a 30 ° conical punch, and the hole diameter d at the time when the crack penetrates the plate thickness is measured. This is determined as the initial hole diameter d 0 (= 20 mm). It is expressed by the value divided by.
【００２５】また、製品の残留オーステナイト量はＸ線
を用いて測定した。表３に材質試験結果および残留オー
ステナイト量測定結果を併せて示す。本発明に従った鋼
は６００Ｎ／ｍｍ2 級以上の高い強度の割に４０％近い
極めて高い伸びを示し（これは引張強度３００〜４００
Ｎ／ｍｍ2 級の軟鋼板に匹敵する）、ｎ値も極めて高い
（図１に引張強度と伸びの関係を示す）。また、残留γ
量も引張強度に応じて適宜確保されている。さらに、従
来のγ残留ハイテン（Ｎｏ．２０の鋼）やデュアルフェ
イズ鋼（Ｎｏ．１８の鋼）は伸びフランジ性に劣るとさ
れていたが、表３あるいは図２に示すように本発明に従
った鋼は伸びフランジ性においても概ね１．５以上とい
う高い値を示す。The amount of retained austenite in the product was measured using X-rays. Table 3 also shows the results of the material test and the measurement of the amount of retained austenite. The steel according to the present invention exhibits a very high elongation of nearly 40% for a high strength of 600 N / mm 2 or more (this is a tensile strength of 300 to 400).
N / mm 2 grade mild steel plate), and the n value is extremely high (FIG. 1 shows the relationship between tensile strength and elongation). Also, the residual γ
The amount is appropriately secured according to the tensile strength. Further, conventional γ-retained high tensile steel (No. 20 steel) and dual-phase steel (No. 18 steel) are said to have poor stretch flangeability, but according to the present invention as shown in Table 3 or FIG. The steel also shows a high value of about 1.5 or more in stretch flangeability.
【００２６】また、確認のため表２に示す鋼のスポット
溶接試験を行ったところ、Ｎｏ．１９の鋼を除き、溶接
継手強度、および溶接継手の剥離状況とも良好であっ
た。For the confirmation, spot welding tests of steel shown in Table 2 were performed. Except for steel No. 19, the strength of the welded joint and the peeling state of the welded joint were also good.
【００２７】[0027]
【表１】 [Table 1]
【００２８】[0028]
【表２】 [Table 2]
【００２９】[0029]
【表３】 [Table 3]
【００３０】[0030]
【発明の効果】本発明によれば、加工成形性と強度いう
相反する特性の両立を本格的に達成できることで、得ら
れた鋼板は自動車に全面的に適用が可能となり、延いて
は自動車の軽量化をもたらし、それを通じて地球規模環
境保護に寄与する。また、本発明による鋼板の使用によ
り、軽量、高意匠の自動車設計が可能となり、ユーザー
の好みに応え得るので、自動車産業の発展にさらに寄与
する。According to the present invention, the steel sheet obtained can be fully applied to automobiles by realizing the compatibility between workability and strength, which are opposite properties, in earnest. It contributes to weight reduction, thereby contributing to global environmental protection. In addition, the use of the steel sheet according to the present invention makes it possible to design a lightweight and highly-designed automobile, and can meet user's preference, thereby further contributing to the development of the automobile industry.
【図１】実施例の鋼の引張強度と伸びの関係を示す図で
ある。FIG. 1 is a diagram showing a relationship between tensile strength and elongation of steel of an example.
【図２】実施例の鋼の引張強度と穴拡げ率との関係を示
す図である。FIG. 2 is a diagram showing the relationship between the tensile strength and the hole expansion ratio of the steel of the example.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−4832（ＪＰ，Ａ) 特開 昭60−43464（ＪＰ，Ａ) 特開 昭61−170518（ＪＰ，Ａ) 特開 昭56−29631（ＪＰ，Ａ) 特開 平１−119618（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C21D 8/04,9/46,9/52 C22C 38/00,38/06──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-24832 (JP, A) JP-A-60-43464 (JP, A) JP-A-61-170518 (JP, A) JP-A Sho 56-434 29631 (JP, A) JP-A-1-119618 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C21D 8/04, 9/46, 9/52 C22C 38/00, 38/06
Claims (3)
様）で、Ｃ：０．０８〜０．３０％、Ｍｎ：１．０〜
２．０％、Ｓｉ：０．５〜２．５％、Ａｌ：０．５〜
１．５％を含有し、残部Ｆｅおよび不可避的不純物から
なる鋼を熱延した後、７３０〜９００℃に１０〜３００
秒加熱し、続いて６６０〜７２０℃まで１０℃／ｓｅｃ
以下で冷却し、その後３０℃／ｓｅｃ以上で３５０〜４
５０℃まで急冷し、その温度で１〜１０分保持すること
を特徴とする加工性の極めて優れた高強度薄鋼板の製造
方法。C .: 0.08 to 0.30%, Mn: 1.0 to 100% by mass (the same applies to steel components hereinafter).
2.0%, Si: 0.5 to 2.5%, Al: 0.5 to
After hot-rolling a steel containing 1.5% and the balance consisting of Fe and unavoidable impurities, the steel was heated to 730 to 900 ° C at 10 to 300 ° C.
Heated for 10 seconds, then 10 ° C / sec to 660-720 ° C
Cool at a temperature below 30 ° C / sec.
A method for producing a high-strength thin steel sheet having extremely excellent workability, wherein the steel sheet is rapidly cooled to 50 ° C. and kept at the temperature for 1 to 10 minutes.
０〜２．０％、Ｓｉ：０．５〜２．５％、Ａｌ：０．５
〜１．５％を含有し、さらにＣａ、Ｍｇ、ＲＥＭ、Ｚｒ
の１種以上を合計で０．００１〜０．０５％含み、残部
Ｆｅおよび不可避的不純物からなる鋼を熱延した後、７
３０〜９００℃に１０〜３００秒加熱し、続いて６６０
〜７２０℃まで１０℃／ｓｅｃ以下で冷却し、その後３
０℃／ｓｅｃ以上で３５０〜４５０℃まで急冷し、その
温度で１〜１０分保持することを特徴とする加工性の極
めて優れた高強度薄鋼板の製造方法。2. C: 0.08 to 0.30%, Mn: 1.
0 to 2.0%, Si: 0.5 to 2.5%, Al: 0.5
~ 1.5%, and further Ca, Mg, REM, Zr
After hot-rolling a steel containing at least one of the following, 0.001 to 0.05% in total and the balance being Fe and unavoidable impurities,
Heat to 30-900 ° C. for 10-300 seconds, followed by 660
To 720 ° C. at 10 ° C./sec or less.
A method for producing a high-strength thin steel sheet having extremely excellent workability, wherein the steel sheet is rapidly cooled to 350 to 450 ° C. at 0 ° C./sec or more and held at that temperature for 1 to 10 minutes.
後、７３０〜９００℃に１０〜３００秒加熱し、続いて
６６０〜７２０℃まで１０℃／ｓｅｃ以下で冷却し、そ
の後３０℃／ｓｅｃ以上で３５０〜４５０℃まで急冷
し、その温度で１〜１０分保持することを特徴とする請
求項１または２記載の加工性の極めて優れた高強度薄鋼
板の製造方法。3. The starting steel is hot-rolled and further cold-rolled, heated to 730 to 900 ° C. for 10 to 300 seconds, subsequently cooled to 660 to 720 ° C. at a rate of 10 ° C./sec or less, and then cooled to 30 ° C. 3. The method for producing a high-strength thin steel sheet having extremely excellent workability according to claim 1 or 2, wherein the steel sheet is rapidly cooled to 350 to 450 [deg.] C. at a rate of not less than / sec and maintained at that temperature for 1 to 10 minutes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28150991A JP2860438B2 (en) | 1991-10-28 | 1991-10-28 | Manufacturing method of high-strength thin steel sheet with extremely excellent workability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28150991A JP2860438B2 (en) | 1991-10-28 | 1991-10-28 | Manufacturing method of high-strength thin steel sheet with extremely excellent workability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05117761A JPH05117761A (en) | 1993-05-14 |
| JP2860438B2 true JP2860438B2 (en) | 1999-02-24 |
Family
ID=17640177
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28150991A Expired - Lifetime JP2860438B2 (en) | 1991-10-28 | 1991-10-28 | Manufacturing method of high-strength thin steel sheet with extremely excellent workability |
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| Country | Link |
|---|---|
| JP (1) | JP2860438B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3764411B2 (en) | 2002-08-20 | 2006-04-05 | 株式会社神戸製鋼所 | Composite steel sheet with excellent bake hardenability |
| JP4494903B2 (en) * | 2004-08-12 | 2010-06-30 | 新日本製鐵株式会社 | Continuous annealing equipment for manufacturing high-strength steel sheets |
| EP2671960B1 (en) | 2005-03-31 | 2017-11-01 | Kabushiki Kaisha Kobe Seiko Sho | High strength cold-rolled steel sheet and automobile components of steel having excellent properties in coating film adhesion, workability, and hydrogen embrittlement resistivity |
| CN104087824B (en) * | 2014-07-11 | 2016-04-27 | 北京科技大学 | A kind of preparation method with the hyperfine structure bainitic steel of TRIP effect |
| WO2020058748A1 (en) * | 2018-09-20 | 2020-03-26 | Arcelormittal | Cold rolled and coated steel sheet and a method of manufacturing thereof |
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1991
- 1991-10-28 JP JP28150991A patent/JP2860438B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05117761A (en) | 1993-05-14 |
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