JP3519869B2 - High-strength hot-rolled steel sheet for automobiles having excellent deformation resistance at high strain rate and method for producing the same - Google Patents
High-strength hot-rolled steel sheet for automobiles having excellent deformation resistance at high strain rate and method for producing the sameInfo
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- JP3519869B2 JP3519869B2 JP13145196A JP13145196A JP3519869B2 JP 3519869 B2 JP3519869 B2 JP 3519869B2 JP 13145196 A JP13145196 A JP 13145196A JP 13145196 A JP13145196 A JP 13145196A JP 3519869 B2 JP3519869 B2 JP 3519869B2
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- hot
- rolled steel
- automobiles
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Description
【０００１】[0001]
【発明の属する技術分野】本発明は、主として、自動車
の耐衝突部材に用いる高歪速度時の変形抵抗に優れた自
動車用高張力熱延鋼板およびその製造方法に関わる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a high-strength hot-rolled steel sheet for automobiles, which is used for a collision-resistant member of automobiles and has an excellent deformation resistance at a high strain rate, and a manufacturing method thereof.
【０００２】[0002]
【従来の技術】自動車の衝突安全性能を評価する上で重
要なことは高歪速度時の変形抵抗の高さである。すなわ
ち、歪速度１０-3／ｓ程度で評価する静的強度よりも、
高歪速度（１０2 ／ｓ〜１０3 ／ｓ）で評価する動的強
度が重要であり、次のような提案がなされている。例え
ば、特開平７−１８３７２号公報記載の技術では動的強
度（歪速度１０2 ／ｓ）と静的強度（歪速度１０-3／
ｓ）の比で、静動比を定義し、それを高めるには鋼中の
残留オーステナイトの量が１０％以上必要で、かつフェ
ライト相の固溶Ｃ量を０．００２０％以下とすることを
必要としている。すなわち、この技術では変形量の大き
い場合の静動比は残留オーステナイトの誘起変態を利用
し、変形量の小さい変形でははフェライト相を軟質化す
ることで静動比を高めている。しかし、この技術は自動
車用部品として使用するには、事前に加工を受けるので
残留オーステナイトが加工誘起変態し、肝心な衝突時に
期待する残留オーステナイト量を安定して確保するのが
困難である。2. Description of the Related Art What is important in evaluating the crash safety performance of an automobile is the high deformation resistance at high strain rates. That is, rather than the static strength evaluated at a strain rate of about 10 −3 / s,
The dynamic strength evaluated at a high strain rate (10 2 / s to 10 3 / s) is important, and the following proposals have been made. For example, in the technique described in JP-A-7-18372, the dynamic strength (strain rate 10 2 / s) and the static strength (strain rate 10 -3 / s)
The ratio of s) defines a static-dynamic ratio, and in order to increase it, the amount of retained austenite in steel must be 10% or more, and the amount of dissolved C in the ferrite phase should be 0.0020% or less. In need of. That is, in this technique, the static-dynamic ratio when the deformation amount is large utilizes the induced transformation of retained austenite, and when the deformation amount is small, the ferrite phase is softened to increase the static-dynamic ratio. However, with this technique, when used as an automobile part, the retained austenite undergoes work-induced transformation because it is subjected to work in advance, and it is difficult to stably secure the expected amount of retained austenite during a critical collision.
【０００３】[0003]
【発明が解決しようとする課題】本発明は、上記のよう
な問題点を解消し、高歪速度時の変形抵抗に優れた自動
車用高張力熱延鋼板およびその製造方法を提供すること
にある。SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-strength hot-rolled steel sheet for automobiles, which is excellent in deformation resistance at a high strain rate, and a manufacturing method thereof, which solves the above problems. .
【０００４】[0004]
【課題を解決するための手段】本発明者らは上記の課題
を解決するため以下のような検討を行った。はじめに高
歪速度時の変形抵抗に優れた熱延鋼板の強化機構につい
て検討を行った。表１に示す化学成分、熱延条件で製造
したスラブを熱間圧延し、得られた鋼板の静動比を測定
した。静動比は歪速度１０3 ／ｓの動的強度と歪速度１
０-3／ｓの比で定義した。なお、動的強度と静的強度は
３〜１０％応力の平均値とした。表２に供試鋼の光学顕
微鏡組織、静的強度および静動比を示す。鋼Ａと鋼Ｂで
は静的強度がほとんどかわらないが、静動比は、固溶強
化されたフェライト相を有する鋼Ａの方が大きい。Means for Solving the Problems The present inventors have conducted the following studies in order to solve the above problems. First, we investigated the strengthening mechanism of hot-rolled steel sheet that has excellent deformation resistance at high strain rates. The slabs produced under the chemical composition and hot rolling conditions shown in Table 1 were hot-rolled, and the static-dynamic ratio of the obtained steel sheet was measured. The static-dynamic ratio is a dynamic strength with a strain rate of 10 3 / s and a strain rate of 1
It was defined as a ratio of 0 -3 / s. The dynamic strength and static strength were average values of 3 to 10% stress. Table 2 shows the optical microscope structure, static strength and static-dynamic ratio of the sample steels. The static strengths of Steel A and Steel B are almost the same, but the static-dynamic ratio is higher in Steel A having the solid solution strengthened ferrite phase.
【０００５】[0005]
【表１】 [Table 1]
【０００６】[0006]
【表２】 [Table 2]
【０００７】次にフェライト相の固溶強化度の静動比に
及ぼす影響を調査するため、表３に示すように、Ｓｉ量
を変化させた熱延鋼板を作製した。表４にフェライト相
のビッカース硬さと静動比を示す。ビッカース硬さはＪ
ＩＳ Ｚ ２２４４に記載された方法に従い、測定し
た。試験荷重は９．８Ｎとした。鋼Ｃと鋼Ｄでは静的強
度がほとんど変わらないが、静動比は、Ｓｉ量が高く、
フェライト相のビッカース硬さが大きい鋼Ｃの方が大き
い。Next, in order to investigate the effect of the degree of solid solution strengthening of the ferrite phase on the static-dynamic ratio, as shown in Table 3, hot-rolled steel sheets with varying Si contents were produced. Table 4 shows the Vickers hardness and static-dynamic ratio of the ferrite phase. Vickers hardness is J
It was measured according to the method described in IS Z 2244. The test load was 9.8N. Steel C and Steel D have almost the same static strength, but the static-dynamic ratio is high in Si content,
Steel C, which has a large Vickers hardness of the ferrite phase, is larger.
【０００８】[0008]
【表３】 [Table 3]
【０００９】[0009]
【表４】 [Table 4]
【００１０】すなわち、得られた知見をまとめると以下
のようになる。
（１）静動比を高めるためには、析出強化したフェライ
ト相よりも固溶強化したフェライト相を利用するのが有
効である。
（２）フェライト相の固溶強化の程度、言い換えるとフ
ェライト相のビッカース硬さを上げることは静動比を高
めることに有効である。
（３）固溶強化されたフェライト相だけでは目標強度が
不足する場合に、少量のマルテンサイト相を併用しても
静動比には大きな影響は与えない。高歪速度で高い変形
抵抗を得るためにフェライト相の固溶強化が適している
理由としては、転位の移動度を抑制し、かつ変形中の可
動転位密度の増加率を低減するのに適しているためと推
定される。本発明は以上のような知見に基づくものであ
り、その主旨は以下の通りである。That is, the obtained knowledge is summarized as follows. (1) In order to increase the static-dynamic ratio, it is effective to use the solid solution strengthened ferrite phase rather than the precipitation strengthened ferrite phase. (2) Increasing the degree of solid solution strengthening of the ferrite phase, in other words, increasing the Vickers hardness of the ferrite phase is effective in increasing the static-dynamic ratio. (3) When the target strength is insufficient only with the solid solution-strengthened ferrite phase, the static-dynamic ratio is not significantly affected even if a small amount of the martensite phase is used together. The reason why solid solution strengthening of the ferrite phase is suitable for obtaining high deformation resistance at a high strain rate is that it is suitable for suppressing the mobility of dislocations and reducing the increase rate of the mobile dislocation density during deformation. It is presumed that this is because The present invention is based on the above findings, and its gist is as follows.
【００１１】（１）質量％で、Ｃ：０．０４〜０．１５
％、Ｓｉ：０．５〜１．８％、Ｍｎ：０．８〜２．０
％、Ｐ：０．０２５％以下、Ｓ：０．０１％以下、Ａ
ｌ：０．００５〜０．１％を含有し残部Ｆｅおよび不可
避的不純物元素からなる鋼を溶製し、連続鋳造してスラ
ブとした後、加熱炉に挿入することなく熱間圧延する
か、または加熱炉にてスラブを１２５０℃以下に加熱し
た後に熱間圧延を行い、Ａｒ 3 点±４０℃で圧延を終了
し、平均冷却速度１０〜８０℃／ｓで冷却し、３５０℃
以下で巻き取り、熱延鋼帯とし、その鋼板の組織がマル
テンサイトからなる第２相を含み、フェライト相が８０
％以上でかつフェライト相のビッカース硬さが１００以
上であることを特徴とする高歪速度時の変形抵抗に優れ
た自動車用高張力熱延鋼板の製造方法。 (1) C: 0.04 to 0.15 in mass%
%, Si: 0.5 to 1.8%, Mn: 0.8 to 2.0
%, P: 0.025% or less, S: 0.01% or less, A
1: Steel containing 0.005 to 0.1% and the balance Fe and unavoidable impurity elements is melted, continuously cast, and slurried.
And then hot rolling without inserting into the heating furnace
Or heat the slab to below 1250 ° C in a heating furnace
After that, hot rolling is performed, and the rolling is completed at Ar 3 points ± 40 ° C.
And cool at an average cooling rate of 10-80 ° C / s, 350 ° C
It is wound up below and made into a hot rolled steel strip, and the structure of the steel sheet is
Includes a second phase consisting of tensite and a ferrite phase of 80
% And the Vickers hardness of the ferrite phase is 100 or less.
Excellent resistance to deformation at high strain rates characterized by being above
For manufacturing high-strength hot-rolled steel sheet for automobiles.
【００１２】（２）質量％で、Ｃ：０．０４〜０．１５
％、Ｓｉ：０．５〜１．８％、Ｍｎ：０．８〜２．０
％、Ｐ：０．０２５％以下、Ｓ：０．０１％以下、Ａ
ｌ：０．００５〜０．１％に加えて、Ｃｒ：０．０５〜
０．５％、Ｃａ：０．０００５〜０．０１％、Ｎｂ：
０．００１〜０．０５％、Ｖ：０．００５〜０．１％、
Ｔｉ：０．００５〜０．０５％、Ｎｉ：０．０５〜０．
５％、Ｍｏ：０．０５〜１．０％のうち一種または二種
以上を含有し残部Ｆｅおよび不可避的不純物元素からな
る鋼を溶製し、連続鋳造してスラブとした後、加熱炉に
挿入することなく熱間圧延するか、または加熱炉にてス
ラブを１２５０℃以下に加熱した後に熱間圧延を行い、
Ａｒ 3 点±４０℃で圧延を終了し、平均冷却速度１０〜
８０℃／ｓで冷却し、３５０℃以下で巻き取り、熱延鋼
帯とし、その鋼板の組織がマルテンサイ トからなる第２
相を含み、フェライト相が８０％以上でかつフェライト
相のビッカース硬さが１００以上であることを特徴とす
る高歪速度時の変形抵抗に優れた自動車用高張力熱延鋼
板の製造方法である。 (2) C: 0.04 to 0.15 in mass%
%, Si: 0.5 to 1.8%, Mn: 0.8 to 2.0
%, P: 0.025% or less, S: 0.01% or less, A
l: 0.005-0.1%, Cr: 0.05-
0.5%, Ca: 0.0005 to 0.01%, Nb:
0.001-0.05%, V: 0.005-0.1%,
Ti: 0.005-0.05%, Ni: 0.05-0.
5% Mo: 0.05-1.0% of 0.05 to 1.0% of steel containing the balance Fe and unavoidable impurity elements is melted, continuously cast into a slab, and then placed in a heating furnace.
Hot-roll without inserting or in a heating furnace
After heating the rub to 1250 ° C or lower, hot rolling is performed,
The rolling is completed at Ar 3 points ± 40 ° C, and the average cooling rate is 10
Cooled at 80 ℃ / s, rolled up at 350 ℃ or below, hot rolled steel
As a band, the second the organization of the steel plate is made of martensite
Phase, 80% or more of ferrite phase and ferrite
The Vickers hardness of the phase is 100 or more.
High-strength hot-rolled steel for automobiles with excellent deformation resistance at high strain rates
It is a method of manufacturing a plate.
【００１３】
本発明における成分および熱延条件の限定
によりもたらされる作用を以下に述べる。Ｃは複合組織
中のマルテンサイトの体積率を増加させ、強度を高める
作用があり、このため少なくとも０．０４％を必要と
し、一方、０．１５％を越えると加工性および溶接性の
劣化が大きい。Ｓｉは本発明では重要な元素である。す
なわち、その量が多いほどフェライト変態を促進させ、
未変態オーステナイト中のＣ濃度を上げ、複合組織を形
成しやすくする元素である。かつ、フェライト相を固溶
強化し、必要な硬度を得るものである。そのためには
０．５％以上必要である。一方、Ｓｉの増加はスケール
オフ量を増加させ、歩留まりの低下を招くとともにコス
ト増となるので上限を１．８％とした。 The effects brought about by the limitation of the components and hot rolling conditions in the present invention will be described below. C has the effect of increasing the volume fraction of martensite in the composite structure and increasing the strength, and therefore requires at least 0.04%, while if it exceeds 0.15%, the workability and weldability deteriorate. large. Si is an important element in the present invention. That is, the larger the amount, the more the ferrite transformation is promoted,
It is an element that increases the C concentration in untransformed austenite and facilitates the formation of a composite structure. In addition, the ferrite phase is solid-solution strengthened to obtain the required hardness. For that purpose, 0.5% or more is necessary. On the other hand, an increase in Si causes an increase in the amount of scale-off, which leads to a decrease in yield and an increase in cost, so the upper limit was made 1.8%.
【００１４】
Ｍｎは０．８％未満ではマルテンサイトが
得られない。しかし、Ｍｎが多すぎるとフェライト変態
を抑制し、ベイナイト変態を助長するとともにコスト高
となるので上限を２．０％とした。Ｐ，Ｓは加工性・溶
接性を劣化させるとともに偏析を助長する。従って、こ
れらの量は低い方が良く、Ｐは０．０２５％以下、Ｓは
０．０１％以下とした。Ａｌは脱酸剤として有効である
が、０．００５％以上でその効果が発揮される。しか
し、０．１％を越えて使用することは介在物の増加をも
たらし好ましくないため０１％以下とした。 If Mn is less than 0.8%, martensite cannot be obtained. However, if Mn is too much, ferrite transformation is suppressed, bainite transformation is promoted, and cost is increased, so the upper limit was made 2.0%. P and S deteriorate workability and weldability and promote segregation. Therefore, it is preferable that these amounts are low, and P is 0.025% or less and S is 0.01% or less. Al is effective as a deoxidizing agent, but its effect is exhibited at 0.005% or more. However, the use of more than 0.1% causes an increase in inclusions and is not preferable, so the content was made 0.1% or less.
【００１５】
本発明では以上の成分の他にＣｒ，Ｃａ，
Ｎｂ，Ｖ，Ｔｉ，ＮｉおよびＭｏのうち、１種または２
種以上を適宜添加させることで発明の効果をさらに発揮
させることができる。Ｃａは介在物の形状を調整し、冷
間加工性を改善する作用があるが、０．０００５％未満
ではその効果を得ることができず、一方、０．０１％を
越えると介在物の量を増やし、かえって冷間加工性を損
なうことから０．０００５〜０．０１％とした。Ｃｒは
オーステナイトの安定化に寄与し、複合組織化に有効で
あり、０．０５％以上でその効果が発揮されるため下限
を０．０５％とした。但し、０．５％を越えると効果が
飽和するばかりでなく、コスト増となる。Ｎｂ，Ｖ，Ｔ
ｉ，ＮｉおよびＭｏは溶接部の強度を上げる働きをす
る。各々、下限値未満では効果がなく、上限値を超える
と効果が飽和し、コスト増となる。 In the present invention, in addition to the above components, Cr, Ca,
One or two of Nb, V, Ti, Ni and Mo
The effects of the invention can be further exerted by appropriately adding one or more species. Ca has the effect of adjusting the shape of inclusions and improving cold workability, but if it is less than 0.0005%, the effect cannot be obtained, while if it exceeds 0.01%, the amount of inclusions is increased. Was added, and rather the cold workability was impaired, so the content was made 0.0005 to 0.01%. Cr contributes to the stabilization of austenite and is effective for forming a composite structure, and the effect is exhibited at 0.05% or more, so the lower limit was made 0.05%. However, if it exceeds 0.5%, not only the effect is saturated, but also the cost increases. Nb, V, T
i, Ni and Mo serve to increase the strength of the welded portion. If it is less than the lower limit value, there is no effect, and if it exceeds the upper limit value, the effect is saturated and the cost increases.
【００１６】
次に熱延条件について述べる。スラブは加
熱炉に挿入せずに直接熱間圧延してもよい。加熱炉に挿
入して再加熱する場合は加熱温度を１２５０℃以下とす
る。これはＳｉスケールの発生を低減させるためであ
る。このＳｉスケールは鋼板の粗度を大きくして成形特
性を劣化させたり、歩留まりロスの増加につながる。ま
た、加熱温度の上昇は燃料原単位の増加を招く。加熱温
度の下限は作業の容易性から１０００℃以上が好まし
い。 [0016] will now be described hot-rolled condition. The slab may be directly hot-rolled without inserting it into the heating furnace. When it is inserted into a heating furnace and reheated, the heating temperature is set to 1250 ° C or lower. This is to reduce the generation of Si scale. This Si scale increases the roughness of the steel sheet to deteriorate the forming characteristics and increases the yield loss. Further, the increase in heating temperature causes an increase in fuel consumption rate. The lower limit of the heating temperature is preferably 1000 ° C. or higher in terms of workability.
【００１７】
圧延終了温度はＡｒ3 ±４０℃とする。Ａ
ｒ3 ＋４０℃を越えると変態後のフェライト粒が粗大化
し、十分な衝突吸収エネルギー能がなくなる。一方、圧
延終了温度がＡｒ3 −４０℃未満では加工フェライトが
残るために加工性が劣化する。圧延後の平均冷却速度は
１０〜８０℃／ｓとする。１０℃／ｓ未満ではフェライ
ト粒が粗大化し、８０℃／ｓを越えるとフェライトの生
成量が不足してオーステナイト中のＣ，Ｍｎ濃縮が十分
でなくなるために粗大な第２相の組織が生成し、加工性
が劣化する。巻取温度は未変態のオーステナイトをマル
テンサイトに変態させるために３５０℃以下とする。こ
れを越えると粗大なベイナイトないしパーライトが生成
し、加工性が劣化する。下限は材質上は特に規制の必要
はないが、コイルが長時間水漏れ状態にあると錆による
外観不良が懸念されるために５０℃以上が好ましい。 The rolling end temperature is Ar 3 ± 40 ° C. A
If r 3 + 40 ° C. is exceeded, the ferrite grains after transformation become coarse and sufficient collision absorption energy capacity is lost. On the other hand, when the rolling end temperature is less than Ar 3 -40 ° C., workability deteriorates because work ferrite remains. The average cooling rate after rolling is 10 to 80 ° C./s. If it is less than 10 ° C / s, the ferrite grains become coarse, and if it exceeds 80 ° C / s, the amount of ferrite produced is insufficient and the concentration of C and Mn in austenite is insufficient, so that a coarse second-phase structure is produced. , Workability deteriorates. The coiling temperature is set to 350 ° C. or lower in order to transform untransformed austenite into martensite. If it exceeds this, coarse bainite or pearlite is generated, and the workability deteriorates. The lower limit is not particularly limited in terms of material, but if the coil is in a water leak state for a long period of time, there is a fear of appearance failure due to rust, so 50 ° C. or higher is preferable.
【００１８】
次に熱延鋼板の組織因子について詳述す
る。フェライト相は８０％以上でかつビッカース硬さが
１００以上とする。フェライト相が８０％未満では加工
性が低下する。また、ビッカース硬さが１００未満では
静動比が低下する。本発明は熱延鋼板のみならず、これ
らを素材とした電気めっき鋼板または有機複合めっき鋼
板に対しても、高歪速度時の変形抵抗に優れた特性を得
ることができる。ここで、電気めっき鋼板とは、Ｎｉを
５〜２０％含有するＺｎ−Ｎｉ系合金めっき鋼板のこと
であり、有機複合めっきとは、Ｎｉを５〜２０％含有す
るＺｎ−Ｎｉ系合金めっき鋼板の表面に第１層として塗
布型クロメート皮膜を固形皮膜として５〜１５０ｍｇ／
ｍ2 形成させ、その上層に第２層として有機溶剤系塗料
組成物を固形皮膜として０．３〜５μｍ塗装したもので
ある。 [0018] Next will be described in detail tissue factor of the hot-rolled steel sheet. The ferrite phase is 80% or more and the Vickers hardness is 100 or more. If the ferrite phase is less than 80%, the workability will be reduced. Further, if the Vickers hardness is less than 100, the static-dynamic ratio is lowered. INDUSTRIAL APPLICABILITY The present invention can provide not only hot-rolled steel sheets, but also electroplated steel sheets or organic composite-plated steel sheets made of these materials with excellent characteristics in deformation resistance at high strain rates. Here, the electroplated steel sheet is a Zn-Ni alloy plated steel sheet containing 5 to 20% Ni, and the organic composite plating is a Zn-Ni alloy plated steel sheet containing 5 to 20% Ni. The coating type chromate film as the first layer on the surface of the
m 2 is formed, and an organic solvent-based coating composition is applied as a second layer on the upper layer thereof in a solid film thickness of 0.3 to 5 μm.
【００１９】[0019]
【実施例】表５に供試鋼の化学成分を示す。鋼Ａ，Ｂ，
Ｃ，Ｄ，Ｅは本発明に従った鋼であり、鋼ＦはＣが上限
はずれ、鋼ＧはＳｉが下限はずれである。表６に熱延条
件を示す。符号１〜７は本発明の熱延条件に従ってい
る。符号８は熱延時の冷却速度が上限はずれ、符号９は
熱延時の巻取温度が上限はずれである。表７に供試鋼の
光学顕微鏡組織の分率、フェライト相のビッカース硬
さ、静動比およびプレス成形性を示す。光学顕微鏡組織
の分率は点算法で求めた。静動比は歪速度１０3 ／ｓの
動的強度と歪速度１０-3／ｓの比で定義した。なお、動
的強度と静的強度は３〜１０％応力の平均値とした。な
お、静動比は１．４以上で高歪速度時の変形抵抗に優れ
た特性が得られる。ビッカース硬さはＪＩＳ Ｚ ２２
４４に記載された方法に従い、測定した。試験荷重は
９．８Ｎとした。また、プレス成形性は、長さ１０００
ｍｍのサイドメンバーの試作金型を用いて、プレスを行
い、割れを生じなかったものを〇、割れを生じたものを
×とした。[Examples] Table 5 shows the chemical composition of the test steel. Steel A, B,
C, D, and E are steels according to the present invention. Steel F has an upper limit of C and steel G has a lower limit of Si. Table 6 shows the hot rolling conditions. Reference numerals 1 to 7 comply with the hot rolling conditions of the present invention. Reference numeral 8 indicates that the cooling rate during hot rolling is out of the upper limit, and reference numeral 9 indicates that the winding temperature during hot rolling is out of the upper limit. Table 7 shows the fraction of the optical microscope structure of the sample steel, the Vickers hardness of the ferrite phase, the static-dynamic ratio, and the press formability. The fraction of the optical microscope structure was determined by the point calculation method. Shizudohi was defined in the dynamic strength and the ratio of the strain rate 10 -3 / s of strain rate 10 3 / s. The dynamic strength and static strength were average values of 3 to 10% stress. The static-dynamic ratio is 1.4 or more, and excellent characteristics of deformation resistance at high strain rate can be obtained. Vickers hardness is JIS Z 22
The measurement was performed according to the method described in 44. The test load was 9.8N. In addition, press formability is 1000
Pressing was carried out using a trial mold of a side member having a size of mm, and those without cracks were marked with ◯, and those with cracks were marked with x.
【００２０】[0020]
【表５】 [Table 5]
【００２１】[0021]
【表６】 [Table 6]
【００２２】[0022]
【表７】 [Table 7]
【００２３】符号１〜５は本発明に従った鋼で、動静比
も高く、プレス成形性も良好である。符号６はＣが上限
値を超えたため、第２相が硬質化し、プレス成形性が劣
化した。符号７はＳｉが下限値を外れたため、フェライ
ト相の固溶強化が足りず、静動比が劣化した。符号８は
熱延時の冷却速度が上限値を外れたため、フェライトが
生成せず、オーステナイトへのＣ，Ｍｎの濃縮が不十分
で、粗大な第２相が生成し、静動比およびプレス成形性
が劣化した。符号９は巻取温度が上限はずれのため、マ
ルテンサイトが生成せず、粗大なパーライトが生成し、
プレス成形性が劣化した。 Reference numerals 1 to 5 are steels according to the present invention, which have a high dynamic-static ratio and good press formability. In reference numeral 6, since C exceeded the upper limit, the second phase was hardened and press formability was deteriorated. In reference numeral 7, Si was out of the lower limit value, so solid solution strengthening of the ferrite phase was insufficient, and the static-dynamic ratio deteriorated. Reference numeral 8 indicates that the cooling rate during hot rolling was out of the upper limit value, so that ferrite was not formed, the concentration of C and Mn in austenite was insufficient, a coarse second phase was formed, and a static-dynamic ratio and press formability were obtained. Has deteriorated. Reference numeral 9 indicates that the winding temperature is out of the upper limit, so that martensite is not generated and coarse pearlite is generated,
Press moldability deteriorated.
【００２４】[0024]
【発明の効果】本発明によれば、加工性が優れ、かつ高
歪速度時の変形抵抗に優れた自動車用高張力熱延鋼板を
得ることができる。このことにより自動車の耐衝突性が
高まり、さらに高強度化により、板厚低減し、車体重量
を軽減することも可能となり、工業的価値は極めて高
い。According to the present invention, it is possible to obtain a high-strength hot-rolled steel sheet for automobiles which is excellent in workability and deformation resistance at a high strain rate. As a result, the collision resistance of the automobile is enhanced, and the strength of the automobile is further increased to reduce the plate thickness and reduce the weight of the vehicle body, which is extremely high in industrial value.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平６−65677（ＪＰ，Ａ) 特開 平６−264185（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 301 C22C 38/06 C22C 38/58 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-65677 (JP, A) JP-A-6-264185 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) C22C 38/00 301 C22C 38/06 C22C 38/58
Claims (2)
を溶製し、連続鋳造してスラブとした後、加熱炉に挿入
することなく熱間圧延するか、または加熱炉にてスラブ
を１２５０℃以下に加熱した後に熱間圧延を行い、Ａｒ
3 点±４０℃で圧延を終了し、平均冷却速度１０〜８０
℃／ｓで冷却し、３５０℃以下で巻き取り、熱延鋼帯と
し、その鋼板の組織がマルテンサイトからなる第２相を
含み、フェライト相が８０％以上でかつフェライト相の
ビッカース硬さが１００以上であることを特徴とする高
歪速度時の変形抵抗に優れた自動車用高張力熱延鋼板の
製造方法。 1. C .: 0.04 to 0.15% Si: 0.5 to 1.8% Mn: 0.8 to 2.0% P: 0.025% or less S: 0.0. Steel containing 01% or less Al: 0.005 to 0.1% and the balance Fe and unavoidable impurity elements
Melted, continuously cast into a slab, and then inserted into a heating furnace
Without hot rolling or slab in heating furnace
Is heated to 1250 ° C or lower and hot-rolled to
Rolling is completed at 3 points ± 40 ° C, average cooling rate is 10-80
Cooled at ℃ / s and wound up at 350 ℃ or less
Then, the second phase of the steel sheet structure consisting of martensite
Includes 80% or more of the ferrite phase and
High Vickers hardness of 100 or more
High-strength hot-rolled steel sheet for automobiles with excellent deformation resistance at strain rate
Production method.
避的不純物元素からなる鋼を溶製し、連続鋳造してスラ
ブとした後、加熱炉に挿入することなく熱間圧延する
か、または加熱炉にてスラブを１２５０℃以下に加熱し
た後に熱間圧延を行い、Ａｒ 3 点±４０℃で圧延を終了
し、平均冷却速度１０〜８０℃／ｓで冷却し、３５０℃
以下で巻き取り、熱延鋼帯とし、その鋼板の組織がマル
テンサイトからなる第２相を含み、フェライト相が８０
％以上でかつフェライト相のビッカース硬さが１００以
上であることを特徴とする高歪速度時の変形抵抗に優れ
た自動車用高張力熱延鋼板の製造方法。 2. C .: 0.04 to 0.15% Si: 0.5 to 1.8% Mn: 0.8 to 2.0% P: 0.025% or less S: 0.0. 01% or less Al: 0.005-0.1% in addition to Cr: 0.05-0.5% Ca: 0.0005-0.01% Nb: 0.001-0.05% V: 0.0. 005 to 0.1% Ti: 0.005 to 0.05% Ni: 0.05 to 0.5% Mo: 0.05 to 1.0% One or more of these are contained, and the balance is Fe and unavoidable. Steel made of specific impurity elements is melted, continuously cast, and slurried.
And then hot rolling without inserting into the heating furnace
Or heat the slab to below 1250 ° C in a heating furnace
After that, hot rolling is performed, and the rolling is completed at Ar 3 points ± 40 ° C.
And cool at an average cooling rate of 10-80 ° C / s, 350 ° C
It is wound up below and made into a hot rolled steel strip, and the structure of the steel sheet is
Includes a second phase consisting of tensite and a ferrite phase of 80
% And the Vickers hardness of the ferrite phase is 100 or less.
Excellent resistance to deformation at high strain rates characterized by being above
For manufacturing high-strength hot-rolled steel sheet for automobiles.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13145196A JP3519869B2 (en) | 1996-05-27 | 1996-05-27 | High-strength hot-rolled steel sheet for automobiles having excellent deformation resistance at high strain rate and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13145196A JP3519869B2 (en) | 1996-05-27 | 1996-05-27 | High-strength hot-rolled steel sheet for automobiles having excellent deformation resistance at high strain rate and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09316596A JPH09316596A (en) | 1997-12-09 |
| JP3519869B2 true JP3519869B2 (en) | 2004-04-19 |
Family
ID=15058272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13145196A Expired - Fee Related JP3519869B2 (en) | 1996-05-27 | 1996-05-27 | High-strength hot-rolled steel sheet for automobiles having excellent deformation resistance at high strain rate and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3519869B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4369545B2 (en) * | 1998-11-30 | 2009-11-25 | 新日本製鐵株式会社 | Ferritic sheet steel with excellent strain rate dependency and automobile using the same |
-
1996
- 1996-05-27 JP JP13145196A patent/JP3519869B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09316596A (en) | 1997-12-09 |
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