JP2000273576A - High tensile strength cold rolled steel plate excellent in roll formability and bulking resistance - Google Patents
High tensile strength cold rolled steel plate excellent in roll formability and bulking resistanceInfo
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- JP2000273576A JP2000273576A JP11083926A JP8392699A JP2000273576A JP 2000273576 A JP2000273576 A JP 2000273576A JP 11083926 A JP11083926 A JP 11083926A JP 8392699 A JP8392699 A JP 8392699A JP 2000273576 A JP2000273576 A JP 2000273576A
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- ferrite
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、ロール成形性お
よび耐座屈性に優れた高張力冷延鋼板に関し、特にかか
る高張力冷延鋼板をロールフォーミングおよび曲げ加工
した場合にそれぞれ懸念される縁波および座屈の発生を
併せて防止しようとするものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-tensile cold-rolled steel sheet having excellent roll formability and buckling resistance, and more particularly to an edge which is concerned when the high-tensile cold-rolled steel sheet is roll-formed and bent. It is intended to prevent the occurrence of waves and buckling.
【０００２】[0002]
【従来の技術】近年、自動車の軽量化による燃費向上の
ために、自動車用バンパーの素材として高張力冷延鋼板
が使用されるようになってきた。また、最近では、製造
コスト低減の観点から、その製造方法についても大物の
一体成形化が指向されている。2. Description of the Related Art In recent years, high-strength cold-rolled steel sheets have been used as materials for automobile bumpers in order to improve fuel efficiency by reducing the weight of automobiles. In recent years, from the viewpoint of reduction in manufacturing cost, large-size integrated molding has been pursued for the manufacturing method.
【０００３】自動車用バンパーを一体成形するために
は、まず、ロールフォーミングで函型に成形したのち、
曲げ加工によって所定のカーブを付与する必要がある。
しかしながら、高張力冷延鋼板のロールフォーミングに
際しては、鋼板の縁部に、図１に示すような縁波が発生
し易いという問題があった。このような縁波の発生を防
止するには、鋼材の降伏応力（ＹＳ、0.2 ％耐力）を高
くすることが有効と考えられる。というのは、ＹＳが高
くなれば一般に弾性限も高くなって、変形時における長
手方向の塑性収縮を効果的に抑制できるからである。In order to integrally form an automobile bumper, first, it is formed into a box by roll forming.
It is necessary to give a predetermined curve by bending.
However, during roll forming of a high-tensile cold-rolled steel sheet, there was a problem that an edge wave as shown in FIG. 1 was easily generated at the edge of the steel sheet. In order to prevent the generation of such edge waves, it is considered effective to increase the yield stress (YS, 0.2% proof stress) of the steel material. This is because the higher the YS, the higher the elastic limit in general, and can effectively suppress the longitudinal plastic shrinkage during deformation.
【０００４】しかしながら、ＹＳを高くすると、ロール
フォーミング後の曲げ加工時に、図１に示したような座
屈の発生が懸念される。というのは、大物一体成形によ
り、プレス品の断面形状が大きくなるため、曲げ時に加
わる応力が座屈限界応力を上回るからであり、この傾向
は材料がハイテン化するに伴って強くなる。However, when YS is increased, buckling as shown in FIG. 1 may occur during bending after roll forming. The reason for this is that since the cross-sectional shape of the pressed product becomes large due to the large-piece integral molding, the stress applied during bending exceeds the buckling limit stress, and this tendency becomes stronger as the material becomes higher in tension.
【０００５】従って、上記したような曲げ加工時におけ
る座屈の発生を防止するためには、ＹＳを小さくするこ
とが有利なのであるが、前述したとおりＹＳを小さくす
ると今度はロールフォーミング時における縁波の発生が
避けられない。Therefore, in order to prevent the occurrence of buckling at the time of bending as described above, it is advantageous to reduce YS. Inevitable.
【０００６】[0006]
【発明が解決しようとする課題】上述したとおり、自動
車用バンパー等のように、高張力冷延鋼板をロールフォ
ーミングと曲げ加工を利用して製造する場合、ロールフ
ォーミングと曲げ加工に必要とされる特性は相反するこ
とから、従来、これら両工程に有利に適合する好適材料
は存在せず、その開発が望まれていた。この発明は、上
記の要請に有利に応えるもので、ロールフォーミング時
における縁波の発生および曲げ加工時における座屈の発
生の両者を効果的に防止することができる、ロール成形
性および耐座屈性に優れた高張力冷延鋼板を提案するこ
とを目的とする。As described above, when a high-tensile cold-rolled steel sheet is manufactured by using roll forming and bending such as an automobile bumper, the roll forming and bending are required. Since the properties are contradictory, there has been no suitable material that can be advantageously used in these two steps, and its development has been desired. The present invention advantageously satisfies the above-described requirements, and can effectively prevent both the generation of edge waves during roll forming and the occurrence of buckling during bending. The purpose is to propose a high-tensile cold-rolled steel sheet with excellent heat resistance.
【０００７】[0007]
【課題を解決するための手段】さて、発明者らは、上記
の目的を達成すべく鋭意研究を重ねた結果、ＹＳが小さ
くても、弾性限をＴＳとの兼ね合いで高くしてやれば、
すなわちＹＳと弾性限とのバランスを適切にとってやれ
ば、座屈のみならず縁波の発生を効果的に防止できるこ
との知見を得た。この発明は、上記の知見に立脚するも
のである。Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, even if YS is small, if the elastic limit is increased in consideration of TS,
That is, it has been found that if the balance between YS and the elastic limit is properly set, not only buckling but also generation of edge waves can be effectively prevented. The present invention is based on the above findings.
【０００８】すなわち、この発明は、鋼組織が、10％以
上（面積率、以下同じ）のフェライトを含むフェライト
とベイナイトの混合組織から主としてなり、降伏比（Ｙ
Ｒ）が75％以下、引張り強さ（ＴＳ）が 580 MPa以上で
かつ（弾性限／ＴＳ）比が45％以上であることを特徴と
するロール成形性および耐座屈性に優れた高張力冷延鋼
板である。That is, in the present invention, the steel structure is mainly composed of a mixed structure of ferrite and bainite containing 10% or more (area ratio, the same applies hereinafter) of ferrite, and the yield ratio (Y
R) of 75% or less, tensile strength (TS) of 580 MPa or more, and (elastic limit / TS) ratio of 45% or more, characterized by excellent roll formability and high buckling resistance. It is a cold rolled steel sheet.
【０００９】この発明において、鋼材としては、Ｃ：0.
03〜0.18wt％、Si：2.0 wt％以下、Mn：1.0 〜3.5 wt
％、Ｐ：0.05wt％以下、Ｓ：0.02wt％以下およびAl：0.
10wt％以下を含有する成分組成になるものが有利に適合
する。また、上記の成分組成に、さらにNb：0.005 〜0.
1 wt％、Ti：0.005 〜0.1 wt％およびCa：0.0001〜0.00
5 wt％のうちから選んだ少なくとも１種を添加すること
もできる。[0009] In the present invention, the steel material is C: 0.
03-0.18wt%, Si: 2.0wt% or less, Mn: 1.0-3.5wt
%, P: 0.05 wt% or less, S: 0.02 wt% or less, and Al: 0.
Those having a component composition containing 10 wt% or less are advantageously suitable. Further, in addition to the above component composition, Nb: 0.005 to 0.1
1 wt%, Ti: 0.005 to 0.1 wt% and Ca: 0.0001 to 0.00
At least one selected from 5 wt% can be added.
【００１０】[0010]
【発明の実施の形態】以下、この発明の解明経緯につい
て説明する。前述したとおり、発明者らは、ロールフォ
ーミング時および曲げ加工時における縁波および座屈の
発生の両者を効果的に防止するためには、ＹＳと弾性限
とのバランスを適切に設定することが重要であることの
知見を得た。そこで、ＹＳと弾性限との好適バランスに
ついて検討したところ、降伏比（ＹＲ）を75％以下にす
ると共に、（弾性限／ＴＳ）比を45％以上（ただし、引
張り強さ（ＴＳ）≧ 580 MPa）とすることが有効である
ことが判明した。ここに（弾性限／ＴＳ）比とは、（弾
性限／ＴＳ）×100 ％の値である。DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the invention will be described below. As described above, the present inventors have to appropriately set the balance between YS and the elastic limit in order to effectively prevent both edge waves and buckling during roll forming and bending. I learned that it is important. Then, when the suitable balance between YS and the elastic limit was examined, the yield ratio (YR) was set to 75% or less, and the (elastic limit / TS) ratio was set to 45% or more (provided that the tensile strength (TS) ≧ 580). MPa) was found to be effective. Here, the (elastic limit / TS) ratio is a value of (elastic limit / TS) × 100%.
【００１１】そこで、次に、発明者らは、上記したよう
なＹＳと弾性限との好適バランスをそなえる鋼材を得る
ための製造方法について研究を進めたところ、製造工程
中、特に鋼片の加熱温度、圧延条件および焼鈍温度を厳
密に管理して、鋼組織を、少なくとも10％以上のフェラ
イトを含むフェライトとベイナイトの混合組織（好まし
くは90％以上）とすることが重要であることが究明され
た。[0011] Then, the present inventors proceeded with research on a manufacturing method for obtaining a steel material having a suitable balance between YS and elastic limit as described above. It has been determined that it is important to control the temperature, rolling conditions and annealing temperature strictly and to make the steel structure a mixed structure of ferrite and bainite (preferably 90% or more) containing at least 10% or more of ferrite. Was.
【００１２】以下、本発明鋼板の好適製造条件について
説明する。まず、鋼のスラブ加熱温度は、通常よりも低
め好適には1100℃未満（好ましくは1000℃以上）に設定
してスラブ加熱を施したのち、熱間圧延終了温度が 850
〜950 ℃程度で熱間圧延を行うことが肝要である。とい
うのは、スラブ加熱温度が低目だと、鋼中に未固溶のNb
（NbＣ）やAl（AlＮ）が残存するが、かような未固溶成
分の影響でγ粒が細粒化し、しかも圧延温度も低目とす
れば、工程を通じて微細な結晶粒が得られ、ひいては最
終製品の（フェライト＋ベイナイト）主体の組織も均一
微細となり、併せてＹＳと弾性限との開きが小さくなる
ためである。この点、スラブ加熱温度が1100℃以上では
低い弾性限しか得られず、また熱間圧延終了温度が上記
の範囲を逸脱すると結晶粒の十分な細粒化が達成されな
いため、ＹＳと弾性限との開きが大きくなる。Hereinafter, preferred conditions for producing the steel sheet of the present invention will be described. First, the slab heating temperature of the steel is set lower than usual, preferably less than 1100 ° C. (preferably 1000 ° C. or more), and then the slab heating is performed.
It is important to perform hot rolling at about 950 ° C. This is because if the slab heating temperature is low, Nb
(NbC) and Al (AlN) remain, but if the γ grains are refined under the influence of such undissolved components and the rolling temperature is also low, fine crystal grains can be obtained throughout the process, Eventually, the structure mainly composed of (ferrite + bainite) of the final product is also uniform and fine, and the difference between YS and the elastic limit is reduced. In this regard, if the slab heating temperature is 1100 ° C. or higher, only a low elasticity limit can be obtained, and if the hot rolling end temperature deviates from the above range, sufficient grain refinement of the crystal grains cannot be achieved. Opening increases.
【００１３】上記の熱間圧延後、コイルに巻取るわけで
あるが、この巻取り温度は 550〜650 ℃程度とすること
が好ましい。というのは、巻取り温度が上記の範囲を外
れた場合には、結晶粒が均質化し難く、やはりＹＳと弾
性限との開きが大きくなるからである。After the above-mentioned hot rolling, the film is wound into a coil. The winding temperature is preferably set to about 550 to 650 ° C. This is because when the winding temperature is outside the above range, it is difficult to homogenize the crystal grains, and the gap between YS and the elastic limit also increases.
【００１４】ついで、冷間圧延を施すが、この冷延条件
については特に限定されることはなく、常法に従って実
施すれば良い。ちなみに、好適冷延圧下率は30〜70％で
あり、かかる圧延によって板厚：0.8〜2.4 mmの板材に
仕上げる。Next, cold rolling is performed. The conditions for the cold rolling are not particularly limited, and may be performed according to a conventional method. Incidentally, the preferred cold rolling reduction is 30 to 70%, and the rolling is finished to a sheet having a sheet thickness of 0.8 to 2.4 mm.
【００１５】上記の冷延後、焼鈍−冷却を施して所望の
（フェライト＋ベイナイト）混合組織の製品板とする
が、かかる焼鈍−冷却は次の条件で行うことが好まし
い。 ・焼鈍温度： 750〜850 ℃（α−γ２相域）この焼鈍温
度が低すぎるとベイナイトの形成が不十分となり、一方
高すぎるとベイナイトの形成が過多となる。 ・冷却第１段： 300℃±50℃まで15℃/s以上 100℃/s以
下程度の速度で冷却。 ・冷却第２段： 150〜200 ℃まで10〜50℃/min程度の速
度で冷却。 ・冷却第３段：以下、室温まで15℃/s以上程度の速度で
冷却。 冷却第１段において、冷却速度が遅すぎるとベイナイト
が形成され難く、一方早すぎるとマルテンサイト化し、
いずれにしても所望組織は得られない。また、冷却第２
段の冷却速度が上記の範囲を逸脱すると、第２相への十
分なＣの濃縮が達成されず、ベイナイトが形成され難く
なる。さらに、冷却第３段の冷却速度が遅いと、組織の
均一性が低下し、ＹＳと弾性限との開きが大きくなる。After the above-described cold rolling, annealing-cooling is performed to obtain a product sheet having a desired (ferrite + bainite) mixed structure. It is preferable that such annealing-cooling be performed under the following conditions. Annealing temperature: 750 to 850 ° C. (α-γ2 phase region) If the annealing temperature is too low, bainite formation is insufficient, while if it is too high, bainite formation is excessive.・ Cooling 1st stage: Cool to 300 ℃ ± 50 ℃ at a rate of 15 ℃ / s or more and 100 ℃ / s or less.・ Cooling second stage: Cooling to 150-200 ° C at a rate of about 10-50 ° C / min.・ Cooling third stage: cool down to room temperature at a rate of about 15 ° C / s or more. In the first cooling stage, if the cooling rate is too slow, it is difficult to form bainite, while if too fast, it becomes martensite,
In any case, the desired tissue cannot be obtained. In addition, the cooling second
If the cooling rate of the stage is outside the above range, sufficient concentration of C in the second phase will not be achieved, and bainite will not be easily formed. Further, when the cooling rate of the third cooling stage is low, the uniformity of the tissue is reduced, and the gap between YS and the elastic limit becomes large.
【００１６】かくして、10％以上のフェライトを含む
（フェライト＋ベイナイト）混合組織から主としてな
り、しかも、降伏比（ＹＲ）が75％以下、引張り強さ
（ＴＳ）が580 MPa以上でかつ（弾性限／ＴＳ）比が45
％以上の高張力冷延鋼板が得られるのである。Thus, it is mainly composed of a (ferrite + bainite) mixed structure containing 10% or more of ferrite, and has a yield ratio (YR) of 75% or less, a tensile strength (TS) of 580 MPa or more and (elastic limit). / TS) ratio is 45
% Or more of a high-tensile cold-rolled steel sheet can be obtained.
【００１７】ここに、鋼組織において、フェライトの量
を10％以上に限定したのは、フェライト量が10％に満た
ないと延性が低下し、ロール加工が困難になるだけでな
く、ＹＲが上昇し座屈し易くなるからである。特に好適
なフェライト量は20〜70％である。また、（フェライト
＋ベイナイト）混合組織は、組織全体の90％以上とする
ことが有利である。なお、この発明において、フェライ
トとベイナイトの他、少量であれば（10％未満）マルテ
ンサイトや残留オーステナイト等を含有していもかまわ
ない。また、結晶粒径については 4.0μm 以下程度とす
ることが好ましい。Here, the reason why the amount of ferrite is limited to 10% or more in the steel structure is that when the amount of ferrite is less than 10%, the ductility is reduced and not only the roll working becomes difficult but also the YR is increased. This is because it becomes easy to buckle. A particularly preferred amount of ferrite is 20-70%. It is advantageous that the (ferrite + bainite) mixed structure is 90% or more of the entire structure. In the present invention, besides ferrite and bainite, a small amount (less than 10%) of martensite or retained austenite may be contained. Further, the crystal grain size is preferably about 4.0 μm or less.
【００１８】次に、この発明において、ＹＲを75％以下
に限定したのは、曲げ加工時における座屈の発生を効果
的に防止するためである。より好ましくは73％以下であ
る。また、（弾性限／ＴＳ）比を45％以上に限定したの
は、ロールフォーミング時における縁波の発生を効果的
に防止するためである。より好ましくは50％以上であ
る。さらに、ＴＳを 580 MPa以上に限定したのは、この
程度の高張力範囲においてこの発明の効果が著しいから
である。なお、ＴＳは 780 MPa以上が特に効果的で好ま
しい。Next, in the present invention, YR is limited to 75% or less in order to effectively prevent buckling during bending. It is more preferably at most 73%. The reason why the (elasticity limit / TS) ratio is limited to 45% or more is to effectively prevent generation of edge waves during roll forming. It is more preferably at least 50%. Further, the reason why the TS is limited to 580 MPa or more is that the effect of the present invention is remarkable in such a high tension range. Note that TS is particularly effective and preferably 780 MPa or more.
【００１９】次に、この発明鋼の好適成分組成について
説明する。 Ｃ：0.03〜0.18wt％ Ｃは、強度の向上に有効に寄与するが、含有量が0.03wt
％に満たないとその添加効果に乏しく、一方0.18wt％を
超えると加工性や溶接性、耐衝撃特性が著しく劣化する
ので、Ｃ量は0.03〜0.18wt％程度が好適である。Next, the preferred composition of the steel of the present invention will be described. C: 0.03 to 0.18 wt% C effectively contributes to the improvement of strength, but the content is 0.03 wt%
%, The effect of the addition is poor. On the other hand, if it exceeds 0.18 wt%, the workability, weldability and impact resistance are remarkably deteriorated, so that the C content is preferably about 0.03 to 0.18 wt%.
【００２０】Si：2.0 wt％以下 Siは、強度を向上させる有用元素であるが、含有量が
2.0wt％を超えると加工性の劣化を招くので、Si量は 2.
0wt％以下程度とするのが好ましい。なお、鋼の清浄度
の観点からは 0.005wt％以上含有させることが好まし
い。Si: 2.0 wt% or less Si is a useful element for improving strength, but its content is
If the content exceeds 2.0 wt%, the workability will be degraded.
It is preferable that the content be about 0 wt% or less. In addition, from the viewpoint of the cleanliness of steel, the content is preferably 0.005 wt% or more.
【００２１】Mn：1.0 〜3.5 wt％ Mnは、Ｓを固定してＳに起因した熱間割れの発生を防止
するだけでなく、強度の改善成分としても有効である。
しかしながら、含有量が 1.0wt％に満たないとその添加
効果に乏しく、一方 3.5wt％を超えると加工性および溶
接性が劣化するので、Mn量は 1.0〜3.5 wt％程度とする
のが好適である。Mn: 1.0 to 3.5 wt% Mn is effective not only for fixing S to prevent the occurrence of hot cracking due to S, but also as a component for improving strength.
However, if the content is less than 1.0 wt%, the effect of the addition is poor, while if it exceeds 3.5 wt%, the workability and weldability deteriorate, so the Mn content is preferably about 1.0 to 3.5 wt%. is there.
【００２２】Ｐ：0.05wt％以下 Ｐは、多量に含有されると、その偏析によって割れの発
生が懸念されるので、Ｐの含有は極力低減する必要があ
るが、0.05wt％以下で許容される。より好ましくは0.02
wt％以下である。P: 0.05 wt% or less If P is contained in a large amount, there is a concern that cracking may occur due to its segregation. Therefore, it is necessary to reduce the content of P as much as possible. You. More preferably 0.02
wt% or less.
【００２３】Ｓ：0.02wt％以下 Ｓが多量に含有されると伸びフランジ性が劣化するので
Ｓの含有は極力低減する必要があるが、0.02wt％以下で
許容される。より好ましくは 0.005wt％以下である。S: 0.02 wt% or less If a large amount of S is contained, the stretch flangeability deteriorates. Therefore, the content of S needs to be reduced as much as possible, but is allowed to be 0.02 wt% or less. More preferably, it is 0.005 wt% or less.
【００２４】Al：0.10wt％以下 Alは、脱酸剤として有効に寄与するが、含有量が0.10wt
％を超えると加工性の劣化を招くので、0.10wt％以下程
度で含有させることが好ましい。より好適には0.02〜0.
06wt％程度である。Al: 0.10 wt% or less Al effectively contributes as a deoxidizing agent, but the content is 0.10 wt%.
%, The workability is degraded. Therefore, it is preferable that the content is about 0.10 wt% or less. More preferably 0.02--0.
It is about 06 wt%.
【００２５】以上、基本成分について説明したが、この
発明ではさらに、以下に述べる元素を添加することがで
きる。 Nb：0.005 〜0.1 wt％ Nbは、鋼組織を細粒化して強度や加工性を向上させるだ
けでなく、低ＹＲや高弾性限を達成する上でも有効な元
素である。しかしながら、含有量が 0.005wt％に満たな
いとその添加効果に乏しく、一方 0.1wt％を超えると加
工性が劣化するので、Nb量は 0.005〜0.1 wt％程度とす
るのが好ましい。The basic components have been described above. In the present invention, the following elements can be further added. Nb: 0.005 to 0.1 wt% Nb is an element that is effective not only to refine the steel structure to improve strength and workability but also to achieve a low YR and a high elastic limit. However, if the content is less than 0.005 wt%, the effect of the addition is poor, while if it exceeds 0.1 wt%, the workability is deteriorated. Therefore, the Nb content is preferably set to about 0.005 to 0.1 wt%.
【００２６】Ti：0.005 〜0.1 wt％ Tiは、Nbと同様、高組織の細粒化および強度や加工性の
向上、さらには低ＹＲ、高弾性限の実現に有効に寄与す
るが、含有量が 0.005wt％に満たないとその添加効果に
乏しく、一方 0.1wt％を超えると加工性が劣化するの
で、Ti量は 0.005〜0.1 wt％程度とするのが好ましい。Ti: 0.005 to 0.1 wt% Ti, like Nb, effectively contributes to fine grain refinement of a high structure, improvement of strength and workability, and realization of low YR and high elasticity limit. If the content is less than 0.005 wt%, the effect of the addition is poor. On the other hand, if the content exceeds 0.1 wt%, the workability deteriorates. Therefore, the Ti content is preferably about 0.005 to 0.1 wt%.
【００２７】Ca：0.0001〜0.005 wt％ Caは、硫化物の形態制御に有効に寄与し、特に伸びフラ
ンジ性の向上させる有用元素であるが、含有量が0.0001
wt％に満たないとその添加効果に乏しく、一方0.005 wt
％を超えると加工性の劣化を招くので、Ca量は0.0001〜
0.005 wt％程度とするのが好ましい。Ca: 0.0001 to 0.005 wt% Ca is a useful element that effectively contributes to morphological control of sulfides and is particularly useful for improving stretch flangeability.
If it is less than wt%, its effect is poor, while 0.005 wt%
%, The workability is degraded.
Preferably, the content is about 0.005 wt%.
【００２８】その他、この発明では必要に応じて、以下
に述べる元素をさらに添加することができる。 Crおよび／またはMo：0.01〜1.0 wt％ CrおよびMoはいずれも、焼入性改善による組織制御に有
効に寄与するが、含有量が0.01wt％に満たないとその添
加効果に乏しく、一方 1.0wt％を超えると硬化が著しく
なるので、0.01〜1.0 wt％の範囲で含有させることが好
ましい。In the present invention, the following elements can be further added as required. Cr and / or Mo: 0.01 to 1.0 wt% Both Cr and Mo effectively contribute to the structure control by improving the hardenability, but if the content is less than 0.01 wt%, the effect of the addition is poor. If the content exceeds wt%, the curing becomes remarkable. Therefore, it is preferable that the content be in the range of 0.01 to 1.0 wt%.
【００２９】Ｂ，Cu，Ni，Ｗ，Co、Ｖおよび／またはZ
r：1.0 wt％以下 これらの元素はいずれも、強度の向上に有効に寄与する
元素であるが、あまりに多く添加すると加工性が劣化す
るので、単独添加または複合添加いずれの場合も 1.0wt
％以下程度で添加することが好ましい。B, Cu, Ni, W, Co, V and / or Z
r: 1.0 wt% or less Each of these elements is an element that effectively contributes to the improvement of strength. However, if too much is added, the workability is deteriorated.
% Is preferable.
【００３０】なお、上記した元素以外には、不可避的不
純物の含有が許容されるが、かかる不純物の混入量は合
計で 0.2wt％以下とすることが好ましい。In addition to the above-mentioned elements, unavoidable impurities may be contained, but the total amount of such impurities is preferably 0.2 wt% or less.
【００３１】表１に示す成分組成になる鋼スラブ（厚
み：220 mm）を、表２に示す条件で処理し、厚み：1.2
mmの冷延鋼板を得た。かくして得られた高張力冷延鋼板
の鋼組織および機械的性質、さらにはロール成形性およ
び耐座屈性について調べた結果を、表３に示す。なお、
ロール成形性および耐座屈性は、冷延鋼板を断面が50×
100 mmの角パイプにロール成形したのち、そのまま2000
mmR で曲げ加工した際の、ロールフォーミング時におけ
る縁波発生の有無および曲げ加工時における座屈発生の
有無で評価した。A steel slab (thickness: 220 mm) having the composition shown in Table 1 was treated under the conditions shown in Table 2 to obtain a steel slab having a thickness of 1.2 mm.
mm cold-rolled steel sheet was obtained. Table 3 shows the results obtained by examining the steel structure and mechanical properties of the high-tensile cold-rolled steel sheet thus obtained, as well as the roll formability and buckling resistance. In addition,
The roll formability and buckling resistance are as follows:
After roll forming into a 100 mm square pipe, 2000
Evaluation was made based on the presence or absence of edge waves during roll forming and the occurrence of buckling during bending when bending at mmR.
【００３２】[0032]
【表１】 [Table 1]
【００３３】[0033]
【表２】 [Table 2]
【００３４】[0034]
【表３】 [Table 3]
【００３５】表３に示したとおり、この発明に従い得ら
れた冷延鋼板は、ロールフォーミングおよび曲げ加工時
において、縁波および座屈の発生が皆無であり、良好な
ロール成形性および耐座屈性が得られていることが分か
る。As shown in Table 3, the cold rolled steel sheet obtained according to the present invention has no edge wave and no buckling during roll forming and bending, and has good roll formability and buckling resistance. It can be seen that the property has been obtained.
【００３６】[0036]
【発明の効果】かくして、この発明によれば、ＹＳと弾
性限の適切なバランスをとることにより、従来、相反す
る性質とされたロール成形性および耐座屈性を兼ね備え
た高張力冷延鋼板を得ることができ、従って、かかる高
張力冷延鋼板にロールフォーミングおよび曲げ加工を施
した場合に従来懸念された縁波および座屈の発生を効果
的に防止することができる。Thus, according to the present invention, by appropriately balancing YS with the elastic limit, a high-tensile cold-rolled steel sheet having both roll forming properties and buckling resistance, which are conventionally contradictory properties, is obtained. Therefore, it is possible to effectively prevent the occurrence of edge waves and buckling, which have conventionally been concerned when such a high-tensile cold-rolled steel sheet is subjected to roll forming and bending.
【図１】 ロールフォーミング時における縁波の発生状
況および曲げ加工時における座屈の発生状況を示した図
である。FIG. 1 is a diagram showing a state of occurrence of edge waves during roll forming and a state of occurrence of buckling during bending.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 川邊 英尚 千葉県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 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidenao Kawabe 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref.
Claims (3)
フェライトとベイナイトの混合組織から主としてなり、
降伏比（ＹＲ）が75％以下、引張り強さ（ＴＳ）が 580
MPa以上でかつ（弾性限／ＴＳ）比が45％以上であるこ
とを特徴とするロール成形性および耐座屈性に優れた高
張力冷延鋼板。The steel structure mainly comprises a mixed structure of ferrite and bainite containing 10% or more of ferrite,
Yield ratio (YR) is 75% or less and tensile strength (TS) is 580
A high-tensile cold-rolled steel sheet excellent in roll formability and buckling resistance, characterized in that the ratio is not less than MPa and the (elastic limit / TS) ratio is not less than 45%.
よび耐座屈性に優れた高張力冷延鋼板。2. The steel composition according to claim 1, wherein the composition of steel is C: 0.03 to 0.18 wt%, Si: 2.0 wt% or less, Mn: 1.0 to 3.5 wt%, P: 0.05 wt% or less, S: 0.02 wt%. A high-tensile cold-rolled steel sheet excellent in roll formability and buckling resistance, characterized by having a composition containing the following and Al: 0.10 wt% or less.
らに Nb：0.005 〜0.1 wt％、 Ti：0.005 〜0.1 wt％および Ca：0.0001〜0.005 wt％ のうちから選んだ少なくとも１種を含有する組成になる
ことを特徴とするロール成形性および耐座屈性に優れた
高張力冷延鋼板。3. The steel composition according to claim 2, wherein the steel further contains at least one selected from the group consisting of Nb: 0.005 to 0.1 wt%, Ti: 0.005 to 0.1 wt%, and Ca: 0.0001 to 0.005 wt%. A high-tensile cold-rolled steel sheet excellent in roll formability and buckling resistance, characterized in that it has a composition that makes it possible to obtain a high tensile strength.
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|---|---|---|---|
| JP08392699A JP3799868B2 (en) | 1999-03-26 | 1999-03-26 | High-tensile cold-rolled steel sheet with excellent roll formability and buckling resistance |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08392699A JP3799868B2 (en) | 1999-03-26 | 1999-03-26 | High-tensile cold-rolled steel sheet with excellent roll formability and buckling resistance |
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| Publication Number | Publication Date |
|---|---|
| JP2000273576A true JP2000273576A (en) | 2000-10-03 |
| JP3799868B2 JP3799868B2 (en) | 2006-07-19 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004332100A (en) * | 2003-04-17 | 2004-11-25 | Nippon Steel Corp | High-strength thin steel sheet superior in hydrogen embrittlement resistance, weldability, and hole-expandability and manufacturing method therefor |
| JP2023506743A (en) * | 2019-12-09 | 2023-02-20 | ポスコホールディングス インコーポレーティッド | Structural steel plate with excellent seawater resistance and manufacturing method thereof |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111961967B (en) * | 2020-07-31 | 2021-09-21 | 天津钢铁集团有限公司 | Steel plate for small-compression-ratio thick-specification controlled rolling type Q345GJE building structure and production method thereof |
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1999
- 1999-03-26 JP JP08392699A patent/JP3799868B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004332100A (en) * | 2003-04-17 | 2004-11-25 | Nippon Steel Corp | High-strength thin steel sheet superior in hydrogen embrittlement resistance, weldability, and hole-expandability and manufacturing method therefor |
| JP2023506743A (en) * | 2019-12-09 | 2023-02-20 | ポスコホールディングス インコーポレーティッド | Structural steel plate with excellent seawater resistance and manufacturing method thereof |
| JP7429782B2 (en) | 2019-12-09 | 2024-02-08 | ポスコホールディングス インコーポレーティッド | Structural steel plate with excellent seawater resistance and manufacturing method thereof |
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| Publication number | Publication date |
|---|---|
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