JPH08311601A - Ultrahigh strength steel sheet excellent in delayed fracture resistance and its production - Google Patents
Ultrahigh strength steel sheet excellent in delayed fracture resistance and its productionInfo
- Publication number
- JPH08311601A JPH08311601A JP12138795A JP12138795A JPH08311601A JP H08311601 A JPH08311601 A JP H08311601A JP 12138795 A JP12138795 A JP 12138795A JP 12138795 A JP12138795 A JP 12138795A JP H08311601 A JPH08311601 A JP H08311601A
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- Prior art keywords
- steel sheet
- strength steel
- group
- element selected
- high strength
- Prior art date
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、耐遅れ破壊特性にすぐ
れる引張強度１１８０ＭＰａ以上の超高強度鋼板及びそ
の製造方法に関する。本発明によるこのような超高強度
鋼板、特に、薄鋼板は、例えば、パイプ用途として、自
動車のドアの補強部材等、軽量で且つ強度が要求される
用途や、また、Ｚｎ、Ｃｄ、Ｓｎ、Ａｌ、Ｃｒ、Ｎｉ、
Ｐｂ等のめっき処理や、クロメート処理、リン酸塩処理
等の化成処理、更には、有機塗装による防食表面処理を
施して、厳しい腐食環境において、種々の用途に好適に
用いることができる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrahigh-strength steel sheet having a tensile strength of 1180 MPa or more which is excellent in delayed fracture resistance and a method for producing the same. Such an ultra-high strength steel sheet according to the present invention, in particular, a thin steel sheet, is used for pipes, for example, as a reinforcing member for automobile doors, where light weight and strength are required, and Zn, Cd, Sn, Al, Cr, Ni,
It can be suitably used for various applications in a severe corrosive environment by performing a plating treatment such as Pb, a chemical conversion treatment such as a chromate treatment and a phosphate treatment, and an anticorrosion surface treatment by an organic coating.
【０００２】[0002]
【従来の技術】地球の環境保全の観点から、最近、自動
車の燃費の改善要求が強い。そこで、車体の軽量化を図
るべく、バンパー、ドアのインパクト・ビーム等、自動
車の種々の補強部材用途に引張強度１１８０ＭＰａ以上
の超高強度薄鋼板のニーズが強くなっている。しかし、
１１８０ＭＰａ以上の強度を有する超高強度鋼を用いた
ボルトにおいては、水素脆化による割れ、所謂遅れ破壊
が発生することが、例えば、特開昭６０−１５５６４４
号公報等に記載されているように、既に知られている。
従って、超高強度薄鋼板を用いた種々の部材において
も、大気環境下の腐食反応によって発生する水素が鋼板
中に入って、使用中に突然破壊するおそれがある。2. Description of the Related Art Recently, from the viewpoint of environmental protection of the earth, there is a strong demand for improvement of fuel efficiency of automobiles. Therefore, in order to reduce the weight of the vehicle body, there is an increasing need for ultra-high-strength thin steel sheets having a tensile strength of 1180 MPa or more for various reinforcing member applications such as bumpers and door impact beams. But,
In bolts made of ultra-high strength steel having a strength of 1180 MPa or more, hydrogen embrittlement may cause cracking, so-called delayed fracture, for example, as disclosed in Japanese Patent Laid-Open No. 60-155644.
It is already known as described in Japanese Patent Publication No.
Therefore, even in various members using the ultra-high-strength thin steel plate, hydrogen generated by a corrosion reaction in the atmospheric environment may enter the steel plate and be suddenly broken during use.
【０００３】超高強度薄鋼板の遅れ破壊の防止について
は、特開平４−２６８０５３号公報に記載されているよ
うに、鋼中にＳｉを添加し、鋼板中への水素原子の侵入
を制御することによって、遅れ破壊の原因である水素脆
化の発生を防止する方法が提案されている。しかし、遅
れ破壊の発生要因は、必ずしも水素侵入に限られている
ものではなく、腐食ピット形成による応力集中も大きな
要因となる。従って、Ｓｉ添加のみによって、遅れ破壊
の発生を十分に防止することは困難である。In order to prevent delayed fracture of an ultra-high strength thin steel sheet, Si is added to the steel to control the penetration of hydrogen atoms into the steel sheet, as described in JP-A-4-268053. Therefore, a method of preventing hydrogen embrittlement, which is a cause of delayed fracture, has been proposed. However, the cause of delayed fracture is not necessarily limited to hydrogen invasion, and stress concentration due to the formation of corrosion pits is also a major factor. Therefore, it is difficult to sufficiently prevent the occurrence of delayed fracture only by adding Si.
【０００４】また、特開平４−２８０９４０号公報に
は、点溶接部の耐水割れ性の改善について記載されてい
るが、３％以上のＮｉの添加を必要とし、コストの上昇
を招くので、実用的ではない。また、母材部の耐水割れ
特性については、何も言及されていない。更に、特開平
５−２９５４８１号公報には、鋼にＣａを添加し、圧延
方向に伸展したＭｎＳを球状のＣａＳに変えることによ
って、オーステナイト結晶粒界の結合力を強め、耐水素
脆化特性を向上させることが提案されている。遅れ破壊
は、特に、割れの起点部において、結晶粒界割れの形態
を示すことが多いが、しかし、破壊の全過程が粒界割れ
であることは殆どなく、従って、結晶粒界の強化は、総
括的な対策とはなり得ない。Further, Japanese Patent Laid-Open No. 4-280940 describes improvement in resistance to water cracking of spot welds, but it requires addition of 3% or more of Ni, resulting in cost increase. Not at all. Further, nothing is mentioned about the water crack resistance of the base material. Further, in JP-A-5-295481, by adding Ca to steel and changing MnS extended in the rolling direction into spherical CaS, the binding force of austenite grain boundaries is strengthened and hydrogen embrittlement resistance is improved. It is proposed to improve. Delayed fracture often exhibits the form of grain boundary cracking, especially at the starting point of cracking, but the entire process of fracture is rarely intergranular cracking, and therefore strengthening of grain boundary is , Cannot be a comprehensive measure.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、引張強度が
１１８０ＭＰａ以上の超高強度薄鋼板における上記のよ
うな遅れ破壊の問題を解決するためのものであって、耐
遅れ破壊特性にすぐれる超高強度鋼板、特に、薄鋼板
と、その製造方法を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problem of delayed fracture in an ultra-high strength thin steel sheet having a tensile strength of 1180 MPa or more and is excellent in delayed fracture resistance. It is an object of the present invention to provide an ultra-high strength steel plate, particularly a thin steel plate, and a method for manufacturing the same.
【０００６】[0006]
【課題を解決するための手段】本発明による耐遅れ破壊
特性にすぐれる超高強度鋼板は、重量％にてＣ 0.０
８〜0.３０％、Ｓｉ 1.０％未満、Ｍｎ 1.５〜3.０
％、Ｓ 0.０１０％以下、Ｐ 0.０３〜0.１５％、
Ｃｕ 0.１０〜1.００％、及びＮｉ 0.１０〜4.００％
を含み、残部鉄及び不可避的不純物よりなり、マルテン
サイト、焼戻しマルテンサイト又はベイナイト組織のい
ずれか１種以上を体積率にて４０％以上含み、強度が１
１８０ＭＰａ以上であることを特徴とする。The ultrahigh-strength steel sheet excellent in delayed fracture resistance according to the present invention has a weight percentage of C 0.0.
8 to 0.30%, Si less than 1.0%, Mn 1.5 to 3.0
%, S 0.010% or less, P 0.03 to 0.15%,
Cu 0.10 to 1.00%, and Ni 0.10 to 4.00%
Containing 40% or more by volume of any one or more of martensite, tempered martensite, and bainite structure, and having a strength of 1
It is characterized by being 180 MPa or more.
【０００７】本発明によるこのような超高強度鋼板は、
本発明に従って、上記元素を含み、残部鉄及び不可避的
不純物よりなる鋼スラブを１１００℃以上の温度に加熱
し、６００℃以下の温度で巻取る熱間圧延を行なった
後、酸洗し、スケールを除き、冷間圧延を行ない、次い
で、連続焼鈍を行なうに際して、８００℃以上、１００
０℃以下の範囲の温度にて均熱した後、３０℃／秒以下
の冷却速度にて、８００〜６５０℃の範囲の温度まで徐
冷し、次いで、この温度から７０℃／秒以上の冷却速度
にて４００℃以下の温度まで冷却し、この後、再加熱す
るか、又はそのまま、１５０〜４００℃の範囲の温度で
１〜２０分間加熱する焼戻し処理を行なうことによって
得ることができる。Such an ultra high strength steel sheet according to the present invention is
According to the present invention, a steel slab containing the above elements and comprising the balance iron and unavoidable impurities is heated to a temperature of 1100 ° C. or higher, and hot rolling is performed at a temperature of 600 ° C. or lower, followed by pickling and scaling. Except the above, cold rolling is performed, and then continuous annealing is performed
After soaking at a temperature in the range of 0 ° C. or less, it is gradually cooled to a temperature in the range of 800 to 650 ° C. at a cooling rate of 30 ° C./s or less, and then cooled from this temperature to 70 ° C./s or more. It can be obtained by cooling to a temperature of 400 ° C. or lower at a speed and then reheating or performing a tempering treatment in which it is heated at a temperature in the range of 150 to 400 ° C. for 1 to 20 minutes.
【０００８】先ず、本発明において、鋼板の有する化学
成分の範囲及びその理由は、次のとおりである。Ｃは、
鋼板中にマルテンサイト組織等の所要組織を生成し、鋼
板を高強度化するために必須の元素であり、特に、本発
明に従って、１１８０ＭＰａ以上の引張強度を得るため
には、少なくとも0.０８％の添加が必要である。しか
し、添加量が0.３０％を越えるときは、加工性を低下さ
せたり、或いは耐食性の劣化等が原因となって、耐水素
脆化特性の劣化が促進されることもある。特に、本発明
においては、鋼板の強度及び耐食性の観点から、Ｃ量
は、0.１２〜0.２０％の範囲がより好ましい。First, in the present invention, the range of the chemical composition of the steel sheet and the reason therefor are as follows. C is
It is an essential element for producing a required structure such as a martensite structure in a steel sheet and increasing the strength of the steel sheet. Particularly, in order to obtain a tensile strength of 1180 MPa or more according to the present invention, at least 0.08% Is required. However, if the addition amount exceeds 0.30%, deterioration of hydrogen embrittlement resistance may be accelerated due to deterioration of workability or deterioration of corrosion resistance. Particularly, in the present invention, the amount of C is more preferably in the range of 0.12 to 0.20% from the viewpoint of the strength and corrosion resistance of the steel sheet.
【０００９】Ｓｉは、延性を劣化させることなく、鋼を
固溶強化するために有効な元素である。しかし、添加量
が1.０％以上であるときは、その効果が飽和するのみな
らず、塗装性が低下する。そこで、本発明においては、
Ｓｉ量は1.０％未満とする。Ｍｎは、鋼の焼入性を高め
る元素であって、連続焼鈍設備においてマルテンサイト
を安定に生じさせるためには、1.５％以上の添加が必要
である。しかし、3.０％を越えるときは、その効果が飽
和するのみならず、偏析が大きくなり、組織が不均一と
なり、加工性が低下するので、添加量は3.０％を上限と
する。Si is an element effective for solid solution strengthening steel without deteriorating ductility. However, when the addition amount is 1.0% or more, not only the effect is saturated but also the coating property is deteriorated. Therefore, in the present invention,
The amount of Si is less than 1.0%. Mn is an element that enhances the hardenability of steel, and must be added in an amount of 1.5% or more in order to stably generate martensite in continuous annealing equipment. However, if it exceeds 3.0%, not only the effect is saturated, but also segregation becomes large, the structure becomes nonuniform, and the workability is deteriorated. Therefore, the upper limit of the addition amount is 3.0%.
【００１０】Ｓは、Ｍｎ等と介在物を形成して、腐食発
生の起点となると共に、曲げ加工性等を劣化させるの
で、0.０１０％以下に規制する。特に好ましくは、0.０
０５％以下である。Ｐは、本発明に従って、Ｃｕと共に
添加することによって、生成錆を緻密化し、大気腐食環
境下における鋼の腐食速度を著しく低下するのに有効で
ある。また、Ｐは、鋼の強度や延性を高めるのにも有効
である。本発明によれば、これらの効果を有効に得るた
めには、Ｐを0.０３％以上添加することが必要である。
しかし、Ｐは、一方において、粒界に偏析しやすく、粒
界強度を低下させるおそれもあるので、添加量の上限を
0.１５％とする。特に、耐食性の向上と脆化抑制の観点
から、Ｐの添加量の上限は、0.０７％が好ましい。Since S forms an inclusion with Mn and the like to serve as a starting point of corrosion generation and deteriorate bending workability and the like, S is restricted to 0.010% or less. Particularly preferably, 0.0
It is less than 05%. According to the present invention, P is effective in densifying the generated rust and significantly reducing the corrosion rate of steel in an atmospheric corrosive environment by adding together with Cu. Further, P is also effective in increasing the strength and ductility of steel. According to the present invention, in order to effectively obtain these effects, it is necessary to add P in an amount of 0.03% or more.
However, on the one hand, P tends to segregate at the grain boundaries and may lower the grain boundary strength.
It is set to 0.15%. Particularly, from the viewpoint of improving corrosion resistance and suppressing embrittlement, the upper limit of the amount of P added is preferably 0.07%.
【００１１】Ｃｕは、本発明に従って、微量のＰと同時
に添加することによって、生成錆を緻密化し、大気腐食
環境下における鋼の腐食速度を著しく低減する。また、
Ｃｕは、電気化学的に鉄よりも貴であるところから、上
記と共に、相乗的に鋼の耐食性を向上させる。このよう
な効果を有効に得るためには、少なくとも0.１０％を添
加することが必要である。しかし、他方において、Ｃｕ
は、熱間圧延時の脆化を引き起こすおそれがあるので、
添加量の上限を1.００％とする。また、Ｃｕ添加による
上記熱間圧延時の脆化を防止するには、後述するよう
に、等量程度のＮｉを同時に添加することが好ましい。
本発明によれば、実用上の観点から、Ｃｕの添加量は、
特に、0.２０〜0.６０％の範囲が好ましい。According to the present invention, Cu densifies the formed rust by adding it together with a trace amount of P, and significantly reduces the corrosion rate of steel in an atmospheric corrosive environment. Also,
Since Cu is electrochemically nobler than iron, it synergistically improves the corrosion resistance of steel together with the above. In order to effectively obtain such effects, it is necessary to add at least 0.10%. But on the other hand, Cu
May cause embrittlement during hot rolling,
The upper limit of the amount added is 1.00%. Further, in order to prevent the embrittlement during the hot rolling due to the addition of Cu, it is preferable to add approximately the same amount of Ni at the same time, as described later.
According to the present invention, from the practical viewpoint, the added amount of Cu is
Particularly, the range of 0.20 to 0.60% is preferable.
【００１２】Ｎｉは、0.１％以上を添加することによっ
て、生成錆の緻密化により、鋼の耐食性を向上させる効
果を有する。しかし、過多に添加するときは、残留オー
ステナイトの増加による引張強度の低下原因となるの
で、上限を4.００％とする。また、Ｎｉは、Ｃｕ添加の
際の熱延脆性を抑制する効果をもつので、上述したよう
に、Ｃｕと等量程度添加することが望ましい。しかしな
がら、Ｎｉは高価な金属であり、経済性の点から考慮す
れば、より好ましい添加範囲は、2.００％以下である。When Ni is added in an amount of 0.1% or more, it has the effect of improving the corrosion resistance of steel by densifying the generated rust. However, if too much is added, it causes a decrease in tensile strength due to an increase in retained austenite, so the upper limit is made 4.00%. Further, since Ni has an effect of suppressing hot rolling embrittlement when Cu is added, it is desirable to add Ni in the same amount as Cu as described above. However, Ni is an expensive metal, and a more preferable addition range is 2.00% or less from the viewpoint of economy.
【００１３】本発明によれば、鋼板は、上記元素に加え
て、Ｔｉ 0.０１〜0.５０％、及びＣｒ 0.１０〜5.０
０％よりなる群から選ばれる少なくとも１種の元素を含
むことができる。According to the present invention, the steel sheet has, in addition to the above elements, Ti 0.01 to 0.50% and Cr 0.10 to 5.0.
It may contain at least one element selected from the group consisting of 0%.
【００１４】Ｔｉは、結晶粒の細粒化と粒成長抑制効果
とを有し、鋼素材の水素脆性感受性を低下させ、更に
は、生成錆の緻密化の効果も有して、耐食性を向上させ
る。これらの効果を有効に得るためには、少なくとも0.
０１％の添加が必要である。しかし、過多に添加すると
きは、Ｃとの析出物を形成し、所定の強度を得ることが
できなくなるので、添加量の上限を0.５０％とする。特
に、本発明においては、添加量は0.０３〜0.２０％の範
囲が好ましい。Ti has the effect of refining the crystal grains and the effect of suppressing grain growth, reduces the hydrogen embrittlement susceptibility of the steel material, and also has the effect of densifying the generated rust, thus improving the corrosion resistance. Let At least 0 to get these effects.
Addition of 01% is required. However, if excessively added, a precipitate with C is formed and a predetermined strength cannot be obtained, so the upper limit of the added amount is set to 0.50%. Particularly, in the present invention, the addition amount is preferably in the range of 0.03 to 0.20%.
【００１５】Ｃｒは、鋼の焼入れ性を向上させると共
に、生成錆を緻密化することによって、鋼の耐食性を向
上させる。このような効果を有効に得るためには、少な
くとも0.１０％の添加が必要である。しかし、過多に添
加するときは、焼入れ焼戻し後の靱性の低下の原因とな
り、更には、腐食形態の局在化（孔食性）を促進し、引
張応力集中による水素脆化割れの原因となるおそれがあ
るので、添加量の上限は5.００％とする。特に、耐食性
及び靱性の観点から、本発明においては、添加量は、1.
５〜3.５％の範囲が好ましい。[0015] Cr improves the hardenability of the steel and also improves the corrosion resistance of the steel by densifying the generated rust. In order to effectively obtain such effects, it is necessary to add at least 0.10%. However, if added too much, it may cause deterioration of toughness after quenching and tempering, and may promote localization of corrosion form (pitting property), causing hydrogen embrittlement cracking due to concentration of tensile stress. Therefore, the upper limit of the added amount is 5.00%. In particular, from the viewpoint of corrosion resistance and toughness, in the present invention, the addition amount is 1.
The range of 5 to 3.5% is preferable.
【００１６】また、本発明によれば、鋼板は、Ａｌ 0.
０５〜2.００％、Ｗ 0.０５〜1.００％、及びＣｏ
0.１０〜5.００％よりなる群から選ばれる少なくとも１
種の元素を含むことができる。According to the present invention, the steel sheet is made of Al 0.
05-2.00%, W 0.05-1.00%, and Co
At least 1 selected from the group consisting of 0.10 to 5.00%
It may include a species of element.
【００１７】Ａｌは、鋼の耐食性を向上させる効果があ
る。この効果を有効に得るには、0.０５％以上の添加が
必要であるが、他方、過多に添加するときは、鋼の加工
性を低下させるので、添加量の上限を2.００％とする。
特に、本発明によれば、添加量は、0.１５〜1.００％の
添加が好ましい。Al has the effect of improving the corrosion resistance of steel. In order to effectively obtain this effect, it is necessary to add 0.05% or more. On the other hand, if too much is added, the workability of the steel will be reduced, so the upper limit of the addition amount is 2.00%. To do.
In particular, according to the present invention, the addition amount is preferably 0.15 to 1.00%.
【００１８】Ｗは、水溶液中で溶解して生じたタングス
テン酸イオンの吸着作用によって、耐孔食性を高める効
果にすぐれる。この効果を有効に得るには、少なくとも
0.０５％の添加が必要である。しかし、1.００％を越え
て過多に添加しても、その効果が飽和するのみであるの
で、上限を1.００％とする。W has an excellent effect of enhancing pitting corrosion resistance due to the adsorption action of tungstate ions generated by dissolution in an aqueous solution. To obtain this effect effectively, at least
Addition of 0.05% is required. However, even if added in excess of 1.00%, the effect is saturated, so the upper limit is made 1.00%.
【００１９】Ｃｏは、固溶強化元素であり、しかも、靱
性を劣化させない特性を有し、更には、耐食性も高める
効果も有している。これらの効果を有効に得るには、0.
１％以上の添加が必要であり、特に、1.０％以上の添加
が好ましい。しかし、Ｃｏは、高価な元素であるので、
添加量の上限を5.００％とする。Co is a solid solution strengthening element, has the property of not degrading toughness, and also has the effect of enhancing corrosion resistance. To obtain these effects effectively, 0.
It is necessary to add 1% or more, and particularly preferably 1.0% or more. However, since Co is an expensive element,
The upper limit of the amount added is 5.00%.
【００２０】更に、本発明によれば、鋼板は、Ｌａ 0.
００１〜0.１００％、Ｃｅ 0.００１〜0.１００％、及
びミッシュメタル 0.００１〜0.１００％よりなる群か
ら選ばれる少なくとも１種の元素を含むことができる。Furthermore, according to the present invention, the steel sheet is La 0.
It may contain at least one element selected from the group consisting of 001 to 0.100%, Ce 0.001 to 0.100%, and misch metal 0.001 to 0.100%.
【００２１】Ｌａ、Ｃｅ又はミッシュメタルは、いずれ
も、鋼が腐食する際に、水溶液中に溶解して、アルカリ
性の水酸化物を生成し、かくして、腐食表面での鉄イオ
ンの溶出に伴う加水分解反応によって、酸性化を中和、
抑制する作用があり、これによって耐食性を向上させ
る。腐食反応による局所的な酸性化は、単に、腐食、即
ち、遅れ破壊の原因となる水素発生反応を促進するのみ
ならず、亀裂発生を促す応力集中のもととなる孔食の生
成を促進するので、これら元素の添加は、平均的な腐食
速度を低減すると共に、耐孔食性の向上の効果も有す
る。La, Ce or misch metal are all dissolved in an aqueous solution when steel is corroded to form an alkaline hydroxide, and thus, the hydration accompanying the elution of iron ions on the corroded surface. Neutralize acidification by decomposition reaction,
It has a suppressing effect, which improves the corrosion resistance. Local acidification by corrosion reaction not only promotes corrosion, that is, hydrogen generation reaction that causes delayed fracture, but also promotes formation of pitting corrosion that causes stress concentration that promotes crack initiation. Therefore, addition of these elements has the effect of reducing the average corrosion rate and improving pitting corrosion resistance.
【００２２】このような耐食性向上の効果を有効に発揮
させるには、上記元素又はミッシュメタルは、いずれ
も、0.００１％以上の添加が必要であるが、しかし、過
多に添加するときは、酸化物系介在物を増加させ、加工
性を低下させると共に、製鋼中、炉壁の溶損を招くおそ
れもあるので、添加量は、いずれの元素又はミッシュメ
タルについても、上限を0.１００％とする。In order to effectively exert such an effect of improving the corrosion resistance, it is necessary to add 0.001% or more of each of the above-mentioned elements or misch metal. However, when they are added excessively, Since oxide inclusions are increased and workability is lowered, there is a risk of melting damage of the furnace wall during steelmaking. Therefore, the addition amount of any element or misch metal has an upper limit of 0.100%. And
【００２３】本発明によれば、鋼板には、Ｃａを添加す
ることができる。Ｃａも、上述したＬａ、Ｃｅ及びミッ
シュメタルと同様の効果を有し、鋼の耐食性の向上に有
効な元素であり、更に、前述したように、Ｃａは、圧延
方向に伸展したＭｎＳを球状のＣａＳに変えることによ
って、オーステナイト結晶粒界の強化の効果も有する。
更には、固溶Ｃａは、電子を放出することにより、鉄原
子間の結合力を高める作用も有する。従って、Ｃａの添
加によって、耐食性の向上と素材の水素脆性感受性の抑
制の相乗効果を実現することができる。According to the present invention, Ca can be added to the steel sheet. Ca also has the same effect as La, Ce, and misch metal described above, and is an element effective for improving the corrosion resistance of steel. Further, as described above, Ca is a spherical form of MnS extended in the rolling direction. By changing to CaS, it also has the effect of strengthening the austenite grain boundaries.
Further, the solid solution Ca also has a function of enhancing the bonding force between iron atoms by releasing electrons. Therefore, by adding Ca, it is possible to realize a synergistic effect of improving the corrosion resistance and suppressing the hydrogen embrittlement sensitivity of the material.
【００２４】このような効果を有効に得るためには、Ｃ
ａは、0.００１％以上を添加すればよいが、しかし、過
多に添加するときは、粗大な介在物を生成して、加工性
を低下させるので、添加量の上限を0.１００％とする。
実用的には、上限は、0.０１０％が好ましい。In order to effectively obtain such an effect, C
Although a may be added in an amount of 0.001% or more, however, when it is added in an excessive amount, coarse inclusions are formed and workability is deteriorated. Therefore, the upper limit of the addition amount is set to 0.100%. To do.
Practically, the upper limit is preferably 0.010%.
【００２５】高強度鋼の遅れ破壊は、現象的には、鋼中
に侵入した拡散性水素が引張応力勾配に従ってある箇所
に局所的に集中し、その箇所において、鋼が水素脆化割
れを起こすことであるとみられる。水素脆化割れは、面
圧説、鉄原子間の凝集力低下説等の種々の機構が提案さ
れているものの、未だ、明確には解明されてないが、水
素の吸収しやすさ、拡散しやすさ、及び鋼自身の水素脆
化感受性の３つの要因が相互に関連した現象であると理
解される。The delayed fracture of high-strength steel is, in theory, that diffusible hydrogen that has penetrated into the steel locally concentrates at a certain location according to the tensile stress gradient, and the steel causes hydrogen embrittlement cracking at that location. It seems to be that. Although various mechanisms of hydrogen embrittlement cracking, such as the theory of surface pressure and the theory of reduction of cohesive force between iron atoms, have been proposed, it has not been clarified yet, but it is easy to absorb hydrogen and diffuse hydrogen. It is understood that the three factors of easiness and hydrogen embrittlement susceptibility of steel itself are interrelated phenomena.
【００２６】従って、水素脆化の対策として、素材側か
らは、（１）水素の侵入経路を遮ること、（２）水素の
鋼中での拡散と引張応力部への集中を抑制すること、
（３）鋼自身の水素脆化性感受性を低くすることの３つ
の対策が有効であると考えられる。従来、水素脆化の対
策としては、（２）及び（３）によるものが多いが、本
発明は（２）及び（３）に加えて、（１）の対策にも着
目したものである。Therefore, as measures against hydrogen embrittlement, from the material side, (1) blocking the invasion route of hydrogen, (2) suppressing the diffusion of hydrogen in steel and the concentration in the tensile stress portion,
(3) Three measures to reduce the hydrogen embrittlement susceptibility of the steel itself are considered to be effective. Conventionally, many countermeasures against hydrogen embrittlement are based on (2) and (3), but the present invention focuses on the countermeasure (1) in addition to (2) and (3).
【００２７】即ち、通常の使用環境における鋼の水素吸
蔵は、鋼が腐食する際、カソード反応により生じた水素
がガス化せずに、鋼中に侵入することに起因するので、
本発明に従って、鋼の耐食性を向上させ、水素野吸蔵を
防止することによって、（１）の対策を実行することが
できる。That is, the hydrogen storage of steel in a normal use environment is caused by the fact that when the steel corrodes, the hydrogen produced by the cathode reaction penetrates into the steel without being gasified.
According to the present invention, the measure (1) can be implemented by improving the corrosion resistance of steel and preventing hydrogen field occlusion.
【００２８】また、耐食性の向上の別の側面としては、
本発明に従って、不均一腐食を抑制することにより、材
料表面における応力集中を避けることができ、もって、
上記（２）の対策とすることができる。一方、（３）の
鋼自身の水素脆化感受性の低下に関しては、粒界偏析元
素含有量を低減すること、或いは結晶粒の微細化等によ
って対応することができる。As another aspect of improving the corrosion resistance,
According to the present invention, by suppressing the non-uniform corrosion, it is possible to avoid stress concentration on the material surface,
The measure of (2) above can be taken. On the other hand, the reduction of the hydrogen embrittlement susceptibility of the steel itself of (3) can be dealt with by reducing the content of the grain boundary segregation element or by refining the crystal grains.
【００２９】本発明は、このように、超高強度鋼の耐遅
れ破壊特性を向上させるための添加元素を鋭意検討した
結果、上述したような所定の元素を用いることによっ
て、引張強度１１８０ＭＰａ以上でありながら、耐遅れ
破壊特性にすぐれる超高強度鋼板を得ることに成功した
ものである。In the present invention, as a result of diligent examination of the additive elements for improving the delayed fracture resistance of the ultra-high strength steel as described above, the tensile strength of 1180 MPa or more can be obtained by using the predetermined elements as described above. In spite of this, it succeeded in obtaining an ultra-high strength steel sheet excellent in delayed fracture resistance.
【００３０】次に、本発明による耐遅れ破壊特性にすぐ
れる超高強度鋼板の製造方法について説明する。Next, a method of manufacturing an ultra high strength steel sheet having excellent delayed fracture resistance according to the present invention will be described.
【００３１】本発明の方法によれば、先ず、上述した化
学成分を有する鋼スラブを加熱温度１１００℃以上、巻
取温度６００℃以下の条件にて、常法に従って、熱間圧
延を行なう。スラブ加熱においては、本発明におけるよ
うな高強度鋼では、熱間圧延時の圧延荷重が高くなりが
ちであるので、圧延温度が低くなりすぎないようにする
ことが好ましく、そこで、鋼スラブの加熱温度を１１０
０℃以上とする。この場合、連続鋳造片をそのまま圧延
する直接圧延や軽加熱や、スラブを冷却した後に、再加
熱を行なう方法等、加熱方法は、特に、限定されるもの
ではない。しかし、加熱温度を１３００℃を越える温度
とすることは、徒に熱エネルギー費用を要するのみであ
り、特に、利点もない。鋼スラブの熱間圧延は、常法に
よって行なえばよく、仕上圧延は８００℃又はそれ以上
の温度で行なえばよい。According to the method of the present invention, first, a steel slab having the above-mentioned chemical composition is hot-rolled according to a conventional method under the conditions of a heating temperature of 1100 ° C. or higher and a winding temperature of 600 ° C. or lower. In the slab heating, in the high-strength steel as in the present invention, the rolling load during hot rolling tends to be high, so it is preferable that the rolling temperature does not become too low. Temperature 110
Set to 0 ° C or higher. In this case, the heating method is not particularly limited, such as direct rolling in which the continuous cast piece is rolled as it is, light heating, or a method in which the slab is cooled and then reheated. However, setting the heating temperature to a temperature higher than 1300 ° C. only requires a great amount of heat energy and has no particular advantage. The hot rolling of the steel slab may be carried out by an ordinary method, and the finish rolling may be carried out at a temperature of 800 ° C. or higher.
【００３２】巻取は、表面のスケールの除去性を考慮
し、６００℃以下の温度で行なう。しかし、余りに低い
ときは、冷間圧延性を低下させるので、巻取温度の下限
は３００℃が好ましい。このようにして得られる熱延鋼
板を常法に従って、酸洗し、研削、ショット・ブラスト
等の手段によって、表面のスケールを除いた後、冷間圧
延し、この後、これを連続焼鈍する。The winding is carried out at a temperature of 600 ° C. or lower in consideration of the surface scale removability. However, if it is too low, the cold rolling property is deteriorated, so the lower limit of the winding temperature is preferably 300 ° C. The hot-rolled steel sheet thus obtained is subjected to a conventional method of pickling, removal of scale on the surface by means such as grinding, shot blasting, etc., followed by cold rolling, followed by continuous annealing.
【００３３】本発明によれば、連続焼鈍によって、加熱
時に、一部又は全体をオーステナイト変態させ、その後
の冷却によって、これらをマルテンサイト変態させる。
本発明によれば、このマルテンサイトの量と合金元素の
量とによって、所望の強度を得ることができる。従っ
て、本発明においては、連続焼鈍において、加熱温度は
８００℃以上、１０００℃以下とする。連続焼鈍後の冷
却処理によってマルテンサイト、焼戻しマルテンサイト
又はベイナイト等の所要の低温変態組織を得るために、
加熱時にオーステナイトを析出させることが必要であ
り、そのために加熱温度をＡc1点以上とする。しかし、
１０００℃を越える温度としても、特に、利点なく、エ
ネルギー費用が嵩むのみである。According to the present invention, a part or the whole of the material undergoes austenite transformation during heating by continuous annealing, and then martensite transformation occurs by cooling.
According to the present invention, a desired strength can be obtained by the amount of martensite and the amount of alloying element. Therefore, in the present invention, in the continuous annealing, the heating temperature is 800 ° C or higher and 1000 ° C or lower. In order to obtain the required low-temperature transformation structure such as martensite, tempered martensite or bainite by the cooling treatment after continuous annealing,
It is necessary to precipitate austenite during heating, and therefore the heating temperature is set to Ac 1 point or higher. But,
Even if the temperature exceeds 1000 ° C., there is no particular advantage and only the energy cost increases.
【００３４】このような連続焼鈍の後、３０℃／秒以下
の冷却速度にて、８００〜６５０℃の範囲の温度まで徐
冷（一次冷却）し、次いで、この温度から急冷（二次冷
却）する。上記徐冷温度が３０℃／秒よりも早いとき
は、フェライトが生成し難く、所定の強度を安定して得
ることができない。また、上記急冷時の冷却速度は、マ
ルテンサイト等の低温変態を起こさせるために、７０℃
／秒以上が必要であり、このような冷却速度にて４００
℃以下まで冷却して、マルテンサイト等の変態を起こさ
せる。急冷開始温度が６５０℃よりも低いときは、急冷
開始までにオーステナイトからフェライトの変態が進
み、体積率にて４０％以上のマルテンサイト等の所要の
低温変態組織を得ることが困難である。他方、急冷開始
温度が８００℃よりも高いときは、得られる鋼板の形状
性が低下するので好ましくない。急冷速度は、特に限定
されるものではないが、通常、工業的には水焼入れによ
る冷却速度（１０００〜２０００℃／秒）が上限であ
る。After such continuous annealing, it is gradually cooled (primary cooling) to a temperature in the range of 800 to 650 ° C. at a cooling rate of 30 ° C./second or less, and then rapidly cooled (secondary cooling) from this temperature. To do. When the slow cooling temperature is higher than 30 ° C./sec, ferrite is hard to be generated and a predetermined strength cannot be stably obtained. The cooling rate during the rapid cooling is 70 ° C. in order to cause low-temperature transformation of martensite and the like.
/ Sec or more is required, and at such a cooling rate 400
Cooling to below ℃, transformation such as martensite occurs. When the quenching start temperature is lower than 650 ° C., transformation of austenite to ferrite progresses by the start of quenching, and it is difficult to obtain a required low temperature transformation structure such as martensite having a volume ratio of 40% or more. On the other hand, when the quenching start temperature is higher than 800 ° C., the formability of the obtained steel sheet deteriorates, which is not preferable. The quenching rate is not particularly limited, but the cooling rate by water quenching (1000 to 2000 ° C./sec) is industrially the upper limit.
【００３５】本発明による鋼板は、マルテンサイト、焼
戻しマルテンサイト又はベイナイト組織のいずれか１種
以上の低温変態組織を体積率にて４０％以上を有し、す
べての組織が低温変態生成物であってもよい。低温変態
組織が４０％よりも少ないときは、所望の強度を得るた
めに必要な合金元素の量が増し、製造費用が高くなる。The steel sheet according to the present invention has a low temperature transformation structure of at least one of martensite, tempered martensite and bainite structure in a volume ratio of 40% or more, and all the structures are low temperature transformation products. May be. When the low temperature transformation structure is less than 40%, the amount of alloying elements required to obtain the desired strength increases, and the manufacturing cost increases.
【００３６】次いで、焼入れた組織がマルテンサイトで
あるときは、その加工性を向上し、例えば、パイプ等に
支障なく容易に加工することができるように、上述した
ような連続焼鈍後に再加熱し、又は連続焼鈍からそのま
ま、１５０〜４００℃の範囲の温度にて焼戻し処理を行
なう。焼戻し処理を４００℃以上の温度で行なうこと
は、再加熱のために製造費用を高めるのみならず、特
に、有用な効果を得ることができない。Next, when the quenched structure is martensite, it is reheated after continuous annealing as described above so that its workability is improved and, for example, pipes and the like can be easily processed without trouble. Alternatively, the tempering treatment is performed at a temperature in the range of 150 to 400 ° C. as it is from the continuous annealing. Performing the tempering treatment at a temperature of 400 ° C. or higher not only increases the manufacturing cost due to reheating, but also cannot obtain a particularly useful effect.
【００３７】[0037]
【実施例】以下に実施例を挙げて本発明を説明するが、
本発明はこれら実施例により何ら限定されるものではな
い。The present invention will be described below with reference to examples.
The present invention is not limited to these examples.
【００３８】実施例１ 表１から３に示す鋼を１２３０℃に加熱して、仕上温度
８００℃にて板厚3.０mmに熱間圧延し、４８０℃で巻き
取った。これを酸洗した後、板厚1.８mmまで冷間圧延し
た。その後、８５０℃で２分間保持し、７５０℃まで強
制空冷し、この温度から水焼入れを行ない、焼戻し処理
を行なった。焼戻し条件は、１８０〜４００℃の温度で
加熱時間１２分として、引張強さが１１８０ＭＰａ以上
の鋼板を得た。表中、低温変態生成物の欄において、Ｍ
はマルテンサイト、Ｍｔは焼戻しマルテンサイト、Ｂは
ベイナイト、Ｐはパーライトを示す。Example 1 The steels shown in Tables 1 to 3 were heated to 1230 ° C., hot-rolled at a finishing temperature of 800 ° C. to a plate thickness of 3.0 mm, and wound at 480 ° C. This was pickled and cold-rolled to a plate thickness of 1.8 mm. Then, the temperature was maintained at 850 ° C. for 2 minutes, forced air cooling to 750 ° C., water quenching was performed from this temperature, and tempering treatment was performed. The tempering conditions were a temperature of 180 to 400 ° C. and a heating time of 12 minutes to obtain a steel sheet having a tensile strength of 1180 MPa or more. In the table, low temperature transformation products, M
Indicates martensite, Mt indicates tempered martensite, B indicates bainite, and P indicates pearlite.
【００３９】[0039]
【表１】 [Table 1]
【００４０】[0040]
【表２】 [Table 2]
【００４１】[0041]
【表３】 [Table 3]
【００４２】このようにして得られた鋼板について、次
のようにして、耐遅れ破壊特性を調べた。即ち、鋼板を
機械加工により２０mm幅、長さ１００mmに切り出し、こ
の試料を板長手方向中央部で曲率半径１０mmのＵ字曲げ
加工し、板端部近傍でボルト締めを行なって、一定量の
曲げ応力を付与した試験片とした。ここに、ボルトと試
験片との間のガルバニック腐食を避けるため、ボルト
は、テフロン製のチューブで被覆し、絶縁した。また、
試験片としては、すべて裸材を用いた。The delayed fracture resistance of the thus obtained steel sheet was examined as follows. That is, a steel plate is cut by machining to a width of 20 mm and a length of 100 mm, and this sample is bent in a U shape with a radius of curvature of 10 mm at the central portion in the longitudinal direction of the plate and bolted near the end of the plate to bend a certain amount. The test piece was given a stress. Here, in order to avoid galvanic corrosion between the bolt and the test piece, the bolt was covered with a Teflon tube and insulated. Also,
All the bare materials were used as the test pieces.
【００４３】試験環境は、塩水噴霧試験（ＪＩＳ Ｚ
２３７１）を１２時間行なった後、これを１２時間放置
することを１サイクルとするサイクル試験と、0.１Ｎ塩
酸浸漬試験（３０℃）との２種とし、上記Ｕ字曲げ試験
片の割れサイクル数及び割れ時間を測定することによっ
て、鋼の耐遅れ破壊特性を評価した。結果を図１に示す
ように、本発明による鋼では、いずれもの試験において
も、割れ発生が起こるまでの時間が著しく長なってお
り、本発明鋼が耐遅れ破壊特性にすぐれることが理解さ
れる。The test environment is a salt spray test (JIS Z
2371) for 12 hours and then left to stand for 12 hours as one cycle and a 0.1N hydrochloric acid immersion test (30 ° C.) as two types, and the crack cycle of the U-shaped bending test piece described above. The delayed fracture resistance properties of the steel were evaluated by measuring the number and cracking time. As shown in the results in FIG. 1, it is understood that the steel according to the present invention has a significantly long time until crack initiation in any of the tests, and the steel according to the present invention has excellent delayed fracture resistance. It
【００４４】実施例２ 表４に示す化学成分を有する鋼を用いて表４及び表５に
示す条件にて高強度鋼板を製造した。得られた鋼板の強
度及び耐遅れ破壊特性を表５に示す。耐遅れ破壊特性の
評価は実施例１と同様にして行なった。Example 2 High-strength steel sheets were manufactured under the conditions shown in Tables 4 and 5 using steels having the chemical compositions shown in Table 4. Table 5 shows the strength and delayed fracture resistance of the obtained steel sheet. The delayed fracture resistance was evaluated in the same manner as in Example 1.
【００４５】[0045]
【表４】 [Table 4]
【００４６】[0046]
【表５】 [Table 5]
【００４７】[0047]
【発明の効果】以上のように、本発明による超高強度鋼
板は、１１８０ＭＰａ以上の引張強度を有しながら、同
時に、遅れ破壊に対してすぐれた耐性を有しており、か
かる鋼板は、例えば、自動車のバンパーやドアの補強部
材の軽量化のために好適に用いることができる。As described above, the ultrahigh strength steel sheet according to the present invention has a tensile strength of 1180 MPa or more, and at the same time, has excellent resistance to delayed fracture. It can be suitably used for reducing the weight of automobile bumpers and door reinforcing members.
【図１】は、本発明による高強度鋼板と比較例としての
鋼板について、それぞれの耐遅れ破壊特性を示すグラフ
である。図中、添数字は、表中の鋼種番号を示す。FIG. 1 is a graph showing delayed fracture resistance characteristics of a high-strength steel sheet according to the present invention and a steel sheet as a comparative example. In the figure, the subscripts indicate the steel type numbers in the table.
───────────────────────────────────────────────────── 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 38/58 Ｃ２２Ｃ 38/58 (72)発明者 中島 悟博 兵庫県加古川市金沢町１番地 株式会社神 戸製鋼所加古川製鉄所内 (72)発明者 田中 福輝 兵庫県加古川市金沢町１番地 株式会社神 戸製鋼所加古川製鉄所内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical indication location C22C 38/58 C22C 38/58 (72) Inventor Satoru Nakajima 1 Kanazawa-machi, Kakogawa-shi, Hyogo Stock Company Kado Steel Works Kakogawa Steel Works (72) Inventor Fukuteru Tanaka 1 Kanazawa-machi, Kakogawa City, Hyogo Prefecture Kadodo Steel Works Kakogawa Steel Works
Claims (20)
純物よりなり、マルテンサイト、焼戻しマルテンサイト
又はベイナイト組織のいずれか１種以上を体積率にて４
０％以上含み、強度が１１８０ＭＰａ以上である耐遅れ
破壊特性にすぐれる超高強度鋼板。1. C wt.% 0.08 to 0.30%, Si less than 1.0%, Mn 1.5 to 3.0%, S 0.010% or less, and P 0.03 to 0.3% by weight. 15%, Cu 0.10 to 1.00%, and Ni 0.10 to 4.00%, balance iron and unavoidable impurities, and one or more of martensite, tempered martensite, and bainite structure. Volume ratio of 4
An ultra high strength steel sheet containing 0% or more and having a strength of 1180 MPa or more and excellent in delayed fracture resistance.
に、 Ｔｉ 0.０１〜0.５０％、及びＣｒ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素を含む超
高強度鋼板。2. The ultra high strength steel sheet according to claim 1, further comprising Ti 0.01 to 0.50% and Cr 0.10 to 5.00%.
An ultra-high strength steel sheet containing at least one element selected from the group consisting of:
に、 Ａｌ 0.０５〜2.００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素を含む超
高強度鋼板。3. The ultra-high strength steel sheet according to claim 1, further comprising Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%.
An ultra-high strength steel sheet containing at least one element selected from the group consisting of:
に、 Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素を含む超高強度鋼板。4. The ultra-high strength steel sheet according to claim 1, further comprising La 0.001 to 0.100%, Ce 0.001 to 0.100%, and Misch metal 0.1.
Ultra high strength steel sheet containing at least one element selected from the group consisting of 001 to 0.100%.
に、(a) Ｔｉ 0.０１〜0.５０％、及びＣｒ 0.１０〜
5.００％よりなる群から選ばれる少なくとも１種の元素
と、(b) Ａｌ 0.０５〜2.００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素とを含む
超高強度鋼板。5. The ultrahigh strength steel sheet according to claim 1, further comprising (a) Ti 0.01 to 0.50% and Cr 0.10.
At least one element selected from the group consisting of 5.00%, and (b) Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%.
An ultra high strength steel sheet containing at least one element selected from the group consisting of:
に、(a) Ｔｉ 0.０１〜0.５０％、及びＣｒ 0.１０〜
5.００％よりなる群から選ばれる少なくとも１種の元素
と、(b) Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素とを含む超高強度鋼板。6. The ultrahigh strength steel sheet according to claim 1, further comprising (a) Ti 0.01 to 0.50% and Cr 0.10.
At least one element selected from the group consisting of 5.00%, and (b) La 0.001 to 0.100%, Ce 0.001 to 0.100%, and misch metal 0.10.
Ultra high strength steel sheet containing at least one element selected from the group consisting of 001 to 0.100%.
に、(a) Ａｌ 0.０５〜2.００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素と、(b)
Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素とを含む超高強度鋼板。7. The ultra-high strength steel plate according to claim 1, further comprising (a) Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5%. 0.00%
At least one element selected from the group consisting of (b)
La 0.001 to 0.10%, Ce 0.001 to 0.100%, and misch metal 0.10.
Ultra high strength steel sheet containing at least one element selected from the group consisting of 001 to 0.100%.
に、(a) Ｔｉ 0.０１〜0.５０％、及びＣｒ 0.１０〜
5.００％よりなる群から選ばれる少なくとも１種の元素
と、(b) Ａｌ 0.０５〜2.００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素と、(c)
Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素とを含む超高強度鋼板。8. The ultra-high strength steel sheet according to claim 1, further comprising (a) Ti 0.01 to 0.50% and Cr 0.10.
At least one element selected from the group consisting of 5.00%, and (b) Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%.
At least one element selected from the group consisting of (c)
La 0.001 to 0.10%, Ce 0.001 to 0.100%, and misch metal 0.10.
Ultra high strength steel sheet containing at least one element selected from the group consisting of 001 to 0.100%.
項１乃至８いずれかに記載の超高強度鋼板。9. The ultra high strength steel sheet according to claim 1, wherein the C content is in the range of 0.12 to 0.20%.
度鋼板であって、更に、Ｃａを0.００１〜0.１％の範囲
で添加してなる超高強度鋼板。10. The ultrahigh-strength steel sheet according to claim 1, further comprising Ca in an amount of 0.001 to 0.1%.
を含み、残部鉄及び不可避的不純物よりなる鋼スラブを
１１００℃以上の温度に加熱し、６００℃以下の温度で
巻取る熱間圧延を行なった後、酸洗し、スケールを除
き、冷間圧延を行ない、次いで、連続焼鈍を行なうに際
して、８００℃以上、１０００℃以下の範囲の温度にて
均熱した後、３０℃／秒以下の冷却速度にて、８００〜
６５０℃の範囲の温度まで徐冷し、次いで、この温度か
ら７０℃／秒以上の冷却速度にて４００℃以下の温度ま
で冷却し、この後、再加熱するか、又はそのまま、１５
０〜４００℃の範囲の温度で１〜２０分間加熱する焼戻
し処理を行なうことを特徴とするマルテンサイト、焼戻
しマルテンサイト又はベイナイト組織のいずれか１種以
上を体積率にて４０％以上含み、強度１１８０ＭＰａ以
上である耐遅れ破壊特性にすぐれる超高強度鋼板の製造
方法。11. C. 0.08 to 0.30% by weight, Si less than 1.0%, Mn 1.5 to 3.0%, S 0.010% or less, P 0.03 to 0. 15%, Cu 0.10 to 1.00%, and Ni 0.10 to 4.00%
A steel slab containing iron and the balance iron and unavoidable impurities is heated to a temperature of 1100 ° C. or higher, and hot rolling is performed at a temperature of 600 ° C. or lower, followed by pickling, removing scale, and cold rolling. Then, when performing continuous annealing, after soaking at a temperature in the range of 800 ° C. or more and 1000 ° C. or less, at a cooling rate of 30 ° C./sec or less, 800 to
Gradually cool to a temperature in the range of 650 ° C., then cool from this temperature to a temperature of 400 ° C. or less at a cooling rate of 70 ° C./sec or more, and then reheat or leave it at 15 ° C.
Martensite, which is characterized by performing a tempering treatment by heating at a temperature in the range of 0 to 400 ° C. for 1 to 20 minutes, contains 40% or more by volume of any one or more of martensite, tempered martensite, and bainite structure, A method for producing an ultra high strength steel sheet having excellent delayed fracture resistance of 1180 MPa or more.
よりなる群から選ばれる少なくとも１種の元素を含む請
求項１１記載の超高強度鋼板の製造方法。12. The steel slab further comprises Ti 0.01 to 0.50% and Cr 0.10 to 5.00%.
The method for producing an ultra-high strength steel sheet according to claim 11, comprising at least one element selected from the group consisting of:
よりなる群から選ばれる少なくとも１種の元素を含む請
求項１１記載の超高強度鋼板の製造方法。13. The steel slab further comprises Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%.
The method for producing an ultra-high strength steel sheet according to claim 11, comprising at least one element selected from the group consisting of:
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素を含む請求項１１記載の超高強度鋼板。14. The steel slab further comprises La 0.001 to 0.100%, Ce 0.001 to 0.100%, and Misch metal 0.1.
The ultrahigh-strength steel sheet according to claim 11, which contains at least one element selected from the group consisting of 001 to 0.100%.
５０％、及びＣｒ 0.１０〜5.００％よりなる群から選
ばれる少なくとも１種の元素と、(b) Ａｌ 0.０５〜2.
００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素とを含む
請求項１１記載の超高強度鋼板の製造方法。15. The steel slab further comprises (a) Ti 0.01 to 0.
At least one element selected from the group consisting of 50% and Cr 0.10 to 5.00%, and (b) Al 0.05 to 2.
00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%
The method for producing an ultrahigh-strength steel sheet according to claim 11, comprising at least one element selected from the group consisting of:
５０％、及びＣｒ 0.１０〜5.００％よりなる群から選
ばれる少なくとも１種の元素と、(b) Ｌａ 0.００１〜
0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素を含む請求項１１記載の超高強度鋼板の製造
方法。16. The steel slab further comprises (a) Ti 0.01 to 0.
50% and at least one element selected from the group consisting of Cr 0.10 to 5.00%, and (b) La 0.001
0.10%, Ce 0.001-0.10%, and misch metal 0.10.
The method for producing an ultra-high strength steel sheet according to claim 11, comprising at least one element selected from the group consisting of 001 to 0.100%.
よりなる群から選ばれる少なくとも１種の元素と、 Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素とを含む請求項１１記載の超高強度鋼の製造
方法板。17. The steel slab further comprises Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.10 to 5.00%.
At least one element selected from the group consisting of La 0.001 to 0.100%, Ce 0.001 to 0.100%, and misch metal 0.1.
The method for producing ultra high strength steel according to claim 11, further comprising at least one element selected from the group consisting of 001 to 0.100%.
５０％、及びＣｒ 0.１０〜5.００％よりなる群から選
ばれる少なくとも１種の元素と、 Ａｌ 0.０５〜2.００％、 Ｗ 0.０５〜1.００％、及びＣｏ 0.１０〜5.００％
よりなる群から選ばれる少なくとも１種の元素と、 Ｌａ 0.００１〜0.１００％、 Ｃｅ 0.００１〜0.１００％、及びミッシュメタル 0.
００１〜0.１００％よりなる群から選ばれる少なくとも
１種の元素とを含む請求項１１記載の超高強度鋼板の製
造方法。18. The steel slab further comprises (a) Ti 0.01 to 0.
50%, and at least one element selected from the group consisting of Cr 0.010 to 5.00%, Al 0.05 to 2.00%, W 0.05 to 1.00%, and Co 0.005. 10-5.00%
At least one element selected from the group consisting of La 0.001 to 0.100%, Ce 0.001 to 0.100%, and misch metal 0.1.
The method for producing an ultra-high strength steel sheet according to claim 11, comprising at least one element selected from the group consisting of 001 to 0.100%.
０％である請求項１１乃至１８いずれかに記載の超高強
度鋼板の製造方法。19. A steel slab having a C content of 0.12 to 0.2.
It is 0%, The manufacturing method of the ultra high strength steel plate in any one of Claims 11-18.
１％添加してなる請求項１１乃至１９いずれかに記載の
超高強度鋼板の製造方法。20. In a steel slab, Ca is 0.001 to 0.
The method for producing an ultra-high strength steel sheet according to any one of claims 11 to 19, wherein 1% is added.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12138795A JP3254107B2 (en) | 1995-05-19 | 1995-05-19 | Ultra-high-strength steel sheet excellent in delayed fracture resistance and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12138795A JP3254107B2 (en) | 1995-05-19 | 1995-05-19 | Ultra-high-strength steel sheet excellent in delayed fracture resistance and method of manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08311601A true JPH08311601A (en) | 1996-11-26 |
| JP3254107B2 JP3254107B2 (en) | 2002-02-04 |
Family
ID=14809946
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12138795A Expired - Fee Related JP3254107B2 (en) | 1995-05-19 | 1995-05-19 | Ultra-high-strength steel sheet excellent in delayed fracture resistance and method of manufacturing the same |
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| Country | Link |
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| JP (1) | JP3254107B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11193418A (en) * | 1997-12-29 | 1999-07-21 | Kobe Steel Ltd | Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic |
| JP2005187863A (en) * | 2003-12-25 | 2005-07-14 | Kobe Steel Ltd | High strength cold rolled steel sheet having excellent coating film adhesion |
| WO2010055609A1 (en) | 2008-11-11 | 2010-05-20 | 新日本製鐵株式会社 | Thick steel sheet having high strength and method for producing same |
| EP2455499A1 (en) * | 2009-07-08 | 2012-05-23 | Toyo Kohan Co., Ltd. | Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet |
| WO2013018723A1 (en) | 2011-07-29 | 2013-02-07 | 新日鐵住金株式会社 | High-strength zinc-plated steel sheet and high-strength steel sheet having superior moldability, and method for producing each |
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1995
- 1995-05-19 JP JP12138795A patent/JP3254107B2/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11193418A (en) * | 1997-12-29 | 1999-07-21 | Kobe Steel Ltd | Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic |
| JP2005187863A (en) * | 2003-12-25 | 2005-07-14 | Kobe Steel Ltd | High strength cold rolled steel sheet having excellent coating film adhesion |
| WO2010055609A1 (en) | 2008-11-11 | 2010-05-20 | 新日本製鐵株式会社 | Thick steel sheet having high strength and method for producing same |
| US8500924B2 (en) | 2008-11-11 | 2013-08-06 | Nippon Steel & Sumitomo Metal Corporation | High-strength steel plate and producing method therefor |
| EP2455499A1 (en) * | 2009-07-08 | 2012-05-23 | Toyo Kohan Co., Ltd. | Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet |
| CN102471821A (en) * | 2009-07-08 | 2012-05-23 | 东洋钢钣株式会社 | Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet |
| US20120234438A1 (en) * | 2009-07-08 | 2012-09-20 | Nakayama Steel Works, Ltd. | Process for Production of Cold-Rolled Steel Sheet Having Excellent Press Moldability, and Cold-Rolled Steel Sheet |
| EP2455499A4 (en) * | 2009-07-08 | 2016-02-10 | Toyo Kohan Co Ltd | Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet |
| WO2013018723A1 (en) | 2011-07-29 | 2013-02-07 | 新日鐵住金株式会社 | High-strength zinc-plated steel sheet and high-strength steel sheet having superior moldability, and method for producing each |
| KR20140026625A (en) | 2011-07-29 | 2014-03-05 | 신닛테츠스미킨 카부시키카이샤 | High-strength zinc-plated steel sheet and high-strength steel sheet having superior moldability and method for producing each |
| US9694561B2 (en) | 2011-07-29 | 2017-07-04 | Nippon Steel & Sumitomo Metal Corporation | High strength steel sheet and high strength galvanized steel sheet excellent in shapeability and methods of production of same |
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