JPH064903B2 - Steel plate with excellent brittle crack propagation arresting property and its manufacturing method - Google Patents
Steel plate with excellent brittle crack propagation arresting property and its manufacturing methodInfo
- Publication number
- JPH064903B2 JPH064903B2 JP60074786A JP7478685A JPH064903B2 JP H064903 B2 JPH064903 B2 JP H064903B2 JP 60074786 A JP60074786 A JP 60074786A JP 7478685 A JP7478685 A JP 7478685A JP H064903 B2 JPH064903 B2 JP H064903B2
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- thickness
- slab
- ferrite
- steel
- Prior art date
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Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は脆性破壊が生じた場合の脆性き裂伝播停止特性
が優れた厚鋼板及びその製造法に関するものである。Description: TECHNICAL FIELD The present invention relates to a thick steel plate having excellent brittle crack propagation arresting characteristics when brittle fracture occurs, and a method for manufacturing the same.
（従来の技術及び発明が解決しようとする問題点） 脆性破壊が生じた場合の脆性き裂伝播停止特性におよぼ
す冶金学的な要因としては結晶粒の微細化が脆性き裂伝
播停止特性を向上させることは良く知られている。一般
的な厚鋼板の製造工程において結晶粒径を微細化する手
段としては従来、低温加熱，低温域圧延および圧延終了
後の冷却速度を適度に制御する方法などが行なわれてき
た。(Problems to be solved by conventional techniques and inventions) As a metallurgical factor that affects the brittle crack propagation arresting characteristics when brittle fracture occurs, grain refinement improves brittle crack propagation arresting characteristics. It is well known to let people do it. As means for refining the crystal grain size in a general manufacturing process of thick steel plates, low temperature heating, low temperature region rolling, and a method of appropriately controlling the cooling rate after the rolling have been performed.
しかし、加熱温度は加熱時に十分オーステナイト化をは
かる必要からAc3以上の温度を保つ必要があり低温加熱
による細粒化には限界がある。However, the heating temperature is required to be sufficiently austenitized during heating, so that it is necessary to maintain the temperature of Ac 3 or higher, and there is a limit to fine graining by low temperature heating.
過度の二相域圧延は材質を劣化させるため圧延温度の低
下にも限界がある。また厚鋼板の圧延では圧延反力の制
限から圧下率を大きくとれず圧延による細粒化にも限界
がある。Since excessive two-phase region rolling deteriorates the material, there is a limit to the reduction of rolling temperature. Further, in the rolling of thick steel plates, the rolling reduction cannot be made large due to the limitation of the rolling reaction force, and there is a limit to the fine graining by rolling.
また圧延終了後の冷却速度は大きいほど変態後のフェラ
イト結晶粒径は微細となるが、過大な場合はベイナイ
ト，マリテンサイト等の低温変態生成組織の占める割合
が増えて材質は劣化するためある程度以上の冷却速度で
冷却することはできず制御冷却による細粒化にも限界が
ある。Also, the larger the cooling rate after rolling is, the finer the ferrite crystal grain size after transformation will be, but if it is too large, the proportion of low-temperature transformation-forming structures such as bainite and martensite will increase and the material will deteriorate to some extent. It is not possible to cool at the above cooling rate, and there is a limit to the atomization by controlled cooling.
以上述べたように、従来の厚鋼板の製造技術ではその結
晶粒の微細化に限界があるため脆性き裂伝播停止特性に
も限界がある。また厚鋼板の結晶粒を微細化する特殊な
方法としては特公昭４９−7293号公報記載のように冷却
・加熱を繰り返すことにより最終組織にいたるまでの変
態の回数を多くする方法がある。しかし単なる温度制御
により変態の回数を増しても結晶粒の微細化には限界が
あり脆性き裂伝播停止特性の向上にも限界があるばかり
でなく、このような工程は経済的に大きな負担となる。As described above, in the conventional thick steel plate manufacturing technology, there is a limit to the refinement of the crystal grains, and thus there is a limit to the brittle crack propagation arresting property. Further, as a special method of refining the crystal grains of the thick steel plate, there is a method of increasing the number of transformations up to the final structure by repeating cooling and heating as described in JP-B-49-7293. However, even if the number of transformations is increased simply by controlling the temperature, there is a limit to the refinement of crystal grains, and there is also a limit to the improvement of the brittle crack propagation arresting property, and such a process imposes a large economical burden. Become.
（問題点を解決するための手段） 本発明は上記のような従来法の欠点を有利に排除しうる
脆性き裂伝播停止特性の優れた厚鋼板およびその製造方
法でありその要旨とするところは次の通りである。(Means for Solving the Problems) The present invention is a thick steel sheet having excellent brittle crack propagation arresting characteristics that can advantageously eliminate the drawbacks of the conventional methods as described above, and a manufacturing method thereof. It is as follows.
重量％で、 Ｃ 0.01〜0.30％、 Mn 2.0％以下、 Si 0.5％以下、 Al 0.1％以下、 Ｎ 0.001〜0.01％、 又は更に、Ｂ 0.0005〜0.0015％、 Cu 0.9％以下、 Ni 1.0％以下、 Cr 0.5％以下、 Mo 0.5％以下の１種または２種以上を含み又は更に、N
b 0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなり、厚鋼板両表面より板厚中
心方向に板厚の１／８以上の距離にわたって５μｍ以下
（Nb、Tiの一種以上を含むときは３μｍ以下）の結晶粒
径を有するフェライト結晶粒が面積率にして５０％以上
存在することを特徴とする脆性き裂伝播停止特性の優れ
た厚鋼板。% By weight, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, or further B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, One or more of Cr 0.5% or less and Mo 0.5% or less, or further N
b 0.05% or less, Ti 0.1% or less, 1 type or 2 types or more, and the balance is Fe
And ferrite having an inevitable impurity and having a crystal grain size of 5 μm or less (3 μm or less when including one or more of Nb and Ti) over a distance of ⅛ or more of the plate thickness from both surfaces of the thick steel plate toward the center of the plate thickness. A thick steel sheet excellent in brittle crack propagation arresting characteristics, characterized in that crystal grains are present in an area ratio of 50% or more.
重量％で、 Ｃ0.01〜0.30％， Mn 2.0％以下， Si 0.5％以下， Al 0.1％以下， Ｎ 0.001〜0.01％ 又は更に Ｂ 0.0005〜0.0015％ Cu 0.9％以下， Ni 1.0％以下， Cr 0.5％以下， Mo 0.5％以下， の１種または２種以下を含み、 残部がFeおよび不可避的不純物よりなる連続鋳造鋳片を
Ac3以上に加熱した後、 あるいは連続鋳造ままで、該鋳片の両表面より鋳片厚中
心方向に鋳片厚の1/8以上がAr3以下となるまで鋳片厚平
均冷却速度が２℃／ｓ以上となるように冷却し、引き続
き該鋳片厚方向に温度差をつけたまま鋳片両表面より鋳
片厚中心方向に鋳片厚の1/8以上がフェライト１相また
はフェライト−オーステナイト２相状態で圧延を開始
し、かつ該圧延中または圧延終了後鋳片厚全域にわたり
Ac3を越える温度まで復熱させることを特徴とする脆性
き裂伝播停止特性の優れた厚鋼板の製造法である。% By weight, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01% or even B 0.0005 to 0.0015% Cu 0.9% or less, Ni 1.0% or less, Cr 0.5 % Or less, Mo 0.5% or less, one or two or less, and the balance is Fe and unavoidable impurities.
After being heated to Ac 3 or more, or as it is in continuous casting, the slab thickness average cooling rate is 2 until 1/8 or more of the slab thickness becomes Ar 3 or less from both surfaces of the slab toward the center of the slab thickness. C./s or more, and continuously with a temperature difference in the thickness direction of the slab, 1/8 or more of the slab thickness from both surfaces of the slab toward the center of the slab thickness is ferrite 1 phase or ferrite- Starting the rolling in the austenite two-phase state, and during the rolling or after the rolling, over the entire thickness of the cast piece.
This is a method for manufacturing thick steel sheets with excellent brittle crack propagation arresting characteristics, which is characterized by reheating to a temperature exceeding Ac 3 .
以下本発明について詳細に説明する。The present invention will be described in detail below.
先づ本発明厚鋼板の成分限定理由について説明する。First, the reasons for limiting the components of the thick steel plate of the present invention will be described.
Ｃは鋼材を強化するために不可欠な元素であって、0.01
％未満では所要の強度が得られにくく、また0.30％を越
えると溶接部の靱性が損われるため0.01％以上0.30％以
下に限定した。C is an essential element for strengthening steel, and 0.01
If it is less than 0.1%, it is difficult to obtain the required strength, and if it exceeds 0.30%, the toughness of the welded portion is impaired, so the content is limited to 0.01% or more and 0.30% or less.
Siは脱酸を促進しかつ強度をあげることで効果的な元素
であるので0.01％以上添加するが、添加しすぎると溶接
性を劣化させるので0.5％以下にとどめる。Si is an element effective in promoting deoxidation and increasing strength, so 0.01% or more is added, but if added too much, weldability deteriorates, so 0.5% or less is kept.
Mn低温靱性を向上させる元素として有効であるので2.0
％以上添加すると溶接割れ性を促進させるおそれがある
ため、2.0％以下にとどめる。Mn is an effective element to improve low temperature toughness, so 2.0
%, The weld crackability may be promoted, so the content is limited to 2.0% or less.
Alは脱酸剤として有効であり結晶粒の微細化にも有効で
あるが過量のAlは材質にとって有害な介在物を生成する
ので上限を0.1％とした。Al is effective as a deoxidizer and is also effective for refining crystal grains, but an excessive amount of Al forms inclusions harmful to the material, so the upper limit was made 0.1%.
ＮはAlと共に窒化物を生成し結晶粒の微細化に有効であ
るが過量のＮは溶接部の靱性が損われるので0.001％以
上0.01％以下に限定した。N forms a nitride together with Al and is effective for refining the crystal grains, but an excessive amount of N impairs the toughness of the welded portion, so the N content is limited to 0.001% or more and 0.01% or less.
Nb,Tiはいずれも微量の添加で結晶粒の細粒化に有効で
あるが過度に添加すると溶接部靱性が劣化するのでNbは
0.05％以下，Tiは0.1％以下とした。Both Nb and Ti are effective for grain refining with a small amount of addition, but if added excessively, the toughness of the weld will deteriorate, so Nb is
0.05% or less and Ti 0.1% or less.
なお析出硬化による強化に有効である元素Ｖを0.1％以
下を本発明鋼に添加しても良い。In addition, 0.1% or less of the element V effective for strengthening by precipitation hardening may be added to the steel of the present invention.
Cu,Cr,Mo,Niはいずれも焼き入れ性を向上させる元素と
して知られており本発明鋼に添加した場合、鋼の強度を
上昇させることができるが過度の添加は低温変態生成物
を生じさせフェライト面積率を減少させることになるの
で、Cuは0.9％以下、Crは0.5％以下、Moは0.5％以下，N
iは1.0％以下とした。Cu, Cr, Mo, Ni are all known as elements that improve hardenability, and when added to the steel of the present invention, the strength of the steel can be increased, but excessive addition causes low-temperature transformation products. As a result, the ferrite area ratio is reduced, so that Cu is 0.9% or less, Cr is 0.5% or less, Mo is 0.5% or less, N
i was set to 1.0% or less.
次に本発明の根幹をなす技術思想について述べる。Next, the technical idea that forms the basis of the present invention will be described.
脆性き裂が伝播するためには伝播を続ける主き裂の前面
に先行き裂が形成されその先行き裂が主き裂に連結する
ことが必要である。この連結は結晶粒界におけるテアリ
ングによって生ずるが、テアリングは本質的に延性破壊
であるので相当量のエネルギーを吸収し、主き裂の減速
に寄与する。結晶粒を微細化することはこのテアリング
による主き裂の減速効果の向上に結びつくものである。In order for a brittle crack to propagate, it is necessary that a forward crack be formed in front of the main crack that continues to propagate and that the forward crack be connected to the main crack. Although this connection is caused by tearing at the grain boundaries, tearing absorbs a considerable amount of energy as it is essentially ductile fracture and contributes to the slowing of the main crack. The refinement of crystal grains leads to an improvement in the moderating effect of the main crack due to this tearing.
このように、結晶粒の微細化は脆性き裂伝播停止特性に
きわめて有効であるが現在の通常の厚鋼板の製造法では
その微細化には限界がある。また特公昭49-7293号公報
記載のような水冷後の再加熱工程を含むような特殊な方
法で板厚方向全厚にわたって微細化をはかることは工業
的に可能ではあるがエネルギー面から見てきわめて不利
である。As described above, the refinement of the crystal grains is extremely effective for the brittle crack propagation arresting property, but there is a limit to the refinement in the current ordinary manufacturing method of thick steel plates. Further, it is industrially possible to reduce the size in the plate thickness direction by a special method including a reheating step after water cooling as described in JP-B-49-7293, but from an energy point of view. It is extremely disadvantageous.
一方、実際に脆性き裂伝播停止に大きな効果を示すのは
板厚中心部の結晶粒の微細化よりもむしろ板厚表層部の
結晶粒の微細化である。これは脆性き裂伝播時に板厚表
層部はシアリップと呼ばれる塑性変形を示し、伝播する
脆性き裂が有する運動エネルギーを吸収するため、特に
板厚表層部の結晶粒が微細であれば優れた脆性き裂伝播
停止特性を示すものである。On the other hand, it is the refinement of the crystal grains in the surface layer portion of the sheet thickness rather than the refinement of the crystal grains in the center portion of the sheet thickness that actually has a great effect on stopping the brittle crack propagation. This is because when the brittle crack propagates, the surface portion of the plate exhibits plastic deformation called shear lip, and absorbs the kinetic energy of the brittle crack that propagates. It shows the crack propagation stopping property.
したがって特公昭49-7293号公報記載のような水冷後の
加熱工程を含むような特殊な処理を施すことなく板厚表
層部の結晶粒を微細化できればエネルギー面での大きな
負担なく脆性き裂伝播停止特性の優れた厚鋼板を得るこ
とができる。Therefore, if the crystal grains in the surface layer of the plate thickness can be made fine without performing a special treatment that includes a heating step after water cooling as described in JP-B-49-7293, brittle crack propagation without a heavy energy burden. A thick steel plate having excellent stopping characteristics can be obtained.
その製造方法は次の通りである。The manufacturing method is as follows.
重量％で、 Ｃ 0.01〜0.30％、 Mn 2.0％以下、 Si 0.5％以下、 Al 0.1％以下、 Ｎ 0.001〜0.01％、 又は更に、Ｂ 0.0005〜0.0015％、 Cu 0.9％以下、 Ni 1.0％以下、 Cr 0.5％以下、 Mo 0.5％以下の１種または２種以上を含み又は更に、N
b 0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなる連続鋳造鋼片をAc3以上に
加熱した後、あるいは連続鋳造ままで、あるいは連続鋳
片を所定の厚みまで粗圧延を行った後で、該鋳片の両表
面より鋳片厚中心方向に鋳片厚の１／８以上がAr3以下
となるまで鋳片厚平均冷却速度が２℃／ｓ以上となるよ
うに冷却し、引き続き該鋳片厚方向に温度差をつけたま
ま鋳片両表面より鋳片厚中心方向に鋳片厚の１／８以上
がフェライト１相またはフェライト−オーステナイト２
相状態で圧延を開始し、かつ該圧延中または圧延終了後
鋳片厚全域にわたりAc3を越える温度まで復熱させるこ
とを特徴とする脆性き裂伝播停止特性の優れた厚鋼板の
製造法。% By weight, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, or further B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, One or more of Cr 0.5% or less and Mo 0.5% or less, or further N
b 0.05% or less, Ti 0.1% or less, 1 type or 2 types or more, and the balance is Fe
And a continuously cast steel slab consisting of inevitable impurities is heated to Ac 3 or more, or as it is in continuous casting, or after the continuous slab is roughly rolled to a predetermined thickness, cast from both surfaces of the slab. Cool the slab thickness average cooling rate to 2 ° C / s or more until 1/8 or more of the slab thickness becomes Ar 3 or less in the center direction of the slab thickness, and then make a temperature difference in the slab thickness direction. As it is, 1/8 or more of the thickness of the slab from the both surfaces of the slab toward the center of the slab thickness is ferrite 1 phase or ferrite-austenite 2
A method for producing a thick steel sheet having excellent brittle crack propagation arresting characteristics, characterized in that rolling is started in a phase state and is reheated to a temperature exceeding Ac 3 throughout the thickness of the cast piece during or after the rolling.
重量％で、 Ｃ 0.01〜0.30％、 Mn 2.0％以下、 Si 0.5％以下、 Al 0.1％以下、 Ｎ 0.001〜0.01％、 又は更に、Ｂ 0.0005〜0.0015％、 Cu 0.9％以下、 Ni 1.0％以下、 Cr 0.5％以下、 Mo 0.5％以下の１種または２種以上を含み又は更に、N
b 0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなる鋳造鋳片をAc3以上に加熱
した後、あるいは鋳片を所定の厚みまで粗圧延を行った
後で、該鋳片の両表面より鋳片厚中心方向に鋳片厚の１
／８以上がAr3以下となるまで鋳片厚平均冷却速度が２
℃／ｓ以上となるように冷却し、引き続き該鋳片厚方向
に温度差をつけたまま鋳片両表面より鋳片厚中心方向に
鋳片厚の１／８以上がフェライト１相またはフェライト
−オーステナイト２相状態で圧延を開始し、かつ該圧延
中または圧延終了後鋳片厚全域にわたりAc3を越える温
度まで復熱させることを特徴とする脆性き裂伝播停止特
性の優れた厚鋼板の製造法。% By weight, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, or further B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, One or more of Cr 0.5% or less and Mo 0.5% or less, or further N
b 0.05% or less, Ti 0.1% or less, 1 type or 2 types or more, and the balance is Fe
And after heating the cast slab consisting of unavoidable impurities to Ac 3 or more, or after roughly rolling the slab to a predetermined thickness, the slab thickness from both surfaces of the slab toward the slab thickness center direction Of 1
Slab thickness average cooling rate is 2 until / 8 or more becomes Ar 3 or less
C./s or more, and continuously with a temperature difference in the slab thickness direction, 1/8 or more of the slab thickness from both surfaces of the slab toward the center of the slab thickness is ferrite 1 phase or ferrite- Manufacture of a thick steel sheet having excellent brittle crack propagation arresting characteristics, characterized in that rolling is started in the austenite two-phase state, and reheating is carried out to a temperature exceeding Ac 3 over the entire thickness of the slab during or after the rolling. Law.
更に上記の製造法に加え必要に応じ、最終圧延終了後、
引き続き板厚平均で４０℃／ｓ以下の冷却速度で板厚平
均温度５００℃以下となるまで制御冷却を行うことを特
徴とする製造方法である。In addition to the above manufacturing method, if necessary, after the final rolling,
Subsequently, the method is characterized in that controlled cooling is performed at a cooling rate of 40 ° C./s or less on average in the sheet thickness until the sheet temperature average temperature becomes 500 ° C. or less.
鋳造ままの鋳片または該鋳片を所定の厚みまで粗圧延し
た粗圧延材を、あるいは鋳造後の鋳片又は鋼片をAc3以
上に加熱した鋳片または該鋳片を所定の厚みまで粗圧延
した粗圧延材を表層部の1/8以上がAr3以下になるまで冷
却し引き続き温度差のついた状態でフェライト１相ある
いはフェライト−オーステナイト２相域で圧延を開始し
て圧延途中又は圧延終了後に再度Ac3以上に自然に復熱
するようにする。As-cast slab or rough-rolled material obtained by roughly rolling the slab to a predetermined thickness, or a cast slab or steel slab that has been heated to Ac 3 or more or a slab that has been rough-rolled to a predetermined thickness. The rough rolled material that has been rolled is cooled until 1/8 or more of the surface layer becomes Ar 3 or less, and then rolling is started in the ferrite 1 phase or ferrite-austenite 2 phase region with a temperature difference, during or after rolling. After that, try to reheat naturally to Ac 3 or higher.
このような加工熱処理効果により圧延終了後のオーステ
ナイト結晶粒はきわめて微細になる。即ちフェライト１
相あるいはフェライト−オーステナイト２相域で圧延加
工を加えて結晶粒を延伸させることによりフェライトか
らオーステナイトへの逆変態時にきわめて微細なオース
テナイト結晶粒を得ることができる。Due to such a thermomechanical treatment effect, the austenite crystal grains after rolling are extremely fine. That is, ferrite 1
By rolling in the phase or ferrite-austenite two-phase region and stretching the crystal grains, extremely fine austenite crystal grains can be obtained during the reverse transformation from ferrite to austenite.
このような方法で得られた微細なオーステナイト結晶粒
はフェライト１相又はフェライト−オーステナイト２相
状態で圧延された加工フェライトがオーステナイトへ逆
変態することにより初めて得られるものであり、圧延を
ともなわない温度制御のみでオーステナイト→フェライ
ト→オーステナイトと変態させた後に圧延を加える方法
では、このような微細な組織を得ることはできない。The fine austenite crystal grains obtained by such a method are first obtained by the reverse transformation of the worked ferrite rolled in the ferrite 1-phase or ferrite-austenite 2-phase state into austenite, and the temperature without rolling. Such a fine structure cannot be obtained by the method of rolling after the transformation of austenite → ferrite → austenite only by control.
またフェライト１相またはフェライト−オーステナイト
２相状態で圧延を開始した後、圧延途中または圧延終了
後に板表面の温度が再びAc3以上に復熱しない場合は、
加工されたフェライトがそのまま最終組織まで残留し靱
性を劣化させるため板厚全域にわたって圧延途中または
圧延終了後にAc3以上に自然に復熱するような冷却を施
すことが必要である。When the temperature of the plate surface does not reheat to Ac 3 or more after the rolling is started in the ferrite 1 phase or the ferrite-austenite 2 phase state, during or after the rolling,
Since the processed ferrite remains as it is in the final structure and deteriorates the toughness, it is necessary to perform cooling so as to spontaneously reheat to Ac 3 or higher during or after rolling over the entire plate thickness.
このように本発明によれば、圧延前の制御冷却時にAr3
以下まで冷却され引き続きフェライト１相又はフェライ
ト−オーステナイト２相状態で圧延された部分の結晶粒
がきわめて微細化されるので脆性き裂伝播停止特性の向
上に大きく寄与するが、かかる効果を得るには板厚両表
面より板厚中心方向に板厚の1/8以上の距離にわたる細
粒化が必要である。Thus, according to the present invention, Ar 3
The crystal grains in the portion that has been cooled to the following temperature and subsequently rolled in the ferrite 1-phase or ferrite-austenite 2-phase state are extremely refined, which greatly contributes to the improvement of the brittle crack propagation arresting property. It is necessary to reduce the grain size from both surfaces to the center of the plate thickness over a distance of 1/8 or more of the plate thickness.
仕上圧延が終了しかつ板表面温度がAc3以上に復熱した
後は放冷しても良いが、母材の強度靱性を高めるため引
き続き40℃／ｓ以下の冷速で500℃以下まで強制冷却し
ても良い。After finishing rolling is completed and the plate surface temperature is reheated to Ac 3 or higher, it may be allowed to cool, but in order to increase the strength and toughness of the base metal, it is continuously forced to 500 ° C or lower at a cooling rate of 40 ° C / s or less. It may be cooled.
冷速は40℃／ｓ以上ではマルテンサイトを生じて靱性が
劣化するため40℃／ｓ以下とした。また５００℃以上の
水冷停止では強度上昇の効果が小さいため強制冷却する
場合は所定の強度に応じて５００℃以下まで水冷する。When the cooling rate is 40 ° C./s or more, martensite occurs and the toughness deteriorates, so the cooling rate was set to 40 ° C./s or less. Further, since the effect of increasing the strength is small when the water cooling is stopped at 500 ° C. or higher, when forced cooling is performed, the water is cooled to 500 ° C. or lower according to the predetermined strength.
このような方法で製造された鋼は、その板厚表面より板
厚中心方向に板厚の1/8以上の範囲にわたって、Nb,Tiを
含まない鋼では粒径５μ以下のフェライトが面積率にし
て５０％以上存在し、またNb,Tiを含む鋼では粒径３μ
以下のフェライトが面積率にして５０％以上存在しきわ
めて良好な脆性き裂伝播停止特性を示す。The steel produced by such a method has a surface area of 1/8 or more of the thickness from the surface of the thickness toward the center of the thickness. Is present in 50% or more, and the grain size is 3μ in steel containing Nb and Ti.
The following ferrite is present in an area ratio of 50% or more, and exhibits extremely good brittle crack propagation stopping characteristics.
（実施例） 次に本発明を実施例にもとづいて詳細に説明する。まず
第１表に示す代表的な成分の鋼について第２表に示す本
発明方法および比較方法を適用した場合、第３表に示し
た機械的性質となり明らかに本発明鋼は優れた特性を示
し、本発明の方法は有効である。(Example) Next, the present invention will be described in detail based on examples. First, when the method of the present invention and the comparative method shown in Table 2 are applied to steels having typical components shown in Table 1, the mechanical properties shown in Table 3 are obtained, and obviously the steel of the present invention shows excellent properties. The method of the present invention is effective.
（発明の効果） 以上の実施例から明らかなごとく本発明によれば、従来
法により得られた厚鋼板に比べきわめて優れた脆性き裂
伝播停止特性を有する厚鋼板を有利に製造することがで
き、優れた特性を有する厚鋼板を供給できる産業上の効
果は極めて顕著なものがある。 (Effects of the Invention) As is clear from the above examples, according to the present invention, it is possible to advantageously manufacture a thick steel sheet having a brittle crack propagation arresting property which is extremely superior to the thick steel sheets obtained by the conventional method. The industrial effect of supplying thick steel plates with excellent properties is extremely remarkable.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/06 38/54 (56)参考文献 特開 昭53−40620（ＪＰ，Ａ) 特開 昭53−40621（ＪＰ，Ａ) 特開 昭58−19432（ＪＰ，Ａ) 特開 昭59−47323（ＪＰ，Ａ) 特開 昭59−182916（ＪＰ，Ａ) 特開 昭60−56017（ＪＰ，Ａ)─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 5 Identification code Internal reference number FI Technical display location C22C 38/06 38/54 (56) References JP-A-53-40620 (JP, A) JP-A JP-A-53-40621 (JP, A) JP-A-58-19432 (JP, A) JP-A-59-47323 (JP, A) JP-A-59-182916 (JP, A) JP-A-60-56017 (JP , A)
Claims (15)
り板厚中心方向に板厚の１／８以上の距離にわたって５
μｍ以下の結晶粒径を有するフェライト結晶粒が面積率
にして５０％以上存在することを特徴とする脆性き裂伝
播停止特性の優れた厚鋼板。1. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, the balance being Fe and inevitable impurities, and both surfaces of a thick steel plate. 5 toward the center of the plate thickness over a distance of ⅛ or more of the plate thickness
A thick steel sheet excellent in brittle crack propagation arresting characteristics, characterized in that ferrite crystal grains having a crystal grain size of μm or less are present in an area ratio of 50% or more.
び不可避的不純物よりなり、厚鋼板両表面より板厚中心
方向に板厚の１／８以上の距離にわたって５μｍ以下の
結晶粒径を有するフェライト結晶粒が面積率にして５０
％以上存在することを特徴とする脆性き裂伝播停止特性
の優れた厚鋼板。2. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, Cr 0.5% or less, Mo 0.5% or less 1 type or 2 types or more and the balance is Fe and unavoidable impurities, and 1/8 or more of the plate thickness from both surfaces of the thick steel plate toward the center of the plate thickness. The area ratio of ferrite crystal grains having a crystal grain size of 5 μm or less over the distance is 50
% Steel plate having excellent brittle crack propagation arresting characteristics.
及び不可避的不純物よりなり、厚鋼板両表面より板厚中
心方向に板厚の１／８以上の距離にわたって３μｍ以下
の結晶粒径を有するフェライト結晶粒が面積率にして５
０％以上存在することを特徴とする脆性き裂伝播停止特
性の優れた厚鋼板。3. One kind by weight% of C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, Nb 0.05% or less, Ti 0.1% or less. Or contains two or more kinds, and the balance is Fe
And unavoidable impurities, and ferrite crystal grains having a crystal grain size of 3 μm or less over the distance of ⅛ or more of the plate thickness in the center direction of the plate thickness from both surfaces of the thick steel plate are 5 in area ratio
A thick steel sheet excellent in brittle crack propagation arresting characteristics characterized by being present in an amount of 0% or more.
0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなり、厚鋼板両表面より板厚中
心方向に板厚の１／８以上の距離にわたって３μｍ以下
の結晶粒径を有するフェライト結晶粒が面積率にして５
０％以上存在することを特徴とする脆性き裂伝播停止特
性の優れた厚鋼板。4. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, Cr 0.5% or less, Mo 0.5% or less 1 type or 2 types or more, and also Nb
0.05% or less, Ti 0.1% or less 1 type or 2 types or more, and the balance is Fe
And unavoidable impurities, and ferrite crystal grains having a crystal grain size of 3 μm or less over the distance of ⅛ or more of the plate thickness in the center direction of the plate thickness from both surfaces of the thick steel plate are 5 in area ratio
A thick steel sheet excellent in brittle crack propagation arresting characteristics characterized by being present in an amount of 0% or more.
3以上に加熱した後、 あるいは連続鋳造ままで、該鋳片の両表面より鋳片厚中
心方向に鋳片厚の１／８以上がAr3以下となるまで鋳片
厚平均冷却速度が２℃／ｓ以上となるように冷却し、引
き続き該鋳片厚方向に温度差をつけたまま鋳片両表面よ
り鋳片厚中心方向に鋳片厚の１／８以上がフェライト１
相またはフェライト−オーステナイト２相状態で圧延を
開始し、かつ該圧延中または圧延終了後鋳片厚全域にわ
たりAc3を越える温度まで復熱させることを特徴とする
脆性き裂伝播停止特性の優れた厚鋼板の製造法。5. A continuous cast slab containing 0.01% to 0.30% by weight of C, 2.0% or less of Mn, 0.5% or less of Si, 0.1% or less of Al, 0.001 to 0.01% of N, and the balance being Fe and unavoidable impurities. Ac
After heating to 3 or more, or as it is in continuous casting, the slab thickness average cooling rate is 2 ° C. until 1/8 or more of the slab thickness becomes Ar 3 or less from both surfaces of the slab toward the center of the slab thickness. 1 / s or more of the slab thickness toward the center of the slab thickness from both surfaces of the slab with the temperature difference in the thickness direction of the slab being 1% or more of ferrite 1
Phase or ferrite-austenite two-phase state is started, and the brittle crack propagation arresting property is excellent, which is characterized by reheating to a temperature exceeding Ac 3 throughout the thickness of the slab during or after the rolling. Manufacturing method of thick steel plate.
び不可避的不純物よりなる連続鋳造鋳片をAc3以上に加
熱した後、 あるいは連続鋳造ままで、該鋳片の両表面より鋳片厚中
心方向に鋳片厚の１／８以上がAr3以下となるまで鋳片
厚平均冷却速度が２℃／ｓ以上となるように冷却し、引
き続き該鋳片厚方向に温度差をつけたまま鋳片両表面よ
り鋳片厚中心方向に鋳片厚の１／８以上がフェライト１
相またはフェライト−オーステナイト２相状態で圧延を
開始し、かつ該圧延中または圧延終了後鋳片厚全域にわ
たりAc3を越える温度まで復熱させることを特徴とする
脆性き裂伝播停止特性の優れた厚鋼板の製造法。6. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni After heating a continuously cast slab containing one or more of 1.0% or less, Cr 0.5% or less, and Mo 0.5% or less and the balance of Fe and inevitable impurities to Ac 3 or more, or as continuous casting, From both surfaces of the slab, cooling is performed so that the slab thickness average cooling rate is 2 ° C./s or more until ⅛ or more of the slab thickness becomes Ar 3 or less in the slab thickness center direction, and the slab is continuously cast. Ferrite 1 is ⅛ or more of the cast piece thickness from both surfaces of the cast piece toward the center of the cast piece thickness with a temperature difference in the cast piece thickness direction.
Phase or ferrite-austenite two-phase state is started, and the brittle crack propagation arresting property is excellent, which is characterized by reheating to a temperature exceeding Ac 3 throughout the thickness of the slab during or after the rolling. Manufacturing method of thick steel plate.
及び不可避的不純物よりなる連続鋳造鋳片をAc3以上に
加熱した後、 あるいは連続鋳造ままで、該鋳片の両表面より鋳片厚中
心方向に鋳片厚の１／８以上がAr3以下となるまで鋳片
厚平均冷却速度が２℃／ｓ以上となるように冷却し、引
き続き該鋳片厚方向に温度差をつけたまま鋳片両表面よ
り鋳片厚中心方向に鋳片厚の１／８以上がフェライト１
相またはフェライト−オーステナイト２相状態で圧延を
開始し、かつ該圧延中または圧延終了後鋳片厚全域にわ
たりAc3を越える温度まで復熱させることを特徴とする
脆性き裂伝播停止特性の優れた厚鋼板の製造法。7. A kind of C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, and Nb 0.05% or less, Ti 0.1% or less in weight%. Or contains two or more kinds, and the balance is Fe
And a continuous cast slab consisting of unavoidable impurities is heated to Ac 3 or more, or as it is in continuous casting, 1/8 or more of the slab thickness is Ar 3 or less from both surfaces of the slab toward the center of the slab thickness. Until the average thickness of the slab is cooled so that the average cooling rate of the slab becomes 2 ° C./s or more. 1/8 or more ferrite 1
Phase or ferrite-austenite two-phase state is started, and the brittle crack propagation arresting property is excellent, which is characterized by reheating to a temperature exceeding Ac 3 throughout the thickness of the slab during or after the rolling. Manufacturing method of thick steel plate.
0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなる連続鋳造鋳片をAc3以上に
加熱した後、 あるいは連続鋳造ままで、該鋳片の両表面より鋳片厚中
心方向に鋳片厚の１／８以上がAr3以下となるまで鋳片
厚平均冷却速度が２℃／ｓ以上となるように冷却し、引
き続き該鋳片厚方向に温度差をつけたまま鋳片両表面よ
り鋳片厚中心方向に鋳片厚の１／８以上がフェライト１
相またはフェライト−オーステナイト２相状態で圧延を
開始し、かつ該圧延中または圧延終了後鋳片厚全域にわ
たりAc3を越える温度まで復熱させることを特徴とする
脆性き裂伝播停止特性の優れた厚鋼板の製造法。8. In% by weight, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, Cr 0.5% or less, Mo 0.5% or less 1 type or 2 types or more, and also Nb
0.05% or less, Ti 0.1% or less 1 type or 2 types or more, and the balance is Fe
And a continuous cast slab consisting of unavoidable impurities is heated to Ac 3 or more, or as it is in continuous casting, 1/8 or more of the slab thickness is Ar 3 or less from both surfaces of the slab toward the center of the slab thickness. Until the average thickness of the slab is cooled so that the average cooling rate of the slab becomes 2 ° C./s or more. 1/8 or more ferrite 1
Phase or ferrite-austenite two-phase state is started, and the brittle crack propagation arresting property is excellent, which is characterized by reheating to a temperature exceeding Ac 3 throughout the thickness of the slab during or after the rolling. Manufacturing method of thick steel plate.
圧延終了後、該粗圧延板の両表面より板厚中心方向に板
厚の１／８以上がAr3以下となるまで板厚平均冷却速度
が２℃／ｓ以上となるように冷却することを特徴とする
特許請求の範囲第５項乃至第８項のいずれか１項に記載
の脆性き裂伝播停止特性の優れた厚鋼板の製造法。9. A continuous cast slab is roughly rolled to a predetermined thickness, and after the rough rolling is completed, the plate is rolled from both surfaces of the roughly rolled plate toward the center of the plate thickness until 1/8 or more of the plate thickness becomes Ar 3 or less. Cooling is performed so that the thickness average cooling rate is 2 ° C./s or more, and the thickness is excellent in brittle crack propagation arresting property according to any one of claims 5 to 8. Steel plate manufacturing method.
加熱した後、該鋼片の両表面より鋼片厚中心方向に鋼片
厚の１／８以上がAr3以下となるまで鋼片厚平均冷却速
度が２℃／ｓ以上となるように冷却し、引き続き該鋼片
厚方向に温度差をつけたまま鋼片両表面より鋼片厚中心
方向に鋼片厚の１／８以上がフェライト１相またはフェ
ライト−オーステナイト２相状態で圧延を開始し、かつ
該圧延中または圧延終了後鋼片厚全域にわたりAc3を越
える温度まで復熱させることを特徴とする脆性き裂伝播
停止特性の優れた厚鋼板の製造法。10. A steel slab composed of 0.01 to 0.30% by weight, Mn 2.0% or less, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, and the balance being Fe and unavoidable impurities by Ac 3 After heating to the above temperature, the average slab thickness cooling rate should be 2 ° C./s or more until 1/8 or more of the slab thickness becomes Ar 3 or less from both surfaces of the slab toward the center of the slab thickness. After cooling, continuously rolling with a temperature difference in the thickness direction of the steel piece, 1/8 or more of the steel piece thickness toward the center of the steel piece thickness from both surfaces of the steel piece in the ferrite 1 phase or ferrite-austenite 2 phase state. And a method for producing a thick steel sheet having excellent brittle crack propagation arresting characteristics, characterized in that the steel plate is reheated to a temperature exceeding Ac 3 during the rolling or after the rolling is completed.
び不可避的不純物よりなる鋼片をAc3以上に加熱した
後、該鋼片の両表面より鋼片厚中心方向に鋼片厚の１／
８以上がAr3以下となるまで鋼片厚平均冷却速度が２℃
／ｓ以上となるように冷却し、引き続き該鋼片厚方向に
温度差をつけたまま鋼片両表面より鋼片厚中心方向に鋼
片厚の１／８以上がフェライト１相またはフェライト−
オーステナイト２相状態で圧延を開始し、かつ該圧延中
または圧延終了後鋼片厚全域にわたりAc3を越える温度
まで復熱させることを特徴とする脆性き裂伝播停止特性
の優れた厚鋼板の製造法。11. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni After heating a steel slab containing one or more of 1.0% or less, Cr 0.5% or less, and Mo 0.5% or less and the balance of Fe and unavoidable impurities to Ac 3 or more, steel from both surfaces of the steel slab is heated. 1 / thickness of steel piece in the center direction
Steel slab thickness average cooling rate is 2 ℃ until 8 or more becomes Ar 3 or less
/ S or more, and subsequently, with a temperature difference in the thickness direction of the steel piece, 1/8 or more of the steel piece thickness in the center direction of the steel piece thickness from both surfaces of the steel piece is ferrite 1 phase or ferrite-
Manufacture of a thick steel sheet excellent in brittle crack propagation arresting characteristics, characterized in that rolling is started in the austenite two-phase state, and reheating is carried out to a temperature exceeding Ac 3 throughout the thickness of the billet during or after the rolling. Law.
及び不可避的不純物よりなる鋼片をAc3以上に加熱した
後、該鋼片の両表面より鋼片厚中心方向に鋼片厚の１／
８以上がAr3以下となるまで鋼片厚平均冷却速度が２℃
／ｓ以上となるように冷却し、引き続き該鋼片厚方向に
温度差をつけたまま鋼片両表面より鋼片厚中心方向に鋼
片厚の１／８以上がフェライト１相またはフェライト−
オーステナイト２相状態で圧延を開始し、かつ該圧延中
または圧延終了後鋼片厚全域にわたりAc3を越える温度
まで復熱させることを特徴とする脆性き裂伝播停止特性
の優れた厚鋼板の製造法。12. One kind of C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, further Nb 0.05% or less, Ti 0.1% or less by weight%. Or contains two or more kinds, and the balance is Fe
And a steel slab consisting of unavoidable impurities are heated to Ac 3 or more, and then 1 /
Steel slab thickness average cooling rate is 2 ℃ until 8 or more becomes Ar 3 or less
/ S or more, and subsequently, with a temperature difference in the thickness direction of the steel piece, 1/8 or more of the steel piece thickness in the center direction of the steel piece thickness from both surfaces of the steel piece is ferrite 1 phase or ferrite-
Manufacture of a thick steel sheet excellent in brittle crack propagation arresting characteristics, characterized in that rolling is started in the austenite two-phase state, and reheating is carried out to a temperature exceeding Ac 3 throughout the thickness of the billet during or after the rolling. Law.
0.05％以下、 Ti 0.1％以下の１種または２種以上を含み、残部がFe
及び不可避的不純物よりなる鋼片をAc3以上に加熱した
後、該鋼片の両表面より鋼片厚中心方向に鋼片厚の１／
８以上がAr3以下となるまで鋼片厚平均冷却速度が２℃
／ｓ以上となるように冷却し、引き続き該鋼片厚方向に
温度差をつけたまま鋼片両表面より鋼片厚中心方向に鋼
片厚の１／８以上がフェライト１相またはフェライト−
オーステナイト２相状態で圧延を開始し、かつ該圧延中
または圧延終了後鋼片厚全域にわたりAc3を越える温度
まで復熱させることを特徴とする脆性き裂伝播停止特性
の優れた厚鋼板の製造法。13. By weight%, C 0.01 to 0.30%, Mn 2.0% or less, Si 0.5% or less, Al 0.1% or less, N 0.001 to 0.01%, B 0.0005 to 0.0015%, Cu 0.9% or less, Ni 1.0% or less, Cr 0.5% or less, Mo 0.5% or less 1 type or 2 types or more, and also Nb
0.05% or less, Ti 0.1% or less 1 type or 2 types or more, and the balance is Fe
And a steel slab consisting of unavoidable impurities are heated to Ac 3 or more, and then 1 /
Steel slab thickness average cooling rate is 2 ℃ until 8 or more becomes Ar 3 or less
/ S or more, and subsequently, with a temperature difference in the thickness direction of the steel piece, 1/8 or more of the steel piece thickness in the center direction of the steel piece thickness from both surfaces of the steel piece is ferrite 1 phase or ferrite-
Manufacture of a thick steel sheet excellent in brittle crack propagation arresting characteristics, characterized in that rolling is started in the austenite two-phase state, and reheating is carried out to a temperature exceeding Ac 3 throughout the thickness of the billet during or after the rolling. Law.
延終了後、該粗圧延板の両表面より板厚中心方向に板厚
の１／８以上がAr3以下となるまで板厚平均冷却速度が
２℃／ｓ以上となるように冷却することを特徴とする特
許請求の範囲第１０項乃至第１３項のいずれか１項に記
載の脆性き裂伝播停止特性の優れた厚鋼板の製造法。14. A steel slab is roughly rolled to a predetermined thickness, and after the rough rolling is completed, plate thickness is reduced from both surfaces of the roughly rolled plate in the center direction of the plate thickness until 1/8 or more of the plate thickness becomes Ar 3 or less. A thick steel sheet having excellent brittle crack propagation arresting properties according to any one of claims 10 to 13, characterized in that cooling is performed so that an average cooling rate is 2 ° C / s or more. Manufacturing method.
／ｓ以下の冷却速度で板厚平均温度が５００℃以下の冷
却速度で板厚平均温度が５００℃以下となるまで制御冷
却を行うことを特徴とする特許請求の範囲第５項乃至第
１４項のいずれか１項に記載の脆性き裂伝播停止特性の
優れた厚鋼板の製造法。15. An average plate thickness of 40 ° C. after completion of final rolling
The controlled cooling is performed at a cooling rate of / s or less until the sheet thickness average temperature becomes 500 ° C. or less until the sheet thickness average temperature becomes 500 ° C. or less. The method for manufacturing a thick steel sheet having excellent brittle crack propagation arresting properties according to any one of 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60074786A JPH064903B2 (en) | 1985-04-09 | 1985-04-09 | Steel plate with excellent brittle crack propagation arresting property and its manufacturing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60074786A JPH064903B2 (en) | 1985-04-09 | 1985-04-09 | Steel plate with excellent brittle crack propagation arresting property and its manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61235534A JPS61235534A (en) | 1986-10-20 |
| JPH064903B2 true JPH064903B2 (en) | 1994-01-19 |
Family
ID=13557317
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60074786A Expired - Fee Related JPH064903B2 (en) | 1985-04-09 | 1985-04-09 | Steel plate with excellent brittle crack propagation arresting property and its manufacturing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH064903B2 (en) |
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Also Published As
| Publication number | Publication date |
|---|---|
| JPS61235534A (en) | 1986-10-20 |
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