JPS624450B2 - - Google Patents
Info
- Publication number
- JPS624450B2 JPS624450B2 JP57111351A JP11135182A JPS624450B2 JP S624450 B2 JPS624450 B2 JP S624450B2 JP 57111351 A JP57111351 A JP 57111351A JP 11135182 A JP11135182 A JP 11135182A JP S624450 B2 JPS624450 B2 JP S624450B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- temperature
- steel
- rolling
- hot
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 84
- 239000010959 steel Substances 0.000 claims description 84
- 238000005096 rolling process Methods 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 14
- 230000009467 reduction Effects 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 239000012535 impurity Substances 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000000463 material Substances 0.000 description 27
- 230000000694 effects Effects 0.000 description 23
- 238000005452 bending Methods 0.000 description 20
- 238000005098 hot rolling Methods 0.000 description 12
- 229910000859 α-Fe Inorganic materials 0.000 description 12
- 238000004804 winding Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- 238000005728 strengthening Methods 0.000 description 7
- 230000006866 deterioration Effects 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 238000005482 strain hardening Methods 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 238000010583 slow cooling Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000655 Killed steel Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
この発明は、引張強さ:70Kg/mm2以上の高強度
をもち、かつ加工性および低温靭性のすぐれた
Ti添加熱延高張力鋼板の製造法に関するもので
ある。
近年、各種建造物や産業機械等の構造材とし
て、高強度でかつ加工性のすぐれた鋼材への要求
が高まつており、これらに対処するために各種の
鋼材が開発され、使用されるようになつてきた。
Nb添加鋼やV添加鋼、あるいはTi添加鋼等がそ
れである。そして、この中でも、製造価格が安く
しかも高強度が得られるとの理由で、Ti添加鋼
が注目されているが、これはNb添加鋼やV添加
鋼よりも靭性が劣るという問題点があつた。
しかしながら最近では、エネルギー事情の悪化
などから、極めて苛酷な環境下での資源開発のや
むなきに至つており、例えば、特に板厚が4.5mm
以上の高張力鋼板の場合には、冷間加工による塑
性変形を加えて寒冷地で使用すると塑性変形部か
ら脆性破壊を生ずる危険性があり、このような点
からも、高強度かつ易加工性という特性に加え
て、寒冷地での使用にも十分に耐えられるよう
な、すぐれた低温靭性をも兼備した高張力鋼板が
強く要望されていた。
そこで、このような要望を満足する高張力鋼板
を提供するものとして、特公昭55―45614号公報
に記載されているような、Ti添加鋼を熱間で制
御圧延する方法が提案された。
Ti添加熱延高張力鋼板の特徴とするところ
は、TiCの析出強化を利用すると同時に、A系介
在物となるMnSをTiSに置き替えてC系介在物と
なし、これによつて加工性の向上を図るものであ
り、高強度を有するとともに、端面を機械切削加
工仕上げした供試材を使用するJIS規格曲げ試験
では密着曲げまで可能であるという、非常にすぐ
れた冷間加工性を有するものとされている。そし
て、上記特公昭55―45614号公報に記載されてい
る方法は、このような特性を有するTi添加熱延
高張力鋼板の製造の際に制御圧延を施すことによ
つて、さらにその低温靭性の改善を図つたもので
ある。
ところで、JIS規格の曲げ試験においては、上
述のように供試材として端面を機械切削加工仕上
げしたものを用いるが、実際の構造部材の生産に
おいては、シヤー端面付の素材(シヤー切断面を
加工してない素材)がそのまま冷間加工に供され
る場合がほとんどであり、したがつて実用面から
は、シヤー端面付の試片での曲げ性能の良好さが
冷間加工用鋼板に要求されることとなる。
ところが、上記特公昭55―45614号公報に記載
されている方法で得られる鋼板をも含めて、Ti
添加熱延鋼板は、一般に、シヤー端面付の曲げ試
験性能が不良であり、曲げ加工の際に端面部に割
れを生ずるという重大な問題のあることがその後
の実用化の段階で明らかとなつてきた。
本発明者は、上述のような観点から、引張強さ
が70Kg/mm2以上の高強度と、すぐれた加工性並び
に低温靭性を有することはもちろん、特にシヤー
端面付の素材の加工性の良好な高張力鋼板を得る
べく、鋭意研究を重ねた結果、特定の成分組成の
Ti添加鋼を制御圧延した後、従来の常識を破つ
た約400℃という低温で巻取れば、引張強さが70
Kg/mm2以上の高い値を示すとともに、シヤー端面
付の鋼板の曲げ割れが改善され、低温靭性にもす
ぐれた高張力鋼板が得られることを見出した。そ
して、これを基にしてさらに研究を続け、以下(a)
〜(c)に示す如き知見を得るに至つたのである。す
なわち、
(a) 高強度を有するTi添加熱延鋼板を製造する
に際して、熱延後、通常の巻取温度である約
600℃で巻取ると、確かに、JIS規格曲げの範囲
においては密着曲げまで可能であつてすぐれた
加工性を有していると判断せざるを得ないが、
シヤー端面付の素材を曲げた場合に、そのフエ
ライト粒界の脆さに起因する曲げ割れを回避す
るのが困難であるうえ、TiCの析出によつて低
温靭性も劣化するものである。ところが、巻取
温度を450℃未満〜200℃の範囲に制御すると、
上述のようなTiCの析出が抑制されるとともに
変態強化がなされてフエライト粒界の脆化が抑
制され、シヤー端面付の曲げ性能が著しく向上
するばかりでなく、シヤルピー破面遷移温度ま
でもが改善され、特に、900℃以下にて合計30
〜90%の圧下を行ない870〜800℃の温度で圧延
を終了するという制御圧延と結び付けることに
より、シヤルピー破面遷移温度の極めて向上し
た高張力鋼板が得られること、
(b) そして、これに加えて、Ti添加鋼中のP分
を低減すれば、上記(a)項で述べた各特性がより
向上すること、
(c) 該Ti添加鋼に、Ca、B、およびCrのうちの
1種または2種以上の特定量を含有せしめれ
ば、より以上の加工性の向上と強靭化が図れる
こと。
なお、本発明者は、これらの知見を得るにあた
つて、Ti添加鋼の機械的性質に及ぼす巻取温度
の影響を調査するための熱延シミユレーシヨン実
験法を確立し、各種実験を繰返したことはいうま
でもない。
この熱延シミユレーシヨン実験法とは、鋼材の
圧延後、所定の温度まで水スプレーにより急冷
し、その後、該所定温度にまで昇温してある炉に
圧延材を投入して炉冷却(冷却速度:20℃/hr)
を行なう方法である。そして、この際の「所定温
度」を巻取温度に一致させれば、実作業における
熱延・巻取りにおけると同様組織並びに特性を有
する鋼板が得られることを確認した。
このような熱延シミユレーシヨン実験法によ
り、820℃仕上げの制御圧延下でTi添加鋼の機械
的性質に及ぼす巻取温度の影響を調査した結果を
第1図に示す。
第1図は、0.10%C―0.30%Si―1.65%Mn―
0.002%S―0.17%Ti―0.025%Al―0.0035%N鋼
(以下、成分組成割合を示す%は重量%とする)
に、900℃以下で50%の圧下を加え、仕上温度:
820℃にて6mm厚の熱延鋼板を得た後、巻取冷却
速度に相当する10℃/secの冷却速度で冷却したと
きの、鋼板の機械的性質に及ぼす巻取温度の影響
を示す線図である。第1図からは、巻取温度が
400℃を越えるあたりから、シヤー端面付板材の
曲げ性、並びにシヤルピー破面遷移温度の劣化が
目立つようになり、特に500℃を越えると実用的
に好ましくない程度にまで該劣化傾向がはなはだ
しくなるが、巻取温度が450℃未満〜200℃の範囲
では加工性並びに低温靭性が極めて良好となるこ
とがわかり、さらに巻取温度を下げて200℃未満
とすると、再びこれらの特性に劣化傾向がみられ
るようになるということが明らかである。また、
鋼中のP含有量も、上記の各特性に影響を与え、
その含有量が0.025%以下であれば、良好な結果
を得ることもわかる。
一方、第2図は、同様のTi添加鋼熱延材にお
ける従来の600℃巻取材(第2図a)と、これよ
りも低温の400℃で巻取つた材料(第2図b)の
光学顕微鏡組織を示したもので、両者を比較する
と、600℃巻取材はナイタル腐食を施すとフエラ
イト粒界腐食むらを起していることがわかる。
そして、これら実験結果から、つぎのような推
論がなされたのである。すなわち、
Ti添加鋼を通常の巻取温度である約600℃で
巻取ると、巻取後の徐冷中、フエライト地中に
TiCの析出が著しくなり、したがつて脆化を生
ずることとなる。また、ナイタル腐食によるフ
エライト粒界腐食むらは、フエライト粒内での
TiCの析出に伴つて粒界に存在する炭素が減少
するという、粒界浄化作用の表われと思われ
る。そして、かかる腐食むらを起しやすい鋼材
では、フエライト粒界が弱いことが知られてい
るから、上述のような鋼材の脆化と粒界脆化の
双方が原因で、鋼板のシヤーリングの時点で既
にその端面に割れを生じ、それがその後の曲げ
加工によつて大きな割れにつながるものと判断
される。
しかしながら、低温巻取りを行なえば、TiC
の析出が適当に抑制され、析出強化にかわつて
変態強化が主体となるため、600℃程度の巻取
りによつて生ずる上記欠点を回避することがで
きるものである。
また、200℃より低い温度での巻取材は、巻
取後の徐冷による自己焼なまし効果が少ないの
で、曲げ性、並びにシヤルピー特性ともに不良
となつたものと思われる。
P含有量を極力少なくすることにより、シヤ
ー端面付鋼板の曲げ性、およびシヤルピー特性
が向上する理由も、Pの存在によつて助長され
る焼戻し脆性に基づくフエライト粒界の脆化
が、Pの減少によつて抑制されたためと考えら
れる。
したがつて、この発明は、上記知見に基づい
て、特にシヤー端面付のTi添加鋼熱延素材の加
工性と低温靭性の向上とを目ざしてなされたもの
であつて、
C:0.05〜0.20%、Ti:0.04〜0.20%、
Si:1.2%以下、Mn:0.5〜2.0%、
P:0.025%以下、S:0.015%以下、
Sol.Al:0.005〜0.15%、
N:0.008%以下、
を含有するか、あるいはさらに、
Ca:0.0100%以下、
B:0.0030%以下、
Cr:1.0%以下、
のうちの1種以上を含み、
Feおよび不可避不純物:残り、
からなるキルド鋼に、900〜800℃の温度域での合
計の圧下率が30〜90%となるような熱間圧延を施
し、870〜800℃で圧延を終了した後、5〜50℃/s
ecの冷却速度で急冷を行なつてから450℃未満〜
200℃で巻取ることによつて、冷間加工性のすぐ
れたTi添加強靭性熱延高張力鋼板を得ることに
特徴を有するものである。
つぎに、この発明の熱延高張力鋼板の製造法に
おいて、鋼の成分組成範囲並びに熱延巻取条件を
上述のように限定した理由を説明する。
C
C成分には鋼の強度を確保する作用があり、
引張強さ:70Kg/mm2以上の強度を達成するため
に欠くことのできない成分であるが、その含有
量が0.05%未満では前記作用に所望の効果を得
ることができず、一方、0.20%を越えて含有せ
しめると、この発明で採用するような低温巻取
りでは高炭素含有ベイナイト組織を生ずること
となつて、曲げ性や低温靭性を劣化させるよう
になることから、その含有量を0.05〜0.20%と
定めた。
Ti
Ti成分には、TiCの析出によつて鋼を強化さ
せるほか、MnSたるA系介在物をTiSたるC系
介在物へ変化させてC曲げ性能を向上する作用
があるが、その含有量が0.04%未満では鋼材に
所望の強度を付与できないばかりでなく、介在
物形状制御も不十分となつてC曲げ性能が劣化
し、一方、0.20%を越えて含有させると本発明
の炭素含有鋼(C:0.05〜0.20%)においては
著しい析出硬化によつて低温靭性に悪影響を及
ぼすようになることから、その含有量を0.04〜
0.20%と定めた。
Si
Si成分は、固溶強化作用と脱酸作用を有して
いる。強度の増加のためには0.05%程度以上含
有されていることが好ましいけれども、1.2%
を越えて含有させると靭性および溶接性を劣化
するようになるので、その含有量を1.2%以下
と定めた。
Mn
Mn成分には鋼を強靭化する作用があり、重
要な成分であるが、その含有量が0.5%未満で
は前記作用に所望の効果を得ることができず、
一方2.0%を越えて含有させるとA系介在物が
生じやすくなつてC曲げ性能が劣化するように
なるので、その含有量を0.5〜2.0%と定めた。
P
P分は、巻取後の徐冷中にフエライト粒界に
偏析して粒界脆化を生じやすい。したがつて、
シヤー端面付の素材の曲げ性能劣化を生ずるこ
ととなるので可能な限り少ない方が良いが、経
済性の面から許容できる範囲として、その含有
量を0.025%以下と定めた。しかしながら、
0.010%以下が好ましいものである。
S
S分は、鋼中においてA系介在物を生じやす
い不純物元素であり、例えTi添加鋼であつて
もその含有量が0.015%を越えるとMnと結合し
てA系介在物を生じて曲げ性能を劣化すること
となるので、その含有量を0.015%以下と定め
た。
Sol.Al
Sol.Al成分には、添加されるTiの有効性を確
保する作用があるが、その含有量が0.005%未
満ではTi添加の効果が十分に発揮されず、一
方0.15%を越えて含有させると非金属介在物の
量が増加して鋼が脆化するようになることか
ら、その含有量を0.005〜0.15%と定めた。
N
N分は鋼中でTiNを生成し、析出硬化に有効
なTiasTiC、あるいは非金属介在物の球状化に
有効なTiasTiSの量を減少させることとなるの
で可能な限り少ない方が良い不純物元素である
が、経済性との兼ね合いで許容できる範囲とし
て、その含有量の上限を0.008%と定めた。し
かしながら、0.0050%以下が好ましい。
Ca
Ca成分は、Al2O3系のB系介在物と結合し
て、これをC系介在物として加工性を向上する
作用がある。すなわち、TiによりA系介在物
を減少させ、CaによりB系介在物をも減少で
きるため、Ti添加鋼におけるCa添加は介在物
形状制御の上で非常に好ましいものであるの
で、特に加工性をより向上する必要がある場合
に、好ましくは0.0008%以上含有させるのが望
ましい。しかし、0.0100%を越えて含有させる
と介在物が許容範囲以上に増加することとなる
ので、その含有量を0.0100%以下と定めた。
B
B成分は鋼の焼入れ性を向上し、強靭性を付
与する作用を有しており、特にこの発明の高張
力鋼板製造法のように、Ti添加鋼を低温巻取
りするという条件下では、Bの微量添加による
鋼の焼入れ性向上効果の影響は非常に大きいも
のである。したがつて、より強靭性が要求され
る場合に、好ましくは0.0001%以上含有させる
のが望ましい。しかし、0.0030%を越えて含有
させても、それ以上の向上効果が得られないこ
とから、その含有量を0.0030%以下と定めた。
Cr
Cr成分にはMnと同様に鋼を強靭化する作用
があり、鋼の強靭性をより向上せしめる必要が
ある場合に、好ましくは0.1%以上添加するの
が望ましいが、1.0%を越えて含有せしめても
それ以上の向上効果が得られないことから、そ
の含有量を1.0%以下と定めた。
熱延・巻取条件
(iv) 熱延条件
Ti添加鋼では、TiCの析出硬化と、粗大な
TiNの存在によつて低温靭性が劣化するの
で、この対策として900℃以下での合計30〜
90%の圧下を行ない、870〜800℃で圧延を終
了するという制御圧延を実施する必要があ
る。この場合、870℃を越えた高い圧延終了
温度あるいは900〜800℃の温度域での合計圧
下率が30未満では、目的とする十分な細粒組
織が得られず、構造物素材として必要な低温
靭性を確保するのが困難となり、したがつて
圧下率は大きければ大きいほどよいが、90%
を越えた圧下率になると圧延機能力に制約を
受けるようになる。一方、800℃未満の温度
で圧延を終了すると、集合組織が発達して異
方性が生じるばかりでなく、C曲げ性を劣化
するようになるので、900〜800℃の温度域で
の合計の圧下率を30〜90%、圧延終了温度を
870〜800℃と定めた。
(ii) 熱延後、巻取りまでの冷却速度
制御圧延後から巻取りまでの冷却速度が5
℃/sec未満の徐冷では、変態強化作用がほと
んど生ぜず、所望の高強度を得ることが困難
となる。したがつて冷却速度は速ければ速い
ほどよいが、50℃/secを越えた冷却速度は実
操業上困難性を伴うようになることから、そ
の冷却速度を5〜50℃/secと定めた。
(iii) 巻取温度
前述のように、巻取温度が450℃以上の場
合には、シヤー端面付素材の曲げ性、および
シヤルピー破面遷移温度の劣化が著しくな
り、一方200℃未満となつた場合にも、やは
り該特性に劣化傾向が現われてくることか
ら、巻取温度を450未満〜200℃と定めた。
ついで、この発明を実施例により比較例と対比
しながら説明する。
実施例
まず、第1表に示したような化学成分組成を有
する本発明方法に使用する鋼の化学成分組成範囲
This invention has a high tensile strength of 70Kg/mm 2 or more, and has excellent workability and low-temperature toughness.
This paper relates to a method for producing Ti-added hot-rolled high-strength steel sheets. In recent years, there has been an increasing demand for steel materials with high strength and excellent workability as structural materials for various buildings and industrial machinery, and various steel materials have been developed and used to meet these demands. I'm getting used to it.
Examples include Nb-added steel, V-added steel, and Ti-added steel. Among these, Ti-added steel is attracting attention because it is cheap to manufacture and can provide high strength, but it has the problem that its toughness is inferior to Nb-added steel and V-added steel. . However, recently, due to the deterioration of the energy situation, it has become unavoidable to develop resources in extremely harsh environments.
In the case of the above-mentioned high-strength steel plates, if they are plastically deformed by cold working and used in cold regions, there is a risk of brittle fracture occurring at the plastically deformed parts. In addition to these properties, there was a strong demand for high-strength steel sheets that also had excellent low-temperature toughness so that they could withstand use in cold regions. Therefore, in order to provide a high-strength steel plate that satisfies these demands, a method of hot controlled rolling of Ti-added steel was proposed, as described in Japanese Patent Publication No. 1983-45614. The feature of Ti-added hot-rolled high-strength steel sheet is that it utilizes the precipitation strengthening of TiC, and at the same time replaces MnS, which is an A-based inclusion, with TiS to create a C-based inclusion, which improves workability. In addition to having high strength, it also has excellent cold workability, as it was possible to perform close bending in a JIS standard bending test using specimens with machined edges. It is said that The method described in the above-mentioned Japanese Patent Publication No. 55-45614 further improves the low-temperature toughness by performing controlled rolling during the production of Ti-added hot-rolled high-strength steel sheets having such characteristics. This is an improvement. By the way, in the bending test according to the JIS standard, as mentioned above, a material with a machined end surface is used as a test material, but in actual production of structural members, a material with a shear end surface (the shear cut surface is machined) is used. In most cases, cold-working steel sheets are subjected to cold working as they are. Therefore, from a practical standpoint, cold-working steel sheets are required to have good bending performance in specimens with sheared edges. The Rukoto. However, there are many Ti
It became clear at the subsequent stage of practical application that hot-rolled steel sheets with additives generally had poor bending test performance with shear end faces, and had serious problems such as cracking at the end faces during bending. Ta. From the above-mentioned viewpoints, the present inventor has found that the material not only has high tensile strength of 70 kg/mm 2 or more, excellent workability and low-temperature toughness, but also has good workability, especially for materials with shear end faces. As a result of intensive research in order to obtain high-strength steel sheets, we found that a specific composition of
After controlled rolling of Ti-added steel, if it is rolled at a low temperature of approximately 400°C, which breaks conventional wisdom, the tensile strength can be increased to 70°C.
It has been found that a high tensile strength steel plate with a high value of Kg/mm 2 or more, improved bending cracking of a steel plate with a shear end face, and excellent low-temperature toughness can be obtained. Based on this, we continued further research, and the following (a)
We have come to the knowledge shown in ~(c). In other words, (a) When producing a Ti-added hot rolled steel sheet with high strength, after hot rolling, the temperature is approximately
When coiled at 600℃, it is true that it is possible to bend closely within the JIS standard bending range, and it has excellent workability.
When bending a material with a shear end surface, it is difficult to avoid bending cracks due to the brittleness of the ferrite grain boundaries, and the low-temperature toughness also deteriorates due to the precipitation of TiC. However, when the winding temperature is controlled within the range of less than 450℃ to 200℃,
As mentioned above, precipitation of TiC is suppressed and transformation strengthening is performed, suppressing embrittlement of ferrite grain boundaries, and not only does the bending performance of the shear end face improve significantly, but also the shear pie fracture transition temperature is improved. In particular, at temperatures below 900°C, a total of 30
(b) By combining this with controlled rolling in which a reduction of ~90% is performed and rolling is completed at a temperature of 870 to 800°C, a high-strength steel plate with an extremely improved Shalpy fracture transition temperature can be obtained; In addition, if the P content in the Ti-added steel is reduced, each of the properties described in item (a) above will be further improved. (c) One of Ca, B, and Cr may be added to the Ti-added steel. By containing a specific amount of a species or two or more species, further improvement in workability and toughness can be achieved. In order to obtain these findings, the present inventor established a hot rolling simulation experimental method to investigate the effect of coiling temperature on the mechanical properties of Ti-added steel, and repeated various experiments. Needless to say. This hot rolling simulation experimental method involves rapidly cooling the steel material by water spray to a predetermined temperature after rolling, and then putting the rolled material into a furnace whose temperature has been raised to the predetermined temperature and cooling it in the furnace (cooling rate: 20℃/hr)
This is a method of doing this. It was also confirmed that if the "predetermined temperature" at this time was made to match the coiling temperature, a steel plate having the same structure and characteristics as in actual hot rolling and coiling operations could be obtained. Figure 1 shows the results of investigating the effect of coiling temperature on the mechanical properties of Ti-added steel under controlled rolling with a finish of 820°C using such a hot rolling simulation experimental method. Figure 1 shows 0.10%C-0.30%Si-1.65%Mn-
0.002%S - 0.17%Ti - 0.025%Al - 0.0035%N steel (Hereinafter, percentages indicating component composition ratios are weight%)
Apply a 50% reduction at a temperature below 900℃, finishing temperature:
A line showing the effect of the coiling temperature on the mechanical properties of the steel plate when a 6 mm thick hot rolled steel plate is obtained at 820℃ and then cooled at a cooling rate of 10℃/sec, which corresponds to the coiling cooling rate. It is a diagram. From Figure 1, the winding temperature is
When the temperature exceeds 400℃, the deterioration of the bendability of the sheet material with shear edges and the transition temperature of the shear pie fracture surface becomes noticeable, and especially when the temperature exceeds 500℃, the deterioration tendency becomes extreme to the extent that it is not practical. It was found that workability and low-temperature toughness were extremely good when the coiling temperature was in the range of less than 450°C to 200°C, and when the coiling temperature was further lowered to less than 200°C, there was a tendency for these properties to deteriorate again. It is clear that Also,
The P content in steel also affects each of the above properties,
It can also be seen that good results can be obtained if the content is 0.025% or less. On the other hand, Figure 2 shows the optical properties of a conventional Ti-added hot-rolled steel material rolled at 600℃ (Figure 2a) and a material rolled at a lower temperature of 400℃ (Figure 2b). This shows the microscopic structure. Comparing the two, it can be seen that when the 600℃ rolled material is subjected to nital corrosion, uneven ferrite grain boundary corrosion occurs. From these experimental results, the following inferences were made. In other words, when Ti-added steel is coiled at the normal coiling temperature of approximately 600℃, during the slow cooling after coiling, ferrite is deposited in the ground.
TiC precipitation becomes significant, resulting in embrittlement. In addition, uneven ferrite grain boundary corrosion due to nital corrosion occurs within the ferrite grains.
This seems to be an expression of the grain boundary purification effect, in which carbon present at grain boundaries decreases as TiC precipitates. It is known that steel materials that are prone to such uneven corrosion have weak ferrite grain boundaries, so both the embrittlement of the steel material and the grain boundary embrittlement described above cause the steel sheet to undergo shearing. It is judged that cracks have already formed on the end face, and that this will lead to large cracks due to subsequent bending. However, if low-temperature winding is performed, TiC
Since the precipitation of is appropriately suppressed and transformation strengthening takes place instead of precipitation strengthening, the above-mentioned drawbacks caused by winding at about 600°C can be avoided. In addition, it is thought that the material rolled at a temperature lower than 200° C. has poor self-annealing effect due to slow cooling after winding, resulting in poor bendability and sharpie properties. The reason why the bendability and shear strength properties of steel sheets with shear edges are improved by reducing the P content as much as possible is that the embrittlement of ferrite grain boundaries due to tempering embrittlement promoted by the presence of P This is thought to be because it was suppressed by the decrease. Therefore, the present invention was made based on the above findings, with the aim of improving the workability and low-temperature toughness of Ti-added hot-rolled steel materials with shear end faces, and in which C: 0.05 to 0.20%. , Ti: 0.04-0.20%, Si: 1.2% or less, Mn: 0.5-2.0%, P: 0.025% or less, S: 0.015% or less, Sol.Al: 0.005-0.15%, N: 0.008% or less. Or, in addition, Ca: 0.0100% or less, B: 0.0030% or less, Cr: 1.0% or less, containing one or more of the following, Fe and unavoidable impurities: the remainder, and the killed steel is heated at 900 to 800°C. After hot rolling with a total rolling reduction of 30 to 90% in the temperature range of 870 to 800℃, 5 to 50℃/s
Below 450℃ after rapid cooling at EC cooling rate
By coiling at 200°C, a Ti-added strong hot-rolled high-strength steel sheet with excellent cold workability is obtained. Next, in the method for producing a hot-rolled high-strength steel sheet of the present invention, the reason why the composition range of the steel and the hot-rolling winding conditions are limited as described above will be explained. C The C component has the effect of ensuring the strength of steel,
Tensile strength: It is an essential component to achieve a strength of 70 Kg/mm 2 or more, but if its content is less than 0.05%, the desired effect cannot be obtained; on the other hand, 0.20% If the content exceeds 0.05, a high carbon-containing bainite structure will occur in low-temperature winding as employed in this invention, deteriorating bendability and low-temperature toughness. It was set at 0.20%. Ti The Ti component has the effect of strengthening steel by precipitating TiC and improving C bending performance by changing A-based inclusions such as MnS to C-based inclusions such as TiS. If the content is less than 0.04%, not only will it not be possible to impart the desired strength to the steel material, but the control of the shape of inclusions will also be insufficient, resulting in poor C bending performance.On the other hand, if the content exceeds 0.20%, the carbon-containing steel of the present invention ( C: 0.05 to 0.20%) causes significant precipitation hardening, which adversely affects low-temperature toughness;
It was set at 0.20%. Si The Si component has a solid solution strengthening effect and a deoxidizing effect. Although it is preferable to contain about 0.05% or more to increase strength, 1.2%
If the content exceeds 1.2%, the toughness and weldability will deteriorate, so the content was set at 1.2% or less. Mn The Mn component has the effect of toughening steel and is an important component, but if its content is less than 0.5%, the desired effect cannot be obtained.
On the other hand, if the content exceeds 2.0%, A-based inclusions tend to occur and the C bending performance deteriorates, so the content was set at 0.5 to 2.0%. P The P component tends to segregate at ferrite grain boundaries during slow cooling after winding and cause grain boundary embrittlement. Therefore,
Since it causes deterioration in the bending performance of the material with the shear end surface, it is better to have as little as possible, but from an economic point of view, the content is set at 0.025% or less as an allowable range. however,
The content is preferably 0.010% or less. S S is an impurity element that tends to form A-based inclusions in steel, and even in Ti-added steel, if its content exceeds 0.015%, it will combine with Mn to form A-based inclusions and cause bending. Since this would degrade performance, its content was set at 0.015% or less. Sol.Al The Sol.Al component has the effect of ensuring the effectiveness of added Ti, but if the content is less than 0.005%, the effect of Ti addition will not be fully exhibited, while if the content exceeds 0.15% If it is included, the amount of nonmetallic inclusions will increase and the steel will become brittle, so the content was set at 0.005 to 0.15%. N N is an impurity element that generates TiN in steel and reduces the amount of TiasTiC, which is effective for precipitation hardening, or TiasTiS, which is effective for spheroidizing nonmetallic inclusions, so it is better to minimize it as much as possible. However, the upper limit of its content has been set at 0.008% as an allowable range considering economic efficiency. However, it is preferably 0.0050% or less. Ca The Ca component has the effect of combining with Al 2 O 3 -based B-based inclusions and converting them into C-based inclusions to improve workability. In other words, since Ti can reduce A-based inclusions and Ca can also reduce B-based inclusions, the addition of Ca in Ti-added steel is very favorable for controlling the shape of inclusions, so it is particularly effective for improving workability. If further improvement is required, it is desirable to contain 0.0008% or more. However, if the content exceeds 0.0100%, the number of inclusions will increase beyond the allowable range, so the content was set at 0.0100% or less. B The B component has the effect of improving the hardenability of steel and imparting toughness, especially under the condition that Ti-added steel is coiled at a low temperature as in the high-strength steel plate manufacturing method of this invention. The effect of improving the hardenability of steel by adding a small amount of B is very large. Therefore, when higher toughness is required, it is desirable to contain 0.0001% or more. However, even if the content exceeds 0.0030%, no further improvement effect can be obtained, so the content was set at 0.0030% or less. Cr Similar to Mn, the Cr component has the effect of toughening steel, and when it is necessary to further improve the toughness of steel, it is desirable to add 0.1% or more, but it is not recommended to add more than 1.0%. Since no further improvement effect could be obtained even if the content was reduced to 1.0% or less, the content was set at 1.0% or less. Hot rolling/coiling conditions (iv) Hot rolling conditions In Ti-added steel, precipitation hardening of TiC and coarse
Since the presence of TiN deteriorates low-temperature toughness, as a countermeasure, the total
It is necessary to carry out controlled rolling in which rolling is completed at 870 to 800°C with a reduction of 90%. In this case, if the finishing temperature of rolling exceeds 870°C or the total rolling reduction rate is less than 30 in the temperature range of 900 to 800°C, the desired fine grain structure cannot be obtained, and the low temperature required as a structural material cannot be obtained. It becomes difficult to ensure toughness, so the higher the reduction rate, the better, but 90%
When the rolling reduction exceeds , the rolling capacity becomes constrained. On the other hand, if rolling is finished at a temperature below 800℃, the texture will develop and anisotropy will occur, as well as deterioration of C bendability, so the total The rolling reduction rate is 30-90%, and the rolling end temperature is
The temperature was set at 870-800℃. (ii) Cooling rate after hot rolling until coiling The cooling rate after controlled rolling until coiling is 5
If the temperature is lower than ℃/sec, almost no transformation strengthening effect occurs, making it difficult to obtain the desired high strength. Therefore, the faster the cooling rate, the better; however, since a cooling rate exceeding 50°C/sec would be difficult in actual operation, the cooling rate was set at 5 to 50°C/sec. (iii) Coiling temperature As mentioned above, when the coiling temperature is 450℃ or higher, the bendability of the material with shear end faces and the shear pie fracture surface transition temperature deteriorate significantly, whereas when the coiling temperature is lower than 200℃. In this case, the characteristics also tend to deteriorate, so the winding temperature was set at less than 450°C to 200°C. Next, the present invention will be explained using examples and comparing with comparative examples. Example First, the chemical composition range of steel used in the method of the present invention having the chemical composition shown in Table 1
【表】【table】
【表】【table】
【表】
を満足する鋼A〜Hと、いずれかの化学成分の組
成範囲が本発明対象鋼のそれから外れている比較
鋼I〜S(組成範囲を外れた成分には※印を付し
てある)を、通常の溶解・鋳造法によつて作成し
た。
つぎに、これらの鋼材を、第2表に示した各条
件にて熱間圧延し、巻取つて、厚さ:6mmの熱延
鋼板を製造した。なお、第2表における※印は、
いずれも本発明において定めた範囲から外れた条
件を示すものである。
さらに、このようにして得られた熱延鋼板の機
械的性質を測定し、得られた結果を第2表に併せ
て記載した。
第2表に示される結果からも、使用鋼材の化学
成分組成範囲、および熱延・巻取りの条件が本発
明で定めた範囲である試験番号1〜13の方法で得
られた熱延鋼板は、いずれも高強度を有するとと
もに、すぐれた低温靭性並びにシヤー端面付曲げ
性能を有していることが明らかであり、他方、鋼
材の化学成分組成、および熱延・巻取りの条件が
本発明で定めた範囲から外れている試験番号14〜
27の方法で得られた熱延鋼板は、低温靭性やシヤ
ー端面付曲げ性能に劣つていることがわかる。特
に、試験番号14の比較例のように、制御圧延を行
なわずに、単に低温巻取のみを行なうと、得られ
る鋼板の組織は第2図bに示すような、少量の細
粒フエライトと微細ベイナイト組織の混合組織と
はならず、すべて粗大なベイナイト組織となつて
大幅な靭性劣化を生ずることもわかつた。なお、
巻取温度が本発明の範囲から外れた場合の実験結
果は、前述の第1図に示したとおり、良好なもの
でなかつたことはいうまでもない。
また、Caを添加した第1表中のD鋼、F鋼、
G鋼およびH鋼では、曲げ性能が極めて向上して
いることが確認された。
このように、特定の化学成分組成のTi添加鋼
に、所定の制御圧延と低温巻取りとを組合せて施
すことにより、少量の細粒フエライトと微細ベイ
ナイト組織の混合組織(細粒フエライトによりベ
イナイト組織が分断されている)が得られ、した
がつて強靭性が確保できるとともに、加工性にも
すぐれた特性が呈せられるのである。
上述のように、この発明によれば、格別な後処
理を施すことなく、引張強さが70Kg/mm2以上の高
強度と、シヤー端面付素材であつても割れを生ず
ることなく良好に冷間加工し得るすぐれた加工性
と、これに加えて極めてすぐれた低温靭性とを兼
ね備えた熱延高張力鋼板を、比較的簡単な手段に
て得ることができ、寒冷地その他で使用する建造
物や産業機械等の構造材に適用することによつて
これまで以上の成果を挙げることが期待できるな
ど、工業上有用な効果がもたらされるのである。[Table] Steels A to H that satisfy the following, and comparative steels I to S in which the composition range of any chemical component deviates from that of the steel subject to the present invention (components that are outside the composition range are marked with *) ) was made using the usual melting and casting method. Next, these steel materials were hot-rolled under the conditions shown in Table 2, and wound to produce hot-rolled steel sheets having a thickness of 6 mm. In addition, the * mark in Table 2 is
All of these conditions are outside the range defined in the present invention. Furthermore, the mechanical properties of the hot rolled steel sheet thus obtained were measured, and the obtained results are also listed in Table 2. From the results shown in Table 2, the hot-rolled steel sheets obtained by the methods of test numbers 1 to 13, in which the chemical composition range of the steel used and the hot-rolling/coiling conditions are within the range specified by the present invention, are It is clear that all of them have high strength, excellent low-temperature toughness and shear end face bending performance, and on the other hand, the chemical composition of the steel material and the conditions of hot rolling and winding are Test number 14 ~ which is outside the specified range
It can be seen that the hot-rolled steel sheet obtained by method 27 is inferior in low-temperature toughness and shear end face bending performance. In particular, when only low-temperature coiling is performed without controlled rolling, as in the comparative example of test number 14, the structure of the obtained steel sheet is as shown in Figure 2b, with a small amount of fine-grained ferrite and fine particles. It was also found that the structure did not become a mixed structure of bainite structure, but instead became a coarse bainite structure, resulting in a significant deterioration of toughness. In addition,
Needless to say, the experimental results when the winding temperature was outside the range of the present invention were not good, as shown in FIG. 1 above. In addition, D steel, F steel in Table 1 with Ca added,
It was confirmed that the bending performance of G steel and H steel was extremely improved. In this way, by subjecting Ti-added steel with a specific chemical composition to a combination of predetermined controlled rolling and low-temperature coiling, a mixed structure of a small amount of fine-grained ferrite and a fine bainite structure (a bainite structure due to fine-grained ferrite) Therefore, not only can toughness be ensured, but also excellent workability can be obtained. As mentioned above, according to the present invention, it is possible to achieve high tensile strength of 70 kg/mm 2 or more without any special post-treatment, and to cool well without cracking even when the material has a shear end surface. Hot-rolled high-strength steel sheets that have excellent workability and extremely low-temperature toughness can be obtained by relatively simple means, making them ideal for buildings used in cold regions and other areas. By applying it to the structural materials of industrial machinery, etc., it can be expected to achieve better results than ever before, and will bring about industrially useful effects.
第1図はTi添加鋼の機械的性質に及ぼす巻取
温度の影響を示した線図、第2図aはTi添加鋼
を制御圧延した後600℃で巻取つた鋼板のナイタ
ル腐食による光学顕微鏡組織図、第2図bは400
℃で巻取つた同様の鋼板のナイタル腐食による光
学顕微鏡組織図である。
Figure 1 is a diagram showing the effect of coiling temperature on the mechanical properties of Ti-added steel, and Figure 2-a is an optical microscope showing nital corrosion of a steel plate rolled at 600℃ after controlled rolling of Ti-added steel. Organization chart, Figure 2b is 400
FIG. 2 is an optical microscopic microstructure diagram of a similar steel plate coiled at ℃ due to nital corrosion.
Claims (1)
らなる組成(以上重量%)を有するキルド鋼に、 900〜800℃の温度域での合計の圧下率が30〜90
%の条件で熱間圧延を施し、870〜800℃の温度で
圧延を終了した後、5〜50℃/secの冷却速度で急
冷し、450℃未満〜200℃の温度で巻取ることを特
徴とする冷間加工性のすぐれたTi添加強靭性熱
延高張力鋼板の製造法。 2 C:0.05〜0.2%、 Ti:0.04〜0.2%、 Si:1.2%以下、 Mn:0.5〜2%、 P:0.025%以下、 S:0.015%以下、 Sol.Al:0.005〜0.15%、 N:0.008%以下、 を含有し、さらに、 Ca:0.01%以下、 B:0.003%以下、 Cr:1%以下、 のうちの1種以上を含有し、残りがFeとその他
の不可避不純物からなる組成(以上重量%)を有
するキルド鋼に、 900〜800℃の温度域での合計の圧下率が30〜90
%の条件で熱間圧延を施し、870〜800℃の温度で
圧延を終了した後、5〜50℃/secの冷却速度で急
冷し、450℃未満〜200℃の温度で巻取ることを特
徴とする冷間加工性のすぐれたTi添加強靭性熱
延高張力鋼板の製造法。[Claims] 1 C: 0.05-0.2%, Ti: 0.04-0.2%, Si: 1.2% or less, Mn: 0.5-2%, P: 0.025% or less, S: 0.015% or less, Sol.Al: 0.005 to 0.15%, N: 0.008% or less, and the remainder consists of Fe and other unavoidable impurities (weight%), the total rolling reduction rate in the temperature range of 900 to 800℃ is 30~90
% conditions, and after finishing the rolling at a temperature of 870 to 800°C, it is rapidly cooled at a cooling rate of 5 to 50°C/sec, and coiled at a temperature of less than 450°C to 200°C. A method for producing Ti-added strong hot-rolled high-strength steel sheets with excellent cold workability. 2 C: 0.05-0.2%, Ti: 0.04-0.2%, Si: 1.2% or less, Mn: 0.5-2%, P: 0.025% or less, S: 0.015% or less, Sol.Al: 0.005-0.15%, N : 0.008% or less, and further contains one or more of the following: Ca: 0.01% or less, B: 0.003% or less, Cr: 1% or less, with the remainder consisting of Fe and other unavoidable impurities. (more than weight%), the total rolling reduction in the temperature range of 900-800℃ is 30-90
% conditions, and after finishing the rolling at a temperature of 870 to 800°C, it is rapidly cooled at a cooling rate of 5 to 50°C/sec, and coiled at a temperature of less than 450°C to 200°C. A method for producing Ti-added strong hot-rolled high-strength steel sheets with excellent cold workability.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11135182A JPS591632A (en) | 1982-06-28 | 1982-06-28 | Manufacture of hot-rolled high-tension steel sheet with superior workability |
US06/507,009 US4472208A (en) | 1982-06-28 | 1983-06-23 | Hot-rolled high tensile titanium steel plates and production thereof |
GB08317181A GB2122644B (en) | 1982-06-28 | 1983-06-24 | Hot-rolled high tensile titanium steel plates and production thereof |
DE19833323255 DE3323255A1 (en) | 1982-06-28 | 1983-06-28 | HOT-ROLLED, HIGH-STRENGTH TITANIUM STEEL SHEET AND METHOD FOR THE PRODUCTION THEREOF |
FR8310696A FR2529231B1 (en) | 1982-06-28 | 1983-06-28 | HOT ROLLED TITANIUM STEEL SHEETS WITH HIGH TENSILE STRENGTH AND THEIR MANUFACTURING METHOD |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11135182A JPS591632A (en) | 1982-06-28 | 1982-06-28 | Manufacture of hot-rolled high-tension steel sheet with superior workability |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS591632A JPS591632A (en) | 1984-01-07 |
JPS624450B2 true JPS624450B2 (en) | 1987-01-30 |
Family
ID=14558988
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP11135182A Granted JPS591632A (en) | 1982-06-28 | 1982-06-28 | Manufacture of hot-rolled high-tension steel sheet with superior workability |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS591632A (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60204826A (en) * | 1984-03-29 | 1985-10-16 | Sumitomo Metal Ind Ltd | Production of ti high tensile steel having excellent low- temperature toughness |
JPS61106715A (en) * | 1984-10-29 | 1986-05-24 | Sumitomo Metal Ind Ltd | Manufacture of steel plate having superior carburizing property |
JPS61157628A (en) * | 1984-12-28 | 1986-07-17 | Nippon Steel Corp | Manufacture of hot coil for high-toughness sour-resistant steel pipe |
KR101103203B1 (en) | 2008-03-26 | 2012-01-05 | 신닛뽄세이테쯔 카부시키카이샤 | Hot rolled steel sheet possessing excellent fatigue properties and stretch-flange ability and process for producing the hot rolled steel sheet |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5675520A (en) * | 1979-11-20 | 1981-06-22 | Kobe Steel Ltd | Manufacture of high yield ratio type nonskin-pass hot rolled high tensile steel plate |
-
1982
- 1982-06-28 JP JP11135182A patent/JPS591632A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5675520A (en) * | 1979-11-20 | 1981-06-22 | Kobe Steel Ltd | Manufacture of high yield ratio type nonskin-pass hot rolled high tensile steel plate |
Also Published As
Publication number | Publication date |
---|---|
JPS591632A (en) | 1984-01-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CN104928569B (en) | A kind of low density steel of 800MPa level high ductibility and its manufacture method | |
JPH11140582A (en) | High toughness thick steel plate excellent in toughness in weld heat-affected zone, and its production | |
US20160160330A1 (en) | Superstrength cold rolled weathering steel sheet and method of manufacturing same | |
JP2987815B2 (en) | Method for producing high-tensile cold-rolled steel sheet excellent in press formability and secondary work cracking resistance | |
JP3280692B2 (en) | Manufacturing method of high strength cold rolled steel sheet for deep drawing | |
JPS624450B2 (en) | ||
CN111349848B (en) | Corrosion-inhibiting high-strength aluminum-coated substrate steel and manufacturing method thereof | |
CN111349769B (en) | Corrosion-inhibiting steel for aluminum-clad substrate and manufacturing method thereof | |
JPS63241120A (en) | Manufacture of high ductility and high strength steel sheet having composite structure | |
JP2990214B2 (en) | Alloyed molten Zn-plated steel sheet of ultra-low C-base thin hot rolled sheet excellent in workability and method for producing the same | |
JPH07150247A (en) | Production of steel tube with high strength and low yield ratio for construction use | |
KR20200075957A (en) | Steel sheet having excellent workability and balance of strength and ductility, and method for manufacturing the same | |
CN111349869A (en) | Steel for high-strength aluminum-coated substrate and manufacturing method thereof | |
KR100435467B1 (en) | A method for manufacturing high strength cold rolled steel sheet having superior ductility by continuous annealing | |
CN115323261B (en) | Steel plate for quenched and tempered acid-resistant pipeline and manufacturing method thereof | |
JP3175063B2 (en) | Ferrite single-phase cold-rolled steel sheet for non-aging deep drawing at room temperature and method for producing the same | |
JPS6366367B2 (en) | ||
JPH09137232A (en) | Production of high tensile strength hot rolled steel plate | |
JPS6338518A (en) | Production of steel plate having excellent hydrogen induced cracking resistance | |
JPS61257421A (en) | Production of extra-high tensile steel plate | |
JPS6350424A (en) | Manufacture of thick high-tensile steel plate excellent in toughness at low temperature and weldability | |
JP3150188B2 (en) | Method for manufacturing high-strength cold-rolled steel sheet with excellent deep drawability | |
JPH0892656A (en) | Production of cold rolled steel sheet excellent in deep drawability | |
KR101433446B1 (en) | Method for manufacturing hot-rolled steel having excellent corrosion resistance and anti-fluting and the hot-rolled steel by the same method | |
JPS60204828A (en) | Manufacture of tough and hard hot rolled steel strip having separation resistance |