JP2005513271A6 - High-strength cold-rolled steel sheet excellent in formability and weldability and its manufacturing method - Google Patents
High-strength cold-rolled steel sheet excellent in formability and weldability and its manufacturing method Download PDFInfo
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- 239000010960 cold rolled steel Substances 0.000 title claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 75
- 239000010959 steel Substances 0.000 claims abstract description 75
- 238000000137 annealing Methods 0.000 claims abstract description 40
- 238000001816 cooling Methods 0.000 claims abstract description 15
- 238000005097 cold rolling Methods 0.000 claims abstract description 13
- 239000000203 mixture Substances 0.000 claims abstract description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 238000005098 hot rolling Methods 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- 238000005279 austempering Methods 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 2
- 238000005496 tempering Methods 0.000 abstract description 9
- 238000010521 absorption reaction Methods 0.000 abstract description 5
- 229910001566 austenite Inorganic materials 0.000 description 58
- 230000000717 retained Effects 0.000 description 27
- 230000001131 transforming Effects 0.000 description 21
- 239000002244 precipitate Substances 0.000 description 17
- 229910017083 AlN Inorganic materials 0.000 description 12
- PIGFYZPCRLYGLF-UHFFFAOYSA-N aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 10
- 238000005755 formation reaction Methods 0.000 description 10
- 229910000529 magnetic ferrite Inorganic materials 0.000 description 10
- 238000000034 method Methods 0.000 description 10
- 229910000859 α-Fe Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 229910000734 martensite Inorganic materials 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 229910001562 pearlite Inorganic materials 0.000 description 7
- 150000001247 metal acetylides Chemical class 0.000 description 6
- 230000002829 reduced Effects 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 238000005482 strain hardening Methods 0.000 description 4
- 230000001629 suppression Effects 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 238000010587 phase diagram Methods 0.000 description 3
- 238000003303 reheating Methods 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- 229910019802 NbC Inorganic materials 0.000 description 2
- 229910034327 TiC Inorganic materials 0.000 description 2
- 230000003247 decreasing Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000004881 precipitation hardening Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching Effects 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 230000000087 stabilizing Effects 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- 229910006639 Si—Mn Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
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Abstract
本発明は、自動車用構造用部品に使用される場合、成形が容易になりながら自動車衝突時エネルギー吸収性に優れ自動車の安定性を向上させられる引張強度70〜90kgf/mm2級の高強度冷延鋼板とその製造方法に関するものである。
本発明は、重量%でC:0.15〜0.25%、Si:0.5〜1.5%、Mn:1.0〜2.0%、P:0.25%以下、S:0.020%以下、Al:0.015〜0.050%、N:0.008〜0.026%、残部Fe及び不可避な不純物を含み、1.2≦Si[%]+50/8 P[%]≦2.0を満足するよう組成される成形性及び溶接性の優れた高強度冷延鋼板と、
前記のように組成された鋼を通常の方法で熱間圧延した後、冷間圧延して冷間圧延板を製造する段階;前記冷間圧延処理された鋼板を下記関係式の範囲の温度において連続焼鈍する段階;及び
[関係式]
563+651C[%]+42Si[%]+18Mn[%]≦焼鈍温度 [℃]≦850℃
前記連続焼鈍された鋼板を20〜100℃/sの冷却速度でオステンパリング開始温度400〜450℃まで急冷してから350〜400℃まで冷却する段階;を含む成形性及び溶接性の優れた高強度冷延鋼板の製造方法に関するものである。The present invention, when used for structural parts for automobiles, has high tensile strength of 70 to 90 kgf / mm 2 class high tensile strength, which is excellent in energy absorption at the time of automobile collision and improves the stability of automobiles while being easy to mold. The present invention relates to a rolled steel sheet and a manufacturing method thereof.
The present invention, by weight, C: 0.15-0.25%, Si: 0.5-1.5%, Mn: 1.0-2.0%, P: 0.25% or less, S: 0.020% or less, Al: 0.015-0.050%, N: 0.008 A high strength cold-rolled steel sheet having excellent formability and weldability, which is composed to satisfy-≦ 0.026%, balance Fe and inevitable impurities, and satisfying 1.2 ≦ Si [%] + 50/8 P [%] ≦ 2.0 ,
Hot-rolling the steel having the above composition by a normal method, and then cold-rolling to produce a cold-rolled sheet; the cold-rolled steel sheet at a temperature within the range of the following relational expression: Continuous annealing stage; and
[Relational expression]
563 + 651C [%] + 42Si [%] + 18Mn [%] ≦ Annealing temperature [℃] ≦ 850 ℃
A step of rapidly cooling the continuously annealed steel sheet to a male tempering start temperature of 400 to 450 ° C. at a cooling rate of 20 to 100 ° C./s and then cooling to 350 to 400 ° C .; The present invention relates to a method for producing a strength cold-rolled steel sheet.
Description
本発明は、自動車の構造用部品に用いられる高強度冷延鋼板の製造方法に関するもので、より詳しくは、70〜90kgf/mm2級の引張強度を提供すると共に、成形が容易で自動車衝突時エネルギー吸収性に優れ、自動車の安定性を向上できる高強度冷延鋼板及びその製造方法に関するものである。 The present invention relates to a method for producing a high strength cold rolled steel sheet used for structural components of an automobile, and more particularly, with providing 70~90kgf / mm 2 class tensile strength, when an automobile collision is easily molded The present invention relates to a high-strength cold-rolled steel sheet that is excellent in energy absorption and can improve the stability of an automobile, and a method for producing the same.
近年環境が社会的に重要な問題として取上げられながら、世界中で自動車排ガス及び燃費の規制が強化されてきている。また、衝突安定性に対する規制も強化され続けており、これに応じて世界各国の自動車メーカーは軽量且つ衝突安全性の優れた自動車を開発している。さらに、自動車の増加と共に自動車事故の頻度が高まり、乗客の安全も強調される。しかし、自動車を軽量に製造しながら衝突安全性を向上させるためには、強度の高い材料を使って自動車を製造しなければならない。 In recent years, regulations on automobile exhaust gas and fuel consumption have been strengthened around the world, while the environment has been taken up as an important social issue. In addition, regulations on collision stability continue to be strengthened, and in response to this, automobile manufacturers around the world are developing cars that are lightweight and have excellent collision safety. Furthermore, with the increase in the number of cars, the frequency of car accidents increases, and passenger safety is emphasized. However, in order to improve collision safety while manufacturing a lightweight vehicle, the vehicle must be manufactured using a material having high strength.
自動車衝突安定性に対する規制が強化されながら、従来の正面衝突、側面衝突の評価と共に従来の正面衝突に対して厳格な基準のオフセット衝突評価試験が追加された。また、自動車安定性においてバンパーのエネルギー吸収性が重要である為、バンパーのエネルギー吸収性を高めるべく自動車部品材料の強度が増加される実状にある。 While regulations on automobile crash stability have been strengthened, a strict standard offset crash assessment test has been added to the conventional crashes along with the assessment of conventional crashes and side impacts. Further, since the energy absorption of the bumper is important in the stability of the automobile, the strength of the automobile part material is increased in order to increase the energy absorption of the bumper.
従来の高強度冷延鋼板の製造技術は、[1]加工硬化鋼、[2]複合組織鋼、[3]加工誘起変態鋼に区分することができる。 Conventional manufacturing techniques for high-strength cold-rolled steel sheets can be divided into [1] work-hardened steel, [2] composite structure steel, and [3] work-induced transformation steel.
[1]加工硬化鋼
冷間圧延による加工硬化を利用する方法として、冷間圧延後回復焼鈍を施し未再結晶素子に強度を増加させるので、添加合金量が少なく溶接性に優れるとの利点がある。しかし、延伸率が低いので成形性が良くない。
[1] Work hardening steel As a method of using work hardening by cold rolling, recovery annealing after cold rolling is performed to increase the strength of the non-recrystallized element, so there is an advantage that the amount of added alloy is small and weldability is excellent. is there. However, since the stretch ratio is low, the moldability is not good.
[2]複合組織鋼
冷間圧延後焼鈍温度をA1変態点以上に加熱しオーステナイトを形成した後、急冷によりオーステナイトをマルテンサイトやベイナイトに変態させて材料の強度を増加させた複合組織鋼がある。しかし、こうした鋼は、熱処理工において冷却速度が速くなければならないので、製造が困難で延伸率が低い欠点があり、その一例として日本特開平6-271942号公報、特開平7-090488号公報が挙げられる。
[2] After the composite structure steel cold rolling after annealing temperature to form austenite heated above the A 1 transformation point, by transformation of the austenite to martensite or bainite material strength composite structure steel increased in the rapid cooling is there. However, these steels have a drawback that they are difficult to manufacture and have a low stretch ratio because the cooling rate must be high in the heat treatment, and examples thereof include Japanese Patent Laid-Open Nos. H6-271942 and 7-090488. Can be mentioned.
[3]加工誘起変態鋼
残留オーステナイトを鋼中に存在させ延伸率を増加させる加工誘起変態鋼がある。成形中に残留オーステナイトが高強度のマルテンサイトに変態しながら加工硬化速度が速まり延伸率が増加するのである。加工誘起変態鋼は、残留オーステナイトを含んだ鋼であり、基本添加元素はC、Si、及びMnが知られている。ここで、Cはマルテンサイトの変態温度を低減させオーステナイトを安定させ、Siは炭化物の形成を抑制して残留オーステナイト内の固溶C含量を増加させる役目を果たす。そして、MnはCと共にマルテンサイト変態温度を下げ強度を増加させる役目を果たす。
[3] Work-induced transformation steels There are work-induced transformation steels in which retained austenite is present in the steel to increase the draw ratio. During the molding, the retained austenite is transformed into high-strength martensite, and the work hardening rate is increased and the stretch ratio is increased. The work-induced transformation steel is steel containing residual austenite, and C, Si, and Mn are known as basic additive elements. Here, C serves to reduce the transformation temperature of martensite and stabilize austenite, and Si serves to increase the content of dissolved C in the retained austenite by suppressing the formation of carbides. Mn, together with C, serves to lower the martensitic transformation temperature and increase the strength.
加工誘起変態鋼を自動車の構造部品に用いて軽量化するためには、単純C-Si-Mn系の加工誘起変態鋼より成形性が増加されなければならない。しかも自動車の形状が複雑になるのにつれて従来の成形性鋼は多くの自動車部品に適用できない実状であり、こうした問題点を解決するためには成形性の向上された加工誘起変態鋼を製造しなければならない。 In order to reduce the weight of work-induced transformation steels used in automotive structural parts, the formability must be increased over that of simple C-Si-Mn work-induced transformation steels. Moreover, as the shape of automobiles becomes more complex, conventional formable steels are not applicable to many automobile parts, and in order to solve these problems, work-induced transformation steels with improved formability must be manufactured. I must.
そして、成形性と共に向上されるべき性質は溶接性である。従来の加工誘起変態鋼においては、炭化物の形成を抑制し残留オーステナイトの分率を増加させ成形性を向上させるべくSiを1.5%以上含ませた。しかし、Si含量が高いと溶接性が劣化し、鋼板生産時鋼板同士を溶接する過程において不良発生率が高いばかりでなく、こうした鋼板により自動車部品を製造し点溶接で部品を製造すると、溶接不良が生じる問題があった。 And the property which should be improved with a moldability is weldability. In the conventional work-induced transformation steel, Si is included in an amount of 1.5% or more in order to suppress the formation of carbides, increase the fraction of retained austenite, and improve the formability. However, if the Si content is high, the weldability deteriorates, and not only the defect occurrence rate is high in the process of welding the steel plates during production. There was a problem that occurred.
（発明の開示）
本発明は上述した従来の加工誘起変態鋼の特性を改善するために案出されたもので、C、Si、P、N等鋼組成成分を最適化することにより、成形性に優れ強度が高いことから、自動車構造用部品に用いられた場合部品材料の厚さを縮減し自動車を軽量化することができ、さらに自動車衝突時エネルギー吸収性に優れ自動車の安定性を向上することができ、また溶接性にも優れた引張強度70〜90kgf/mm2級の冷延鋼板を提供することに目的がある。
(Disclosure of the Invention)
The present invention was devised to improve the properties of the above-described conventional work-induced transformation steel, and by optimizing the steel composition components such as C, Si, P, and N, it has excellent formability and high strength. Therefore, when used in automotive structural parts, it is possible to reduce the thickness of the parts material and reduce the weight of the automobile, and to improve the stability of the automobile with excellent energy absorption at the time of automobile collision. The object is to provide a cold-rolled steel sheet having a tensile strength of 70 to 90 kgf / mm 2 and excellent weldability.
また、本発明は前記のような冷延鋼板の製造方法を提供することにも目的がある。 Another object of the present invention is to provide a method for producing such a cold-rolled steel sheet.
（発明を実施するための最良の形態）
以下、本発明を説明する。
前述したように、加工誘起変態鋼の場合、残留オーステナイトを鋼中に存在させ、延伸率を増加させるようC、Si及びMnが基本的に添加され、とりわけSiは炭化物の形成を抑制し残留オーステナイト分率を増加させるよう1.5%以上添加するのが一般であるが、Si含量が多くなるほど鋼板の溶接性が低下する問題があった。
(Best Mode for Carrying Out the Invention)
The present invention will be described below.
As described above, in the case of work-induced transformation steel, residual austenite is present in the steel, and C, Si and Mn are basically added so as to increase the draw ratio. In particular, Si suppresses the formation of carbides and residual austenite. In general, 1.5% or more is added so as to increase the fraction, but there is a problem that the weldability of the steel sheet decreases as the Si content increases.
したがって、本発明者はこうした問題点を解決すべく研究と実験を重ね、その結果、Pを適正量添加すればSi含量を1.5%以下にしながらも優れた成形性と溶接性が得られ、しかも適正量のAlとNの添加でAlNを析出させ結晶粒を微細化し、自動車構造用部品に適した高強度冷延鋼板が得られることを察知し、本発明を提案するに至ったのである。 Therefore, the present inventor repeated research and experiments to solve these problems, and as a result, if an appropriate amount of P is added, excellent formability and weldability can be obtained while the Si content is 1.5% or less. It was discovered that AlN was precipitated by adding appropriate amounts of Al and N to refine crystal grains, and a high-strength cold-rolled steel sheet suitable for automobile structural parts was obtained, and the present invention was proposed.
したがって、本発明は、重量%でC：0.15〜0.25%、Si：0.5〜1.5%、Mn：1.0〜2.0%、P：0.25%以下、S:0.020%以下、Al:0.015〜0.050%、N：0.008〜0.026%、残部Feと不可避な不純物を含み、1.2≦Si[%]+50/8P[%]≦2.0を満足するよう組成される成形性及び溶接性の優れた冷延鋼板に関するものである。 Therefore, the present invention, by weight, C: 0.15-0.25%, Si: 0.5-1.5%, Mn: 1.0-2.0%, P: 0.25% or less, S: 0.020% or less, Al: 0.015-0.050%, N : 0.008 to 0.026%, with the balance Fe and inevitable impurities, and related to cold-rolled steel sheets with excellent formability and weldability, which are composed to satisfy 1.2 ≦ Si [%] + 50 / 8P [%] ≦ 2.0 It is.
また、本発明は、
前記のように組成される鋼を通常の方法で熱間圧延した後冷間圧延することにより冷間圧延板を製造する段階；
前記冷間圧延処理された鋼板を下記関係式の範囲の温度で連続焼鈍する段階；及び
[関係式]
563+651C[%]+42Si[%]+18Mn[%]≦焼鈍温度[℃]≦850℃
前記連続焼鈍した鋼板を20〜100℃/sの冷却速度でオステンパリング(austempering)開始温度400〜450℃まで急冷後350〜400℃まで冷却する段階；を含んで構成される成形性及び溶接性の優れた高強度冷延鋼板の製造方法に関するものである。
The present invention also provides:
A step of producing a cold-rolled sheet by hot-rolling the steel having the above-described composition by a normal method and then cold-rolling;
Continuously annealing the cold-rolled steel sheet at a temperature in the range of the following relational expression:
[Relational expression]
563 + 651C [%] + 42Si [%] + 18Mn [%] ≦ Annealing temperature [℃] ≦ 850 ℃
A step of quenching the continuously annealed steel sheet at an austempering start temperature of 400 to 450 ° C. at a cooling rate of 20 to 100 ° C./s and then cooling to 350 to 400 ° C. It is related with the manufacturing method of the high-strength cold-rolled steel plate which was excellent.
以下、本発明の鋼組成成分及びその制限理由について説明する。 Hereinafter, the steel composition component of the present invention and the reasons for its limitation will be described.
・C:0.15〜0.25%
本発明において、Cは、マルテンサイト変態温度を下げてオーステナイトを安定化させることにより、常温で残留オーステナイトを形成し延伸率を増加させる役目を果たす成分である。しかし、こうした効果を得るためには、0.15重量%(以下、単に%とする)以上添加されなければならないが、0.25%を超えると、その溶接性が劣化し鋼板の溶接及び自動車部品の溶接工程に不利である。
・ C: 0.15-0.25%
In the present invention, C is a component that plays the role of forming retained austenite at room temperature and increasing the stretch ratio by lowering the martensite transformation temperature and stabilizing austenite. However, in order to obtain such an effect, it must be added by 0.15% by weight (hereinafter simply referred to as%) or more, but if it exceeds 0.25%, its weldability deteriorates, and the welding process of steel sheets and automobile parts Disadvantageous.
・Si:0.5〜1.5%
Siは、オステンパリング過程において炭化物形成を抑制する役目を果たす。このように、Siにより炭化物形成が抑制されると、固溶Cの量が増え多くの固溶Cが残留オーステナイトに拡散するので、残留オーステナイトが安定化する。これに反して、Siは溶接性を急激に減少させる為、冷延工程中溶接と自動車部品成形後の溶接を円滑に行えるようSiの含量が少ないほど良い。言い換えれば、適正分率の残留オーステナイトを形成し優れた成形性を確保するためにはSi含量が多くなければならないが、溶接性のためにはSi含量が少なければならないのである。そして、Siは鋼中に多量添加されると、熱間圧延後巻取工程において鋼板表面層の結晶粒界に沿って内部酸化を起こす。熱延鋼板において内部酸化が発生すると、酸洗工程において内部酸化の発生部分に局部的な腐食が生じ、酸洗された鋼板表面が非常に粗くなる。これは冷間圧延工程において表面欠陥となり、焼鈍工程において焼鈍炉内のハースロール(Hearth roll)に欠陥を作り、後続作業において鋼板のざらつきなどの欠陥を発生させる。
・ Si: 0.5-1.5%
Si plays a role of suppressing carbide formation in the male tempering process. Thus, when carbide formation is suppressed by Si, the amount of solute C increases and a large amount of solute C diffuses into the retained austenite, so that the retained austenite is stabilized. On the other hand, since Si decreases weldability rapidly, it is better that the Si content is smaller so that welding during the cold rolling process and welding after molding of automobile parts can be performed smoothly. In other words, the Si content must be high in order to form an appropriate fraction of retained austenite and ensure excellent formability, but the Si content must be low for weldability. When a large amount of Si is added to the steel, internal oxidation occurs along the grain boundaries of the steel sheet surface layer in the winding process after hot rolling. When internal oxidation occurs in the hot-rolled steel sheet, local corrosion occurs in the portion where the internal oxidation occurs in the pickling process, and the pickled steel sheet surface becomes very rough. This becomes a surface defect in the cold rolling process, creates a defect in the hearth roll in the annealing furnace in the annealing process, and generates defects such as roughness of the steel sheet in the subsequent operation.
したがって、本発明においては、炭化物の形成を効果的に抑制すべくSi含量を0.5%以上添加しながら溶接性や熱延鋼板の内部酸化による表面欠陥を考慮し、その上限を1.5%に制限する。溶接性の面からより好ましくはSi含量を0.5〜1.2%に制限するとよい。 Therefore, in the present invention, in order to effectively suppress the formation of carbides, while adding Si content of 0.5% or more, considering the weldability and surface defects due to internal oxidation of the hot-rolled steel sheet, the upper limit is limited to 1.5%. . In view of weldability, the Si content is more preferably limited to 0.5 to 1.2%.
・Mn: 1.0〜2.0%
Mnは、材料の強度を増加させ、Cと同様マルテンサイトの変態温度を低減させオーステナイトを安定化させる役目を果たす成分である。しかし、その添加量が1.0%未満であると、こうした効果を期待することができず、2.0%を超過するとフェライト変態速度が遅くなりすぎ、冷却中形成されるフェライト量が少なくなる問題がある。
・ Mn: 1.0-2.0%
Mn is a component that increases the strength of the material and reduces the martensite transformation temperature and stabilizes austenite in the same manner as C. However, if the added amount is less than 1.0%, such an effect cannot be expected. If the added amount exceeds 2.0%, the ferrite transformation rate becomes too slow, and the amount of ferrite formed during cooling is reduced.
本発明においては、形成されるフェライト量が多くなるほど多量の固溶Cが残留オーステナイトに拡散し残留オーステナイトを安定化させるので、適量のフェライトを形成することが重要である。もし、Mnが過度に添加されると、冷却中フェライトに変態されなかったオーステナイトがオステンパリング温度において高い分率のベイナイトとなり、強度が増加しながら延伸率が減少する。 In the present invention, as the amount of ferrite formed increases, a larger amount of solid solution C diffuses into the retained austenite and stabilizes the retained austenite. Therefore, it is important to form an appropriate amount of ferrite. If Mn is added excessively, austenite that has not been transformed into ferrite during cooling becomes a high fraction of bainite at the male tempering temperature, and the stretch ratio decreases while the strength increases.
本発明においてはこうした点に鑑みてMnの含量を1.0〜2.0%に制限する。 In view of these points, the present invention limits the Mn content to 1.0 to 2.0%.
・P:0.25%以下
Pは、Siのようなフェライト強化元素として、炭化物の形成を効果的に抑制すべく添加する。しかし、その含量が0.25%を超過すると、スラブ製造過程において結晶粒中心部にPが過度に偏析し、連続鋳造過程において破断が生じる可能性が高まり、しかも製品の結晶粒界に多量のPが偏析して結晶粒界の破壊による延性が低減されかねない。
・ P: 0.25% or less
P is added as a ferrite strengthening element such as Si to effectively suppress the formation of carbides. However, if its content exceeds 0.25%, P is segregated excessively in the center of the crystal grain during the slab manufacturing process, and there is a high possibility that fracture will occur in the continuous casting process, and a large amount of P is present at the grain boundary of the product. Segregation may reduce ductility due to fracture of grain boundaries.
上述したように、Si含量が1.5%を超過すると、鋼板の溶接性が悪くなる。したがって、本発明においては、Si添加量を1.5%以下に制御しながら、且つSiと共に添加されると炭化物の形成を抑制するPを同時に添加して、残留オーステナイトの分率を維持することができる。即ち、Pを添加しない従来鋼の場合、炭化物の形成を抑制し残留オーステナイト分率を適正量に維持すべくSiを1.5〜2.0%含有させなければならないが、Pを適正量添加した本発明の場合、Siを0.5〜1.5%で添加しても残留オーステナイトを安定化できるばかりでなく溶接性の向上も図れる。 As described above, when the Si content exceeds 1.5%, the weldability of the steel sheet deteriorates. Therefore, in the present invention, it is possible to maintain the fraction of retained austenite by simultaneously adding P that suppresses the formation of carbides when added with Si while controlling the Si addition amount to 1.5% or less. . That is, in the case of a conventional steel to which P is not added, Si must be contained in an amount of 1.5 to 2.0% in order to suppress carbide formation and maintain the retained austenite fraction in an appropriate amount. In this case, even if Si is added at 0.5 to 1.5%, not only the retained austenite can be stabilized, but also the weldability can be improved.
図1は、1.5Mn-1.5Siが添加された鋼と1.5Mn-1.0Si-0.08Pが添加された鋼の夫々の状態図を示したもので、1.5Mn-1.5Siが添加された鋼と1.5Mn-1.0Si-0.08Pが添加された鋼の状態図が同じであることがわかる。 Fig. 1 shows the phase diagrams of steel added with 1.5Mn-1.5Si and steel added with 1.5Mn-1.0Si-0.08P. It can be seen that the phase diagram of steel added with 1.5Mn-1.0Si-0.08P is the same.
即ち、これは相変態挙動において、0.08%含量のPが0.5%含量のSiと同じ効果を奏することを示すものである。 That is, this indicates that 0.08% content P has the same effect as 0.5% content Si in the phase transformation behavior.
このことに鑑みて、本発明においては、溶接性と熱延鋼板の内部酸化性を改善すべくSi含量を下げながらPを添加する際、1.2≦Si[%]+50/8 P[%]≦2.0の関係を満たすよう、与えられたSi含量に対してPを添加することがより好ましい。 In view of this, in the present invention, when adding P while lowering the Si content to improve the weldability and internal oxidation of the hot-rolled steel sheet, 1.2 ≦ Si [%] + 50/8 P [%] More preferably, P is added to a given Si content so as to satisfy the relationship of ≦ 2.0.
一方、図2は、0.2C-1.0Si-1.5Mn鋼においてP含量とN添加による鋼板の機械的性質の変化を示したグラフである。図2に示したように、Si添加量を1.0%まで低減しP含量を増加させると延伸率が増加し、とりわけP含量が0.08%の際延伸率が著しく増加することがわかる。 On the other hand, FIG. 2 is a graph showing changes in mechanical properties of the steel sheet due to the P content and N addition in 0.2C-1.0Si-1.5Mn steel. As shown in FIG. 2, it can be seen that when the Si addition amount is reduced to 1.0% and the P content is increased, the stretch ratio increases, and particularly when the P content is 0.08%, the stretch ratio increases remarkably.
・S:0.020%以下
SはMnと結合してMnS析出物を形成する。MnSは介在物として形成され、亀裂の開始点として働きかねないので、その析出量が少ないほど有利であるが、本発明においてはこのことを考慮して、S含量を0.020%以下に制限する。
・ S: 0.020% or less
S combines with Mn to form MnS precipitates. Since MnS is formed as an inclusion and may act as a crack initiation point, the smaller the amount of precipitation, the more advantageous. In the present invention, however, considering this, the S content is limited to 0.020% or less.
・Al:0.015〜0.050%
Alは、製鋼工程において添加され、鋼中のＯと反応してスラグを形成し、溶鋼上部に形成されたスラグを除去することにより、鋼中のＯを除去させる脱酸元素である。本発明においては、鋼中のＯを除去し残留したAlを利用してAlN析出物を形成し、残留オーステナイト結晶粒を減少させ延伸率を向上するのに利用する。
・ Al: 0.015-0.050%
Al is a deoxidizing element that is added in the steelmaking process, reacts with O in the steel to form slag, and removes the slag formed on the molten steel, thereby removing O in the steel. In the present invention, O in steel is removed and Al remaining to form AlN precipitates is used to reduce the retained austenite crystal grains and improve the drawing ratio.
一方、同量の残留オーステナイトが存在する場合、結晶粒のサイズが小さく且つ多数のオーステナイトが分布すると、変形中マルテンサイトに変態しながら加工硬化速度を速くさせる効果が高いので、延伸率が向上することが知られている。残留オーステナイトのサイズを縮減させるためには、焼鈍中にオーステナイトのサイズを減少させるべきであり、このため析出物を形成して結晶粒成長を抑えなければならない。 On the other hand, when the same amount of retained austenite is present, if the size of the crystal grains is small and a large number of austenite is distributed, the effect of increasing the work hardening speed while transforming into martensite during deformation is high, so the stretch ratio is improved. It is known. In order to reduce the size of the retained austenite, the size of the austenite should be reduced during annealing, and therefore precipitates must be formed to suppress grain growth.
しかし、析出物が多すぎると、析出硬化により強度が増加し延伸率が低減する傾向があるので、析出物の量を減らしながらオーステナイト結晶粒のサイズを効果的に縮めることが重要である。鉄鋼から析出硬化の効果を得るべく主に使われるNb、Ti、V析出物は、そのサイズが大きいだけでなく、オーステナイト安定化元素であるCと結合してNbC、TiC、VCなどを形成し固溶C含量を減少させるので、加工誘起変態鋼には適していない。従って、これらを総合すると、加工誘起変態鋼において延伸率を増加させるためには、Cと結合せずサイズの小さい析出物を形成すべきであることがわかる。 However, if there are too many precipitates, the strength tends to increase due to precipitation hardening and the stretching ratio tends to decrease. Therefore, it is important to effectively reduce the size of austenite grains while reducing the amount of precipitates. Nb, Ti, V precipitates mainly used to obtain precipitation hardening effects from steel are not only large in size, but also combine with austenite stabilizing element C to form NbC, TiC, VC, etc. It is not suitable for work-induced transformation steel because it reduces the solute C content. Therefore, when these are put together, it can be seen that in order to increase the stretch ratio in the work-induced transformation steel, precipitates having a small size without being bonded to C should be formed.
本発明においては、こうした役目を果たす析出物としてAlNを形成する。AlNはCの固溶度が無く、析出物のサイズがTiC、NbC、VCなどの析出物に比して非常に小さいことが知られている。Alの量が0.015%より小さいと、形成される析出物の数が少ない為、効果的に残留オーステナイトのサイズを縮減することができない。それに比して、Alの量が0.050%より多いと、AlN析出物が粗大化し延伸率の向上に不利である。こうした理由から、本発明においてはAl含量を0.015〜0.050%に制限する。 In the present invention, AlN is formed as a precipitate that fulfills such a role. It is known that AlN has no solid solubility of C, and the size of the precipitate is very small compared to precipitates such as TiC, NbC, and VC. If the amount of Al is less than 0.015%, the number of precipitates formed is small, and the size of retained austenite cannot be reduced effectively. On the other hand, if the amount of Al is more than 0.050%, the AlN precipitates are coarsened, which is disadvantageous for improving the stretching ratio. For these reasons, the Al content is limited to 0.015 to 0.050% in the present invention.
・N: 0.008〜0.026%
Nは、AlNを形成すべく添加される成分である。一般の製鉄所の製鋼工程において、不純物として添加されるNは0.004%以内である。しかし、本発明においては、AlN析出物を形成し結晶粒の微細化を成し遂げるべくNを積極的に添加する。NはAlNの形で析出するので、原子量を考慮すると次のようなN/Al(14/27)で添加することが適切である。即ち、0.015〜0.050%の範囲のAlを添加する際、Nの範囲は0.008〜0.026%にすることが適切である。こうした範囲でNを添加する際、適量のAlNが形成され残留オーステナイト結晶粒のサイズが縮減され、図2のように延伸率が高められるのである。
・ N: 0.008 ~ 0.026%
N is a component added to form AlN. In a steelmaking process in a general steelworks, N added as an impurity is within 0.004%. However, in the present invention, N is positively added in order to form AlN precipitates and achieve crystal grain refinement. Since N precipitates in the form of AlN, it is appropriate to add N / Al (14/27) as follows considering the atomic weight. That is, when adding Al in the range of 0.015 to 0.050%, the range of N is suitably 0.008 to 0.026%. When N is added in such a range, an appropriate amount of AlN is formed, the size of residual austenite crystal grains is reduced, and the stretch ratio is increased as shown in FIG.
図3は、AlN析出物がオーステナイト結晶粒の移動を抑制することを示した図で、焼鈍中AlN析出物がオーステナイト成長を抑制することがわかる。 FIG. 3 is a diagram showing that AlN precipitates suppress the movement of austenite crystal grains, and it can be seen that AlN precipitates suppress austenite growth during annealing.
次に、本発明の鋼板製造工程について説明する。 Next, the steel plate manufacturing process of the present invention will be described.
本発明は、前記のように組成された鋼を熱間圧延して巻き取り、次いで熱間圧延板を冷間圧延してから連続焼鈍し熱処理することにより、成形性及び溶接性の優れた高強度冷延鋼板を製造することができる。 In the present invention, the steel having the above composition is hot-rolled and wound up, and then the hot-rolled sheet is cold-rolled and then continuously annealed and heat-treated, so that it has excellent formability and weldability. A strength cold-rolled steel sheet can be produced.
本発明は、こうした製造工程中冷間圧延板の連続焼鈍工程とオステンパリング(austempering)条件を制御することに特徴があるもので、これを具体的に説明すれば次のとおりである。 The present invention is characterized by controlling the continuous annealing step of the cold-rolled sheet and the male tempering conditions during the manufacturing process, which will be described in detail as follows.
先ず、本発明においては、前記のように組成された鋼を使って、通常の方法により熱間圧延及び冷間圧延処理を行い、冷間圧延板を製造する。即ち、後述する熱間圧延条件と冷間圧延条件は本発明に用いられる代表的な一例に過ぎず、本発明はこれに制限されるものではない。 First, in the present invention, hot rolling and cold rolling treatment are performed by a normal method using the steel having the above composition to produce a cold rolled sheet. That is, the hot rolling conditions and cold rolling conditions described below are merely representative examples used in the present invention, and the present invention is not limited to these.
本発明においては前記組成の鋼を高温で再加熱し熱間圧延するが、この際、その再加熱温度を1050〜1300℃に制御することが好ましい。そして上記のように再加熱後、熱間圧延する際その仕上げ圧延温度を890〜940℃に制御することが好ましい。また、前記のように圧延して巻き取るが、この際巻取温度は600〜700℃とすることが好ましい。 In the present invention, the steel having the above composition is reheated at a high temperature and hot-rolled. At this time, the reheating temperature is preferably controlled to 1050 to 1300 ° C. And after reheating as mentioned above, it is preferable to control the finish rolling temperature at 890-940 degreeC when hot-rolling. Moreover, it rolls and winds as mentioned above, but it is preferable that winding temperature shall be 600-700 degreeC in this case.
次いで、前記得た熱間圧延板を酸洗し冷間圧延するが、この際冷間圧下率は40〜70%とすることが好ましい。 Next, the obtained hot-rolled sheet is pickled and cold-rolled. At this time, the cold rolling reduction is preferably 40 to 70%.
次いで、前記冷間圧延処理された鋼板を下記関係式の範囲の温度において連続焼鈍する。
[関係式]
563+651C[%]+42Si[%]+18Mn[%]≦焼鈍温度[℃]≦850℃
Next, the cold-rolled steel sheet is continuously annealed at a temperature within the range of the following relational expression.
[Relational expression]
563 + 651C [%] + 42Si [%] + 18Mn [%] ≦ Annealing temperature [℃] ≦ 850 ℃
前述したように、C、Si、Mnを含んだ鋼を用いて延伸率を増加させるためには残留オーステナイトの含量を増加させなければならない。しかし、本発明者の研究によると、残留オーステナイトを増加させるためには熱処理サイクルを成分に適するよう設定しなければならない。 As described above, in order to increase the draw ratio using steel containing C, Si, and Mn, the content of retained austenite must be increased. However, according to the inventor's work, in order to increase the retained austenite, the heat treatment cycle must be set to suit the components.
連続焼鈍炉において焼鈍する際、残留オーステナイトを形成するためには、アニーリング(annealing)してオーステナイトを形成し、オステンパリング(austempering)温度まで冷却してオステンパリングしベイナイトを形成しながら固溶Cを残留オーステナイトに拡散させ、オーステナイトを安定化させなければならない。この際、焼鈍温度をうまく設定することが重要である。焼鈍温度が低すぎると、熱延鋼板に存在するパーライトが溶解されず、オーステナイトの安定性を低下させる。また、焼鈍温度が高すぎると、オーステナイトが過多に形成されフェライトが少なくなるので、最終的にベイナイトが形成され過ぎて強度が増加し延伸率が低下する。 In order to form retained austenite when annealing in a continuous annealing furnace, annealing is performed to form austenite, cooling to austempering temperature and cooling to austempering temperature to form bainite. It must diffuse into the retained austenite to stabilize the austenite. At this time, it is important to set the annealing temperature well. If the annealing temperature is too low, the pearlite present in the hot-rolled steel sheet is not melted and the stability of the austenite is lowered. On the other hand, if the annealing temperature is too high, austenite is excessively formed and ferrite is decreased, so that bainite is finally formed excessively, the strength is increased, and the stretch ratio is lowered.
本発明の発明者は、こうした事実を考慮して各成分の鋼について最適の焼鈍温度を設定するための研究及び実験を重ねた結果、図4の結果を得た。 The inventor of the present invention has obtained the results shown in FIG. 4 as a result of repeated research and experiments for setting the optimum annealing temperature for each component steel in consideration of such facts.
図4は、C、Si、Mnの含量を変化させながら焼鈍温度に応じたオーステナイト量を示したグラフであり、同じ成分の鋼を用いる場合に残留オーステナイト量を増加させるためには、焼鈍温度を上昇させるべきであることがわかる。このように、焼鈍温度を上昇させると、最大フェライトを形成し、オーステナイトに最大の固溶Cを拡散することができるが、この際フェライト分率を最大に増加させながらパーライトは必ず溶解されなければならない。その理由は、前記パーライトには炭化物が多量存在するので、パーライトが存在するとオーステナイトに拡散される固溶Cが減るからである。このようなパーライトを完全に溶解させるためには、Cの含量が0.1、0.15、0.20%の各鋼においてオーステナイトの量が19、28、38%でなけねればならない。これ以上のオーステナイトを形成すると、フェライトの量が減ってしまうため残留オーステナイトを多く形成させ難い。 Fig. 4 is a graph showing the amount of austenite according to the annealing temperature while changing the contents of C, Si, and Mn, and in order to increase the amount of retained austenite when using the steel of the same component, the annealing temperature was changed. You can see that it should be raised. Thus, when the annealing temperature is raised, the maximum ferrite can be formed and the maximum solid solution C can be diffused in the austenite, but the pearlite must be dissolved without increasing the ferrite fraction to the maximum. Don't be. The reason is that since a large amount of carbide exists in the pearlite, the solid solution C diffused into the austenite decreases when pearlite is present. In order to completely dissolve such pearlite, the amount of austenite must be 19, 28, and 38% in each steel having a C content of 0.1, 0.15, and 0.20%. If more austenite is formed, the amount of ferrite is reduced, so that it is difficult to form much retained austenite.
こうした条件から、本発明の発明者はパーライトを完全に溶解させる焼鈍温度は少なくとも563+651C[%]+42Si[%]+18Mn[%]以上でなければならないことがわかった。しかし、前記焼鈍温度が850℃以上であると、オーステナイトの形成が多くなり過ぎるので、上限は850℃とした。 From these conditions, the inventors of the present invention have found that the annealing temperature for completely dissolving pearlite must be at least 563 + 651C [%] + 42Si [%] + 18Mn [%]. However, if the annealing temperature is 850 ° C. or higher, austenite formation becomes excessive, so the upper limit was set to 850 ° C.
したがって、本発明において最適な焼鈍温度の範囲は前記関係式により定義される。 Therefore, the optimum annealing temperature range in the present invention is defined by the relational expression.
また、本発明においては前記焼鈍温度において適正なオーステナイトを形成すべく、その焼鈍時間を50秒以上に設定することが好ましい。 In the present invention, it is preferable to set the annealing time to 50 seconds or more in order to form appropriate austenite at the annealing temperature.
そして、上記のように連続焼鈍された鋼板は、焼鈍区間においてオーステナイトが形成された材料をパーライトができないようオステンパリング開始温度400〜450℃まで急冷してから350〜450℃まで冷却するオステンパリングを実施する。 The steel sheet that has been continuously annealed as described above is subjected to male tempering in which the material in which the austenite is formed in the annealing section is rapidly cooled to 400 to 450 ° C. and then cooled to 350 to 450 ° C. so that pearlite cannot be formed. carry out.
連続焼鈍区間において、オステンパリング開始温度までは急冷するが、この際の冷却速度は約20〜100℃/secとすることが好ましい。オステンパリングする際、焼鈍区間において形成されたオーステナイトの一部がベイナイトとなり、固溶Cが残留オーステナイトに拡散して残留オーステナイトが安定化する。 In the continuous annealing section, the temperature is rapidly cooled to the male tempering start temperature, and the cooling rate at this time is preferably about 20 to 100 ° C./sec. When male tempering is performed, a part of austenite formed in the annealing section becomes bainite, and solid solution C diffuses into the retained austenite to stabilize the retained austenite.
そして、焼鈍区間において、オステンパリング開始温度の400〜450℃まで急冷してから再び350〜450℃まで冷却するが、好ましくは200〜500sec間冷却することがよい。 And in an annealing area, although it cools to 350-450 degreeC again after quenching to 400-450 degreeC of a male tempering start temperature, Preferably it is good to cool for 200-500 second.
以下、本発明を実施例を基により具体的に説明する。しかし、後述する実施例は本発明の好ましき一実施例を記述するもので、本発明がこうした実施例の記載内容により制限されるものとして解釈されてはならない。 Hereinafter, the present invention will be specifically described based on examples. However, the embodiment described below describes a preferred embodiment of the present invention, and the present invention should not be construed as being limited by the description of such embodiment.
[実施例]
表1のような組成の鋼片を夫々用意してから、これらについて熱間圧延を施した。この際、再加熱温度は1250℃、仕上げ熱間圧延温度は910℃、そして巻取温度は600℃とした。次いで、巻き取られた熱間圧延板の表面酸化層を酸洗により除去した後、50%冷間圧延を施して1.4mm厚の冷延鋼板を製造した。そして、このように冷間圧延された鋼板を連続焼鈍炉において熱処理し、この熱処理の際焼鈍時間は51〜102秒とし、オステンパリング時間は300秒とした。
[Example]
Steel slabs having the compositions shown in Table 1 were prepared, and then hot rolled. At this time, the reheating temperature was 1250 ° C., the finish hot rolling temperature was 910 ° C., and the winding temperature was 600 ° C. Next, after removing the surface oxide layer of the rolled hot-rolled sheet by pickling, cold rolling was performed by 50% to produce a cold-rolled steel sheet having a thickness of 1.4 mm. And the steel plate cold-rolled in this way was heat-processed in the continuous annealing furnace, the annealing time in this heat treatment was 51 to 102 seconds, and the male tempering time was 300 seconds.
こうした熱処理条件別冷延鋼板材質の測定結果を表2に示した。
前記表1及び表2に示したように、その組成成分と連続焼鈍条件等が最適に制御された本発明例(1〜11)の場合は全て、延伸率特性ばかりでなく溶接特性等も優れていた。 As shown in Table 1 and Table 2, in the case of the present invention examples (1 to 11) in which the composition components and continuous annealing conditions are optimally controlled, not only the draw ratio characteristics but also the welding characteristics are excellent. It was.
これに対して、その組成成分が本発明の範囲を外れた比較例(3〜13)の場合には、全般に延伸率が悪くなり溶接性もやはり良くなかった。とりわけ、Si添加量が1.5%を超過した鋼種B3を用いた比較例(11〜14)の場合、全て溶接性が非常に悪かった。 On the other hand, in the case of Comparative Examples (3 to 13) whose composition components were outside the scope of the present invention, the stretch ratio was generally poor and the weldability was also not good. In particular, in the comparative examples (11 to 14) using steel type B3 in which the Si addition amount exceeded 1.5%, all the weldability was very poor.
そして、Si+50/8Pが1.2未満の鋼組成(B5)を用いた比較例(15)と窒素添加量が寡少な鋼種(B6)を使った比較例(16)の場合にも延伸率特性が良くなかった。 And in the comparative example (15) using a steel composition (B5) with Si + 50 / 8P less than 1.2 and the comparative example (16) using a steel type (B6) with a small amount of nitrogen addition, the draw ratio characteristics Was not good.
一方、比較例(1〜2)は、その組成成分が本発明範囲であるが焼鈍温度が本発明範囲を外れる場合であり、比較例(1)は焼鈍温度が低すぎて鋼板の再結晶が完全に成されなかったり炭化物が完全に溶解されない為、均一な残留オーステナイトが得られず延伸率が悪くなることがわかる。そして、比較例(2)は焼鈍温度が高すぎて加工性に悪影響を及ぼす針状形残留オーステナイトができる為、鋼の延伸率が急減した。 On the other hand, Comparative Example (1-2) is a case where the composition component is within the scope of the present invention, but the annealing temperature is outside the scope of the present invention, and Comparative Example (1) is too low for recrystallization of the steel sheet. It can be seen that since it is not completely formed or the carbide is not completely dissolved, uniform retained austenite cannot be obtained and the drawing ratio is deteriorated. In Comparative Example (2), since the annealing temperature is too high and acicular retained austenite having an adverse effect on workability is formed, the steel drawing rate rapidly decreased.
（発明の効果）
上述したように、本発明は、延伸率が高くて成形性の優れた高強度鋼板を提供し、この高強度鋼板は自動車構造用部品に用いられ自動車の安定性を向上させる有利な効果を奏する。
(The invention's effect)
As described above, the present invention provides a high-strength steel sheet having a high draw ratio and excellent formability, and this high-strength steel sheet is used for automobile structural parts and has an advantageous effect of improving the stability of the automobile. .
本発明の好ましき実施例が説明の目的から記載されているが、当業者は、添付の請求範囲に記載された技術思想と範囲を外れずに、様々な変更、追加及び代替が可能なことに想到するであろう。 While the preferred embodiments of the present invention have been described for purposes of illustration, those skilled in the art may make various modifications, additions and substitutions without departing from the spirit and scope of the appended claims. You will think of that.
Claims (5)
前記冷間圧延板を下記関係式の範囲の温度において連続焼鈍する段階;及び、
[関係式]
563+651 C[%]+42 Si[%]+18 Mn[%]≦焼鈍温度 [℃]≦850℃
前記連続焼鈍された鋼板を20〜100℃/sの冷却速度でオステンパリング(austempering)開始温度400〜450℃まで急冷した後350〜400℃まで冷却する段階;を含む成形性及び溶接性の優れた高強度冷延鋼板の製造方法。 C: 0.15-0.25%, Si: 0.5-1.5%, Mn: 1.0-2.0%, P: 0.25% or less, S: 0.020% or less, Al: 0.015-0.050%, N: 0.008-0.026% By subjecting the steel containing the balance Fe and unavoidable impurities to 1.2 ≦ Si [%] + 50/8 P [%] ≦ 2.0 to hot rolling under normal conditions and then cold rolling Producing cold rolled sheets;
Continuously annealing the cold-rolled sheet at a temperature within the range of the following relational expression; and
[Relational expression]
563 + 651 C [%] + 42 Si [%] + 18 Mn [%] ≦ Annealing temperature [℃] ≦ 850 ℃
A step of rapidly cooling the continuously annealed steel sheet to austempering start temperature of 400 to 450 ° C. at a cooling rate of 20 to 100 ° C./s and then cooling to 350 to 400 ° C .; excellent formability and weldability A method for producing high strength cold-rolled steel sheets.
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| KR1020010085539A KR100554753B1 (en) | 2001-12-27 | 2001-12-27 | High strength cold rolled steel sheet with superior formability and weldability and method for manufacturing thereof |
| KR2001/85539 | 2001-12-27 | ||
| PCT/KR2002/001167 WO2003056041A1 (en) | 2001-12-27 | 2002-06-20 | High strength cold rolled steel sheet with superior formability and weldability, and manufacturing method therefor |
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| JP2005513271A JP2005513271A (en) | 2005-05-12 |
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| EP (1) | EP1458896A4 (en) |
| JP (1) | JP3895728B2 (en) |
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| JP5165236B2 (en) * | 2006-12-27 | 2013-03-21 | 新日鐵住金ステンレス株式会社 | Stainless steel plate for structural members with excellent shock absorption characteristics |
| US8752752B2 (en) * | 2009-03-09 | 2014-06-17 | Hong Kong Polytechnic University | Method of making a composite steel plate |
| KR101129757B1 (en) * | 2009-03-26 | 2012-03-23 | 현대제철 주식회사 | Method for preventing edge part saw type crack of thin slab |
| MX357839B (en) * | 2011-07-29 | 2018-07-26 | Nippon Steel & Sumitomo Metal Corp | High-strength zinc-plated steel sheet and high-strength steel sheet having superior moldability, and method for producing each. |
| CA2879540C (en) * | 2012-08-06 | 2018-06-12 | Nippon Steel & Sumitomo Metal Corporation | Cold-rolled steel sheet and method for manufacturing same, and hot-stamp formed body |
| CN103276303A (en) * | 2013-06-07 | 2013-09-04 | 南京钢铁股份有限公司 | High strength chain steel for mine, and preparation method thereof |
| CN104630641B (en) * | 2014-12-11 | 2017-02-22 | 武汉钢铁(集团)公司 | 800MPa-grade high-strength high-plasticity low-carbon medium-manganese steel and manufacturing method thereof |
| CN105154763A (en) * | 2015-09-24 | 2015-12-16 | 华北理工大学 | Low-carbon silicon-manganese bainite high-strength steel and production method thereof |
| CN108441604B (en) * | 2018-01-24 | 2019-09-03 | 易觉汽车科技（上海）有限公司 | A kind of auto parts and components part intensity adjustable design method |
| CN117127099B (en) * | 2023-04-28 | 2024-04-16 | 鞍钢股份有限公司 | 1300MPa ultra-high strength plastic cold-rolled Mn-TRIP steel and preparation method thereof |
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| JPH0238532A (en) * | 1988-07-29 | 1990-02-07 | Kobe Steel Ltd | Manufacture of cold rolled high-tensile sheet steel |
| JPH09194935A (en) * | 1996-01-10 | 1997-07-29 | Toyo Kohan Co Ltd | Production of cold rolled steel sheet for gasket material, excellent in spring characteristic, and gasket material |
| FR2757877B1 (en) * | 1996-12-31 | 1999-02-05 | Ascometal Sa | STEEL AND PROCESS FOR THE MANUFACTURE OF A SHAPED STEEL PART BY COLD PLASTIC DEFORMATION |
| JPH10259448A (en) * | 1997-03-21 | 1998-09-29 | Kobe Steel Ltd | High strength steel sheet excellent in static absorbed energy and impact resistance and its production |
| JP3448454B2 (en) * | 1997-04-10 | 2003-09-22 | 新日本製鐵株式会社 | High-strength cold-rolled steel sheet with excellent surface properties and formability, and method for producing the same |
| JP3727151B2 (en) * | 1997-09-04 | 2005-12-14 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet for drums, method for producing the same, and steel high-strength drum |
| KR100328044B1 (en) * | 1997-11-04 | 2002-05-10 | 이구택 | A Manufacturing Method of High Strength Cold Rolled Steel Sheet Having |
| JP3401427B2 (en) * | 1998-03-12 | 2003-04-28 | 株式会社神戸製鋼所 | High-strength steel sheet with excellent impact resistance |
| JPH11343538A (en) * | 1998-05-29 | 1999-12-14 | Kawasaki Steel Corp | Cold-rolled steel sheet suitable for high-density energy beam welding and its production |
| JP3424619B2 (en) * | 1999-09-16 | 2003-07-07 | 住友金属工業株式会社 | High tensile cold rolled steel sheet and method for producing the same |
| KR100415667B1 (en) * | 1999-12-20 | 2004-01-31 | 주식회사 포스코 | A method for high strength cold rolled steel sheet having superior impact absorption property and formability and a method for manufacturing it |
| JP4524850B2 (en) * | 2000-04-27 | 2010-08-18 | Ｊｆｅスチール株式会社 | High-tensile cold-rolled steel sheet with excellent ductility and strain age hardening characteristics and method for producing high-tensile cold-rolled steel sheet |
| JP4839527B2 (en) * | 2000-05-31 | 2011-12-21 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet with excellent strain age hardening characteristics and method for producing the same |
| KR100470652B1 (en) * | 2000-12-20 | 2005-03-07 | 주식회사 포스코 | A method for manufacturing high strength cold rolled steel sheet with superior formability |
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2001
- 2001-12-27 KR KR1020010085539A patent/KR100554753B1/en not_active IP Right Cessation
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2002
- 2002-06-20 JP JP2003556557A patent/JP3895728B2/en not_active Expired - Fee Related
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