JP2503338B2 - Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot welds - Google Patents
Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot weldsInfo
- Publication number
- JP2503338B2 JP2503338B2 JP3341214A JP34121491A JP2503338B2 JP 2503338 B2 JP2503338 B2 JP 2503338B2 JP 3341214 A JP3341214 A JP 3341214A JP 34121491 A JP34121491 A JP 34121491A JP 2503338 B2 JP2503338 B2 JP 2503338B2
- Authority
- JP
- Japan
- Prior art keywords
- strength
- steel sheet
- rolled steel
- spot
- cold rolled
- 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 - Fee Related
Links
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は自動車のパネルや家電製
品に使用される成形性が良好でスポット溶接部の疲労強
度性に優れた高強度冷延鋼板に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength cold-rolled steel sheet which has good formability and is excellent in fatigue strength of spot welds used for automobile panels and home electric appliances.
【０００２】[0002]
【従来の技術】冷延鋼板の強度を上昇するために、従来
多くの試みが成されている。特に引張り強さが３５〜５
０kgf/mm2 を有する鋼板の場合には、Ｓｉ，Ｍｎ，Ｃｒ
あるいはＰなどを添加し、強度増加を図ってきた。ま
た、最近の技術進歩により極低炭素鋼の溶製が容易とな
り、これをベースにＴｉやＮｂを添加して加工性を確保
している。一方、この種の鋼板はプレス加工等で成形し
た部品を組立てる際に、スポット溶接が行われるが、こ
のスポット溶接に関しても多くの技術が提案されてい
る。2. Description of the Related Art Many attempts have heretofore been made to increase the strength of cold-rolled steel sheets. Especially tensile strength is 35-5
In the case of a steel sheet having 0 kgf / mm 2 , Si, Mn, Cr
Alternatively, P has been added to increase the strength. Further, due to recent technological advances, it becomes easy to melt ultra-low carbon steel, and Ti or Nb is added to this to secure workability. On the other hand, this type of steel plate is spot-welded when assembling parts formed by press working or the like, and many techniques have been proposed for this spot welding.
【０００３】例えば特開昭６３−３１０９３９号公報に
は、Ｔｉおよび／またはＮｂを添加した極低炭素鋼板に
おいて、再結晶焼鈍温度、時間を選んで断面組織率で５
〜３０％の未再結晶組織を残存させることにより、ナゲ
ット部およびその周辺の硬度分布を最適化することでス
ポット溶接部の継手疲労強度を向上ささせることが開示
されている。しかしこの様な組織を有する鋼板は、伸び
（Ｅｌ）や平均ラングフォド値（ｒ値）が低く、成形性
に問題がある。また、製造条件が狭く、厳しい温度制御
が必要となる。For example, Japanese Patent Laid-Open No. 63-310939 discloses an ultra-low carbon steel sheet to which Ti and / or Nb is added, and the recrystallization annealing temperature and time are selected to obtain a cross-sectional structure ratio of 5
It is disclosed that the joint fatigue strength of the spot welded portion is improved by optimizing the hardness distribution of the nugget portion and its periphery by leaving ˜30% of the non-recrystallized structure. However, a steel sheet having such a structure has a low elongation (El) and an average Langfoud value (r value), and has a problem in formability. In addition, manufacturing conditions are narrow, and strict temperature control is required.
【０００４】また、特開昭６３−３１７６４７号公報に
は、ＴｉとＮｂを同時に添加した極低炭素鋼板におい
て、粒径０．０５μｍ以下のＴｉ化合物を析出させるこ
とにより降伏強度（ＹＰ）を上昇させてスポット溶接時
の接触抵抗を高めて、溶接部の強度靭性を向上させるこ
とが記述されている。この種の鋼板において微細析出物
はＥｌの劣化を招来する傾向があり、またＹＰを上昇さ
せることは極低炭素鋼板の基本性能であるプレス時の形
状凍結性を損なうことになる。In Japanese Patent Laid-Open No. 63-317647, the yield strength (YP) is increased by precipitating a Ti compound having a grain size of 0.05 μm or less in an ultra low carbon steel sheet to which Ti and Nb are added at the same time. It is described that the contact resistance during spot welding is increased to improve the strength and toughness of the welded portion. In this type of steel sheet, fine precipitates tend to cause deterioration of El, and increasing YP impairs the shape fixability at the time of pressing, which is the basic performance of the ultra-low carbon steel sheet.
【０００５】更に特開昭６３−３１７６４８号公報で
は、Ｔｉ−Ｎｂ極低炭素鋼板表面にダル加工を施し表面
粗度を大きくすることにより、鋼板と鋼板の接触面積を
小さくして溶接時の接触抵抗を大きくすることで良好な
スポット溶接性を得る発明を提案し、特開昭６３−３１
７６４９号公報では、Ｔｉ，Ｎｂ，Ｂを適当量添加する
ことによりＹＰを高くして接触抵抗を高め、かつ溶接後
の組織を微細にし溶接部の強度上昇を図ることを開示し
ている。しかし前者の表面粗度を大きくするには製造コ
ストが高くなり、後者の引張り強度（ＴＳ）を上げ高強
度化したときにはＹＰが更に上昇し、面歪みが懸念され
る。Further, in Japanese Laid-Open Patent Publication No. 63-317648, the surface of Ti-Nb ultra-low carbon steel sheet is dulled to increase the surface roughness, thereby reducing the contact area between the steel sheets and the contact during welding. An invention has been proposed in which good resistance to spot welding is obtained by increasing the resistance.
Japanese Patent No. 7649 discloses that by adding Ti, Nb, and B in appropriate amounts, YP can be increased to increase contact resistance, and the structure after welding can be made fine to increase the strength of the welded portion. However, in the former case, the manufacturing cost is increased to increase the surface roughness, and in the latter case, when the tensile strength (TS) is increased to increase the strength, YP is further increased, and there is a fear of surface strain.
【０００６】なお、最近極低炭素鋼あるいはこれにＮｂ
および、あるいはＢを添加したものにおいて、Ａｌ／Ｎ
バランスおよびＯ量を適性にすることでスポット溶接継
手の耐疲労特性を良好にすることが特開平２−１６３３
２３号公報により提案されているが、Ｔｉ含有極低炭素
鋼板についての開示がなく、またＡｌを多量に含有する
ので製造コスト上の問題もある。Recently, ultra-low carbon steel or Nb
And / or B added, Al / N
It is possible to improve the fatigue resistance of spot welded joints by adjusting the balance and O content appropriately.
Although it is proposed by Japanese Patent Publication No. 23, there is no disclosure about a Ti-containing ultra-low carbon steel sheet, and since it contains a large amount of Al, there is a problem in manufacturing cost.
【０００７】[0007]
【発明が解決しようとする課題】自動車のパネルなどに
使用される望ましい高強度冷延鋼板は、降伏強度はそれ
ほど高くなく、かつ著しく加工硬化し、さらに塗装焼付
硬化能を合わせ持つ鋼板である。また、プレス成形時に
ＹＰ−Ｅｌが０．２％以下でストレッチャーストレイン
が発生せず、平均ｒ値（深絞り特性）や伸び（張出特
性）などの加工性にも優れ、かつ２次加工性にも優れる
必要がある。更にはプレス成形部品を組立てる際にはス
ポット溶接性も良くなくてはならない。前記した各先行
技術にはスポット溶接性についての開示はあるが、上記
した加工成形にともなって要求される諸特性を具備する
と共にスポット溶接部に優れた疲労強度を有するものは
見当たらない。A desirable high-strength cold-rolled steel sheet used for an automobile panel or the like is a steel sheet which does not have a very high yield strength, is significantly work-hardened, and has a paint bake hardening ability. In addition, when YP-El is 0.2% or less during press molding, stretcher strain does not occur, excellent workability such as average r value (deep drawing property) and elongation (overhang property), and secondary processing. It also needs to be excellent. Furthermore, spot weldability must be good when assembling press-formed parts. Although each of the above-mentioned prior arts discloses the spot weldability, none of the above-mentioned prior arts has the properties required for the work forming and the spot welds have excellent fatigue strength.
【０００８】本発明は、極低炭素鋼に従来固溶体強化元
素として余り用いられていないＭｎ，Ｃｒを添加してこ
れらを有効に活用し、更にＴｉ，Ｎｂの少なくとも一種
を含有せしめた極低炭素冷延鋼板であって、降伏強度
（ＹＰ）が１５〜２５kgf/mm2、降伏比（ＹＲ＝ＹＰ／
ＴＳ，ＴＳ：引張強度）が０．５５以下、プレス成形時
に降伏点伸び（ＹＲ−Ｅｌ）が０．２％以下、加工硬化
量（ＷＨ）が４kgf/mm2以上、塗装焼付時の焼付硬化量
（ＢＨ）が２〜５kgf/mm2 で、かつＷＨ＋ＢＨかつ６kg
f/mm2 以上、平均ｒ値が１．５以上、Ｔ．Ｅｌが３５％
以上，延性−脆性遷移温度が−５０℃以下の優れた２次
加工性を有する成形後の面形状性が良好で、かつ優れた
耐デント性を具備し、しかもスポット溶接部の疲労強度
に優れた高強度冷延鋼板を提供することを目的とする。According to the present invention, Mn and Cr, which have not been used as solid solution strengthening elements in the past, are added to ultra-low carbon steel to make effective use of them, and further, ultra-low carbon containing at least one of Ti and Nb. A cold-rolled steel sheet having a yield strength (YP) of 15 to 25 kgf / mm 2 and a yield ratio (YR = YP /
TS, TS: Tensile strength) 0.55 or less, Yield point elongation (YR-El) 0.2% or less during press molding, Work hardening amount (WH) 4 kgf / mm 2 or more, Bake hardening during coating baking Quantity (BH) is 2-5kgf / mm 2 , and WH + BH and 6kg
f / mm 2 or more, average r value of 1.5 or more, T.I. El is 35%
As described above, the ductility-brittleness transition temperature is -50 ° C or less, the secondary workability is excellent, the surface shape property after molding is excellent, the dent resistance is excellent, and the fatigue strength of the spot weld is excellent. It is intended to provide a high strength cold rolled steel sheet.
【０００９】[0009]
【課題を解決するための手段】上記目的を達成するため
に本発明は以下の構成を要旨とする。即ち重量で、 (1) Ｃ ：０．０００３〜０．０１％、 Ｓｉ：０．００５〜０．５％、 Ｍｎ：０．３〜３．０％、 Ｃｒ：０．０１〜３．０％、 かつ、Ｍｎ＋Ｃｒを０．５％以上となるようにし、 Ｐ ：０．００１〜０．１２％、 Ｓ ：０．００１〜０．０１５％、 Ａｌ：０．００５〜０．１０％、 Ｂ ：０．０００１〜０．００２％ さらに、 Ｔｉ：０．００３〜０．１０％および Ｎｂ：０．００３〜０．１０％の一種または二種であ
て、 Ｔｉ＊＝Ｔ．Ｔｉ−３．４２Ｎの時２≦（Ｔｉ＊＋０．
５２Ｎｂ）／Ｃ≦２０になるように含有し、残部Ｆｅお
よび不可避不純物からなることを特徴とするスポット溶
接部の疲労強度に優れた良加工性高強度冷延鋼板であ
り、(2) 上記鋼板に、更に重量でＢ：０．０００１〜
０．００２％含有せしめたことを特徴とする成形性およ
びスポット溶接部の疲労強度に優れた良加工性高強度冷
延鋼板である。In order to achieve the above object, the present invention has the following structures. That is, by weight, (1) C: 0.0003 to 0.01%, Si: 0.005 to 0.5%, Mn: 0.3 to 3.0%, Cr: 0.01 to 3.0% , And Mn + Cr to be 0.5% or more, P: 0.001 to 0.12%, S: 0.001 to 0.015%, Al: 0.005 to 0.10%, B: 0.0001 to 0.002% Further, one or two of Ti: 0.003 to 0.10% and Nb: 0.003 to 0.10%, Ti * = T. When Ti−3.42N, 2 ≦ (Ti * + 0.
52 Nb) / C ≦ 20, and is a good workability high strength cold rolled steel sheet excellent in fatigue strength of spot welds, characterized in that it comprises the balance Fe and unavoidable impurities. In addition, by weight B: 0.0001-
It is a good workability high strength cold rolled steel sheet excellent in formability and fatigue strength of spot welds, which is characterized by containing 0.002%.
【００１０】[0010]
【作用】本発明者らは、３５〜５０kgf/mm2 級のＴＳを
もち、加工性の優れた冷延鋼板を得るのに、加工性が良
好となるＴｉやＮｂを単独および複合添加した極低炭素
鋼をベースにして鋭意研究をし、以下に述べるような新
知見を得た。The present inventors have obtained a cold-rolled steel sheet having a TS of 35 to 50 kgf / mm 2 grade and excellent workability, and a workability-improving Ti or Nb single or composite electrode added. Through intensive research based on low carbon steel, we obtained new knowledge as described below.
【００１１】第１に、上記ベース鋼に、代表的な固溶体
強化元素であるＳｉ，Ｐ，Ｍｎ，Ｃｒを添加し、冷延、
焼鈍、調質圧延後の引張特性、特に降伏挙動と加工硬化
現象を詳細に調査した。その結果、従来から固溶体強化
元素として多用されているＳｉ，Ｐは、ａ）まず微量の
添加で著しく降伏強度を上昇させること、ｂ）その結果
低歪域での加工硬化率が著しく減少することが判明し
た。First, Si, P, Mn, and Cr, which are typical solid solution strengthening elements, are added to the above base steel and cold rolled,
The tensile properties after annealing and temper rolling, especially the yield behavior and work hardening phenomenon were investigated in detail. As a result, Si and P, which are conventionally frequently used as solid solution strengthening elements, are as follows: a) First, the addition of a very small amount significantly increases the yield strength, and b) As a result, the work hardening rate in a low strain region is significantly reduced. There was found.
【００１２】一方、従来固溶体強化元素としてあまり用
いられないＭｎ，Ｃｒを添加すると、ａ）降伏強度は殆
ど上昇せず、ｂ）引張強度が上昇する、ｃ）その結果、
低歪域での加工硬化率がむしろこれらの添加により増加
するという、極めて重要な新知見を得た。これらの機構
についても検討を加えた結果、ａ）降伏強度はＦｅ元素
と添加したＸ元素との原子半径の差で決定され、原子半
径の差が大きいほど増加する、ｂ）加工硬化率は転位の
すべり挙動と深く関係し、Ｘ元素の添加により積層欠陥
エネルギーが低下すると、転位の交差すべりが困難とな
り加工硬化率が増加する、という基本原理を構築した。
これによれば、Ｓｉ，ＰはＦｅより著しく原子半径が小
さく、従って原子半径差が大きくなるので降伏強度が著
しく上昇し、Ｍｎ，Ｃｒは原子半径がＦｅのそれと極め
て近いので殆ど降伏強度を変化させなかったものと理解
できる。一方、積層欠陥エネルギーへの影響に関しては
必ずしも明瞭でないが、初期加工硬化後の転位構造の観
察結果から、Ｓｉ，Ｐは調査した添加量の範囲内で殆ど
積層欠陥エネルギーに影響を与えないが、Ｍｎ，Ｃｒは
これを低下させる傾向のあることが、始めて明らかとな
った。On the other hand, when Mn and Cr, which are not conventionally used as solid solution strengthening elements, are added, a) yield strength is hardly increased, b) tensile strength is increased, and c) as a result,
We obtained a very important new finding that the work hardening rate in the low strain region is increased by these additions. As a result of investigating these mechanisms, a) the yield strength is determined by the difference in atomic radius between the Fe element and the added X element, and increases as the difference in atomic radius increases. B) Work hardening rate is dislocation It was deeply related to the slip behavior of the above, and the basic principle was established that, when the stacking fault energy was lowered by the addition of the X element, the cross slip of dislocations became difficult and the work hardening rate increased.
According to this, the atomic radii of Si and P are much smaller than that of Fe, and hence the difference in atomic radii becomes larger, so that the yield strength increases remarkably. The atomic radii of Mn and Cr are very close to those of Fe, so that the yield strength changes almost. It can be understood that it was not made. On the other hand, although the influence on the stacking fault energy is not always clear, from the observation result of the dislocation structure after the initial work hardening, Si and P have almost no influence on the stacking fault energy within the investigated addition amount range, It became clear for the first time that Mn and Cr tended to reduce this.
【００１３】以上の機構により、Ｍｎ，Ｃｒを添加する
と降伏強度は殆ど変化せず、加工硬化率が増加して引張
強度が上昇したものと考える。このような特徴的な挙動
は、上述した本発明の目的、すなわち低ＹＰでかつ高Ｗ
Ｈの特性を達成するためには、従来のＳｉ，Ｐの添加だ
けでは困難であり、Ｍｎ，Ｃｒの添加が必須となること
を意味する。従って、本発明ではＭｎ，Ｃｒの積極的な
活用を発明の基本的な手段とした。ただしＭｎ，Ｃｒの
添加だけでは、所望の強度が得られない場合が発生した
り、製造コストが上昇したりするのでＳｉ，Ｐ添加との
併用も考える。According to the above mechanism, it is considered that when Mn and Cr are added, the yield strength hardly changes, the work hardening rate increases, and the tensile strength increases. Such characteristic behavior is due to the above-mentioned object of the present invention, that is, low YP and high W.
In order to achieve the characteristics of H, it means that it is difficult to add Si and P in the related art, and the addition of Mn and Cr is essential. Therefore, in the present invention, the positive use of Mn and Cr is the basic means of the invention. However, since the desired strength may not be obtained and the manufacturing cost may be increased only by adding Mn and Cr, the combined use with Si and P is also considered.
【００１４】第２に本発明者らは、Ｍｎ，Ｃｒの積極的
な添加により塗装焼付硬化性も向上するという新知見も
得た。本発明では、加工性を確保するためにＴｉやＮｂ
を単独および複合添加した極低炭素鋼をベースにする
が、この場合には一般的にＣやＮがＴｉやＮｂに固定さ
れるので焼付硬化能が無いか、あってもわずかである。
これは、Ｃ，ＮとＴｉ，Ｎｂとの親和力が非常に強いの
で、優れた加工性が得られるように原子％で（Ｔｉ＋Ｎ
ｂ）量を（Ｃ＋Ｎ）量より多くした場合には、固溶（Ｃ
＋Ｎ）が残存し難いためである。しかし、このような場
合でもＭｎ，Ｃｒを積極的に添加することによりＢＨ性
が付与できたという新しい事実は、ＴｉＣやＮｂＣの溶
解度積に変化の生じたことを示唆している。すなわち、
Ｍｎ，ＣｒはＣと引力の相互作用を有するため、ＴｉＣ
やＮｂＣと平衡するマトリックス中の固溶Ｃをより安定
化し、これらの析出物の溶解度積を増大させる結果、残
存する固溶Ｃ量を増加させＢＨ性を向上させたものと考
える。従って、Ｍｎ，Ｃｒの添加は塗装焼付硬化性を付
与するための新しい手段としても活用できる。Secondly, the present inventors have obtained a new finding that coating bake hardenability is also improved by positively adding Mn and Cr. In the present invention, Ti and Nb are used to secure workability.
Is used as a base, but in this case, since C and N are generally fixed to Ti and Nb, there is no bake hardenability, or there is little.
This is because the affinity between C and N and Ti and Nb is very strong, so that (Ti + N)
b) When the amount is larger than the (C + N) amount, the solid solution (C
+ N) is unlikely to remain. However, even in such a case, the new fact that the BH property can be imparted by positively adding Mn and Cr suggests that the solubility products of TiC and NbC have changed. That is,
Since Mn and Cr have an interaction of attractive force with C, TiC
It is considered that the solid solution C in the matrix in equilibrium with NbC and NbC is further stabilized and the solubility product of these precipitates is increased, and as a result, the amount of remaining solid solution C is increased and the BH property is improved. Therefore, addition of Mn and Cr can be utilized as a new means for imparting paint bake hardenability.
【００１５】また、塗装焼付性に寄与する固溶Ｃは、Ｂ
と同様に結晶粒界を強化するので、極低炭素鋼の欠点と
して知られている２次加工脆化の防止手段としても有効
である。また、２次加工脆化は粒界偏析したＰの存在に
より助長されることは良く知られているが、Ｍｎ，Ｃｒ
はＰと引力の相互作用があり、偏析するＰ量を低減する
ので、２次加工脆化の防止にも有効であるという知見も
得られた。The solid solution C which contributes to the baking property of the coating is B
Since the grain boundaries are strengthened similarly to the above, it is also effective as a means for preventing secondary work embrittlement, which is known as a drawback of ultra-low carbon steel. It is well known that secondary working embrittlement is promoted by the presence of P segregated at the grain boundaries.
Has an interaction between P and attractive force, and reduces the amount of segregated P, so that it was found that it is also effective in preventing embrittlement in secondary working.
【００１６】自動車などプレス成形部品の組立てには溶
接作業を効率良く行なわなければならず、そのためには
スポット溶接性が優れていることが重要である。一般
に、スポット溶接性は、溶接適性電流下限値が低電流で
あるほど優れていることが知られている。また、溶接適
性電流下限値は、鋼板の降伏強度が高いものほど低くて
済むこともよく知られている。これは鋼板の降伏強度が
高いと、スポット溶接時に電極からの加圧によって局部
変形が起こり難いために、電極と鋼板との接触面積が小
さくなることに起因する。本発明鋼は、上述した通りプ
レス時の耐面歪性の観点からＹＰを極力低下せしめるよ
う設計されている。しかしながら、ＷＨが非常に高いた
めプレス成形後の降伏強度は通常のＰやＳｉを用いた高
強度冷延鋼板のそれと比べて同程度となり、スポット溶
接性と耐面歪性を両立することができる。In order to assemble a press-molded part such as an automobile, the welding work must be carried out efficiently, and for that purpose, it is important that the spot weldability is excellent. In general, it is known that the spot weldability is superior as the lower limit of the welding aptitude current is lower. It is also well known that the lower limit of the welding aptitude current is required to be lower as the yield strength of the steel sheet is higher. This is because when the yield strength of the steel sheet is high, local deformation is less likely to occur due to the pressure applied from the electrode during spot welding, so that the contact area between the electrode and the steel sheet becomes small. As described above, the steel of the present invention is designed to reduce YP as much as possible from the viewpoint of surface strain resistance during pressing. However, since the WH is very high, the yield strength after press forming is about the same as that of the high-strength cold-rolled steel sheet using ordinary P or Si, and both spot weldability and surface strain resistance can be achieved. .
【００１７】さらにスポット溶接部には、自動車走行時
の繰り返し応力による疲労破壊が発生することがあり、
スポット溶接後の疲労強度に優れていることも極めて重
要な課題である。本発明鋼においては、Ｍｎ，Ｃｒを積
極的に添加するので、スポット溶接による変態組織が微
細になり、スポット溶接部の疲労強度に著しく優れるこ
とが判明した。これに対して、従来のようなＰやＳｉを
添加した高強度鋼板においては、スポット溶接性、溶接
後の疲労強度が著しく低い。このような鋼板において
は、降伏強度は高いものの、溶接時の加熱によって著し
く結晶粒が粗大化することが特性劣化の主たる原因であ
ると思われる。Further, in the spot welded portion, fatigue fracture may occur due to repetitive stress when the vehicle is running,
Excellent fatigue strength after spot welding is also a very important issue. In the steel of the present invention, since Mn and Cr are positively added, the transformation structure by spot welding becomes fine, and it has been found that the fatigue strength of the spot welded portion is remarkably excellent. On the other hand, in a conventional high-strength steel sheet to which P or Si is added, spot weldability and fatigue strength after welding are extremely low. In such a steel sheet, although the yield strength is high, it is considered that the main cause of the characteristic deterioration is that the crystal grains are remarkably coarsened by heating during welding.
【００１８】自動車の車体などの防錆化が進む今日、表
面処理鋼板化の動向は著しい。鋼板の表面処理法は、電
気メッキと溶融メッキに大別される。前者は、一般的に
鋼板の種類を問わずメッキ密着性は良好であるが、厚目
付けが困難で、コスト高となる問題がある。一方後者
は、前者の欠点はないが、鋼板の種類によっては、メッ
キ密着性が劣化したり、Ｆｅ−Ｚｎの合金化反応が大き
く影響されたりする。本発明者らは、従来鋼において強
化元素として多用されているＳｉ，Ｐの添加量を抑制
し、Ｍｎ，Ｃｒを活用する本発明鋼が、とくにゼンジマ
ー方式の連続溶融亜鉛メッキプロセスによる合金化溶融
亜鉛メッキ鋼板の製造において、次のような長所を有す
る新知見も得た。すなわち、Ｓｉ，ＰはＺｎとＦｅの合
金化反応を抑制するため、これらの元素を多量に含む鋼
板を製造するときには、ラインスピードを減少させ生産
性を低下せざるをえなかった。また、Ｓｉの添加はメッ
キ密着性を劣化し、プレス成形時に種々の問題を生じ
た。一方、Ｍｎ，Ｃｒの添加は、このような悪影響を持
たないことが判明した。機構は必ずしも明らかでない
が、ａ）表面に偏析するＭｎが還元後に残る酸化物の種
類と形態を変え、メッキ密着性を改善したり、ｂ）Ｍｎ
やＣｒがＰとの相互作用を通して粒界偏析するＰ量を低
減し、合金化反応を正常にしたりする役割があるものと
推察される。この点も、従来法の問題点の解決手段とし
て活用した。本発明は、このような思想と新知見に基づ
いて構築されたものである。Nowadays, with the progress of rust prevention of automobile bodies and the like, the trend toward the use of surface-treated steel sheets is remarkable. Surface treatment methods for steel sheets are roughly classified into electroplating and hot dip coating. The former generally has good plating adhesion regardless of the type of steel sheet, but has a problem that it is difficult to make a thick basis weight and the cost becomes high. On the other hand, the latter does not have the drawback of the former, but depending on the type of steel sheet, the plating adhesion is deteriorated or the Fe-Zn alloying reaction is greatly affected. The present inventors have found that the steel of the present invention which suppresses the addition amounts of Si and P, which are often used as strengthening elements in conventional steel, and utilizes Mn and Cr, is alloyed and melted by a continuous hot dip galvanizing process of a Zenzimer system. In the manufacture of galvanized steel sheets, we also gained new knowledge with the following advantages. That is, since Si and P suppress the alloying reaction between Zn and Fe, when producing a steel sheet containing a large amount of these elements, the line speed must be reduced and productivity must be reduced. Further, the addition of Si deteriorates the adhesion of the plating and causes various problems during press molding. On the other hand, it has been found that the addition of Mn and Cr does not have such an adverse effect. Although the mechanism is not always clear, a) Mn segregated on the surface changes the type and morphology of the oxide remaining after reduction to improve plating adhesion, and b) Mn.
It is presumed that Cr and Cr have a role of reducing the amount of P segregated at the grain boundaries through the interaction with P and normalizing the alloying reaction. This point was also utilized as a solution to the problems of the conventional method. The present invention is constructed based on such an idea and new knowledge.
【００１９】以下に、本発明において成分および特性値
を上述のように限定した理由についてさらに説明する。 Ｃ量：Ｃは成品の材質特性を決定する極めて重要な元素
である。本発明は真空脱ガス処理をした極低炭素鋼を前
提とするが、Ｃが０．０００３％未満になると粒界強度
が低下し、２次加工脆性が発生し、かつ製造コストが著
しく増加する。一方、Ｃ量が０．０１％超になると強度
は上昇するが、成形性が著しく低下するので、その範囲
を０．０００３％〜０．０１％とする。The reasons for limiting the components and characteristic values in the present invention as described above will be further described below. C content: C is a very important element that determines the material properties of the product. The present invention is premised on a vacuum degassed ultra low carbon steel, but if C is less than 0.0003%, the grain boundary strength decreases, secondary work embrittlement occurs, and the manufacturing cost significantly increases. . On the other hand, if the C content exceeds 0.01%, the strength increases, but the formability remarkably decreases, so the range is made 0.0003% to 0.01%.
【００２０】Ｓｉ量：Ｓｉは、安価に強度を上昇する元
素として知られており、その添加量は狙いとする強度レ
ベルに応じて変化させればよく、下限は０．００５でよ
い。一方、添加量を多くするとＹＰが上昇し過ぎてプレ
ス時に面歪が発生する。更に化成処理性や溶融亜鉛メッ
キの密着性の低下、合金反応の遅延による生産性の低下
などの問題が発生する。また、スポット溶接部の耐疲労
特性を劣化させる。従ってその上限を０．８％とした。Si amount: Si is known as an element that increases the strength at a low cost, and the addition amount may be changed according to the target strength level, and the lower limit may be 0.005. On the other hand, when the addition amount is increased, YP rises too much and surface strain occurs during pressing. Further, problems such as deterioration of chemical conversion treatment property and adhesiveness of hot dip galvanizing, and deterioration of productivity due to delay of alloy reaction occur. It also deteriorates the fatigue resistance of the spot welds. Therefore, the upper limit is set to 0.8%.
【００２１】Ｍｎ量：Ｍｎは、降伏強度をあまり上昇さ
せず強度を増加させる有効な固溶体強化元素であり、か
つ焼付硬化能を付与したり、２次加工脆性を防止した
り、更にはスポット溶接部の耐疲労特性を向上させ、か
つ化成処理性や溶融亜鉛メッキ性を改善する効果も有す
るので、本発明では積極的に添加する。しかし余り多量
に添加すると、降伏強度が著しく増加したり延性が低下
したりするので、その上限を３．０％とする。下限はＣ
ｒ含有量との兼ね合いで決めるが０．３％以上は必要で
ある。Mn content: Mn is an effective solid solution strengthening element that does not significantly increase the yield strength and increases the strength, imparts bake hardenability, prevents secondary work brittleness, and further spot welding. Since it has the effect of improving the fatigue resistance of the part and improving the chemical conversion treatment property and the hot dip galvanizing property, it is positively added in the present invention. However, if added in an excessively large amount, the yield strength remarkably increases and the ductility decreases, so the upper limit is made 3.0%. The lower limit is C
It is determined in consideration of the r content, but 0.3% or more is necessary.
【００２２】Ｃｒ量：ＣｒもＭｎも同様、降伏強度をほ
とんど上昇させず強度を増加させる有効な元素であり、
かつ焼付硬化能を付与したり、２次加工脆性を防止する
だけでなく、スポット溶接後の疲労強度を向上させるの
で、本発明では積極的に利用する。しかしＣｒが多くな
ると熱延板の酸洗性が低下したり、製品板の化成処理性
が劣化したりするので、上限を３％とする。上記したＭ
ｎとＣｒは同様の機能目的で添加するが、これらの元素
による適切な諸特性をうるためにはＭｎ＋Ｃｒを０．５
％以上とすることが好ましい。Cr content: Cr and Mn are both effective elements that increase the yield strength with almost no increase in yield strength.
In addition to imparting bake hardenability and preventing secondary work brittleness, it improves fatigue strength after spot welding, so it is actively used in the present invention. However, if the amount of Cr is large, the pickling property of the hot-rolled sheet deteriorates and the chemical conversion treatment property of the product sheet deteriorates, so the upper limit is made 3%. M mentioned above
n and Cr are added for the same function purpose, but in order to obtain appropriate characteristics by these elements, Mn + Cr should be 0.5
% Or more is preferable.
【００２３】Ｐ量：Ｐは安価に強度を上昇する元素とし
て知られており、従来の固溶体強化した高強度鋼板にお
いては多用されている。しかし添加量が０．１２％超に
なると、たとえ本発明のようにＭｎ，Ｃｒを積極的に添
加しても、ａ）降伏強度が上昇しすぎてプレス時に面形
状不良を引き起こしたり、ｂ）２次加工脆化が生じたり
する。また、ｃ）連続溶融亜鉛メッキ時に合金化反応が
極めて遅くなり、生産性が低下する。さらに、ｄ）スポ
ット溶接後の疲労強度が著しく低下する。従って、その
上限値を０．１２％とする。P content: P is known as an element that increases the strength at a low cost, and is often used in conventional solid solution strengthened high strength steel sheets. However, if the addition amount exceeds 0.12%, even if Mn and Cr are positively added as in the present invention, a) the yield strength is excessively increased to cause a surface shape defect during pressing, or b). Secondary processing embrittlement may occur. Further, c) the alloying reaction during continuous hot-dip galvanizing becomes extremely slow, and the productivity is reduced. Furthermore, d) the fatigue strength after spot welding is significantly reduced. Therefore, the upper limit value is set to 0.12%.
【００２４】Ｓ量：Ｓは低い方が好ましいが、０．００
１％未満になると製造コストが上昇するので、これを下
限値とする。一方、０．０１５％超になるとＭｎＳやＴ
ｉＳなどの硫化物が数多く析出し、加工性が劣化するの
で、これを上限値とする。S amount: S is preferably low, but 0.00
If it is less than 1%, the production cost increases, so this is set as the lower limit. On the other hand, if it exceeds 0.015%, MnS or T
Since a large number of sulfides such as iS precipitate and workability deteriorates, this is set as the upper limit.
【００２５】Ａｌ量：Ａｌは脱酸調整に使用するが、
０．００５％未満ではＴｉの添加歩留が低下する。一
方、０．１％超になるとコスト上昇を招く。Al amount: Al is used for deoxidation adjustment,
If it is less than 0.005%, the yield of Ti addition is reduced. On the other hand, if it exceeds 0.1%, the cost increases.
【００２６】Ｔｉ，Ｎｂ量：Ｔｉ，Ｎｂは、Ｃ，Ｎの一
部あるいは全部をＴｉＣ，ＴｉＮ，あるいはＮｂ（Ｃ
Ｎ）として固定することにより、極低炭素鋼の加工性と
非時効性を確保する役割を有する。そのためにＴｉ＊＝
Ｔ．Ｔｉ−３．４２Ｎとしたときに、２≦（Ｔｉ＊＋
０．５２Ｎｂ）／Ｃ≦２０とする事が好ましい。その
際、各元素の含有範囲は０．００３〜０．１５％とする
のがよく、０．００５％未満ではその添加効果が現れ
ず、一方、０．１％以上となると著しい合金コストの上
昇を招くからである。Amount of Ti, Nb: Ti, Nb is TiC, TiN, or Nb (C
By fixing as N), it has a role of ensuring workability and non-aging property of the ultra-low carbon steel. Therefore, Ti * =
T. When Ti−3.42N, 2 ≦ (Ti * ++
It is preferable that 0.52 Nb) / C ≦ 20. At that time, it is preferable that the content range of each element is 0.003 to 0.15%, and if it is less than 0.005%, the addition effect does not appear, while if it is 0.1% or more, the alloy cost increases significantly. Because it invites.
【００２７】なお、Ｎ量は特に規定しないが低い方が好
ましい。その量が多くなると過剰のＴｉやＡｌの添加が
必要になったり、加工性が劣化したりするので、０．０
０６０％以下とする。また本発明においてＢは、必要に
応じて添加してもよく、この際Ｎが事前に固定されてい
る場合には結晶粒界に偏析し、２次加工脆化の防止に有
効である。しかし０．０００１％未満では、その効果が
不充分であるり、０．００２０％超になると添加コスト
の上昇やスラブ割れの原因となるので添加する場合はこ
の範囲とするのがよい。The N content is not particularly specified, but a lower content is preferable. If the amount increases, excessive addition of Ti or Al becomes necessary, or workability deteriorates.
060% or less. In the present invention, B may be added as necessary, and when N is fixed in advance at this time, it segregates at the grain boundaries and is effective in preventing secondary work embrittlement. However, if it is less than 0.0001%, the effect is insufficient, and if it exceeds 0.0020%, it causes an increase in addition cost and slab cracking. Therefore, it is preferable to set this range when adding.
【００２８】本発明は以上のような成分構成の高強度冷
延鋼板は熱間圧延、冷間圧延、焼鈍等各工程を通常の方
法で経て製造される。しかし、スラブを熱延するに際し
ては、その仕上げ温度を、成品板の加工性を確保すると
いう観点からＡｒ3 −１００℃以上とし、また、巻き取
り温度を室温から７５０℃とするのが好ましい。According to the present invention, the high-strength cold-rolled steel sheet having the above-mentioned composition is manufactured by the usual methods such as hot rolling, cold rolling and annealing. However, when hot rolling the slab, the finishing temperature, from the viewpoint of securing the workability of-products plate and Ar 3 -100 ° C. or more, and preferably set to 750 ° C. The coiling temperature from room temperature.
【００２９】この様にして本発明によれば、３５〜５０
kgf/mm2 の引張り強さ（ＴＳ）を有し、降伏強度（Ｙ
Ｐ）を１５〜２５kgf/mm2 、降伏比（ＹＲ＝ＹＰ／Ｔ
Ｓ）を０．５５以下の低ＹＲとし、平均ｒ値が１．５以
上、伸び（Ｔ．Ｅｌ）が３５％以上で、プレス成形時の
ＹＰ−Ｅｌが０．２％以下であり、また加工時あるいは
加工後の衝撃に因る割れ発生がない２次加工性に優れ、
かつ塗装焼付時の焼付硬化量（ＢＨ）が２〜５kgf/mm2
であり、成形後面形状性が良好で、さらに優れた耐デン
ト性を具備し、しかもスポット溶接部の疲労強度に優れ
た高強度冷延鋼板を得ることができる。Thus, according to the present invention, 35-50
kgf / mm 2 tensile strength (TS) and yield strength (Y
P) of 15 to 25 kgf / mm 2 , yield ratio (YR = YP / T
S) is low YR of 0.55 or less, the average r value is 1.5 or more, the elongation (T.El) is 35% or more, and the YP-El during press molding is 0.2% or less, and Excellent secondary workability that does not cause cracking due to impact during or after processing,
Moreover, the bake hardening amount (BH) during baking is 2 to 5 kgf / mm 2
Thus, it is possible to obtain a high-strength cold-rolled steel sheet having good surface shape after forming, excellent dent resistance, and excellent fatigue strength of spot welds.
【００３０】[0030]
【実施例】表１に示す組成を有する鋼を溶製し、スラブ
加熱温度１１５０℃、仕上げ温度９１０℃、巻き取り温
度を６５０℃で熱延圧延し、得られた鋼板を圧下率８０
％で冷間圧延してから８４０℃で焼鈍、調質圧延し製品
とした。この冷延鋼板よりＪＩＳ５号引張試験片を採取
し引張試験に供した。またスポット溶接を施した時の溶
接適性電流下限値は、２％の引張変形を与えた材料を用
いて評価した。溶接強度は、溶接時間：８サイクル、加
圧力：１９０kgf ，電流８kAの条件で溶接後、引張剪断
強度によって評価した。さらに疲労特性は、スポット溶
接条件を調節することによりナゲット径がすべて５．０
mmとなるようにして、引張剪断疲労試験片を作製し、こ
れを完全片振りの疲労試験に供した。得られた結果を表
２に示す。EXAMPLE Steels having the compositions shown in Table 1 were melted and hot-rolled at a slab heating temperature of 1150 ° C., a finishing temperature of 910 ° C., and a winding temperature of 650 ° C.
% Cold-rolled, then annealed at 840 ° C. and temper-rolled to obtain a product. A JIS No. 5 tensile test piece was sampled from this cold rolled steel sheet and subjected to a tensile test. In addition, the lower limit value of the welding suitability current when performing spot welding was evaluated using a material that was given a tensile deformation of 2%. The welding strength was evaluated by tensile shear strength after welding under the conditions of welding time: 8 cycles, applied pressure: 190 kgf, and current 8 kA. Furthermore, as for fatigue characteristics, the nugget diameter is all 5.0 by adjusting spot welding conditions.
A tensile shear fatigue test piece was prepared so as to have a thickness of mm, and this was subjected to a fatigue test of perfect swing. The obtained results are shown in Table 2.
【００３１】[0031]
【表１】 [Table 1]
【００３２】[0032]
【表２】 表２から明らかなように、本発明鋼板は、従来材に比
し、降伏強度（ＹＰ）が低く、伸び（Ｅｌ）や平均ｒ値
が高い。また、ＢＨ性や２次加工性にも優れている。さ
らに、スポット溶接性、ならびにスポット溶接後の疲労
強度にも優れていることが分かる。これに対して本発明
範囲を外れた比較鋼では、各機械的性質、スポット溶接
性および溶接後の耐疲労特性に劣っていた。[Table 2] As is clear from Table 2, the steel sheet of the present invention has a lower yield strength (YP), a higher elongation (El), and a higher average r value than the conventional materials. Further, it is also excellent in BH property and secondary workability. Further, it can be seen that the spot weldability and the fatigue strength after spot welding are also excellent. On the other hand, the comparative steels out of the range of the present invention were inferior in each mechanical property, spot weldability and fatigue resistance after welding.
【００３３】[0033]
【発明の効果】以上の説明から明らかなように、本発明
によればＭｎ，Ｃｒ等を有効に活用したＴｉ，Ｎｂ含有
極低炭素鋼板賭することにより、従来にない加工性と共
にスポット溶接部の疲労強度に優れた高強度冷延鋼板が
得られる。また、本発明の鋼板は、ＢＨ性や２次加工性
に優れ自動車のフレームや容器用材料等に広範囲に使用
することができる。As is apparent from the above description, according to the present invention, by betting a Ti / Nb-containing ultra-low carbon steel sheet in which Mn, Cr, etc. are effectively utilized, a spot welded portion with unprecedented workability can be obtained. A high-strength cold-rolled steel sheet having excellent fatigue strength can be obtained. Further, the steel sheet of the present invention is excellent in BH property and secondary workability and can be widely used as a material for automobile frames and containers.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平２−163323（ＪＰ，Ａ) 特開 昭63−317649（ＪＰ，Ａ) 特開 昭63−317648（ＪＰ，Ａ) 特開 昭63−310939（ＪＰ，Ａ) 特開 平２−163318（ＪＰ，Ａ) ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-2-163323 (JP, A) JP-A-63-317649 (JP, A) JP-A-63-317648 (JP, A) JP-A-63- 310939 (JP, A) JP-A-2-163318 (JP, A)
Claims (2)
て、 Ｔｉ＊＝Ｔ．Ｔｉ−３．４２Ｎの時２≦（Ｔｉ＊＋０．
５２Ｎｂ）／Ｃ≦２０になるように含有し、残部Ｆｅお
よび不可避不純物からなることを特徴とするスポット溶
接部の疲労強度に優れた良加工性高強度冷延鋼板。1. By weight, C: 0.0003 to 0.01%, Si: 0.005 to 0.8%, Mn: 0.3 to 3.0%, Cr: 0.01 to 3.0%. And Mn + Cr to be 0.5% or more, P: 0.001 to 0.12%, S: 0.001 to 0.015%, Al: 0.005 to 0.10%, and Ti: 0.003 to 0.10% and Nb: 0.003 to 0.10%, one or two of which Ti * = T. When Ti−3.42N, 2 ≦ (Ti * + 0.
52 Nb) / C ≦ 20, and the balance Fe and unavoidable impurities make the workability and high strength cold rolled steel sheet excellent in fatigue strength of spot welds.
て、 Ｔｉ＊＝Ｔ．Ｔｉ−３．４２Ｎの時２≦（Ｔｉ＊＋０．
５２Ｎｂ）／Ｃ≦２０になるように含有し、残部Ｆｅお
よび不可避不純物からなることを特徴とするスポット溶
接部の疲労強度に優れた良加工性高強度冷延鋼板。2. By weight, C: 0.0003 to 0.01%, Si: 0.005 to 0.5%, Mn: 0.3 to 3.0%, Cr: 0.01 to 3.0%. , And Mn + Cr to be 0.5% or more, P: 0.001 to 0.12%, S: 0.001 to 0.015%, Al: 0.005 to 0.10%, B: 0.0001 to 0.002% Further, one or two of Ti: 0.003 to 0.10% and Nb: 0.003 to 0.10%, Ti * = T. When Ti−3.42N, 2 ≦ (Ti * + 0.
52 Nb) / C ≦ 20, and the balance Fe and unavoidable impurities make the workability and high strength cold rolled steel sheet excellent in fatigue strength of spot welds.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3341214A JP2503338B2 (en) | 1991-12-24 | 1991-12-24 | Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot welds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3341214A JP2503338B2 (en) | 1991-12-24 | 1991-12-24 | Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot welds |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05263184A JPH05263184A (en) | 1993-10-12 |
| JP2503338B2 true JP2503338B2 (en) | 1996-06-05 |
Family
ID=18344266
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3341214A Expired - Fee Related JP2503338B2 (en) | 1991-12-24 | 1991-12-24 | Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot welds |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2503338B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1223695C (en) | 1998-12-07 | 2005-10-19 | 杰富意钢铁株式会社 | High strength cold rolled steel plate and its producing method |
| KR101758557B1 (en) | 2015-06-05 | 2017-07-18 | 주식회사 포스코 | High-strength thin steel sheet having excellent drawability and bake hardenability and method for manufacturing the same |
| KR101819358B1 (en) | 2016-08-12 | 2018-01-17 | 주식회사 포스코 | High-strength thin steel sheet having excellent formability and method for manufacturing the same |
| KR102218464B1 (en) | 2019-06-17 | 2021-02-19 | 주식회사 포스코 | Method of manufacturing ultra low carbon steel having high formablity and excellent surface qualities |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02111841A (en) * | 1988-10-19 | 1990-04-24 | Kawasaki Steel Corp | Cold rolled steel sheet excellent in workability and having baking hardenability and hot dip zinc galvanizing steel sheet |
| JPH02118029A (en) * | 1988-10-26 | 1990-05-02 | Sumitomo Metal Ind Ltd | Manufacture of cold rolled steel sheet with superior formability |
| JPH03199342A (en) * | 1989-12-28 | 1991-08-30 | Kawasaki Steel Corp | Sheet metal for working excellent in durability in weld zone |
-
1991
- 1991-12-24 JP JP3341214A patent/JP2503338B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05263184A (en) | 1993-10-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6692584B2 (en) | High tensile cold-rolled steel sheet excellent in ductility and in strain aging hardening properties, and method for producing the same | |
| WO1996030555A1 (en) | Ultralow-carbon cold-rolled sheet and galvanized sheet both excellent in fatigue characteristics and process for producing both | |
| US7608156B2 (en) | High strength cold rolled steel sheet and method for manufacturing the same | |
| EP3919645A1 (en) | Hot-pressed member, cold-rolled steel sheet for hot-pressed member, and methods respectively for producing these products | |
| JP3365632B2 (en) | High-strength cold-rolled steel sheet and hot-dip galvanized high-strength cold-rolled steel sheet having good formability and methods for producing them | |
| KR102153194B1 (en) | Ultra high strength and high ductility cold rolled steel sheet with superior resistance to liquid metal embrittlment(lme) cracking, plated steel sheet and method for manufacturing the same | |
| JP2503338B2 (en) | Good workability and high strength cold rolled steel sheet with excellent fatigue strength of spot welds | |
| JP3016636B2 (en) | High strength cold rolled steel sheet with good formability | |
| JP3238211B2 (en) | Manufacturing method of cold rolled steel sheet or hot-dip galvanized cold rolled steel sheet with excellent bake hardenability and non-aging property | |
| JP2002206139A (en) | High strength galvannealed steel sheet and high strength galvanized steel sheet having excellent plating adhesion and press formability and production method therefor | |
| JP2980785B2 (en) | Cold-rolled steel sheet or hot-dip galvanized cold-rolled steel sheet excellent in bake hardenability and formability, and methods for producing them | |
| JP3719025B2 (en) | Cold-rolled steel sheet for deep drawing with excellent fatigue resistance | |
| JPH06122940A (en) | Cold rolled steel sheet and galvanized cold rolled steel sheet having excellent baking hardenability and also cold monaging property and production thereof | |
| JP3044641B2 (en) | Room temperature non-ageing cold rolled steel sheet with remarkably high paint bake hardening performance | |
| JPH09310149A (en) | Cold rolled steel sheet excellent in deep drawability, spot weldability and punchability and its production | |
| JP3309771B2 (en) | Alloyed hot-dip galvanized steel sheet and method for producing the same | |
| JPH05255807A (en) | High strength cold rolled steel sheet and calvanized high strength cold rolled steel sheet excellent in formability and their manufacture | |
| JP2620444B2 (en) | High strength hot rolled steel sheet excellent in workability and method for producing the same | |
| JP3350096B2 (en) | Cold-rolled steel sheet or hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability and formability, and methods for producing them | |
| JP2556633B2 (en) | Method for producing cold-rolled steel sheets with excellent hot-dip galvanizing properties | |
| US20230295759A1 (en) | Steel sheet having excellent formability and strain hardening rate | |
| JPH0578783A (en) | High strength cold rolled steel sheet having satisfactory formability | |
| JPH05263185A (en) | High strength cold rolled steel sheet and galvanized high strength cold rolled steel sheet good in formability, and their manufacture | |
| JP2002003994A (en) | High strength steel sheet and high strength galvanized steel sheet | |
| JP2503338C (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 19960116 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080402 Year of fee payment: 12 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090402 Year of fee payment: 13 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090402 Year of fee payment: 13 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100402 Year of fee payment: 14 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110402 Year of fee payment: 15 |
|
| LAPS | Cancellation because of no payment of annual fees |