JPH0123530B2 - - Google Patents
Info
- Publication number
- JPH0123530B2 JPH0123530B2 JP10686681A JP10686681A JPH0123530B2 JP H0123530 B2 JPH0123530 B2 JP H0123530B2 JP 10686681 A JP10686681 A JP 10686681A JP 10686681 A JP10686681 A JP 10686681A JP H0123530 B2 JPH0123530 B2 JP H0123530B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- cold
- deep drawability
- strength
- secondary workability
- 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 17
- 239000010959 steel Substances 0.000 claims description 17
- 238000000137 annealing Methods 0.000 claims description 13
- 239000010960 cold rolled steel Substances 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 235000021110 pickles Nutrition 0.000 claims 1
- 239000006104 solid solution Substances 0.000 description 12
- 238000000034 method Methods 0.000 description 11
- 239000003973 paint Substances 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 238000005097 cold rolling Methods 0.000 description 5
- 238000005098 hot rolling Methods 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 229910000655 Killed steel Inorganic materials 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000010422 painting Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910001335 Galvanized steel Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000008397 galvanized steel Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000009849 vacuum degassing Methods 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
Description
本発明は深絞り性と２次加工性の優れた実質的
にフエライトとパーライトの組織からなる高強度
冷延鋼板の連続焼鈍による製造法に関するもので
ある。
車体重量の低減や安全性の向上のため、自動車
用冷延鋼板は高強度鋼板への転換が急速に進めら
れている。最近の自動車への高強度冷延鋼板の採
用は、強度部材のみならず外板、内板のかなり成
形性の厳しい部品へと移行しつつある。従つて、
内・外板等に用いられる鋼板として要求される材
質特性は、低降伏点であること、降伏点伸びがな
いこと、張出し性、深絞り性が優れていること、
２次加工性に優れていること、さらには塗装焼付
硬化性に優れていることが条件となる。ここで、
２次加工性とは、深絞り加工品に２次的な加工を
施す際に脆性的な破壊が生じるか否かという材料
特性を示すもので、２次的加工によつて脆性破壊
が生じない傾向を２次加工性に優れているとよ
ぶ。また、塗装焼付硬化性とは、プレス成形時に
は低降伏点であり、成形加工後の塗装ラインにお
ける200℃前後の熱処理によつて降伏点が上昇す
る材料特性を示すもので、その降伏点の上昇量が
多いほど塗装焼付硬化性に優れているとよぶ。塗
装焼付硬化性をよくするには、焼鈍後に固溶の
Ｃ，Ｎを適量残存させることが有効であるが、Ｃ
とＮの拡散の活性化エネルギーはＣの方が高く、
固溶Ｃを利用する方がより好ましい。
ところで、鋼を強化する方法としては、固溶体
強化が最も安価な方法である。従来の固溶体強化
による高強度冷延鋼板としてＰ添加したものがあ
り、例えば特公昭50−31090号公報において提案
されている。これはＰを0.05〜0.25％含有させて
強度とｎ値の向上を図り、一方Ｐ含有による２次
加工性の劣化を防ぐのにＣを0.02〜0.10％と比較
的多く含有させるとともに、Ｂ，Al，Siを含有
させたもので、高強度で２次加工性のすぐれた冷
延鋼板である。しかし、冷延後、箱焼鈍をした場
合も、連続焼鈍をした場合も引張り強度のみなら
ず降伏点が高く、深絞り性が十分にあるとはいえ
なかつた。
一般に深絞り性、張出し性を要求される高強度
冷延鋼板は箱焼鈍されるが、該箱焼鈍では冷却速
度が非常に遅いので、焼鈍済鋼板中の固溶Ｃが極
めて低く塗装焼付硬化性を具備させることは困難
である。また、焼付きの点から700℃以上の温度
で焼鈍することは難しく、深絞り性が確保しにく
い。さらには生産効率上にも問題がある。
ところで、連続焼鈍法でＰを含有した高強度冷
延鋼板の値（深絞り性）を高めるには炭素含有
量を低減することが有効な方法の１つであるが、
Ｐは鋼を脆化させ、この脆化は特に炭素含有量が
少ないほど顕著であるといわれており、例えば
N.P・Allenによる鉄の機械的性質に及ぼす溶質
元素の影響（Iron and Its Dilute Solid
Solutions，1963年、271〜314頁）に関する報文
がある。
そこで、本発明者らは炭素含有量を0.01％以下
に低減したAlキルド鋼にＰを強化元素として含
有しても、２次加工性の問題がなく、連続焼鈍に
よつて深絞り性に優れ、かつ塗装焼付硬化性も良
好な高強度冷延鋼板を製造する方法につき検討し
たところ、ＢをＮ量と関係をもたせて含有せしめ
Ｎを固定して非時効化する一方、固溶Ｂとして存
在させ、熱間圧延後の冷却速度およびその後の捲
取温度を規定してＢ炭化物の形成を防ぎ固溶Ｂを
確保すると、２次加工性が非常に改善されてよく
なることが明らかとなつた。また、その熱間圧延
以降の工程条件は深絞り性の向上という相乗効果
も有する。
本発明の要旨とするところは以下の通りであ
る。Ｃ：0.01％以下、Mn：0.10〜1.50％、Si：
1.0％以下、Ｐ：0.04〜0.12％、Ｓ：0.015％以下、
酸可溶Al：0.005〜0.070％、Ｎ：0.0060％以下、
Ｂ：11／14Ｎ％＜Ｂ％＜11／14Ｎ＋0.060％、残部が鉄
および不可避的不純物からなる鋼を鋼片とした
後、Ar3点以上の温度で仕上げ圧延し、続いて20
℃／sec以上の冷却速度で冷却し、680℃以下で巻
取り、その後酸洗し、50％以上の圧下率で冷間圧
延した後、700〜Ac3の温度範囲内で10秒〜10分
間均熱し、冷却することを特徴とする連続焼鈍に
よる深絞り性と２次加工性に優れた高強度冷延鋼
板の製造法。
次に本発明の限定理由について述べる。
ＣはＰ添加による２次加工性の劣化を防ぐため
に有効な元素といわれているがその量が増えると
ｒ値を劣化させるために上限を0.01％とする。と
くに本発明のＰ添加Alキルド鋼においては炭素
量をできるだけ低減し、高値を確保するために
は0.008％未満の炭素含有量が好ましい。そして、
炭素量を低減したことによる２次加工脆性の問題
は、Ｂの添加や製造条件との組み合せによつて解
決するものでこの点については後に述べる。
MnはＳによる粒界の脆化を防止するために
0.10％以上を必要とする。Mnは高強度化のため
に有効な元素であるが、多過ぎると値を劣化さ
せるので上限を1.50％とする。なお強度の点から
は0.45〜1.0％の含有が好ましい。
Siは有効な強化元素であり、延性を向上させる
効果もある。しかし、添加量が多過ぎると２次加
工脆化を促進させるとともに塗装後の耐食性を劣
化させるために上限を1.0％とする。
Ｐは安価に強度を確保できる最も有効な固溶体
強化元素であり、強度付与のためには0.04％以上
が必要である。しかし、多過ぎると２次加工脆化
の危険性を増し、溶接性も損なうために上限を
0.12％とする。
Alは酸素による脆化を防ぐため、酸可溶Alと
して最低0.005％は必要であり、0.070％を超える
とアルミナ系介在物が増加して清浄度を劣化させ
る。
Ｎは固溶状態にあると塗装焼付硬化性には有効
であるが、室温での時効劣化が大きくなるため、
Ｂによつて固定する必要がある。しかし、0.0060
％を超えると固溶Ｎが残存しがちとなるので
0.0060％を上限とする。好ましくは0.0040％以下
とすることが望ましい。
Ｂは本発明の重要な構成要件であり、その第１
の作用効果であるＮの固定のためにＮと化学量論
的に当価なＢを添加する必要がある。第２の作用
効果である２次加工性の改善のためにはＢを固溶
状態としてＰよりも優先的に結晶粒界に偏析させ
る必要がある。しかし、あまり多量の添加は深絞
り性を劣化させる。従つてＢの添加量は
11／14Ｎ％＜Ｂ％11／14Ｎ＋0.0060％
に規制する。
Ｓは粒界を脆化させるため上限を0.015％とす
る。Ｓはできるだけ少ない方が好ましく、0.010
％以下にするとよい。なお、Ｓの固定はMn以外
にREM，Ca，Zrのような硫化物形成元素の添加
が有効である。
次に製造工程条件の限定理由を述べる。
本発明鋼は、転炉等により溶製されたのち真空
脱ガス処理によつて成分調整され、連続鋳造法ま
たは造塊―分塊法によつてスラブとされる。該ス
ラブは熱間圧延においてAr3点以上の温度で仕上
げ圧延され、その後20℃／sec以上の冷却速度で
冷却され、680℃以下で巻取られる。仕上げ温度
はAr3点未満では冷延―焼鈍後の深絞り性に好ま
しい集合組織が発達しにくくなる。仕上げ圧延後
の冷却速度と巻取温度は、熱延板のフエライト粒
の粗大化による深絞り性に有害な集合組織の発達
を抑えるため及びＢ炭化物の生成をできるだけ回
避し固溶Ｂを確保するとともに値を向上させる
ために圧延後の冷却速度は20℃／sec以上、巻取
温度は680℃以下を必要とする。冷却速度が20
℃／sec未満、巻取温度が680℃を超えると深絞り
性が劣化し、２次加工性に対するＢの効果が発揮
されない。なお、冷却方法は仕上圧延後ホツトラ
ンテーブルの前半部でできるだけ急冷するのが好
ましい。冷間圧延の圧下率は深絞り性を得るため
に50％以上を必要とする。できるだけ高い値を
得るには75〜85％の圧下率で冷延することが好ま
しい。冷延の方法としてはレバース方式よりもタ
ンデム方式の方が高値の確保には好ましい。
冷延されたコイルは次に連続焼鈍されるが、ま
ず均熱温度は700〜Ac3の範囲内とする。700℃未
満では再結晶が不十分であり、延性が劣る。Ac3
点を超えると深絞り性に好ましい集合組織が無秩
序化され、値が劣化する。次に保定時間は10秒
〜10分とするが、10秒未満の保定では再結晶が十
分でなく、また10分を超えると結晶粒が粗大化し
引張強さを低下させるためである。連続焼鈍後は
通常、過時効処理される。調質圧延は必要により
施されるが、その圧下率は0.5〜1.5％が好まし
い。
本発明によると連続焼鈍後の鋼板の組織はフエ
ライトとパーライトからなり、フエライト素地中
に深絞り性を劣化させるマルテンサイト等の焼入
組織は生成されていない。
本発明による方法で製造した冷延原板あるいは
冷延鋼板は亜鉛メツキ鋼板その他の表面処理鋼板
の素材としても利用できる。
次に本発明の実施例について説明する。
実施例
第１表の化学成分からなる鋼を同表に示すよう
な熱延条件、冷延条件および連続焼鈍条件により
板厚0.8mmの冷延鋼板を製造した。調質圧延は、
いずれも1.2％を施した。得られた鋼板の機械的
性質、値、常温での時効特性、塗装焼付硬化量
および２次加工性を第２表に示す。ここで、常温
での時効特性は、23℃にて６ケ月経過後における
鋼板の降伏点伸びの発生程度で評価した。塗装焼
付硬化量は、引張試験片を予め２％引張つた時の
応力と、除荷後に170℃で20分の塗装焼付処理に
相当する熱処理を行つた後再び引張つた時の降伏
応力との差で示した。２次加工性は、施削された
円板を適当な絞り比で３段絞りを行ないこのカツ
プを10℃の温度に保定した後、直ちにカツプの中
に円錐台形のポンチを押し込み、カツプの側壁に
脆性的割れが生じるか否かで判定した。脆性的割
れが発生しない限界の絞り比が高いほど耐２次加
工性に優れていることになる。
鋼Ａ〜Ｄは本発明による鋼板であり、引張強さ
が36〜47Kg／mm2の範囲で深絞り性を示す値が高
く、常温では降伏点伸びが発生しない。それにも
かかわらず約６Kg／mm2前後の高い塗装焼付硬化量
を有し、かつ２次加工性に優れている。一方、従
来法による炭素含有量の多い鋼板Ｅは値が低
く、極低炭素Alキルド鋼にＰのみを添加した鋼
板Ｆは２次加工脆化が顕著である。鋼ＧはＢ量が
不足し２次加工性はほとんど改善されない。鋼Ｈ
は低い仕上温度、熱延後のおそい冷却速度、高い
巻取温度のために値が非常に低い。
以上のように本発明法によれば、引張強さが35
Kg／mm2以上で高い値と６Kg／mm2程度の高い塗装
焼付硬化性を有し、かつ２次加工性に優れた高強
度冷延鋼板が製造できる。
The present invention relates to a method for producing a high-strength cold-rolled steel sheet, which has excellent deep drawability and secondary workability, and which consists essentially of a structure of ferrite and pearlite, by continuous annealing. In order to reduce vehicle weight and improve safety, cold-rolled steel sheets for automobiles are rapidly being replaced with high-strength steel sheets. In recent years, high-strength cold-rolled steel sheets are being used in automobiles not only for high-strength components, but also for outer and inner panels, which require considerably more formability. Therefore,
The material properties required for steel plates used for inner and outer panels include a low yield point, no elongation at yield point, and excellent stretchability and deep drawability.
The conditions are that it has excellent secondary workability and also that it has excellent paint bake hardenability. here,
Secondary workability refers to the material property of whether or not brittle fracture occurs when secondary processing is applied to a deep-drawn product. This tendency is called excellent secondary processability. In addition, paint bake hardenability refers to material properties that have a low yield point during press forming, and whose yield point increases when heat treated at around 200℃ on the painting line after forming. It is said that the larger the amount, the better the paint baking hardenability. In order to improve paint baking hardenability, it is effective to leave an appropriate amount of solid solution C and N after annealing.
The activation energy for diffusion of and N is higher for C,
It is more preferable to use solid solution C. By the way, solid solution strengthening is the cheapest method for strengthening steel. Conventional high-strength cold-rolled steel sheets made by solid solution strengthening include P-added steel sheets, which have been proposed, for example, in Japanese Patent Publication No. 31090/1983. This is done by containing 0.05 to 0.25% of P to improve strength and n-value, while containing a relatively large amount of C at 0.02 to 0.10% to prevent deterioration of secondary workability due to the presence of P. Containing Al and Si, it is a cold-rolled steel sheet with high strength and excellent secondary workability. However, both in the case of box annealing and in the case of continuous annealing after cold rolling, not only the tensile strength but also the yield point were high, and deep drawability could not be said to be sufficient. Generally, high-strength cold-rolled steel sheets that require deep drawability and stretchability are box annealed, but since the cooling rate in box annealing is very slow, the solid solution C in the annealed steel sheet is extremely low, making it difficult to harden by painting. It is difficult to provide this. Additionally, it is difficult to anneal at temperatures above 700°C due to seizure, and it is difficult to ensure deep drawability. Furthermore, there is also a problem in terms of production efficiency. By the way, one effective method to increase the value (deep drawability) of high-strength cold-rolled steel sheets containing P by continuous annealing is to reduce the carbon content.
P embrittles steel, and this embrittlement is said to be particularly pronounced as the carbon content decreases; for example,
Iron and Its Dilute Solid by NP Allen
Solutions, 1963, pp. 271-314). Therefore, the present inventors discovered that even if P is included as a strengthening element in Al-killed steel with a carbon content reduced to 0.01% or less, there is no problem in secondary workability and it has excellent deep drawability through continuous annealing. We investigated a method for manufacturing high-strength cold-rolled steel sheets that also have good paint bake hardenability, and found that B is contained in a relationship with the amount of N, and while N is fixed and non-aging, B exists as a solid solution. It has become clear that secondary workability can be greatly improved by regulating the cooling rate after hot rolling and the subsequent winding temperature to prevent the formation of B carbides and ensure solid solution B. Further, the process conditions after hot rolling also have a synergistic effect of improving deep drawability. The gist of the present invention is as follows. C: 0.01% or less, Mn: 0.10-1.50%, Si:
1.0% or less, P: 0.04-0.12%, S: 0.015% or less,
Acid-soluble Al: 0.005 to 0.070%, N: 0.0060% or less,
B: 11/14N%<B%<11/14N+0.060%, the balance is iron and unavoidable impurities. After making the steel into a billet, it is finish rolled at a temperature of A r3 point or higher, and then 20
Cooled at a cooling rate of ℃/sec or more, coiled at 680℃ or less, then pickled, cold rolled at a rolling reduction of 50% or more, and then heated within a temperature range of 700 to A c3 for 10 seconds to 10 minutes. A method for producing high-strength cold-rolled steel sheets with excellent deep drawability and secondary workability through continuous annealing characterized by soaking and cooling. Next, the reasons for the limitations of the present invention will be described. C is said to be an effective element for preventing deterioration of secondary workability due to P addition, but as its amount increases, the r value deteriorates, so the upper limit is set at 0.01%. In particular, in the P-added Al-killed steel of the present invention, a carbon content of less than 0.008% is preferred in order to reduce the carbon content as much as possible and ensure a high value. and,
The problem of secondary processing brittleness caused by reducing the amount of carbon can be solved by adding B and combining it with manufacturing conditions, and this point will be described later. Mn is used to prevent grain boundary embrittlement caused by S.
Requires 0.10% or more. Mn is an effective element for increasing strength, but too much Mn deteriorates the value, so the upper limit is set at 1.50%. Note that from the viewpoint of strength, the content is preferably 0.45 to 1.0%. Si is an effective reinforcing element and also has the effect of improving ductility. However, if the amount added is too large, it will promote embrittlement due to secondary processing and deteriorate the corrosion resistance after painting, so the upper limit is set at 1.0%. P is the most effective solid solution strengthening element that can secure strength at low cost, and 0.04% or more is required to impart strength. However, if the amount is too high, the risk of secondary processing embrittlement increases and weldability is also impaired, so the upper limit must be set.
Set at 0.12%. In order to prevent embrittlement due to oxygen, a minimum of 0.005% of Al is required as acid-soluble Al, and if it exceeds 0.070%, alumina-based inclusions will increase and the cleanliness will deteriorate. When N is in a solid solution state, it is effective for paint baking hardenability, but aging deterioration at room temperature becomes large.
It is necessary to fix it by B. But 0.0060
%, solid solution N tends to remain.
The upper limit is 0.0060%. The content is preferably 0.0040% or less. B is an important component of the present invention, and the first
It is necessary to add B in a stoichiometrically equivalent amount to N in order to fix N, which is the effect of In order to improve the secondary workability, which is the second effect, it is necessary to make B in a solid solution state and segregate it preferentially over P at the grain boundaries. However, adding too much will deteriorate deep drawability. Therefore, the amount of B added is regulated to 11/14N%<B%11/14N+0.0060%. Since S embrittles grain boundaries, the upper limit is set to 0.015%. It is preferable that S be as small as possible, 0.010
% or less. Note that, in addition to Mn, addition of sulfide-forming elements such as REM, Ca, and Zr is effective for fixing S. Next, the reasons for limiting the manufacturing process conditions will be described. The steel of the present invention is melted in a converter or the like, then its composition is adjusted by vacuum degassing treatment, and it is made into a slab by a continuous casting method or an ingot-blowing method. The slab is finish rolled during hot rolling at a temperature of A r3 or higher, then cooled at a cooling rate of 20°C/sec or higher, and coiled at a temperature of 680°C or lower. If the finishing temperature is below the A r3 point, it will be difficult to develop a texture that is favorable for deep drawability after cold rolling and annealing. The cooling rate and coiling temperature after finish rolling are determined in order to suppress the development of texture that is harmful to deep drawability due to coarsening of ferrite grains in the hot rolled sheet, and to avoid the formation of B carbides as much as possible to ensure solid solution B. At the same time, in order to improve the value, the cooling rate after rolling must be at least 20°C/sec, and the coiling temperature must be at most 680°C. Cooling rate is 20
When the coiling temperature exceeds 680° C./sec and the winding temperature exceeds 680° C., deep drawability deteriorates, and the effect of B on secondary workability is not exhibited. Note that as for the cooling method, it is preferable to cool the product as quickly as possible in the front half of the hot run table after finish rolling. The reduction ratio in cold rolling is required to be 50% or more in order to obtain deep drawability. In order to obtain the highest possible value, it is preferable to cold-roll at a rolling reduction of 75 to 85%. As for the cold rolling method, the tandem method is preferable to the lever method in order to secure a high price. The cold rolled coil is then continuously annealed, but first the soaking temperature is within the range of 700~A c3 . Below 700°C, recrystallization is insufficient and ductility is poor. A c3
Beyond this point, the texture favorable for deep drawability becomes disordered and the value deteriorates. Next, the holding time is set to 10 seconds to 10 minutes; however, holding for less than 10 seconds will not result in sufficient recrystallization, and if it exceeds 10 minutes, the crystal grains will become coarse and the tensile strength will decrease. After continuous annealing, an overaging treatment is usually performed. Temper rolling may be performed if necessary, but the reduction ratio is preferably 0.5 to 1.5%. According to the present invention, the structure of the steel sheet after continuous annealing consists of ferrite and pearlite, and no quenched structure such as martensite, which deteriorates deep drawability, is formed in the ferrite matrix. The cold-rolled original sheet or cold-rolled steel sheet produced by the method according to the present invention can also be used as a material for galvanized steel sheets and other surface-treated steel sheets. Next, examples of the present invention will be described. Example A cold-rolled steel plate having a thickness of 0.8 mm was produced from steel having the chemical components shown in Table 1 under hot rolling conditions, cold rolling conditions, and continuous annealing conditions as shown in the same table. Temper rolling is
In both cases, 1.2% was applied. Table 2 shows the mechanical properties, values, aging characteristics at room temperature, paint bake hardening amount, and secondary workability of the obtained steel plate. Here, the aging characteristics at room temperature were evaluated by the degree of elongation at yield point of the steel plate after 6 months at 23°C. The amount of paint baking hardening is the difference between the stress when a tensile test piece is pulled 2% in advance and the yield stress when it is pulled again after being unloaded and subjected to heat treatment equivalent to 20 minutes of paint baking at 170℃. It was shown in For secondary workability, the machined disc is drawn in three stages at an appropriate drawing ratio, the cup is held at a temperature of 10°C, and then a truncated conical punch is immediately pushed into the cup to form a hole on the side wall of the cup. Judgment was made based on whether brittle cracking occurred. The higher the limit drawing ratio at which brittle cracks do not occur, the better the secondary workability is. Steels A to D are steel plates according to the present invention, and have a high value of deep drawability in the range of tensile strength of 36 to 47 Kg/mm 2 , and no elongation at yield point occurs at room temperature. Despite this, it has a high coating hardening rate of approximately 6 kg/mm 2 and has excellent secondary workability. On the other hand, steel sheet E with a high carbon content produced by the conventional method has a low value, and steel sheet F, which is made by adding only P to ultra-low carbon Al-killed steel, has significant secondary work embrittlement. Steel G lacks B content, and secondary workability is hardly improved. Steel H
The value is very low due to the low finishing temperature, slow cooling rate after hot rolling, and high coiling temperature. As described above, according to the method of the present invention, the tensile strength is 35
A high-strength cold-rolled steel sheet can be produced that has a high value of Kg/mm 2 or more and a high paint bake hardenability of about 6 Kg/mm 2 and has excellent secondary workability.
【表】【table】
Claims (1)
1.0％以下、Ｐ：0.04〜0.12％、Ｓ：0.015％以下、
酸可溶Al：0.005〜0.070％、Ｎ：0.0060％以下、
Ｂ：11／14Ｎ％＜Ｂ11／14Ｎ＋0.0060％、残部が鉄お よび不可避的不純物からなる鋼を鋼片とした後、
Ar3点以上の温度で仕上げ圧延し、続いて20℃／
sec以上の冷却速度で冷却し、680℃以下で巻取
り、その後酸洗し、50％以上の圧下率で冷間圧延
した後、700〜Ac3点の温度範囲内で10秒〜10分
間均熱し冷却することを特徴とする連続焼鈍によ
る深絞り性と２次加工性に優れた高強度冷延鋼板
の製造法。[Claims] 1 C: 0.01% or less, Mn: 0.10 to 1.50%, Si:
1.0% or less, P: 0.04-0.12%, S: 0.015% or less,
Acid-soluble Al: 0.005 to 0.070%, N: 0.0060% or less,
B: 11/14N% < B11/14N + 0.0060%, after making the steel into a billet with the balance consisting of iron and unavoidable impurities,
Finish rolling at a temperature of A r3 or higher, followed by 20℃/
Cool at a cooling rate of sec or more, coil at 680℃ or less, then pickle, cold-roll at a reduction rate of 50% or more, and then equalize for 10 seconds to 10 minutes within the temperature range of 700 to A c3 points. A method for producing high-strength cold-rolled steel sheets with excellent deep drawability and secondary workability through continuous annealing, which is characterized by heating and cooling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10686681A JPS589933A (en) | 1981-07-10 | 1981-07-10 | Production of high strength cold rolled steel plate of superior deep drawability and secondary workability by continuous annealing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10686681A JPS589933A (en) | 1981-07-10 | 1981-07-10 | Production of high strength cold rolled steel plate of superior deep drawability and secondary workability by continuous annealing |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS589933A JPS589933A (en) | 1983-01-20 |
| JPH0123530B2 true JPH0123530B2 (en) | 1989-05-02 |
Family
ID=14444463
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10686681A Granted JPS589933A (en) | 1981-07-10 | 1981-07-10 | Production of high strength cold rolled steel plate of superior deep drawability and secondary workability by continuous annealing |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS589933A (en) |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0718836Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718837Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718834Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718833Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718832Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718835Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社内 | Armor type laterally-covered interior / exterior material |
| JPH0720272Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720271Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720274Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720273Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721714Y2 (en) * | 1989-05-01 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721713Y2 (en) * | 1989-05-01 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721717Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
| JPH0721716Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
| JPH0721715Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6077957A (en) * | 1983-10-05 | 1985-05-02 | Kawasaki Steel Corp | High-tension cold-rolled steel sheet with superior deep drawability |
-
1981
- 1981-07-10 JP JP10686681A patent/JPS589933A/en active Granted
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0718836Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718837Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718834Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718833Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718832Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社 | Armor type laterally-covered interior / exterior material |
| JPH0718835Y2 (en) * | 1989-05-01 | 1995-05-01 | 東邦シートフレーム株式会社内 | Armor type laterally-covered interior / exterior material |
| JPH0720272Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720271Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720274Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0720273Y2 (en) * | 1989-05-01 | 1995-05-15 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721714Y2 (en) * | 1989-05-01 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721713Y2 (en) * | 1989-05-01 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor-type laterally extending interior / exterior material |
| JPH0721717Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
| JPH0721716Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
| JPH0721715Y2 (en) * | 1989-05-11 | 1995-05-17 | 東邦シートフレーム株式会社 | Armor type joint material for interior and exterior materials |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS589933A (en) | 1983-01-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPS60174852A (en) | Cold rolled steel sheet having composite structure and superior deep drawability | |
| JPH0123530B2 (en) | ||
| JPH024657B2 (en) | ||
| 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 | |
| JP2521553B2 (en) | Method for producing cold-rolled steel sheet for deep drawing having bake hardenability | |
| JP4177477B2 (en) | Manufacturing method of cold-rolled steel sheet and hot-dip galvanized steel sheet with excellent room temperature aging resistance and panel characteristics | |
| JPH03277741A (en) | Dual-phase cold roller steel sheet excellent in workability, cold nonaging properties and baking hardenability and its manufacture | |
| JP2800541B2 (en) | Manufacturing method of high strength hot-dip galvanized steel sheet for deep drawing | |
| JPS5884928A (en) | Production of high-strength cold-rolled steel plate for deep drawing having excellent nonaging property, secondary workability and curing performance for baked paint | |
| JP3840855B2 (en) | High-strength thin steel sheet with excellent secondary work brittleness resistance and formability and method for producing the same | |
| JPH09209039A (en) | Production of high strength cold rolled steel sheet excellent in deep drawability | |
| JP3516747B2 (en) | Manufacturing method of cold-rolled steel sheet for non-aging deep drawing at room temperature with excellent material uniformity and surface quality in the coil longitudinal direction | |
| JPH058258B2 (en) | ||
| JPH05195060A (en) | Production of baking hardening type cold rolled steel sheet excellent in ageing resistance and press formability | |
| JP3043901B2 (en) | Method for producing high-strength cold-rolled steel sheet and galvanized steel sheet with excellent deep drawability | |
| JPH055156A (en) | High strength steel sheet for forming and its production | |
| JP2006199997A (en) | Automotive steel sheet and its manufacturing method | |
| JP4218598B2 (en) | High tensile alloyed hot dip galvanized steel sheet with excellent plating characteristics | |
| JPH0413816A (en) | Production of galvanized steel sheet having high moldability | |
| JP3150188B2 (en) | Method for manufacturing high-strength cold-rolled steel sheet with excellent deep drawability | |
| JPH05263189A (en) | High strength cold rolled steel sheet and galvanized high strength cold rolled steel sheet good in formability, and their manufacture | |
| JP3544441B2 (en) | High-strength hot-rolled steel sheet and plated steel sheet with excellent deep drawability and method for producing the same | |
| WO2020003986A1 (en) | Methods for producing cold-rolled steel sheet, hot-dip galvanized steel sheet, and alloyed hot-dip galvanized steel sheet | |
| JPH03150317A (en) | Manufacture of hot dip galvanized cold rolled steel sheet for deep drawing having excellent brittlement resistance in secondary working | |
| JPS6082617A (en) | Production of high tensile cold rolled steel plate for deep drawing |