JP2864966B2 - Continuously annealed cold rolled steel sheet with excellent balance between deep drawability and deep draw resistance - Google Patents
Continuously annealed cold rolled steel sheet with excellent balance between deep drawability and deep draw resistanceInfo
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- JP2864966B2 JP2864966B2 JP27312693A JP27312693A JP2864966B2 JP 2864966 B2 JP2864966 B2 JP 2864966B2 JP 27312693 A JP27312693 A JP 27312693A JP 27312693 A JP27312693 A JP 27312693A JP 2864966 B2 JP2864966 B2 JP 2864966B2
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Description
【０００１】[0001]
【産業上の利用分野】この発明は、極低炭素鋼を素材と
し、極めて優れた、深絞り成形性と耐深絞り脆性とのバ
ランスを有する冷延鋼板に関するものであり、前記冷延
鋼板から製造された表面処理鋼板等にも応用し得るもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-rolled steel sheet made of ultra-low carbon steel and having an extremely excellent balance between deep-drawing formability and deep-drawing brittleness. It can also be applied to manufactured surface-treated steel sheets and the like.
【０００２】[0002]
【従来の技術】最近の製鋼工程における脱ガス技術の進
歩により、鋼中の炭素( C ) 含有量を30ppm 以下まで低
減した極低炭素鋼が比較的安価で且つ大量に製造される
ようになり、前記極低炭素鋼にNb、Ti、B およびZr等を
添加した、所謂IF(Interstitial Free) 鋼が、連続焼鈍
プロセスで深絞り性と非時効性が要求されるEDDQクラス
の超深絞り用冷延鋼板を製造するための有力な素材とし
て一般化しつつある。2. Description of the Related Art Recent advances in degassing technology in the steelmaking process have led to the production of ultra-low carbon steels in which the carbon (C) content in steel has been reduced to 30 ppm or less, at relatively low cost and in large quantities. The so-called IF (Interstitial Free) steel in which Nb, Ti, B, Zr, etc. are added to the ultra-low carbon steel is used for an EDDQ class ultra-deep drawing in which a deep drawing property and a non-aging property are required in a continuous annealing process. It is becoming a popular material for manufacturing cold rolled steel sheets.
【０００３】連続焼鈍冷延鋼板として一般的に使用され
るIF鋼は、TiおよびNbを、各々単独あるいは複合添加し
た鋼である。Tiは強力な炭・窒化物形成元素であると同
時に、鋼中S をも硫化物として固定作用を有しているた
め、特に、Ti-IF 鋼は、広い成分範囲で、極めて優れた
深絞り性および延性が安定して得られるのが特徴であ
る。しかし、Tiは酸化し易いため、連続鋳造時のノズル
閉塞およびTi酸化物によるスラブ表面欠陥発生の問題が
ある。また、鋼中C をTiC として完全に固定するに足る
量のTiを添加した場合、焼鈍後の鋼板の粒界強度が低下
し、深絞り脆化(2次加工脆化) の問題が顕在化する。深
絞り脆化の問題に対しては、微量B の添加が有効である
ことが知られているが、深絞り性の劣化を伴う点が問題
である。[0003] IF steel generally used as a continuously annealed cold rolled steel sheet is a steel in which Ti and Nb are added individually or in combination. Since Ti is a strong carbon and nitride forming element and also has the effect of fixing S in the steel as a sulfide, Ti-IF steel is particularly excellent in deep drawing in a wide range of components. It is characterized in that the properties and ductility are obtained stably. However, since Ti is easily oxidized, there is a problem of nozzle clogging during continuous casting and slab surface defects caused by Ti oxide. In addition, if sufficient amount of Ti is added to completely fix C in steel as TiC, the grain boundary strength of the annealed steel sheet decreases, and the problem of deep drawing embrittlement (secondary work embrittlement) becomes apparent. I do. It is known that the addition of a small amount of B is effective for the problem of deep drawing embrittlement, but there is a problem in that deep drawability is deteriorated.
【０００４】これに対し、Nb−IF鋼は、NbC として鋼中
C を固定することによって、Ti−IF鋼と同様に優れた深
絞り性が得られるが、Ti−IF鋼に比べて、Nb含有量の適
正範囲が狭いという問題がある。しかし、酸化物系のス
ラブ表面欠陥が生成しにくいため、スラブ手入れが不要
になり、直送圧延による熱延鋼帯の製造が可能となるメ
リットがある。また、合金化亜鉛メッキ鋼板の原板とし
て、Nbを単独あるいはTiとの複合添加したIF鋼を使用し
た場合、合金層の密着性がTi−IF鋼に比べて改善される
ことが知られている。On the other hand, Nb-IF steel is used as NbC in steel.
By fixing C, excellent deep drawability can be obtained as in the case of Ti-IF steel, but there is a problem that the appropriate range of the Nb content is narrower than that of Ti-IF steel. However, since oxide-based slab surface defects are not easily generated, there is an advantage that slab care is not required and a hot-rolled steel strip can be manufactured by direct-feed rolling. It is also known that, when an IF steel to which Nb is used alone or in combination with Ti is used as a base plate of an alloyed galvanized steel sheet, the adhesion of the alloy layer is improved as compared with the Ti-IF steel. .
【０００５】上述したTi添加IF鋼およびNb添加IF鋼相互
の補完技術として、NbおよびTiの両方を添加する複合添
加技術（特公昭61-32375号公報) が開示されている。そ
の技術の骨子は、0.003 〜0.025wt.% のNbと、0.010 〜
0.037wt.% のTiを、Nb＞2.33C 、(48/14)(N −0.002)＜
Ti＜4 C ＋3.43N の条件にて添加するもので、仕上げ熱
延前にN をTiN とし、そして、C を[Nb,Ti]Cとして完全
に固定することを基本技術としている。As a complementary technique between the above-mentioned IF-added Ti steel and IF-added Nb steel, there is disclosed a composite addition technique (Japanese Patent Publication No. 61-32375) in which both Nb and Ti are added. The essence of the technology is 0.003-0.025 wt.% Nb and 0.010-0.025 wt.
0.037wt.% Ti, Nb> 2.33C, (48/14) (N−0.002) <
It is added under the condition of Ti <4C + 3.43N, and the basic technology is to completely fix N as TiN and C as [Nb, Ti] C before hot rolling.
【０００６】さて、IF鋼への微量B 添加は、従来開示さ
れた特許出願においては、第2 請求項以降で付加的に限
定されるケ−スが大半であった。これは、B が、耐2 次
加工脆化に対して極めて有効な元素である反面、鋼板の
必須の特性として要求されている深絞り性を劣化させる
元素であるため、積極的な添加は必ずしも得策ではない
ためである。これに対して、IF鋼にB を積極的に添加す
る技術として、特開昭63-317625 号公報等が開示されて
いる。これは、IF鋼の不可避的な問題である溶接熱影響
部の組織微細化作用を利用して、B 添加による深絞り性
の劣化を回避しようとするものであるが、ベ−スとなる
成分系は、TiとNbを複合添加したIF鋼である。また、２
次加工性と表面処理性を考慮した鋼板が、特開昭59-140
333 号公報に、そして、絞り用合金化溶融亜鉛めっき鋼
板が、特開平1-184227号公報に開示されているが、基本
的な成分設計思想および作用・効果の点では、深絞り性
と耐深絞り脆性とのバランスの向上を配慮した技術では
ない。[0006] The addition of a trace amount of B to IF steel has been mostly limited in the patent applications disclosed so far by the additional claims after the second claim. This is because B is an element that is extremely effective for secondary work embrittlement resistance, but because it is an element that deteriorates the deep drawability required as an essential property of steel sheets, active addition is not necessarily required. This is not a good idea. On the other hand, Japanese Patent Application Laid-Open No. 63-317625 discloses a technique for positively adding B to IF steel. This aims to avoid the deterioration of deep drawability due to the addition of B by utilizing the structure refinement of the weld heat-affected zone, which is an inevitable problem of IF steel. The system is an IF steel with a complex addition of Ti and Nb. Also, 2
A steel sheet that takes into account the secondary workability and surface treatment properties is disclosed in JP-A-59-140.
No. 333 and an alloyed hot-dip galvanized steel sheet for drawing are disclosed in Japanese Patent Application Laid-Open No. 1-184227. It is not a technique that considers the improvement of balance with deep drawing brittleness.
【０００７】[0007]
【発明が解決しようとする課題】近年、自動車の部品形
状の複雑化、大型化および防錆性の重視等に伴い、従来
は成形性の厳しい部位( リアクウオ−タ等) のみに使用
されていたEDDQクラスの超深絞り用冷延鋼板の使用割合
が増大しており、前記EDDQクラスの鋼板が汎用品種とし
て大量に使用されるようになってきた。一方、連続焼鈍
プロセスの普及に伴って、当該プロセスで非時効超深絞
り用冷延鋼板を製造する最も有効な方法として、IF鋼を
素材とした製造法が一般的になりつつある。しかし、IF
鋼を汎用品種として大量に製造すると、前述したよう
に、深絞り脆化等のIF鋼特有の問題が顕在化する危険性
があり、成分設計上十分な配慮が必要となる。本発明の
目的は、このような実態に鑑み、上述した問題点を解決
することによって、IF鋼において二律背反する特性であ
る、深絞り成形性と、耐深絞り脆性とをバランスさせる
上で最も好ましい成分設計をし、深絞り性と耐深絞り脆
性とのバランスの優れた連続焼鈍冷延鋼板を提供するこ
とにある。In recent years, as the shape and size of automobile parts have become more complicated, rust prevention has been emphasized, and so on, the former has been used only for parts (reactor, etc.) having severe moldability. The use ratio of cold rolled steel sheets for ultra deep drawing of the EDDQ class is increasing, and the steel sheets of the EDDQ class have come to be used in large quantities as general-purpose products. On the other hand, with the widespread use of the continuous annealing process, a production method using IF steel as a raw material has become common as the most effective method for producing a cold-rolled steel sheet for non-aging ultra-deep drawing in the process. But IF
When steel is manufactured in large quantities as a general-purpose product, as described above, there is a risk that problems specific to IF steel, such as deep drawing embrittlement, may become apparent, and sufficient consideration must be given to component design. The object of the present invention is, in view of such a situation, by solving the above-mentioned problems, the most contradictory properties in IF steel, deep drawing formability, and most preferable in balancing deep drawing brittle resistance. It is an object of the present invention to provide a continuously annealed cold-rolled steel sheet having an excellent balance between deep drawability and resistance to deep drawability by designing the components.
【０００８】[0008]
【課題を解決するための手段】本発明は、C 含有量が0.
0030wt.%未満である極低炭素鋼をベ−スとしたIF鋼を改
善して、深絞り性と耐深絞り脆性の両者をバランスよく
向上させた、最も優れた非時効超深絞り用冷延鋼板に関
するものであり、Ti(0.02 〜0.05wt.%) および微量のB
(3 〜10ppm)を含有した極低炭素鋼を必須鋼種とし、且
つ、Ti*(＝Ti−(48/14) N −(48/32) S ≧0)、C および
B 量で規定されるX ( ＝−ln｛(C/Ti*) B｝）の値を適
正範囲に規制することに特徴を有し、このような化学成
分組成によって初めて目的を達成することができあるも
のであり、詳しくは下記のとおりである。Means for Solving the Problems The present invention has a C content of 0.1%.
The best non-aging ultra-deep drawing cold-rolled steel with improved balance between deep drawability and deep draw brittleness by improving IF steel based on ultra-low carbon steel of less than 0030 wt.%. This is related to rolled steel sheets, Ti (0.02-0.05wt.%) And trace amounts of B
(3 to 10 ppm) as an essential steel grade, and Ti * (= Ti− (48/14) N− (48/32) S ≧ 0), C and
It is characterized in that the value of X (= -ln ｛(C / Ti *) B｝), which is defined by the amount of B, is regulated to an appropriate range. It is possible, and details are as follows.
【０００９】この発明の、深絞り性と耐深絞り脆性との
バランスの優れた連続焼鈍冷延鋼板は、C ：0.0030wt.%
未満、Mn：0.05〜0.20wt.%、Si：0.05wt.%以下、P ：0.
02wt.%以下、S ：0.010 wt.%以下、sol.Al：0.025 〜0.
06wt.%、N ：0.0030 wt.% 以下、Ti：0.02〜0.05wt.%未
満、B ：0.0003〜0.0010wt.%、を含有し、且つ、下記
(1) 、(2) 式、 X ＝−ln｛( C / Ti* ) B ｝ ─────────(1) 但し、Ti* ＝Ti−(48/14) N −(48/32) S ≧0 ──(2) で規定されるX の値が9.2 〜11.2の範囲を満足し、残部
が鉄(Fe)および不可避不純物からなる化学成分組成を有
することに特徴を有するものである。The continuously annealed cold rolled steel sheet of the present invention, which has an excellent balance between deep drawability and deep draw resistance, has a C content of 0.0030 wt.%.
, Mn: 0.05 to 0.20 wt.%, Si: 0.05 wt.% Or less, P: 0.
02 wt.% Or less, S: 0.010 wt.% Or less, sol.Al: 0.025 to 0.
06 wt.%, N: 0.0030 wt.% Or less, Ti: 0.02-0.05 wt.%, B: 0.0003-0.0010 wt.%, And
(1), (2), X = −ln ｛(C / Ti *) B｝ ───────── (1) where Ti * = Ti− (48/14) N − (48 / 32) S ≧ 0 ── (2) The value of X satisfies the range of 9.2 to 11.2, and the balance is characterized by having a chemical composition of iron (Fe) and unavoidable impurities. It is.
【００１０】[0010]
【作用】本発明において最も重要な構成要件は、0.0030
wt.%未満のC 含有量の極低炭素鋼に、0.02〜0.05wt.%の
範囲内のTi、および、3 〜10ppm の範囲内のB を複合添
加したIF鋼において、その化学成分組成について前記
(1) および(2) 式で算出されるX の値を、9.2 〜11.2の
範囲内に限定する点にあり、これによって、深絞り性と
耐深絞り脆性とのバランスの優れた連続焼鈍冷延鋼板が
得られる。The most important component in the present invention is 0.0030
The chemical composition of an ultra-low carbon steel with a C content of less than wt.%, combined with Ti in the range of 0.02-0.05 wt.% and B in the range of 3-10 ppm, was added. Said
The value of X calculated by the formulas (1) and (2) is limited to the range of 9.2 to 11.2, whereby the continuous annealing and cooling having an excellent balance between the deep drawability and the resistance to deep drawability are performed. A rolled steel sheet is obtained.
【００１１】この発明の連続焼鈍冷延鋼板の化学成分組
成を上述した範囲内に限定した理由について述べる。 (1) Ti:本発明では、IF鋼として不可欠な炭・窒化物形
成元素の添加に関して、Tiを必須添加元素とするが、同
時に当該成分系の鋼板の表面性状に影響を及ぼすスラブ
段階での表面欠陥はTiが原因となることから、Tiの含有
量を制限する。スラブの表面欠陥は、Tiの添加量の増加
に伴って悪化する。特に、直送圧延等を行なう場合は厳
密な管理が必要となる。図1 は、Ti添加極低炭素鋼の連
続鋳造スラブ表面に発生するピンホ−ル欠陥に対する、
微量のNbおよびB の効果を示したグラフである。同図か
ら明らかなように、Ti添加鋼では、Ti含有量の増加に伴
って、連続鋳造スラブ表面に発生するピンホ−ル欠陥は
増加するが、微量のB を複合添加することによって、ピ
ンホ−ル欠陥は著しく減少し、その効果はNbを複合添加
したものより顕著である。このような点から、本発明で
は、極微量のB 添加によってスラブの欠陥を皆無とする
ことを目標として、Ti含有量の上限を0.05wt.%未満とす
る。一方、Tiは強力な窒化物および硫化物形成元素であ
る。特に、鋼中のN に関しては、高温域でTiN として粗
大析出するため、熱間圧延後にN をAlN として析出させ
ることにより、コイル長手方向の材質変動が改善され
る。そこで、窒化物および硫化物として析出した残余の
Tiが鋼中のC を析出固定させ得る条件として、Tiの含有
量の下限を0.02wt.%とする。従って、Tiの含有量は、0.
02〜0.05wt.%未満の範囲内に限定すべきである。The reason why the chemical composition of the continuously annealed cold-rolled steel sheet of the present invention is limited to the above range will be described. (1) Ti: In the present invention, with respect to the addition of the carbon / nitride forming element indispensable as an IF steel, Ti is an essential additive element, but at the same time in the slab stage which affects the surface properties of the steel sheet of the component system. Since surface defects are caused by Ti, the content of Ti is limited. The surface defects of the slab worsen with an increase in the amount of Ti added. In particular, strict control is required when performing direct rolling. Figure 1 shows the pinhole defects on the surface of the continuous cast slab of Ti-added ultra-low carbon steel.
5 is a graph showing the effects of trace amounts of Nb and B. As can be seen from the figure, in the Ti-added steel, the pinhole defects generated on the surface of the continuously cast slab increase with the increase of the Ti content. The defect is significantly reduced, and the effect is more remarkable than that of the composite addition of Nb. From such a point, in the present invention, the upper limit of the Ti content is set to less than 0.05 wt.% In order to eliminate the defects of the slab by adding a very small amount of B. On the other hand, Ti is a strong nitride and sulfide forming element. In particular, since N in steel is coarsely precipitated as TiN in a high temperature region, the material fluctuation in the longitudinal direction of the coil is improved by precipitating N as AlN after hot rolling. Therefore, the residuals precipitated as nitrides and sulfides
As a condition under which Ti can precipitate and fix C in steel, the lower limit of the content of Ti is set to 0.02 wt.%. Therefore, the content of Ti is 0.
It should be limited to the range from 02 to less than 0.05 wt.%.
【００１２】(2) C :次に、本発明では、鋼中のC の全
てを、TiC またはTiS を核とした炭硫化物として析出さ
せることを目標とする。これは、IF鋼としての優れた成
形性および完全非時効性を兼備することを必須条件にす
るためである。C はIF鋼として成分設計する上で、その
含有量が少ないほどTiの添加量が少なくてすむ。そこ
で、本発明では、Tiの含有量が0.02〜0.05wt.%未満の範
囲内で固定できるC の含有量の上限値を、0.0030wt.%未
満に限定する。しかし、熱間圧延時の組織の細粒化に対
しては、C は有効な元素であり、両者の観点からC 含有
量は、0.0010〜0.0015wt.%程度が望ましい。(2) C: Next, the present invention aims to precipitate all of C 2 in the steel as a carbosulfide having TiC or TiS as a nucleus. This is because it is an essential condition to have both excellent formability and complete non-aging property as IF steel. When designing the composition of C as an IF steel, the smaller the content, the smaller the amount of Ti added. Therefore, in the present invention, the upper limit of the C content that can be fixed within the range of Ti content of 0.02 to less than 0.05 wt.% Is limited to less than 0.0030 wt.%. However, C is an effective element for refining the structure during hot rolling, and from both viewpoints, the C content is desirably about 0.0010 to 0.0015 wt.%.
【００１３】(3) Si:Siは鋼板の延性を維持する点か
ら、その含有量を0.05wt.%以下に限定する。 (4) Mn:Mn含有量は、TiがS を固定するので、通常レベ
ルよりも低くても問題がない。特に、連続焼鈍過程で残
留固溶C を析出させるためには、Mn含有量は低い方が望
ましいが、0.05wt.%未満では溶銑予備処理コストが上昇
する。一方、残留固溶Cの低減および深絞り性に好まし
い集合組織の発達を図るために、0.20wt.%以下にするこ
とが必要である。従って、Mnの含有量は、0.05〜0.20w
t.%の範囲内に限定すべきである。(3) Si: The content of Si is limited to 0.05 wt.% Or less from the viewpoint of maintaining the ductility of the steel sheet. (4) Mn: The Mn content is not problematic even if it is lower than the normal level because Ti fixes S 2. In particular, in order to precipitate residual solid solution C in the continuous annealing process, the lower the Mn content, the better. However, if it is less than 0.05 wt.%, The cost of hot metal pretreatment increases. On the other hand, in order to reduce the residual solid solution C and develop a texture preferable for deep drawability, the content needs to be 0.20 wt.% Or less. Therefore, the content of Mn is 0.05 to 0.20 w
It should be limited to the range of t.%.
【００１４】(5) P :P は、耐深絞り脆化に対して有害
な元素であるが、B を必須添加元素とする本発明におい
ては、その含有量の上限値が緩和される。しかしなが
ら、成形性を維持するため、延性に対する悪影響が無視
できる範囲内に抑えることが必要である。従って、P 含
有量は、0.02wt.%以下に限定すべきである。(5) P: P is an element harmful to the deep drawing embrittlement resistance, but in the present invention in which B is an essential additive element, the upper limit of the content is relaxed. However, in order to maintain formability, it is necessary to keep the adverse effect on ductility within a negligible range. Therefore, the P content should be limited to 0.02 wt.% Or less.
【００１５】(6) S :S は、Tiと硫化物を形成すること
によってTi*(＝Ti−(48/14) N −(48/32) S≧0)を減ず
る。S によって、硫化物として消費されるTiを極力少な
くすることが必要である。従って、S の含有量は0.010
wt.%以下に限定すべきである。(6) S: S reduces Ti * (= Ti− (48/14) N− (48/32) S ≧ 0) by forming a sulfide with Ti. It is necessary to minimize the amount of Ti consumed as sulfide by S. Therefore, the content of S is 0.010
It should be limited to wt.% or less.
【００１６】(7) Al:Alは、Tiが添加された本発明の鋼
においては、N を固定するだけの目的であれば、連続鋳
造が可能な範囲内でその含有量を低減することができ
る。しかしながら、本発明では、Alで鋼を脱酸すること
によって、Tiの酸化を抑制し、表面欠陥の発生を減ずる
ことが必要である。このような作用を発揮させるため
に、Alの含有量は、0.025 〜0.06wt.%の範囲内に限定す
べきである。(7) Al: In the steel of the present invention to which Ti is added, if the purpose is only to fix N, the content of Al can be reduced within a range where continuous casting is possible. it can. However, in the present invention, it is necessary to suppress the oxidation of Ti and reduce the occurrence of surface defects by deoxidizing steel with Al. In order to exert such an effect, the content of Al should be limited to the range of 0.025 to 0.06 wt.%.
【００１７】(8) N :N は、IF鋼の材質特性を発揮させ
るために、その含有量は低い方が望ましい。特に、Tiと
窒化物を形成することによってTi*(＝Ti−(48/14) N −
(48/32) S ≧0)を減ずる。従って、N の含有量は、0.00
30wt.%以下に限定すべきである。(8) In order to exhibit the material properties of IF steel, the content of N: N is preferably low. In particular, Ti * (= Ti− (48/14) N −
(48/32) S ≧ 0) is reduced. Therefore, the content of N is 0.00
It should be limited to 30 wt.% Or less.
【００１８】(9) B :B は、本発明の必須添加元素であ
る。特に、Ti添加IF鋼をベ−スとしてB を添加すること
により、深絞り性と深絞り脆化とのバランスが、従来の
鋼板と比較して格段に向上する。図2 は、Ti添加IF鋼、
Nb添加IF鋼およびTi、Nb複合添加IF鋼の各々にB を添加
した鋼板の、連続焼鈍後の鋼板の面内3 方向(0°、45
°、90°) のｒ値の最低値（ｒmin ) と、絞り比2.2 で
評価し、絶対温度で表した深絞り脆化臨界温度( Ｔth)
との比（ｒmin ／Ｔth）を、鋼中B 含有量で整理したグ
ラフである。同図から明らかなように、B を本発明の範
囲内のTi含有量と共に複合添加した場合にのみ、B 含有
量が3 〜10ppm の範囲内で、ｒmin ／Ｔth≧0.015 とな
る。図3 は、Ti、B 添加IF鋼において、ｒmin ／Ｔ
thを、X [ ＝−ln｛(C/Ti*) B] で整理したグラフであ
る。同図から明らかなように、ｒmin ／Ｔth≧0.015 と
なるのは、X の値が9.2 〜11.2の範囲内のときである。
従って、本発明においては、Ti添加をベ−スとして、B
の含有量を3 〜10ppmの範囲内に限定し、更に、X [ ＝
−ln｛(C/Ti*) B ] が9.2 〜11.2の範囲内になるように
限定すべきである。(9) B: B is an essential additive element of the present invention. In particular, by adding B with a Ti-added IF steel as a base, the balance between deep drawability and deep draw embrittlement is significantly improved as compared with conventional steel sheets. Figure 2 shows the Ti-added IF steel,
The in-plane three directions (0 °, 45 °) of the steel sheet after continuous annealing of the steel sheet containing B added to each of the Nb-added IF steel and the Ti / Nb composite-added IF steel
°, 90 °) and the critical value of the deep drawing embrittlement critical temperature (T th ) expressed in absolute temperature, evaluated with the lowest value of the r value (r min ) and the drawing ratio of 2.2.
5 is a graph in which the ratio (r min / T th ) with the B content in steel is arranged. As is clear from the figure, only when B is added in combination with Ti content within the range of the present invention, r min / T th ≧ 0.015 when the B content is within the range of 3 to 10 ppm. Figure 3 shows rmin / T for Ti and B-added IF steel.
The th, is a graph organized by X [= -ln {(C / Ti *) B]. As is clear from the figure, r min / T th ≧ 0.015 is satisfied when the value of X is in the range of 9.2 to 11.2.
Therefore, in the present invention, the addition of Ti
Is limited to the range of 3 to 10 ppm, and X [=
−ln ｛(C / Ti *) B] should be limited to the range of 9.2 to 11.2.
【００１９】本発明鋼の特性を最大限に発揮させるため
には、連続焼鈍プロセスにて焼鈍することが必須であ
る。その場合、焼鈍温度が再結晶温度以上であれば、本
発明鋼の特性を発揮させることができるが、ｒmin は高
温で焼鈍するほど増大するため、Ａc3変態点直下までの
温度範囲であって、できる限り高温度で焼鈍するのが望
ましい。なお、本発明で開示した鋼板は、連続焼鈍後に
各種の電気メッキ処理工程、有機被覆工程あるいは冷延
鋼板を連続溶融亜鉛メッキ工程にて防錆性の優れた鋼板
に適用することも可能で、優れた深絞り性と耐2 次加工
脆性のバランスが損なわれることはない。In order to maximize the properties of the steel of the present invention, it is essential to perform annealing in a continuous annealing process. In that case, if the annealing temperature is the recrystallization temperature or higher, although it is possible to exhibit the properties of the steel of the present invention, r min in order to increase as the annealing at high temperature, a temperature range of up to just below Ac 3 transformation point Therefore, it is desirable to anneal at as high a temperature as possible. Incidentally, the steel sheet disclosed in the present invention, it is also possible to apply a variety of electroplating steps after continuous annealing, an organic coating step or a cold-rolled steel sheet to a steel sheet excellent in rust prevention in a continuous hot-dip galvanizing step, The balance between excellent deep drawability and secondary work brittleness is not impaired.
【００２０】[0020]
【実施例】次に、この発明を実施例により、比較例と対
比しながら説明する。 (実施例1)表1 に示す本発明の範囲内の化学成分組成を
有する本発明鋼No.1〜8 、および、表2 に示す本発明の
範囲外の化学成分組成を有する比較鋼No.1〜20の連続鋳
造鋳片を、1200℃に加熱した後、粗圧延で厚さ36mmに圧
延し、次いで、仕上げ温度を890 〜920 ℃の範囲内の条
件で熱間圧延を行い、厚さ3.2 mmの鋼板とした。このよ
うにして得られた熱延鋼帯を620 ℃で巻き取った。前記
熱延鋼帯を酸洗後、厚さ0.8 mmまで冷間圧延を行い、次
いで、840 〜850 ℃の温度範囲で連続焼鈍を施した。こ
のようにして得られた鋼帯に対して0.5%の調質圧延を施
して連続焼鈍冷延鋼帯を製造した。前記連続焼鈍冷延鋼
帯の各々から試験片を採取して、鋼板の面内３方向（ 0
°、45°、90°) のｒ値の最低値( ｒmin ) 、絞り比2.
2 で評価し、絶対温度で表した深絞り脆化臨界温度( Ｔ
th) を測定すると共に、ｒmin / Ｔthを求めて、表3 に
示した。なお、スラブの表面欠陥の発生状況について併
記した。〇は欠陥発生なし、△は軽度の欠陥発生、×は
欠陥発生を表す。EXAMPLES Next, the present invention will be described with reference to examples and comparative examples. (Example 1) Inventive steel Nos. 1 to 8 having a chemical composition within the range of the present invention shown in Table 1, and comparative steel No. 1 having a chemical composition outside the range of the present invention shown in Table 2. After heating the continuous cast slab of 1 to 20 to 1200 ° C, it is rolled to a thickness of 36 mm by rough rolling, and then hot-rolled at a finishing temperature within a range of 890 to 920 ° C to obtain a thickness. A 3.2 mm steel plate was used. The hot-rolled steel strip thus obtained was wound at 620 ° C. After pickling the hot-rolled steel strip, it was cold-rolled to a thickness of 0.8 mm, and then continuously annealed in a temperature range of 840 to 850 ° C. The steel strip thus obtained was subjected to a temper rolling of 0.5% to produce a continuously annealed cold-rolled steel strip. Specimens were sampled from each of the continuous annealed cold rolled steel strips, and were in three directions (0
(°, 45 °, 90 °), the lowest r value (r min ), aperture ratio 2.
The critical temperature of deep drawing embrittlement (T
th )), and r min / T th was determined, and the results are shown in Table 3. The occurrence of surface defects on the slab is also shown. 〇 indicates no defect occurrence, △ indicates a slight defect occurrence, and X indicates a defect occurrence.
【００２１】[0021]
【表１】 [Table 1]
【００２２】[0022]
【表２】 [Table 2]
【００２３】[0023]
【表３】 [Table 3]
【００２４】表1 、2 および3 から明らかなように、本
発明の範囲外の化学成分組成を有する比較鋼No.7〜9 、
11、17および18から製造した冷延鋼板は、ｒmin が2.0
以上と高く深絞り性が優れていたが、Ｔthが153 〜223K
と高温であって耐深絞り脆性が劣化し、また、比較鋼N
o.1〜6 、12〜16、19および20から製造した冷延鋼板
は、Ｔthが133K以下と低温であって耐深絞り脆性が優れ
ていたが、ｒmin が1.98以下と低く深絞り性が劣化し、
従って、No.10 を除くすべての比較鋼のｒmin / Ｔthの
値は低く( 0.015 以下) 、深絞り性と耐深絞り脆性との
バランスが劣化した。なお、比較鋼No.10 から製造した
冷延鋼板は、ｒmin 、Ｔthおよびｒmin / Ｔth共に優れ
ているが、スラブに軽度の表面欠陥が発生した。As is clear from Tables 1, 2 and 3, comparative steels Nos. 7 to 9 having a chemical composition outside the scope of the present invention,
The cold-rolled steel sheets manufactured from 11, 17 and 18 have r min of 2.0
As described above, the deep drawability was excellent and the T th was 153 to 223K.
At high temperatures, the brittleness resistance to deep drawing deteriorates.
o. The cold-rolled steel sheets manufactured from 1 to 6, 12 to 16, 19 and 20 had a low T th of 133 K or less and were excellent in deep drawing brittleness resistance, but had a low r min of 1.98 or less and had a low deep drawing. Deteriorates,
Therefore, the values of r min / T th of all the comparative steels except No. 10 were low (0.015 or less), and the balance between deep drawability and deep draw resistance was deteriorated. In addition, the cold rolled steel sheet manufactured from the comparative steel No. 10 was excellent in both r min , T th and r min / T th , but a slight surface defect occurred in the slab.
【００２５】これに対して、本発明の範囲内の化学成分
組成を有する本発明鋼No.1〜8 から製造した冷延鋼板は
いずれも、ｒmin は、2.0 以上と高く深絞り性が優れて
おり、Ｔthは、133 K 以下と低温であって、耐深絞り脆
性が優れており、しかも、ｒmin / Ｔthは、0.015 以上
であって深絞り性と耐深絞り脆性とのバランスが優れて
いた。更に、スラブの表面には欠陥が発生せず良好であ
った。On the other hand, all of the cold rolled steel sheets produced from the steels Nos. 1 to 8 of the present invention having a chemical composition within the range of the present invention have a high r min of 2.0 or more and excellent deep drawability. T th is as low as 133 K or lower and has excellent resistance to deep drawing embrittlement, and r min / T th is not less than 0.015 and a balance between deep drawability and resistance to deep drawing embrittlement. Was excellent. Furthermore, no defects were generated on the surface of the slab, and the slab was good.
【００２６】(実施例2)表1 に示した本発明鋼No.1〜3
、5 〜8 、および、表 2に示した比較鋼No.7〜10およ
び17〜20の連続鋳造鋳片を加熱することなく、直送圧延
( 熱間圧延) を行なった。粗圧延で36mmに圧延した後、
実施例1 と同じく、仕上げ厚さを3.2 mm、仕上げ温度を
870 〜910 ℃の範囲内の条件で熱間圧延を行い、このよ
うにして得られた熱延鋼帯を660 ℃で巻き取った。前記
熱延鋼帯を酸洗後、厚さ0.8 mmまで冷間圧延を行い、次
いで、840 〜850 ℃の温度範囲で連続焼鈍を施した。こ
のようにして得られた鋼帯に対して0.5%の調質圧延を施
して連続焼鈍冷延鋼帯を製造した。前記連続焼鈍冷延鋼
帯の各々から試験片を採取して、鋼板の面内３方向（ 0
°、45°、90°) のｒ値の最低値( ｒmin ) 、絞り比2.
2 で評価し、絶対温度で表した深絞り脆化臨界温度( Ｔ
th) を測定すると共に、ｒmin / Ｔthを求めて、表4 に
示した。なお、スラブ表面のピンホ−ル欠陥の発生密度
( 指標) について表4 に併記した。(Example 2) Steel Nos. 1 to 3 of the present invention shown in Table 1
, 5-8 and continuous cast slabs of comparative steel Nos. 7-10 and 17-20 shown in Table 2 without heating
(Hot rolling). After rolling to 36mm by rough rolling,
As in Example 1, the finishing thickness was 3.2 mm and the finishing temperature was
Hot rolling was performed at a temperature in the range of 870 to 910 ° C, and the hot-rolled steel strip thus obtained was wound at 660 ° C. After pickling the hot-rolled steel strip, it was cold-rolled to a thickness of 0.8 mm, and then continuously annealed in a temperature range of 840 to 850 ° C. The steel strip thus obtained was subjected to a temper rolling of 0.5% to produce a continuously annealed cold-rolled steel strip. Specimens were sampled from each of the continuous annealed cold rolled steel strips, and were in three directions (0
(°, 45 °, 90 °), the lowest r value (r min ), aperture ratio 2.
The critical temperature of deep drawing embrittlement (T
th ) was measured, and r min / T th was determined. The results are shown in Table 4. The density of pinhole defects on the slab surface
(Index) is also shown in Table 4.
【００２７】[0027]
【表４】 [Table 4]
【００２８】表1 、2 および4 から明らかなように、連
続鋳造鋳片に対して、直送による熱間圧延を施した場合
でも、実施例１で得られた結果と同様、本発明の範囲外
の化学成分を有する鋼から製造した冷延鋼板は、深絞り
性または耐深絞り脆性のいずれかが劣っているために、
深絞り性と耐深絞り脆性とのバランスが劣っていた。更
に、スラブ表面にピンホ−ル欠陥が発生したものが多か
った。これに対して、本発明の範囲内の化学成分組成を
有する鋼から製造した冷延鋼板は、深絞り性および耐深
絞り脆性がすぐれており、しかも、深絞り性と耐深絞り
脆性とのバランスが優れていた。また、スラブ表面には
ピンホ−ル欠陥が発生せず、スラブ表面は良好であっ
た。As is evident from Tables 1, 2 and 4, even if the continuous cast slab was subjected to hot rolling by direct feeding, it was out of the scope of the present invention similarly to the result obtained in Example 1. Cold-rolled steel sheet manufactured from steel having the chemical composition of, because either deep drawability or deep draw resistance is inferior,
The balance between deep drawability and deep draw resistance was poor. Furthermore, many pinhole defects occurred on the slab surface. On the other hand, a cold-rolled steel sheet manufactured from steel having a chemical composition within the range of the present invention has excellent deep drawability and deep draw brittleness resistance, and furthermore, has a deep drawability and a deep draw resistance brittleness. The balance was excellent. Also, no pinhole defects were generated on the slab surface, and the slab surface was good.
【００２９】[0029]
【発明の効果】以上詳述したように、本発明において
は、極低C 鋼をベ−スとして、TiおよびB 等を適正量含
有する化学成分組成の鋼を開発し、B およびTiの複合添
加によりIF鋼を改善したので、IF鋼における相反する特
性である深絞り性と耐深絞り脆性とのバランスの優れた
連続焼鈍冷延鋼板を、安価に、効率よく、そして、安定
して量産することができる、工業上有用な効果が得られ
る。As described in detail above, in the present invention, a steel having a chemical composition containing an appropriate amount of Ti, B, etc., based on an extremely low C steel, has been developed, and a composite of B and Ti has been developed. Since the addition of the IF steel has improved the IF steel, the continuous annealing cold-rolled steel sheet with an excellent balance between the contradictory properties of the IF steel, deep drawing and deep drawing brittleness, has been mass-produced inexpensively, efficiently, and stably. An industrially useful effect can be obtained.
【図１】Ti添加極低炭素鋼の連続鋳造スラブ表面に発生
するピンホ−ル欠陥に対する、微量のNbおよびB の効果
を示したグラフである。FIG. 1 is a graph showing the effect of trace amounts of Nb and B on pinhole defects generated on the surface of a continuously cast slab of Ti-added ultra-low carbon steel.
【図２】Ti添加IF鋼、Nb添加IF鋼およびTi、Nb複合添加
IF鋼の各々にB を添加した鋼板の、連続焼鈍後の鋼板の
面内3 方向(0°、45°、90°) のｒ値の最低値（ｒmin)
と、絶対温度で評価した深絞り脆化臨界温度( Ｔth)
との比（ｒmin ／Ｔth）を、鋼中B 含有量で整理したグ
ラフである。Figure 2: Ti-added IF steel, Nb-added IF steel, and Ti and Nb composite addition
The lowest r value (r min ) in three in-plane directions (0 °, 45 °, 90 °) of the steel sheet after continuous annealing of the steel sheet with B added to each of the IF steels
And deep drawing embrittlement critical temperature (T th ) evaluated in absolute temperature
5 is a graph in which the ratio (r min / T th ) with the B content in steel is arranged.
【図３】Ti、B 添加IF鋼において、ｒmin ／Ｔthを、鋼
中の化学成分組成によって決まる値X [ ＝−ln｛(C/Ti
*)B、但し、Ti* ＝Ti−(48/14) N −(48/32) S ≧0 ]
で整理したグラフである。[FIG. 3] In the Ti steel and B-added IF steel, r min / T th is set to a value X [= −ln ｛(C / Ti / C) determined by the chemical composition of the steel.
*) B, where Ti * = Ti-(48/14) N-(48/32) S ≥ 0]
It is a graph arranged in.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平６−49590（ＪＰ，Ａ) 特開 平５−195079（ＪＰ，Ａ) 特開 平５−117758（ＪＰ，Ａ) 特開 昭59−140333（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C22C 38/00 - 38/60 C21D 9/46 - 9/48──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-49590 (JP, A) JP-A-5-195079 (JP, A) JP-A-5-117758 (JP, A) JP-A-59-1979 140333 (JP, A) (58) Field surveyed (Int. Cl. 6 , DB name) C22C 38/00-38/60 C21D 9/46-9/48
Claims (1)
が鉄(Fe)および不可避不純物からなる化学成分組成を有
することを特徴とする、深絞り性と耐深絞り脆性とのバ
ランスの優れた連続焼鈍冷延鋼板。1. Carbon (C): less than 0.0030 wt.%, Manganese (Mn): 0.05 to 0.20 wt.%, Silicon (Si): 0.05 wt.% Or less, phosphorus (P): 0.02 wt.% Or less, Sulfur (S): 0.010 wt.% Or less, Soluble aluminum (sol.Al): 0.025 to 0.06 wt.%, Nitrogen (N): 0.0030 wt.% Or less, Titanium (Ti): 0.02 to less than 0.05 wt.% , Boron (B): 0.0003 to 0.0010 wt.%, And the following formulas (1) and (2): X = −ln ｛(C / Ti *) B｝ ──────── ─ (1) where Ti * = Ti-(48/14) N-(48/32) S ≥ 0 ── The value of X defined by (2) satisfies the range of 9.2 to 11.2, and the remainder is A continuously annealed cold-rolled steel sheet having an excellent balance between deep drawability and resistance to deep drawability, characterized by having a chemical composition of iron (Fe) and unavoidable impurities.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27312693A JP2864966B2 (en) | 1993-10-05 | 1993-10-05 | Continuously annealed cold rolled steel sheet with excellent balance between deep drawability and deep draw resistance |
| CA002149522A CA2149522C (en) | 1993-10-05 | 1994-10-05 | Continuously annealed cold-rolled steel sheet excellent in balance between deep drawability and resistance to secondary-work embrittlement and method for manufacturing same |
| US08/407,011 US5531839A (en) | 1993-10-05 | 1994-10-05 | Continously annealed cold-rolled steel sheet excellent in balance between deep drawability and resistance to secondary-work embrittlement and method for manufacturing same |
| PCT/JP1994/001663 WO1995009931A1 (en) | 1993-10-05 | 1994-10-05 | Continuously annealed and cold rolled steel sheet |
| CN94190734A CN1043905C (en) | 1993-10-05 | 1994-10-05 | Continuously annealed and cold rolled steel sheet |
| KR1019950702040A KR0165929B1 (en) | 1993-10-05 | 1995-05-19 | Continuously annealed and cold rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27312693A JP2864966B2 (en) | 1993-10-05 | 1993-10-05 | Continuously annealed cold rolled steel sheet with excellent balance between deep drawability and deep draw resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07102344A JPH07102344A (en) | 1995-04-18 |
| JP2864966B2 true JP2864966B2 (en) | 1999-03-08 |
Family
ID=17523494
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|---|---|---|---|
| JP27312693A Expired - Lifetime JP2864966B2 (en) | 1993-10-05 | 1993-10-05 | Continuously annealed cold rolled steel sheet with excellent balance between deep drawability and deep draw resistance |
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| Country | Link |
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| JP (1) | JP2864966B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106498139A (en) * | 2016-11-22 | 2017-03-15 | 首钢京唐钢铁联合有限责任公司 | Process method and device for producing IF steel |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103706646B (en) * | 2013-12-18 | 2015-10-28 | 首钢总公司 | A kind of gapless atomic steel connects the method for optimizing temper rolling technology moving back thin plate |
| CN105603299A (en) * | 2016-02-03 | 2016-05-25 | 首钢总公司 | Extra-deep drawing interstitial free steel and production method thereof |
| CN106282795B (en) * | 2016-08-30 | 2018-04-10 | 唐山钢铁集团有限责任公司 | A kind of high-strength IF steel band and its hot rolling production method |
| CN114525449A (en) * | 2022-01-28 | 2022-05-24 | 包头钢铁（集团）有限责任公司 | DC04 automobile steel plate for cold rolling deep drawing and manufacturing method thereof |
-
1993
- 1993-10-05 JP JP27312693A patent/JP2864966B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106498139A (en) * | 2016-11-22 | 2017-03-15 | 首钢京唐钢铁联合有限责任公司 | Process method and device for producing IF steel |
| CN106498139B (en) * | 2016-11-22 | 2018-11-09 | 首钢京唐钢铁联合有限责任公司 | Process method and device for producing IF steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07102344A (en) | 1995-04-18 |
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