JPH07102344A - Continuously annealed cold rolled steel sheet well balanced between deep drawability and resistance to deep drawing brittleness - Google Patents
Continuously annealed cold rolled steel sheet well balanced between deep drawability and resistance to deep drawing brittlenessInfo
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- JPH07102344A JPH07102344A JP5273126A JP27312693A JPH07102344A JP H07102344 A JPH07102344 A JP H07102344A JP 5273126 A JP5273126 A JP 5273126A JP 27312693 A JP27312693 A JP 27312693A JP H07102344 A JPH07102344 A JP H07102344A
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Abstract
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 extremely low carbon steel and having an extremely excellent balance between deep drawability and deep drawing brittleness resistance. 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 made it possible to produce extremely low-carbon steel in which the carbon (C) content in the steel is reduced to 30 ppm or less at a relatively low cost and in large quantities. The so-called IF (Interstitial Free) steel, which is made by adding Nb, Ti, B, and Zr to the ultra-low carbon steel, is for EDDQ class ultra-deep drawing that requires deep drawability and non-aging property in the continuous annealing process. It is becoming popular as an influential 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。The IF steel generally used as a continuous annealed cold rolled steel sheet is a steel in which Ti and Nb are added individually or in combination. Ti is a strong carbon / nitride forming element, and at the same time, S in steel also has a fixing action as a sulfide, so Ti-IF steel in particular has an extremely excellent deep drawing in a wide composition range. The feature is that the ductility and ductility are stably obtained. However, since Ti is easily oxidized, there is a problem of nozzle clogging during continuous casting and generation of slab surface defects due to Ti oxide. Also, when Ti in an amount sufficient to completely fix C in the steel as TiC is added, the grain boundary strength of the steel sheet after annealing decreases and the problem of deep drawing embrittlement (secondary work embrittlement) becomes apparent. To do. It is known that the addition of a trace amount of B is effective for the problem of deep drawing embrittlement, but the problem is that the deep drawing property deteriorates.
【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, the same excellent deep drawability as Ti-IF steel can be obtained, but there is a problem that the appropriate range of Nb content is narrower than that of Ti-IF steel. However, since oxide-based slab surface defects are less likely to be generated, there is an advantage that slab maintenance is not required and a hot rolled steel strip can be manufactured by direct feed rolling. Further, it is known that the adhesion of the alloy layer is improved as compared with the Ti-IF steel when the IF steel containing Nb alone or a composite addition of Ti is used as the original plate of the alloyed galvanized steel sheet. .
【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 technology for complementing the above-mentioned Ti-added IF steel and Nb-added IF steel, a composite addition technology for adding both Nb and Ti (Japanese Patent Publication No. 61-32375) is disclosed. The essence of the technology is 0.003 to 0.025 wt.% Nb and 0.010 to
0.037wt.% Ti, Nb> 2.33C, (48/14) (N −0.002) <
It is added under the condition of Ti <4 C +3.43 N, and the basic technology is to fix N as TiN and C as [Nb, Ti] C before finish 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。The addition of a trace amount of B to IF steel has been mostly limited in the cases disclosed in the second and subsequent claims in the previously disclosed patent applications. This is because B is an element that is extremely effective against secondary work embrittlement resistance, but on the other hand, it is an element that deteriorates the deep drawability required as an essential property of the steel sheet, so positive addition is not always necessary. This is because it is not a good idea. On the other hand, Japanese Patent Laid-Open No. 63-317625 discloses a technique for actively adding B to IF steel. This is an attempt to avoid the deterioration of deep drawability due to the addition of B by utilizing the structure refining effect of the weld heat affected zone, which is an unavoidable problem of IF steel. The system is an IF steel with a composite addition of Ti and Nb. Also, 2
A steel sheet that takes into consideration the secondary workability and surface treatment is disclosed in JP-A-59-140.
Japanese Unexamined Patent Publication No. 1-184227 discloses an alloyed hot-dip galvanized steel sheet for drawing. However, in view of the basic component design concept and action / effect, deep drawing property and resistance It is not a technology that considers the improvement of the 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, due to the complicated and large-sized parts of automobiles and the emphasis on rust prevention, they have been conventionally used only in parts with severe moldability (reactor etc.). The use ratio of EDDQ class cold rolled steel sheets for ultra deep drawing is increasing, and the EDDQ class steel sheets have come to be used in large quantities as general-purpose products. On the other hand, with the spread of the continuous annealing process, a manufacturing method using IF steel as a raw material is becoming common as the most effective method for manufacturing a cold-rolled steel sheet for non-aging super deep drawing in the process. But IF
If a large amount of steel is manufactured as a general-purpose product, as described above, there is a risk that problems peculiar to IF steel such as deep drawing embrittlement may become apparent, and it is necessary to give due consideration to the component design. In view of such an actual situation, the object of the present invention is to solve the above-mentioned problems, which is a contradictory property in IF steel, deep drawing formability, and most preferable in balancing deep drawing brittleness resistance. It is intended to provide a continuous annealed cold-rolled steel sheet having a well-balanced deep drawing property and deep drawing embrittlement resistance 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.
The best non-aging ultra-deep cold drawing with improved balance between deep drawability and deep drawing embrittlement resistance by improving IF steel based on ultra low carbon steel of less than wt%. It is related to rolled steel sheets, Ti (0.02 to 0.05 wt.%) And a small amount of B
Ultra low carbon steel containing (3 to 10 ppm) is an essential steel type, and Ti * (= Ti− (48/14) N− (48/32) S ≧ 0), C and
It is characterized by restricting the value of X (= −ln {(C / Ti *) B}) defined by the amount of B within an appropriate range, and it is possible to achieve the objective for the first time with such a chemical composition. It is possible, and the 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 continuous annealed cold-rolled steel sheet of the present invention having an excellent balance of deep drawability and deep drawing brittleness resistance is C: 0.0030 wt.%.
Less than, 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 to less than 0.05 wt.%, B: 0.0003 to 0.0010 wt.%, And the following:
(1), (2), X = −ln {(C / Ti *) B} ────────── (1) where Ti * = Ti− (48/14) N − (48 / 32) Characteristic that the value of X specified by S ≧ 0 ── (2) satisfies the range of 9.2 to 11.2, and the balance has a chemical composition of iron (Fe) and inevitable impurities 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 constituent element of the present invention is 0.0030.
About the chemical composition of the IF steel in which Ti in the range of 0.02 to 0.05 wt.% and B in the range of 3 to 10 ppm were added to the ultra-low carbon steel with a C content of less than wt.% The above
The value of X calculated by Eqs. (1) and (2) is limited to the range of 9.2 to 11.2, which allows continuous annealing and cooling with a good balance between deep drawability and deep drawing embrittlement resistance. 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 regard to the addition of carbon / nitride forming elements that are indispensable as IF steel, Ti is an essential addition element, but at the same time in the slab stage that affects the surface properties of the steel sheet of the relevant component system. Since the surface defect is caused by Ti, the content of Ti is limited. The surface defects of the slab are exacerbated as the amount of Ti added increases. In particular, strict control is required when performing direct feed rolling or the like. Figure 1 shows the pinhole defects that occur on the surface of a continuously cast slab of Ti-added ultra-low carbon steel.
It is a graph which showed the effect of a trace amount of Nb and B. As is clear from the figure, in the Ti-added steel, the pinhole defects generated on the surface of the continuously cast slab increase as the Ti content increases. Le defects are significantly reduced, and the effect is more remarkable than that of Nb added in combination. From such a point, in the present invention, the upper limit of the Ti content is set to less than 0.05 wt.% With the goal of eliminating defects in the slab by adding a trace amount of B 2. On the other hand, Ti is a strong nitride and sulfide forming element. In particular, N in steel is coarsely precipitated as TiN in the high temperature region. Therefore, by precipitating N as AlN after hot rolling, material variation in the longitudinal direction of the coil is improved. Therefore, the residuals deposited as nitrides and sulfides
As a condition under which Ti can precipitate and fix C in steel, the lower limit of the Ti content is 0.02 wt.%. Therefore, the content of Ti is 0.
It should be limited to the range of 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 at precipitating all of C in steel as carbosulfide having TiC or TiS as a nucleus. This is because it is essential to combine 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 Ti content range 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 the viewpoints of both, the C content is preferably 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: Si maintains the ductility of the steel sheet, so the content is limited to 0.05 wt.% Or less. (4) Since the content of Mn: Mn is fixed by Ti, it does not matter if it is lower than the normal level. Particularly, in order to precipitate the residual solid solution C 2 in the continuous annealing process, it is desirable that the Mn content is low, but if it is less than 0.05 wt.%, The hot metal pretreatment cost increases. On the other hand, in order to reduce the residual solid solution C and develop a texture preferable for deep drawability, it is necessary to set the content to 0.20 wt.% Or less. Therefore, the content of Mn is 0.05 to 0.20w
It should be limited to within 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 deep drawing embrittlement resistance, but in the present invention in which B is an essential additive element, the upper limit of its content is relaxed. However, in order to maintain the formability, it is necessary to suppress the adverse effect on ductility within a range that can be ignored. 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 Ti consumed as sulfide by S. Therefore, the S content 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: Al, in the steel of the present invention to which Ti is added, the content thereof may be reduced within the range where continuous casting is possible for the purpose of only fixing N. 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 the steel with Al. In order to exert such an effect, the Al content 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) It is desirable that the content of N: N is low in order to exert the material characteristics of IF steel. In particular, Ti * (= Ti- (48/14) N-
Decrease (48/32) S ≥ 0). 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 Ti-added IF steel as the base, the balance between deep drawability and deep drawing embrittlement is significantly improved compared to conventional steel sheets. Figure 2 shows Ti-added IF steel,
After the continuous annealing, the steel sheet with B added to each of the Nb-added IF steel and the Ti and Nb composite-added IF steel has three in-plane directions (0 °, 45 °).
°, 90 °) r-value minimum (r min ) and the drawing ratio of 2.2, and the deep-drawing embrittlement critical temperature (T th ) expressed in absolute temperature
2 is a graph in which the ratio (r min / T th ) of and is arranged by the B content in steel. As is clear from the figure, only when B is compounded with Ti content within the range of the present invention, r min / T th ≧ 0.015 is obtained when the B content is within the range of 3 to 10 ppm. Figure 3 shows r min / T for IF steels containing Ti and B.
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 within the range of 9.2 to 11.2.
Therefore, in the present invention, the addition of Ti is based on B
Content in the range of 3 to 10 ppm, and X [=
-Ln {(C / Ti *) B] should be limited to be in the range 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 characteristics of the steel of the present invention, it is essential to anneal it in a continuous annealing process. In that case, if the annealing temperature is the recrystallization temperature or higher, the characteristics of the steel of the present invention can be exhibited, but r min increases as the annealing is performed at a high temperature, so that the temperature range is just below the Ac 3 transformation point. Therefore, it is desirable to anneal at the highest temperature possible. Incidentally, the steel sheet disclosed in the present invention, various electroplating treatment step after continuous annealing, it is also possible to apply an organic coating step or 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 resistance to 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 by way of examples in comparison with comparative examples. (Example 1) Inventive steel Nos. 1 to 8 having chemical composition within the range of the present invention shown in Table 1 and comparative steel No. 1 having chemical composition outside the range of the present invention shown in Table 2. Continuously cast slabs of 1 to 20 are heated to 1200 ° C, rolled by rough rolling to a thickness of 36 mm, and then hot-rolled at a finishing temperature within the range of 890 to 920 ° C to obtain a thickness of A 3.2 mm steel plate was used. The hot-rolled steel strip thus obtained was wound at 620 ° C. The hot-rolled steel strip was pickled, cold-rolled to a thickness of 0.8 mm, and then continuously annealed in the temperature range of 840 to 850 ° C. The steel strip thus obtained was subjected to 0.5% temper rolling to produce a continuous annealed cold rolled steel strip. A test piece was taken from each of the continuously annealed cold rolled steel strips, and the in-plane three directions (0
Minimum r-value (r min ) at 45 °, 45 °, 90 °, aperture ratio 2.
The deep-drawing embrittlement critical temperature (T
th ) was measured and r min / T th was determined and is shown in Table 3. In addition, the occurrence status of the surface defects of the slab is also described. ◯ indicates that no defect has occurred, Δ indicates that a slight defect has occurred, and x indicates that a defect has occurred.
【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 Steel Nos. 7-9 having chemical composition outside the scope of the present invention,
Cold rolled steel sheets manufactured from 11, 17 and 18 have an r min of 2.0.
Although it was high and the deep drawability was excellent, T th was 153 to 223K.
At high temperature, the deep drawing embrittlement resistance deteriorates.
The cold-rolled steel sheet produced from o.1 to 6, 12 to 16, 19 and 20 had a low Tth of 133 K or less and excellent deep drawing embrittlement resistance, but had a low r min of 1.98 or less and deep drawing. Deteriorated
Therefore, the r min / T th values of all the comparative steels except No. 10 were low (0.015 or less), and the balance between the deep drawability and the deep drawing embrittlement resistance deteriorated. The cold-rolled steel sheet manufactured from Comparative Steel No. 10 was excellent in 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 the cold-rolled steel sheets manufactured from the invention steel Nos. 1 to 8 having the chemical composition within the range of the present invention have a high r min of 2.0 or more and an excellent deep drawability. T th is 133 K or less, which is a low temperature, and the deep drawing embrittlement resistance is excellent, and r min / T th is 0.015 or more, which is a balance between the deep drawing property and the deep drawing embrittlement resistance. Was excellent. Furthermore, no defects were generated on the surface of the slab, which 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 to 8 and the continuous cast slabs of comparative steel Nos. 7 to 10 and 17 to 20 shown in Table 2 are directly rolled without heating.
(Hot rolling) was performed. After rolling to 36mm by rough rolling,
As in Example 1, the finishing thickness is 3.2 mm and the finishing temperature is
Hot rolling was carried out under the conditions of 870 to 910 ° C, and the hot-rolled steel strip thus obtained was wound at 660 ° C. The hot-rolled steel strip was pickled, cold-rolled to a thickness of 0.8 mm, and then continuously annealed in the temperature range of 840 to 850 ° C. The steel strip thus obtained was subjected to 0.5% temper rolling to produce a continuous annealed cold rolled steel strip. A test piece was taken from each of the continuously annealed cold rolled steel strips, and the in-plane three directions (0
Minimum r-value (r min ) at 45 °, 45 °, 90 °, aperture ratio 2.
The deep-drawing embrittlement critical temperature (T
(th ) was measured, and r min / T th was calculated and shown in Table 4. The density of pinhole defects on the slab surface
(Indicator) 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 apparent from Tables 1, 2 and 4, even when the continuously cast slab is hot-rolled by direct feeding, the result is outside the scope of the present invention, as in the result obtained in Example 1. Cold-rolled steel sheet produced from steel having a chemical composition of, because either deep drawing resistance or deep drawing brittleness is inferior,
The balance between deep drawability and deep draw resistance was poor. Furthermore, pinhole defects often occurred on the slab surface. On the other hand, the cold-rolled steel sheet produced from the steel having the chemical composition within the scope of the present invention has excellent deep drawability and deep drawing embrittlement resistance, and moreover, with deep drawing property and deep drawing embrittlement resistance. The balance was excellent. Further, no pinhole defect was 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 above in detail, in the present invention, a steel having a chemical composition containing an appropriate amount of Ti and B, etc. was developed based on an ultra-low C steel, and a composite of B and Ti was developed. Since the addition of IF steel has been improved by the addition, continuous annealing cold-rolled steel sheet with excellent balance between the deep drawing property and the deep drawing embrittlement resistance, which are the contradictory properties of IF steel, can be mass-produced at low cost, efficiently and stably. It is possible to obtain industrially useful effects.
【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 a trace amount of Nb and B on the pinhole defects generated on the surface of a continuously cast slab of a 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-Nb composite-added
Minimum r value (r min ) in the 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 the deep drawing critical temperature (T th ) evaluated by absolute temperature
2 is a graph in which the ratio (r min / T th ) of and is arranged by the B content in steel.
【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 shows a value of r min / T th in an IF steel containing Ti and B, which is determined by the chemical composition in the steel X [= −ln {(C / Ti
*) B, where Ti * = Ti- (48/14) N- (48/32) S ≥ 0]
It is a graph organized by.
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) However, Ti * ＝ Ti− (48/14) N − (48/32) S ≧ 0 ─── The value of X specified in (2) satisfies the range of 9.2 to 11.2, and the balance is A continuous annealed cold-rolled steel sheet having an excellent balance between deep drawability and deep drawing embrittlement resistance, which has a chemical composition of iron (Fe) and inevitable 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 |
| CN94190734A CN1043905C (en) | 1993-10-05 | 1994-10-05 | Continuously annealed and cold rolled steel sheet |
| 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 |
| 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 true JPH07102344A (en) | 1995-04-18 |
| JP2864966B2 JP2864966B2 (en) | 1999-03-08 |
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ID=17523494
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|---|---|---|---|
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| Country | Link |
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| CN105603299A (en) * | 2016-02-03 | 2016-05-25 | 首钢总公司 | Extra-deep drawing interstitial free steel and production method thereof |
| CN106282795A (en) * | 2016-08-30 | 2017-01-04 | 唐山钢铁集团有限责任公司 | A kind of high-strength IF steel band and hot rolling production method thereof |
| 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 |
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-
1993
- 1993-10-05 JP JP27312693A patent/JP2864966B2/en not_active Expired - Lifetime
Cited By (5)
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| CN103706646A (en) * | 2013-12-18 | 2014-04-09 | 首钢总公司 | Leveling process optimization method for continuously-annealed interstitial free steel sheets |
| 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 |
| CN106282795A (en) * | 2016-08-30 | 2017-01-04 | 唐山钢铁集团有限责任公司 | A kind of high-strength IF steel band and hot rolling production method thereof |
| 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 |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2864966B2 (en) | 1999-03-08 |
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