JP2001026842A - Cold rolled steel sheet excellent in surface property and internal property and its production - Google Patents
Cold rolled steel sheet excellent in surface property and internal property and its productionInfo
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- JP2001026842A JP2001026842A JP19655299A JP19655299A JP2001026842A JP 2001026842 A JP2001026842 A JP 2001026842A JP 19655299 A JP19655299 A JP 19655299A JP 19655299 A JP19655299 A JP 19655299A JP 2001026842 A JP2001026842 A JP 2001026842A
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- oxide
- inclusions
- steel sheet
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、表面性状および内
質に優れる冷延鋼板、とくに鋼中の酸化物系介在物の組
成を制御して、介在物起因によるプレス割れに対する抵
抗性を高めた冷延鋼板およびその製造方法に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-rolled steel sheet having excellent surface properties and internal quality, in particular, by controlling the composition of oxide-based inclusions in steel to improve the resistance to press cracking due to inclusions. The present invention relates to a cold-rolled steel sheet and a method for producing the same.
【０００２】[0002]
【従来の技術】鋼の脱酸は、当初、特公昭44−18066 号
公報に開示されているように、AlではなくFe-Ti で行わ
れていた。しかし近年では、酸素濃度の安定した鋼を低
コストで製造するために、Alを0.005 wt％以上含有させ
るAl脱酸鋼が主流となっている。2. Description of the Related Art Steel is initially deoxidized with Fe-Ti instead of Al, as disclosed in Japanese Patent Publication No. 44-18066. However, in recent years, in order to produce steel with stable oxygen concentration at low cost, Al deoxidized steel containing Al in an amount of 0.005 wt% or more has become mainstream.
【０００３】鋼のAl脱酸は、ガス攪拌やＲＨ脱ガス装置
を用い、生成酸化物を凝集、合体させて、浮上分離する
方法であるが、この場合、鋳片中にはAl2O3 酸化物が不
可避に残留することになる。しかも、このAl2O3 はクラ
スター状になるため、分離しにくく、時には数100 μｍ
以上ものクラスター状介在物が残留する。もし、このよ
うなクラスター状の介在物が鋳片表層部に捕捉される
と、ヘゲ, スリーバのような表面欠陥につながることに
なるから、美麗さを必要とする自動車用鋼板では致命的
な欠陥となる。また、Al脱酸では、Al2O3 がタンディシ
ュからモールドへ注入するために使用するイマージョン
ノズルの内壁に付着し、ノズル閉塞をひき起こすという
問題があった。[0003] Al deoxidation of steel is a method of aggregating and coalescing oxides produced by gas agitation or an RH degassing apparatus to separate them by flotation. In this case, Al 2 O 3 is contained in a slab. Oxides will inevitably remain. Moreover, since this Al 2 O 3 is clustered, it is difficult to separate, and sometimes several hundred μm.
The above cluster-like inclusions remain. If such cluster-like inclusions are trapped in the surface layer of the slab, they will lead to surface defects such as scabs and slivers. It becomes a defect. In addition, Al deoxidation has a problem in that Al 2 O 3 adheres to an inner wall of an immersion nozzle used for injecting the material from a tundish into a mold, causing nozzle clogging.
【０００４】このようなAl脱酸に伴う上述した問題に対
し、アルミキルドした溶鋼中にCaを添加することによ
り、CaO , Al2O3 複合酸化物を生成させる方法が提案さ
れている。 (例えば、特開昭61−276756号公報, 特開昭
58−154447号公報および特開平6−49523 号公報) 。こ
の方法におけるCa添加の目的は、Al2O3 とCaとを反応さ
せて、CaOAl2O3, 12CaOAl2O3, 3CaOAl2O3 等の低融点複
合酸化物を形成することにより、上述した問題点を克服
しようとするものである。[0004] In order to solve the above-mentioned problems associated with Al deoxidation, a method has been proposed in which Ca is added to aluminum-killed molten steel to produce a CaO, Al 2 O 3 composite oxide. (For example, Japanese Patent Application Laid-Open No. 61-276756,
58-1554447 and JP-A-6-49523). The purpose of Ca addition in this method was described above by reacting Al 2 O 3 and Ca to form low melting point composite oxides such as CaOAl 2 O 3 , 12CaOAl 2 O 3 , 3CaOAl 2 O 3 . It tries to overcome the problem.
【０００５】しかしながら、溶鋼中へCaを添加すると、
このCaが鋼中のＳと反応してCaＳを形成し、このCaＳが
発錆の原因をつくる。この点、特開平６−559 号公報で
は、発錆を防止するために、鋼中に残留するCa量を5 pp
m 以上10ppm 未満とする方法を提案している。しかし、
Ca量を10ppm 未満にしたとしても、鋼中に残留するCaＯ
−Al2O3 系酸化物の組成が適正でない場合、特にCaO 濃
度が30％以上の酸化物の場合、その酸化物中のＳの溶解
度が増加し、温度低下時や凝固時に介在物内周囲にCaＳ
が不可避に生成する。その結果、そのCaＳが起点となっ
て錆が発生し、製品板の表面性状の劣化を招くようにな
る。また、このような発錆点が残留したまま、めっきあ
るいは塗装のような表面処理を行うと、処理後にどうし
ても表面ムラが発生する。一方で、介在物中のCaO 濃度
が20％以下と低くかつAl2O3 濃度が高い場合、特にAl2O
3 濃度が70％以上の場合には、介在物の融点が上がり、
介在物どうしが焼結しやすくなるため、連続鋳造時にノ
ズル詰まりが発生しやすくなるだけでなく、鋼板表面に
はヘゲ, スリーバ等が発生し、表面性状を著しく悪化さ
せるという問題があった。[0005] However, when Ca is added to molten steel,
The Ca reacts with S in the steel to form CaS, and the CaS causes rust. In this regard, in Japanese Patent Application Laid-Open No. 6-559, in order to prevent rusting, the amount of Ca remaining in steel is reduced to 5 pp.
It proposes a method to reduce the concentration to m or more and less than 10 ppm. But,
Even if the Ca content is less than 10 ppm, CaO remaining in the steel
When the composition of -al 2 O 3 based oxide is not proper, especially in the case of CaO concentrations oxide 30% or more, its solubility S in the oxides increases, inclusions within the perimeter at the time and the solidification temperature drop To CaS
Is inevitably generated. As a result, rust is generated from the CaS as a starting point, leading to deterioration of the surface properties of the product plate. In addition, if surface treatment such as plating or painting is performed with such rusting points remaining, surface unevenness will inevitably occur after the treatment. On the other hand, if the high and the concentration of Al 2 O 3 CaO concentration is as low as 20% or less in inclusions, in particular Al 2 O
3 When the concentration is 70% or more, the melting point of inclusions increases,
Since inclusions are easily sintered, not only nozzle clogging is liable to occur during continuous casting, but also barges and slivers are generated on the surface of the steel sheet.
【０００６】これに対し、近年に至り、Alを添加せず
に、Tiで脱酸する方法が、特開平８−239731号公報とし
て開発されている。このようなAlレスTi脱酸の方法は、
Al脱酸法に比べ、到達酸素濃度が高く介在物量は多い
が、クラスター状の酸化物は生成しない。とくに生成す
る介在物の形態がTi酸化物−Al2O3 系となり、２〜50μ
ｍ程度の粒状の酸化物が分散した状態を呈する。そのた
め、介在物がクラスター状になることに起因する上述し
た表面欠陥は減少する。しかしながら、このTi脱酸の場
合、Al≦0.005 wt％の溶鋼では、Ti濃度が0.010 wt％以
上になると、固相状態のTi酸化物がタンディッシュノズ
ルの内面に地金を取り込んだ形で付着成長し、かえって
ノズルの閉塞を誘発するという新たな問題があった。On the other hand, in recent years, a method of deoxidizing with Ti without adding Al has been developed as JP-A-8-239731. The method of such Al-less Ti deoxidation is as follows:
Compared to the Al deoxidation method, the reached oxygen concentration is higher and the amount of inclusions is larger, but no cluster oxide is generated. In particular, the form of the inclusions generated is Ti oxide-Al 2 O 3 system, 2 ~ 50μ
It exhibits a state in which about m granular oxides are dispersed. Therefore, the above-mentioned surface defects due to inclusions being clustered are reduced. However, in the case of this Ti deoxidation, in the molten steel with Al ≤ 0.005 wt%, when the Ti concentration becomes 0.010 wt% or more, the solid state Ti oxide adheres to the inner surface of the tundish nozzle by taking in the metal. There was a new problem of growing and instead causing nozzle blockage.
【０００７】このような問題 (ノズルの閉塞防止) を解
決するために、特開平８−281391号公報では、AlレスTi
脱酸鋼において、ノズルを通過する溶鋼の酸素量を制限
することにより、ノズル内面に成長するTi2O3 の成長を
防止する方法を提案している。しかし、この方法の場
合、酸素量の制限にも限界があることから、処理量が限
られる(800トン程度) という別の問題があった。また、
閉塞の進行とともにモールド内湯面のレベル制御が不安
定になるため、根本的な解決にはなっていないのが実情
である。In order to solve such a problem (prevention of nozzle blockage), Japanese Patent Laid-Open No. 8-281391 discloses an Al-less Ti
In deoxidized steel, a method has been proposed to prevent the growth of Ti 2 O 3 growing on the inner surface of the nozzle by limiting the oxygen content of molten steel passing through the nozzle. However, in this method, there is another problem that the treatment amount is limited (about 800 tons) because the limitation of the oxygen amount is also limited. Also,
The fact is that the level control of the molten metal level in the mold becomes unstable with the progress of the blockage, so that it is not a fundamental solution.
【０００８】また、この特開平８−281390号公報に開示
の技術は、タンディッシュノズルの閉塞防止策として、
溶鋼のSi濃度を適正化して介在物組成をTi3O5-SiO2系に
することにより、ノズル内面に成長するTi2O3 の成長を
防止する方法を提案している。しかし、単にSi濃度を増
加しても介在物中にSiO2を含有させることは難しく、少
なくとも (wt％Si) ／ (wt％Ti) ＞50を満足するように
しなければならない。したがって、鋼中のTi濃度が0.01
0 wt％の場合、SiO2−Ti酸化物を得るためには、Si濃度
は0.5 wt％以上が必要となる。しかし、Siの増加は材質
の硬化を招き、また、めっき性の劣化を招く。Si濃度の
増加は鋼板表面性状への悪影響が大きくなり、根本的な
解決方法を提供するものではない。The technique disclosed in Japanese Patent Application Laid-Open No. 8-281390 discloses a technique for preventing blockage of a tundish nozzle.
By the composition of inclusions by optimizing the Si concentration of the molten steel Ti 3 O 5 -SiO 2 system, it has proposed a method of preventing the growth of Ti 2 O 3 to grow the nozzle inner surface. However, it is difficult to make the inclusions contain SiO 2 simply by simply increasing the Si concentration, and it is necessary to satisfy at least (wt% Si) / (wt% Ti)> 50. Therefore, the Ti concentration in steel is 0.01
In the case of 0 wt%, in order to obtain a SiO 2 —Ti oxide, the Si concentration needs to be 0.5 wt% or more. However, an increase in Si causes hardening of the material and also causes deterioration in plating property. An increase in the Si concentration has an adverse effect on the surface properties of the steel sheet, and does not provide a fundamental solution.
【０００９】次に、特公平７−47764 号公報では、Mn：
0.03〜1.5 wt％、Ti：0.02〜1.5 wt％となるように脱酸
することにより、MnO を17〜31wt％含有する MnO−Ti酸
化物からなる低融点の介在物を含有する非時効性冷延鋼
板を提案している。この提案の場合、上記 MnO−Ti酸化
物は低融点であり、溶鋼中では液相状態となるため、溶
鋼がタンディッシュノズルを通過してもノズルに付着す
ることなくモールドに注入されるので、タンディッシュ
ノズルの閉塞を効果的に防止できる。しかしながら、森
岡泰行, 森田一樹ら：鉄と鋼, 81(1995), p.40の報告に
あるように、MnO ：17〜31％含有する MnO−Ti酸化物を
得るためには、Mn, Tiの酸素との親和力の違いから、溶
鋼中のMnとTiの濃度比を、 (wt％Mn) ／ (wt％Ti) ＞10
0 にする必要がある。したがって、鋼中のTi濃度が0.01
0 wt％の場合、所要のMnO −Ti酸化物を得るためには、
Mn濃度は1.0 wt％以上が必要である。しかし、Mn含有量
が1.0 wt％を超えると材質が硬化する。従って、MnO を
17〜31wt％含有する MnO−Ti酸化物の介在物を形成する
ことは実際上困難であった。Next, in Japanese Patent Publication No. 7-47764, Mn:
By deoxidizing so as to be 0.03 to 1.5 wt% and Ti: 0.02 to 1.5 wt%, non-aging cold containing low melting point inclusions made of MnO-Ti oxide containing 17 to 31 wt% of MnO 2. We have proposed rolled steel sheets. In the case of this proposal, the MnO-Ti oxide has a low melting point and is in a liquid phase state in molten steel, so that even when the molten steel passes through the tundish nozzle, it is injected into the mold without adhering to the nozzle. Blockage of the tundish nozzle can be effectively prevented. However, as reported by Yasuyuki Morioka, Kazuki Morita et al .: Iron and Steel, 81 (1995), p. 40, in order to obtain a MnO-Ti oxide containing MnO: 17-31%, Mn, Ti From the difference in affinity between oxygen and oxygen, the concentration ratio of Mn and Ti in the molten steel was calculated as follows: (wt% Mn) / (wt% Ti)> 10
Must be 0. Therefore, the Ti concentration in steel is 0.01
In the case of 0 wt%, in order to obtain the required MnO-Ti oxide,
Mn concentration must be 1.0 wt% or more. However, if the Mn content exceeds 1.0 wt%, the material hardens. Therefore, MnO
It was practically difficult to form inclusions of MnO-Ti oxide containing 17-31 wt%.
【００１０】さらに、特開平８−281394号公報では、Al
レスTi脱酸鋼においてタンディッシュノズルの閉塞の防
止策として、ノズルに CaO・ZrO2粒を含有する材料を用
いることにより、溶鋼中のTi3O5 がノズルに捕捉された
場合、TiO2−SiO2−Al2O3 −CaO −ZrO2系の低融点介在
物にしてその成長を防止する方法を提案している。しか
しながら、溶鋼中の酸素濃度が高い場合、付着介在物の
TiO2濃度が高くなって低融点化しないため、ノズル閉塞
を防止することにはつながらず、一方で酸素濃度が低い
場合には、ノズルが溶損する問題があり、十分な対策に
はなっていない。[0010] Further, in Japanese Patent Application Laid-Open No. 8-281394, Al
As prevention of clogging of the tundish nozzle in less Ti-deoxidized steel, by using a material containing CaO · ZrO 2 grains in the nozzle, if the Ti 3 O 5 in the molten steel was trapped in the nozzle, TiO 2 - A method has been proposed in which a low melting point inclusion of the SiO 2 —Al 2 O 3 —CaO—ZrO 2 system is used to prevent its growth. However, when the oxygen concentration in the molten steel is high,
Since the TiO 2 concentration is high and the melting point is not lowered, it does not prevent nozzle clogging.On the other hand, when the oxygen concentration is low, there is a problem that the nozzle is melted, and it is not a sufficient measure .
【００１１】また、上掲のノズル詰まり防止に関する各
従来技術は、連続鋳造プロセスにおいて、溶鋼をタンデ
ィッシュノズルからモールドへ注入するための浸漬ノズ
ルには依然としてArガスやN2ガスを吹き込んで鋳造する
必要がある。しかし、その吹き込んだガスが鋳片の凝固
シェルに捕捉され、気泡性欠陥になるという問題が残さ
れていた。さらに、重要なことは、従来の形態制御方法
で粒状の介在物にすると、これが鋼板に残留した場合、
従来のクラスター状介在物では起こり難かったプレス割
れが発生しやすくなり、大きな問題となることがあっ
た。[0011] Further, in the above-mentioned prior arts relating to nozzle clogging prevention, in a continuous casting process, an immersion nozzle for injecting molten steel from a tundish nozzle into a mold is still cast by blowing Ar gas or N 2 gas. There is a need. However, there remains a problem that the blown gas is trapped by the solidified shell of the slab and becomes a cellular defect. What is more important is that if the conventional form control method is used to make granular inclusions,
Press cracking, which is difficult to occur with conventional cluster-like inclusions, is likely to occur, which may be a serious problem.
【００１２】[0012]
【発明が解決しようとする課題】本発明は、従来技術が
抱える上述した問題点を解決課題とするものであり、ク
ラスター状介在物等による表面欠陥が発生しにくく、大
型粒状の介在物に起因するプレス割れが生じがたい、表
面性状、内質ともに良好な冷延鋼板とその製造技術を提
案することにある。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is difficult to generate surface defects due to cluster-like inclusions and the like. It is an object of the present invention to propose a cold-rolled steel sheet having good surface properties and good internal quality, and a manufacturing technique therefor, which hardly causes press cracking.
【００１３】[0013]
【課題を解決するための手段】発明者らは、上記の目的
を達成すべく鋭意研究を重ねた結果、以下の結論を導く
に到った。 １）鋼板の表面性状を向上させるためには、介在物を低
融点化して、連鋳におけるノズル詰まりを抑制すること
により、パウダー巻き込み、気泡の付着を抑制すること
が必要である。 ２）鋼板内部の粒状介在物を特定の組成にすれば、介在
物の凝集を抑制することが可能となる。この特定組成範
囲を外れると、介在物が急速に凝集して、粗大化しやす
くなる。 ３）介在物組成は、溶鋼の組成によって一義的に定まる
ものではなく、速度論的に決まり、ＲＨ脱ガスなどの二
次精錬処理中の攪拌以外に、特に脱酸剤の添加時期に影
響される。この添加時期は、Al添加後に生成する Al2Ｏ
3 が核となり、その後に形成されるTi−Ca−Al−Ｏ系介
在物の組成や粒径に大きく影響を及ぼす。Means for Solving the Problems The inventors have conducted intensive studies to achieve the above object, and as a result, have reached the following conclusions. 1) In order to improve the surface properties of the steel sheet, it is necessary to reduce the melting point of inclusions and suppress nozzle clogging in continuous casting, thereby suppressing powder entrapment and air bubble adhesion. 2) If the granular inclusions inside the steel sheet have a specific composition, it is possible to suppress the aggregation of the inclusions. When the content is out of the specific composition range, the inclusions are rapidly aggregated, and are likely to be coarse. 3) The composition of the inclusions is not uniquely determined by the composition of the molten steel, but is determined kinetically, and is affected by the timing of addition of the deoxidizing agent in addition to the stirring during the secondary refining treatment such as RH degassing. You. This addition is performed at the time of Al 2 O
3 becomes a nucleus, and greatly affects the composition and particle size of the Ti-Ca-Al-O-based inclusions formed thereafter.
【００１４】このような知見の下に開発した本発明は、
Ｃ≦0.010 wt％、Si≦1.0 wt％、Mn≦3.0 wt％、Ｐ≦0.
15wt％、Ｓ≦0.05wt％、Al＜0.01wt％、Ｎ≦0.01wt％、
0.015 wt％≦Ti≦0.1 wt％、Caおよび／または金属ＲＥ
Ｍ≧0.0005wt％を含み、残部はFeおよび不可避的不純物
よりなる成分組成であり、50μｍ以下の大きさを有す
る、粒状または破断状の酸化物系介在物の組成が Al2Ｏ
3 ：10〜30wt％、Caおよび／または金属ＲＥＭの酸化
物：5 〜30wt％、Ti酸化物：50〜90wt％であることを特
徴とする、表面性状および内質に優れる冷延鋼板であ
る。The present invention developed based on such knowledge,
C ≦ 0.010 wt%, Si ≦ 1.0 wt%, Mn ≦ 3.0 wt%, P ≦ 0.
15wt%, S ≦ 0.05wt%, Al <0.01wt%, N ≦ 0.01wt%,
0.015 wt% ≦ Ti ≦ 0.1 wt%, Ca and / or metal RE
M ≧ 0.0005 wt%, and the balance is a component composition of Fe and unavoidable impurities. The composition of the particulate or fractured oxide-based inclusion having a size of 50 μm or less is Al 2 O.
3 : A cold-rolled steel sheet having excellent surface properties and internal quality, characterized by 10 to 30 wt%, oxide of Ca and / or metal REM: 5 to 30 wt%, and Ti oxide: 50 to 90 wt%. .
【００１５】また、上記発明鋼板は、出鋼後の溶鋼をAl
およびTiにより脱酸したのちCaおよび／またはＲＥＭを
添加する工程を経て製造するに当たり、Al添加前の酸素
の量と、Alを添加してからTiを添加するまでの時間との
間に、ａO ／ｔ≦１００（ただし、ａO ：Al添加前の酸
素の量（ｐｐｍ）、ｔ：Alを添加してからTiを添加する
までの時間（ｍｉｎ））の関係が成り立つようにして添
加することにより製造される。Further, the steel sheet according to the invention is characterized in that the molten steel after tapping is made of Al
In the production through the step of adding Ca and / or REM after deoxidation with Ti and Ti, between the amount of oxygen before the addition of Al and the time from the addition of Al to the addition of Ti, a O 2 / t ≦ 100 (however, a O : the amount of oxygen (ppm) before the addition of Al, t: the time (min) from the addition of Al to the addition of Ti) so as to satisfy the relationship. It is manufactured by
【００１６】[0016]
【発明の実施の形態】次に、本発明の構成要件を上記範
囲に限定した理由について説明する。 (a) Ｃ≦0.010 wt％ Ｃは、少なければ少ないほど深絞り性が向上し、その含
有量を0.010 wt％以下とすることで良好な成形性が得ら
れるので、0.010 wt％以下とした。Next, the reason why the constituent elements of the present invention are limited to the above range will be described. (a) C ≦ 0.010 wt% As the smaller the content of C, the deeper the drawability, the better the formability can be obtained by setting the content to 0.010 wt% or less.
【００１７】(b) Si≦1.0 wt％ Siは、鋼を強化する作用があり、所望の強度に応じて必
要量を含有させるが、その含有量が1.0 wt％を超えると
深絞り性が低下するので、1.0 wt％以下に限定した。(B) Si ≦ 1.0 wt% Si has an effect of strengthening steel, and contains a necessary amount according to a desired strength. However, if the content exceeds 1.0 wt%, deep drawability deteriorates. Therefore, the content was limited to 1.0 wt% or less.
【００１８】(c) Mn≦3.0 wt％ Mnは、鋼を強化する作用があり、所望の強度に応じて必
要量を含有させるが、その含有量が3.0 wt％を超えると
深絞り性が低下するので、3.0 wt％以下に限定した。な
お、好ましい範囲は0.01〜2.0 wt％である。(C) Mn ≦ 3.0 wt% Mn has the effect of strengthening the steel and contains a necessary amount according to the desired strength. However, if the content exceeds 3.0 wt%, the deep drawability decreases. Therefore, it was limited to 3.0 wt% or less. In addition, a preferable range is 0.01 to 2.0 wt%.
【００１９】(d) Ｐ≦0.15wt％ Ｐは、鋼を強化する作用があり、所望の強度に応じて必
要量を含有させるが、その含有量が0.15wt％を超える
と、深絞り性が低下するので0.15wt％以下に限定した。(D) P ≦ 0.15 wt% P has the effect of strengthening steel and contains a necessary amount according to the desired strength. If the content exceeds 0.15 wt%, the deep drawability becomes poor. The content was limited to 0.15% by weight or less because it decreased.
【００２０】(e) Ｓ≦0.05wt％ Ｓは、少ないほど深絞り性が向上するので好ましいが、
その含有量が0.05wt％以下であれば、さほど悪影響が出
ないので、0.05wt％以下に限定した。(E) S ≦ 0.05 wt% It is preferable that S is smaller, since the deep drawability is improved.
If the content is 0.05 wt% or less, there is no significant adverse effect, so the content is limited to 0.05 wt% or less.
【００２１】(f) Al＜0.01wt％ Alは、本発明においては重要な役割りを担う成分であ
る。0.01wt％以上では、Al脱酸になり、巨大 Al2Ｏ3 ク
ラスターが多量に生成し、表面性状を劣化させる。ま
た、冷延一焼鈍時の粒成長性を制御できる50μｍ以下の
微細酸化物が少なくなるため、強度−伸びバランスが低
下する。したがって、Al含有量は0.01wt％未満とした。(F) Al <0.01 wt% Al is a component that plays an important role in the present invention. If the content is 0.01 wt% or more, Al deoxidation occurs, and a large amount of giant Al 2 O 3 clusters are generated, deteriorating the surface properties. Further, the amount of fine oxide of 50 μm or less that can control the grain growth during cold rolling and annealing is reduced, and the strength-elongation balance is reduced. Therefore, the Al content was less than 0.01 wt%.
【００２２】(g) Ｎ≦0.01wt％ Ｎは、少ないほど深絞り性が向上するので低減するのが
好ましいが、その含有量が0.01wt％以下であれば、さほ
ど悪影響を及ぼさないので、0.01wt％以下に限定した。(G) N ≦ 0.01 wt% It is preferable to reduce the N content because the smaller the content, the better the deep drawability is. However, if the content of N is 0.01 wt% or less, there is no significant adverse effect. It was limited to wt% or less.
【００２３】(h) 0.015 wt％≦Ti≦0.1 wt％ Tiは、本発明鋼板において重要な元素であり、Ti脱酸に
より、50μｍ以下のサイズの微細な酸化物系介在物を形
成させ、冷延−焼鈍時の粒成長性を制御して、強度−伸
びバランスを向上させる成分である。さらに、この微細
酸化物は、熱延板の微細化にも有効に作用するため、冷
延−焼鈍後に｛１１１｝再結晶集合組織が発達してｒ値
が向上する。このTi含有量が0.015 wt％未満では、添加
の効果、即ち微細酸化物の量が少なすぎるため、所望の
効果が得られなくなるので、下限を0.015 wt％に限定し
た。一方、0.1wt ％を超えて添加すると材質が硬化して
成形加工性を損なうほか、コスト上昇をも招くので、上
限を0.1wt ％とした。(H) 0.015 wt% ≦ Ti ≦ 0.1 wt% Ti is an important element in the steel sheet of the present invention. By deoxidizing Ti, fine oxide-based inclusions having a size of 50 μm or less are formed, A component that controls grain growth during elongation-annealing and improves strength-elongation balance. Further, since this fine oxide effectively acts on miniaturization of a hot-rolled sheet, {111} recrystallization texture develops after cold rolling and annealing, and the r-value is improved. If the Ti content is less than 0.015 wt%, the desired effect cannot be obtained because the effect of addition, that is, the amount of the fine oxide is too small, so the lower limit is limited to 0.015 wt%. On the other hand, if added in excess of 0.1% by weight, the material is hardened and the moldability is impaired, and the cost is increased. Therefore, the upper limit is set to 0.1% by weight.
【００２４】(i) Caおよび／または金属ＲＥＭ≧0.0005
wt％（合計量） Caおよび金属ＲＥＭは、本発明において重要な元素であ
り、CaおよびＲＥＭのいずれか１種または２種を合計で
0.0005wt％以上添加する必要がある。すなわち、溶鋼を
Ti脱酸した後、さらにCaおよびＲＥＭのいずれか１種ま
たは２種を合計で0.0005wt％以上添加することにより、
Ti−Ca−Al−Ｏ系の低融点の酸化物系介在物に調整でき
る。このような調整を行うと、連続鋳造時に、地金を含
んだTi酸化物のノズルへの付着を阻止して、ノズル閉塞
を防ぐことができる。さらに、CaＯおよび／またはＲＥ
Ｍ酸化物は、冷延−焼鈍後の粒成長および熱延板の細粒
化にも寄与する。なお、過剰なCa、ＲＥＭの添加は鋼板
の発錆を引き起こす原因ともなるので、0.005 wt％以下
（合計量）の範囲で添加するのが望ましい。(I) Ca and / or metal REM ≧ 0.0005
wt% (total amount) Ca and metal REM are important elements in the present invention, and any one or two of Ca and REM are used in total.
It is necessary to add 0.0005 wt% or more. In other words, molten steel
After Ti deoxidation, one or more of Ca and REM are added by a total of 0.0005 wt% or more,
It can be adjusted to Ti-Ca-Al-O-based low melting point oxide-based inclusions. By performing such adjustment, it is possible to prevent the Ti oxide containing the base metal from adhering to the nozzle during continuous casting, thereby preventing nozzle blockage. In addition, CaO and / or RE
The M oxide also contributes to grain growth after cold rolling and annealing and grain refinement of a hot rolled sheet. Since excessive addition of Ca and REM may cause rusting of the steel sheet, it is preferable to add Ca and REM in an amount of 0.005 wt% or less (total amount).
【００２５】(2) 鋼板中の介在物 本発明では、鋼中の介在物の組成を Al2O3：10〜30wt
％、Caおよび／または金属ＲＥＭの酸化物：5 〜30wt
％、Ti酸化物：50〜90wt％とすることによって、介在物
を低融点化し、かつ、溶鋼との濡れ性を増加させること
により、介在物の凝集性を低下させる。その結果、鋳片
の大型粒状介在物が残留しなくなり、最終的には、鋼板
のプレス割れが防止され、プレス性の向上が達成され
る。図１に、TiO2−CaO −A12O3 系状態図を示す。この
状態図から低融点の組成となるのは、とくにTiO2：Al2O
3 ：CaO の重量比が７：1.5 ：1.5 の付近にある。この
ような傾向をもとにしてさらに検討を行い、本発明で
は、低融点組成範囲として、Al2O3 ：10〜30wt％、Caお
よび／または金属ＲＥＭの酸化物：5 〜30wt％（合計
量）、Ti酸化物：50〜90wt％と定めた。この範囲から外
れる組成では、タンディッシュより前の工程では介在物
は液相であるが、鋳型では溶鋼温度が低下するため、介
在物は固体となって急速に凝集が進行し、大型介在物を
生成するようになる。このようにして、本発明による組
成範囲では、大型介在物の生成が抑制され、プレス割れ
を抑制することが可能になる。(2) Inclusions in Steel Sheet In the present invention, the composition of inclusions in the steel is Al 2 O 3 : 10 to 30 wt.
%, Oxide of Ca and / or metal REM: 5-30 wt%
%, Ti oxide: 50 to 90 wt% to lower the melting point of the inclusions and increase the wettability with the molten steel, thereby reducing the cohesiveness of the inclusions. As a result, large-sized particulate inclusions in the slab do not remain, and finally press cracking of the steel sheet is prevented, and the pressability is improved. Figure 1 shows a TiO 2 -CaO -A1 2 O 3 phase diagram. The low melting point composition from this phase diagram is particularly due to TiO 2 : Al 2 O
The weight ratio of 3 : CaO is around 7: 1.5: 1.5. Further studies were conducted based on such a tendency. In the present invention, Al 2 O 3 : 10 to 30 wt%, Ca and / or metal REM oxide: 5 to 30 wt% (total Amount), Ti oxide: 50 to 90 wt%. If the composition is out of this range, the inclusions are in the liquid phase in the process before the tundish, but the temperature of the molten steel drops in the mold, so that the inclusions become solid and agglomerate rapidly, and large inclusions are removed. Will be generated. Thus, in the composition range according to the present invention, the generation of large inclusions is suppressed, and it is possible to suppress press cracking.
【００２６】本発明で上記組成に定める介在物径を50μ
ｍ以下としたのは、おおよそ50μｍを超える大きさの介
在物はスラグやモールドフラックスの混入に起因するも
のが含まれるので、脱酸生成物の組成を定めるには、50
μｍを超える大きさの介在物は組成の対象から外さねば
ならないからである。なお、本発明における鋼板中の介
在物の大きさとは、鋼板幅方向（圧延直角方向）の大き
さを意味する。というのは、スラブ中に存在する介在物
の寸法は、圧延により、圧延方向には伸長するものの、
板幅方向にはほとんど変化しない。従って、鋼板幅方向
の介在物寸法が上記範囲内のものは、スラブ段階でもこ
の寸法範囲にある微細なものと考えることができる。ま
た、本発明でいう粒状または破断状の酸化物系介在物と
は、鋼スラブで生成した酸化物系介在物が比較的小さな
ものでは、その形を維持しているような粒状のもの、ま
た比較的大きなものでは熱延および冷延により圧延方向
に分断された破断状のものをそれぞれ意味する。In the present invention, the inclusion diameter defined in the above composition is 50 μm.
m or less, since inclusions having a size exceeding approximately 50 μm include those resulting from the incorporation of slag and mold flux, to determine the composition of the deoxidation product,
This is because inclusions having a size exceeding μm must be excluded from the composition. The size of the inclusions in the steel sheet in the present invention means the size in the width direction of the steel sheet (the direction perpendicular to the rolling direction). Because the size of the inclusions present in the slab is elongated in the rolling direction by rolling,
It hardly changes in the width direction. Therefore, those having the inclusion size in the width direction of the steel sheet within the above range can be considered to be fine within this size range even at the slab stage. Further, the granular or fractured oxide-based inclusions referred to in the present invention are, when the oxide-based inclusions generated by the steel slab are relatively small, granular ones that maintain their shape, A relatively large one means a fractured one which is divided in the rolling direction by hot rolling and cold rolling.
【００２７】(3) 製造方法 本発明鋼板は、出鋼後の溶鋼をAlおよびTiにより脱酸し
たのちCaおよび／またはＲＥＭを添加する工程により溶
製する。このとき、Al添加前の酸素量と、Alを添加して
からTiを添加するまでの時間（すなわち、Al単独脱酸時
間）との間に、ａO ／ｔ≦１００（ただし、ａO ：Al添
加前の酸素の量（ｐｐｍ）、ｔ：Alを添加してからTiを
添加するまでの時間（ｍｉｎ））の関係が成り立つよう
にして添加する必要がある。溶鋼（通常は、ＲＨ脱ガス
設備にて脱炭処理後の溶鋼）中に、Alを添加すると、そ
の直後に Al2Ｏ3 クラスターが生成する。図２に、各脱
酸剤添加後の介在物の写真を示す。この Al2Ｏ3 クラス
ターは大型化しやすく、大きいものでは１ｍｍ以上にな
る。 Al2Ｏ3 クラスターの大きさと径は、Al添加前の溶
解酸素量ａOでほぼ決まり、ａO が大きいとクラスター
の量、径とも大きくなる。そして、この Al2Ｏ3 クラス
ターは、Ti添加後のTi2O3 、さらにCa添加後のTi−Al−
Ca(REM) 系の球状介在物の組成や粒径に影響を及ぼす。
Ti添加前のAl2 Ｏ3 量が多いと、最終の介在物の Al2Ｏ
3 濃度が高くなり、かつ、介在物が凝集しやすくなって
粗大化することがわかった。また、Alを添加してからTi
を添加するまでの時間は、Ti添加時に残留する大型のAl
2O3 クラスターを通じて、最終的に製品の大型介在物量
に影響を及ぼす。(3) Production Method The steel sheet of the present invention is produced by deoxidizing molten steel after tapping with Al and Ti and then adding Ca and / or REM. At this time, between the amount of oxygen before the addition of Al and the time from the addition of Al to the addition of Ti (that is, the deoxidation time of Al alone), a O / t ≦ 100 (where a O : It is necessary to add oxygen in such a way that the relationship between the amount of oxygen (ppm) before Al addition and the time (t: the time from the addition of Al to the addition of Ti (min)) is satisfied. When Al is added to molten steel (usually, molten steel after decarburization treatment by RH degassing equipment), Al 2 O 3 clusters are generated immediately thereafter. FIG. 2 shows a photograph of the inclusion after addition of each deoxidizing agent. The Al 2 O 3 cluster is likely to be large, and if it is large, it will be 1 mm or more. The size and diameter of the Al 2 O 3 clusters, substantially determined by dissolving oxygen a O before Al addition, as large as a O large amount of clusters, both diameter. This Al 2 O 3 cluster is composed of Ti 2 O 3 after Ti addition and Ti-Al-
Affects the composition and particle size of Ca (REM) -based spherical inclusions.
If the amount of Al 2 O 3 before adding Ti is large, the final inclusion Al 2 O 3
3 It was found that the concentration was increased, and the inclusions were easily aggregated and coarsened. Also, after adding Al, Ti
Time until the addition of Ti
Through the 2 O 3 cluster, it ultimately affects the amount of large inclusions in the product.
【００２８】これらの事実をベースにして導いたパラメ
ータａO ／ｔの値を１００以下にすると、介在物の組成
が、Al2O3 ：10〜30wt％、Caおよび／または金属ＲＥＭ
の酸化物：5 〜30wt％、Ti酸化物：50〜90wt％となり低
融点化が達成できる。その結果、タンディッシュや浸漬
ノズル内に、酸化物等の付着防止のためのArやN2等のガ
スを吹き込む必要がなくなり、吹き込みガスによる気泡
性の欠陥も防止できる。しかも、このスラブをさらに、
熱延、冷延、焼鈍することにより、表面性状と内質に優
れた冷延鋼板を製造することが可能となる。なお、本発
明において、ＲＥＭ酸化物（例えば、La2O3 ，CeO2）
は、CaＯと同じ役割を果たすことを確認した。また、二
次精錬設備で，ＲＨ脱ガス以外の処理、例えば、ＶＯＤ
などを使用した場合でも、介在物組成を本発明の範囲に
制御できれば同様の効果が得られるのは言うまでもな
い。If the value of the parameter a O / t derived on the basis of these facts is set to 100 or less, the composition of the inclusion becomes Al 2 O 3 : 10 to 30 wt%, Ca and / or metal REM.
Oxide: 5 to 30% by weight, Ti oxide: 50 to 90% by weight, and a lower melting point can be achieved. As a result, it is not necessary to blow a gas such as Ar or N 2 into the tundish or the immersion nozzle to prevent the adhesion of oxides and the like, and it is possible to prevent the bubble defect due to the blown gas. Moreover, this slab is further
By hot rolling, cold rolling and annealing, it becomes possible to produce a cold rolled steel sheet having excellent surface properties and internal quality. In the present invention, REM oxide (for example, La 2 O 3 , CeO 2 )
Confirmed the same role as CaO. In the secondary refining equipment, processing other than RH degassing, for example, VOD
It is needless to say that the same effect can be obtained even when the composition is controlled within the range of the present invention.
【００２９】本発明鋼板を製造する際の他の条件とし
て、スラブの加熱は、圧延荷重および結晶粒径の点か
ら、900 〜1300℃の温度で行うのが望ましく、熱間圧延
の終了温度も同様な理由で、650 〜960 ℃の範囲とする
のが好ましい。また、冷間圧延における冷延圧下率は加
工性確保の上から50〜95％とすることが、冷延後の再結
晶焼鈍の温度は 700〜920 ℃とすることが望ましい。As another condition for producing the steel sheet of the present invention, the slab is desirably heated at a temperature of 900 to 1300 ° C. in view of the rolling load and the crystal grain size. For the same reason, the temperature is preferably in the range of 650 to 960 ° C. It is desirable that the rolling reduction in cold rolling in cold rolling be 50 to 95% from the viewpoint of ensuring workability, and the temperature of recrystallization annealing after cold rolling be 700 to 920 ° C.
【００３０】[0030]
【実施例】出鋼後リムド処理した溶鋼に、ＲＨ処理設備
にて、Alを添加し、次いでTiを添加した。その後、Ca
（一部のものについてはＲＥＭ）をワイヤーで添加し、
連続鋳造によりスラブとした。このスラブを熱延（終了
温度：820 ℃）、冷延、連続焼鈍（焼鈍温度：800 ℃）
して、板厚0.75ｍｍの冷延板および亜鉛めっき板とし
た。以上の製造条件及び得られた冷延鋼板の各特性の調
査結果を表１及び表２にまとめて示す。なお、上記製造
工程において、Al添加前の溶解酸素量ａo は、濃淡電池
を利用した酸素プローブで測定した。また、鋼板の介在
物の組成は、ＥＰＭＡやＥＤＸなどの分析手法によっ
て、50μｍ径以下の介在物個々の組成を分析し、10個の
値の平均値から求めた。さらに、冷延鋼板（冷延板およ
び亜鉛めっき板）の表面性状は、鋼板の目視検査によ
り、またプレス割れは、各10枚のサンプルについてバル
ジ試験を行い、介在物によるネッキング個数を一定重量
当たりの個数として指数化した。表１、２から、ａo ／
ｔを１００（ｐｐｍ／ｍｉｎ）以下にして、介在物の組
成を調整した発明例は、表面性状、耐プレス割れ性とも
に大幅に向上することがわかる。なお、連続鋳造工程に
おけるイマージョンノズルの閉塞は本発明では生じなか
ったが、一方、鋼中のAl濃度が0.01％以上の場合 (Alキ
ルド鋼) には、浸漬ノズルからのAr吹きを行わないとノ
ズル閉塞を起こして鋳造不能となった。EXAMPLE Al was added to molten steel that had been rimmed after tapping in a RH treatment facility, and then Ti was added. Then, Ca
(REM for some) with a wire,
A slab was formed by continuous casting. This slab is hot rolled (finish temperature: 820 ° C), cold rolled, and continuously annealed (annealing temperature: 800 ° C)
Thus, a cold-rolled sheet and a galvanized sheet having a sheet thickness of 0.75 mm were obtained. Tables 1 and 2 collectively show the above production conditions and the results of the investigation on the properties of the obtained cold-rolled steel sheets. In the above manufacturing process, Al added before lysis oxygen a o was measured with an oxygen probe utilizing concentration cell. The composition of the inclusions in the steel sheet was determined by analyzing the composition of each inclusion having a diameter of 50 μm or less by an analysis method such as EPMA or EDX, and determining the average value of 10 values. In addition, the surface properties of cold-rolled steel sheets (cold-rolled sheets and galvanized sheets) were checked by visual inspection of the steel sheets. The number was converted to an index. From Tables 1 and 2, ao /
It can be seen that the invention example in which the composition of the inclusion was adjusted by setting t to 100 (ppm / min) or less significantly improved both the surface properties and the press crack resistance. In the present invention, the clogging of the immersion nozzle in the continuous casting process did not occur, but when the Al concentration in the steel was 0.01% or more (Al-killed steel), Ar blowing from the immersion nozzle was not performed. Nozzle clogging occurred and casting became impossible.
【００３１】[0031]
【表１】 [Table 1]
【００３２】[0032]
【表２】 [Table 2]
【００３３】[0033]
【発明の効果】以上説明したように、本発明によれば、
連続鋳造時にArやN2等のガスを吹き込まずともイマージ
ョンノズルの閉塞を引き起こすことがなく、しかも冷延
鋼板の表面は非金属介在物に起因する表面欠陥がなく、
内部での粗大な介在物もないのでプレス割れも回避で
き、優れたプレス性が得られる。As described above, according to the present invention,
Without infused with Ar and N 2 or the like of gas during continuous casting without causing clogging of the immersion nozzle, moreover the surface of the cold-rolled steel sheet has no surface defects caused by nonmetallic inclusions,
Since there are no coarse inclusions inside, press cracking can be avoided and excellent pressability can be obtained.
【図１】Ti−Ca−Al−Ｏ系の状態図である。FIG. 1 is a phase diagram of a Ti—Ca—Al—O system.
【図２】酸化物系介在物の形状変化を示す図である。FIG. 2 is a view showing a shape change of an oxide-based inclusion.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 反町 健一 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 (72)発明者 鍋島 誠司 岡山県倉敷市水島川崎通１丁目（番地な し） 川崎製鉄株式会社水島製鉄所内 Ｆターム(参考） 4K020 AA22 AC07 AC09 BB22 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenichi Sorimachi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Seiji Nabeshima 1-chome Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture None) Kawasaki Steel Corporation Mizushima Works F term (reference) 4K020 AA22 AC07 AC09 BB22
Claims (2)
0 wt％、Ｐ≦0.15wt％、Ｓ≦0.05wt％、Al＜0.01wt％、
Ｎ≦0.01wt％、0.015 wt％≦Ti≦0.1 wt％、Caおよび／
または金属ＲＥＭ≧0.0005wt％を含み、残部はFeおよび
不可避的不純物よりなる成分組成であり、50μｍ以下の
大きさを有する、粒状または破断状の酸化物系介在物の
組成が Al2Ｏ3 ：10〜30wt％、Caおよび／または金属Ｒ
ＥＭの酸化物： 5〜30wt％、Ti酸化物：50〜90wt％であ
ることを特徴とする、表面性状および内質に優れる冷延
鋼板。1. C ≦ 0.010 wt%, Si ≦ 1.0 wt%, Mn ≦ 3.
0 wt%, P ≦ 0.15 wt%, S ≦ 0.05 wt%, Al <0.01 wt%,
N ≦ 0.01 wt%, 0.015 wt% ≦ Ti ≦ 0.1 wt%, Ca and / or
Or, the composition of the oxide-based inclusions containing metal REM ≧ 0.0005 wt%, the balance being Fe and unavoidable impurities, and having a size of 50 μm or less, and having a granular or fractured form of Al 2 O 3 : 10-30 wt%, Ca and / or metal R
A cold rolled steel sheet having excellent surface properties and internal quality, characterized in that EM oxide: 5 to 30 wt% and Ti oxide: 50 to 90 wt%.
たのちCaおよび／またはＲＥＭを添加する工程を経て、
Ｃ≦0.010 wt％、Si≦1.0 wt％、Mn≦3.0 wt％、Ｐ≦0.
15wt％、Ｓ≦0.05wt％、Al＜0.01wt％、Ｎ≦0.01wt％、
0.015 wt％≦Ti≦0.1 wt％、Caおよび／または金属ＲＥ
Ｍ≧0.0005wt％を含み、残部はFeおよび不可避的不純物
よりなる冷延鋼板を製造するに当たり、 Al添加前の酸素の量と、Alを添加してからTiを添加する
までの時間との間に、 ａO ／ｔ≦１００ ただし、ａO ：Al添加前の酸素の量（ｐｐｍ）、ｔ：Al
を添加してからTiを添加するまでの時間（ｍｉｎ）の関
係が成り立つように添加することを特徴とする、表面性
状および内質に優れる冷延鋼板の製造方法。2. A process in which molten steel after tapping is deoxidized with Al and Ti and then Ca and / or REM is added.
C ≦ 0.010 wt%, Si ≦ 1.0 wt%, Mn ≦ 3.0 wt%, P ≦ 0.
15wt%, S ≦ 0.05wt%, Al <0.01wt%, N ≦ 0.01wt%,
0.015 wt% ≦ Ti ≦ 0.1 wt%, Ca and / or metal RE
In producing a cold-rolled steel sheet containing M ≧ 0.0005 wt%, with the balance being Fe and unavoidable impurities, between the amount of oxygen before adding Al and the time from adding Al to adding Ti. to, a O / t ≦ 100, however, a O: the amount of Al added before oxygen (ppm), t: Al
A method for producing a cold-rolled steel sheet having excellent surface properties and internal quality, characterized in that a time (min) from the addition of Ti to the addition of Ti is established.
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| JP19655299A JP3870614B2 (en) | 1999-07-09 | 1999-07-09 | Cold-rolled steel sheet having excellent surface properties and internal quality and method for producing the same |
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