JP3739933B2 - Steel sheet for surface treatment with good workability and few defects and method for producing the same - Google Patents

Steel sheet for surface treatment with good workability and few defects and method for producing the same Download PDF

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JP3739933B2
JP3739933B2 JP08376898A JP8376898A JP3739933B2 JP 3739933 B2 JP3739933 B2 JP 3739933B2 JP 08376898 A JP08376898 A JP 08376898A JP 8376898 A JP8376898 A JP 8376898A JP 3739933 B2 JP3739933 B2 JP 3739933B2
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steel
alumina
inclusions
titanium oxide
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JPH11279721A (en
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寿雅 友清
一正 山崎
利明 溝口
竜司 岡本
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Nippon Steel Corp
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Nippon Steel Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、加工性が良好で欠陥が少ない、ぶりきやティンフリースチール等の表面処理用鋼板およびその製造方法に関する。
【0002】
【従来の技術】
ぶりき原板の調質度は、JIS(G3303)に規定されるように、ロックウェル硬さに応じて軟質のものから調質度T1として、T6までの6種に分類される。一般に調質度がT1〜T3の軟質ぶりきは焼鈍工程において箱型焼鈍法で、調質度がT4〜T6までの硬質ぶりきは連続焼鈍法で製造されている。しかし、箱型焼鈍法では生産性や材質ばらつき等の問題があり、軟質ぶりきの製造も連続焼鈍法で行うことが望まれていた。連続焼鈍法による軟質ぶりきの製造に関しては、特開昭58−197224号公報や特開平4−228526号公報がある。これらの技術はいずれも極低炭素鋼を用い、さらに結晶粒の微細化や面内異方性を改善するために、所定量のNbを添加した鋼板あるいはその製造方法に関するものである。これらの技術の提案により、連続焼鈍法において軟質でかつ加工性の良好なブリキ原板の製造が可能となった。
【0003】
しかしながら、成形性の改善を目的としたNbの多量添加は鋼板の耐食性劣化や再結晶温度の上昇を招き、連続焼鈍工程での鋼板の軟化による通板不良等の原因となり、材質特性と安定製造に関して課題も残っている。
【0004】
また、ぶりき、ティンフリースチール等の表面処理鋼板は、通常、深絞り加工、しごき加工、曲げ加工、ストレッチ加工等を施して容器として使用される。これらの鋼板は、転炉で溶製された未脱酸の溶鋼をAlで脱酸を行うAlキルド鋼で製造されている。このようなAl脱酸鋼では、脱酸時に添加したAlと溶鋼中の酸素が反応したり、脱酸後に鋼中に残留したAlがスラグや空気中等の酸素によって酸化してアルミナが生じる。このアルミナは硬質であるため圧延や加工等で破砕されずに鋼板に塊状で残存し、加工時に割れや疵等の欠陥発生の原因となる。そこでこれらのアルミナに対して、▲1▼スラグ中や雰囲気中の酸素の制御による溶鋼中のAlの酸化によるアルミナの生成防止や、▲2▼溶鋼中へのガスやフラックスの吹き込みによる溶鋼中のアルミナの浮上促進による低減と、▲3▼溶鋼中へのCaの添加によってアルミナを圧延・加工時に破砕されやすいカルシウムアルミネートに形態制御する無害化が行われてきた。
【0005】
しかし、Alで脱酸を行っている限りはアルミナの生成は皆無にはできず、除去も不十分である。そして、Ca添加による方法もCaは高価であるとともに歩留まりが極めて悪いために合金コストが高くなる。また介在物にアルミナを含有するため冷却時に介在物中に固いアルミナが部分的に晶出し、圧延等によっても破砕されずに残存し欠陥が発生する。さらに、Caを添加して生成するカルシウムアルミネートは肥大化しやすく、このような介在物が浮上しきれず残留した場合には欠陥となる。これらの問題を解決するためにはAl以外の元素で脱酸することが考えられ、特公昭48−29005に見られるようにAlもSiも全く添加せずにTiのみで脱酸する方法があるが、この場合Tiのみによる脱酸のためにTi添加前の溶鋼中酸素は非常に高い値となり、この様な溶鋼にTiを添加すると粒径の大きなチタン酸化物が多量に生成して溶鋼中に残存し、これはアルミナと同様に固く破砕されにくいため欠陥となる。
【0006】
このため、特公平2−9646に見られるように、Ti添加前にAlを添加して予備脱酸を行い、溶鋼酸素を低減した後にTiを添加する方法があるが、上記のごとき方法では溶鋼中の酸素が高い状態でAlを添加するために、多量のAlを添加する必要があり、その結果、多量のアルミナが生成してそのまま残留したり、アルミナを含有する複合介在物が生成して冷却時に介在物中の一部にアルミナが晶出し、この部分が圧延等によっても破砕されずに残存し欠陥が発生する。また、Alは脱酸力が強いので酸素のコントロールが不安定である。さらに、Tiを添加した際にTiと溶鋼中の酸素との反応によって生成したチタン酸化物の一部は複合介在物となるが、この複合酸化物はアルミナを含むために冷却時に介在物中に晶出するアルミナが破砕されずに残存し欠陥が発生する。一方、生成したチタン酸化物の大部分は粒径が大きくかつ、破砕されにくいチタン酸化物となって溶鋼中に存在し、その一部は浮上しきれずに残留して欠陥となる等の課題がある。このように通常の製造方法では、粒径が大きくかつ、硬質の介在物が含まれるのが一般的であり、この介在物は加工時に亀裂の起点となるため、この種の介在物が多量に含まれると、欠陥が多発するという問題を有していた。
【0007】
鋼中に酸可溶Alを多く含有する鋼は再結晶温度が高くなり、特に前述の極低炭素鋼にTi、Nb等の炭窒化物形成元素を添加した鋼では、微細な炭窒化物が鋼中に存在するので、一般の低炭素Alキルド鋼よりもさらに高い温度で焼鈍をしなければならなかった。これを解消する方法として、特開昭62−30822号公報のようにAlで脱酸を行うものの、脱酸に使われた以外の余剰Alすなわち酸可溶Alを0.010%以下に制限する技術がある。この技術もAlで脱酸しているのでAlの酸化物が鋼中に残存するのは必然で、これらの鋼においてもAlの酸化物のよる欠陥の発生は抑え得ないものであった。さらに、酸可溶Alが残存しないように脱酸すると脱酸不足が生じ、鋼中に気泡が残ることがしばしば起き、ブローホールと呼ばれる欠陥により表面性状を損ね、安定化ができる技術ではなかった。
【0008】
【発明が解決しようとする課題】
本発明はこのような課題を解決するためになされたものであり、鋼中の介在物を微細で、かつ、部分的に固い晶出相がなく、介在物全体が変形・破砕しやすい組成の介在物にコントロールし、低コストで介在物欠陥を少なくし、さらに、鋼中のAlの含有量を極めて少なくできるので再結晶温度を低くでき、このため、Nb、Ti等の炭窒化物形成元素を添加した極低炭素鋼を用いても連続焼鈍工程での通板不良等を解決し、安定的な製造が可能となる鋼板およびその製造方法を提供するものである。
【0009】
【課題を解決するための手段】
本発明の特徴とするところは、
(1)重量%で、
C :0.0002〜0.0080%、
Si:0.001 〜0.04%、
Mn:0.05〜1.0 %、
P :0.001 〜0.050 %、
S :0.001 〜0.030 %、
Sol.Al:0.001 〜0.005 %、
N :0.0005〜0.0080%、
Ti:0.004 〜0.030 %、
を含有し、残部がFe及び不可避的不純物からなる鋼において、最大粒径が150μm 以下で鋼中の介在物をチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナが主成分でチタン酸化物が5〜30%、アルミナが2〜15%でかつチタン酸化物とアルミナの和が40%以下である酸化物系介在物を含有せしめたことを特徴とする加工性が良好で欠陥の少ない表面処理用鋼板、
(2)前記1記載の成分に加えてさらに、
Nb:0.002 〜0.05%
を含有し、残部がFe及び不可避的不純物からなる鋼において、最大粒径が150μm 以下で鋼中の介在物をチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナが主成分でチタン酸化物が5〜30%、アルミナが2〜15%でかつチタン酸化物とアルミナの和が40%以下である酸化物系介在物を含有せしめたことを特徴とする加工性が良好で欠陥の少ない表面処理用鋼板、
(3)精錬後の溶鋼の鋼中酸素量を250ppm以下に脱酸し、ついでTiを添加し、その後Alを添加して前記1または2記載の成分の鋼とし、この鋼を連続鋳造−熱間圧延の後、600 〜800 ℃で巻取って、ついで脱スケール処理、冷間圧延後、650 〜750 ℃で連続焼鈍を施し、調質圧延あるいは2次冷間圧延の後、めっき工程を経て表面処理鋼板とする加工性が良好で欠陥が少ない表面処理用鋼板の製造方法、
(4)Alを添加する際に、化学組成がAl:10〜80重量%、残りFe、Mn、Siの1種〜3種及び不可避的不純物からなる合金を添加して行うことを特徴とする前記3に記載の加工性が良好で欠陥が少ない表面処理用鋼板の製造方法、
にある。
【0010】
【発明の実施の形態】
本発明者らは、種々の組成の介在物を人工的に合成して鋼中に埋め込み,実験室的に圧延実験を行った。その結果、介在物中にアルミナを少量含有しチタン酸化物(TiOX 、X=1.5 〜2.0)、マンガン酸化物(MnO) 、シリコン酸化物(SiO2)アルミナ(Al2O3)を主成分とする組成の介在物とすれば、融点が比較的低く、冷却時に高融点で固い晶出相が生成せず、圧延等によって微細に破砕されることを知見した。
【0011】
このようなアルミナ含有量および組成の異なる介在物を分散させた鋼を実験室的に溶製、鋳造し、通常の方法で熱間圧延、酸洗、冷間圧延、焼鈍、調質圧延、めっきを行って鋼板とし、絞り成形を行ったが一部の鋼板で割れ等の欠陥が発生した。この欠陥の部分の調査を行った結果、欠陥部には伸延した介在物が検出された。介在物サイズを測定した結果、その大きさは鋳片での大きさに換算するといずれも平均粒径50μm より大きかったことが判った。欠陥が発生しなかった部分を切断し鋼中の介在物の大きさを測定すると、これには平均粒径150μm 以下の介在物が検出された。平均粒径が50〜150μm で欠陥が発生しなかった部分の介在物の組成を調査すると、チタン酸化物(TiOX 、X=1.5 〜2.0)とアルミナ(Al2O3)との和が40%以下の介在物組成であった。介在物の組成がチタン酸化物(TiOX 、X=1.5 〜2.0)とアルミナ(Al2O3)との和が40%超で、平均粒径が50〜150μm になると、硬質の介在物で比較的粒径が大きいため、圧延等による圧下で伸展・変形を受けても、破砕されずに連続したまま残ったり、破砕されてもその粒が大きく連続して存在するために加工時に欠陥となると考えられる。さらに、詳細な調査をしたところ、介在物の平均粒径が150μm 以下で、チタン酸化物(TiOX 、X=1.5 〜2.0)とアルミナ(Al2O3)との和が40%以下でも、チタン酸化物(TiOX 、X=1.5 〜2.0)とアルミナ(Al2O3)がそれぞれ、30%超と15%超では欠陥が発生することが判明した。
【0012】
以上のことより、平均粒径が150μm 以下で、組成がチタン酸化物(TiOX 、X=1.5 〜2.0)とアルミナ(Al2O3)がそれぞれ30%以下と15%以下でかつ両者の和が40%以下であれば欠陥とならないことが推測されたため、150μm 以下のチタン酸化物(TiOX 、X=1.5 〜2.0)が5〜30%とアルミナ(Al2O3) が2〜15%で両者の和が40%以下含有したチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナを主成分とする組成の介在物のみを分散させた鋼を実験室的に溶製、鋳造し、通常の方法で熱間圧延、酸洗、冷間圧延、焼鈍、2次冷間圧延、めっきを行って、絞り成形を行ったところ欠陥の発生がないことが確認できた。
【0013】
さらに添加するTi濃度を変化させて実験を行った結果、チタン酸化物、マンガン酸化物、シリコン酸化物、アルミナを主成分とする組成の介在物とするには、Ti濃度を0.030 %以下にすることが必要である。これはTiが高すぎるとTiの脱酸力がMnやSiに比べて高いのでこれらの酸化物と複合せず、アルミナと同様な高融点のチタン酸化物含有量の高い介在物が生成するためである。一方、Tiの下限を0.004 %としたのは、連続鋳造時に脱酸不足による気泡の発生を防止するためであり、Ti量は脱酸に使用された残りを用いて、C、Nを析出固定するので、好ましくはこのC、Nの析出固定に必要な量に脱酸に必要な量に0.004 %を加えた量以上とする。C、Nを析出固定するために必要なTiはNbの添加量によって異なり、詳細は後述する。
【0014】
Tiを添加した後にAlを添加することで、Al添加時の酸素濃度が下がっており、Alの添加量が少なくてすみ、生成する介在物中のアルミナ含有量も少なく、介在物中にアルミナが含有していても加工時の欠陥発生はほとんどない。また、Ti添加時に生成したチタン酸化物、マンガン酸化物、シリコン酸化物を主成分とする組成の介在物はAlによって還元されてしまわずにチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナを主成分とする組成の介在物となる。これらの介在物はアルミナ単体に比べると溶鋼中で浮上しやすく、清浄性も向上する。総Al量が0.001%以上あれば酸素は20ppm以下とすることができ、COガスは発生せずに鋳造が可能となり、COガス起因の気孔が鋼材中に生成するのを抑止することができる。
【0015】
まず、転炉で目標とする0.0002〜0.0080%のCを含む溶鋼を溶製する。この際、溶鋼中のCが目標とするC濃度より高い場合には出鋼後に真空脱ガス装置等による脱炭処理を行い所定のC濃度まで低減し、目標とするC濃度より低い場合には出鋼後にCを添加して所定のC濃度とする。
【0016】
次に、出鋼した溶鋼をMn、Siの1種または2種を添加するか、真空脱ガス処理による予備脱酸を行って溶鋼中の酸素を250ppm以下とする。単体のアルミナを生成さませないためにはTiを添加させる前にAlを添加しないことが必要であり、Fe−MnやFe−Siを添加してMn、Siにより脱酸を行う。Mn、Siの添加量は脱酸時に添加するTi合金中に含まれるMnやSiによって増加する量を考慮して添加する。また、MnやSiは脱酸力が弱いので製品によっては目標範囲内では溶鋼中の酸素を300ppm以下にすることが困難な場合があるので、その際には真空脱ガス処理により真空脱酸を行い酸素を下げる。溶鋼中の酸素が250ppmより高くなると、Ti合金を多量に添加することが必要になり、後述するように脱酸時の過飽和度が大きくなり、Ti添加時にアルミナと同様の高融点のチタン酸化物が多数生成し、複合介在物が安定して生成しない。また、これらが凝集して大きな介在物となる。このようにして溶鋼中の酸素を250ppm以下に調整した溶鋼に、化学組成がTi:10〜70重量%の成分と残部はFe、Mn、Siのうち1種から3種および不可避的不純物とからなる合金を添加して、Tiを溶鋼成分として0.004 〜0.030 %含有させる。溶鋼中のTi濃度を0.030 %以下とすることでチタン酸化物、マンガン酸化物、シリカを主成分とする組成の複合介在物とすることが可能となる。溶鋼中のTi濃度が高すぎるとTiの脱酸力がMnやSiに比べて高いのでこれらの酸化物と複合せず、アルミナと同様な高融点のチタン酸化物が主成分の介在物となる。
【0017】
更に、脱酸時の過飽和度を小さくすれば核生成速度が遅くなり、生成する介在物の個数及び介在物径が小さくなる。過飽和度はTiと酸素の積で決まるので、過飽和度を小さくする方法として脱酸合金中のTi含有量を低くすることと脱酸時の溶鋼中の酸素を低くすることが有効である。脱酸合金中のTi含有量が高い場合には溶鋼中に添加した脱酸合金の周囲にTi濃度の高い部分が生成して過飽和度が高くなるので、Ti含有量の低い脱酸合金を使用する。酸素濃度および合金中Ti含有量が低くなるにしたがって介在物径は小さくなり、酸素を250ppm以下とし、かつ、Ti含有量が70%以下の合金で脱酸することで、平均粒径150μm 以下の介在物となる。Ti含有量が高くなると介在物径が大きくなるとともに、脱酸時にチタン酸化物の割合の高い介在物が生成し、それが溶鋼中に残存し混在する。Ti濃度が低すぎると脱酸合金の投入量が多くなりすぎ、溶鋼温度の低下が起こって溶鋼の凝固や鋳造が困難になったり、添加に時間がかかり生産性に障害を与える。また、Ti含有量が高い場合には少量ずつ添加すると部分的に過飽和度の高い部分が少なくなり有効である。
【0018】
また、TiをFeやSi、Mnとの合金とすることで、Tiの活量を下げるとともに部分的に濃度の高い領域を減少させるために、過飽和度が一層減少し、チタン酸化物、マンガン酸化物、シリコン酸化物の複合介在物の生成を促進する。
【0019】
Tiは1度に添加してもよいが、2回以上に分割して添加してもよい。Tiは添加後に溶鋼中の酸素が高く鋳造時COガスが発生して鋳型内溶鋼のボイリングが発生するおそれのある場合には、Ti添加後にAlを0.001%以上なる量添加してもよい。これによって酸素は20ppm以下になり、COガス発生によるボイリングなしに鋳造が可能となる。Tiの添加による脱酸によって酸素が下げられているので、Ti添加前にAlを添加する場合よりもAlの添加量は少なくて済み、生成する介在物の量が少なく、粗大な介在物も生成しない。Alを0.005 %以下とすることで介在物はチタン酸化物、シリコン酸化物、マンガン酸化物、およびアルミナが主成分でチタン酸化物が5〜30%、アルミナが2〜15%でチタン酸化物とアルミナの和が40%以下の溶鋼中で液体状態として存在する介在物となる。
このようにして溶製した溶鋼は通常と同じ方法でタンディッシュを通して、連続鋳造機で鋳造することが可能である。
【0020】
最終的に鋼中に含有されるMnの含有量は、0.05%未満に下げるためには精錬時間が長くなって経済性を大きく損ねるので、0.05%を下限とし、1.0%を越えると鋼板の加工性が大きく劣化し製品形状によっては加工ができなくなるので、1.0%を上限とする。
Si量は、0.001 %未満に下げるのは十分な予備処理等が必要で精錬に大幅なコスト負担をかけ経済性を損ねるので0.001 %を下限とし、0.04%を越えるとめっきの際にめっき不良が発生し、表面性状、耐食性を損ねるとともに材質を硬質化させるため、軟質の鋼板を得ることができなくなるため0.04%を上限とする。
Pは、0.001 %未満に下げることは溶銑予備処理に時間とコストがかかり、経済性を大きく損ねるので、0.001 %を下限とし、0.050 %を越えると加工性が劣化し、加工に支障をきたすので0.050 %を上限とする。
Sは、0.001%未満に下げることは溶銑予備処理に時間とコストがかかり、経済性を大きく損ねるので、0.001 %を下限とし、0.030 %を越えると加工性・耐食性が劣化し、缶としての加工・性能に支障をきたすので0.030 %を上限とする。
Nは、0.0005%未満に下げることは精錬の段階での大幅なコスト上昇を伴い経済性を大きく損ねるので、0.0005%を下限とし、0.0080%を越えると、固溶NをなくすためのTi添加量が多く必要で、本願の目的である介在物の形態制御が不可能になるので、0.0080%を上限とする。
【0021】
固溶N量を少なくするために、NをTiNとして固定するには、前述のように少なくともTi(%)>3.43×N(%)とする必要がある。さらに、加工性を向上させるためには、TiはCとの当量以上添加することが好ましい。この場合のTiの添加量は、Ti(%)>4×C(%)+3.43×N(%)となる。
Tiの上限は、0.030%とする。この量を越えると、脱酸時にTiを大量に加えなければならなくなり、本願発明の特徴とする介在物組成が得られなくなるためである。
【0022】
Nbは、加工性向上を目的として、主としてCを析出固定するために添加する。添加量としては、好ましくは、Tiを添加しない場合は、Nb(%)>6.64×N(%)、Tiを添加してNを析出固定した場合は、Nb(%)>0.8×7.75×C(%)を添加する。添加量の下限としては、0.002 %未満では、加工性を向上させる効果がなくなるので、0.002 %を下限とし、0.050 %を越えると、固溶Nbの存在によってかえって加工性を劣化させることになるので、0.050 %を上限とする。
【0023】
このようにして溶製した溶鋼を通常と同じ方法でタンディッシュを通して、連続鋳造機で鋳造する。さらに、適宜、熱間圧延に先立って加熱を施し、この鋳片を通常と同じ方法で熱間圧延した後、600 ℃〜800 ℃の温度範囲で巻取りを行う。巻取温度600 ℃未満では、Ti及びNbによる固溶N及び固溶Cの析出固定が不十分で時効性が劣化するので600 ℃を下限とし、800 ℃を越えると粗大粒となり加工後肌荒れを起こして外観を損ねるので800 ℃を上限とする。ついで、脱スケール処理を行う。一般には酸洗を施すが、機械的にスケール除去を行っても良い。その後、冷間圧延を行い、連続焼鈍を行う。連続焼鈍の温度は、650 ℃〜750 ℃とする。650 ℃未満では再結晶が完全ではなく加工性が劣化するので650 ℃を下限とし、750 ℃を越えると鋼板の高温強度が弱まり、連続焼鈍炉内で絞りと呼ばれる現象を起こし,破断するなどの問題が生じやすくなるので750 ℃を上限とする。その後、スキンパス圧延あるいは5〜40%程度のDR圧延を施し、クロムめっきあるいは錫めっきなどのめっきを施し、表面処理鋼板とする。例えば、クロムめっき及び又は錫めっき層があれば、地鉄との界面にNi等の極薄層があってもかまわないし、錫めっきが錫−鉄合金めっきであってもかまわない。また、表面に樹脂フィルムを貼り付けたラミネート鋼板又は溶融した樹脂をすくなくとも片面に被覆せしめた樹脂積層鋼板も、本発明の表面処理鋼板から逸脱するものではない。
【0024】
【実施例】
270トン転炉で表1に示す合金組成の脱酸用合金を用いて、各成分の鋼を溶製し連続鋳造した。製造した鋼の成分を表1にまとめて示す。また介在物組成および介在物のサイズを表2に示す。ついで、熱間圧延を行った。そのときの巻取温度を表3に示した。次いで、酸洗、冷間圧延を行った後、表3に示す温度で焼鈍を実施した。焼鈍は、箱焼鈍あるは連続焼鈍で行った。表3には、再結晶温度も同時に示す。焼鈍後、スキンパス圧延あるいは2次冷間圧延を施した。表3にその圧下率を示す。ついで、クロムめっきまたは錫めっきを施し、さらに一部の鋼板については、表裏面にポリエチレンテレフタレート樹脂フィルムを張り付け表面処理鋼板とした。
【0025】
その鋳片の一部および表面処理鋼板の一部を採取し、断面を調査し、介在物の組成、大きさ、形状を調査した。その結果を表2に示す。介在物の組成は走査型電子顕微鏡でエネルギー分散分析装置によって測定した。本発明では鋳片内にはチタン酸化物、マンガン酸化物、シリコン酸化物、を主とする組成で、ほぼ球形の介在物が検出された。また、冷延鋼板ではこれらの介在物が破砕され微細分散されていた。
【0026】
得られた表面処理鋼板を3段絞りに成形した絞り缶と絞りとしごきを加えたDI缶を製造し、このときの割れが発生した欠陥率を調査した。この結果を表3に示す。表3から本願発明鋼では、比較鋼に比べて再結晶温度が低く、低い焼鈍温度でも絞り成形が可能であり、さらに欠陥率が少なくなっていることがわかる。
【0027】
【表1】
【0028】
【表2】
【0029】
【表3】
【0030】
【発明の効果】
本発明によって、加工性が良好で欠陥の発生が少ない表面処理用鋼板の製造が可能となった。
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel sheet for surface treatment such as tinplate or tin-free steel having good workability and few defects, and a method for producing the same.
[0002]
[Prior art]
As specified in JIS (G3303), the tempering degree of the tinplate sheet is classified into six types from soft one to tempering degree T1 up to T6 according to the Rockwell hardness. Generally, soft tin with a tempering degree of T1 to T3 is manufactured by a box-type annealing method in the annealing process, and hard tinting with a tempering degree of T4 to T6 is manufactured by a continuous annealing method. However, the box-type annealing method has problems such as productivity and material variations, and it has been desired to produce a soft tinplate by the continuous annealing method. Japanese Unexamined Patent Publication No. 58-197224 and Japanese Laid-Open Patent Publication No. 4-228526 are known for producing soft tinplate by the continuous annealing method. Each of these techniques relates to a steel sheet using a very low carbon steel, and further added with a predetermined amount of Nb in order to improve grain refinement and in-plane anisotropy, or a method for manufacturing the same. By proposing these technologies, it has become possible to produce a tin plate that is soft and has good workability in the continuous annealing method.
[0003]
However, the addition of a large amount of Nb for the purpose of improving formability leads to deterioration of the corrosion resistance of the steel sheet and an increase in the recrystallization temperature, which may cause poor sheeting due to the softening of the steel sheet in the continuous annealing process, resulting in material properties and stable production. There are still issues regarding
[0004]
Further, surface-treated steel sheets such as tinplate and tin-free steel are usually used as containers after being subjected to deep drawing, ironing, bending, stretching, and the like. These steel plates are made of Al killed steel, in which undeoxidized molten steel melted in a converter is deoxidized with Al. In such Al deoxidized steel, Al added during deoxidation reacts with oxygen in the molten steel, or Al remaining in the steel after deoxidation is oxidized by oxygen such as slag or air to produce alumina. Since this alumina is hard, it remains in a lump in the steel sheet without being crushed by rolling or processing, and causes defects such as cracks and wrinkles during processing. Therefore, for these aluminas, (1) prevention of alumina formation by oxidation of Al in the molten steel by controlling oxygen in the slag and atmosphere, and (2) in the molten steel by blowing gas and flux into the molten steel. Reduction by promoting the floating of alumina, and (3) detoxification to control the form of alumina into calcium aluminate that is easily crushed during rolling and processing by adding Ca to molten steel.
[0005]
However, as long as deoxidation is performed with Al, the production of alumina cannot be completely eliminated, and the removal is insufficient. The Ca addition method also increases the cost of the alloy because Ca is expensive and the yield is extremely poor. Further, since the inclusion contains alumina, the hard alumina partially crystallizes in the inclusion during cooling, and remains without being crushed even by rolling or the like, thereby generating defects. Furthermore, calcium aluminate produced by adding Ca tends to enlarge, and if such inclusions cannot be lifted up and remain, they become defects. In order to solve these problems, it is conceivable to deoxidize with an element other than Al. As shown in Japanese Patent Publication No. 48-29005, there is a method of deoxidizing only with Ti without adding any Al or Si. However, in this case, oxygen in the molten steel before Ti addition becomes very high due to deoxidation only by Ti, and when Ti is added to such molten steel, a large amount of titanium oxide having a large particle size is generated in the molten steel. This is a defect because it is hard and not crushed like alumina.
[0006]
For this reason, as seen in Japanese Patent Publication No. 2-9646, there is a method in which Al is added before Ti addition and preliminary deoxidation is performed, and Ti is added after reducing the molten steel oxygen. It is necessary to add a large amount of Al in order to add Al with a high oxygen content. As a result, a large amount of alumina is generated and remains as it is or a composite inclusion containing alumina is generated. During cooling, alumina crystallizes in a part of the inclusions, and this part remains without being crushed even by rolling or the like, resulting in a defect. Moreover, since Al has a strong deoxidizing power, the control of oxygen is unstable. Furthermore, a part of the titanium oxide produced by the reaction between Ti and oxygen in the molten steel when Ti is added becomes a composite inclusion, but since this composite oxide contains alumina, it is contained in the inclusion during cooling. The crystallized alumina remains without being crushed and a defect occurs. On the other hand, most of the produced titanium oxide has a large particle size and is difficult to be crushed and exists in the molten steel, and a part of the titanium oxide does not float and remains as a defect. is there. As described above, in the normal manufacturing method, it is general that the particle size is large and hard inclusions are included. Since these inclusions are the starting point of cracks during processing, a large amount of such inclusions are present. When included, there was a problem that defects frequently occur.
[0007]
Steel containing a large amount of acid-soluble Al in the steel has a high recrystallization temperature. In particular, in a steel obtained by adding a carbonitride-forming element such as Ti or Nb to the aforementioned ultra-low carbon steel, fine carbonitride is present. Since it exists in steel, it had to be annealed at a higher temperature than general low carbon Al killed steel. As a method for solving this, there is a technique of limiting excess Al other than that used for deoxidation, that is, acid-soluble Al to 0.010% or less, although deoxidation is performed with Al as disclosed in JP-A-62-28222. is there. Since this technique is also deoxidized with Al, it is inevitable that the oxide of Al remains in the steel, and even in these steels, generation of defects due to the oxide of Al cannot be suppressed. Furthermore, if deoxidation is performed so that acid-soluble Al does not remain, deoxidation is insufficient, and air bubbles often remain in the steel, which is not a technique that can stabilize the surface properties due to defects called blowholes and can be stabilized. .
[0008]
[Problems to be solved by the invention]
The present invention has been made in order to solve such problems, and the inclusions in the steel are fine and have a composition that is easy to deform and crush the entire inclusions without a partially hard crystallized phase. Control of inclusions, low inclusion defects at low cost, and further, the recrystallization temperature can be lowered because the content of Al in the steel can be extremely reduced. For this reason, carbonitride-forming elements such as Nb and Ti The present invention provides a steel plate and a method for producing the same, which solves a plate passing defect in a continuous annealing process even when using an ultra-low carbon steel to which is added, and enables stable production.
[0009]
[Means for Solving the Problems]
The feature of the present invention is that
(1) By weight%
C: 0.0002 to 0.0080%,
Si: 0.001 to 0.04%,
Mn: 0.05 to 1.0%,
P: 0.001 to 0.050%,
S: 0.001 to 0.030%,
Sol. Al: 0.001 to 0.005%,
N: 0.0005 to 0.0080%,
Ti: 0.004 to 0.030%,
In which the balance is Fe and inevitable impurities, the maximum particle size is 150 μm or less, and the inclusions in the steel are mainly composed of titanium oxide, manganese oxide, silicon oxide, alumina, and titanium oxide Surface treatment with good workability and few defects, characterized by containing oxide inclusions containing 5-30%, alumina 2-15% and the sum of titanium oxide and alumina 40% or less Steel plate,
(2) In addition to the above component 1,
Nb: 0.002 to 0.05%
In which the balance is Fe and inevitable impurities, the maximum particle size is 150 μm or less, and the inclusions in the steel are mainly composed of titanium oxide, manganese oxide, silicon oxide, alumina, and titanium oxide Surface treatment with good workability and few defects, characterized by containing oxide inclusions containing 5-30%, alumina 2-15% and the sum of titanium oxide and alumina 40% or less Steel plate,
(3) Deoxidizing the molten steel after refining to 250 ppm or less, then adding Ti, and then adding Al to obtain the steel of the above component 1 or 2, which is continuously cast-heat After cold rolling, it is wound at 600-800 ° C, then descaling, cold-rolled, and then subjected to continuous annealing at 650-750 ° C, and after temper rolling or secondary cold rolling, it undergoes a plating process A method for producing a steel sheet for surface treatment with good workability and few defects, which is a surface-treated steel sheet,
(4) When adding Al, the chemical composition is Al: 10 to 80% by weight, the remaining Fe, Mn, 1 to 3 types of Fe, Mn, Si, and an alloy composed of inevitable impurities is added. The method for producing a steel sheet for surface treatment having good workability and few defects as described in 3 above,
It is in.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The inventors artificially synthesized inclusions of various compositions and embedded them in steel, and conducted a rolling experiment in the laboratory. As a result, the inclusion contains a small amount of alumina, and the main components are titanium oxide (TiO x , X = 1.5 to 2.0), manganese oxide (MnO), silicon oxide (SiO 2 ) alumina (Al 2 O 3 ). It was found that the inclusions having the composition as described above have a relatively low melting point, do not produce a hard crystallization phase with a high melting point during cooling, and are finely crushed by rolling or the like.
[0011]
Such steel in which inclusions with different alumina contents and compositions are dispersed is melted and cast in a laboratory, and hot rolling, pickling, cold rolling, annealing, temper rolling, plating are performed in the usual way. The steel sheet was made into a steel sheet and drawn, but some of the steel sheets had defects such as cracks. As a result of investigating this defect portion, the inclusions that were distracted were detected in the defect portion. As a result of measuring the size of the inclusions, it was found that all the sizes were larger than the average particle size of 50 μm when converted into the size of the slab. When a portion where no defect occurred was cut and the size of inclusions in the steel was measured, inclusions having an average particle size of 150 μm or less were detected. When the composition of inclusions in the portion where the average particle diameter was 50 to 150 μm and no defect occurred was investigated, the sum of titanium oxide (TiO x , X = 1.5 to 2.0) and alumina (Al 2 O 3 ) was 40. % Of inclusion composition. When the composition of inclusions is more than 40% of the sum of titanium oxide (TiO x , X = 1.5 to 2.0) and alumina (Al 2 O 3 ) and the average particle size is 50 to 150 μm, Since the particle size is relatively large, even if it is stretched or deformed under rolling due to rolling, etc., it remains continuous without being crushed, or even if it is crushed, the particles are large and continuous. It is considered to be. Furthermore, when a detailed investigation was conducted, even when the average particle size of inclusions was 150 μm or less and the sum of titanium oxide (TiO x , X = 1.5 to 2.0) and alumina (Al 2 O 3 ) was 40% or less, It has been found that defects occur when titanium oxide (TiO x , X = 1.5 to 2.0) and alumina (Al 2 O 3 ) exceed 30% and 15%, respectively.
[0012]
From the above, the average particle size is 150 μm or less, the composition is titanium oxide (TiO x , X = 1.5 to 2.0) and alumina (Al 2 O 3 ) are 30% or less and 15% or less, respectively. Since it was estimated that no defects would occur if the content was 40% or less, titanium oxide (TiO x , X = 1.5 to 2.0) of 150 μm or less was 5 to 30% and alumina (Al 2 O 3 ) was 2 to 15%. In the laboratory, a steel in which only inclusions having a composition mainly composed of titanium oxide, manganese oxide, silicon oxide, and alumina containing 40% or less of the sum is dispersed and cast, When hot rolling, pickling, cold rolling, annealing, secondary cold rolling, and plating were performed by the above method, it was confirmed that no defects were generated.
[0013]
Furthermore, as a result of experiments conducted by changing the concentration of Ti to be added, in order to make inclusions whose composition is mainly composed of titanium oxide, manganese oxide, silicon oxide, and alumina, the Ti concentration should be 0.030% or less. It is necessary. This is because if Ti is too high, the deoxidizing power of Ti is higher than that of Mn and Si, so it does not combine with these oxides, and inclusions with a high melting point titanium oxide content similar to alumina are produced. It is. On the other hand, the lower limit of Ti is set to 0.004% in order to prevent the generation of bubbles due to insufficient deoxidation during continuous casting. The amount of Ti is precipitated and fixed using the remainder used for deoxidation. Therefore, the amount is preferably equal to or greater than the amount necessary for the precipitation fixation of C and N plus 0.004% to the amount necessary for deoxidation. Ti required to precipitate and fix C and N varies depending on the amount of Nb added, and details will be described later.
[0014]
By adding Al after adding Ti, the oxygen concentration at the time of Al addition is reduced, the amount of Al added is small, the content of alumina in the produced inclusions is small, and alumina is contained in the inclusions. Even if it is contained, there is almost no generation of defects during processing. In addition, inclusions composed mainly of titanium oxide, manganese oxide, and silicon oxide produced when Ti is added are not reduced by Al, and titanium oxide, manganese oxide, silicon oxide, and alumina are not reduced. It becomes an inclusion with a composition as a main component. These inclusions are more likely to float in molten steel compared to alumina alone, and the cleanliness is improved. If the total amount of Al is 0.001% or more, oxygen can be reduced to 20 ppm or less, it is possible to cast without generating CO gas, and it is possible to suppress the formation of pores due to CO gas in the steel material.
[0015]
First, molten steel containing 0.0002 to 0.0080% C targeted in the converter is melted. At this time, when C in the molten steel is higher than the target C concentration, decarburization is performed by a vacuum degassing apparatus or the like after the steel is discharged to reduce to a predetermined C concentration, and when C is lower than the target C concentration. C is added after steeling to obtain a predetermined C concentration.
[0016]
Next, one or two kinds of Mn and Si are added to the molten steel that has been produced, or preliminary deoxidation is performed by vacuum degassing treatment to reduce oxygen in the molten steel to 250 ppm or less. In order not to form a single alumina, it is necessary not to add Al before adding Ti, and Fe-Mn or Fe-Si is added and deoxidation is performed with Mn and Si. Mn and Si are added in consideration of the amount increased by Mn and Si contained in the Ti alloy added during deoxidation. In addition, since Mn and Si have weak deoxidation power, depending on the product, it may be difficult to reduce the oxygen in the molten steel to 300 ppm or less within the target range. Do oxygen. When the oxygen in the molten steel is higher than 250 ppm, it is necessary to add a large amount of Ti alloy. As described later, the degree of supersaturation at the time of deoxidation increases, and the titanium oxide having the same high melting point as alumina at the time of Ti addition. Are produced in large numbers, and complex inclusions are not stably produced. Moreover, these aggregate and become a large inclusion. In this way, the molten steel whose oxygen in the molten steel is adjusted to 250 ppm or less is composed of a component having a chemical composition of Ti: 10 to 70% by weight and the balance of one to three of Fe, Mn, and Si and unavoidable impurities. An alloy to be added is added to contain 0.004 to 0.030% of Ti as a molten steel component. By making the Ti concentration in the molten steel 0.030% or less, a composite inclusion having a composition mainly composed of titanium oxide, manganese oxide, and silica can be obtained. If the Ti concentration in the molten steel is too high, the deoxidizing power of Ti is higher than that of Mn and Si, so it will not be combined with these oxides, and the high melting point titanium oxide similar to alumina will be the main inclusion. .
[0017]
Furthermore, if the degree of supersaturation during deoxidation is reduced, the nucleation rate is reduced, and the number of inclusions and the inclusion diameter are reduced. Since the degree of supersaturation is determined by the product of Ti and oxygen, it is effective to reduce the Ti content in the deoxidized alloy and to reduce the oxygen in the molten steel during deoxidation as a method for reducing the degree of supersaturation. When the Ti content in the deoxidized alloy is high, a portion with a high Ti concentration is generated around the deoxidized alloy added to the molten steel and the degree of supersaturation increases, so a deoxidized alloy with a low Ti content is used. To do. Inclusion diameter decreases as the oxygen concentration and Ti content in the alloy decrease, deoxidizing with an alloy having oxygen of 250 ppm or less and Ti content of 70% or less, the average particle diameter is 150 μm or less. It becomes an inclusion. Increasing the Ti content increases the inclusion diameter, and at the time of deoxidation, inclusions with a high proportion of titanium oxide are produced, which remain in the molten steel and are mixed. If the Ti concentration is too low, the amount of deoxidized alloy added becomes too large and the molten steel temperature decreases, making it difficult to solidify and cast the molten steel, and it takes time to add and hinders productivity. Further, when the Ti content is high, it is effective to add a small amount little by little because the portion with a high degree of supersaturation is partially reduced.
[0018]
In addition, by using Ti as an alloy with Fe, Si, and Mn, the supersaturation is further reduced in order to lower the Ti activity and partially reduce the high concentration region. And the formation of composite inclusions of silicon oxide.
[0019]
Ti may be added at once, but may be added in two or more portions. If Ti has a high oxygen content in the molten steel after the addition and CO gas is generated during casting and there is a risk of boiling of the molten steel in the mold, Al may be added in an amount of 0.001% or more after the addition of Ti. As a result, oxygen becomes 20 ppm or less, and casting becomes possible without boiling due to generation of CO gas. Since oxygen is lowered by deoxidation due to the addition of Ti, the amount of Al added is smaller than when Al is added before Ti addition, the amount of inclusions produced is small, and coarse inclusions are also produced. do not do. By making Al 0.005% or less, inclusions include titanium oxide, silicon oxide, manganese oxide, and alumina as main components, titanium oxide 5 to 30%, alumina 2 to 15% and titanium oxide. It becomes an inclusion which exists as a liquid state in molten steel whose sum of alumina is 40% or less.
The molten steel thus produced can be cast by a continuous casting machine through a tundish in the same manner as usual.
[0020]
Ultimately, if the Mn content contained in the steel is lowered to less than 0.05%, the refining time will be long and the economic efficiency will be greatly impaired, so 0.05% is the lower limit, and if it exceeds 1.0%, the steel plate Since the workability of the steel is greatly deteriorated and it cannot be processed depending on the product shape, the upper limit is 1.0%.
Lowering the Si content to less than 0.001% requires sufficient pretreatment, which imposes a significant cost burden on refining and impairs economics. Therefore, the lower limit is 0.001%. If it exceeds 0.04%, plating defects will occur during plating. Occurs and deteriorates surface properties and corrosion resistance, and hardens the material, making it impossible to obtain a soft steel plate, so 0.04% is made the upper limit.
Lowering P to less than 0.001% takes time and cost for hot metal pretreatment and greatly impairs economic efficiency. Therefore, if 0.001% is the lower limit and it exceeds 0.050%, the workability deteriorates and the processing is hindered. The upper limit is 0.050%.
Lowering S to less than 0.001% takes time and cost for hot metal pretreatment, which greatly impairs economic efficiency. If 0.001% is the lower limit and exceeds 0.030%, workability and corrosion resistance deteriorate, and processing as a can.・ Because it hinders performance, the upper limit is 0.030%.
Lowering N to less than 0.0005% greatly impairs economic efficiency with a significant cost increase at the refining stage. Therefore, the lower limit is 0.0005%, and if it exceeds 0.0080%, the amount of Ti added to eliminate solute N Therefore, it is impossible to control the form of inclusions, which is the object of the present application, so the upper limit is set to 0.0080%.
[0021]
In order to reduce the amount of dissolved N, in order to fix N as TiN, it is necessary to make at least Ti (%)> 3.43 × N (%) as described above. Furthermore, in order to improve workability, Ti is preferably added in an amount equal to or greater than that of C. In this case, the amount of Ti added is Ti (%)> 4 × C (%) + 3.43 × N (%).
The upper limit of Ti is 0.030%. If this amount is exceeded, a large amount of Ti must be added during deoxidation, and the inclusion composition characteristic of the present invention cannot be obtained.
[0022]
Nb is mainly added to precipitate and fix C for the purpose of improving workability. The amount of addition is preferably Nb (%)> 6.64 × N (%) when no Ti is added, and Nb (%)> 0.8 when Ti is added and N is precipitated and fixed. Add x 7.75 x C (%). As the lower limit of the amount added, if less than 0.002%, the effect of improving the workability is lost, so 0.002% is the lower limit, and if it exceeds 0.050%, the workability is deteriorated due to the presence of solid solution Nb. The upper limit is 0.050%.
[0023]
The molten steel thus melted is cast by a continuous casting machine through a tundish in the same manner as usual. Further, heating is appropriately performed prior to hot rolling, and the slab is hot-rolled by the same method as usual, and then wound in a temperature range of 600 ° C to 800 ° C. If the coiling temperature is less than 600 ° C, precipitation and fixation of solute N and solute C with Ti and Nb is insufficient and aging deteriorates. Therefore, 600 ° C is the lower limit, and if it exceeds 800 ° C, coarse grains become rough after processing. The upper limit is set to 800 ° C because it causes damage to the appearance. Next, descaling is performed. Generally, pickling is performed, but the scale may be removed mechanically. Then, cold rolling is performed and continuous annealing is performed. The temperature for continuous annealing is 650 ° C to 750 ° C. If the temperature is lower than 650 ° C, the recrystallization is not complete and the workability deteriorates, so the lower limit is 650 ° C. If the temperature exceeds 750 ° C, the high-temperature strength of the steel sheet weakens, causing a phenomenon called squeezing in a continuous annealing furnace and causing breakage. Since problems are likely to occur, the upper limit is 750 ° C. Thereafter, skin pass rolling or DR rolling of about 5 to 40% is performed, and plating such as chromium plating or tin plating is performed to obtain a surface-treated steel sheet. For example, if there is a chromium plating and / or tin plating layer, there may be a very thin layer of Ni or the like at the interface with the base iron, and the tin plating may be a tin-iron alloy plating. Also, a laminated steel plate with a resin film attached to the surface or a resin laminated steel plate coated on at least one side with molten resin does not depart from the surface-treated steel sheet of the present invention.
[0024]
【Example】
Using a deoxidizing alloy having the alloy composition shown in Table 1 in a 270-ton converter, steel of each component was melted and continuously cast. The components of the manufactured steel are summarized in Table 1. The inclusion composition and inclusion size are shown in Table 2. Subsequently, hot rolling was performed. Table 3 shows the winding temperature at that time. Next, after pickling and cold rolling, annealing was performed at the temperatures shown in Table 3. The annealing was performed by box annealing or continuous annealing. Table 3 also shows the recrystallization temperature. After annealing, skin pass rolling or secondary cold rolling was performed. Table 3 shows the rolling reduction. Next, chromium plating or tin plating was applied, and a part of the steel plates was a surface-treated steel plate by attaching a polyethylene terephthalate resin film to the front and back surfaces.
[0025]
A part of the slab and a part of the surface-treated steel sheet were collected, the cross section was examined, and the composition, size, and shape of the inclusions were investigated. The results are shown in Table 2. The composition of inclusions was measured with an energy dispersive analyzer using a scanning electron microscope. In the present invention, almost spherical inclusions were detected in the slab with a composition mainly composed of titanium oxide, manganese oxide, and silicon oxide. Moreover, in the cold rolled steel sheet, these inclusions were crushed and finely dispersed.
[0026]
A drawn can obtained by forming the obtained surface-treated steel sheet into a three-stage drawing and a DI can with a drawing and ironing were manufactured, and the defect rate at which cracking occurred was investigated. The results are shown in Table 3. It can be seen from Table 3 that the steel of the present invention has a lower recrystallization temperature than that of the comparative steel, can be drawn at a low annealing temperature, and has a reduced defect rate.
[0027]
[Table 1]
[0028]
[Table 2]
[0029]
[Table 3]
[0030]
【The invention's effect】
According to the present invention, it is possible to produce a steel sheet for surface treatment with good workability and few defects.

Claims (4)

重量%で、
C :0.0002〜0.0080%、
Si:0.001 〜0.04%、
Mn:0.05〜1.0 %、
P :0.001 〜0.050 %、
S :0.001 〜0.030 %、
Sol.Al:0.001 〜0.005 %、
N :0.0005〜0.0080%、
Ti:0.004 〜0.030 %、
を含有し、残部がFe及び不可避的不純物からなる鋼において、最大粒径が150μm 以下で鋼中の介在物をチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナが主成分でチタン酸化物が5〜30%、アルミナが2〜15%で、かつチタン酸化物とアルミナの和が40%以下である酸化物系介在物を含有せしめたことを特徴とする加工性が良好で欠陥の少ない表面処理用鋼板。
% By weight
C: 0.0002 to 0.0080%,
Si: 0.001 to 0.04%,
Mn: 0.05 to 1.0%,
P: 0.001 to 0.050%,
S: 0.001 to 0.030%,
Sol. Al: 0.001 to 0.005%,
N: 0.0005 to 0.0080%,
Ti: 0.004 to 0.030%,
In which the balance is Fe and inevitable impurities, the maximum particle size is 150 μm or less, and the inclusions in the steel are mainly composed of titanium oxide, manganese oxide, silicon oxide, alumina, and titanium oxide Surface with good workability and few defects, characterized by containing oxide inclusions with 5-30%, alumina 2-15% and the sum of titanium oxide and alumina 40% or less Steel plate for processing.
請求項1記載の成分に加えてさらに、
Nb:0.002 〜0.05%
を含有し、残部がFe及び不可避的不純物からなる鋼において、最大粒径が150μm 以下で鋼中の介在物をチタン酸化物、マンガン酸化物、シリコン酸化物、アルミナが主成分でチタン酸化物が5〜30%、アルミナが2〜15%で、かつチタン酸化物とアルミナの和が40%以下である酸化物系介在物を含有せしめたことを特徴とする加工性が良好で欠陥の少ない表面処理用鋼板。
In addition to the ingredients of claim 1,
Nb: 0.002 to 0.05%
In which the balance is Fe and inevitable impurities, the maximum particle size is 150 μm or less, and the inclusions in the steel are mainly composed of titanium oxide, manganese oxide, silicon oxide, alumina, and titanium oxide Surface with good workability and few defects, characterized by containing oxide inclusions with 5-30%, alumina 2-15% and the sum of titanium oxide and alumina 40% or less Steel plate for processing.
精錬後の溶鋼の鋼中酸素量を250ppm以下に脱酸し、ついでTiを添加し、その後Alを添加して請求項1または2記載の成分の鋼とし、この鋼を連続鋳造−熱間圧延の後、600 〜800 ℃で巻取って、ついで脱スケール処理、冷間圧延後、650 〜750 ℃で連続焼鈍を施し、調質圧延あるいは2次冷間圧延の後、めっき工程を経て表面処理鋼板とする加工性が良好で欠陥が少ない表面処理用鋼板の製造方法。The oxygen content in the steel after refining is deoxidized to 250 ppm or less, then Ti is added, and then Al is added to obtain the steel of the component according to claim 1, which is continuously cast-hot rolled. After that, it is wound at 600-800 ° C, then descaling, cold-rolled, and then subjected to continuous annealing at 650-750 ° C, and after temper rolling or secondary cold rolling, surface treatment is performed through a plating process. A method for producing a steel sheet for surface treatment with good workability and few defects. Alを添加する際に、化学組成がAl:10〜80重量%、残りFe、Mn、Siの1種〜3種及び不可避的不純物からなる合金を添加して行うことを特徴とする請求項3に記載の加工性が良好で欠陥が少ない表面処理用鋼板の製造方法。The alloy is formed by adding an alloy composed of Al: 10 to 80% by weight, the remaining Fe, Mn, and Si, and unavoidable impurities when adding Al. The manufacturing method of the steel plate for surface treatment with favorable workability and few defects as described in 1.
JP08376898A 1998-03-30 1998-03-30 Steel sheet for surface treatment with good workability and few defects and method for producing the same Expired - Fee Related JP3739933B2 (en)

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