JP3951402B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

【００１８】
また、最終仕上焼鈍後は、未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するりん酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付け製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度B₈を測定した。
【００１９】
脱炭焼鈍後の集合組織は、試料の表面から板厚方向に1/5 厚だけ化学研磨した位置で、Ｘ線極点図により測定した。また、極点図の測定データから３次元集合組織を計算により求めた。集合組織の解析にあたっては、｛１１０｝〈００１〉方位、｛１１１｝〈１１２〉方位及び｛１００｝〈０１１〉方位を含むＴＤ回りの回転系列（Bunge 表示のオイラー角でφ₁ ＝90°、φ₂ ＝45°）にまず着目した。着目した理由は、どの試料においても、ほぼ、φ₁ ＝90°、φ₂ ＝45°上に極大値が存在するからである。厳密には、多少のずれを伴うこともあるが、対称性を考慮すると本質的なずれではないと考えられるので、以後の議論は、φ₁ ＝90°、φ₂ ＝45°上に着目して進めることにする。
【００２０】
なお、観察、測定用の試料は、いずれも熱延コイルの長手方向中央付近に対応する位置（以下、「Ｙ部」という。）から採取した。熱延コイルの先端部（以下、「Ｘ部」という。）、尾端部（以下、「Ｚ部」という。）については後で述べる。
【００２１】
図１に例として、鋼スラブとしてａを用い、熱延板焼鈍温度が850 ℃、冷間圧延温度が150 ℃、脱炭焼鈍温度が825 ℃の場合の集合組織について、φ₁ ＝90°、φ₂ ＝45でΦが変化したときのランダム強度比を示した。なお、Φ≧０°とΦ＜０°とでは対称になるので、ここでは０°≦Φ≦90°の範囲で図示した。
図１の場合、極大値を与えるΦは60.1°である。この値は｛１１１｝〈１１２〉（Φ＝54.7°）よりは５°以上大きく、｛１１０｝〈００１〉と〈１１０〉軸回り29.9°の回転関係であることから、｛１１０｝〈００１〉とΣ９の範囲にはない。しかし、その製品はB₈にして1.88T の比較的良好な磁気特性を示した。そこで、実験した全ての試料について、脱炭焼鈍後の集合組織のφ₁ ＝90°、φ₂ ＝45°上で極大を与えるΦの値と、製品の磁束密度B₈との関係を調査し、図２に示した。図２から、｛１１０｝〈００１〉とΣ９の範囲であるΦ：46.1〜56.1°に極大値が存在した場合は全て、製品の磁束密度はB₈にして1.7 T 以下であるという、従来知見からの予想とは異なる結果が得られた。また、極大を与えるΦの値は大き過ぎても製品の磁気特性の不良をもたらす。良好な磁気特性を得るには、極大を与えるΦの値が58°以上62°以下であることが必要条件であることが分かった。
【００２２】
しかし、極大を与えるΦの値が、58°以上62°以下であっても、製品の磁束密度が1.8 以下になる場合もある。その原因を解明するために、集合組織の二つ目の着目点として、副方位の強度を調査した。
脱炭焼鈍後の集合組織において、二番目に強い強度を持つ方位は、｛12４１｝〈０１４〉近傍の方位であった。そこで、｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度との関係を調査した。図３には、φ₁ ＝90°、φ₂ ＝45°上で極大を与えるΦの値が58°以上62°以下であった試料に関して｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度B₈の関係を示した。｛12４１｝〈０１４〉のランダム強度比が3.0 以上の場合に製品のB₈は1.85T 以上となった。ただし、｛12４１｝〈０１４〉方位のランダム強度比が8.6 と極端に高かった試料は、B₈が1.8 T 以下となった。この試料のみ、脱炭焼鈍板における｛12４１｝〈０１４〉方位は、φ₁ ＝90°、φ₂ ＝45°上での極大方位を超えて、最大のピークになっていた。このことから、製品の磁束密度を向上させるには、副方位｛12４１｝〈０１４〉の強度を高めることが大切であるが、最大ピークになるほど大きくなることは有害であることが分かった。
【００２３】
以上の実験結果から、スラブ加熱温度が低く、インヒビターの抑制力が弱い条件下では、最終仕上焼鈍時にΣ９対応粒界が移動しやすいという現象は確認できなかった。
しかも、
・図２でΦ＝60°前後で製品の磁気特性が良好であったこと、
・｛12４１｝〈０１４〉方位と｛１１０｝〈００１〉方位との角度差が約30°であり、この方位の適度な増加が製品の磁気特性向上に有効であること、
から、スラブ加熱温度が低い条件下では、仕上圧延時の粒成長において、Σ９対応粒界が特に移動し易いわけではなく、30°前後の角度差をもつ粒界が移動し易いと考えられる。
【００２４】
次に、脱炭焼鈍板の｛12４１｝〈０１４〉方位の強度が二次再結晶に及ぼす影響について考察する。｛12４１｝〈０１４〉方位も、φ₁ ＝90°、Φ＝60°、φ₂ ＝45°方位も、｛１１０｝〈００１〉方位から30°の角度差である。したがって、仕上焼鈍時の粒成長において、30°前後の角度差を持つ粒界が移動しやすいという点のみからは、脱炭焼鈍板の地がφ₁ ＝90°、Φ＝60°、φ₂ ＝45°方位であることも、｛12４１｝〈０１４〉方位であることも｛１１０｝〈００１〉の成長に関しては同等である。しかし、実験結果からは、φ₁ ＝90°、Φ＝60°、φ₂ ＝45°方位が強いだけでは良好な二次再結晶は生じず、｛12４１｝〈０１４〉方位もある程度強くないといけない。この理由を解明すべく、脱炭焼鈍板の断面組織観察を行った。断面組織観察には、電子線後方散乱図形、以下、ＥＢＳＰ（Electron Back Scattering diffraction Pattern）を用いた。
ＥＢＳＰでは、0.1 μm 以下の空間分解能で結晶方位が測定できる。また、一点の測定に１秒程度しか要しない。更に、結晶粒径よりも十分小さいピッチで二次元試料面上を自動測定し、結晶方位が変化するところを粒界とみなし、測定した領域をマッピングすることができる。そして、マッピングした領域について、粒径分布、平均粒径など解析可能である。ここでは、粒径分布を求める目的でＥＢＳＰを利用した。
【００２５】
図４に脱炭焼鈍板の｛12４１｝〈０１４〉方位のランダム強度比と粒径の変動係数との関係を示す。ここでは、図３同様、φ₁ ＝90°、φ₂ ＝45°上で極大を与えるΦの値が58°以上62°以下であった試料について調査した。図４により、｛12４１｝〈０１４〉方位の増加に伴い、変動係数が大きくなって、非整粒になっていくが、｛12４１｝〈０１４〉方位が最大ピークになるまで増加すると再び粒径がそろってくることが分かる。そして、製品の磁束密度が高くなるのは、変動係数が大きい条件下であるという、従来知見とは異なる結果が得られた。
【００２６】
以上から、｛12４１｝〈０１４〉方位の適度な増加は、粒径を不均一にし、良好な二次再結晶につながることが分かった。なお、脱炭焼鈍板で粒径が不均一な試料について、各結晶粒の方位をＥＢＳＰで測定すると、粗大な粒は｛12４１｝〈０１４〉近傍方位であった。つまり、｛12４１｝〈０１４〉方位の粒は他の方位の粒に比べて粒成長し易いと考えられる。
【００２７】
脱炭焼鈍板の粒径が不均一であることは、スラブ加熱温度が高い場合や、途中窒化を施す場合、すなわち、インヒビターの抑制力が強い場合には有害であると報告されてきたが、この発明のように、インヒビター抑制力が弱い場合には、組織の不均一性がインヒビション効果を補う働きをするのではないかと考えられる。
【００２８】
以上の実験から、この発明においては、
脱炭焼鈍後の板の板厚1/5 層で測定した集合組織が、下記の条件を満たすように制御することとするのである。
集合組織の最大ピークが、Bunge のオイラー角表示で
φ₁ ＝90°±7.5 °、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°±7.5 °
の範囲内に存在し、かつ、
｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上。
なお、集合組織を板厚1/5 層で評価する理由は、最終仕上焼鈍時に、｛１１０｝〈００１〉方位の二次再結晶が板厚1/5 層付近を起点に発生し易く、二次再結晶前のこの部分の集合組織が特に重要だからである
【００２９】
ここまでは、熱延コイルの長手方向中央付近（Ｙ部）に相当する部分についての結果である。実際の製造においては、コイルの全長にわたって良好な特性が得られなければいけない。そこで、実験１、すなわちＹ部において良好な特性（B₈≧1.85T ）が得られた試料について、Ｘ部（熱延コイルの先端部）及びＺ部（尾端部）についても製品の磁束密度B₈を測定したところ、いくつかの試料においてはＸ部又はＺ部でB₈の劣化が生じていた。
【００３０】
そこで、コイル端部での磁気特性不良の要因を調査したところ、仕上圧延開始温度（ＳＴ）がコイル全長にかけて大きく変化する場合に、コイル端部での磁気特性不良が生じることが判明した。図５には、横軸にＸ部の仕上圧延開始温度ＳＴとＺ部の仕上圧延開始温度ＳＴの差を、縦軸にＸ部、Ｙ部、Ｚ部の磁束密度B₈をそれぞれ示し、圧延開始温度の差が磁束密度に及ぼす影響を調べてみた。同図から、ＳＴの絶対値によらず、ＳＴのコイル全長にわたっての変動を100 ℃以内に制御することにより、コイル全長で良好な特性が得られることが分かった。
【００３１】
このことから、圧延開始温度のコイル全長にわたっての変動を100 ℃以内に制御することにより、コイル全長で良好な特性が得られる理由を更に究明すべく、Ｘ部で磁気特性の不良が生じた試料について、脱炭焼鈍板の板厚1/5 層の集合組織を測定したところ、｛12４１｝〈０１４〉方位のランダム強度比が3.0 未満であった。一方、Ｚ部で磁気特性不良が生じた試料について、脱炭焼鈍板の板厚1/5 層の集合組織を測定したところ、｛12４１｝〈０１４〉方位が非常に多く、最大ピークとなっていた。
【００３２】
一般に、圧延開始温度ＳＴは熱延コイルの先端で高く、尾端に向かうにつれて低温になる。そして、圧延開始温度ＳＴが低下すると、熱延途中でのAlN の析出が多くなる。ここにおいて、良好な磁気特性を得べくインヒビター強度を適正に制御するには、熱延板でのAlN の析出状況に応じて熱延板焼鈍温度を変化させなければならないところ、コイルの先端から尾端まで常法に従い一定温度で熱延板焼鈍を施すと、Ｘ部（コイル先端部）ではインヒビターの抑制力が比較的強く、｛12４１｝〈０１４〉方位粒の脱炭焼鈍時の成長が抑えられるために均一な組織となり、また、Ｚ部（コイル尾端部）ではインヒビターの抑制力が比較的弱いために｛12４１｝〈０１４〉方位が試料全体を覆うほどまで成長して均一な組織となって、この発明の方法によれば、どちらも磁気特性の不良になりやすい。しかし、圧延開始温度ＳＴのコイル全長にわたっての変動が100 ℃以内であれば、次工程の熱延板焼鈍でコイル全長にわたるインヒビター強度を適切な状態に制御可能となり、コイル端部での磁気特性の劣化が解消されて、全長にわたって良好な製品が得られことがわかった。
【００３３】
さらに、発明者らは、コイル全長で安定して良好な特性を得るための方法について検討し、脱炭焼鈍時の昇温速度を制御することが有効であることを見出した。実験２にその検討結果を示す。
【００３４】
実験２
表１のａの成分組成の220 mm厚のスラブ３本を1200℃の温度に加熱後、熱間圧延して2.5 mmの熱延コイルとした。その際、仕上圧延開始温度（ＳＴ）は、Ｘ部で1045℃、Ｚ部で950 ℃（その差95℃）に統一した。これらのコイルに925 ℃で30秒間の熱延板焼鈍を施し、酸洗した後、タンデム圧延機で200 ℃の温度で0.34mmの厚みに冷間圧延した。その後、脱脂処理を行い、850 ℃で120 秒間の脱炭焼鈍を施した。
その際、脱炭焼鈍の昇温条件は、以下の３通りに変化させた。
(1) 600 ℃〜750 ℃を平均12℃/secで昇温、
(2) 600 ℃〜750 ℃を平均20℃/secで昇温、
(3) 600 ℃〜750 ℃を平均28℃/secで昇温、
【００３５】
冷間圧延後及び脱炭焼鈍後に、各コイルのＸ部、Ｚ部から試料を採取した。
図６に、脱炭焼鈍板の板厚1/5 層での｛12４１｝〈０１４〉方位のランダム強度比を示す。なお、集合組織の測定方法は実験１と同様である。図６から、昇温速度が速いほど、Ｘ部の｛12４１｝〈０１４〉方位は少なく、Ｚ部の｛12４１｝〈０１４〉方位は多くなり、コイル長手方向での強度の差が大きくなることが分かる。
【００３６】
脱炭焼鈍板の集合組織が、昇温速度によって図６のように変化した理由を考察するため、採取した冷延板（Ｘ部、Ｚ部）に、実験室で脱炭焼鈍を施した。昇温速度は上述の(1) と(3) の２条件とし、850 ℃で120 秒間均熱後の試料と、850 ℃到達後、即時に炉から引き出した試料とについて、断面組織観察を行った。図７に、各試料の結晶粒の平均粒径を示す。昇温速度が28℃/sの場合は850 ℃到達時点での粒径はＸ，Ｚでほとんど差はないが、120 秒均熱後には、インヒビターの抑制力の弱いＺ部で粒成長が顕著に起こっている。一方、昇温速度が12℃/sの場合は、850 ℃到達時点で、既に長手方向に粒成長の差が生じており、インヒビターの抑制力の弱いＺ部の方が、Ｘ部よりも粒径が大きい。しかし、120 秒均熱後に再び粒径を比較すると、長手方向の差が縮小する。これは、850 ℃到達段階で、粒径が大きいほうが、均熱途中の粒成長の駆動力が低下するためと考えられる。
【００３７】
図６と図７から、脱炭焼鈍の昇温速度を遅くすることにより、コイル全長にわたって、粒成長を同程度に制御することが可能であり、その結果、より確実に、コイル全長での｛12４１｝〈０１４〉方位の強度をこの発明の適正範囲に制御できることが明らかとなった。
【００３８】
上記のように、脱炭焼鈍板の集合組織を制御することが必要なのであるが、そのためには、以下に示す条件に従う必要がある。
（成分について）
Ｃ：0.02wt％以上、0.06wt％以下
Ｃは、組織を改善し、二次再結晶を安定化させるために必要な成分で、そのためには、0.02wt％以上が必要である。しかし、0.06wt％を超えると冷延時の破断が増加すること、また、脱炭焼鈍後の組織が均一になり過ぎて、この発明には適さないことから、0.06wt％以下とする。
Si：2.0 wt％以上、4.5 wt％以下
Siは、電気抵抗を増加させ鉄損を低減するために必須の成分であり、このためには2.0 wt％以上含有させることが必要であるが、4.5 wt％を超えると加工性が劣化し、製造や製品の加工が極めて困難になるので、2.0 wt％以上4.5 wt％以下の範囲とする。
Mn：0.03wt％以上、2.5 wt％以下
MnもSiと同様に電気抵抗を高める成分であり、また、製造時の熱間加工性を向上させるので必要な成分である。この目的のためには、0.03wt％以上の含有が必要であるが、2.5 wt％を超えて含有した場合、γ変態を誘起して磁気特性が劣化するので、0.03wt％以上、2.5 wt％以下の範囲とする。
【００３９】
Al：0.005 wt％以上、0.030 wt％以下
Alは、インヒビター成分として、0.005 wt％以上、0.030 wt％以下を含有させることが必要である。AlはＮと結びついてAlN としてインビビターの役割を果たし、特にAlN をスラブ加熱時に固溶させ、熱延板焼鈍の昇温過程で微細析出させることにより、一次再結晶粒の成長抑制効果が高まる。しかし、Alの含有量が0.005 wt％未満の場合、熱延板焼鈍の昇温過程において析出するAlN の量が不足し、逆に0.030 wt％を超える場合も、1260℃以下でのスラブ加熱の際にAlN の固溶が困難となるために熱延板焼鈍の昇温過程において微細に析出するAlN の量が不足する。したがって、インヒビターとしての効果を有効に発揮させるために、Alの含有量は0.005 wt％以上、0.030 wt％以下とする。
Ｎ：0.0030wt％以上、0.0100以下
ＮはAlN を形成し、インヒビターとして機能するので、0.0030wt％以上含有させることが必要である。しかしながら、0.0100wt％を超えて含有すると鋼中でガス化し、膨れ等の欠陥をもたらすので、0.0030wt％以上、0.0100wt％以下の範囲にしなければならない。
【００４０】
その他のインヒビター成分
Sb、Nb、Sn、Cr、Se、Ｓ等を必要に応じて添加し、インヒビターとして機能させることもできる。特に、SbもしくはSnは、熱間圧延において微細な析出物を形成し、次工程の熱延板焼鈍の昇温過程におけるAlN の析出核を増加させる作用を有するので有効である。かかる作用を得るためには、これらの成分を0.001 wt％以上添加することが必要であるが、0.30wt％を超えると製品のベンド特性等、機械的特性が劣化するので、その含有量は0.001 wt％以上、0.30wt％以下とするのが好ましい。
【００４１】
（熱間圧延）
以上の成分に調整されたスラブは、通常の方法に従い、スラブ加熱に供されたのち、熱間圧延により熱延コイルとされる。
スラブ加熱温度は、1260℃以下とする。スラブ加熱温度が低いことは、エネルギーコスト低減のために好ましいだけでなく、AlN 等のインビビター成分の析出状態に適度な不均一性を生じさせ、脱炭焼鈍後の粒径分布の不均一性を助長するという点で好ましい。
なお、近年、スラブ加熱を行わず、連続鋳造後、直接熱間圧延を行う方法が開示されているが、この方法は、スラブ加熱温度を低くとれるので、この発明においても好適に実施し得る。
また、コイル全長で良好な磁気特性を得るために、熱間圧延の仕上圧延開始温度の変動は、コイル全長で100 ℃以内に制御されなければならない。
【００４２】
（熱延板焼鈍）
熱延板焼鈍は、950 ℃以下で行うことが好ましい。熱延板焼鈍の目的は、熱延板の組織を均一化することと、インヒビターの微細析出を促すことにあるので、一般には1000℃以上の高温で行われるが、この発明では組織の均一化は必要なく、むしろ有害であるため、極めて低温で行うこととする。しかし、インヒビターを微細析出させることは必要不可欠であるので、熱延板焼鈍を省略したり、800 ℃未満で行うことは好ましくない。
【００４３】
（冷間圧延）
冷間圧延はタンデム圧延機で100 ℃以上の温度で行うことが好ましい。タンデム圧延機は歪速度が大きく、パス間時間が短いので、かかるタンデム圧延機で100 ℃以上の温度で温間圧延を施すと、不均一変形が促進される。圧延時の不均一変形は、脱炭焼鈍時の一次再結晶粒の成長の不均一性を助長する。脱炭焼鈍板の粒径の不均一性は、｛12４１｝〈０１４〉方位の適度な増加に対応し、製品の磁気特性向上に結びつくので、好ましい。
【００４４】
（脱炭焼鈍、最終仕上焼鈍、コーティング）
冷間圧延後、脱炭焼鈍を常法に従い施したのち、焼鈍分離剤を塗布し、最終仕上焼鈍を施す。
脱退焼鈍の昇温過程においては、コイル全長で良好な磁気特性を得るために、600 ℃〜750 ℃の昇温速度を20℃/s以下とすることが好ましい。
最終仕上焼鈍後は、必要に応じて絶縁コーティングを塗布焼き付け、更に平坦化焼鈍を施し、製品とする。
【００４５】
【実施例】
（実施例１）
表１に示すｅ、ｆの成分組成の200 mm厚のスラブ各９本を、1150℃の温度に加熱後、熱間圧延して2.4 mmの熱延コイルとした。仕上圧延開始温度は、Ｘ部で990 ℃、Ｚ部で925 ℃に制御した。これらのコイルは、60秒間の熱延板焼鈍を施し、酸洗した後、タンデム圧延機で0.34mmの厚みに冷間圧延した。この際、熱延板焼鈍温度を850 ℃、940 ℃及び1030℃の３通り、冷間圧延温度を60℃、120 ℃及び200 ℃の３通りに変化させた。その後、脱脂処理を行い、830 ℃で120 秒間の脱炭焼鈍を施したのち、焼鈍分離剤を塗布して最終仕上焼鈍を施した。なお、脱炭焼鈍の昇温過程の600 〜750 ℃の昇温速度は16℃/sに制御した。
【００４６】
脱炭焼鈍後、試料の一部を採取し、板厚1/5 層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
最終仕上焼鈍後、未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するりん酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付けて製品とした。
各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度B₈とW_17/50（磁束密度1.7 T における鉄損）を測定した。
【００４７】
表２，表３に、脱炭焼鈍板の集合組織と製品の磁気特性とを示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°上で極大を与えるΦの値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料は、備考欄に※印を付与した。また、集合組織と磁気測定は、コイル長手方向の先端部（Ｘ部）、中央付近（Ｙ部）、及び尾端部（Ｚ部）のそれぞれより試料を採取して行った。
【００４８】
【表２】

【００４９】
【表３】

【００５０】
表２、表３に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°の範囲内に存在し、かつ、｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱延板焼鈍温度を950 ℃以下とし、冷間圧延をタンデム圧延機で100 ℃以上で行うことが極めて有効であることがわかる。
【００５１】
（実施例２）
表１に示すｅの成分組成の200 mm厚のスラブ６本を1150℃の温度に加熱後、以下の３条件で２本ずつ熱間圧延して2.4 mmの熱延コイルとした。
(A) Ｘ部の仕上圧延開始温度980 ℃、Ｚ部の仕上圧延開始温度930 ℃、
(B) Ｘ部の仕上圧延開始温度995 ℃、Ｚ部の仕上圧延開始温度905 ℃、
(C) Ｘ部の仕上圧延開始温度1015℃、Ｚ部の仕上圧延開始温度880 ℃、
これらのコイルに、850 ℃で60秒間の熱延板焼鈍を施し、酸洗したのち、タンデム圧延機で0.34mmの厚みに冷間圧延した。その後、脱脂処理を行い、830 ℃で120 秒間の脱炭焼鈍を施したのち、焼鈍分離剤を塗布して最終仕上焼鈍を施した。脱炭焼鈍の昇温条件は、以下の２通りに変化させた。
（イ）600 〜750 ℃の昇温速度が10℃/s、
（ロ）600 〜750 ℃の昇温速度が26℃/s、
【００５２】
脱炭焼鈍後、試料の一部を採取し、板厚1/5 層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
最終仕上焼鈍後、未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するりん酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付け製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度B₈とW_17/50（磁束密度1.7 T における鉄損）を測定した。
表４に、脱炭焼鈍板の集合組織と製品の磁気特性とを示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°で極大を与えるΦの値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料については、表中に※を付与した。また、集合組織と磁気測定は、熱延コイル長手方向のＸ部、Ｙ部、Ｚ部それぞれに対応する位置より試料を採取して行った。
【００５３】
【表４】

【００５４】
表４に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°の範囲内に存在し、かつ、｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、コイル全長にわたって、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱間圧延の仕上圧延開始温度のコイル全長での変動を100 ℃以内に制御し、脱炭焼鈍の昇温過程の600 ℃〜750 ℃の昇温速度を20℃/s以下とすることが極めて有効であることがわかる。
【００５５】
（実施例３）
表１に示すｇ、ｈの成分組成の250 mm厚のスラブ各９本を、1220℃の温度に加熱後、熱間圧延して2.7 mmの熱延コイルとした。仕上圧延開始温度は、Ｘ部で1020℃、Ｚ部で940 ℃に制御した。これらのコイルに、60秒間の熱延板焼鈍を施し、酸洗した後、80℃の温度で1.6 mmの厚みまで第１回目のタンデム圧延機による冷間圧延を施し、950 ℃の温度で中間焼鈍を施したのち、酸洗し、0.22mmの厚みまでの第２回目のタンデム圧延機による冷間圧延を施した。この際、熱延板焼鈍温度を800 ℃、900 ℃及び1000℃の３通り、第２回目の冷間圧延温度を80℃、150 ℃及び250 ℃の３通りに変化させた。その後、脱脂処理を行い、850 ℃で120 秒間の脱炭焼鈍を施したのち、焼鈍分離剤を塗布して最終仕上焼鈍を施した。なお、脱炭焼鈍の昇温過程の600 〜750 ℃の昇温速度は16℃/sに制御した。
脱炭焼鈍後、試料の一部を採取し、板厚1/5 層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
最終仕上焼鈍後、未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するりん酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付けて製品とした。
各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度B₈とW_17/50（磁束密度1.7 T における鉄損）を測定した。
【００５６】
表５、表６に、脱炭焼鈍板の集合組織と製品の磁気特性との関係を示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°上で極大を与えるΦの値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料は、備考欄に※印を付与した。また、集合組織と磁気測定は、コイル長手方向の先端部（Ｘ部）、中央付近（Ｙ部）、及び尾端部（Ｚ部）のそれぞれより試料を採取して行った。
【００５７】
【表５】

【００５８】
【表６】

【００５９】
表５、表６に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°の範囲内に存在し、かつ、｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱延板焼鈍温度を950 ℃以下とし、冷間圧延をタンデム圧延機で100 ℃以上で行うことが極めて有効であることがわかる。
【００６０】
（実施例４）
表１に示すｇの成分組成の250 mm厚のスラブ６本を1220℃の温度に加熱後、以下の３条件で２本ずつ熱間圧延して2.7 mmの熱延コイルとした。
(D) Ｘ部の仕上圧延開始温度1010℃、Ｚ部の仕上圧延開始温度950 ℃、
(E) Ｘ部の仕上圧延開始温度1025℃、Ｚ部の仕上圧延開始温度935 ℃、
(F) Ｘ部の仕上圧延開始温度1040℃、Ｚ部の仕上圧延開始温度910 ℃、
これらのコイルは、900 ℃で60秒間の熱延板焼鈍を施し、酸洗したのち、80℃の温度で1.6 mmの厚みまでの第１回目のタンデム圧延機による冷間圧延を施し、950 ℃の温度で中間焼鈍を施したのち、酸洗し、0.22mmの厚みまでの第２回目のタンデム圧延機による冷間圧延を施した。この第２回目の冷間圧延温度は、220 ℃とした。その後、脱脂処理を行い、850 ℃で120 秒間の脱炭焼鈍を施したのち、焼鈍分離剤を塗布して最終仕上焼鈍を施した。脱炭焼鈍の昇温条件は、以下の２通りに変化させた。
（ハ）600 〜750 ℃の昇温速度が9 ℃/s、
（ニ）600 〜750 ℃の昇温速度が27℃/s、
脱炭焼鈍後、試料の一部を採取し、板厚1/5 層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
【００６１】
最終仕上焼鈍後、未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するりん酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付け製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度B₈とW_17/50（磁束密度1.7 T における鉄損）を測定した。
表７に、脱炭焼鈍板の集合組織と製品の磁気特性とを示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°で極大を与えるΦの値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料については、表中に※を付与した。また、集合組織と磁気測定は、熱延コイル長手方向のＸ部、Ｙ部、Ｚ部それぞれに対応する位置より試料を採取して行った。
【００６２】
【表７】

【００６３】
表７に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°の範囲内に存在し、かつ、｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、コイル全長にわたって、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱間圧延の仕上圧延開始温度のコイル全長での変動を100 ℃以内に制御し、脱炭焼鈍の昇温過程の600 ℃〜750 ℃の昇温速度を20℃/s以下とすることが極めて有効であることがわかる。
【００６４】
【発明の効果】
この発明により、磁気特性を良好に保った汎用一方向性電磁鋼板を安定して製造することが可能になった。
【図面の簡単な説明】
【図１】脱炭焼鈍版の集合組織のφ₁ ＝90°、φ₂ ＝45°断面においてΦが変化したときのランダム強度比を示す図である。
【図２】φ₁ ＝90°、φ₂ ＝45°断面上で極大を与えるΦの値と、製品の磁束密度Ｂ₈ との関係を示す図である。
【図３】｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度Ｂ₈ の関係を示す図である。
【図４】脱炭焼鈍板の｛12４１｝〈０１４〉方位のランダム強度比と粒径の変動係数との関係を示す図である。
【図５】コイル全長にわたる仕上圧延開始温度の差が製品の磁束密度に及ぼす影響を示す図である。
【図６】脱炭焼鈍の昇温速度が、脱炭焼鈍板の板厚1/5 層での｛12４１｝〈０１４〉方位のランダム強度比に及ぼす影響を示す図である。
【図７】脱炭焼鈍における850 ℃到達時及び850 ℃で120 秒均熱後の一次再結晶粒の平均粒径を、コイルＸ部とＺ部とで示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a grain-oriented electrical steel sheet, and more particularly to a method for stably producing a general-purpose grain-oriented silicon steel sheet having good magnetic properties.
[0002]
[Prior art]
Oriented silicon steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and it is fundamentally important that they have excellent magnetic properties such as magnetic flux density and iron loss value. Therefore, a slab having a thickness of 100 to 300 mm is hot-rolled after high-temperature heating, and then this hot-rolled sheet is made into a final sheet thickness by one or more cold rollings sandwiching intermediate annealing, and after decarburization annealing, It is manufactured through a complicated process in which an annealing separator is applied and then final finish annealing is performed for the purpose of secondary recrystallization and purification. In order to enhance the magnetic properties of such a directional silicon steel plate, the {110} <001> orientation in which the <001> axis, which is the easy axis of magnetization, is aligned in the rolling direction by secondary recrystallization in the finish annealing step. It is important to grow crystal grains (so-called goth orientation).
[0003]
In order to effectively promote secondary recrystallization such that crystal grains are highly accumulated in the {110} <001> orientation, the following three points are important.
The first is to disperse a dispersed phase called an inhibitor that suppresses the growth of primary recrystallized grains to a uniform and appropriate size. Inhibitors have the effect of suppressing the growth of primary recrystallized grains during the final finish annealing, whereby only the grains with the {110} <001> orientation with the highest grain growth advantage can be grown. The grains are engulfed and grow large. Therefore, the inhibitory force of the inhibitor must be controlled to such a strength that only the grains of {110} <001> orientation can grow and the growth of other grains can be stopped.
[0004]
Typical examples of such inhibitors include sulfides such as MnS, MnSe, AlN and VN, selenium compounds, nitrides, and the like, which have extremely low solubility in steel. In order to exert the action as an inhibitor, in the manufacturing process, a method has been adopted in which the inhibitor is once completely dissolved in the slab before the hot rolling and then finely precipitated in the subsequent process. The slab heating temperature for sufficiently dissolving this inhibitor is about 1400 ° C, which is about 200 ° C higher than the slab heating temperature of ordinary steel. Such high temperature slab heating has the following drawbacks.
1) High energy intensity due to high temperature heating.
2) Melt scale is likely to occur and slab sag is likely to occur.
3) Over decarburization of the slab surface occurs.
4) In order to solve the problems 2) and 3), an induction furnace dedicated to oriented silicon steel was devised, but the problem of increased energy costs remained.
[0005]
Many studies have been made to achieve low temperature slab heating of oriented silicon steel in order to overcome the above drawbacks. A decrease in the slab heating temperature inevitably leads to a shortage of the amount of the inhibitor component in the solution, and thus inevitably causes a decrease in the inhibitory ability of the inhibitor. Therefore, an intermediate nitriding technique has been developed as a technique to compensate for the decrease in the suppression force caused by low-temperature slab heating in a later process. As this nitriding technique, for example, Japanese Patent Laid-Open No. 57-207114 discloses a technique of nitriding at the time of decarburization annealing, and Japanese Patent Laid-Open No. 62-70521 specifies finish annealing conditions and at the time of finish annealing. A technique that enables low-temperature slab heating by nitriding in the middle is disclosed. Furthermore, Japanese Patent Application Laid-Open No. 62-40315 has disclosed a method in which the inhibitor can be controlled to an appropriate state by nitriding during the subsequent process even if Al and N are not dissolved at the time of slab heating.
However, the method of performing nitriding on the way before the finish annealing requires new equipment, and there is a problem that the cost increases, and the problem that nitriding during the finish annealing is difficult to control remains. ing.
[0006]
The second is to appropriately control the crystal grain size distribution after the primary recrystallization. Studies have been conducted on the crystal grain size of the primary recrystallization structure from the viewpoint of controlling the driving force of secondary recrystallization. For example, in Japanese Patent Laid-Open No. 2-182866, a primary recrystallized structure having an average primary recrystallized grain diameter of 15 μm or more and a coefficient of variation (standard deviation of grain size distribution normalized by the average diameter) of 0.6 or less is used. It was disclosed that it was important to have it. In Japanese Patent Laid-Open No. 4-337029, the amount of N in steel in the annealing process before the final cold rolling is detected, and primary recrystallization annealing is performed so as to obtain primary recrystallized grains in the range of 15 to 25 μm based on the result. A technique for changing the set temperature is disclosed. Furthermore, in Japanese Patent Laid-Open No. 6-33141, the average diameter of primary recrystallized grains after decarburization annealing is 6 to 11 μm and the coefficient of variation is 0.5 or less, and the primary recrystallization just before the start of secondary recrystallization of final finish annealing. A technique for increasing the average diameter of recrystallized grains by 5 to 30% has been disclosed. As in these publications, there are various theories on the optimal primary recrystallization grain size. In order to cause secondary recrystallization, it is important to finely control the balance between the driving force of grain growth and the inhibitory force of the inhibitor that suppresses it, and the inhibitor depends on the chemical composition and process conditions of the steel sheet. When the restraining force of is changed, the optimum driving force, that is, the optimum primary recrystallization grain size is also changed. However, the fact that a smaller coefficient of variation is better is a consistent view of previous technologies. As a technique for controlling both inhibitory inhibitory force and driving force for grain growth, JP-A-4-297524 discloses that the average grain size of primary recrystallized grains is 18 to 35 μm, and after hot rolling, secondary recrystallization is performed. A technique for performing nitriding before the start is disclosed.
[0007]
The third is proper control of the primary recrystallization texture. In order to further enhance the superiority of grain growth in the {110} <001> orientation during the final finish annealing, the ground orientation is strongly accumulated in the {111} <112> orientation, and secondary recrystallization is included therein. It has been considered important to have a {110} <001> orientation with a high degree of sharpness, which is the core of.
This concept is based on the theory that grain boundaries in a Σ9 correspondence are easy to move. Strictly speaking, the Σ9 correspondence relationship means that the grains on both sides of the grain boundary are in a rotational relationship of 38.9 degrees around the <110> axis, but in general, in the range where the rotation angle is 38.9 ± 5.0 degrees, Σ9 It can be regarded as a relationship (Brandon condition). Here, the {110} <001> orientation and the {111} <112> orientation have a rotational relationship of 35.3 ° C. around the <110> axis, and are within a range that can be regarded as a correspondence relationship of Σ9. Therefore, in the primary recrystallized texture, a state in which {110} <001> having high sharpness is scattered in the ground strongly accumulated in {111} <112> is the {110} <001> orientation. It has been considered advantageous for secondary recrystallization.
[0008]
In summary, in order to produce secondary recrystallization accumulated in the {110} <001> orientation,
(B) A strong inhibitor suppressing power is required, and for that purpose, the slab heating temperature should be raised to about 1400 ° C, or nitridation in the middle is required.
(B) The primary recrystallized structure needs to be controlled in a state where the variation in particle size is small, that is, in a sized state,
(C) The primary recrystallization texture should be controlled so that the orientation of the ground is strongly accumulated in {111} <112>, and {110} <001> with high sharpness is scattered therein. ,
These three points have been considered important.
[0009]
[Problems to be solved by the invention]
However, as described above, when the slab heating temperature is increased, a problem may be caused in terms of quality, which is disadvantageous in terms of cost. The intermediate nitriding method also has a problem in terms of cost and controllability, and it has been difficult to achieve both good magnetic properties of the product and reduction in manufacturing cost. The primary recrystallized structure that has been considered desirable in the past has not solved the problem of achieving both good magnetic properties and cost reduction.
[0010]
The problem to be solved by the present invention is that the slab heating temperature is as low as that of ordinary steel in the production of general-purpose directional silicon steel sheets that require cost reduction, and the magnetic characteristics are well maintained over the entire coil length. This is the development of an advantageous method for producing a porous silicon steel sheet. In particular, it is an object to produce a grain-oriented silicon steel sheet with stable magnetic properties without aggressive nitriding.
[0011]
[Means for Solving the Problems]
As a result of intensive research, the inventors of the present invention have made directional silicon with a slab heating temperature as low as that of ordinary steel and good magnetic properties in the manufacture of general-purpose oriented silicon steel sheets that require cost reduction. A new method has been found for producing steel sheets without aggressive nitriding.
[0012]
  Based on the above findings, the present invention provides C: 0.02-0.06 wt%, Si: 2.0-4.5 wt%, Mn: 0.03-2.5 wt%, Al: 0.005-0.030 wt%, and N: 0.003-0.010 wt%. Containing silicon steel slabTheAfter heating, hot rolling consisting of rough rolling and finish rollingTheAfter performing hot-rolled sheet annealing, the final sheet thickness is obtained by cold rolling at least once with intermediate or intermediate annealing, followed by decarburization annealing and then annealing after applying an annealing separator. In the manufacturing method of the grain-oriented electrical steel sheet to be applied,Slab heating temperature 1260 After the hot rolling, the variation of the finish rolling start temperature over the entire coil length 100 By controlling to be within ℃, and adjusting the hot-rolled sheet annealing temperature, by adjusting the rolling temperature as tandem rolling cold rolling,The grain-oriented electrical steel sheet manufacturing method is characterized in that the texture in the 1/5 layer thickness region of the sheet after decarburization annealing is a structure that satisfies the following conditions.
                                Record
  The maximum peak orientation of the texture is displayed in Bunge's Euler angle display.
φ₁ = 90 ° ± 7.5 °, Φ: 58-62 ° or -58--62 °, φ₂ = 45 ° ± 7.5 °
And the random intensity ratio of {1241} <014> is 3.0 or more.
  In this invention,
・ Hot-rolled sheet annealing is performed at a temperature of 950 ° C or lower, and cold rolling is performed at a temperature of 100 ° C or higher with a tandem rolling mill.
・ The heating rate of 600 to 750 ℃ in the annealing process of decarburization annealing shall be 20 ℃ / s or less,
It is more preferable to perform one or both of the above.
[0013]
In the present invention, the random intensity ratio represents an abundance ratio of a specific orientation, and (an abundance ratio of a portion having a specific orientation at a measurement site) ÷ (a virtual orientation having no orientation at all). Abundance ratio of the possessed portion). The crystal orientation is measured by X-ray diffraction intensity or the like.
[0014]
The Euler angle is described in “Aggregate Texture” (written by Keiichi Nagashima; published on January 20, 1984, published by Maruzen Co., Ltd.) p.7-9. See pages 35-36 of the same book.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the following, experiments that have led to the above invention will be described, and embodiments of the present invention will be described in detail.
In the conventional technique, the primary recrystallized structure is sized (under (b) described above) and the primary recrystallized texture is changed to {111 under the condition that the inhibitor has a very strong inhibitory force as described in (a) above. } There have been many reports that it is effective to strongly accumulate <112> (the above-mentioned (c)). However, the inventors have conducted intensive research based on the idea that (b) (c) is not necessarily effective under conditions where the inhibitor is weak.
[0016]
(Experiment 1)
10 slabs each having a thickness of 200 mm having a composition of a to d shown in Table 1 were heated to a temperature of 1200 ° C. and then hot-rolled to form a 2.5 mm hot-rolled coil. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm with a tandem rolling mill. Then, after degreasing and performing decarburization annealing for 120 seconds, the final finish annealing was performed by applying an annealing separator.
During these steps, the hot-rolled sheet annealing temperature was changed in the range of 700 to 1150 ° C, the cold rolling temperature in the range from room temperature to 350 ° C, and the decarburization annealing temperature in the range of 750 to 950 ° C. After decarburization annealing, a part of the sample was collected, and the structure was observed and the texture was measured.
[0017]
[Table 1]

[0018]
Further, after the final finish annealing, the unreacted annealing separator was removed, and an insulating coating containing magnesium phosphate containing colloidal silica as a main component was applied, and a product baked at 800 ° C. was obtained. From each product, cut out Epstein-sized test pieces along the rolling direction to obtain magnetic flux density B₈Was measured.
[0019]
The texture after decarburization annealing was measured by an X-ray pole figure at a position where 1/5 thickness was chemically polished from the surface of the sample in the thickness direction. In addition, a three-dimensional texture was calculated from the measurement data of the pole figure. In the analysis of the texture, a rotation sequence around TD including the {110} <001>, {111} <112>, and {100} <011> directions (Bunge's Euler angle φ₁= 90 °, φ₂= 45 °) first. The reason for focusing on₁= 90 °, φ₂This is because there is a local maximum above 45 °. Strictly speaking, there may be some deviation, but considering the symmetry, it is considered not an essential deviation.₁= 90 °, φ₂= Focus on 45 ° above and proceed.
[0020]
Note that the samples for observation and measurement were collected from a position corresponding to the vicinity of the center in the longitudinal direction of the hot-rolled coil (hereinafter referred to as “Y portion”). The distal end portion (hereinafter referred to as “X portion”) and the tail end portion (hereinafter referred to as “Z portion”) of the hot rolled coil will be described later.
[0021]
As an example in FIG. 1, for a texture when a is used as a steel slab, the hot-rolled sheet annealing temperature is 850 ° C, the cold rolling temperature is 150 ° C, and the decarburization annealing temperature is 825 ° C.₁= 90 °, φ₂= Random intensity ratio when Φ changed at 45. It should be noted that since Φ ≧ 0 ° and Φ <0 ° are symmetric, the illustration is made in the range of 0 ° ≦ Φ ≦ 90 °.
In the case of FIG. 1, Φ giving the maximum value is 60.1 °. This value is 5 ° or more larger than {111} <112> (Φ = 54.7 °), and is {110} <001> and a rotational relationship of 29.9 ° around the <110> axis, so that {110} <001> And not in the range of Σ9. But its product is B₈It showed relatively good magnetic properties of 1.88T. Therefore, for all samples tested, the texture φ after decarburization annealing₁= 90 °, φ₂= The value of Φ that gives the maximum at 45 ° and the magnetic flux density B of the product₈The relationship between and is shown in FIG. From FIG. 2, in all cases where the maximum value exists in the range of {110} <001> and Σ9, Φ: 46.1 to 56.1 °, the magnetic flux density of the product is B₈As a result, the result was less than 1.7 T, which was different from the expectation from the conventional knowledge. Moreover, even if the value of Φ that gives the maximum is too large, the magnetic properties of the product are deteriorated. In order to obtain good magnetic properties, it has been found that the value of Φ giving the maximum is 58 ° or more and 62 ° or less.
[0022]
However, even if the value of Φ giving the maximum is 58 ° or more and 62 ° or less, the magnetic flux density of the product may be 1.8 or less. To elucidate the cause, we investigated the strength of the secondary orientation as the second focus of texture.
In the texture after decarburization annealing, the orientation with the second strongest strength was the orientation in the vicinity of {1241} <014>. Therefore, the relationship between the random intensity ratio in the {1241} <014> orientation and the magnetic flux density of the product was investigated. In FIG.₁= 90 °, φ₂= Random strength ratio of {1241} <014> orientation and magnetic flux density B of the product for the sample whose Φ value giving the maximum at 45 ° is 58 ° or more and 62 ° or less₈Showed the relationship. If the random intensity ratio of {1241} <014> is 3.0 or more, B₈Became 1.85T or more. However, the sample whose random intensity ratio in the {1241} <014> orientation was extremely high at 8.6 is B₈Became 1.8 T or less. Only in this sample, the {1241} <014> orientation in the decarburized annealing plate is φ₁= 90 °, φ₂= Beyond the maximum direction at 45 °, it was the largest peak. From this, in order to improve the magnetic flux density of the product, it is important to increase the strength of the sub-azimuth {1241} <014>, but it has been found that increasing the maximum peak is harmful.
[0023]
From the above experimental results, it was not possible to confirm the phenomenon that the Σ9-corresponding grain boundary easily moves during the final finish annealing under the condition that the slab heating temperature is low and the inhibitor's inhibitory force is weak.
Moreover,
・ In Fig. 2, the magnetic properties of the product were good around Φ = 60 °.
The angular difference between the {1241} <014> orientation and the {110} <001> orientation is about 30 °, and a moderate increase in this orientation is effective in improving the magnetic properties of the product;
Therefore, it is considered that under the condition where the slab heating temperature is low, the grain boundary corresponding to Σ9 is not particularly easily moved during grain growth during finish rolling, and the grain boundary having an angular difference of about 30 ° is likely to move.
[0024]
Next, the influence of the strength of the {1241} <014> orientation of the decarburized annealed plate on the secondary recrystallization will be considered. {1241} <014> orientation is φ₁= 90 °, Φ = 60 °, φ₂= 45 ° azimuth is also an angle difference of 30 ° from the {110} <001> azimuth. Therefore, the ground of the decarburized annealing plate is φ only because the grain boundaries with an angle difference of around 30 ° are likely to move during grain growth during finish annealing.₁= 90 °, Φ = 60 °, φ₂= 45 ° azimuth and {1241} <014> azimuth are equivalent for the growth of {110} <001>. However, from the experimental results,₁= 90 °, Φ = 60 °, φ₂If the = 45 ° orientation is strong, good secondary recrystallization does not occur, and the {1241} <014> orientation must be strong to some extent. In order to elucidate the reason, the cross-sectional structure of the decarburized annealed plate was observed. For cross-sectional structure observation, an electron beam backscattering pattern, hereinafter referred to as EBSP (Electron Back Scattering Diffraction Pattern), was used.
With EBSP, crystal orientation can be measured with a spatial resolution of 0.1 μm or less. In addition, only one second is required for one point of measurement. Furthermore, it is possible to automatically measure the two-dimensional sample surface with a pitch sufficiently smaller than the crystal grain size, and to regard the place where the crystal orientation changes as the grain boundary, and to map the measured region. And about the mapped area | region, particle size distribution, an average particle diameter, etc. are analyzable. Here, EBSP was used for the purpose of obtaining the particle size distribution.
[0025]
FIG. 4 shows the relationship between the random strength ratio of the {1241} <014> orientation of the decarburized annealed plate and the coefficient of variation of the particle size. Here, as in FIG.₁= 90 °, φ₂= A sample having a value of Φ giving a maximum at 45 ° was 58 ° to 62 ° was investigated. According to FIG. 4, as the {1241} <014> orientation increases, the coefficient of variation increases and becomes non-sized, but when the {1241} <014> orientation increases to the maximum peak, the particle size is increased again. You can see that And the result from which the magnetic flux density of a product becomes high is a condition different from the conventional knowledge that the coefficient of variation is large.
[0026]
From the above, it was found that a moderate increase in the {1241} <014> orientation makes the grain size non-uniform and leads to good secondary recrystallization. In addition, when the orientation of each crystal grain was measured by EBSP for a sample with a non-uniform grain size on a decarburized annealed plate, the coarse grains were in the vicinity of {1241} <014>. That is, it is considered that grains with {1241} <014> orientation are easier to grow than grains with other orientations.
[0027]
The non-uniform grain size of the decarburized annealed plate has been reported to be harmful when the slab heating temperature is high or when nitriding is performed midway, that is, when the inhibitor's inhibitory power is strong, As in the present invention, when inhibitor inhibitory power is weak, it is considered that tissue non-uniformity may serve to supplement the inhibition effect.
[0028]
From the above experiment, in the present invention,
The texture measured at the 1 / 5th layer thickness of the plate after decarburization annealing is controlled so as to satisfy the following conditions.
The maximum peak of the texture is displayed in Bunge's Euler angle display.
φ₁= 90 ° ± 7.5 °, Φ: 58-62 ° or -58--62 °, φ₂= 45 ° ± 7.5 °
Within the scope of
Random intensity ratio of {1241} <014> orientation is 3.0 or more.
The reason why the texture is evaluated with a thickness of 1/5 layer is that secondary recrystallization in the {110} <001> orientation is likely to occur from the vicinity of the thickness of 1/5 layer during the final finish annealing. This is because the texture of this part before the next recrystallization is particularly important
[0029]
Up to this point, the results have been obtained for the portion corresponding to the vicinity of the center in the longitudinal direction (Y portion) of the hot rolled coil. In actual manufacturing, good characteristics must be obtained over the entire length of the coil. Therefore, in Experiment 1, that is, a good characteristic (B₈≧ 1.85T), the magnetic flux density B of the product in the X part (the tip of the hot rolled coil) and the Z part (the tail end)₈As a result of measurement, in some samples, B in the X part or Z part₈Degradation occurred.
[0030]
Therefore, the cause of the magnetic characteristic failure at the coil end was investigated, and it was found that when the finish rolling start temperature (ST) changes greatly over the entire length of the coil, the magnetic characteristic failure at the coil end occurs. In FIG. 5, the horizontal axis indicates the difference between the finish rolling start temperature ST of the X part and the finish rolling start temperature ST of the Z part, and the vertical axis indicates the magnetic flux density B of the X part, the Y part, and the Z part.₈The effect of the difference in rolling start temperature on the magnetic flux density was investigated. From the figure, it was found that good characteristics can be obtained over the entire coil length by controlling the variation of the ST over the entire coil length within 100 ° C., regardless of the absolute value of ST.
[0031]
From this, in order to further investigate the reason why good characteristics can be obtained over the entire length of the coil by controlling the fluctuation of the rolling start temperature over the entire length of the coil to within 100 ° C., a sample in which a magnetic property defect occurred in the X part When the texture of 1/5 layer thickness of the decarburized annealed plate was measured, the random strength ratio of the {1241} <014> orientation was less than 3.0. On the other hand, when the texture of the 1/5 layer thickness of the decarburized annealed plate was measured for the sample in which the magnetic property defect occurred in the Z portion, the {1241} <014> orientation was very large and the maximum peak was not observed. It was.
[0032]
In general, the rolling start temperature ST is high at the tip of the hot-rolled coil, and becomes colder toward the tail end. And when rolling start temperature ST falls, precipitation of AlN in the middle of hot rolling will increase. Here, in order to properly control the inhibitor strength in order to obtain good magnetic properties, the hot-rolled sheet annealing temperature must be changed according to the precipitation state of AlN on the hot-rolled sheet. When hot-rolled sheet annealing is performed at a constant temperature up to the end, inhibitor suppressive power is relatively strong in the X part (coil tip), and growth during decarburization annealing of {1241} <014> oriented grains is suppressed. Since the inhibitor suppressive force is relatively weak at the Z portion (coil tail end portion), the {1241} <014> orientation grows to the extent that it covers the entire sample. Thus, according to the method of the present invention, both tend to have poor magnetic properties. However, if the fluctuation of the rolling start temperature ST over the entire length of the coil is within 100 ° C., the inhibitor strength over the entire length of the coil can be controlled to an appropriate state by the hot-rolled sheet annealing in the next process. It was found that deterioration was eliminated and a good product was obtained over the entire length.
[0033]
Furthermore, the inventors have studied a method for stably obtaining good characteristics over the entire length of the coil, and have found that it is effective to control the temperature rising rate during decarburization annealing. Experiment 2 shows the results of the study.
[0034]
Experiment 2
Three 220 mm-thick slabs having the component composition a in Table 1 were heated to a temperature of 1200 ° C. and hot-rolled to obtain 2.5 mm hot-rolled coils. At that time, the finish rolling start temperature (ST) was unified to 1045 ° C. in the X part and 950 ° C. in the Z part (the difference was 95 ° C.). These coils were subjected to hot-rolled sheet annealing at 925 ° C. for 30 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm at a temperature of 200 ° C. with a tandem rolling mill. Thereafter, degreasing treatment was performed, and decarburization annealing was performed at 850 ° C. for 120 seconds.
At that time, the temperature raising conditions for decarburization annealing were changed in the following three ways.
(1) Temperature rise from 600 ℃ to 750 ℃ at an average of 12 ℃ / sec.
(2) Temperature rise from 600 ℃ to 750 ℃ at an average of 20 ℃ / sec.
(3) Temperature rise from 600 ° C to 750 ° C at an average of 28 ° C / sec.
[0035]
After cold rolling and after decarburization annealing, samples were taken from the X part and Z part of each coil.
FIG. 6 shows the random strength ratio of the {1241} <014> orientation in the 1 / 5th layer thickness of the decarburized and annealed plate. The texture measurement method is the same as in Experiment 1. From FIG. 6, it can be seen that the faster the rate of temperature rise, the smaller the {1241} <014> orientation in the X portion and the more {1241} <014> orientation in the Z portion, and the greater the difference in strength in the coil longitudinal direction. I understand.
[0036]
In order to consider the reason why the texture of the decarburized annealed plate changed as shown in FIG. 6 depending on the heating rate, the collected cold-rolled plates (X and Z) were decarburized and annealed in the laboratory. The temperature rise rate is the above two conditions (1) and (3), and the cross-sectional structure of the sample after soaking at 850 ° C for 120 seconds and the sample immediately after reaching 850 ° C are extracted. It was. FIG. 7 shows the average grain size of the crystal grains of each sample. When the heating rate is 28 ° C / s, the particle size when reaching 850 ° C is almost the same between X and Z, but after 120 seconds of soaking, grain growth is remarkable in the Z part where the inhibitor's inhibitory power is weak. Is going on. On the other hand, when the heating rate is 12 ° C./s, a difference in grain growth has already occurred in the longitudinal direction when the temperature reaches 850 ° C. The diameter is large. However, if the particle size is compared again after 120 seconds of soaking, the longitudinal difference is reduced. This is presumably because the driving force for grain growth during soaking decreases when the grain size is large when the temperature reaches 850 ° C.
[0037]
From FIG. 6 and FIG. 7, it is possible to control the grain growth to the same extent over the entire coil length by slowing the temperature raising rate of the decarburization annealing, and as a result, more reliably { It has become clear that the intensity of the 1241} <014> orientation can be controlled within the proper range of the present invention.
[0038]
As described above, it is necessary to control the texture of the decarburized and annealed plate. To that end, it is necessary to comply with the following conditions.
(About ingredients)
C: 0.02wt% or more, 0.06wt% or less
C is a component necessary for improving the structure and stabilizing secondary recrystallization, and for that purpose, 0.02 wt% or more is necessary. However, if it exceeds 0.06 wt%, the fracture at the time of cold rolling increases, and the structure after decarburization annealing becomes too uniform, which is not suitable for the present invention, so 0.06 wt% or less.
Si: 2.0 wt% or more, 4.5 wt% or less
Si is an essential component for increasing electrical resistance and reducing iron loss. For this purpose, it is necessary to contain 2.0 wt% or more, but if it exceeds 4.5 wt%, the workability deteriorates. Since manufacturing and processing of products become extremely difficult, the range is 2.0 wt% to 4.5 wt%.
Mn: 0.03wt% or more, 2.5wt% or less
Mn is also a component that increases electrical resistance like Si, and is a necessary component because it improves hot workability during manufacturing. For this purpose, it is necessary to contain 0.03 wt% or more. However, if it exceeds 2.5 wt%, the gamma transformation is induced and the magnetic properties deteriorate, so 0.03 wt% or more, 2.5 wt% The following range.
[0039]
Al: 0.005 wt% or more, 0.030 wt% or less
Al needs to contain 0.005 wt% or more and 0.030 wt% or less as an inhibitor component. Al is combined with N to serve as an invitor as AlN. In particular, AlN is solid-dissolved during slab heating and finely precipitated in the temperature rising process of hot-rolled sheet annealing, thereby increasing the effect of suppressing the growth of primary recrystallized grains. However, when the Al content is less than 0.005 wt%, the amount of AlN that precipitates during the temperature rising process of hot-rolled sheet annealing is insufficient, and conversely, when it exceeds 0.030 wt%, the slab heating at 1260 ° C or less At this time, since it becomes difficult to dissolve AlN, the amount of AlN finely precipitated in the temperature rising process of hot-rolled sheet annealing is insufficient. Therefore, in order to effectively exhibit the effect as an inhibitor, the Al content is set to 0.005 wt% or more and 0.030 wt% or less.
N: 0.0030 wt% or more, 0.0100 or less
Since N forms AlN and functions as an inhibitor, it is necessary to contain 0.0030 wt% or more. However, if it exceeds 0.0100 wt%, it will gasify in steel and cause defects such as blistering, so it must be in the range of 0.0030 wt% or more and 0.0100 wt% or less.
[0040]
Other inhibitor components
Sb, Nb, Sn, Cr, Se, S or the like can be added as necessary to function as an inhibitor. In particular, Sb or Sn is effective because it has the effect of forming fine precipitates in hot rolling and increasing the precipitation nuclei of AlN in the temperature rising process of the next hot-rolled sheet annealing. In order to obtain such an action, it is necessary to add 0.001 wt% or more of these components. However, if it exceeds 0.30 wt%, the mechanical properties such as the bend characteristics of the product deteriorate, so the content is 0.001. It is preferable that the content is not less than wt% and not more than 0.30 wt%.
[0041]
(Hot rolling)
The slab adjusted to the above components is subjected to slab heating in accordance with a normal method, and is then formed into a hot rolled coil by hot rolling.
Slab heating temperature shall be 1260 ℃ or less. A low slab heating temperature is not only preferable for reducing energy costs, but also causes moderate non-uniformity in the precipitation state of the invitator components such as AlN, thereby reducing the non-uniformity of the particle size distribution after decarburization annealing. This is preferable in terms of promotion.
In recent years, a method of directly performing hot rolling after continuous casting without performing slab heating has been disclosed, but since this method can reduce the slab heating temperature, it can also be suitably implemented in the present invention.
Also, in order to obtain good magnetic properties over the entire length of the coil, the variation in the finish rolling start temperature of the hot rolling must be controlled within 100 ° C. over the entire length of the coil.
[0042]
(Hot rolled annealing)
The hot-rolled sheet annealing is preferably performed at 950 ° C or lower. The purpose of hot-rolled sheet annealing is to homogenize the structure of the hot-rolled sheet and to promote fine precipitation of the inhibitor, so it is generally performed at a high temperature of 1000 ° C or higher. Is not necessary, but rather harmful, so it should be done at very low temperatures. However, since it is indispensable to precipitate the inhibitor finely, it is not preferable to omit the hot-rolled sheet annealing or to perform it at less than 800 ° C.
[0043]
(Cold rolling)
Cold rolling is preferably performed at a temperature of 100 ° C. or higher with a tandem rolling mill. A tandem mill has a high strain rate and a short time between passes. Therefore, when the tandem mill is warm-rolled at a temperature of 100 ° C. or higher, non-uniform deformation is promoted. Non-uniform deformation during rolling promotes non-uniform growth of primary recrystallized grains during decarburization annealing. The non-uniformity of the grain size of the decarburized annealed plate is preferable because it corresponds to a moderate increase in the {1241} <014> orientation and leads to an improvement in the magnetic properties of the product.
[0044]
(Decarburization annealing, final finish annealing, coating)
After cold rolling, decarburization annealing is performed according to a conventional method, and then an annealing separator is applied and final finish annealing is performed.
In the temperature raising process of the release annealing, in order to obtain good magnetic characteristics over the entire length of the coil, it is preferable to set the temperature raising rate at 600 ° C. to 750 ° C. to 20 ° C./s or less.
After final finish annealing, if necessary, an insulating coating is applied and baked, and further flattened annealing is performed to obtain a product.
[0045]
【Example】
Example 1
Nine 200 mm-thick slabs having the component compositions e and f shown in Table 1 were each heated to a temperature of 1150 ° C. and hot-rolled to form 2.4 mm hot-rolled coils. The finishing rolling start temperature was controlled at 990 ° C. in the X part and 925 ° C. in the Z part. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm with a tandem rolling mill. At this time, the hot-rolled sheet annealing temperature was changed in three ways: 850 ° C., 940 ° C. and 1030 ° C., and the cold rolling temperature was changed in three ways: 60 ° C., 120 ° C. and 200 ° C. Thereafter, degreasing treatment was performed, decarburization annealing was performed at 830 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing. In addition, the temperature increase rate of 600-750 degreeC of the temperature rising process of decarburization annealing was controlled to 16 degreeC / s.
[0046]
After decarburization annealing, a part of the sample was taken and the texture of the 1 / 5th layer was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product.
From each product, cut out Epstein-sized test pieces along the rolling direction to obtain magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
[0047]
Tables 2 and 3 show the texture of the decarburized and annealed sheet and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂= Φ giving a maximum at 45 ° and the random intensity ratio of {1241} <014> orientation. In addition, the * mark was given to the remarks column for the sample whose {1241} <014> orientation had the maximum peak. In addition, the texture and magnetic measurement were performed by collecting samples from the front end (X portion), the vicinity of the center (Y portion), and the tail end (Z portion) in the coil longitudinal direction.
[0048]
[Table 2]

[0049]
[Table 3]

[0050]
As shown in Tables 2 and 3, the maximum peak of the texture of the decarburized annealed plate is φ₁= 90 °, Φ: 58-62 ° or -58--62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the product has good magnetic properties. Also, in order to control the texture of the decarburized annealed sheet as described above, it is extremely effective to set the hot-rolled sheet annealing temperature to 950 ° C or lower and perform cold rolling at 100 ° C or higher with a tandem rolling mill. I understand.
[0051]
(Example 2)
Six 200 mm-thick slabs having the component composition e shown in Table 1 were heated to a temperature of 1150 ° C. and then hot-rolled two by two under the following three conditions to form a 2.4 mm hot-rolled coil.
(A) X part finish rolling start temperature 980 ° C, Z part finish rolling start temperature 930 ° C,
(B) X part finish rolling start temperature 995 ° C, Z part finish rolling start temperature 905 ° C,
(C) X part finish rolling start temperature 1015 ° C, Z part finish rolling start temperature 880 ° C,
These coils were subjected to hot-rolled sheet annealing at 850 ° C. for 60 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm with a tandem rolling mill. Thereafter, degreasing treatment was performed, decarburization annealing was performed at 830 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing. The temperature raising conditions for decarburization annealing were changed in the following two ways.
(B) The heating rate from 600 to 750 ° C is 10 ° C / s,
(B) A heating rate of 600-750 ° C is 26 ° C / s,
[0052]
After decarburization annealing, a part of the sample was taken and the texture of the 1 / 5th layer was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied to obtain a baked product at 800 ° C. From each product, cut out Epstein-sized test pieces along the rolling direction to obtain magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
Table 4 shows the texture of the decarburized and annealed sheet and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂The value of Φ giving a maximum at = 45 ° and the random intensity ratio of the {1241} <014> orientation are shown. In addition, * was provided in the table | surface about the sample from which the {1241} <014> direction became the maximum peak. In addition, the texture and magnetic measurement were performed by collecting samples from positions corresponding to the X part, the Y part, and the Z part in the longitudinal direction of the hot rolled coil.
[0053]
[Table 4]

[0054]
As shown in Table 4, the maximum peak of the texture of the decarburized and annealed sheet is φ in the Bunge Euler angle display.₁= 90 °, Φ: 58-62 ° or -58--62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the product has good magnetic properties. In addition, in order to control the texture of the decarburized annealing plate as described above over the entire length of the coil, the variation in the hot rolling finish rolling start temperature is controlled within 100 ° C, and the decarburization annealing is increased. It can be seen that it is extremely effective to set the heating rate of 600 ° C. to 750 ° C. in the temperature process to 20 ° C./s or less.
[0055]
(Example 3)
Nine 250 mm-thick slabs each having a composition of g and h shown in Table 1 were heated to a temperature of 1220 ° C. and hot-rolled to form a 2.7 mm hot-rolled coil. The finishing rolling start temperature was controlled at 1020 ° C. in the X part and 940 ° C. in the Z part. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled by a first tandem rolling mill to a thickness of 1.6 mm at a temperature of 80 ° C, and intermediated at a temperature of 950 ° C. After annealing, it was pickled and cold rolled by a second tandem rolling mill to a thickness of 0.22 mm. At this time, the hot-rolled sheet annealing temperature was changed in three ways: 800 ° C., 900 ° C. and 1000 ° C., and the second cold rolling temperature was changed in three ways: 80 ° C., 150 ° C. and 250 ° C. Thereafter, degreasing treatment was performed, decarburization annealing was performed at 850 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing. In addition, the temperature increase rate of 600-750 degreeC of the temperature rising process of decarburization annealing was controlled to 16 degreeC / s.
After decarburization annealing, a part of the sample was taken and the texture of the 1 / 5th layer was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product.
From each product, cut out Epstein-sized test pieces along the rolling direction to obtain magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
[0056]
Tables 5 and 6 show the relationship between the texture of the decarburized annealing plate and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂= Φ giving a maximum at 45 ° and the random intensity ratio of {1241} <014> orientation. In addition, the * mark was given to the remarks column for the sample whose {1241} <014> orientation had the maximum peak. In addition, the texture and magnetic measurement were performed by collecting samples from the front end (X portion), the vicinity of the center (Y portion), and the tail end (Z portion) in the coil longitudinal direction.
[0057]
[Table 5]

[0058]
[Table 6]

[0059]
As shown in Tables 5 and 6, the maximum peak of the texture of the decarburized annealed plate is φ₁= 90 °, Φ: 58-62 ° or -58--62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the product has good magnetic properties. Also, in order to control the texture of the decarburized annealed sheet as described above, it is extremely effective to set the hot-rolled sheet annealing temperature to 950 ° C or lower and perform cold rolling at 100 ° C or higher with a tandem rolling mill. I understand.
[0060]
(Example 4)
Six 250 mm-thick slabs having the component composition of g shown in Table 1 were heated to a temperature of 1220 ° C. and then hot-rolled two by two under the following three conditions to form a 2.7 mm hot-rolled coil.
(D) X part finish rolling start temperature 1010 ° C, Z part finish rolling start temperature 950 ° C,
(E) X part finish rolling start temperature 1025 ° C, Z part finish rolling start temperature 935 ° C,
(F) X part finish rolling start temperature 1040 ° C, Z part finish rolling start temperature 910 ° C,
These coils were hot-rolled sheet annealed at 900 ° C for 60 seconds, pickled, cold-rolled by a first tandem rolling mill to a thickness of 1.6 mm at a temperature of 80 ° C, and 950 ° C After performing the intermediate annealing at the temperature, pickling and cold rolling with a second tandem rolling mill to a thickness of 0.22 mm. The second cold rolling temperature was 220 ° C. Thereafter, degreasing treatment was performed, decarburization annealing was performed at 850 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing. The temperature raising conditions for decarburization annealing were changed in the following two ways.
(C) The heating rate from 600 to 750 ° C is 9 ° C / s,
(D) The heating rate from 600 to 750 ° C is 27 ° C / s,
After decarburization annealing, a part of the sample was taken and the texture of the 1 / 5th layer was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
[0061]
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied to obtain a baked product at 800 ° C. From each product, cut out Epstein-sized test pieces along the rolling direction to obtain magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
Table 7 shows the texture of the decarburized and annealed sheet and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂The value of Φ giving a maximum at = 45 ° and the random intensity ratio of the {1241} <014> orientation are shown. In addition, * was provided in the table | surface about the sample from which the {1241} <014> direction became the maximum peak. In addition, the texture and magnetic measurement were performed by collecting samples from positions corresponding to the X part, the Y part, and the Z part in the longitudinal direction of the hot rolled coil.
[0062]
[Table 7]

[0063]
As shown in Table 7, the maximum peak of the texture of decarburized and annealed plates is φ in the Bunge Euler angle display.₁= 90 °, Φ: 58-62 ° or -58--62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the product has good magnetic properties. In addition, in order to control the texture of the decarburized annealing plate as described above over the entire length of the coil, the variation in the hot rolling finish rolling start temperature is controlled within 100 ° C, and the decarburization annealing is increased. It can be seen that it is extremely effective to set the heating rate of 600 ° C. to 750 ° C. in the temperature process to 20 ° C./s or less.
[0064]
【The invention's effect】
According to the present invention, it has become possible to stably produce a general-purpose unidirectional electrical steel sheet having good magnetic properties.
[Brief description of the drawings]
[Fig. 1] φ of texture of decarburized and annealed plate₁= 90 °, φ₂= It is a figure which shows random intensity ratio when (PHI) changes in a 45 degree cross section.
[Fig. 2] φ₁= 90 °, φ₂= Φ value giving maximum on 45 ° cross section and magnetic flux density B of product₈It is a figure which shows the relationship.
FIG. 3: {1241} <014> orientation random intensity ratio and product magnetic flux density B₈It is a figure which shows the relationship.
FIG. 4 is a diagram showing a relationship between a random strength ratio of {1241} <014> orientation of a decarburized and annealed plate and a coefficient of variation of particle diameter.
FIG. 5 is a diagram showing the influence of the difference in finish rolling start temperature over the entire coil length on the magnetic flux density of the product.
FIG. 6 is a diagram showing the influence of the temperature raising rate of decarburization annealing on the random strength ratio of {1241} <014> orientation in the 1 / 5th layer thickness of the decarburized annealing plate.
FIG. 7 is a diagram showing the average particle size of primary recrystallized grains at the time of reaching 850 ° C. and after soaking at 850 ° C. for 120 seconds in the decarburization annealing in the coil X part and the Z part.

Claims (3)

C: 0.02~0.06wt%, Si: 2.0 ~4.5 wt%, Mn: 0.03~2.5wt%, Al: 0.005 ~0.030 wt% and N: after heating the silicon steel slab containing 0.003 ~0.010wt%, subjected to hot rolling consisting of rough rolling and finish rolling, and then was subjected to hot rolled sheet annealing, a final sheet thickness by twice or more cold rolling sandwiching once or intermediate annealing, further, decarburization annealing, Next, in the method for producing a grain-oriented electrical steel sheet that is subjected to finish annealing after applying an annealing separator,
After setting the slab heating temperature to 1260 ℃ or less,
The hot rolling is performed by controlling the fluctuation of the finish rolling start temperature in the entire coil length to be within 100 ° C., and
By adjusting the hot-rolled sheet annealing temperature and changing the rolling temperature to cold rolling as tandem rolling, the texture in the plate thickness 1/5 layer area after decarburization annealing satisfies the following conditions A method for producing a grain-oriented electrical steel sheet, characterized by forming a structure.
The maximum peak orientation of the texture is Bunge's Euler angle display: φ ₁ = 90 ° ± 7.5 °, Φ: 58 ~ 62 ° or -58 ~ −62 °, φ ₂ = 45 ° ± 7.5 °
And the random intensity ratio of {1241} <014> is 3.0 or more. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein hot-rolled sheet annealing is performed at a temperature of 950 ° C or lower, and cold rolling is performed at a temperature of 100 ° C or higher with a tandem rolling mill. The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein a temperature increase rate of 600 to 750 ° C in an annealing process of decarburization annealing is set to 20 ° C / s or less.

Images