JP3895943B2 - Method for forming insulating film on grain-oriented electrical steel sheet - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、鋼板に対する付与張力が大きく方向性電磁鋼板の鉄損低減に有効に作用するほう酸アルミニウム皮膜を絶縁皮膜として形成する方法に関する。
【０００２】
【従来の技術】
方向性電磁鋼板は（１１０）［００１］方位を主方位とする結晶組織を有し、通常２％以上のＳｉを含有する鋼板であり、磁気鉄心材料として多用されており、特にエネルギーロスが少ない鉄損の低い材料が求められている。
Ｓｉ含有量が５％以下である場合、その磁気異方性の故に、鋼板に張力を付与することにより鉄損が低減するという性質がある。鋼板に半永久的に張力を付与するためには、鋼板表面に地鉄より熱膨張係数の小さい皮膜を高温で形成することが有効である。
【０００３】
方向性電磁鋼板の仕上げ焼鈍工程において、通常、自然に形成されるＭｇ2ＳｉＯ4もしくはＭｇ2ＳｉＯ4とＭｇＡｌ2Ｏ4を主体とする仕焼鈍皮膜は、焼鈍後の冷却によって、鋼板に対して０．５ｋｇｆ／ｍｍ2程度の張力を付与しており、ある程度の鉄損低減効果を有するが、その効果は十分ではない。
このため、仕上げ焼鈍後の方向性電磁鋼板の絶縁性を高めるために形成する絶縁皮膜によって、さらに張力を付与する努力がなされている。例えば、特開昭４８−３９３３８号公報に開示された、コロイド状シリカと燐酸塩を主体とする塗布液を焼き付けて得られる絶縁被膜は、さらに、０．５ｋｇｆ／ｍｍ2程度の張力を付与することができ、現行の市販の方向性電磁鋼板に広く用いられている。
【０００４】
発明者らが、方向性電磁鋼板の鉄損値に対する付与張力の影響を調査したところ、仕上げ焼鈍皮膜＋上記絶縁皮膜で得られる付与張力は、未だ不十分であり、より付与張力の大なる絶縁皮膜が形成できるならば、方向性電磁鋼板の鉄損値は、さらに低減し得ることが判明した。
そこで、発明者らは、新規なる絶縁被膜の開発に着手し、極めて付与張力の大きい絶縁被膜として、特開平６−６５７５４号公報、特開平６−６５７５５号公報等において、アルミナゾルとほう酸を混合した塗布液を塗布、焼き付けることによって得られるほう酸アルミニウム被膜（ＡｌxＢyＯ1.5(x-y)）を提案してきた。この絶縁皮膜は従来の絶縁皮膜の１．５〜２倍程度の皮膜張力を与える。
【０００５】
しかしながら、上記皮膜の開発を進めて行く過程で、用いるべきアルミナゾルの性状によって、得られる皮膜張力や造膜性、塗布液の安定性が異なることがわかった。例えば、結晶性の低いアルミナゾルは、ほう酸との反応性が良好であるため高い皮膜張力を得ることができる一方、造膜性が劣るために、必要な皮膜厚みを確保することが困難であり、さらには、ほう酸と混合した後の粘度安定性が悪く、ゲル化しやすいと言う性質を有する。
【０００６】
一方、結晶性の良好なベーマイト的なアルミナゾルは、造膜性が良好であり、かつ、ほう酸との混合の後の粘度安定性に優れる一方で、ホウ酸との反応性が劣り、得られる皮膜張力が不足する。
そこで、発明者らは、特開平１０−２８７９８４号公報において、結晶性の良好なアルミナゾルと、結晶性の低いアルミナゾルを混合して用いるという方法を開示した。しかしながら、この方法では、得られる皮膜張力、造膜性、粘度安定性のいずれも十分に満足のゆくものではなかった。
【０００７】
【発明が解決しようとする課題】
本発明は、方向性電磁鋼板に、ほう酸アルミニウム質の絶縁皮膜を形成するに際し、得られる皮膜張力を低下させることなしに、塗布液の粘度安定性等を確保する方法を開示するものである。
【０００８】
【課題を解決するための手段】
本発明においては、ほう酸とアルミナゾルを、Ａｌ：Ｂのモル比で１：１〜５：１の範囲で混合した分散液を、仕上げ焼鈍済みの方向性電磁鋼板に塗布し、５００℃以上で焼き付けて、ほう酸アルミニウム皮膜を形成するに当たり、アルミナゾルとして、１００℃乾燥後のＸ線回折測定におけるベーマイト（０２０）回折線の半価幅が３度以上で、かつ、アルミナゾル中の塩基性塩化アルミニウムおよび塩基性酢酸アルミニウム含有量が、Ａｌ量換算で、アルミナゾル中全Ａｌ量の３０％以下であるアルミナゾルを用いることを特徴とする方向性電磁鋼板の絶縁皮膜形成方法を要旨とする。
【０００９】
アルミナゾルとは、アルミナ水和物の微粒子から成るコロイドであり、コロイドの組成は、形式的に、Ａｌ2Ｏ3・ｘＨ2Ｏで表される。アルミナゾルの製法は、各種存在し、各製造法や製造条件によってコロイド粒子の結晶性は様々に変化する。アルミナゾルコロイド粒子の結晶性の比較的良好なものは、第１図に示すように、乾燥ゲルのＸ線回折パターンの幅が狭く、かつ、各回折ピークはγ−ＡｌＯＯＨ（ベーマイト、Ａｌ2Ｏ3・Ｈ2Ｏ）的の回折パターンに一致する。結晶性の低下とともに各回折ピークの幅は広がり、ほとんどピークの認められない場合もある。
【００１０】
したがって、Ｘ線回折のピーク幅は、アルミナゾル中のコロイド粒子の結晶性の評価に適している。また、結晶性の良好なものは、Ａｌ2Ｏ3・ｘＨ2Ｏで表現した場合のｘの値が１〜２程度にあり、結晶性の低下とともにｘの値が増大する。これは、結晶性の低下とともにコロイド粒子に結合する水が増えるからであると思われる。一般に１００℃程度の乾燥では、結晶水は解放されない。
【００１１】
発明者らは、ほう酸との反応性が良好で高い皮膜張力が得られる一方で、造膜性が劣り、かつ、ほう酸との混合の後の粘度安定性に劣る、結晶性の低いアルミナゾルの成分を調査した。その結果、当初、発明者らが用いていた低結晶性アルミナゾル中には、アルミナ水和物コロイド粒子に加えて、塩基性塩化アルミニウムや塩基性酢酸アルミニウムが多量に含有されていることが判明した。
【００１２】
塩基性塩の存在は、以下のようにして確認した。アルミナゾルコロイド粒子は数百ｎｍの大きさであるのに対し、塩基性塩は水溶液中で重合度の低いポリアルミニウムカチオン（数ｎｍ）と酸からなる塩として存在する故、両者は遠心分離と濾過により分離できる。
そこで、当初、発明者らが用いていた低結晶性アルミナゾルにつき、１８００ｒｐｍで１時間の遠心分離を施し、沈殿物および濾液それぞれにつきＡｌ量を調べたところ、全Ａｌ量の内、コロイドとして沈降した量が６０％、上澄み中に残存した量が４０％であった。さらに、上澄み中の陰イオンを分析したところ、上澄み中Ａｌ量に対し１／２〜１／３等量の塩素イオンや酢酸イオンを認めた。
【００１３】
したがって、上澄み中のＡｌは塩基性塩化アルミニウムや塩基性酢酸アルミニウムとして存在していることが判明した。よって、このアルミナゾルの組成は、Ａｌ換算で６０％がコロイド、４０％が塩基性アルミニウム塩であったといえる。当初、発明者らが用いていたアルミナゾル中に多量のこれら塩基性アルミニウム塩が含有していた理由は定かではないが、アルミナゾルの製造法に起因するものと思われる。
【００１４】
次ぎに、各種塩基性アルミニウム塩単体を準備し、その水溶液を作成して、ほう酸を添加した。その結果、塩基性塩化アルミニウムと塩基性酢酸アルミニウムの場合は、添加攪拌中に水溶液がゲル化したが、塩基性硝酸アルミニウム等、他の塩基性アルミニウム塩の場合では、長時間放置してもゲル化が起こらなかった。
【００１５】
上記検討結果より、当初、発明者らが用いていた低結晶性アルミナゾルが、ほう酸との混合後に、液の粘度安定性の点で劣る理由は、コロイド粒子の結晶性が低いことにあるのではなく、たまたま多量に含有されていた塩基性塩化アルミニウムや塩基性酢酸アルミニウムの存在によるものと考えられた。
上記予想を確認するために、第１表に示すように、塩基性塩化アルミニウムもしくは塩基性酢酸アルミニウムの含有量がＡｌ換算で全Ａｌ量の４０％であるアルミナゾル、限外濾過により塩基性塩化アルミニウムや塩基性酢酸アルミニウム含有量をＡｌ換算で全Ａｌ量の３０％もしくは２０％に減少させたもの、さらに、塩基性硝酸アルミニウムをＡｌ換算で全Ａｌ量の４０％含有するアルミナゾルを用意した。いずれも、ベーマイト（０２０）回折線の半価幅が３度以上の低結晶性アルミナゾルである。これらアルミナゾルにＡｌ：Ｂのモル比が２：１となるようほう酸を添加し、２４時間放置後の液のゲル化の有無を観察した。
【００１６】
【表１】
第１表に示したように、塩基性塩化アルミニウムや塩基性酢酸アルミニウムをＡｌ換算で全Ａｌ量の４０％含有するアルミナゾルを用いた場合には、２４時間後に液がゲル化してしまうが、これらの塩基性アルミニウム塩をＡｌ換算で全Ａｌ量の３０％以下に減らしたものはゲル化が起こっていない。
また、塩基性硝酸アルミニウムを含有するゾルは、その含有量がＡｌ換算で全Ａｌ量の４０％であっても、ゲル化が起こっていない。
【００１８】
したがって、塩基性塩化アルミニウムおよび塩基性酢酸アルミニウム含有量がＡｌ換算で全Ａｌ量の３０％以下の低結晶性アルミナゾルを用いた塗布液は、粘度安定性の点で問題なく使用できるといえる。
次ぎに、前記塗布液を鋼板に塗布乾燥し、塗布液の造膜性を調査した。造膜性が悪い場合には、塗布量の増大とともに乾燥膜が剥がれやすくなるので、５ｇ／ｍ2塗布した場合に剥離が起こるか否かをもって造膜性の判定基準とした。
【００１９】
表１に示すように、塩基性塩化アルミニウムや塩基性酢酸アルミニウムを、Ａｌ換算で全Ａｌ量の４０％含有するアルミナゾルを用いた場合には、５ｇ／ｍ2塗布時に剥離が起こるが，これらの塩基性アルミニウム塩を、Ａｌ換算で全Ａｌ量の３０％以下に減らしたものは、剥離が起こっていない。
また、塩基性硝酸アルミニウムを含有するゾルは、その含有量がＡｌ換算で全Ａｌ量の４０％であっても、剥離が起こっていない。
【００２０】
したがって、当初、発明者らが用いていた低結晶性アルミナゾルとほう酸を混合した塗布液の造膜性が劣る理由は、コロイド粒子の結晶性が低いことにあるのではなく、たまたま多量に含有されていた塩基性塩化アルミニウムや塩基性酢酸アルミニウムの存在によるものと言える。
以上のように、ほう酸との反応性が良好で高い皮膜張力が得やすい低結晶性アルミナゾルの欠点であった、ほう酸との混合後のゲル化のしやすさ、および、低い造膜性の原因は、アルミナゾルの結晶性自体にあるのではなく、当初、発明者らの用いていたアルミナゾルに、たまたま多量に含有されていた塩基性塩化アルミニウムや塩基性酢酸アルミニウムにあると言える。
【００２１】
したがって、これら２種の塩基性アルミニウム塩含有量を制御した低結晶性アルミナゾルを用いるならば、結晶性の良好なアルミナゾルと混合しなくとも、すなわち、得られる皮膜張力を犠牲にしなくとも、良好な液安定性や造膜性を得ることができる。
つづいて、アルミナゾルの結晶性と得られる皮膜張力の関係について述べる。特開平１０−２８７９８４号公報に開示したように、結晶水含有量の比較的良好な、すなわち、結晶性の低いアルミナゾルは、ほう酸との反応性に富み、高い皮膜張力を得ることができる。同公報においては、結晶性の指標として、１００℃で乾燥した場合の結晶水含有量（Ａｌ2Ｏ3・ｘＨ2Ｏで表記した場合のｘの値）を用いた。この指標は測定誤差を含むことが判明したため、本発明では、結晶水含有量として、１００℃乾燥後のＸ線回折におけるベーマイト（０２０）回折線の半価幅を採用することとした。
【００２２】
第２図に、本発明における回折線半価幅の定義を示した。第１図に示したように、ベーマイト（０２０）回折線は、最も強い反射強度を与える回折線であり、格子間隔で約０．６ｎｍ付近にあり、ＣｕＫα線を用いた場合には、回折角２θ＝１４度付近となる。
各種アルミナゾルを用意し、塩基性塩化アルミニウムと塩基性酢酸アルミニウムの合計の含有量を、Ａｌ換算で全Ａｌ量の４０％以下に制御した上で、ほう酸と混合し、鋼板に塗布し８５０℃で焼き付けて得られる皮膜張力を測定した結果は実施例で詳細に述べるが、ベーマイト（０２０）回折線の回折幅が３度以上のアルミナゾルを用いた場合には高い皮膜張力が得られる。
【００２３】
【発明の実施の形態】
本発明の方向性電磁鋼板の絶縁皮膜形成方法は、結晶性の低いアルミナゾルとほう酸との混合液を、仕上げ焼鈍（二次再結晶焼鈍）が完了した方向性電磁鋼板に塗布し、焼き付けて、ほう酸アルミニウムからなる絶縁皮膜を形成するものである。結晶性の低いアルミナゾルとは、１００℃で乾燥した場合のＸ線回折におけるベーマイト（０２０）回折線の半価幅が３度以上のアルミナゾルである。
【００２４】
３度以上の半価幅を有するアルミナゾルは、ほとんど（０２０）回折線が認められない、いわゆる無定形ないし非晶質アルミナゾルを含め、ほう酸と混合して焼き付けることにより、高い皮膜張力を鋼板に付与することができる。
ただし、上記アルミナゾル中の塩基性塩化アルミニウムや塩基性酢酸アルミニウムの含有量は、Ａｌ換算で、アルミナゾル中全Ａｌ量の３０％以下でなければならない。これら塩基性アルミニウム塩含有量が３０％を越えると、ほう酸との混合時の液の粘度安定性が低下しゲル化しやすくなり、また、造膜性が劣化して必要な皮膜厚みを達成できなくなる。
【００２５】
市販のアルミナゾルの中には、これら塩基性アルミニウム塩を３０％を越えて含有するものがあるが、その場合には、限外濾過等により、塩基性アルミニウム塩の含有量を、Ａｌ換算で全Ａｌ量の３０％以下に減少させて使用することができる。
塗布液中のアルミナゾルとほう酸の混合比は、Ａｌ：Ｂのモル比で１：１〜５：１の範囲とする。この範囲外では、得られる皮膜張力が著しく低下し、特に、ほう酸が過剰の場合には、未反応のＢ2Ｏ3が生成し、耐水性等が劣化する。
【００２６】
本発明の塗布液には、上記アルミナゾルとほう酸に、必要に応じ添加物を加えてもよい。例えば、酸化珪素前駆体化合物、遷移金属化合物、アルカリ、あるいは、アルカリ金属化合物、希土類元素化合物、無機酸、有機酸，アンモニア等を必要量添加することができる。
上記塗布液を、５％以下のＳｉを含有する仕上げ焼鈍済みの方向性電磁鋼板に、ロールコート法、デップ法、スプレー法、あるいは、電気泳動法など、公知の手段により塗布する。塗布法は、特に限定されず、液性状等に応じて最適な方法を選択すればよい。
【００２７】
本発明で言うところの仕上げ焼鈍済みの方向性電磁鋼板には、（１）一般的に公知の製造法、すなわち、ＭｇＯを主体とする焼鈍分離剤を塗布して仕上げ焼鈍を行うことによって生ずるＭｇ2ＳｉＯ4もしくはＭｇ2ＳｉＯ4とＭｇＡｌ2Ｏ4を主体とする仕焼鈍皮膜を有するものと、（２）これら仕上げ焼鈍皮膜のない方向性電磁鋼板、の２種類があり、本発明は、いずれの方向性電磁鋼板にも適用できる。
【００２８】
上記（２）の方向性電磁鋼板の製造方法としては、（ａ）ＭｇＯ焼鈍分離剤中に仕上げ焼鈍皮膜形成を阻害する添加物を含有させたり（特開平０５−２９９２２８号公報）、（ｂ）ＭｇＯに代えてＡｌ2Ｏ3等、不活性な酸化物等を主体とする焼鈍分離剤として用いることにより意図的に仕上げ焼鈍皮膜を形成させない方法、（ｃ）通常の仕上げ焼鈍を行った後に仕上げ焼鈍皮膜を酸洗等で除去する方法、がある。
【００２９】
上記（ｂ）の方法では、特開平８−３６４８号公報に開示したように、焼鈍分離剤中のアルカリ金属元素濃度を制御することにより、仕上げ焼鈍皮膜がないばかりでなく表面が平滑である方向性電磁鋼板が得られる。また、（ｃ）の製造法を採用した後、化学研磨、電解研磨によって、（ｂ）と同様の表面が平滑な方向性電磁鋼板が得られる。本発明の絶縁皮膜は、特に表面が平滑な方向性電磁鋼板の鉄損値を著しく低減させることに効果的である。
【００３０】
一般的な製造法によって製造した、すなわち、仕上げ焼鈍皮膜を有する方向性電磁鋼板の場合、Ｍｇ2ＳｉＯ4もしくはＭｇ2ＳｉＯ4とＭｇＡｌ2Ｏ4を主体とする仕焼鈍皮膜の上に、直接、本発明の塗布液を塗布焼き付けても特段問題はないが、本発明の塗布液を焼き付ける前に、燐酸塩とコロイダルシリカを主体とする従来の絶縁皮膜をあらかじめ形成すると、極めて耐食性の高い絶縁皮膜となる。
【００３１】
仕上げ焼鈍皮膜の無い方向性電磁鋼板に、本発明の塗布液を適用する場合には、特開平０６−１８４７６２号公報に開示したように、０．００１μｍ以上の膜厚を有するＳｉＯ2の膜をあらかじめ形成させることによって、鋼板と絶縁皮膜との間の良好な密着性を得ることができる。
ＳｉＯ2膜の形成方法には、方向性電磁鋼板の弱酸化性雰囲気中焼鈍により、ＳｉＯ2外部酸化膜を形成する方法や、ＣＶＤやＰＶＤ等のドライコーティングにより、ＳｉＯ2膜を形成する方法がある。
【００３２】
いずれの方向性電磁鋼板においても、レーザー照射による点列状の局所歪み導入や溝形成等の、いわゆる、磁区制御と併用すれば、本発明の絶縁皮膜による高い付与張力により、極めて低い鉄損値を有する方向性電磁鋼板が得られる。
本発明の塗布液を塗布した方向性電磁鋼板は、５００℃〜１２００℃で焼付を行う。５００℃未満の場合、アルミナ水和物の脱水が不十分であり、ほう酸アルミニウムが形成し難い。また、１２００℃以上の焼付温度は、特に大きな不都合はないものの、経済的ではない。
【００３３】
より好ましくは、７００〜１２００℃であり、この温度範囲では、ほう酸アルミニウムの形成が容易に進行し、高い皮膜張力が得られる。
焼付の雰囲気は、一般的には限定されないが、仕上げ焼鈍皮膜がない方向性電磁鋼板に適用する場合には、絶縁皮膜と鋼板との間の界面の酸化を防止するために、非酸化性雰囲気ないし水素を含有する雰囲気を採用することが望ましい。
【００３４】
【実施例】
（実施例１）
第２表に示すように、結晶性と塩基性アルミニウム塩の種類および含有量の異なる各種アルミナゾルとほう酸を混合し、必要に応じて純水を添加して塗布液を準備した。通常の製造法により製造した仕上げ焼鈍皮膜を有する板厚０．２３ｍｍの方向性電磁鋼板を用意し、第２表の塗布液を、片面あたり５ｇ／ｍ2塗布し、８５０℃で３０秒間焼き付けた。塗布液中のＡｌ：Ｂのモル比は２：１である。その際の塗布液の安定性、造膜性、絶縁皮膜形成後の磁気特性と絶縁皮膜張力を第２表に示した。
【００３５】
【表２】
塗布液安定性は、２４時間放置後のゲル化の有無、造膜性は、乾燥後の皮膜の剥離の有無、皮膜張力は、片面を保護しつつアルカリにより絶縁皮膜を除去した場合の鋼板のそりから算出した。
第２表に示したように、塩基性塩化アルミニウムおよび塩基性酢酸アルミニウムの含有量が、Ａｌ換算でアルミナゾル中全Ａｌ量の３０％を越える塗布液（Ｎｏ．５および８）では、塗布液の粘度が不安定であり、かつ、造膜性が悪く、乾燥後に皮膜の剥離が起こっているが、上記両塩基性アルミニウム塩が３０％以下の塗布液では、そのような現象が認められない。
【００３７】
さらに、乾燥後の（０２０）回折線半価幅が３度以上のアルミナゾルを用いた場合には、そうでない場合に比較して、得られる皮膜張力が大きく、鉄損値のより低い方向性電磁鋼板となっている。
（実施例２）
通常の製造法により製造した仕上げ焼鈍皮膜を有する板厚０．２３ｍｍの方向性電磁鋼板を用意し、これに、従来のコリダルシリカと燐酸塩を主体とするコーティング液を、５ｇ／ｍ2塗布し８５０℃で６０秒焼き付けたもの、および、コロイダルシリカと燐酸塩を１ｇ／ｍ2塗布して６００℃で３０秒焼き付けた後、さらに、ほう酸とアルミナゾルからなる塗布液を、さらに、４ｇ／ｍ2塗布して８５０℃で６０秒焼き付けたものを用意した。
【００３８】
ほう酸とアルミナゾルからなる塗布液は２種類用意した。すなわち、結晶性の良好なアルミナゾルと低結晶性アルミナゾルを混合したもの、および、低結晶性アルミナゾルのみを用いたものである。いずれのアルミナゾルも、塩基性塩化アルミニウムや塩基性酢酸アルミニウムの含有量は、Ａｌ換算で全Ａｌ量の３０％以下である。
【００３９】
得られた方向性電磁鋼板の磁気特性、絶縁皮膜張力、耐錆性を調査した。耐錆性は、５０℃、５％食塩水を５時間噴霧した後の発錆の有無により判定した。結果を第３表に示す。
コロイダルシリカと燐酸塩を主体とする従来のコーティング液を焼き付けた上に、本発明のコーティング液を焼き付けた方向性電磁鋼板は、従来のコーティング液のみを用いた従来の方向性電磁鋼板に劣らない耐錆性を有し、かつ、鉄損値が著しく改善されている。
【００４０】
また、低結晶性アルミナゾルとほう酸からなる塗布液は、従来のコロイダルシリカと燐酸塩を主体とする塗布液や、結晶性良好なアルミナゾルと低結晶性アルミナゾルを混合したうえでほう酸を混入させた場合に比較して、得られる皮膜張力が大きく、その結果、低い鉄損値を与えている。
【００４１】
【表３】
（実施例３）
特開平８−３６４８号公報に従って仕上げ焼鈍を行った板厚０．２２ｍｍの仕上げ焼鈍皮膜が無く、かつ、表面が平滑である方向性電磁鋼板を用意した。溝付歯車ロールにより、これに、深さ２０μｍ、幅１００μｍの溝を、５ｍｍ間隔で圧延方向にほぼ垂直の方向に形成した。一部の方向性電磁鋼板には、還元性雰囲気中の焼鈍により、１０ｎｍの厚さでＳｉＯ2膜を形成した。
【００４３】
これに、従来のコロイダルシリカと燐酸塩を主体とするコーティング液を５ｇ／ｍ2塗布し８５０℃で６０秒焼き付けたもの、および、ほう酸とアルミナゾルからなる塗布液を５ｇ／ｍ2塗布して８５０℃で６０秒焼き付けたものを用意した。
ほう酸とアルミナゾルからなる塗布液は２種類用意した。すなわち、結晶性の良好なアルミナゾルと低結晶性アルミナゾルを混合したもの、および、低結晶性アルミナゾルのみを用いたものである。
【００４４】
いずれのアルミナゾルも、塩基性塩化アルミニウムや塩基性酢酸アルミニウムの含有量は、Ａｌ換算で全Ａｌ量の３０％以下である。
得られた方向性電磁鋼板の磁気特性、絶縁皮膜張力、密着性を調査した。皮膜密着性は、曲率半径１０ｍｍの丸棒に鋼板を巻き付けた場合の皮膜の剥離の有無によって判定した。第４表に示すように、ＳｉＯ2膜を形成することにより、絶縁皮膜の密着性が良好となり、また、低結晶性アルミナゾルとほう酸からなる塗布液は、従来のコロイダルシリカと燐酸塩を主体とする塗布液や、結晶性良好なアルミナゾルと低結晶性アルミナゾルを混合したうえでほう酸を混入させた場合に比較して、得られる皮膜張力が大きく、その結果、極めて低い鉄損値を与えている。
【００４５】
【表４】
【発明の効果】
本発明によって、従来の絶縁皮膜に比較して格段に大きい張力を方向性電磁鋼板に付与することができるほう酸アルミニウム質の絶縁皮膜を、粘度変化の少ない塗布液を用いて密着性良好に形成することができ、方向性電磁鋼板の鉄損を著しく改善できる。
【図面の簡単な説明】
【図１】１００℃で乾燥したアルミナゾルのＸ線回折パターン（ＣｕＫα線使用）を示す図である。
【図２】Ｘ線回折線の半価幅の定義を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming an aluminum borate film as an insulating film that has a large applied tension to a steel sheet and effectively acts to reduce iron loss of a grain-oriented electrical steel sheet.
[0002]
[Prior art]
A grain-oriented electrical steel sheet is a steel sheet having a crystal structure with the (110) [001] orientation as the main orientation and usually containing 2% or more of Si, and is often used as a magnetic iron core material, with particularly low energy loss. There is a need for materials with low iron loss.
When the Si content is 5% or less, due to the magnetic anisotropy, there is a property that iron loss is reduced by applying tension to the steel sheet. In order to apply a semi-permanent tension to the steel sheet, it is effective to form a film having a smaller thermal expansion coefficient than that of the ground iron at a high temperature on the steel sheet surface.
[0003]
In the finish annealing process of grain-oriented electrical steel sheets, normally, naturally formed Mg 2 SiO 4 or a finish annealing film mainly composed of Mg 2 SiO 4 and MgAl 2 O 4 is applied to the steel sheet by cooling after annealing. Although a tension of about 0.5 kgf / mm 2 is applied and the iron loss is reduced to some extent, the effect is not sufficient.
For this reason, efforts have been made to further apply tension with an insulating film formed to enhance the insulation of the grain-oriented electrical steel sheet after finish annealing. For example, the insulating coating obtained by baking a coating solution mainly composed of colloidal silica and phosphate disclosed in JP-A-48-39338 further imparts a tension of about 0.5 kgf / mm 2. It is widely used in current commercially available grain-oriented electrical steel sheets.
[0004]
When the inventors investigated the effect of the applied tension on the iron loss value of the grain-oriented electrical steel sheet, the applied tension obtained with the finish annealed film + the above insulating film is still insufficient, and the insulation with a higher applied tension. It was found that if the film can be formed, the iron loss value of the grain-oriented electrical steel sheet can be further reduced.
Therefore, the inventors started the development of a new insulating coating, and mixed an alumina sol and boric acid in an insulating coating having a very large applied tension in JP-A-6-65754, JP-A-6-65555, etc. applying the coating solution has been proposed aluminum borate coating film obtained by baking (Al x B y O 1.5 ( xy)). This insulating film gives a film tension about 1.5 to 2 times that of the conventional insulating film.
[0005]
However, in the course of proceeding with the development of the film, it was found that the film tension, film-forming properties, and coating solution stability obtained differ depending on the properties of the alumina sol to be used. For example, alumina sol with low crystallinity has good reactivity with boric acid, so that high film tension can be obtained, while film forming property is inferior, so it is difficult to ensure the required film thickness, Furthermore, it has the property that the viscosity stability after mixing with boric acid is poor and gelation is likely.
[0006]
On the other hand, boehmite-like alumina sol with good crystallinity has good film-forming properties and excellent viscosity stability after mixing with boric acid, but has poor reactivity with boric acid, resulting in a film obtained. Insufficient tension.
In view of this, the inventors disclosed in JP-A-10-287984 a method in which an alumina sol with good crystallinity and an alumina sol with low crystallinity are mixed and used. However, with this method, none of the obtained film tension, film-forming property, and viscosity stability are sufficiently satisfactory.
[0007]
[Problems to be solved by the invention]
The present invention discloses a method for ensuring the viscosity stability and the like of a coating solution without lowering the film tension obtained when forming an aluminum borate insulating film on a grain-oriented electrical steel sheet.
[0008]
[Means for Solving the Problems]
In the present invention, a dispersion obtained by mixing boric acid and alumina sol in a molar ratio of Al: B in the range of 1: 1 to 5: 1 is applied to a directional electrical steel sheet that has been subjected to finish annealing, and baked at 500 ° C. or higher. In forming the aluminum borate film, the half-width of boehmite (020) diffraction line in an X-ray diffraction measurement after drying at 100 ° C. is 3 degrees or more as the alumina sol, and the basic aluminum chloride and the base in the alumina sol sexual aluminum acetate content, of Al content in terms, and gist insulating film forming method of the grain-oriented electrical steel sheet characterized by using an alumina sol is 30% or less of the total Al content in the alumina sol.
[0009]
Alumina sol is a colloid composed of fine particles of alumina hydrate, and the composition of the colloid is formally expressed as Al 2 O 3 .xH 2 O. There are various methods for producing alumina sol, and the crystallinity of colloidal particles varies depending on each production method and production conditions. As shown in FIG. 1, the alumina sol colloidal particles having relatively good crystallinity have a narrow width of the X-ray diffraction pattern of the dried gel, and each diffraction peak has γ-AlOOH (boehmite, Al 2 O 3 It matches the diffraction pattern of (H 2 O). As the crystallinity decreases, the width of each diffraction peak increases, and there are cases where almost no peak is observed.
[0010]
Therefore, the peak width of X-ray diffraction is suitable for evaluating the crystallinity of colloidal particles in alumina sol. In addition, for those having good crystallinity, the value of x when expressed by Al 2 O 3 .xH 2 O is about 1 to 2, and the value of x increases as the crystallinity decreases. This seems to be because water that binds to the colloidal particles increases as the crystallinity decreases. Generally, crystallization water is not released by drying at about 100 ° C.
[0011]
The inventors have a low crystallinity component of alumina sol that has good reactivity with boric acid and high film tension, but poor film-forming property and poor viscosity stability after mixing with boric acid. investigated. As a result, it was initially found that the low crystalline alumina sol used by the inventors contained a large amount of basic aluminum chloride and basic aluminum acetate in addition to alumina hydrate colloidal particles. .
[0012]
The presence of the basic salt was confirmed as follows. Alumina sol colloidal particles are several hundreds of nanometers in size, while basic salts exist in the aqueous solution as low-polymerization polyaluminum cations (several nm) and acid salts. Can be separated.
Therefore, initially, the low crystalline alumina sol used by the inventors was centrifuged at 1800 rpm for 1 hour, and when the amount of Al was examined for each precipitate and filtrate, it settled as a colloid out of the total amount of Al. The amount was 60%, and the amount remaining in the supernatant was 40%. Furthermore, when the anion in the supernatant was analyzed, chlorine ions and acetate ions in an amount equivalent to 1/2 to 1/3 of the amount of Al in the supernatant were recognized.
[0013]
Therefore, it was found that Al in the supernatant was present as basic aluminum chloride or basic aluminum acetate. Therefore, it can be said that the composition of this alumina sol was 60% colloid and 40% basic aluminum salt in terms of Al. The reason why a large amount of these basic aluminum salts were contained in the alumina sol used by the inventors at the beginning is not clear, but it seems to be due to the production method of the alumina sol.
[0014]
Next, various basic aluminum salt simple substance was prepared, the aqueous solution was created, and the boric acid was added. As a result, in the case of basic aluminum chloride and basic aluminum acetate, the aqueous solution gelled during the addition and stirring. However, in the case of other basic aluminum salts such as basic aluminum nitrate, Did not happen.
[0015]
From the above examination results, the reason why the low crystalline alumina sol used by the inventors at the beginning is inferior in the viscosity stability of the liquid after mixing with boric acid is that the crystallinity of the colloidal particles is low. It was thought that this was due to the presence of basic aluminum chloride or basic aluminum acetate which happened to be contained in large amounts.
In order to confirm the above prediction, as shown in Table 1, alumina sol in which the content of basic aluminum chloride or basic aluminum acetate is 40% of the total Al amount in terms of Al, basic aluminum chloride by ultrafiltration In addition, an alumina sol was prepared in which the basic aluminum acetate content was reduced to 30% or 20% of the total Al content in terms of Al, and further, the basic aluminum nitrate contained 40% of the total Al content in terms of Al. Both are low crystalline alumina sols having a half width of boehmite (020) diffraction line of 3 degrees or more. Boric acid was added to these alumina sols so that the molar ratio of Al: B was 2: 1, and the presence or absence of gelation of the liquid after being allowed to stand for 24 hours was observed.
[0016]
[Table 1]
As shown in Table 1, when an alumina sol containing 40% of the total amount of Al in terms of Al as basic aluminum chloride or basic aluminum acetate is used, the solution gels after 24 hours. No gelation occurred when the basic aluminum salt was reduced to 30% or less of the total Al content in terms of Al.
Further, the sol containing basic aluminum nitrate does not cause gelation even when the content is 40% of the total Al content in terms of Al.
[0018]
Therefore, it can be said that a coating solution using a low crystalline alumina sol having a basic aluminum chloride content and a basic aluminum acetate content of 30% or less in terms of Al in terms of Al can be used without any problem in terms of viscosity stability.
Next, the said coating liquid was apply | coated and dried on the steel plate, and the film forming property of the coating liquid was investigated. When the film-forming property is poor, the dry film easily peels off as the coating amount increases. Therefore, whether or not peeling occurs when applied at 5 g / m 2 was used as a criterion for determining the film-forming property.
[0019]
As shown in Table 1, when an alumina sol containing 40% of the total amount of Al in terms of Al is used as basic aluminum chloride or basic aluminum acetate, peeling occurs when 5 g / m 2 is applied. No peeling occurred when the basic aluminum salt was reduced to 30% or less of the total Al content in terms of Al.
Further, the sol containing basic aluminum nitrate does not peel even when the content is 40% of the total Al amount in terms of Al.
[0020]
Therefore, the reason why the film forming property of the coating solution in which boric acid is mixed with the low crystalline alumina sol used by the inventors is inferior is not because the crystallinity of the colloidal particles is low. This can be attributed to the presence of basic aluminum chloride and basic aluminum acetate.
As described above, the low crystallinity alumina sol has good reactivity with boric acid and is easy to obtain high film tension. Ease of gelation after mixing with boric acid and cause of low film-forming property Is not in the crystallinity of the alumina sol itself, but can be said to be in the basic aluminum chloride or the basic aluminum acetate which happens to be contained in a large amount in the alumina sol used by the inventors at the beginning.
[0021]
Therefore, if a low crystalline alumina sol having a controlled content of these two basic aluminum salts is used, the low crystalline alumina sol is good without being mixed with an alumina sol having good crystallinity, that is, without sacrificing the obtained film tension. Liquid stability and film-forming property can be obtained.
Next, the relationship between the crystallinity of alumina sol and the resulting film tension will be described. As disclosed in Japanese Patent Application Laid-Open No. 10-287984, an alumina sol having a relatively good crystallization water content, that is, low crystallinity, is rich in reactivity with boric acid and can obtain a high film tension. In this publication, the content of water of crystallization when dried at 100 ° C. (value of x when expressed as Al 2 O 3 .xH 2 O) was used as an index of crystallinity. Since this index was found to include measurement errors, in the present invention, the half-value width of the boehmite (020) diffraction line in X-ray diffraction after drying at 100 ° C. was adopted as the crystallization water content.
[0022]
FIG. 2 shows the definition of the half-width of the diffraction line in the present invention. As shown in FIG. 1, the boehmite (020) diffraction line is the diffraction line that gives the strongest reflection intensity, and is in the vicinity of about 0.6 nm in the lattice spacing. When the CuKα line is used, the diffraction angle 2θ = around 14 degrees.
Various alumina sols were prepared, and the total content of basic aluminum chloride and basic aluminum acetate was controlled to 40% or less of the total Al amount in terms of Al, mixed with boric acid, applied to a steel plate, and applied at 850 ° C. The results of measuring the film tension obtained by baking are described in detail in Examples, but a high film tension is obtained when an alumina sol having a boehmite (020) diffraction line diffraction width of 3 degrees or more is used.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
In the method for forming an insulating film of a grain-oriented electrical steel sheet of the present invention, a mixed liquid of alumina sol and boric acid having low crystallinity is applied to a grain-oriented electrical steel sheet that has been subjected to finish annealing (secondary recrystallization annealing), and baked. An insulating film made of aluminum borate is formed. An alumina sol having low crystallinity is an alumina sol in which the half width of boehmite (020) diffraction line in X-ray diffraction when dried at 100 ° C. is 3 degrees or more.
[0024]
Alumina sol with a half width of 3 degrees or more, including so-called amorphous or amorphous alumina sol, in which almost no (020) diffraction line is observed, is mixed with boric acid and baked to give high film tension to the steel sheet. can do.
However, the content of basic aluminum chloride or basic aluminum acetate in the alumina sol must be 30% or less of the total amount of Al in the alumina sol in terms of Al. If the content of these basic aluminum salts exceeds 30%, the viscosity stability of the liquid at the time of mixing with boric acid is lowered and the gel is easily gelled, and the film forming property is deteriorated so that the required film thickness cannot be achieved. .
[0025]
Some commercially available alumina sols contain more than 30% of these basic aluminum salts. In that case, the content of the basic aluminum salt is completely reduced in terms of Al by ultrafiltration or the like. It can be used by reducing it to 30% or less of the amount of Al.
The mixing ratio of alumina sol and boric acid in the coating solution is in the range of 1: 1 to 5: 1 in terms of a molar ratio of Al: B. Outside this range, the resulting film tension is remarkably reduced. In particular, when boric acid is excessive, unreacted B 2 O 3 is formed, and the water resistance and the like deteriorate.
[0026]
If necessary, additives may be added to the above-mentioned alumina sol and boric acid in the coating solution of the present invention. For example, a necessary amount of a silicon oxide precursor compound, a transition metal compound, an alkali, or an alkali metal compound, a rare earth element compound, an inorganic acid, an organic acid, ammonia, or the like can be added.
The coating solution is applied to a directional magnetic steel sheet that has been annealed and containing 5% or less of Si by a known means such as a roll coating method, a dipping method, a spray method, or an electrophoresis method. The coating method is not particularly limited, and an optimal method may be selected according to the liquid properties and the like.
[0027]
The directionally annealed grain-oriented electrical steel sheet according to the present invention has (1) a generally known manufacturing method, that is, Mg produced by applying an annealing separator mainly composed of MgO and performing final annealing. There are two types, 2 SiO 4 or those having a finish annealing film mainly composed of Mg 2 SiO 4 and MgAl 2 O 4 , and (2) grain-oriented electrical steel sheets without these finish annealing films. It can also be applied to the grain-oriented electrical steel sheet.
[0028]
As the method for producing the grain-oriented electrical steel sheet (2) above, (a) an additive that inhibits the formation of the finish annealing film is contained in the MgO annealing separator (Japanese Patent Laid-Open No. 05-299228), (b) A method in which a finish annealing film is not intentionally formed by using it as an annealing separator mainly composed of an inert oxide such as Al 2 O 3 in place of MgO, (c) Finishing after carrying out normal finishing annealing There is a method of removing the annealed film by pickling or the like.
[0029]
In the method (b), as disclosed in JP-A-8-3648, by controlling the alkali metal element concentration in the annealing separator, not only there is no finish annealing film, but also the direction in which the surface is smooth. Steel sheet is obtained. Further, after adopting the production method (c), a grain-oriented electrical steel sheet having a smooth surface similar to (b) is obtained by chemical polishing and electrolytic polishing. The insulating film of the present invention is particularly effective for significantly reducing the iron loss value of a grain-oriented electrical steel sheet having a smooth surface.
[0030]
In the case of a grain-oriented electrical steel sheet manufactured by a general manufacturing method, that is, having a finish annealed film, directly on the annealed film mainly composed of Mg 2 SiO 4 or Mg 2 SiO 4 and MgAl 2 O 4 , There is no particular problem even if the coating liquid of the present invention is applied and baked. However, if a conventional insulating film mainly composed of phosphate and colloidal silica is formed in advance before baking the coating liquid of the present invention, an insulating film with extremely high corrosion resistance is obtained. It becomes.
[0031]
When the coating liquid of the present invention is applied to a grain-oriented electrical steel sheet having no finish annealing film, as disclosed in JP-A-06-184762, a SiO 2 film having a thickness of 0.001 μm or more is used. By forming in advance, good adhesion between the steel sheet and the insulating film can be obtained.
As a method of forming the SiO 2 film, there are a method of forming a SiO 2 external oxide film by annealing the grain-oriented electrical steel sheet in a weakly oxidizing atmosphere, and a method of forming a SiO 2 film by dry coating such as CVD or PVD. is there.
[0032]
In any grain-oriented electrical steel sheet, when used in combination with so-called magnetic domain control, such as the introduction of local strain in the form of a point sequence by laser irradiation or groove formation, an extremely low iron loss value due to the high applied tension by the insulating film of the present invention. A grain-oriented electrical steel sheet having
The grain-oriented electrical steel sheet coated with the coating liquid of the present invention is baked at 500 ° C to 1200 ° C. When the temperature is less than 500 ° C., the dehydration of the alumina hydrate is insufficient and aluminum borate is difficult to form. A baking temperature of 1200 ° C. or higher is not economical, although there is no particular disadvantage.
[0033]
More preferably, it is 700-1200 degreeC, and formation of aluminum borate advances easily in this temperature range, and high film tension is obtained.
In general, the baking atmosphere is not limited, but when applied to a grain-oriented electrical steel sheet without a finish annealed film, a non-oxidizing atmosphere is used to prevent oxidation at the interface between the insulating film and the steel sheet. It is desirable to employ an atmosphere containing hydrogen.
[0034]
【Example】
Example 1
As shown in Table 2, a variety of alumina sols and boric acids having different types and contents of crystalline and basic aluminum salts were mixed, and pure water was added as necessary to prepare a coating solution. A directional magnetic steel sheet having a thickness of 0.23 mm having a finish annealed film manufactured by a normal manufacturing method was prepared, and the coating solution in Table 2 was applied at 5 g / m 2 per side and baked at 850 ° C. for 30 seconds. . The molar ratio of Al: B in the coating solution is 2: 1. Table 2 shows the stability of the coating liquid, the film-forming property, the magnetic properties after forming the insulating film, and the insulating film tension.
[0035]
[Table 2]
The coating solution stability is the presence or absence of gelation after standing for 24 hours, the film-forming property is the presence or absence of peeling of the film after drying, and the film tension is that of the steel sheet when the insulating film is removed by alkali while protecting one side Calculated from sled.
As shown in Table 2, in coating solutions (Nos. 5 and 8) in which the content of basic aluminum chloride and basic aluminum acetate exceeds 30% of the total Al content in the alumina sol in terms of Al, Although the viscosity is unstable and the film-forming property is poor and the film is peeled after drying, such a phenomenon is not observed in the coating solution containing 30% or less of both basic aluminum salts.
[0037]
Further, when an alumina sol having a half-width of (020) diffraction line after drying of 3 degrees or more is used, a directional electromagnetic wave having a higher film tension and a lower iron loss value is obtained compared to the case where it is not. It is a steel plate.
(Example 2)
A directional electrical steel sheet having a thickness of 0.23 mm having a finish annealed film manufactured by a normal manufacturing method is prepared, and a conventional coating liquid mainly composed of colloidal silica and phosphate is applied at 5 g / m 2 to 850. After baking at 60 ° C. for 60 seconds and after applying 1 g / m 2 of colloidal silica and phosphate and baking at 600 ° C. for 30 seconds, a coating solution comprising boric acid and alumina sol is further applied at 4 g / m 2. Then, what was baked at 850 ° C. for 60 seconds was prepared.
[0038]
Two types of coating solutions composed of boric acid and alumina sol were prepared. That is, a mixture of a highly crystalline alumina sol and a low crystalline alumina sol, and a mixture using only a low crystalline alumina sol. In any alumina sol, the content of basic aluminum chloride or basic aluminum acetate is 30% or less of the total Al amount in terms of Al.
[0039]
The magnetic properties, insulating film tension, and rust resistance of the obtained grain-oriented electrical steel sheet were investigated. Rust resistance was determined by the presence or absence of rusting after spraying 5% saline at 50 ° C. for 5 hours. The results are shown in Table 3.
The grain-oriented electrical steel sheet obtained by baking the coating liquid of the present invention after baking the conventional coating liquid mainly composed of colloidal silica and phosphate is not inferior to the conventional grain-oriented electrical steel sheet using only the conventional coating liquid. It has rust resistance and the iron loss value is remarkably improved.
[0040]
In addition, the coating liquid consisting of low crystalline alumina sol and boric acid is mixed with boric acid after mixing the conventional colloidal silica and phosphate based coating liquid or alumina sol with good crystallinity and low crystalline alumina sol. In comparison with the above, the obtained film tension is large, and as a result, a low iron loss value is given.
[0041]
[Table 3]
(Example 3)
A grain-oriented electrical steel sheet without a finish annealing film having a thickness of 0.22 mm that was subjected to finish annealing in accordance with Japanese Patent Laid-Open No. 8-3648 and having a smooth surface was prepared. By using a grooved gear roll, grooves having a depth of 20 μm and a width of 100 μm were formed in a direction substantially perpendicular to the rolling direction at intervals of 5 mm. On some grain-oriented electrical steel sheets, a SiO 2 film having a thickness of 10 nm was formed by annealing in a reducing atmosphere.
[0043]
A conventional coating liquid mainly composed of colloidal silica and phosphate was applied at 5 g / m 2 and baked at 850 ° C. for 60 seconds, and a coating liquid composed of boric acid and alumina sol was applied at 5 g / m 2 and 850. What was baked at 60 degreeC for 60 second was prepared.
Two types of coating solutions composed of boric acid and alumina sol were prepared. That is, a mixture of a highly crystalline alumina sol and a low crystalline alumina sol, and a mixture using only a low crystalline alumina sol.
[0044]
In any alumina sol, the content of basic aluminum chloride or basic aluminum acetate is 30% or less of the total Al amount in terms of Al.
The magnetic properties, insulating film tension and adhesion of the obtained grain-oriented electrical steel sheet were investigated. The film adhesion was determined by the presence or absence of film peeling when a steel plate was wound around a round bar having a curvature radius of 10 mm. As shown in Table 4, by forming the SiO 2 film, the adhesion of the insulating film is improved, and the coating liquid composed of low crystalline alumina sol and boric acid is mainly composed of conventional colloidal silica and phosphate. Compared to the case where boric acid is mixed after mixing a coating solution with good crystallinity and low crystallinity alumina sol, the resulting film tension is greater, resulting in extremely low iron loss values. .
[0045]
[Table 4]
【The invention's effect】
According to the present invention, an aluminum borate-based insulating film capable of imparting a significantly greater tension to a grain-oriented electrical steel sheet than a conventional insulating film is formed with good adhesion using a coating solution with little viscosity change. And the iron loss of the grain-oriented electrical steel sheet can be remarkably improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an X-ray diffraction pattern (using CuKα rays) of alumina sol dried at 100 ° C. FIG.
FIG. 2 is a diagram showing a definition of a half width of an X-ray diffraction line.
Claims (4)
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| WO2019155858A1 (en) * | 2018-02-06 | 2019-08-15 | Ｊｆｅスチール株式会社 | Electromagnetic steel sheet with insulating coating and production method therefor |
| KR102628699B1 (en) * | 2019-01-08 | 2024-01-25 | 닛폰세이테츠 가부시키가이샤 | Grain-oriented electrical steel sheet and manufacturing method of grain-oriented electrical steel sheet |
| JP7188105B2 (en) * | 2019-01-16 | 2022-12-13 | 日本製鉄株式会社 | Oriented electrical steel sheet |
| JP7188104B2 (en) * | 2019-01-16 | 2022-12-13 | 日本製鉄株式会社 | Oriented electrical steel sheet |
| JP7448819B2 (en) | 2020-08-20 | 2024-03-13 | 日本製鉄株式会社 | Grain-oriented electrical steel sheet and its manufacturing method |
| WO2024096082A1 (en) * | 2022-11-01 | 2024-05-10 | 日本製鉄株式会社 | Grain-oriented electromagnetic steel sheet |
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| JPS60131976A (en) * | 1983-12-19 | 1985-07-13 | Kawasaki Steel Corp | Manufacture of grain-oriented silicon steel sheet having superior iron loss characteristic |
| JP2698003B2 (en) * | 1992-08-25 | 1998-01-19 | 新日本製鐵株式会社 | Method for forming insulating film on unidirectional silicon steel sheet |
| JP3172025B2 (en) * | 1994-01-13 | 2001-06-04 | 新日本製鐵株式会社 | Method for forming insulating film on unidirectional silicon steel sheet with good adhesion |
| JP2664337B2 (en) * | 1994-04-15 | 1997-10-15 | 新日本製鐵株式会社 | Method for forming insulating film on unidirectional silicon steel sheet |
| JP3272211B2 (en) * | 1995-09-13 | 2002-04-08 | 新日本製鐵株式会社 | Method of forming insulating film on magnetic domain controlled unidirectional silicon steel sheet |
| JP3369840B2 (en) * | 1996-03-29 | 2003-01-20 | 新日本製鐵株式会社 | Method for producing low iron loss unidirectional silicon steel sheet |
| JPH09272981A (en) * | 1996-04-09 | 1997-10-21 | Nippon Steel Corp | Production of low core loss grain oriented silicon steel sheet |
| JP3406799B2 (en) * | 1997-04-14 | 2003-05-12 | 新日本製鐵株式会社 | Method for producing unidirectional silicon steel sheet having aluminum borate coating |
| JP4277432B2 (en) * | 1999-12-27 | 2009-06-10 | 住友金属工業株式会社 | Low magnetostrictive bi-directional electrical steel sheet |
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