JP3930696B2 - Unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film and method for producing the same - Google Patents
Unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film and method for producing the same Download PDFInfo
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【０００１】
【発明の属する技術分野】
本発明は、フォルステライト（Ｍｇ2ＳｉＯ4）等で構成される無機鉱物質皮膜の生成を意図的に防止して製造したり、さらには、鏡面光沢を呈するまで表面を平坦化させたりして調製した仕上げ焼鈍済みの一方向性珪素鋼板に対し、張力付与性の絶縁性皮膜を形成させた一方向性珪素鋼板とその製造方法に関するものである。
【０００２】
【従来の技術】
一方向性珪素鋼板は磁気鉄芯材料として多用されており、特にエネルギーロスを少なくするために、鉄損の少ない材料が求められている。鉄損の低減には鋼板に張力を付与することが有効であることから、鋼板に比べ熱膨張係数の小さい材質からなる皮膜を高温で形成することによって鋼板に張力を付与し、鉄損低減が図られてきた。仕上げ焼鈍工程で鋼板表面の酸化物と焼鈍分離剤とが反応して生成するフォルステライト系皮膜は、鋼板に張力を与えることで磁気特性の向上に寄与し、また、皮膜密着性も優れている。
【０００３】
また、特開昭４８−３９３３８号公報で開示されたコロイド状シリカとリン酸塩を主体とするコーティング液を鋼板表面に塗布し、焼き付けることによって絶縁皮膜を形成する方法は、鋼板に対する張力付与の効果が大きく、鉄損低減に有効である。
そこで、仕上げ焼鈍工程で生じたフォルステライト系皮膜を残した上でリン酸塩を主体とする絶縁皮膜を形成することが、一般的な一方向性珪素鋼板の製造方法となっている。
【０００４】
近年、フォルステライト系皮膜と地鉄の乱れた界面構造が、皮膜張力による鉄損改善効果をある程度減少させていることが明らかになってきた。そこで、例えば、特開昭４９−９６９２０号公報に開示されている如く、仕上げ焼鈍工程で生ずるフォルステライト系皮膜を除去したり、さらに、鏡面化仕上げを行った後、改めて張力皮膜を形成させることにより、さらなる鉄損低減を試みる技術が開発された。
【０００５】
しかしながら、上記絶縁皮膜においては、フォルステライトを主体とする皮膜の上に形成した場合はかなりの密着性が得られるものの、フォルステライト系皮膜を除去したり、あるいは、仕上げ焼鈍工程で意図的にフォルステライト形成を行わなかったものに対しては皮膜密着性が十分ではない。特に、フォルステライト系皮膜の除去を行った場合は、コーティング液を塗布して形成させる張力付与型絶縁皮膜のみで所要の皮膜張力を確保する必要があり、必然的に厚膜化しなければならず、より一層の密着性が必要である。
【０００６】
したがって、従来の皮膜形成法では、鏡面化の効果を十分に引き出すほどの皮膜張力を達成し、かつ、皮膜密着性をも確保することは困難であり、十分な鉄損低減が図られていなかった。
そこで、張力付与性絶縁皮膜の密着性を確保するための技術として、張力付与性絶縁皮膜の形成に先立ち、仕上げ焼鈍済みの一方向性珪素鋼板の表面に酸化膜を形成させる方法が、例えば、特開昭６０−１３１９７６号公報、特開平６−１８４７６２号公報、特開平７−２７８８３３号公報、特開平８−１９１０１０号公報、特開平９−０７８２５２号公報、において開示された。
【０００７】
特開昭６０−１３１９７６号公報記載の方法は、仕上げ焼鈍済みの一方向性珪素鋼板を鏡面化した後、鋼板表面付近を内部酸化させる方法で、この内部酸化層によって張力皮膜の密着性を向上させ、内部酸化、即ち鏡面度減退で生じる鉄損劣化を、皮膜密着性向上によってもたらされる付与張力の増大で補おうとする方法である。
【０００８】
特開平６−１８４７６２号公報記載の方法は、鏡面化ないしはそれに近い状態に調製した仕上げ焼鈍済みの一方向性珪素鋼板に対し、温度ごとに特定の雰囲気で焼鈍を施すことにより鋼板表面に外部酸化型の酸化膜を形成し、この酸化膜でもって張力付与性絶縁皮膜の皮膜と鋼板との皮膜密着性を確保する方法である。特開平７−２７８８３３号公報記載の方法は、張力付与性の絶縁皮膜が結晶質である場合において、無機鉱物質皮膜のない仕上げ焼鈍済みの一方向性珪素鋼板の表面に予め非晶質の酸化物の下地皮膜を形成させておくことで、結晶質の張力付与性絶縁皮膜が形成される際に起こる鋼板酸化、即ち、鏡面度減退を防止する方法である。
【０００９】
特開平８−１９１０１０号公報記載の方法は、非金属物質を除去した仕上げ焼鈍済みの一方向性珪素鋼板の表面に結晶性のファイヤライトを形成させることで、ファイヤライト結晶による張力付与効果と密着性向上効果により鉄損低減を図る方法である。
特開平９−０７８２５２号公報記載の方法は、無機鉱物質皮膜のない仕上げ焼鈍済みの一方向性珪素鋼板の表面に形成させる下地シリカ層の量を１００ｍｇ／ｍ２以下にすることで、張力皮膜の密着性確保だけでなく、良好な鉄損値をも実現しようとする方法である。
【００１０】
【発明が解決しようとする課題】
上述の方法を適用し、無機鉱物質のない一方向性珪素鋼板の表面に酸化膜を形成させることで、皮膜密着性の改善や鉄損値の低減を図るという効果は、それなりに認められる。しかしながら、張力付与性絶縁皮膜の皮膜密着性は必ずしも完全ではなかった。
【００１１】
【課題を解決するための手段】
本発明は、上述の問題点を解決し、無機鉱物質皮膜のない仕上げ焼鈍済みの一方向性珪素鋼板に対し、十分な皮膜密着性を得ることができるよう張力付与型の絶縁性皮膜を形成させることを特徴とするものである。
本発明の要旨は、次のとおりである。
【００１２】
（１）フォルステライトの無機鉱物質皮膜の生成を意図的に防止して製造した後、張力付与性の絶縁皮膜を形成した一方向性珪素鋼板であって、張力付与性絶縁皮膜と鋼板との界面に、平均膜厚が２ｎｍ以上５００ｎｍ以下でシリカを主体とする膜状外部酸化膜に加え、該膜状外部酸化膜の膜厚を貫通した形で生成し、前記張力付与性絶縁皮膜の形成時、該張力付与性絶縁皮膜側に嵌入する形態で存在し、前記膜状外部酸化膜に対する断面面積比率が２％以上の、シリカを主体とする粒状外部酸化物を有することを特徴とする張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板。
【００１３】
（２）前記張力付与性絶縁皮膜が、リン酸塩とコロイド状シリカを主体とする塗布液を焼き付けることによって生成させたものであることを特徴とする前記（１）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板。
【００１４】
（３）前記張力付与性絶縁皮膜が、アルミナゾルとほう酸を主体とする塗布液を焼き付けることによって生成させたものであることを特徴とする前記（１）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板。
（４）フォルステライトの無機鉱物質皮膜の生成を意図的に防止して製造した仕上げ焼鈍済み一方向性珪素鋼板に対し、張力付与性絶縁皮膜と鋼板との密着性を確保するため、張力付与性絶縁皮膜の形成に先立ち、該鋼板に低酸化性雰囲気中で焼鈍を施すことにより、鋼板表面にシリカを主体とする酸化物を形成させた後、張力付与性絶縁皮膜形成用の塗布液を塗布し、焼き付けることによって張力付与性絶縁皮膜を形成し一方向性珪素鋼板を製造する方法において、皮膜密着性確保のための低酸化性雰囲気中焼鈍を施す前に、鋼板表面に微少歪ないしは微小凹凸を付与し、平均膜厚が２ｎｍ以上５００ｎｍ以下でシリカを主体とする膜状外部酸化膜に加え、前記張力付与性絶縁皮膜の形成時、該張力付与性絶縁皮膜側に嵌入する形態で存在し、前記膜状外部酸化膜に対する断面面積比率が２％以上の、シリカを主体とする粒状外部酸化物を、前記膜状外部酸化膜の膜厚を貫通した形で生成させることを特徴とする張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板の製造方法。
【００１５】
（５）前記鋼板表面に、砥粒付きブラシで微少歪を付与することを特徴とする前記（４）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板の製造方法。
【００１６】
（６）前記鋼板表面に、酸洗で微小凹凸を付与することを特徴とする前記（４）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板の製造方法。
（７）前記張力付与性絶縁皮膜が、リン酸塩とコロイド状シリカを主体とする塗布液を焼き付けることによって生成させたものであることを特徴とする前記（４）、（５）または（６）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板の製造方法。
【００１７】
（８）前記張力付与性絶縁皮膜が、アルミナゾルとほう酸を主体とする塗布液を焼き付けることによって生成させたものであることを特徴とする前記（４）、（５）または（６）記載の張力付与性絶縁皮膜の皮膜密着性に優れる一方向性珪素鋼板の製造方法。
【００１８】
【発明の実施の形態】
以下、発明の詳細について説明する。
発明者らは、張力付与性絶縁皮膜の形成に先立ち、仕上げ焼鈍済みの一方向性珪素鋼板の表面に酸化膜を形成させる方法によっても、皮膜密着性が必ずしも完全ではない原因として、酸化膜を形成させる前の鋼板の表面状態に問題があるのではないかと考えた。つまり、表面状態の違いにより外部酸化型酸化膜の構造が変動し、その結果、張力付与性絶縁皮膜の皮膜密着性に差異が生じているのではないかと推測した。
【００１９】
そこで、外部酸化型酸化膜形成前の鋼板に対し、前処理を施し、張力付与性絶縁皮膜の密着性に対する前処理の有無と、外部酸化型酸化膜の構造との関係を調べた。
実験用素材として、板厚０．２２５ｍｍの一方向性珪素鋼板の脱炭焼鈍板に対し、アルミナを主体とする焼鈍分離剤を塗布して仕上げ焼鈍を行い、二次再結晶させ、鏡面光沢を有する一方向性珪素鋼板を準備した。ついで、シリコンカーバイド砥粒付きブラシで鋼板表面に微少な歪を導入する前処理を行なう条件と行わない条件で試料を作製した。
【００２０】
次に、窒素２５％、水素７５％、露点−１℃の雰囲気において均熱時間１０秒で、種々の温度で熱処理を行ない、シリカを主体とする外部酸化型酸化膜を形成させた。最後に、張力付与性の絶縁皮膜を形成するため、リン酸アルミニウム、クロム酸、コロイダルシリカを主体とする塗布液を塗布し、窒素雰囲気中で８３５℃で３０秒間焼き付けた。このようにして作製した鋼板の皮膜密着性を調べた。
【００２１】
皮膜密着性は、直径２０ｍｍの円筒に試料を巻き付けた時、鋼板から剥離せず、鋼板と皮膜が密着したままであった部分の面積率（以後、皮膜残存面積率と称する）で評価した。密着性が不良で皮膜が完全に剥離した場合は０％、皮膜密着性が良好で皮膜が全く剥離しなかった場合を１００％と判定した。評価は皮膜残存面積率が９０％以下の場合を×、９５％のものを○、１００％のものを◎とした。
【００２２】
また、張力付与性絶縁皮膜と鋼板との界面に存在する外部酸化型酸化膜の構造を調べるため、集中イオンビーム法（以下、ＦＩＢ法と称する）によって試料を作製し、透過型電子顕微鏡（以下、ＴＥＭと称する）で断面構造を観察した。ＦＩＢ法とは、鋼板上に形成した厚さ数μｍの皮膜を断面方向から観察できるよう、皮膜付き鋼板試料の所望の位置から厚さ数μｍの薄片状試料を作製・採取する手法である。
【００２３】
ＦＩＢ法で薄膜試料を作製し、ＴＥＭで鋼板と張力付与性絶縁皮膜の界面部分を調べたところ、シリカ主体の外部酸化型酸化膜が観察された。中でも、中間層である酸化膜を形成させる前に砥粒入りブラシで鋼板表面に微少歪を導入した試料については、外部酸化型の膜状酸化膜に加え、図１に示すような、膜状酸化膜を貫通し、張力付与性絶縁皮膜側に嵌入するような形態のシリカ主体の粒状酸化物が観察された。
【００２４】
このような界面部分を多数、観察し、その断面において、膜状酸化膜に対する粒状酸化物の比率（以下、粒状酸化物面積率と称する）を算出した。また、外部酸化型酸化膜の平均膜厚も求めた。結果を表１にまとめた。
【００２５】
【表１】
表１から、張力付与性絶縁皮膜の密着性を確保できる条件を求めると、次のようになる。
まず、熱処理温度５００℃の条件で、外部酸化型酸化膜の膜厚が１ｎｍの試料番号１と試料番号２の条件では、皮膜残存面積率が、それぞれ、１０％と２０％と低く、砥粒付きブラシによる前処理の有無に関わらず、皮膜密着性が確保できない。
【００２７】
一方、外部酸化型酸化膜の膜厚が２ｎｍ以上の試料番号３から試料番号１６の熱処理温度が６００℃から１１５０℃の条件においては、皮膜残存面積率が９０％以上となり、概ね、皮膜密着性が確保できるようになる。
但し、砥粒付きブラシによる前処理を行ない、粒状酸化物の断面面積率が２％以上の条件では、皮膜密着性が良好であるが、砥粒付きブラシによる前処理を行なわない、粒状酸化物の少ない、即ち、断面面積率にして０％ないしは１％の条件では外部酸化型酸化膜の膜厚が厚くとも、皮膜密着性が必ずしも完全とはいえず、皮膜残存面積率で９０％となった。
【００２８】
特に、試料番号１２、１４、１６の外部酸化型酸化膜の膜厚が４０ｎｍ以上で、熱処理温度が１０００℃以上の条件では、皮膜密着性が格段に良好である。
表１から、張力付与性絶縁皮膜の皮膜密着性を完全に確保するためには、外部酸化型酸化膜の膜厚が２ｎｍ以上で、かつ、粒状酸化物の断面面積率が２％以上であることが必須であることがわかる。こうした粒状酸化物を、膜状酸化物とともに形成させるためには、外部酸化型酸化膜を形成させるための熱処理に先立ち、鋼板表面に微少歪を導入し、その後、外部酸化型酸化膜の形成を、温度６００℃以上、特に好ましくは、１０００℃以上で行なう必要があることがわかる。
【００２９】
次に、外部酸化型酸化膜を形成させる前の鋼板前処理として、１％硝酸中で室温で１０秒間、軽酸洗を行ない、表面に微小な凹凸を形成した条件で、表１と同様の手順で実験と評価を行なった。結果を表２に示す。
【００３０】
【表２】
表２から、張力付与性絶縁皮膜の密着性を確保できる条件を求めると、次のようになる。
まず、熱処理温度５００℃の条件で、外部酸化型酸化膜の膜厚が１ｎｍの試料番号１と試料番号２の条件では、皮膜残存面積率が、それぞれ、２０％と３０％と低く、硝酸酸洗による表面微小凹凸化処理の有無に関わらず、皮膜密着性が確保できない。
【００３２】
一方、外部酸化型酸化膜の膜厚が２ｎｍ以上の試料番号３から試料番号１６の熱処理温度が６００℃から１１５０℃の条件においては、概ね、皮膜密着性が確保できるようになる。
但し、砥粒付きブラシによる前処理を行ない、粒状酸化物の断面面積率が２％以上の条件では、皮膜密着性が良好であるが、硝酸酸洗処理を行なわない、粒状酸化物の少ない、即ち、断面面積率にして０％か、ないしは、１％の条件では、たとえ外部酸化型酸化膜の膜厚が厚くとも、皮膜密着性が必ずしも完全とはいえず、皮膜残存面積率で９０％となった。
【００３３】
特に、試料番号１２、１４、１６の外部酸化型酸化膜の膜厚が４０ｎｍ以上で、熱処理温度が１０００℃以上の条件では、皮膜密着性が格段に良好である。
以上から、張力付与性絶縁皮膜の皮膜密着性を完全に確保するためには、外部酸化型酸化膜の膜厚が２ｎｍ以上で、かつ、粒状酸化物の断面面積率が２％以上であることが必須であることがわかる。こうした粒状酸化物を、膜状酸化物とともに形成させるためには、外部酸化型酸化膜を形成させるための熱処理に先立ち、鋼板表面に微小凹凸を導入し、その後、外部酸化型酸化膜の形成を、温度６００℃以上、特に好ましくは、１０００℃以上で行なう必要があることがわかる。
【００３４】
このように皮膜密着性について、外部酸化型酸化膜の膜厚や粒状酸化物の占める断面面積率が大きく影響していることについて、発明者らはその機構を次のように考えている。
まず、外部酸化型酸化膜における温度と膜厚の関係について述べる。
鋼板と張力付与性絶縁皮膜との密着性は、両者の界面に形成させた外部酸化型酸化膜によって決まる。一般に外部酸化型酸化膜は、金属原子が鋼中から表面に拡散し、表面で酸化性ガスと反応することで成長するといわれている。そのため、酸化膜の成長速度は原子の拡散速度によって決まる。原子の拡散は熱エネルギーによって高められる。したがって、温度が高いほど原子の拡散が促進され、外部酸化型酸化膜はより成長する。
【００３５】
こうした機構のため熱処理温度が５００℃と低い条件では、外部酸化型の酸化膜の成長が十分ではないため、皮膜密着性が十分ではなく、一方、熱処理温度が６００℃以上では、十分に外部酸化型酸化膜が成長するので、皮膜密着性は良好で、さらに、１０００℃以上では、さらに酸化膜が成長し易くなるので、皮膜密着性が極めて良好となるものと考えられる。
【００３６】
こうした推測が妥当であることは、透過型電子顕微鏡を使った外部酸化型酸化膜の膜厚測定の結果からわかる。即ち、膜厚が１ｎｍで、外部酸化型酸化膜の成長が十分でない、熱処理温度５００℃の条件では、張力付与型絶縁皮膜の密着性が不良であるのに対し、膜厚２ｎｍ以上で、外部酸化型酸化膜が成長した、熱処理温度６００℃以上の条件では、皮膜密着性は良好である。
【００３７】
外部酸化型酸化膜中に粒状酸化物が形成される機構の詳細は未だ不明であるが、外部酸化型酸化膜を形成するのに先立ち、鋼板表面を砥粒入りブラシで払拭することにより微少歪を導入したり、あるいは、酸洗によって微小凹凸を形成したりすることにより、こうした微少歪や微小凹凸を起点として酸化膜が特に成長し、粒状形態にまで発達するのではないか、と発明者らは考えている。
【００３８】
次に、張力付与性絶縁皮膜の鋼板密着性と粒状酸化物の断面面積率との関係について述べる。
張力付与性絶縁皮膜による鋼板への張力付与は、張力付与性絶縁皮膜と鋼板との熱膨張係数の差によってもたらされる。この時、張力付与性絶縁皮膜と鋼板との界面には多大な応力が発生する。この応力に耐え、鋼板と張力付与性絶縁皮膜の密着性を確保するのが外部酸化型酸化膜である。
【００３９】
発明者らは、こうした応力耐性に関し、粒状酸化物が影響しているのではないかと推測している。つまり、粒状酸化物が外部酸化型酸化膜の膜厚を貫通した形で生成し、それにより、張力付与性絶縁皮膜を形成した時に、粒状酸化物が張力付与性絶縁皮膜側に差し込んだ様な形態、いわゆる、楔状に嵌入することで強い応力耐性が発現しているのではないかと推定している。
【００４０】
外部酸化型酸化膜に対する粒状酸化物の比率が２％以上の場合、応力に耐え得るが、粒状酸化物の比率が２％よりも少ない場合、外部酸化型酸化膜が、張力付与性絶縁皮膜によって押しかかる応力に耐えることができず、張力付与性絶縁皮膜が剥離してしまうのではないかと考えている。
外部酸化型酸化膜の膜厚の上限については、皮膜密着性の点からは特に限定されないが、５００ｎｍよりも厚くなると、非磁性部分の増加により、トランスのおける重要指標である占積率の悪化を招くので、５００ｎｍ以下にすることが望ましい。
【００４１】
【実施例】
（実施例１）
板厚０．２２５ｍｍ、Ｓｉ濃度３．３０質量％の一方向性珪素鋼板製造用の冷延板に脱炭焼鈍を施した後、表面酸化層を弗化アンモニウムと硫酸の混合溶液中で酸洗し溶解除去した。ついで、アルミナ粉末を静電塗布法で塗布し、乾燥水素雰囲気中、１２００℃、２０時間の仕上げ焼鈍を行なった。こうして調製した二次再結晶済みの一方向性珪素鋼板の表面には無機鉱物質がなく、かつ、鏡面光沢を有する。
【００４２】
この鋼板に対し、アルミナ砥粒付きブラシで鋼板表面を払拭したもの（実施例）と払拭しなかったもの（比較例）を作製した。ついで、窒素５０％、水素５０％、露点−１０℃の雰囲気中、温度９００℃で熱処理を行なうことで、外部酸化型酸化膜を形成させた。
次に、調製した鋼板に対し、濃度５０％のリン酸マグネシム／アルミニウム水溶液５０ｍｌ、濃度３０％のコロイダルシリカ水分散液６６ｍｌ、無水クロム酸５ｇからなる混合液を塗布し、８５０℃で３０秒間焼き付け、張力付与性の絶縁皮膜を形成させた。
【００４３】
こうして調製した絶縁皮膜付き一方向性珪素鋼板について、その断面をＦＩＢ−ＴＥＭ法で調べ、外部酸化型酸化膜の平均膜厚を粒状酸化物の断面面積率を算出した。また、直径２０ｍｍの円筒に試料を巻き付けた時の皮膜残存面積率で皮膜密着性を評価した。結果を表３に示す。
【００４４】
【表３】
表３から、砥粒付きブラシによる払拭を行なわず、粒状酸化物面積率１％で皮膜残存面積率９０％である比較例に比べ、砥粒付きブラシによる払拭を行ない、粒状酸化物面積率１０％で皮膜残存面積率９５％である実施例のほうが、皮膜密着性が良好で優れていることがわかる。
（実施例２）
板厚０．２２５ｍｍ、Ｓｉ濃度３．３５質量％の一方向性珪素鋼板製造用の冷延板に脱炭焼鈍を施し、表面にマグネシアと塩化ビスマスを主体とする焼鈍分離剤の水スラリーを塗布し、乾燥した。ついで、乾燥水素雰囲気中、１２００℃、２０時間の仕上げ焼鈍を行ない、表面に無機鉱物質のほとんどない二次再結晶の完了した一方向性珪素鋼板を得た。ついで、２％硝酸、室温下で５秒間酸洗し、表面に微少な凹凸を形成したもの（実施例）と酸洗をしなかったもの（比較例）を作製した。
【００４６】
次に、この鋼板に対し、窒素２５％、水素７５％、露点−１５℃の雰囲気中、温度１１５０℃で熱処理を行なうことで、シリカを主体とする外部酸化型酸化膜を形成させた。ついで、調製した鋼板に対し、濃度５０％のリン酸マグネシウム水溶液５０ｍｌ、濃度２０％のコロイダルシリカ水分散液１００ｍｌ、無水クロム酸５ｇからなる混合液を塗布し、８５０℃で３０秒間焼き付け、張力付与性の絶縁皮膜を形成させた。
【００４７】
こうして調製した絶縁皮膜付き一方向性珪素鋼板について、直径２０ｍｍの円筒に試料を巻き付けた時の皮膜残存面積率で絶縁皮膜の密着性を評価した。結果を表４に示す。
【００４８】
【表４】
表４から、酸洗による前処理を行なわず、粒状酸化物面積率１％で皮膜残存面積率９０％である比較例に比べ、酸洗を行ない、粒状酸化物面積率１５％で皮膜残存面積率９５％である実施例のほうが、皮膜密着性が良好で優れていることがわかる。
（実施例３）
板厚０．２２５ｍｍ、Ｓｉ濃度３．２５質量％の一方向性珪素鋼板製造用の冷延板に脱炭焼鈍を施し、表面にアルミナを主体とする焼鈍分離剤の水スラリーを塗布し、乾燥した。ついで、乾燥水素雰囲気中、１２００℃、２０時間の仕上げ焼鈍を行ない、表面に無機鉱物質がほとんどなく、鏡面光沢を有する二次再結晶の完了した一方向性珪素鋼板を得た。この鋼板に対し、シリコンカーバイド砥粒付きブラシで鋼板表面を払拭したもの（実施例）と払拭しなかったもの（比較例）を作製した。
【００５０】
ついで、窒素３０％、水素７０％、露点−２℃の雰囲気中、温度８００℃で熱処理を行なうことで、外部酸化型酸化膜を形成させた。ついで、調製した鋼板に対し、濃度５０％のリン酸アルミニウム水溶液５０ｍｌ、濃度２０％のコロイダルシリカ水分散液１００ｍｌ、無水クロム酸５ｇからなる混合液を塗布し、８５０℃で３０秒間焼き付け、張力付与性の絶縁皮膜を形成させた。
【００５１】
こうして調製した絶縁皮膜付き一方向性珪素鋼板について、直径２０ｍｍの円筒に試料を巻き付けた時の皮膜残存面積率で皮膜密着性を評価した。結果を表５に示す。
【００５２】
【表５】
表５から、砥粒付きブラシによる払拭を行なわず、粒状酸化物面積率１％で皮膜残存面積率９０％である比較例に比べ、砥粒付きブラシによる払拭を行ない、粒状酸化物面積率２１％で皮膜残存面積率９５％である実施例のほうが、皮膜密着性が良好で優れていることがわかる。
（実施例４）
板厚０．２３ｍｍ、Ｓｉ濃度３．３０質量％の一方向性珪素鋼板製造用の冷延板に脱炭焼鈍を施し、表面にマグネシアを主体とする焼鈍分離剤の水スラリーを塗布し、乾燥した後、乾燥水素雰囲気中、１２００℃、２０時間の仕上げ焼鈍を行なった。こうして調製した二次再結晶の完了した一方向性珪素鋼板の表面にはフォルステライトを主体とする皮膜が生成している。
【００５４】
ついで、ふっ化アンモニウムと硫酸の混合溶液中で酸洗し、表面皮膜を溶解除去した後、ふっ酸と過酸化水素水の混合溶液中で化学研磨し、鋼板表面に無機鉱物質がなく、かつ、鏡面光沢をもつ鋼板を得た。
この鋼板に対し、アルミナ粉末を投射することにより表面に微少歪を導入したもの（実施例）としなかったもの（比較例）を作製した。ついで、窒素５０％、水素５０％、露点−８℃の雰囲気中、温度１０５０℃で熱処理を行なう事で外部酸化型酸化膜を形成させた。
【００５５】
次に、１０％濃度のコロイダルアルミナ水分散液１００ｍｌ、不定形アルミナ粉末１０ｇ、ホウ酸５ｇ、水２００ｍｌからなる混合液を塗布し、９００℃で３０秒間焼き付け、張力付与性の絶縁皮膜を形成させた。
こうして調製した絶縁皮膜付き一方向性珪素鋼板について、直径２０ｍｍの円筒に試料を巻き付けた時の皮膜残存面積率で皮膜密着性を評価した。結果を表６に示す。
【００５６】
【表６】
表６から、アルミナ粉末の投射を行なわず、粒状酸化物面積率１％で皮膜残存面積率９０％である比較例に比べ、アルミナ粉末の投射を行ない、表面に歪を導入した粒状酸化物面積率３０％で皮膜残存面積率９５％である実施例のほうが、皮膜密着性が良好で優れていることがわかる。
【００５８】
【発明の効果】
本発明により、皮膜密着性の良好な無機鉱物質皮膜のない一方向性珪素鋼板を得ることができる。
【図面の簡単な説明】
【図１】シリカを主体とする粒状外部酸化物の態様を示す図（顕微鏡写真）である。[0001]
BACKGROUND OF THE INVENTION
The present invention is produced by intentionally preventing the formation of an inorganic mineral film composed of forsterite (Mg 2 SiO 4 ) or the like, and further flattening the surface until it exhibits a specular gloss. The present invention relates to a unidirectional silicon steel sheet in which a tension-imparting insulating film is formed on the prepared finish-oriented unidirectional silicon steel sheet and a method for producing the same.
[0002]
[Prior art]
Unidirectional silicon steel sheets are widely used as magnetic iron core materials, and materials with low iron loss are particularly required to reduce energy loss. Since it is effective to apply tension to the steel sheet to reduce iron loss, it is possible to reduce the iron loss by applying tension to the steel sheet by forming a coating made of a material having a smaller thermal expansion coefficient than that of the steel sheet at a high temperature. It has been planned. The forsterite film formed by the reaction between the oxide on the steel sheet surface and the annealing separator in the final annealing process contributes to the improvement of magnetic properties by applying tension to the steel sheet, and also has excellent film adhesion. .
[0003]
In addition, the method of forming an insulating film by applying a coating liquid mainly composed of colloidal silica and phosphate disclosed in JP-A-48-39338 on the surface of a steel sheet and baking the coating liquid, Great effect, effective in reducing iron loss.
Therefore, it is a general method for producing a unidirectional silicon steel sheet to leave the forsterite-based film generated in the finish annealing step and form an insulating film mainly composed of phosphate.
[0004]
In recent years, it has become clear that the disordered interface structure between the forsterite film and the ground iron reduces the iron loss improvement effect due to the film tension to some extent. Therefore, for example, as disclosed in Japanese Patent Laid-Open No. 49-96920, after removing the forsterite-based film generated in the finish annealing process and further performing a mirror finish, a tension film is formed again. Has developed a technology to further reduce iron loss.
[0005]
However, in the above insulating film, when it is formed on a film mainly composed of forsterite, considerable adhesion can be obtained, but the forsterite film is removed or the film is intentionally formed in the final annealing process. Film adhesion is not sufficient for the case where stellite is not formed. In particular, when removing forsterite-based films, it is necessary to ensure the required film tension with only the tension-imparting insulating film that is formed by applying a coating solution. More adhesion is required.
[0006]
Therefore, in the conventional film formation method, it is difficult to achieve a film tension enough to bring out the effect of mirroring and to ensure film adhesion, and sufficient iron loss reduction has not been achieved. It was.
Therefore, as a technique for ensuring the adhesion of the tension-imparting insulating film, prior to the formation of the tension-imparting insulating film, a method of forming an oxide film on the surface of the finished unidirectional silicon steel sheet, for example, This is disclosed in JP-A-60-131976, JP-A-6-184762, JP-A-7-278833, JP-A-8-191010, and JP-A-9-078252.
[0007]
The method described in JP-A-60-131976 is a method in which a unidirectional silicon steel plate that has been subjected to finish annealing is mirror-finished, and the vicinity of the steel plate surface is internally oxidized. This internal oxide layer improves the adhesion of the tension film. In this method, iron loss deterioration caused by internal oxidation, that is, reduction in specularity is compensated by an increase in applied tension caused by improvement in film adhesion.
[0008]
In the method described in JP-A-6-184762, the surface of a steel sheet is externally oxidized by performing annealing in a specific atmosphere at each temperature on a unidirectional silicon steel sheet that has been mirror-finished or finished to a close condition. In this method, a mold oxide film is formed, and the film adhesion between the tension-providing insulating film and the steel sheet is ensured with this oxide film. In the method described in Japanese Patent Application Laid-Open No. 7-278833, in the case where the tension-providing insulating film is crystalline, the surface of the unidirectional silicon steel plate that has been annealed without an inorganic mineral film is previously oxidized amorphous. This is a method of preventing steel plate oxidation, that is, reduction in specularity, which occurs when a crystalline tension-imparting insulating film is formed by forming a base film of the object.
[0009]
The method described in Japanese Patent Application Laid-Open No. Hei 8-191010 discloses a method of forming a crystalline firelite on the surface of a unidirectional silicon steel sheet that has been subjected to finish annealing from which non-metallic substances have been removed, thereby providing a tension-imparting effect and adhesion with a firelite crystal. This is a method for reducing iron loss by improving the property.
In the method described in Japanese Patent Laid-Open No. 9-078252, the amount of the base silica layer formed on the surface of the finish-oriented annealed unidirectional silicon steel sheet having no inorganic mineral film is reduced to 100 mg / m 2 or less. This is a method of not only ensuring adhesion but also achieving a good iron loss value.
[0010]
[Problems to be solved by the invention]
By applying the above-described method and forming an oxide film on the surface of the unidirectional silicon steel sheet having no inorganic mineral, the effects of improving the film adhesion and reducing the iron loss value are recognized as such. However, the film adhesion of the tension-imparting insulating film is not always perfect.
[0011]
[Means for Solving the Problems]
The present invention solves the above-mentioned problems and forms a tension-imparting type insulating film so that sufficient film adhesion can be obtained with respect to a unidirectional silicon steel sheet that has been annealed without an inorganic mineral film. It is characterized by making it.
The gist of the present invention is as follows.
[0012]
(1) A unidirectional silicon steel sheet that is produced by intentionally preventing formation of an inorganic mineral film of forsterite and then forming a tension-imparting insulating film, comprising: In addition to a film-like external oxide film having an average film thickness of 2 nm or more and 500 nm or less at the interface, the film is formed so as to penetrate the film thickness of the film-like external oxide film, thereby forming the tension-imparting insulating film. A tension which is present in a form to be fitted into the tension-providing insulating film and has a granular external oxide mainly composed of silica having a cross-sectional area ratio of 2% or more with respect to the film-like external oxide film A unidirectional silicon steel sheet excellent in film adhesion of an imparting insulating film.
[0013]
( 2 ) The tension-imparting insulating film according to ( 1 ), wherein the tension-imparting insulating film is formed by baking a coating liquid mainly composed of phosphate and colloidal silica. Unidirectional silicon steel sheet with excellent film adhesion.
[0014]
( 3 ) The film adhesion of the tension-imparting insulating film according to (1), wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. Unidirectional silicon steel sheet with excellent resistance.
( 4 ) In order to ensure the adhesion between the tension-imparting insulating coating and the steel sheet, the finish-annealed unidirectional silicon steel sheet produced by intentionally preventing the formation of the inorganic mineral film of forsterite is applied with tension. Prior to forming the insulating insulating film, the steel sheet is annealed in a low oxidizing atmosphere to form an oxide mainly composed of silica on the surface of the steel sheet, and then a coating liquid for forming a tension-imparting insulating film is formed. In the method of producing a unidirectional silicon steel sheet by applying and baking to form a tension-imparting insulating film, the surface of the steel sheet is slightly strained or minutely annealed in a low-oxidation atmosphere to ensure film adhesion. irregularity was applied, in addition to the film-like outer oxide layer having an average thickness mainly composed of silica 2nm or 500nm or less, during the formation of the tensioning insulating coating, exist in a form that fits into the tension-imparting insulating film side And, cross-sectional area ratio with respect to the film-like external oxide film is 2% or more, and characterized in that the granular outer oxide mainly comprising silica, cause raw made in the form of penetrating the thickness of the film-like external oxide film A method for producing a unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film.
[0015]
( 5 ) The method for producing a unidirectional silicon steel sheet excellent in film adhesion of the tension-imparting insulating film according to ( 4 ), wherein a slight strain is imparted to the surface of the steel sheet with a brush with abrasive grains.
[0016]
( 6 ) The method for producing a unidirectional silicon steel sheet excellent in film adhesion of the tension-imparting insulating film according to ( 4 ), wherein fine irregularities are imparted to the steel sheet surface by pickling.
( 7 ) The above-mentioned ( 4 ), ( 5 ) or ( 6 ), wherein the tension-imparting insulating film is formed by baking a coating liquid mainly composed of phosphate and colloidal silica. ) A method for producing a unidirectional silicon steel sheet having excellent film adhesion of the tension-providing insulating film.
[0017]
( 8 ) The tension described in ( 4 ), ( 5 ) or ( 6 ) above, wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. A method for producing a unidirectional silicon steel sheet excellent in film adhesion of an imparting insulating film.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, details of the invention will be described.
Prior to the formation of the tension-imparting insulating film, the inventors have considered that the film adhesion is not always perfect even by the method of forming an oxide film on the surface of the unidirectional silicon steel sheet that has been subjected to finish annealing. We thought that there might be a problem in the surface condition of the steel plate before forming. That is, it was speculated that the structure of the external oxide oxide film fluctuated due to the difference in surface state, and as a result, the film adhesion of the tension-imparting insulating film might be different.
[0019]
Therefore, the steel sheet before the formation of the external oxide type oxide film was pretreated, and the relationship between the presence or absence of the pretreatment for the adhesion of the tension-imparting insulating film and the structure of the external oxide type oxide film was investigated.
As an experimental material, a decarburized and annealed sheet of unidirectional silicon steel sheet with a thickness of 0.225 mm is coated with an annealing separator mainly composed of alumina, subjected to final annealing, and subjected to secondary recrystallization, resulting in a specular gloss. A unidirectional silicon steel plate was prepared. Next, a sample was prepared under conditions where a pretreatment for introducing a slight strain on the surface of the steel sheet was performed with a brush with silicon carbide abrasive grains and conditions where the pretreatment was not performed.
[0020]
Next, heat treatment was performed at various temperatures in a soaking time of 10 seconds in an atmosphere of nitrogen 25%, hydrogen 75%, and dew point-1 ° C. to form an external oxide oxide film mainly composed of silica. Finally, in order to form a tension-providing insulating film, a coating solution mainly composed of aluminum phosphate, chromic acid, and colloidal silica was applied and baked at 835 ° C. for 30 seconds in a nitrogen atmosphere. The film adhesion of the steel sheet thus prepared was examined.
[0021]
The film adhesion was evaluated by the area ratio (hereinafter referred to as the film remaining area ratio) of the part where the steel sheet and the film remained in close contact with each other when the sample was wound around a cylinder having a diameter of 20 mm. When the adhesion was poor and the film was completely peeled off, it was judged as 0%, and when the film adhesion was good and the film was not peeled off at all, it was judged as 100%. In the evaluation, the case where the film remaining area ratio was 90% or less was evaluated as x, the film was 95%, and the film was 100%.
[0022]
In addition, in order to investigate the structure of the external oxide type oxide film existing at the interface between the tension-imparting insulating film and the steel sheet, a sample was prepared by a concentrated ion beam method (hereinafter referred to as FIB method), and a transmission electron microscope (hereinafter referred to as an electron microscope). , Referred to as TEM). The FIB method is a technique for producing and collecting a flaky sample having a thickness of several μm from a desired position of a coated steel plate sample so that the coating having a thickness of several μm formed on the steel plate can be observed from the cross-sectional direction.
[0023]
When a thin film sample was prepared by the FIB method and the interface portion between the steel plate and the tension-imparting insulating film was examined by TEM, an external oxide oxide film mainly composed of silica was observed. In particular, for a sample in which a slight strain is introduced into the steel plate surface with an abrasive brush before forming an oxide film as an intermediate layer, in addition to an external oxide film oxide film, a film shape as shown in FIG. A granular oxide mainly composed of silica was observed, penetrating the oxide film and fitting into the tension-imparting insulating film side.
[0024]
Many such interface portions were observed, and the ratio of the granular oxide to the film-like oxide film (hereinafter referred to as the granular oxide area ratio) was calculated in the cross section. Further, the average film thickness of the external oxide film was also obtained. The results are summarized in Table 1.
[0025]
[Table 1]
From Table 1, it is as follows when the conditions which can ensure the adhesiveness of a tension | tensile_strength imparting insulating film are calculated | required.
First, under the conditions of the heat treatment temperature of 500 ° C. and the conditions of Sample No. 1 and Sample No. 2 in which the thickness of the external oxide oxide film is 1 nm, the remaining film area ratio is as low as 10% and 20%, respectively. The film adhesion cannot be ensured regardless of the presence or absence of the pretreatment with the attached brush.
[0027]
On the other hand, in the conditions where the heat treatment temperature of Sample No. 3 to Sample No. 16 where the thickness of the external oxide oxide film is 2 nm or more is 600 ° C. to 1150 ° C., the film remaining area ratio is 90% or more, and the film adhesion generally Can be secured.
However, the pretreatment with a brush with abrasive grains is performed, and the granular oxide has good film adhesion under the condition that the cross-sectional area ratio of the granular oxide is 2% or more, but the pretreatment with the brush with abrasive grains is not performed. When the cross-sectional area ratio is 0% or 1%, even if the thickness of the external oxide film is large, the film adhesion is not necessarily perfect, and the film remaining area ratio is 90%. It was.
[0028]
In particular, when the thicknesses of the external oxide oxide films of Sample Nos. 12, 14, and 16 are 40 nm or more and the heat treatment temperature is 1000 ° C. or more, the film adhesion is remarkably good.
From Table 1, in order to completely secure the film adhesion of the tension-imparting insulating film, the thickness of the external oxide oxide film is 2 nm or more and the cross-sectional area ratio of the granular oxide is 2% or more. It is clear that this is essential. In order to form such a granular oxide together with a film-like oxide, a slight strain is introduced into the surface of the steel plate prior to the heat treatment for forming the outer oxide oxide film, and then the outer oxide oxide film is formed. It can be seen that the temperature must be 600 ° C. or higher, particularly preferably 1000 ° C. or higher.
[0029]
Next, as a steel plate pretreatment before forming the external oxide film, light pickling was performed in 1% nitric acid at room temperature for 10 seconds, and conditions similar to those in Table 1 were formed under the condition that fine irregularities were formed on the surface. Experiments and evaluations were performed according to the procedure. The results are shown in Table 2.
[0030]
[Table 2]
From Table 2, it is as follows when the conditions which can ensure the adhesiveness of a tension | tensile_strength imparting insulating film are calculated | required.
First, under the conditions of the heat treatment temperature of 500 ° C. and the conditions of Sample No. 1 and Sample No. 2 where the thickness of the external oxide oxide film is 1 nm, the remaining film area ratios are as low as 20% and 30%, respectively. The film adhesion cannot be ensured regardless of the presence or absence of surface micro-roughening treatment by washing.
[0032]
On the other hand, under the conditions where the heat treatment temperature of Sample No. 3 to Sample No. 16 in which the thickness of the external oxide oxide film is 2 nm or more is 600 ° C. to 1150 ° C., the film adhesion can be generally secured.
However, pretreatment with a brush with abrasive grains is carried out, and under conditions where the sectional area ratio of the granular oxide is 2% or more, the film adhesion is good, but the nitric acid pickling treatment is not performed, the granular oxide is small, That is, when the cross-sectional area ratio is 0% or 1%, even if the thickness of the external oxide oxide film is thick, the film adhesion is not necessarily perfect, and the film remaining area ratio is 90%. It became.
[0033]
In particular, when the thicknesses of the external oxide oxide films of Sample Nos. 12, 14, and 16 are 40 nm or more and the heat treatment temperature is 1000 ° C. or more, the film adhesion is remarkably good.
From the above, in order to ensure the film adhesion of the tension-imparting insulating film, the thickness of the external oxide oxide film is 2 nm or more and the cross-sectional area ratio of the granular oxide is 2% or more. Is essential. In order to form such a granular oxide together with a film-like oxide, fine irregularities are introduced on the surface of the steel plate prior to the heat treatment for forming the external oxide oxide film, and then the external oxide oxide film is formed. It can be seen that the temperature must be 600 ° C. or higher, particularly preferably 1000 ° C. or higher.
[0034]
As described above, the inventors consider the mechanism of the film adhesion as follows, because the film thickness of the external oxide oxide film and the cross-sectional area ratio occupied by the granular oxide have a great influence.
First, the relationship between the temperature and the film thickness in the external oxide film will be described.
Adhesion between the steel sheet and the tension-imparting insulating film is determined by an external oxidation type oxide film formed at the interface between the two. In general, it is said that an external oxide oxide film grows when metal atoms diffuse from the steel to the surface and react with an oxidizing gas on the surface. Therefore, the growth rate of the oxide film is determined by the diffusion rate of atoms. Atomic diffusion is enhanced by thermal energy. Therefore, the higher the temperature, the more the atom diffusion is promoted and the outer oxide oxide film grows more.
[0035]
Due to such a mechanism, the growth of the external oxide type oxide film is not sufficient under conditions where the heat treatment temperature is as low as 500 ° C., so that the film adhesion is not sufficient. On the other hand, when the heat treatment temperature is 600 ° C. or higher, sufficient external oxidation is achieved. Since the type oxide film grows, the film adhesion is good. Further, at 1000 ° C. or higher, the oxide film grows more easily, so the film adhesion is considered to be extremely good.
[0036]
It can be understood from the result of the measurement of the thickness of the external oxide film using a transmission electron microscope that such an assumption is valid. That is, when the film thickness is 1 nm and the growth of the external oxide oxide film is not sufficient and the heat treatment temperature is 500 ° C., the adhesion of the tension-imparting insulating film is poor, whereas the film thickness of 2 nm or more The film adhesion is good under conditions where the oxide type oxide film is grown and the heat treatment temperature is 600 ° C. or higher.
[0037]
The details of the mechanism by which granular oxide is formed in the external oxide film are still unclear, but before forming the external oxide film, a slight distortion can be obtained by wiping the steel plate surface with a brush containing abrasive grains. The inventor says that the oxide film will grow especially from such micro-strain and micro-unevenness as a starting point, and will develop into a granular form by introducing micro-unevenness by pickling or by pickling Are thinking.
[0038]
Next, the relationship between the steel sheet adhesion of the tension-imparting insulating film and the cross-sectional area ratio of the granular oxide will be described.
The application of tension to the steel sheet by the tension-imparting insulating film is caused by the difference in thermal expansion coefficient between the tension-imparting insulating film and the steel sheet. At this time, a great amount of stress is generated at the interface between the tension-imparting insulating film and the steel plate. It is the external oxide type oxide film that can withstand this stress and ensure the adhesion between the steel sheet and the tension-imparting insulating film.
[0039]
The inventors speculate that the granular oxide may have an effect on such stress resistance. That is, the granular oxide is generated in a form that penetrates the film thickness of the external oxidation type oxide film, so that when the tension imparting insulating film is formed, the granular oxide is inserted into the tension imparting insulating film side. It is presumed that strong stress resistance is manifested by the form, so-called wedge shape.
[0040]
When the ratio of the granular oxide to the external oxide film is 2% or more, it can withstand the stress, but when the ratio of the granular oxide is less than 2%, the external oxide film is formed by the tension-imparting insulating film. We cannot withstand the pressing stress and think that the tension-imparting insulating film may peel off.
The upper limit of the thickness of the external oxide film is not particularly limited in terms of film adhesion, but when the thickness exceeds 500 nm, the space factor, which is an important indicator in transformers, deteriorates due to an increase in nonmagnetic portions. Therefore, it is desirable that the thickness be 500 nm or less.
[0041]
【Example】
Example 1
After decarburization annealing was performed on a cold-rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.225 mm and a Si concentration of 3.30% by mass, the surface oxide layer was pickled in a mixed solution of ammonium fluoride and sulfuric acid. And dissolved and removed. Subsequently, the alumina powder was applied by an electrostatic coating method, and finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere. The surface of the secondary recrystallized unidirectional silicon steel sheet thus prepared is free of inorganic minerals and has a specular gloss.
[0042]
With respect to this steel plate, a product (Example) in which the surface of the steel plate was wiped with a brush with alumina abrasive grains and a sample in which the surface was not wiped (Comparative Example) were prepared. Then, an external oxide oxide film was formed by performing heat treatment at a temperature of 900 ° C. in an atmosphere of 50% nitrogen, 50% hydrogen, and a dew point of −10 ° C.
Next, a mixed liquid consisting of 50 ml of magnesium phosphate aqueous solution with a concentration of 50%, 66 ml of a colloidal silica aqueous dispersion with a concentration of 30%, and 5 g of chromic anhydride was applied to the prepared steel sheet and baked at 850 ° C. for 30 seconds. Then, a tension-imparting insulating film was formed.
[0043]
About the unidirectional silicon steel plate with an insulating film prepared in this way, the cross section was investigated by FIB-TEM method, and the cross-sectional area ratio of the granular oxide was calculated from the average film thickness of the external oxide type oxide film. Moreover, the film adhesion was evaluated by the film remaining area ratio when the sample was wound around a cylinder with a diameter of 20 mm. The results are shown in Table 3.
[0044]
[Table 3]
From Table 3, wiping with a brush with abrasive grains was performed, and wiping with a brush with abrasive grains was performed, compared to a comparative example in which the granular oxide area ratio was 1% and the film remaining area ratio was 90%. It can be seen that the example in which the film residual area ratio is 95% and the film adhesion is 95% is better and better.
(Example 2)
Decarburized and annealed cold-rolled sheet for unidirectional silicon steel sheet with 0.225mm thickness and Si concentration of 3.35% by mass, and water slurry of annealing separator mainly composed of magnesia and bismuth chloride is applied to the surface. And dried. Then, finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere, and a unidirectional silicon steel sheet with a secondary recrystallization almost free of inorganic minerals on the surface was obtained. Subsequently, pickling was performed at 2% nitric acid at room temperature for 5 seconds to prepare a surface having minute irregularities (Example) and a surface not pickled (Comparative Example).
[0046]
Next, this steel sheet was heat-treated at a temperature of 1150 ° C. in an atmosphere of 25% nitrogen, 75% hydrogen, and dew point of −15 ° C. to form an external oxide oxide film mainly composed of silica. Next, a mixed liquid consisting of 50 ml of a 50% magnesium phosphate aqueous solution, 100 ml of a 20% colloidal silica aqueous dispersion and 5 g of anhydrous chromic acid was applied to the prepared steel sheet, and baked at 850 ° C. for 30 seconds to give tension. An insulating film was formed.
[0047]
About the unidirectional silicon steel plate with an insulating film prepared in this way, the adhesiveness of the insulating film was evaluated by the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm. The results are shown in Table 4.
[0048]
[Table 4]
From Table 4, pickling is carried out compared with the comparative example in which the pretreatment by pickling is not carried out and the granular oxide area ratio is 1% and the remaining film area ratio is 90%. It can be seen that the example having the rate of 95% has better film adhesion and is superior.
(Example 3)
Decarburization annealing is applied to a cold-rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.225 mm and a Si concentration of 3.25% by mass, and a water slurry of an annealing separator mainly composed of alumina is applied to the surface, followed by drying. did. Next, finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere, and a unidirectional silicon steel sheet having almost no inorganic mineral on the surface and having a secondary recrystallization having a specular gloss was obtained. With respect to this steel plate, a product (Example) in which the surface of the steel plate was wiped with a brush with silicon carbide abrasive grains (Example) and a product in which the steel plate was not wiped (Comparative Example) were prepared.
[0050]
Subsequently, heat treatment was performed at a temperature of 800 ° C. in an atmosphere of 30% nitrogen, 70% hydrogen, and a dew point of −2 ° C. to form an external oxide film. Next, a mixed liquid consisting of 50 ml of 50% aluminum phosphate aqueous solution, 100 ml of 20% colloidal silica aqueous dispersion and 5 g of anhydrous chromic acid was applied to the prepared steel sheet, and baked at 850 ° C. for 30 seconds to give tension. An insulating film was formed.
[0051]
About the unidirectional silicon steel plate with an insulating film prepared in this way, the film adhesion was evaluated by the film remaining area ratio when the sample was wound around a cylinder with a diameter of 20 mm. The results are shown in Table 5.
[0052]
[Table 5]
From Table 5, wiping with a brush with abrasive grains was performed, and wiping with a brush with abrasive grains was performed, as compared with a comparative example in which the granular oxide area ratio was 1% and the film remaining area ratio was 90% without wiping with a brush with abrasive grains. It can be seen that the example in which the film residual area ratio is 95% and the film adhesion is 95% is better and better.
Example 4
Decarburization annealing is applied to a cold rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.23 mm and a Si concentration of 3.30% by mass, and a water slurry of an annealing separator mainly composed of magnesia is applied to the surface, followed by drying. Then, finish annealing was performed in a dry hydrogen atmosphere at 1200 ° C. for 20 hours. A film mainly composed of forsterite is formed on the surface of the unidirectional silicon steel sheet that has been subjected to secondary recrystallization thus prepared.
[0054]
Next, pickling in a mixed solution of ammonium fluoride and sulfuric acid, dissolving and removing the surface film, and then chemically polishing in a mixed solution of hydrofluoric acid and hydrogen peroxide solution, there is no inorganic mineral on the steel sheet surface, and A steel sheet having a specular gloss was obtained.
With respect to this steel plate, alumina powder was projected (Example) and what was not introduced (Comparative Example) was produced by projecting alumina powder. Then, an external oxide oxide film was formed by performing heat treatment at a temperature of 1050 ° C. in an atmosphere of 50% nitrogen, 50% hydrogen, and a dew point of −8 ° C.
[0055]
Next, a mixed solution consisting of 100 ml of a 10% colloidal alumina dispersion, 10 g of amorphous alumina powder, 5 g of boric acid, and 200 ml of water is applied and baked at 900 ° C. for 30 seconds to form a tension-imparting insulating film. It was.
About the unidirectional silicon steel plate with an insulating film prepared in this way, the film adhesion was evaluated by the film remaining area ratio when the sample was wound around a cylinder with a diameter of 20 mm. The results are shown in Table 6.
[0056]
[Table 6]
From Table 6, the alumina powder is projected and the surface of the granular oxide is introduced as compared with the comparative example in which the alumina powder is not projected and the area ratio of the granular oxide is 1% and the remaining area ratio of the film is 90%. It can be seen that the example with the rate of 30% and the rate of remaining film area of 95% has better coating adhesion and is superior.
[0058]
【The invention's effect】
According to the present invention, it is possible to obtain a unidirectional silicon steel sheet having no inorganic mineral film with good film adhesion.
[Brief description of the drawings]
FIG. 1 is a diagram (micrograph) showing an embodiment of a granular external oxide mainly composed of silica.
Claims (8)
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001124473A JP3930696B2 (en) | 2001-04-23 | 2001-04-23 | Unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film and method for producing the same |
| EP02720582A EP1382717B1 (en) | 2001-04-23 | 2002-04-23 | Unidirectional silicon steel sheet excellent in adhesion of insulating coating film imparting tensile force |
| KR1020027017584A KR100553020B1 (en) | 2001-04-23 | 2002-04-23 | Unidirectional silicon steel sheet excellent in adhesion of insulating coating film imparting tensile force |
| CNB028013166A CN1263891C (en) | 2001-04-23 | 2002-04-23 | Unidirectional silicon steel sheet excellent in adhesion of insulating coating film imparting tensile force and its mfg. method |
| PCT/JP2002/004052 WO2002088424A1 (en) | 2001-04-23 | 2002-04-23 | Unidirectional silicon steel sheet excellent in adhesion of insulating coating film imparting tensile force |
| US10/312,643 US6713187B2 (en) | 2001-04-23 | 2002-04-23 | Grain-oriented silicon steel sheet excellent in adhesiveness to tension-creating insulating coating films and method for producing the same |
| DE2002621237 DE60221237T2 (en) | 2001-04-23 | 2002-04-23 | UNIDIRECTIONAL SILICON PLATE WITH EXCELLENT ADHESION OF PULL-ON TRANSDUCER OF INSULATING COATING |
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| JP2001124473A JP3930696B2 (en) | 2001-04-23 | 2001-04-23 | Unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film and method for producing the same |
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| 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 |
| JP3858302B2 (en) * | 1996-03-19 | 2006-12-13 | 日新製鋼株式会社 | Steel plate for heat treatment with excellent oxide scale adhesion |
| JPH1150227A (en) * | 1997-07-28 | 1999-02-23 | Mitsubishi Materials Corp | Formation of surface oxidized coating on ti alloy or machine parts made of ti alloy |
-
2001
- 2001-04-23 JP JP2001124473A patent/JP3930696B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020012667A1 (en) | 2018-07-13 | 2020-01-16 | 日本製鉄株式会社 | Base sheet for grain-oriented electrical steel sheets, grain-oriented silicon steel sheet that serves as material for base sheet for grain-oriented electrical steel sheets, method for producing base sheet for grain-oriented electrical steel sheets, and method for producing grain-oriented electrical steel sheets |
| KR20210018933A (en) | 2018-07-13 | 2021-02-18 | 닛폰세이테츠 가부시키가이샤 | A grain-oriented electrical steel sheet, a grain-oriented silicon steel sheet used as a material for a grain-oriented electrical steel sheet, a method for producing a grain-oriented electrical steel sheet, and a method for producing a grain-oriented electrical steel sheet |
| US11884988B2 (en) | 2018-07-13 | 2024-01-30 | Nippon Steel Corporation | Base sheet for grain-oriented electrical steel sheet, grain-oriented silicon steel sheet which is used as material of base sheet for grain-oriented electrical steel sheet, method of manufacturing base sheet for grain-oriented electrical steel sheet, and method of manufacturing grain-oriented electrical steel sheet |
| WO2020149349A1 (en) | 2019-01-16 | 2020-07-23 | 日本製鉄株式会社 | Grain-oriented electromagnetic steel sheet and method for manufacturing same |
| KR20210111281A (en) | 2019-01-16 | 2021-09-10 | 닛폰세이테츠 가부시키가이샤 | Grain-oriented electrical steel sheet and its manufacturing method |
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