JP3882103B2 - Low iron loss unidirectional electrical steel sheet with tension-applying anisotropic coating - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、変圧器や発電器の鉄心等に利用される方向性電磁鋼板に関し、特に該鋼板の表面に被成する張力付与型被膜に張力付与異方性を付加することによって、鉄損特性の一層の改善を図ろうとするものである。
【０００２】
【従来の技術】
Siを含有し、かつ結晶方位が（１１０）〔００１〕方位に配向した方向性電磁鋼板は、優れた軟磁気特性を有することから商用周波数域での各種鉄心材料として広く用いられている。かかる電磁鋼板において特に重要な特性は、一般に50Hzの周波数で 1.7Ｔに磁化させた場合の損失であるＷ17/50 (W/kg)で表わされるところの鉄損が低いことである。
【０００３】
鉄損のうち、渦電流損（Ｗe ）を低減するのに有効な方法としては、Siを含有させて電気抵抗を高める方法、鋼板板厚を薄くする方法、さらには結晶粒径を低減する方法などが、一方ヒステリシス損（Ｗh ）を低減する方法としては、圧延方向に＜００１＞軸を高度に揃える方法が知られている。
このうち、Siを多量に含有させる方法は、飽和磁束密度の低下を招き鉄心のサイズ拡大の原因になるため、自ずから限界があった。
また、結晶方位を揃える方法も、すでに磁束密度Ｂ8 にして1.96Ｔや1.97Ｔという優れた値の製品が得られており、これ以上の改善の余地は少なくなっている。
さらに、製品板厚を減少する方法にしても、過度に薄い板厚の製品は圧延が困難であることから、工業的には現実的ではない。
【０００４】
その他、鉄損の低減に有効な方法として、鋼板に張力を付加する方法が知られていて、工業的には、鋼板より熱膨張係数の小さい材質からなる被膜を被成することによって、鋼板に対して張力を付与している。
すなわち、最終的に結晶方位を揃える２次再結晶と鋼板の純化を兼ねる最終仕上焼鈍工程で、鋼板表面の酸化物（シリカを主体とする）と鋼板表面に塗布した焼鈍分離剤（マグネシアを主成分とする）とが反応してフォルステライト (Mg2SiO4)を主成分とする被膜が形成されるが、この被膜は鋼板に与える張力が大きく、鉄損低減に効果がある。さらに、この張力効果を増大するために、上記したフォルステライト質被膜上に、低熱膨張性のコーティング（張力付与型の絶縁コーティング）を上塗りして、製品とすることが一般的である。
【０００５】
現在、フォルステライト被膜を有する方向性電磁鋼板に適用される張力付与型の絶縁コーティングとしては、Alやアルカリ土類金属のリン酸塩とコロイダルシリカ、無水クロム酸またはクロム酸塩を主成分とした処理液を塗布し、焼付けることによって形成されるものが多い。この絶縁コーティングによる張力付与の機構は、コロイダルシリカに代表される地鉄より熱膨張係数の小さい無機質を大量に含有する被膜を高温で焼付けることにより、地鉄と絶縁コーティングとの熱膨張差に基づいて、常温では鋼板に張力が付与される現象を利用している。
この方法で形成される絶縁被膜は、鋼板に対する張力付与効果が大きく、鉄損低減に極めて有効である。かかる絶縁被膜の代表的形成方法については、例えば特公昭53−28375 号公報や特公昭56−52117 号公報等に開示されている。
【０００６】
【発明が解決しようとする課題】
さて、鋼板と被膜との熱膨張係数差を利用して鋼板に張力を付与する場合、その張力値σは次式(1) で表されることが知られている（例えば特許第2664323 号公報）。
σ＝２Ｅc ・Ａc （Ｔ−Ｔ0 ）（αm −αc ）÷Ａm --- (1)
ここで、Ｅc ：被膜のヤング率
Ａc , Ａm ：被膜、鋼板の断面積
Ｔ：被膜の被成温度（軟化温度）
Ｔ0 ：測定温度（室温）
αc , αm ：被膜、鋼板の熱膨張係数
上掲式(1) に従えば、被膜のヤング率が高く、熱膨張係数が鋼板のそれと比較して小さいほど、張力値σは大きくなる。
しかしながら、現行以上に被膜のヤング率や熱膨張係数を変更しても、所望の低鉄損は得られなかった。
【０００７】
以下、この理由について述べる。
フォルステライトを主成分とする鉱物質の一次被膜にしても、上塗りの低熱膨張性の張力付与型コーティングにしても、被膜が発生させる応力は２次元的には等方的であり、面内のすべての方向に一様に張力を付与する。これらの被膜を鋼板に被成することによって磁区細分化効果が発揮され、鉄損値が低下するのは、２次再結晶した方向性電磁鋼板の結晶が圧延方向に対し、（１１０）〔００１〕方位に集積しているためである。
なぜなら、ほぼ単結晶に近いほど方位集積している方向性電磁鋼板は、圧延方向には＜１００＞軸、圧延方向と直角方向には＜１１０＞軸を持つ結晶群から成っている。Fe等の体心立方格子を有する金属は一般的に＜１００＞方位のヤング率が最も小さい。下記のヤング率の定義式(2) で示されるように、同一の応力σが付加された場合、ヤング率が小さいほど物質の変形量は大きくなる。
付加応力σ＝ヤング率Ｅ×変形量ΔＬ --- (2)
【０００８】
従って、方向性電磁鋼板に対して一様な応力を付与した場合であっても、特に圧延方向に最も伸張変形する。圧延方向に張力が加わった場合、圧延方向とほぼ平行な磁区は細分化され、鉄損値は低減する。逆に圧延方向と直角に張力を付与した場合には、磁区パターンは乱れたり消失したりして、鉄損値の増大を招く。
しかしながら、フォルステライトや上塗りコーティング等、等方的に張力を付与する被膜でも、上述したように鋼板自身の変形に対する異方性から圧延方向への張力効果が最大となるので、鉄損値が低減するのである。
【０００９】
前掲式(1) から明らかなように、被膜の膜厚を増加させたり、ヤング率を高めたり、熱膨張係数を小さくすることによって、付与応力を増大させることは可能である。
しかしながら、この方法では同時に磁区細分化に有害な圧延方向と直角方向への張力成分も増加するため、等方的な性質を有する被膜の各種因子を単に変更するだけでは、鉄損低減効果は飽和し、現状以上の鉄損低減効果は得られない。
上記したような理由により、鋼板への張力付与による鉄損低減技術には、新しい発展が近年認められなかったのである。
【００１０】
【課題を解決するための手段】
そこで、発明者らは、上記の限界を打破すべく種々検討を加えた結果、被膜自身に張力付与異方性を付加するという全く新しい着想を得た。
すなわち、鉄損低減に有害な圧延方向と直角方向への張力付与効果を低減し、より有効な圧延方向への張力付与を増加させるべく鋭意研究を進めた結果、自身が張力付与異方性を有する被膜を新たに開発し、本発明を完成させるに至ったのである。
【００１１】
すなわち、 本究明の要旨構成は次のとおりである。
１．方向性電磁鋼板の表面に被成する張力付与型被膜について、その鋼板圧延方向と平行方向における被膜断面積を、鋼板圧延方向と直角方向にわたって反復して変化させることを特徴とする張力付与異方性被膜を有する低鉄損一方向性電磁鋼板。
【００１２】
２．鋼板圧延方向と平行方向に線状溝を所定の間隔を隔てて反復して形成した鋼板の表面に、張力付与型被膜を被成したことを特徴とする上記１記載の低鉄損一方向性電磁鋼板。
【００１３】
３．平滑化した鋼板の表面に、鋼板圧延方向と平行に所定の間隔を隔てて反復して形成した線状溝を有する張力付与型被膜を被成したことを特徴とする上記１記載の低鉄損一方向性電磁鋼板。
【００１４】
４．平滑化した鋼板の表面に、鋼板圧延方向と平行に、線状の張力付与型被膜を所定の間隔を隔てて反復して被成したことを特徴とする上記１記載の低鉄損一方向性電磁鋼板。
【００１５】
５．張力付与型被膜における圧延方向張力の被膜有効厚みをｔ RD 、圧延直角方向張力の被膜有効厚みをｔ TD としたとき、これらの比がｔ RD ／ｔ TD ＞１を満足することを特徴とする上記１〜４のいずれかに記載の低鉄損一方向性電磁鋼板。
【００１６】
【発明の実施の形態】
以下、本発明について具体的に説明する。
Si：３mass％を含有する最終仕上げ焼鈍済み方向性電磁鋼板（板厚：0.23mm）のフォルステライト被膜に、圧延方向と平行にレーザー照射により溝幅：10μm、深さ：２μm の線状溝を形成した。 この時溝の間隔は20μm とした。その後、コロイダルシリカとリン酸マグネシウムを主成分とする張力付与型の絶縁被膜を片面当たり 8.0 g/m2 被成した。また、比較のため、圧延直角方向に同様の線状溝を形成させた素材と溝形成を行わずにそのまま絶縁被膜を被成した素材を作製した。
表１に、各素材の鉄損Ｗ17/50 について調査した結果を比較して示す。
また、鋼板の片面のみにレーザー照射による線状溝形成とその後の張力付与型コーティングを施し、試料の反り量から鋼板の圧延方向への付与応力を算出し、その値も併記した。
【００１７】
【表１】
同表に示したとおり、圧延方向と平行に線状溝を設けた試料（発明例）では、標準材と比較して、鉄損値、引張張力ともに向上した。
これに対し、圧延直角方向に線状溝を設けた試料（比較例）では、鉄損値および引張張力とも標準材よりも劣化した。
【００１９】
上記したとおり、発明例において鉄損値が向上した理由は、圧延直角方向に引張応力を発生させるためのコーティングの有効断面積が溝の形成により減少し、磁気特性に有害な圧延直角方向の引張応力が減少したことによるものと考えられる。
【００２０】
また、鋼板の反り量から圧延方向の付与張力を測定したところ、試料No.1では従来よりも増加していることが判明した。
この理由は、標準材である試料No.3と比較して張力コーティングの塗布量は同じなので、鋼板の圧延方向に付与される応力は同一なはずであるが、圧延直角方向の引張応力が減少した分だけ直角方向の変形量が減少するので、逆に圧延方向への伸張が容易となり、その結果、増加したためと考えられる。
なお、圧延方向の鋼板変形の増加量は、固体弾性論で良く知られたポアソン比を考慮して算出可能である。
【００２１】
例えば、圧延直角方向の被膜の有効断面積が半分になり、付与張力が半減した場合、方向性電磁鋼板では圧延方向の伸びは約10％程度増加すると予想される。従って、圧延方向の付与張力が同一でも、圧延直角方向の応力減少によって実際の圧延方向での変形量は大きくなり、磁気特性改善に対して相乗的な効果が生じたものと考えられる。
逆に、圧延直角方向に線状溝を形成した試料No.2の場合、磁気特性に有効な圧延方向の付与張力はその有効断面積の減少と共に低下してしまい、かつ圧延方向の伸張が減少した分だけ、圧延直角方向の引張変形量が増大し、その結果、一層の磁気特性の劣化を招いたものと考えられる。
【００２２】
すなわち、本発明の原理は、前掲式(1) で示される被膜の断面積Ａc を圧延方向と圧延直角方向とで変化させることによって、圧延方向の引張応力を圧延直角方向のそれよりも高めることにあり、その手段として、それぞれの方向の被膜の有効断面積を変化させるのである。
【００２３】
ここで、被膜の断面積について詳述する。
図１に、本発明の被膜断面を標準材のそれと比較して模式的に示す。
同図に示したとおり、標準材のように厚みが一様な被膜では、その断面積はどの方向でも同じであり、平均的な厚みによって決定される。
これに対し、本発明のように被膜断面積に異方性がある被膜の場合、例えば圧延方向の被膜応力は、圧延方向の断面積がＳRDであるから、式(1) においてＡc＝ＳRDとして算出される値となる。他方、圧延直角方向の被膜応力を考えた場合、直角方向の厚みは大きく変動し厚い部分と薄い部分が混在しているが、応力に寄与する断面積は応力方向に投影したときの最小面積ＳTDであり、それより厚い箇所はいわば被膜応力には寄与しない無駄な部分と見なすことができる。
【００２４】
実際の被膜有効断面積は、図２に示すように、その有効厚みを計測しれやれば良い。
例えば、一方向に線状溝を設けたような被膜の場合、圧延方向張力の被膜有効厚みｔRDはコーティングの塗布量と密度から算出したり、断面積SEM 観察などで直接計測することが可能である。
また、圧延直角方向張力の被膜有効厚みｔTDは、 ｔRD−1/2 Ryで表せる。 ここで、Ry（圧延直角方向) は、表面粗さを表すJIS の最大高さRyのことであり、 疵と見なされるような並外れて高い山および低い谷がない部分から基準長さだけ抜き取って計測された値である。
張力付与型被膜の最表面に凹凸を設けて張力異方性を発生させた場合にはその表面を、 また下地のフォルステライト膜に線状溝等を設けて、 その形状を転写する形で異方性を持たせた場合には、 張力付与型被膜のみを除去した後にレプリカであるフォルステライト膜の形状を粗度計等で計測してやれば良い。
【００２５】
圧延方向の被膜応力を決定する有効断面積ＳRDが、圧延直角方向の被膜応力を決定する有効断面積ＳTDより大きければ、式(1) に基づいて圧延方向の引張応力が圧延直角方向のそれよりも大きな張力付与型被膜を得ることができる。従って、例えば図１中で標準材と発明材に等量の張力付与型コートを塗布、被成した場合、両者のＳRDは同一であり、ＳTDだけが発明材で小さくなる。
【００２６】
上記の例は、最終仕上げ焼純時に形成されるフォルステライト膜に線状溝を設け、その上に張力付与型のコーティングを被成することで間接的にコーティングの被膜断面積に異方性を持たせた場合であるが、直接コーティング自身に線状溝を設けたり、コーティングを線状に塗布したりして、その断面積に異方性を持たせることも可能である。また、仕上げ焼鈍後にフォルステライト被膜を有さない鋼板表面に対して線状溝を形成させることをも可能である。
【００２７】
また、被膜の有効断面積に異方性を持たせる手段としては、溝等を形成させるのが最も簡便であるが、これだけに限定されるものではない。なお、溝等についても、圧延方向と平行に形成するのが最も有効と考えられるが、磁気特性等を考慮して圧延方向に対して斜めに線状あるいは点線状に溝やピットを形成しても構わない。要は、張力付与型コーティングの圧延方向の引張応力値が、圧延直角方向のそれを上回るような被膜断面が得られるパターンであれば良い。
また、溝等を形成させる手段としては、レーザー照射を始めとして、エメリー研磨紙を鋼板表面に押しつけて研削するヘアライン処理のような手法も有効であるし、フォルステライト被膜形成の一次原料である一次再結晶焼純時に生成するシリカを主体とする酸化物膜を線状に除去するなどして、フォルステライト被膜の断面積に異方性を持たせる方法も有効な手段である。
さらに、鋼板自身に圧延ロール等で断面異方性を持たせることも、鋼板の圧延方向への伸張がより容易になる形状であれば有効である。
【００２８】
以上述べたとおり、本発明では、圧延方向張力の被膜有効断面積ＳRDを圧延直角方向張力の被膜有効断面積ＳTDよりも大きくする、換言すれば圧延方向張力の被膜有効厚みｔRDを圧延直角方向張力の被膜有効厚みｔTDよりも大きくすることによって、圧延方向における引張応力を増大させ、効果的に磁区を細分化して鉄損の一層の低減を図るのである。
【００２９】
次に、本発明で対象とする電磁鋼板の好適成分組成について説明する。
本発明で対象とする電磁鋼板については、その成分組成が特に限定されることはないが、Siを 1.5〜7.0 mass％、Mnを0.03〜2.5 mass％程度含有させることが望ましい。
ここに、SiやMnは、製品の電気抵抗を高め、鉄損を低減するのに有効な成分であるが、Siは 7.0mass％を超えると硬度が高くなって製造や加工が困難となり、一方Mnは 2.5mass％を超えると熱処理時にγ変態を誘起して磁気特性を劣化させるおそれがある。
また、鋼中には、上記の元素の他に、方向性電磁鋼板の製造に適するインヒビター成分として知られている、Al, Ｂ, Bi, Sb, Mo, Te, Sn, Ｐ, Ge, As, Nb,Cr, Ti, Cu, Pb, ZnおよびInなどの公知元素を単独または複合して含有させることができる。
なお、Ｃ、Ｓ、Ｎなどの不純物はいずれも、磁気特性上有害な作用があり、特に鉄損を劣化させるので、それぞれＣ：0.003 mass％以下、Ｓ：0.002 mass％以下、Ｎ：0.002 mass％以下程度に抑制することが望ましい。
【００３０】
張力付与型の絶縁コーティングの種類としては、従来からフォルステライト被膜を有する方向性電磁鋼板に用いられているリン酸塩−コロイダルシリカ−クロム酸系のコーティング等が、その効果およびコスト、均一処理性などの点から好適である。
コーティングの厚みについては、張力付与効果や占積率、被膜密着性等の点から 0.3〜10μm 程度とするのが好ましい。
また、張力コーティングとしては、これ以外にも特開平６−65754 号公報、特開平６−65755 号公報および特開平６−299366号公報などで提案されているホウ酸−アルミナ等の酸化物系被膜を適用することも可能である。
【００３１】
さらに、圧延方向に初めからより大きな張力付与効果をもたらすような、被膜自身が張力異方性を有するものであればなおさら都合がよい。圧延方向により大きな張力付与効果をもたらす被膜としては、前掲式(1) より明らかなように、ヤング率や熱膨張係数に異方性を持つものでも良く、圧延方向のヤング率が圧延直角方向のそれよりも大きかったり、逆に熱膨張係数が低いものであっても構わない。。
また、被膜のマトリックスは等方的な性質を有するものであっても、繊維状の組織を含み、例えばそれらが圧延方向に平行になっていて、異方性を発揮するような被膜も有効である。
【００３２】
【実施例】
実施例１
Si：3.0 mass％を含有する最終板厚：0.20mmに圧延された冷延板に、線状溝を形成し、脱炭・一次再結晶焼鈍後、MgＯを主成分とする焼純分離剤を塗布してから、二次再結晶過程と純化過程を含む最終仕上げ焼純を施すことによって、フォルステライト被膜を有する方向性電磁鋼板を製造した。
このフォルステライト被膜に、粗さ＃600 のエメリー紙で圧延方向または圧延直角方向に研磨時の荷重を変えて線状に溝を形成した後、張力付与型コーティングとしてリン酸マグネシウム、コロイダルシリカおよびクロム酸マグネシウムを主成分とする水性処理液を塗布し、 800℃で焼き付けて、鋼板片面当たり約 6.0g/m2の厚さの被膜を形成させた。
コーティング被成後の断面SEM 観察から圧延方向と平行方向および直角方向のコーティングの有効断面積を厚みとして計測した。
また、各鋼板の鉄損値Ｗ17/50 を測定した。
得られた結果を表２に示す。
【００３３】
【表２】
同表から明らかなように、圧延方向と平行にエメリー研磨を行い、圧延直角方向のコーティング有効厚みを、圧延方向のそれよりも減少させた発明例（No.1,２）はいずれも、何の処理も行わなかった標準材（No.5）と比較して鉄損値の改善が見られた。
これに対し、圧延方向の被膜張力を決める有効厚みが直角方向のそれよりも小さい比較例（No.3, 4)では、鉄損値はむしろ劣化した。
【００３５】
実施例２
Si：3.0 mass％を含有する最終板厚：0.20mmに圧延された冷延板に、線状溝を形成し、脱炭・一次再結晶焼純後、MgＯを主成分とする焼純分離剤を塗布してから、二次再結晶過程と純化過程を含む最終仕上げ焼鈍を施すことによって、フォルステライト被膜を有する方向性電磁鋼板を製造した。
このフォルステライト被膜に、レーザー照射により、圧延方向または圧延直角方向に線状溝を形成させた。この時のビーム径は約２μm である。ついで、張力付与型コーティングとしてリン酸アルミニウムおよびコロイダルシリカを主成分とする水性処理液を塗布し、 850℃で焼き付けて、鋼板片面当たり約 5.0 g/m2の厚さの被膜を形成させた。
コーティング被成後の断面SEM 観察から圧延方向と平行方向および直角方向のコーティングの有効断面積を厚みとして計測し、その比を求めた。
また、各鋼板の鉄損値Ｗ17/50 を測定した。
得られた結果を表３に示す。
【００３６】
【表３】
同表から明らかなように、圧延方向と平行にレーザー照射を行い、圧延直角方向のコーティング有効厚みを減少させ、圧延方向と圧延直角方向の有効厚み比を１よりも大きくした発明例（No.1, ２）はいずれも、何の処理も行わなかった標準材（No.5）と比較して、圧延方向のコーティング張力が増加し、鉄損値が低下した。
これに対し、圧延直角方向にレーザー照射を行い、コーティングの有効厚み比が１よりも小さくなった比較例（No.3, 4)では、圧延方向のコーティング張力が減少し、鉄損値は劣化した。
【００３８】
【発明の効果】
かくして、本発明に従い、方向性電磁鋼板の表面に、磁区細分化に有効な圧延方向に平行な張力成分が、磁区細分化に有害な圧延直角方向の張力成分よりも大きくなるように、張力付与型被膜の被膜断面積に異方性を持たせることにより、従来に比べて格段に鉄損値を低減することができ、産業上極めて有用である。
【図面の簡単な説明】
【図１】 本発明の被膜断面を標準材と比較して示した図である。
【図２】 圧延方向張力の被膜有効厚みｔRDと圧延直角方向張力の被膜有効厚みｔTDの説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grain-oriented electrical steel sheet used for an iron core or the like of a transformer or a generator, and in particular, by adding tension-imparting anisotropy to a tension-imparting film formed on the surface of the steel sheet, iron loss characteristics. It is intended to further improve the above.
[0002]
[Prior art]
A grain-oriented electrical steel sheet containing Si and having a crystal orientation in the (110) [001] orientation is widely used as various iron core materials in a commercial frequency range because of having excellent soft magnetic properties. A particularly important characteristic in such an electrical steel sheet is that the iron loss expressed by W 17/50 (W / kg), which is a loss when magnetized to 1.7 T at a frequency of 50 Hz, is generally low.
[0003]
Among the iron losses, effective methods for reducing eddy current loss (We) include a method of increasing the electrical resistance by containing Si, a method of reducing the steel plate thickness, and a method of reducing the crystal grain size. On the other hand, as a method for reducing the hysteresis loss (Wh), a method of highly aligning the <001> axis in the rolling direction is known.
Among these methods, the method of containing a large amount of Si has a limit because it causes a decrease in the saturation magnetic flux density and causes an increase in the size of the iron core.
In addition, as for the method of aligning the crystal orientation, products having excellent values of 1.96 T and 1.97 T have already been obtained with the magnetic flux density B 8 , and there is little room for further improvement.
Furthermore, even if the method is to reduce the product plate thickness, a product having an excessively thin plate thickness is difficult to roll.
[0004]
In addition, as an effective method for reducing iron loss, a method of applying tension to a steel plate is known, and industrially, by applying a coating made of a material having a smaller thermal expansion coefficient than that of a steel plate, The tension is given to it.
In other words, in the final finishing annealing process, which is the final recrystallization that aligns the crystal orientation and the purification of the steel sheet, the oxide on the steel sheet surface (mainly silica) and the annealing separator applied to the steel sheet surface (mainly magnesia) To form a film mainly composed of forsterite (Mg 2 SiO 4 ), but this film has a large tension applied to the steel sheet and is effective in reducing iron loss. Furthermore, in order to increase this tension effect, it is common to make a product by overcoating a low thermal expansion coating (tension-providing insulating coating) on the forsterite film.
[0005]
Currently, the tension-providing insulation coating applied to grain-oriented electrical steel sheets with a forsterite film is mainly composed of Al and alkaline earth metal phosphates and colloidal silica, chromic anhydride or chromate. Many are formed by applying and baking a treatment liquid. The mechanism of tension application by this insulating coating is based on the difference in thermal expansion between the base iron and the insulating coating by baking a coating containing a large amount of inorganic material with a smaller coefficient of thermal expansion than that of the base iron represented by colloidal silica at a high temperature. Based on this, a phenomenon is used in which tension is applied to the steel sheet at room temperature.
The insulating coating formed by this method has a great effect of imparting tension to the steel sheet and is extremely effective in reducing iron loss. A typical method for forming such an insulating film is disclosed in, for example, Japanese Patent Publication No. 53-28375 and Japanese Patent Publication No. 56-52117.
[0006]
[Problems to be solved by the invention]
Now, when tension is applied to a steel sheet using the difference in thermal expansion coefficient between the steel sheet and the coating, it is known that the tension value σ is expressed by the following equation (1) (for example, Japanese Patent No. 2664323) ).
σ = 2E c · A c (T−T 0 ) (α m −α c ) ÷ A m --- (1)
Here, E c : Young's modulus of the coating A c , Am : coating, cross-sectional area of the steel sheet T: coating temperature (softening temperature) of the coating
T 0 : Measurement temperature (room temperature)
α c , α m : Coefficient of thermal expansion of coating and steel sheet According to the above equation (1), the Young's modulus of the coating is higher, and the smaller the thermal expansion coefficient is that of the steel sheet, the greater the tension value σ.
However, even if the Young's modulus and thermal expansion coefficient of the coating were changed more than the current level, the desired low iron loss could not be obtained.
[0007]
The reason for this will be described below.
Whether it is a primary coating for minerals based on forsterite or a top-coated low thermal expansion tension-imparting coating, the stress generated by the coating is two-dimensionally isotropic. Apply tension uniformly in all directions. By applying these coatings on the steel sheet, the magnetic domain refinement effect is exhibited, and the iron loss value decreases because the crystal of the secondary recrystallized grain-oriented electrical steel sheet is (110) [001] in the rolling direction. This is because they are accumulated in the direction.
This is because the grain-oriented electrical steel sheet, whose orientation is accumulated as it is closer to a single crystal, consists of a group of crystals having a <100> axis in the rolling direction and a <110> axis in a direction perpendicular to the rolling direction. A metal having a body-centered cubic lattice such as Fe generally has the smallest Young's modulus in the <100> orientation. As shown in the following definition formula (2) of Young's modulus, when the same stress σ is applied, the amount of deformation of the material increases as the Young's modulus decreases.
Applied stress σ = Young's modulus E × deformation amount ΔL --- (2)
[0008]
Accordingly, even when uniform stress is applied to the grain-oriented electrical steel sheet, it is most stretched and deformed particularly in the rolling direction. When tension is applied in the rolling direction, the magnetic domains substantially parallel to the rolling direction are subdivided and the iron loss value is reduced. Conversely, when tension is applied at right angles to the rolling direction, the magnetic domain pattern is disturbed or disappears, leading to an increase in iron loss value.
However, even for coatings that apply isotropic tension, such as forsterite and top coating, as described above, the tension effect in the rolling direction is maximized from the anisotropy of the deformation of the steel sheet itself, so the iron loss value is reduced. To do.
[0009]
As apparent from the above formula (1), the applied stress can be increased by increasing the film thickness of the coating, increasing the Young's modulus, or decreasing the thermal expansion coefficient.
However, this method also increases the tensile component in the direction perpendicular to the rolling direction, which is harmful to magnetic domain fragmentation, so that the effect of reducing iron loss is saturated simply by changing various factors of the film having isotropic properties. However, the iron loss reduction effect beyond the current level cannot be obtained.
For the reasons described above, new developments have not been recognized in recent years in the technology for reducing iron loss by applying tension to a steel sheet.
[0010]
[Means for Solving the Problems]
Thus, the inventors have made various studies to overcome the above-mentioned limitations, and as a result, have obtained a completely new idea of adding tension imparting anisotropy to the coating itself.
That is, as a result of diligent research to reduce the effect of applying tension in the direction perpendicular to the rolling direction, which is harmful to iron loss reduction, and to increase the application of tension in the more effective rolling direction, A new coating was developed and the present invention was completed.
[0011]
That is, the summary of the present study is as follows.
1. A tension-applying anisotropy characterized by repetitively changing the cross-sectional area of the coating in the direction parallel to the rolling direction of the steel sheet over the direction perpendicular to the rolling direction of the steel sheet. Low iron loss unidirectional electrical steel sheet with a conductive coating.
[0012]
2. 2. The low iron loss unidirectionality according to 1 above, wherein a tension-imparting coating is formed on the surface of a steel sheet formed by repeatedly forming linear grooves at a predetermined interval in a direction parallel to the rolling direction of the steel sheet. Electrical steel sheet.
[0013]
3. 2. The low iron loss according to 1 above, wherein a tension-imparting film having linear grooves formed repeatedly at a predetermined interval in parallel with the rolling direction of the steel sheet is formed on the surface of the smoothed steel sheet. Unidirectional electrical steel sheet.
[0014]
4). 2. The low iron loss unidirectionality according to 1 above, wherein a linear tension-imparting coating is formed repeatedly on the surface of the smoothed steel sheet in parallel with the rolling direction of the steel sheet at a predetermined interval. Electrical steel sheet.
[0015]
5). When a coating effective thickness of the rolling direction tension definitive in tension-imparting coating t RD, a coating effective thickness of the perpendicular to the rolling direction tension was t TD, and characterized in that these ratios satisfies t RD / t TD> 1 The low iron loss unidirectional electrical steel sheet according to any one of 1 to 4 above.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described.
Si: 3% by mass final finish annealed grain-oriented electrical steel sheet (thickness: 0.23mm) forsterite film with a groove width: 10μm and depth: 2μm by laser irradiation parallel to the rolling direction Formed. At this time, the groove interval was 20 μm. Thereafter, a tension-imparting insulating film composed mainly of colloidal silica and magnesium phosphate was applied to 8.0 g / m 2 per side. For comparison, a material in which similar linear grooves were formed in the direction perpendicular to the rolling and a material in which an insulating coating was directly formed without forming the grooves were produced.
Table 1 shows a comparison of the results of investigation on the iron loss W 17/50 of each material.
Moreover, linear groove formation by laser irradiation and subsequent tension imparting type coating were applied to only one side of the steel sheet, and the applied stress in the rolling direction of the steel sheet was calculated from the amount of warpage of the sample, and the value was also shown.
[0017]
[Table 1]
As shown in the table, in the sample (invention example) provided with linear grooves parallel to the rolling direction, both the iron loss value and the tensile tension were improved as compared with the standard material.
On the other hand, in the sample (comparative example) provided with linear grooves in the direction perpendicular to the rolling, both the iron loss value and the tensile tension were deteriorated as compared with the standard material.
[0019]
As described above, the reason why the iron loss value is improved in the invention example is that the effective cross-sectional area of the coating for generating tensile stress in the perpendicular direction of rolling is reduced by the formation of grooves, and the tensile force in the perpendicular direction of rolling, which is harmful to magnetic properties, is reduced This is thought to be due to the decrease in stress.
[0020]
Moreover, when the applied tension in the rolling direction was measured from the amount of warpage of the steel sheet, it was found that Sample No. 1 had an increase compared to the prior art.
The reason for this is that the applied amount of tension coating is the same as sample No. 3 which is a standard material, so the stress applied in the rolling direction of the steel sheet should be the same, but the tensile stress in the direction perpendicular to the rolling is reduced. The amount of deformation in the perpendicular direction is reduced by that amount, and conversely, it is easy to stretch in the rolling direction, resulting in an increase.
Note that the amount of increase in deformation of the steel sheet in the rolling direction can be calculated in consideration of the Poisson's ratio, which is well known in the solid elasticity theory.
[0021]
For example, when the effective sectional area of the coating in the direction perpendicular to the rolling is halved and the applied tension is halved, the elongation in the rolling direction is expected to increase by about 10% in the grain-oriented electrical steel sheet. Therefore, even if the applied tension in the rolling direction is the same, the amount of deformation in the actual rolling direction increases due to the stress reduction in the direction perpendicular to the rolling, and it is considered that a synergistic effect has been produced for the improvement of the magnetic properties.
Conversely, in the case of sample No. 2 in which linear grooves are formed in the direction perpendicular to the rolling direction, the effective tension in the rolling direction for the magnetic properties decreases as the effective cross-sectional area decreases, and the elongation in the rolling direction decreases. Therefore, it is considered that the amount of tensile deformation in the direction perpendicular to the rolling increases, and as a result, the magnetic properties are further deteriorated.
[0022]
That is, the principles of the present invention, by changing the cross-sectional area A c of the coating represented by the supra formula (1) in the rolling direction and the direction perpendicular to the rolling direction, increase than the rolling direction of the tensile stress in the direction perpendicular to the rolling direction In particular, the effective cross-sectional area of the coating in each direction is changed as the means.
[0023]
Here, the cross-sectional area of the coating will be described in detail.
FIG. 1 schematically shows a cross section of the coating of the present invention in comparison with that of a standard material.
As shown in the figure, in a film having a uniform thickness such as a standard material, the cross-sectional area is the same in any direction and is determined by the average thickness.
On the other hand, in the case of a film having an anisotropy in the film cross-sectional area as in the present invention, for example, the film stress in the rolling direction has a cross-sectional area in the rolling direction of SRD , so that A c = This is a value calculated as SRD . On the other hand, when the film stress in the direction perpendicular to the rolling is considered, the thickness in the right direction varies greatly, and a thick part and a thin part are mixed, but the cross-sectional area contributing to the stress is the minimum area S when projected in the stress direction. It is TD , and the thicker part can be regarded as a useless part that does not contribute to the film stress.
[0024]
As shown in FIG. 2, the actual effective cross-sectional area of the film may be measured by measuring its effective thickness.
For example, in the case of a film with linear grooves in one direction, the effective film thickness t RD of the rolling direction tension can be calculated from the coating amount and density of the coating, or directly measured by cross-sectional area SEM observation, etc. It is.
Also, the effective coating thickness t TD in the direction perpendicular to the rolling direction can be expressed as t RD −1/2 Ry. Here, Ry (the direction perpendicular to the rolling direction) is the JIS maximum height Ry representing the surface roughness, and is extracted by a reference length from a part that does not have extraordinarily high peaks and low valleys that are considered to be ridges. It is a measured value.
If tension anisotropy is generated by providing irregularities on the outermost surface of the tension-imparting film, the surface is different, and a linear groove is provided on the underlying forsterite film to transfer the shape. In the case of imparting anisotropy, the shape of the replica forsterite film may be measured with a roughness meter or the like after removing only the tension-imparting film.
[0025]
If the effective cross-sectional area S RD that determines the coating stress in the rolling direction is larger than the effective cross-sectional area S TD that determines the coating stress in the direction perpendicular to the rolling direction, the tensile stress in the rolling direction is A larger tension-imparting film can be obtained. Thus, for instance invention material coated with an equal amount of tension-imparting coating with standard material in FIG. 1, when form the, both S RD are the same, only the S TD is smaller in the invention material.
[0026]
In the above example, a linear groove is provided in the forsterite film formed at the time of final finish tempering, and a tension-imparting type coating is formed thereon to indirectly make the coating cross-sectional area anisotropic. In this case, it is possible to provide anisotropy in the cross-sectional area by providing a linear groove directly in the coating itself or by applying the coating in a linear shape. It is also possible to form linear grooves on the steel sheet surface that does not have a forsterite film after finish annealing.
[0027]
Further, as a means for imparting anisotropy to the effective cross-sectional area of the film, it is most convenient to form a groove or the like, but it is not limited to this. Note that it is considered most effective to form grooves and the like parallel to the rolling direction, but in consideration of magnetic properties, etc., grooves and pits are formed diagonally or linearly with respect to the rolling direction. It doesn't matter. In short, any pattern may be used as long as the tensile stress value in the rolling direction of the tension-imparting coating is higher than that in the direction perpendicular to the rolling.
In addition, as a means for forming grooves and the like, a technique such as laser irradiation, hairline processing for pressing emery abrasive paper against the steel sheet surface and grinding is also effective, and the primary material for forming forsterite film A method of giving anisotropy to the cross-sectional area of the forsterite film, for example, by removing the oxide film mainly composed of silica formed during recrystallization annealing into a linear shape is also an effective means.
Furthermore, it is effective to give the steel sheet itself cross-section anisotropy with a rolling roll or the like as long as the shape makes it easier to stretch the steel sheet in the rolling direction.
[0028]
As described above, in the present invention, the effective coating area S RD of the rolling direction tension is made larger than the effective coating area S TD of the normal direction tension of rolling, in other words, the effective coating thickness t RD of the rolling direction tension is rolled. By making the effective thickness t TD of the perpendicular tension larger than the effective coating thickness t TD , the tensile stress in the rolling direction is increased and the magnetic domain is effectively subdivided to further reduce the iron loss.
[0029]
Next, the suitable component composition of the electrical steel sheet which is the subject of the present invention will be described.
The component composition of the electrical steel sheet to be used in the present invention is not particularly limited, but it is desirable to contain Si in an amount of 1.5 to 7.0 mass% and Mn in an amount of 0.03 to 2.5 mass%.
Here, Si and Mn are effective components to increase the electrical resistance of the product and reduce iron loss. However, if Si exceeds 7.0 mass%, the hardness increases and manufacturing and processing become difficult. If Mn exceeds 2.5 mass%, γ transformation may be induced during heat treatment to deteriorate the magnetic properties.
In addition to the above elements, in steel, Al, B, Bi, Sb, Mo, Te, Sn, P, Ge, As, which are known as inhibitor components suitable for the production of grain-oriented electrical steel sheets Known elements such as Nb, Cr, Ti, Cu, Pb, Zn, and In can be contained alone or in combination.
Note that impurities such as C, S, and N all have harmful effects on magnetic properties, and particularly deteriorate iron loss. Therefore, C: 0.003 mass% or less, S: 0.002 mass% or less, and N: 0.002 mass, respectively. It is desirable to suppress to about% or less.
[0030]
The types of tension-imparting insulation coatings include phosphate-colloidal silica-chromic acid-based coatings that have been used for grain-oriented electrical steel sheets with a forsterite film. From the point of view, it is preferable.
The thickness of the coating is preferably about 0.3 to 10 μm from the viewpoint of tension imparting effect, space factor, film adhesion and the like.
In addition, as the tension coating, other oxide-based films such as boric acid-alumina proposed in JP-A-6-65754, JP-A-6-65755, JP-A-6-299366, etc. It is also possible to apply.
[0031]
Furthermore, it is even more convenient if the coating itself has a tension anisotropy that provides a greater tensioning effect in the rolling direction from the beginning. As is clear from the above equation (1), the coating film that provides a greater tensioning effect in the rolling direction may have anisotropy in Young's modulus and thermal expansion coefficient, and the Young's modulus in the rolling direction is perpendicular to the rolling direction. It may be larger than that or may have a low thermal expansion coefficient. .
In addition, even if the coating matrix has isotropic properties, it is also effective to include a fibrous structure, for example, a coating that exhibits anisotropy when they are parallel to the rolling direction. is there.
[0032]
【Example】
Example 1
Si: 3.0 mass% final plate thickness: Cold-rolled sheet rolled to 0.20 mm, linear grooves are formed, decarburized and primary recrystallization annealing, and then a pure separation agent mainly composed of MgO After the application, a grain-oriented electrical steel sheet having a forsterite film was manufactured by performing final finishing tempering including a secondary recrystallization process and a purification process.
The forsterite film is coated with emery paper with a roughness of # 600 to change the load during polishing in the rolling direction or in the direction perpendicular to the rolling direction to form linear grooves, and then a magnesium phosphate, colloidal silica and chromium as a tension-imparting coating. An aqueous treatment liquid mainly composed of magnesium acid was applied and baked at 800 ° C. to form a film having a thickness of about 6.0 g / m 2 per one side of the steel sheet.
From the cross-sectional SEM observation after coating, the effective cross-sectional area of the coating in the direction parallel to and perpendicular to the rolling direction was measured as the thickness.
Moreover, the iron loss value W 17/50 of each steel plate was measured.
The obtained results are shown in Table 2.
[0033]
[Table 2]
As is apparent from the table, any of the invention examples (Nos. 1 and 2) in which the emery polishing is performed in parallel with the rolling direction and the effective coating thickness in the direction perpendicular to the rolling direction is smaller than that in the rolling direction. The iron loss value was improved compared to the standard material (No. 5) which was not subjected to the above treatment.
On the other hand, in the comparative examples (No. 3 and 4) in which the effective thickness that determines the film tension in the rolling direction is smaller than that in the perpendicular direction, the iron loss value rather deteriorated.
[0035]
Example 2
Si: 3.0 mass% final thickness: Cold-rolled sheet rolled to 0.20 mm, linear grooves are formed, decarburized and primary recrystallized tempered, and then sintered separating agent mainly composed of MgO Then, the grain-oriented electrical steel sheet having a forsterite film was manufactured by performing final finishing annealing including a secondary recrystallization process and a purification process.
On this forsterite film, linear grooves were formed in the rolling direction or the direction perpendicular to the rolling direction by laser irradiation. The beam diameter at this time is about 2 μm. Next, an aqueous treatment liquid mainly composed of aluminum phosphate and colloidal silica was applied as a tension-imparting coating and baked at 850 ° C. to form a film having a thickness of about 5.0 g / m 2 per one side of the steel sheet.
From the cross-sectional SEM observation after coating, the effective cross-sectional area of the coating in the direction parallel to the rolling direction and the direction perpendicular to the rolling direction was measured as the thickness, and the ratio was determined.
Moreover, the iron loss value W 17/50 of each steel plate was measured.
The obtained results are shown in Table 3.
[0036]
[Table 3]
As is apparent from the table, laser irradiation was performed in parallel with the rolling direction, the effective coating thickness in the direction perpendicular to the rolling was reduced, and the effective thickness ratio in the rolling direction and the direction perpendicular to the rolling was greater than 1 (No. In both cases 1 and 2), the coating tension in the rolling direction increased and the iron loss value decreased as compared with the standard material (No. 5) which was not subjected to any treatment.
In contrast, in the comparative examples (No. 3 and 4) in which the effective thickness ratio of the coating was smaller than 1 by laser irradiation in the direction perpendicular to the rolling, the coating tension in the rolling direction decreased and the iron loss value deteriorated. did.
[0038]
【The invention's effect】
Thus, according to the present invention, tension is applied to the surface of the grain-oriented electrical steel sheet so that the tension component parallel to the rolling direction effective for magnetic domain fragmentation is larger than the tensile component in the perpendicular direction of rolling harmful to magnetic domain fragmentation. By giving anisotropy to the film cross-sectional area of the mold film, the iron loss value can be remarkably reduced as compared with the prior art, which is extremely useful industrially.
[Brief description of the drawings]
FIG. 1 is a view showing a cross section of a coating according to the present invention in comparison with a standard material.
FIG. 2 is an explanatory diagram of a coating effective thickness t RD of rolling direction tension and a coating effective thickness t TD of rolling perpendicular direction tension.
Claims (5)
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| JP2000123908A JP3882103B2 (en) | 2000-04-25 | 2000-04-25 | Low iron loss unidirectional electrical steel sheet with tension-applying anisotropic coating |
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| JP2000123908A JP3882103B2 (en) | 2000-04-25 | 2000-04-25 | Low iron loss unidirectional electrical steel sheet with tension-applying anisotropic coating |
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| JP5927754B2 (en) * | 2010-06-29 | 2016-06-01 | Ｊｆｅスチール株式会社 | Oriented electrical steel sheet and manufacturing method thereof |
| JP5593942B2 (en) * | 2010-08-06 | 2014-09-24 | Ｊｆｅスチール株式会社 | Oriented electrical steel sheet and manufacturing method thereof |
| JP5853352B2 (en) * | 2010-08-06 | 2016-02-09 | Ｊｆｅスチール株式会社 | Oriented electrical steel sheet and manufacturing method thereof |
| RU2540244C2 (en) * | 2010-08-06 | 2015-02-10 | ДжФЕ СТИЛ КОРПОРЕЙШН | Sheet from textured electric steel |
| JP6121086B2 (en) * | 2010-09-30 | 2017-04-26 | Ｊｆｅスチール株式会社 | Oriented electrical steel sheet and manufacturing method thereof |
| JP6624180B2 (en) * | 2016-10-18 | 2019-12-25 | Ｊｆｅスチール株式会社 | Grain-oriented electrical steel sheet and its manufacturing method |
| KR101919527B1 (en) * | 2016-12-23 | 2018-11-16 | 주식회사 포스코 | Oriented electrical steel sheet and method for manufacturing the same |
| CN109141717A (en) * | 2018-08-22 | 2019-01-04 | 三众机械设备（太仓）有限公司 | Broken magnetic Real time auto measure all-in-one machine |
| WO2021084793A1 (en) | 2019-10-31 | 2021-05-06 | Ｊｆｅスチール株式会社 | Electromagnetic steel sheet with insulation coating film |
| CN114555860B (en) * | 2019-10-31 | 2024-06-18 | 杰富意钢铁株式会社 | Electromagnetic steel sheet with insulating coating film |
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