JP3935664B2

JP3935664B2 - Treatment liquid for insulating film formation of electrical steel sheet and method

Info

Publication number: JP3935664B2
Application number: JP2000232866A
Authority: JP
Inventors: 克高橋
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Sumitomo Metal Industries Ltd
Priority date: 2000-08-01
Filing date: 2000-08-01
Publication date: 2007-06-27
Anticipated expiration: 2020-08-01
Also published as: JP2002047576A

Description

【０００１】
【発明の属する技術分野】
本発明は電磁鋼板の表面に絶縁皮膜を形成するための処理液および処理方法に関し、特に６価クロム等の有害な化合物を含まず、無方向性電磁鋼板用絶縁皮膜として従来は一般的であった重クロム酸塩系皮膜と同程度の焼付け温度で製造可能であり、かつ従来のリン酸塩系絶縁皮膜では得られない優れた耐水性を有し、特に1.0 g/m²以下の薄膜の絶縁皮膜を形成させる際の成膜性や密着性、耐水性に優れた、電磁鋼板の絶縁皮膜形成用処理液および処理方法に関する。
【０００２】
【従来の技術】
回転機や変圧器の鉄芯に使用される電磁鋼板の絶縁皮膜は、層間抵抗だけでなく、ユーザーにおける利便性 (打抜性、溶接性、耐熱性、かしめ性) 等の種々の特性が要求される。
【０００３】
現在一般に使用されている無方向性電磁鋼板用の絶縁皮膜は、以下の３種に大別される：
▲１▼耐熱性が重視され、歪取り焼鈍可能な無機皮膜、
▲２▼打抜き性と溶接性の両立を目指した、歪取焼鈍可能な、無機有機混合型の半有機皮膜、
▲３▼打抜き性が重視され、歪取り焼鈍不可の有機皮膜。
【０００４】
この中で汎用されているのは、歪取り焼鈍可能な、▲１▼および▲２▼の無機成分を含む絶縁皮膜である。特に、▲２▼の半有機皮膜が、無機皮膜に比較して打抜き性が格段に優れるため、主流となっている。
【０００５】
これまで上記▲１▼、▲２▼の絶縁皮膜中の無機成分を形成するための材料としては、重クロム酸塩が広く用いられてきた。重クロム酸塩を使用した絶縁皮膜は、６価クロムと多価金属塩を含む水溶液にエチレングリコールやグリセリンなどの有機還元剤を混合して得た処理液を電磁鋼板に塗布した後、加熱して塗膜を焼付け、６価クロムを３価クロムに還元して造膜させることにより形成される。焼付けは200 ℃から330 ℃の温度で１分以内の短時間で終了する。しかし、この絶縁皮膜の形成に用いる６価クロムは、毒性が強く、製造に携わる人間の健康を害する危険性が懸念される。また、形成された絶縁皮膜中に含まれる３価クロムは、６価クロムに比べると毒性は格段に低いが、完全に無害であるとは言えない。したがって、重クロム酸塩を用いる絶縁皮膜は、製造時および製品段階で、人間あるいは環境に僅かながらでも有害である可能性が否定できず、クロムを全く使用しないノンクロム型の絶縁皮膜が求められるようになってきた。
【０００６】
重クロム酸塩と同様に絶縁皮膜の形成に利用可能な無機成分として、リン酸塩がある。リン酸塩水溶液は、無機成分として数少ない造膜可能な系であり、かつ比較的安価に得られるため、従来より無機および半有機の絶縁皮膜用無機成分として検討されてきた (例えば、特公昭53−28375 号公報) 。
【０００７】
しかし、重クロム酸塩系の還元反応とは異なり、リン酸塩系の絶縁皮膜では、脱水反応による縮合の進行によりリン酸塩を高分子化し、皮膜の水不溶性を高めて造膜させる。そのため、耐水性の高い絶縁皮膜を形成するには、処理液の塗布後に、重クロム酸塩系処理液に比べてより高い温度（例、 300〜400 ℃）で焼き付けることが必要である。焼付け温度が高くなると、次に述べるような問題点がある。
【０００８】
▲１▼焼付けに必要な熱量および／または時間が増え、工業生産性・経済性の観点から不利である。
▲２▼汎用の半有機皮膜に含まれる樹脂の一部が熱分解して、皮膜の性能 (密着性、耐食性、打ち抜き性) が低下する恐れがある。耐熱性の高い樹脂を使用すれば、この問題は軽減されるが、そのような樹脂は高価であり、経済性の観点から工業的には採用しにくい。
【０００９】
リン酸塩系絶縁皮膜の例として、第一リン酸アルミニウムと有機エマルジョン樹脂とを含有し、エマルジョンの粒径を粗大化するか、他の成分 (架橋体樹脂粉体、アルコール、または有機酸金属塩) をさらに添加した処理液を用いて絶縁皮膜を形成することが、特開平５−78855 号、同６−330338号、同11−131250号および同11−152579号各公報に提案されている。
【００１０】
しかし、本発明者らが検討した結果、これらの各公報に記載された処理液では、特に膜厚が小さい (付着量約1.0 g/m²以下の) 薄膜の絶縁皮膜を形成する場合に、成膜性が不十分となり、焼付け温度を高くしないと、絶縁皮膜の耐水性や密着性が低下し、薄膜での性能に劣ることが判明した。薄膜の絶縁皮膜を設けた電磁鋼板は、特に溶接性が重視される用途や、自動化かしめ性が重視される用途などで、必要になってくる。
【００１１】
例えば、特開平11−131250号および同11−152579号各公報には、200 ℃または250 ℃で焼付けた皮膜の湿潤試験での耐食性の試験結果が示されており、錆の有無で耐食性を評価しているが、このような評価方法で錆が認められない場合でも、耐水性が十分であるとはいえない。錆が発生しなくても、絶縁皮膜が白化するだけでべたつきや滑り性低下といった性能劣化が認められるからである。
【００１２】
【発明が解決しようとする課題】
これまで無方向性電磁鋼板用の半有機皮膜としてリン酸塩系皮膜が使用されてきた例はいくつかあるものの、特に薄膜の場合には、重クロム酸塩系に比べて高い焼付温度が必要とされることから、ごく限られた用途にしか使用されていなかった。
【００１３】
クロムを使用せず、重クロム酸塩系なみの低い焼付け温度で成膜でき、その場合でも湿潤試験で白化に耐えるといった優れた耐水性や、密着性、絶縁性等の電磁鋼板用絶縁皮膜に必要な諸性能を有し、薄膜でも優れた成膜性を示す電磁鋼板の絶縁皮膜形成用処理液はこれまで皆無に等しかった。本発明は、このような処理液とそれを用いた電磁鋼板の絶縁皮膜形成方法とを提供するものである。
【００１４】
【課題を解決するための手段】
本発明者らは、リン酸塩系処理液を用いた電磁鋼板の絶縁皮膜形成について、従来の重クロム酸塩系処理液と同様の焼付け温度で成膜可能で、優れた耐水性と密着性を有する皮膜が形成でき、さらに付着量1.0g/m²以下の薄膜の絶縁皮膜の場合でも良好に成膜可能な処理液の開発を目指して鋭意検討を行った。
【００１５】
その結果、水溶性の多価リン酸塩の水溶液に、酸基、特にホスホン酸基を含有するキレート剤を添加した処理液により、上記目的が達成されることを見出し、本発明を完成させた。
【００１６】
本発明に係る電磁鋼板の絶縁皮膜形成用処理液は、水性溶媒中にＡｌ、Ｍｇ、Ｃａ、Ｓｒ、ＢａおよびＺｎのそれぞれの第一リン酸塩の１種または２種以上（Ａ）と、ホスホン酸化合物またはホスホン酸化合物およびカルボン酸化合物（Ｂ）とが溶解している処理液からなり、Ａｌ、Ｍｇ、Ｃａ、Ｓｒ、ＢａおよびＺｎのそれぞれの第一リン酸塩の１種または２種以上（Ａ）に含まれる金属原子のモル数とその価数の積の総和をΣＭｉとし、ホスホン酸化合物またはホスホン酸化合物およびカルボン酸化合物（Ｂ）のモル数と分子中の酸基数の積の総和をΣＯｉとするとき、（Ａ）と（Ｂ）の割合が下記の式（１）を満たし、さらに合成樹脂を含有することを特徴とする、電磁鋼板の絶縁皮膜形成用処理液。
【００１７】
0.1 ≦ΣＯｉ／ΣＭｉ≦５ ‥‥ (1)
好適態様にあっては、多価金属リン酸塩(A) は第一リン酸アルミニウムおよび／または第一リン酸マグネシウムであり、その処理液中の濃度は１〜50質量％の範囲内であり、キレート剤(B) は少なくとも一部がホスホン酸化合物である。
【００１８】
本発明の絶縁皮膜形成用処理液は、半有機皮膜を形成するように、さらに合成樹脂を含有していてもよい。合成樹脂は、リン酸塩水溶液に分散または溶解させて使用される。この場合、主に水性合成樹脂を用いるのが好ましい。水性合成樹脂とは、水溶性合成樹脂、水分散性合成樹脂、および水中エマルジョン型合成樹脂を包含する意味である。また、本発明の処理液は、合成樹脂とは別に、またはこれに加えて、さらにホウ酸および／またはコロイダルシリカを含有していてもよい。
【００１９】
本発明の処理液を用いた電磁鋼板の処理方法は、この処理液を電磁鋼板の少なくとも片面に塗布した後、加熱して塗膜を焼付け、電磁鋼板の表面に絶縁皮膜を形成することからなる。この処理方法は、特に形成された絶縁皮膜の付着量が片面当たり1.0 g/m²以下の薄い絶縁皮膜の形成に適用することが有利であり、その場合でも耐水性や密着性に優れ、湿潤試験で白化に耐える優れた絶縁皮膜を形成することができる。また、塗膜の焼付け温度 (最高到達板温度、以下同じ) は、従来の重クロム酸塩系処理液の場合と同様に 200〜330 ℃の範囲内とすることが好ましい。
【００２０】
【発明の実施の形態】
本発明により処理する電磁鋼板の種類は、特に限定されない。電磁鋼板は無方向性と方向性のいずれでもよく、また熱延鋼板と冷延鋼板のいずれでもよい。一般的な電磁鋼板は、Siを１〜５％程度含む低炭素鋼板であるが、Siをほとんど含まない普通鋼も電磁鋼板として使用可能である。
【００２１】
本発明で電磁鋼板に絶縁皮膜を形成するのに用いる処理液は、水性溶媒中に水溶性多価金属リン酸塩(A) と酸基を有するキレート剤(B) とが溶解した溶液である。水性溶媒は、水でよいが、水と水混和性有機溶媒 (例、アルコール、ケトン等) との混合溶媒も使用することができる。
【００２２】
多価金属リン酸塩(A) とキレート剤(B) の割合は、(A) に含まれる金属原子のモル数とその価数の積の総和をΣＭｉとし、(B) のモル数と分子中の酸基数の積の総和をΣＯｉとするとき、下記の式(1) を満たすような割合とする。
【００２３】
0.1 ≦ΣＯｉ／ΣＭｉ≦５ ‥‥ (1)
ΣＯｉ／ΣＭｉの値が0.1 より小さいと、薄膜の絶縁皮膜を形成する場合の成膜性が劣化し、均一な絶縁皮膜を形成することができず、耐水性も低下する。一方、ΣＯｉ／ΣＭｉの値が５より大きいと、処理液の粘度が上昇したり、処理液中の無機成分が経時的に沈降したりして、形成される絶縁皮膜の品質が安定しないばかりか、その耐水性が劣ることもある。ΣＯｉ／ΣＭｉの値の好ましい範囲は 0.2〜３である。
【００２４】
多価金属リン酸塩の水溶液にキレート剤を添加した処理液を使用することによ、成膜性や密着性、さらには付着量が1.0 g/m²以下の薄膜の絶縁皮膜の形成能が向上する理由は、明確には解明されていないが、下記のような機構が関与しているのではないかと本発明者らは推測している。
【００２５】
キレート剤を含有しない処理液 (即ち、多価金属リン酸塩の水溶液) を電磁鋼板の表面に塗布した場合、この処理液中に存在する、多価金属リン酸塩から解離した第一リン酸イオンや遊離リン酸が強酸性であるため、鋼板表面がエッチングされ、処理液中に鉄イオンが溶出する。溶出した鉄イオンと第一リン酸イオンまたは遊離リン酸が、乾燥に伴う処理液の濃縮によって化合し、乾燥初期からリン酸鉄の微細な粒子を形成する。これらのリン酸鉄微粒子は結晶質であるため、白濁した皮膜の外観を与えて成膜性を阻害したり、或いはリン酸鉄を基点として皮膜剥離を生じて密着性を阻害し、それにより耐水性をも低下させる。特に付着量1.0 g/m²以下の薄膜の場合には、皮膜中に生成するリン酸鉄粒子の径 (短径あるいは長径) の膜厚に対する占める割合が大きくなるため、皮膜の欠陥を生じやすくなり、成膜性や密着性・耐水性への悪影響がより大きくなる。
【００２６】
多価金属リン酸塩にキレート剤を添加した処理液を電磁鋼板の表面に塗布すると、鋼板表面のエッチングにより溶出した鉄イオンが、リン酸鉄の粒子を生成するより前に、キレート剤によって捕捉され、塗布された未乾燥の処理液中で安定化する。キレート剤は処理液中にほぼ均一に分散されていると考えられ、乾燥焼付けが進行するにつれ、キレート剤自身の一部脱水縮合を伴って、非晶質の皮膜として安定化するものと推測される。
【００２７】
水溶性多価金属リン酸塩化合物(A) は、絶縁皮膜を形成するベースとなる成分である。金属が１価のアルカリ金属であると、耐水性のある皮膜を形成することができないので、リン酸の多価金属を使用する。
【００２８】
水溶性の多価金属リン酸塩（Ａ）としては、第一リン酸アルミニウムおよび第一リン酸マグネシウムの一方または両方を使用することが好ましい。ここで、第一リン酸アルミニウムはＡｌ／Ｐのモル比が０．７／３〜１．２／３のものを包含し、第一リン酸マグネシウムはＭｇ／Ｐのモル比が０．７／２〜１．２／２のものを包含する。多価金属リン酸塩の金属イオンは、高濃度の処理液が得られやすい、工業的に安価といった理由から、上記の２種類（アルミニウム塩およびマグネシウム塩）が好ましいが、他の２価または３価の金属塩（Ｃａ、Ｓｒ、Ｂａ、Ｚｎ塩）も使用できる。また、市販のリン酸塩水溶液に金属または金属酸化物もしくは水酸化物を添加して、リン酸イオンに対して多価金属の比率を高めたものも使用できる。
【００２９】
処理液中の多価金属リン酸塩の濃度は１〜50質量％の範囲が好ましく、より好ましくは２〜30質量％である。この濃度が１質量％未満では、造膜性が乏しく、耐水性も低下する傾向が認められる。一方、この濃度が50％を超えると、処理液の安定性が低下し、固形物の沈降や粘度の上昇が生じ、均一な皮膜を形成することが困難となる。
【００３０】
キレート剤(B) は、多価金属リン酸塩の成膜性を改善し、低温焼付け条件においても耐水性が良好な皮膜が形成できるようにする。また、キレート剤(B) は、多価金属リン酸塩のみでは困難な、均一かつ非晶質で緻密な絶縁皮膜の形成を可能にする作用も果たす。
【００３１】
キレート剤(B) としては、酸基を有するキレート剤を使用する。これは、処理液が多価金属リン酸塩を含有し、酸性であるからである。例えば、エチレンジアミンといった酸基を有しないキレート剤では、処理液中の第一リン酸イオンと反応して、キレート形成能あるいは金属捕捉能力を失ってしまう。
【００３２】
酸基を有するキレート剤(B) としては、オキシカルボン酸、ジカルボン酸、アミノカルボン酸等のカルボン酸化合物も使用できるが、ホスホン酸 (亜リン酸) 化合物が、同じリン酸類であり、かつ皮膜の耐水性向上効果が大きいことから好ましい。また、ホスホン酸系キレート剤とカルボン酸系キレート剤とを併用することもできる。
【００３３】
ホスホン酸系キレート剤の具体例としては、ヒドロキシエチリデンモノ−およびジ−ホスホン酸、アミノトリメチレンホスホン酸等が挙げられる。カルボン酸系キレート剤のうち、オキシカルボン酸の具体例としてはグリコール酸、乳酸等が、ジカルボン酸の具体例としてはシュウ酸、マロン酸、コハク酸等が、アミノカルボン酸の具体例としてはエチレンジアミン四酢酸、ニトリロ三酢酸等がそれぞれ挙げられる。以上はいずれも例示にすぎず、他の化合物も使用することができる。
【００３４】
特開平11−131250号公報には、第一リン酸アルミニウムに有機酸金属塩を添加した処理液が開示され、有機酸としてコハク酸等のキレート剤となる化合物も例示されている。しかし、この有機酸は金属塩の形態で使用され、当然ながらキレート剤としては機能しない。例えば、コハク酸を本発明でキレート剤として使用する場合には、これは遊離形態でなければならない。
【００３５】
本発明の絶縁皮膜形成用処理液には、打抜き性のよい半有機皮膜が形成されるように、合成樹脂、好ましくは水性の合成樹脂を添加してもよい。水性合成樹脂は、前述したように、エマルジョン型、水分散性型、水溶性型のいずれの水性樹脂であってもよい。合成樹脂の具体例として、アクリル樹脂、アクリルスチレン樹脂、アルキッド樹脂、ポリエステル樹脂、シリコーン樹脂、フッ素樹脂、ポリオレフィン樹脂、スチレン樹脂、酢酸ビニル樹脂、エポキシ樹脂、フェノール樹脂、ウレタン樹脂、メラミン樹脂等が挙げられる。合成樹脂は、１種または２種以上添加することができる。
【００３６】
合成樹脂を処理液に添加する場合、その添加量は、多価金属リン酸塩100 質量部に対して３〜100 質量部の範囲内とすることが好ましい。合成樹脂の量が３質量部より少ないと、打抜き性の向上がほとんど得られず、100 質量部を超えると、歪取り焼鈍後の層間抵抗が低下することがある。この合成樹脂の添加量は、より好ましくは５〜5 質量部、さらに好ましくは７〜30質量部である。
【００３７】
本発明の処理液に、特に歪取り焼鈍後の耐食性を向上させるため、ホウ酸を添加してもよい。ホウ酸添加量は、多価金属リン酸塩のＰ換算100 質量部あたり、Ｂ換算で50質量部以下とすることが好ましい。添加量が過多であると層間抵抗や歪取り焼鈍後の耐食性が向上するものの、処理液中にホウ酸を完全に溶解することができず、液中で沈殿することがある。この添加量はより好ましくは２〜20質量部である。
【００３８】
本発明の処理液にはまた、層間抵抗を向上させるため、コロイダルシリカを配合してもよい。コロイダルシリカの添加量は、多価金属リン酸塩のＰ換算100 質量部あたり、Si換算で50質量部以下とすることが好ましい。シリカ添加量が過多であると、処理液の安定性が失われたり、表面性状が損なわれることがある。この添加量はより好ましくは２〜30質量部である。
【００３９】
上記以外にも、処理液中に、所望により、防錆剤、消泡剤、処理液安定化剤等の他の添加剤を適宜配合することができる。
本発明の処理液を使用し、これを素地の電磁鋼板の表面 (通常は両面であるが、片面に塗布することも可能) に塗布し、加熱して塗膜を焼付けると、耐水性と密着性に優れたリン酸塩系絶縁皮膜が形成される。
【００４０】
処理液の塗布方法は特に制限されず、工業的に一般に用いられる、ロールコーター、カーテンフローコーター、スプレー塗装、ナイフコーター、浸漬等の種々の塗布方法が適用できる。
【００４１】
皮膜の焼付けも、通常実施される、熱風式、赤外線式、誘導加熱式等の方法によって実施でき、従来の重クロム酸塩なみの焼付温度、即ち、 200〜330 ℃の温度範囲で１分以内の短時間の焼付きによる成膜で、耐水性と密着性に優れ、絶縁性も良好な皮膜になる。この絶縁皮膜の耐水性は、湿潤試験で白化に耐えるのに十分なものである。
【００４２】
電磁鋼板の絶縁皮膜の付着量は、0.1 g/m²以上、３g/m²以下が好ましい。付着量が0.1 g/m²未満であると、均一塗布が困難になるだけでなく、焼鈍時の耐焼付き性および耐食性、層間抵抗が不足する。付着量が３g/m²を超えると、層間抵抗の向上しろが飽和する上、皮膜の密着性が低下するようになる。層間抵抗、即ち、絶縁性が主に要求される場合には、付着量を1.0 g/m²以上とするのがよい。逆に、例えば、鉄芯や回転機の生産時の生産性の向上のために溶接性の改善が要求される場合には、1.0 g/m²未満、好ましくは0.5 g/m²以下の薄膜とすることが要求される。このように、用途で重視される性能に応じて、膜厚を設定することができる。本発明の処理液は、特に付着量が1.0 g/m²以下の薄膜を形成する場合にも成膜性が良好で、密着性や耐水性に優れた絶縁皮膜を形成できるという特長があるので、このような薄膜の絶縁皮膜の形成に適用することが有利である。
【００４３】
【実施例】
以下に示す実施例により本発明を具体的に例示するが、本発明はこれら実施例により制限されるものではない。実施例中の％および部は、特に指定しない限り質量％および質量部である。
【００４４】
(実施例１)
濃度30％の第一リン酸アルミニウム水溶液 (Al／Ｐ比＝ 0.9／３) に、キレート剤として１−ヒドロキシエチリデン−1,1 −ジホスホン酸 (ｋ１と表記) を、ΣＯｉ／ΣＭｉの値が種々の値をとるように添加して溶解させ、または無添加で、供試用の絶縁皮膜形成用処理液を作製した。比較用として、エチレングリコールまたはクエン酸アルミニウムをそれぞれリン酸アルミニウム100 部に対して５部の割合で添加した処理液を用意した。これらの処理液を40℃で６カ月間保存し、処理液の安定性を調べた。保存後の処理液に固形物が発生しない場合を○、固形物が発生した場合を×と評価した。
【００４５】
これらの各処理液を、0.1 ％のSiを含む板厚0.5 mmの電磁鋼板の両面に、焼付け後の絶縁皮膜の付着量が 0.1〜２g/m²となるようにロールコーターで塗布した後、熱風炉で最高到達板温度が270 ℃となるように30秒間加熱して塗膜を焼付け、絶縁皮膜を形成した。得られた絶縁皮膜付き電磁鋼板の耐水性と密着性を次に述べるように評価した。結果を、処理液組成と一緒に表１に示す。
【００４６】
耐水性
50℃、98％RHの湿潤試験機内に、絶縁皮膜付き電磁鋼板の試験片を吊るし、72時間後の皮膜表面の状態を、触手によるべたつきの有無と、色差測定による白化の程度により調査した。評価は下記の４段階にて行い○、◎を合格とした。皮膜の白化については、ミノルタ製全反射型色差測定器CR-300を使用し、JIS-Z8730 で規定されるＬ値 (白さを表す数値) を試験前後に測定し、そのＬ値の変化 (ΔＬ) の大きさで白化を判断した。
【００４７】
◎：べたつきなし、白化なし (ΔＬ≦２) 、
○：べたつきなし、白化やや有り (ΔＬ≦５) 、
△：べたつき有り、白化有り (ΔＬ≦10) 、
×：べたつき有り、白化顕著 (ΔＬ≦20) 。
【００４８】
絶縁皮膜の密着性
長さ50 mm 、幅25 mm の絶縁皮膜付き電磁鋼板の試験片を、直径５mmの鉄棒に巻き付け、巻き付けた外側の部分についてテープ剥離試験を行って、鋼板に残存した絶縁皮膜の状況を調査した。下記の４段階で評価を行い、◎、○を合格とした。
【００４９】
◎：皮膜剥離なし、
○：皮膜剥離発生 (面積率で５％以下) 、
△：皮膜剥離発生 (面積率で５％超、30％以下) 、
×：皮膜剥離発生 (面積率で30％超) 。
【００５０】
【表１】

表１からわかるように、キレート剤を添加せず、第一リン酸アルミニウムのみの絶縁皮膜では、耐水性が劣り、その傾向は付着量が小さくなるほど強まり、密着性まで悪くなる。それに対し、本発明に従ってキレート剤を配合した処理液を使用すると、耐水性や密着性が著しく改善され、 0.1〜0.2 g/m²という非常な薄膜の絶縁皮膜でも、耐水性と密着性が十分に良好となる。ただし、キレート剤の添加量が少なすぎると、この改善が得られず、キレート剤の添加量が多すぎると、処理液の安定性が損なわれる。
【００５１】
作製した絶縁皮膜付き電磁鋼板について、750 ℃で２時間の歪取焼鈍を施した後の皮膜性能を密着性および層間抵抗に関して調査した。表１の試験No. の試料のうち、１〜３および５〜８の試料は、焼鈍後に長さ50 mm 、直径20 mm の丸棒に巻付け、巻き付けた皮膜の外側をテープ剥離すると、皮膜剥離が見られた。６〜16の試料は密着性良好であった。一方、４の試料は皮膜ムラがあり、歪取焼鈍後の層間抵抗が0.5 Ωcm²/枚以下であった。他の試料は３〜100 Ωcm²/枚の層間抵抗を示し、焼鈍後としては十分な絶縁性を示した。
【００５２】
(実施例２)
濃度30％の第一リン酸アルミニウム (Al／Ｐ比＝ 0.9／３) または濃度30％の第一リン酸マグネシウム (Mg／Ｐ比＝0.85／２) の水溶液に、キレート剤として１−ヒドロキシエチリデン−1,1 −ジホスホン酸 (ｋ１) 、アミノトリメチレンホスホン酸 (ｋ２) および／またはグリコール酸を (ｋ３) を、ΣＯｉ／ΣＭｉの値が１になる割合で添加して溶解させた。この多価金属リン酸塩／キレート剤水溶液に、ガラス転移点20℃のアクリルエマルジョンを多価金属リン酸塩100 部に対して20部の量で添加し、場合によりさらに、多価金属リン酸塩のＰ換算100 部に対して、ホウ酸をＢ換算で20部またはコロイダルシリカをSi換算で10部添加し、十分に攪拌して、処理液を作製した。
【００５３】
この処理液を用いて、焼付け温度 (最高到達板温度) を変更した以外は実施例１と同様にして、電磁鋼板の両面に絶縁皮膜を形成し、耐水性と密着性を評価した。試験結果を、処理液組成および焼付け温度 (加熱時間は30秒) 一緒に表２にまとめて示す。
【００５４】
【表２】

表２からわかるように、合成樹脂を添加した打抜き性のよい半有機型の絶縁皮膜の場合でも薄膜の絶縁皮膜で耐水性と密着性に優れた絶縁皮膜を形成することができた。また、多価金属リン酸塩やキレート剤の種類を変更したり、焼付け温度を変化させたり、あるいはホウ酸もしくはコロイダルシリカといった添加剤を添加しても、耐水性および密着性への著しい影響は見られず、いずれも良好な結果であった。
【００５５】
【発明の効果】
本発明の電磁鋼板の絶縁皮膜形成用処理液は、クロム等の有害物を含んでおらず、成膜性に優れているので、電磁鋼板の従来の重クロム酸塩と同レベルの焼付け温度で、かつ付着量が1.0 g/m²以下、特に0.5 g/m²以下といった薄膜でも、耐水性と密着性に優れた絶縁皮膜を形成することができる。この絶縁皮膜は、付着量が0.1 g/m²以上であれば、実用上十分な層間抵抗 (JIS-C2550 に準拠した測定で５〜10Ω・cm²/枚以上) を有する。
【００５６】
従って、本発明により、環境や人員への悪影響を懸念せずに、耐水性、絶縁性、密着性等の必要な諸性能を備えた絶縁皮膜を、用途に応じて厚膜から薄膜までの付着量で、比較的安価に電磁鋼板の表面に形成することができる。この絶縁皮膜は、従来の多価金属リン酸塩系皮膜には見られない、優れた薄膜性能 (薄膜での成膜性、密着性、耐水性) を有する。本発明の処理液を用いて製造した絶縁皮膜付き電磁鋼板は、モーター用途をはじめ、広範囲の用途に利用可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment liquid and a treatment method for forming an insulating film on the surface of an electrical steel sheet, and in particular, it does not contain harmful compounds such as hexavalent chromium and has been generally used as an insulating film for non-oriented electrical steel sheets. It can be manufactured at the same baking temperature as that of dichromate-based coatings, and has excellent water resistance that cannot be obtained with conventional phosphate-based insulating coatings, especially for thin films of 1.0 g / m ² or less. The present invention relates to a treatment liquid and a treatment method for forming an insulating film of an electrical steel sheet, which are excellent in film formability, adhesion and water resistance when forming an insulating film.
[0002]
[Prior art]
Insulation coatings on electrical steel sheets used for iron cores of rotating machines and transformers require not only interlayer resistance but also various characteristics such as user convenience (punchability, weldability, heat resistance, caulking properties). Is done.
[0003]
Insulating films for non-oriented electrical steel sheets that are generally used at present are roughly classified into the following three types:
(1) An inorganic film that emphasizes heat resistance and is capable of strain relief annealing.
(2) An inorganic-organic mixed organic semi-organic film capable of strain relief annealing, aiming to achieve both punchability and weldability.
(3) An organic film that emphasizes punchability and cannot be subjected to strain relief annealing.
[0004]
Among them, the insulating film containing the inorganic components (1) and (2) that can be subjected to strain relief annealing is widely used. In particular, the semi-organic film (2) has become mainstream because it has much better punchability than inorganic films.
[0005]
Hitherto, dichromate has been widely used as a material for forming inorganic components in the insulating films of the above (1) and (2). An insulating film using dichromate is heated after applying a treatment liquid obtained by mixing an organic reducing agent such as ethylene glycol or glycerin to an aqueous solution containing hexavalent chromium and a polyvalent metal salt on an electrical steel sheet. The coating film is baked, and hexavalent chromium is reduced to trivalent chromium to form a film. Baking is completed in a short time of less than 1 minute at a temperature of 200 ° C to 330 ° C. However, hexavalent chromium used for the formation of this insulating film is highly toxic, and there is a concern about the danger of harming the health of human beings involved in production. Further, trivalent chromium contained in the formed insulating film is much less toxic than hexavalent chromium, but cannot be said to be completely harmless. Therefore, an insulating film using dichromate cannot be denied that it may be slightly harmful to humans or the environment at the manufacturing and product stages, and a non-chromium type insulating film that does not use chromium at all is required. It has become.
[0006]
As an inorganic component that can be used for forming an insulating film as in the case of dichromate, there is a phosphate. Phosphate aqueous solution is one of the few inorganic components capable of forming a film and can be obtained at a relatively low cost. Therefore, it has been conventionally studied as an inorganic component for inorganic and semi-organic insulating films (for example, JP-B-53). -28375).
[0007]
However, unlike a dichromate-based reduction reaction, a phosphate-based insulating film is formed into a film by increasing the water insolubility of the film by polymerizing the phosphate by the progress of condensation due to the dehydration reaction. Therefore, in order to form a highly water-resistant insulating film, it is necessary to bake at a higher temperature (eg, 300 to 400 ° C.) than the dichromate-based treatment liquid after application of the treatment liquid. When the baking temperature increases, there are problems as described below.
[0008]
(1) The amount of heat and / or time required for baking increases, which is disadvantageous from the viewpoint of industrial productivity and economy.
(2) A part of the resin contained in the general-purpose semi-organic film may be thermally decomposed to deteriorate the film performance (adhesion, corrosion resistance, punchability). If a resin having high heat resistance is used, this problem is alleviated, but such a resin is expensive and difficult to employ industrially from the viewpoint of economy.
[0009]
Examples of phosphate-based insulating films include primary aluminum phosphate and organic emulsion resin, which can be used to increase the particle size of the emulsion or other components (crosslinked resin powder, alcohol, or organic acid metal). It is proposed in Japanese Patent Application Laid-Open Nos. 5-78855, 6-330338, 11-131250, and 11-152579 to form an insulating film using a treatment solution to which a salt is further added. .
[0010]
However, as a result of the study by the present inventors, the treatment liquids described in each of these publications have a particularly small film thickness (adhesion amount of about 1.0 g / m ² or less) when forming a thin insulating film, It has been found that if the film formability is insufficient and the baking temperature is not increased, the water resistance and adhesion of the insulating film are lowered and the performance of the thin film is poor. A magnetic steel sheet provided with a thin insulating film is required particularly for applications in which weldability is important and applications in which automatic caulking is important.
[0011]
For example, Japanese Patent Application Laid-Open Nos. 11-131250 and 11-152579 show the corrosion resistance test results in a wet test of a film baked at 200 ° C. or 250 ° C., and the corrosion resistance is evaluated by the presence or absence of rust. However, even when rust is not recognized by such an evaluation method, it cannot be said that the water resistance is sufficient. This is because even if rust does not occur, performance deterioration such as stickiness and slipperiness is recognized only by whitening of the insulating film.
[0012]
[Problems to be solved by the invention]
There have been several examples of phosphate coatings used as semi-organic coatings for non-oriented electrical steel sheets, but a higher baking temperature is required compared to dichromate coatings, especially for thin films. Therefore, it was used only for very limited purposes.
[0013]
Films can be formed at a low baking temperature similar to that of dichromate without using chromium, and even in such cases, it can be used as an insulation film for electrical steel sheets with excellent water resistance, adhesion, insulation, etc. There have been no treatment liquids for forming an insulating film on a magnetic steel sheet that has various performances and exhibits excellent film formability even in a thin film. The present invention provides such a treatment liquid and a method for forming an insulating film on an electrical steel sheet using the same.
[0014]
[Means for Solving the Problems]
The inventors of the present invention can form a film at the same baking temperature as that of a conventional dichromate treatment liquid, and have excellent water resistance and adhesion, for forming an insulating film of an electrical steel sheet using a phosphate treatment liquid. In order to develop a treatment solution that can form a film with good adhesion even in the case of a thin insulating film having an adhesion amount of 1.0 g / m ² or less, we have made extensive studies.
[0015]
As a result, the inventors have found that the above object can be achieved by a treatment solution in which a chelating agent containing an acid group, particularly a phosphonic acid group, is added to an aqueous solution of a water-soluble polyvalent phosphate, and the present invention has been completed. .
[0016]
Insulation film forming treatment solution of the electromagnetic steel sheet according to the present invention, an aqueous solvent Al, Mg, Ca, Sr, 1 or two or more of each of the first phosphate Ba and Zn and (A), A treatment liquid in which a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) are dissolved , and one or two primary phosphates of Al, Mg, Ca, Sr, Ba and Zn or the number of moles of metal atoms contained in (a) and the sum of the products of the valences and ShigumaMi, phosphonate compound or phosphoric acid compound and a carboxylic acid compound moles of the product of the acid groups in the molecule of (B) when the ΣOi the sum, (a) the ratio of (B) is less than the equation (1) below, further characterized by containing a synthetic resin, the insulating film forming treatment solution of the electromagnetic steel sheets.
[0017]
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)
In a preferred embodiment, the polyvalent metal phosphate (A) is primary aluminum phosphate and / or primary magnesium phosphate, and its concentration in the treatment liquid is in the range of 1 to 50% by mass. The chelating agent (B) is at least partially a phosphonic acid compound.
[0018]
The treatment liquid for forming an insulating film of the present invention may further contain a synthetic resin so as to form a semi-organic film. The synthetic resin is used after being dispersed or dissolved in an aqueous phosphate solution. In this case, it is preferable to mainly use an aqueous synthetic resin. The aqueous synthetic resin is meant to include water-soluble synthetic resins, water-dispersible synthetic resins, and emulsion-in-water synthetic resins. Moreover, the treatment liquid of the present invention may further contain boric acid and / or colloidal silica separately from or in addition to the synthetic resin.
[0019]
The method for treating an electrical steel sheet using the treatment liquid of the present invention comprises applying the treatment liquid to at least one surface of the electrical steel sheet, then heating and baking the coating film to form an insulating film on the surface of the electrical steel sheet. . This treatment method is particularly advantageous when applied to the formation of a thin insulating film with an adhesion amount of the formed insulating film of 1.0 g / m ² or less per side, and even in such a case, it has excellent water resistance and adhesion, and is wet. An excellent insulating film that resists whitening can be formed in the test. The baking temperature of the coating film (maximum reached plate temperature, hereinafter the same) is preferably in the range of 200 to 330 ° C. as in the case of the conventional dichromate-based treatment liquid.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The kind of electrical steel sheet processed by this invention is not specifically limited. The electromagnetic steel sheet may be non-directional or directional, and may be either a hot-rolled steel sheet or a cold-rolled steel sheet. A general electromagnetic steel sheet is a low-carbon steel sheet containing about 1 to 5% of Si, but ordinary steel containing almost no Si can also be used as the electromagnetic steel sheet.
[0021]
The treatment liquid used for forming an insulating film on the electrical steel sheet in the present invention is a solution in which a water-soluble polyvalent metal phosphate (A) and a chelating agent (B) having an acid group are dissolved in an aqueous solvent. . The aqueous solvent may be water, but a mixed solvent of water and a water-miscible organic solvent (eg, alcohol, ketone, etc.) can also be used.
[0022]
The ratio of polyvalent metal phosphate (A) to chelating agent (B) is the sum of the product of the number of moles of metal atoms contained in (A) and its valence, ΣMi, and the number of moles of (B) and the molecule When the sum of products of the number of acid groups therein is ΣOi, the ratio is set so as to satisfy the following formula (1).
[0023]
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)
When the value of ΣOi / ΣMi is less than 0.1, the film formability when forming a thin insulating film is deteriorated, a uniform insulating film cannot be formed, and the water resistance is also lowered. On the other hand, if the value of ΣOi / ΣMi is greater than 5, not only will the viscosity of the treatment liquid increase or the inorganic components in the treatment liquid will settle down over time, and the quality of the insulating film formed will not be stable. The water resistance may be inferior. A preferable range of the value of ΣOi / ΣMi is 0.2-3.
[0024]
By using a treatment solution in which a chelating agent is added to an aqueous solution of polyvalent metal phosphate, the film formability and adhesion, as well as the ability to form a thin insulating film with a coating weight of 1.0 g / m ² or less The reason for the improvement is not clearly clarified, but the present inventors speculate that the following mechanism may be involved.
[0025]
When a treatment liquid containing no chelating agent (that is, an aqueous solution of polyvalent metal phosphate) is applied to the surface of the electrical steel sheet, the primary phosphoric acid dissociated from the polyvalent metal phosphate present in the treatment liquid Since ions and free phosphoric acid are strongly acidic, the steel plate surface is etched, and iron ions are eluted in the treatment liquid. The eluted iron ions and primary phosphate ions or free phosphate are combined by concentration of the treatment liquid accompanying drying, and fine particles of iron phosphate are formed from the beginning of drying. Since these iron phosphate fine particles are crystalline, they give the appearance of a cloudy film and inhibit film formation, or peel off the film from iron phosphate and inhibit adhesion, thereby preventing water resistance. It also reduces sex. In particular, in the case of a thin film with an adhesion amount of 1.0 g / m ² or less, the ratio of the diameter (short diameter or long diameter) of the iron phosphate particles formed in the film to the film thickness is large, and thus film defects are likely to occur. As a result, adverse effects on film formability, adhesion, and water resistance are further increased.
[0026]
When a treatment liquid in which a chelating agent is added to a polyvalent metal phosphate is applied to the surface of a magnetic steel sheet, the iron ions eluted by etching the steel sheet surface are captured by the chelating agent before producing iron phosphate particles. And stabilized in the applied undried processing solution. It is considered that the chelating agent is almost uniformly dispersed in the processing solution, and it is estimated that as the baking finishes, the chelating agent itself partially stabilizes as an amorphous film with some dehydration condensation. The
[0027]
The water-soluble polyvalent metal phosphate compound (A) is a component that serves as a base for forming an insulating film. If the metal is a monovalent alkali metal, a water-resistant film cannot be formed. Therefore, a polyvalent metal of phosphoric acid is used.
[0028]
As the water-soluble polyvalent metal phosphate (A), it is preferable to use one or both of primary aluminum phosphate and primary magnesium phosphate. Here, primary aluminum phosphate includes Al / P having a molar ratio of 0.7 / 3 to 1.2 / 3, and primary magnesium phosphate has a molar ratio of Mg / P of 0.7 / 2 to 1.2 / 2 are included. The metal ions of the polyvalent metal phosphate are preferably the above two types (aluminum salt and magnesium salt) because a high-concentration treatment solution is easily obtained and industrially inexpensive. Valent metal salts (Ca, Sr, Ba, Zn salts) can also be used. Moreover, what added the metal or metal oxide, or hydroxide to the commercially available phosphate aqueous solution, and raised the ratio of the polyvalent metal with respect to phosphate ion can also be used.
[0029]
The concentration of the polyvalent metal phosphate in the treatment liquid is preferably in the range of 1 to 50% by mass, more preferably 2 to 30% by mass. When this concentration is less than 1% by mass, the film-forming property is poor and the water resistance tends to decrease. On the other hand, when the concentration exceeds 50%, the stability of the treatment liquid is lowered, the solids are settled and the viscosity is increased, and it becomes difficult to form a uniform film.
[0030]
The chelating agent (B) improves the film formability of the polyvalent metal phosphate so that a film having good water resistance can be formed even under low temperature baking conditions. In addition, the chelating agent (B) also serves to make it possible to form a uniform, amorphous and dense insulating film, which is difficult with only the polyvalent metal phosphate.
[0031]
As the chelating agent (B), a chelating agent having an acid group is used. This is because the treatment liquid contains a polyvalent metal phosphate and is acidic. For example, a chelating agent having no acid group, such as ethylenediamine, reacts with the primary phosphate ion in the treatment liquid, and loses the chelate forming ability or the metal capturing ability.
[0032]
As the chelating agent (B) having an acid group, carboxylic acid compounds such as oxycarboxylic acid, dicarboxylic acid, and aminocarboxylic acid can also be used. However, the phosphonic acid (phosphorous acid) compound is the same phosphoric acid, and the film. This is preferable because of its large water resistance improvement effect. Also, a phosphonic acid chelating agent and a carboxylic acid chelating agent can be used in combination.
[0033]
Specific examples of the phosphonic acid chelating agent include hydroxyethylidene mono- and di-phosphonic acid, aminotrimethylene phosphonic acid and the like. Among carboxylic acid-based chelating agents, specific examples of oxycarboxylic acids include glycolic acid and lactic acid, specific examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, and the like, and specific examples of aminocarboxylic acids include ethylenediamine. Examples include tetraacetic acid and nitrilotriacetic acid. The above is only an example, and other compounds can be used.
[0034]
Japanese Patent Application Laid-Open No. 11-131250 discloses a treatment liquid in which an organic acid metal salt is added to primary aluminum phosphate, and examples of compounds that can be used as chelating agents such as succinic acid as organic acids. However, this organic acid is used in the form of a metal salt and naturally does not function as a chelating agent. For example, if succinic acid is used as a chelating agent in the present invention, it must be in free form.
[0035]
A synthetic resin, preferably an aqueous synthetic resin, may be added to the treatment liquid for forming an insulating film of the present invention so that a semi-organic film having good punchability is formed. As described above, the aqueous synthetic resin may be any emulsion type, water-dispersible type, or water-soluble type. Specific examples of synthetic resins include acrylic resins, acrylic styrene resins, alkyd resins, polyester resins, silicone resins, fluororesins, polyolefin resins, styrene resins, vinyl acetate resins, epoxy resins, phenol resins, urethane resins, melamine resins, etc. It is done. One or more synthetic resins can be added.
[0036]
When adding a synthetic resin to a process liquid, it is preferable to make the addition amount into the range of 3-100 mass parts with respect to 100 mass parts of polyvalent metal phosphates. When the amount of the synthetic resin is less than 3 parts by mass, improvement in punchability is hardly obtained, and when it exceeds 100 parts by mass, the interlayer resistance after strain relief annealing may be lowered. The amount of the synthetic resin added is more preferably 5 to 5 parts by mass, still more preferably 7 to 30 parts by mass.
[0037]
Boric acid may be added to the treatment liquid of the present invention in order to improve the corrosion resistance especially after the strain relief annealing. The amount of boric acid added is preferably 50 parts by mass or less in terms of B per 100 parts by mass in terms of P of the polyvalent metal phosphate. If the amount added is excessive, the interlayer resistance and the corrosion resistance after strain relief annealing are improved, but boric acid cannot be completely dissolved in the treatment liquid and may precipitate in the liquid. This addition amount is more preferably 2 to 20 parts by mass.
[0038]
The treatment liquid of the present invention may also contain colloidal silica in order to improve interlayer resistance. The amount of colloidal silica added is preferably 50 parts by mass or less in terms of Si per 100 parts by mass in terms of P of the polyvalent metal phosphate. If the amount of silica added is excessive, the stability of the treatment liquid may be lost or the surface properties may be impaired. This addition amount is more preferably 2 to 30 parts by mass.
[0039]
In addition to the above, other additives such as a rust inhibitor, an antifoaming agent, and a treatment liquid stabilizer can be appropriately blended in the treatment liquid as desired.
Using the treatment liquid of the present invention, applying this to the surface of the base electrical steel sheet (usually both sides, but it is also possible to apply to one side) and baking the film by heating, the water resistance and A phosphate insulating film excellent in adhesion is formed.
[0040]
The coating method of the treatment liquid is not particularly limited, and various coating methods such as roll coater, curtain flow coater, spray coating, knife coater, and immersion, which are generally used industrially, can be applied.
[0041]
Baking of the film can also be performed by the usual methods such as hot air, infrared, induction heating, etc., and the baking temperature similar to that of the conventional dichromate, that is, within a temperature range of 200 to 330 ° C. within 1 minute. The film is formed by baking for a short period of time, resulting in a film with excellent water resistance and adhesion and good insulation. The water resistance of this insulating film is sufficient to withstand whitening in a wet test.
[0042]
The adhesion amount of the insulating coating on the electrical steel sheet is preferably 0.1 g / m ² or more and 3 g / m ² or less. When the adhesion amount is less than 0.1 g / m ² , not only uniform coating becomes difficult, but also seizure resistance, corrosion resistance and interlayer resistance during annealing are insufficient. When the adhesion amount exceeds 3 g / m ² , the improvement in interlayer resistance is saturated and the adhesion of the film is lowered. When interlayer resistance, that is, insulation is mainly required, the adhesion amount should be 1.0 g / m ² or more. Conversely, for example, when improvement in weldability is required to improve productivity during production of iron cores and rotating machines, a thin film of less than 1.0 g / m ² , preferably 0.5 g / m ² or less Is required. Thus, the film thickness can be set according to the performance that is important in the application. The treatment liquid of the present invention has the advantage that it can form an insulating film excellent in adhesion and water resistance, particularly when a thin film having an adhesion amount of 1.0 g / m ² or less is formed. It is advantageous to apply to the formation of such a thin insulating film.
[0043]
【Example】
The present invention is specifically illustrated by the following examples, but the present invention is not limited by these examples. Unless otherwise specified, “%” and “parts” in the examples are “% by mass” and “parts by mass”.
[0044]
(Example 1)
1-Hydroxyethylidene-1,1-diphosphonic acid (denoted as k1) as a chelating agent in 30% aqueous solution of primary aluminum phosphate (Al / P ratio = 0.9 / 3) with various values of ΣOi / ΣMi A treatment solution for forming an insulating film for test was prepared by adding and dissolving so as to take the value of 1 or without addition. For comparison, a treatment liquid was prepared in which ethylene glycol or aluminum citrate was added at a ratio of 5 parts to 100 parts of aluminum phosphate. These treatment solutions were stored at 40 ° C. for 6 months, and the stability of the treatment solutions was examined. The case where a solid substance did not generate | occur | produce in the process liquid after a preservation | save was evaluated as (circle) and the case where a solid substance generate | occur | produced was evaluated as x.
[0045]
Each of these treatment liquids was applied on both sides of a 0.5 mm thick steel sheet containing 0.1% Si by a roll coater so that the amount of the insulating film deposited after baking was 0.1-2 g / m ² . The coating film was baked by heating for 30 seconds so that the maximum plate temperature reached 270 ° C. in a hot air oven to form an insulating film. The water resistance and adhesion of the obtained electrical steel sheet with an insulating film were evaluated as described below. The results are shown in Table 1 together with the treatment liquid composition.
[0046]
water resistant
A test piece of a magnetic steel sheet with an insulating film was hung in a wet testing machine at 50 ° C. and 98% RH, and the state of the film surface after 72 hours was investigated by the presence or absence of stickiness by a tentacle and the degree of whitening by color difference measurement. Evaluation was performed in the following four stages, and ○ and ◎ were regarded as acceptable. For whitening of the film, Minolta's total reflection color difference meter CR-300 was used, and the L value (numerical value representing whiteness) specified by JIS-Z8730 was measured before and after the test, and the change in the L value ( Whitening was judged by the magnitude of ΔL).
[0047]
A: No stickiness, no whitening (ΔL ≦ 2),
○: No stickiness, slight whitening (ΔL ≦ 5),
Δ: Stickiness, whitening (ΔL ≦ 10),
X: Stickiness, remarkable whitening (ΔL ≦ 20).
[0048]
Adhesion of insulating film A test piece of 50 mm long and 25 mm wide magnetic steel sheet with an insulating film was wound around a 5 mm diameter iron bar, and the outer part of the wound wire was subjected to a tape peeling test to form a steel sheet. The state of the remaining insulation film was investigated. Evaluation was made in the following four stages, and ◎ and ○ were accepted.
[0049]
A: No film peeling,
○: Film peeling occurred (area ratio is 5% or less),
Δ: Film peeling occurred (area ratio is over 5%, 30% or less),
X: Film peeling occurred (area ratio exceeds 30%).
[0050]
[Table 1]

As can be seen from Table 1, in the insulating film containing only the primary aluminum phosphate without adding a chelating agent, the water resistance is inferior, the tendency becomes stronger as the adhesion amount becomes smaller, and the adhesiveness becomes worse. On the other hand, when a treatment liquid containing a chelating agent according to the present invention is used, the water resistance and adhesion are remarkably improved, and even with a very thin insulating film of 0.1 to 0.2 g / m ² , the water resistance and adhesion are sufficient. It will be good. However, if the addition amount of the chelating agent is too small, this improvement cannot be obtained, and if the addition amount of the chelating agent is too large, the stability of the treatment liquid is impaired.
[0051]
About the produced magnetic steel sheet with an insulating film, the film performance after carrying out the stress relief annealing for 2 hours at 750 degreeC was investigated regarding adhesiveness and interlayer resistance. Of the samples of test No. 1 in Table 1, samples 1 to 3 and 5 to 8 were wound on a round bar having a length of 50 mm and a diameter of 20 mm after annealing, and the outside of the wound film was peeled off with tape. Peeling was observed. Samples 6 to 16 had good adhesion. On the other hand, the sample No. 4 had uneven coating, and the interlayer resistance after strain relief annealing was 0.5 Ωcm ² / sheet or less. The other samples showed an interlayer resistance of 3 to 100 Ωcm ² / sheet, and showed sufficient insulation after annealing.
[0052]
(Example 2)
1-hydroxyethylidene as a chelating agent in an aqueous solution of 30% primary aluminum phosphate (Al / P ratio = 0.9 / 3) or 30% primary magnesium phosphate (Mg / P ratio = 0.85 / 2) -1,1-diphosphonic acid (k1), aminotrimethylenephosphonic acid (k2) and / or glycolic acid (k3) were added and dissolved at a ratio of ΣOi / ΣMi of 1. To this polyvalent metal phosphate / chelating agent aqueous solution, an acrylic emulsion having a glass transition point of 20 ° C. is added in an amount of 20 parts with respect to 100 parts of the polyvalent metal phosphate. 20 parts of boric acid in terms of B or 10 parts of colloidal silica in terms of Si was added to 100 parts in terms of P of the salt, and stirred sufficiently to prepare a treatment solution.
[0053]
Using this treatment liquid, an insulating film was formed on both surfaces of the magnetic steel sheet in the same manner as in Example 1 except that the baking temperature (maximum reached plate temperature) was changed, and water resistance and adhesion were evaluated. The test results are summarized in Table 2 together with the treatment liquid composition and baking temperature (heating time is 30 seconds).
[0054]
[Table 2]

As can be seen from Table 2, even in the case of a semi-organic insulating film having a good punching property to which a synthetic resin was added, an insulating film excellent in water resistance and adhesion could be formed with a thin insulating film. Also, even if the type of polyvalent metal phosphate or chelating agent is changed, the baking temperature is changed, or additives such as boric acid or colloidal silica are added, there is a significant effect on water resistance and adhesion. It was not seen and all were good results.
[0055]
【The invention's effect】
The treatment liquid for forming an insulating film of the electrical steel sheet according to the present invention does not contain harmful substances such as chromium and is excellent in film formability. Therefore, at the same baking temperature as the conventional dichromate of the electrical steel sheet. Even with a thin film having an adhesion amount of 1.0 g / m ² or less, particularly 0.5 g / m ² or less, an insulating film excellent in water resistance and adhesion can be formed. This insulating film has a practically sufficient interlayer resistance (5 to 10 Ω · cm ² / sheet or more as measured in accordance with JIS-C2550) when the adhesion amount is 0.1 g / m ² or more.
[0056]
Therefore, according to the present invention, an insulating film having necessary performances such as water resistance, insulation and adhesion can be attached from a thick film to a thin film depending on the application without concern for adverse effects on the environment and personnel. The amount can be formed on the surface of the electromagnetic steel sheet relatively inexpensively. This insulating film has excellent thin film performance (film forming property, adhesion, water resistance) that is not found in conventional polyvalent metal phosphate-based films. The electrical steel sheet with an insulating film manufactured using the treatment liquid of the present invention can be used for a wide range of applications including motor applications.

Claims

One or more of each primary phosphate of Al, Mg, Ca, Sr, Ba and Zn (A) in an aqueous solvent, and a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) The number of moles of metal atoms contained in one or more of the primary phosphates of Al, Mg, Ca, Sr, Ba and Zn (A) and their valencies When the sum of the products of the numbers is ΣMi and the sum of the products of the number of moles of the phosphonic acid compound or the phosphonic acid compound and the carboxylic acid compound (B) and the number of acid groups in the molecule is ΣOi, (A) and (B) ratio meets the following equation (1), further characterized by containing a synthetic resin, the insulating film forming treatment solution of the electromagnetic steel sheets.
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)

One or more of each primary phosphate of Al, Mg, Ca, Sr, Ba and Zn (A) in an aqueous solvent, and a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) The number of moles of metal atoms contained in one or more primary phosphates of Al, Mg, Ca, Sr, Ba, and Zn (A) and their valencies When the sum of the products of the numbers is ΣMi and the sum of the products of the number of moles of the phosphonic acid compound or the phosphonic acid compound and the carboxylic acid compound (B) and the number of acid groups in the molecule is ΣOi, (A) and (B) A treatment liquid for forming an insulating film on an electrical steel sheet, characterized in that the ratio satisfies the following formula (1) and further contains boric acid and / or colloidal silica.
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)

One or more of each primary phosphate of Al, Mg, Ca, Sr, Ba and Zn (A) in an aqueous solvent, and a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) The number of moles of metal atoms contained in one or more primary phosphates of Al, Mg, Ca, Sr, Ba, and Zn (A) and their valencies When the sum of the products of the numbers is ΣMi and the sum of the products of the number of moles of the phosphonic acid compound or the phosphonic acid compound and the carboxylic acid compound (B) and the number of acid groups in the molecule is ΣOi, (A) and (B) Ratio is the following formula (1) And further containing a synthetic resin and boric acid and / or colloidal silica.
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)

The processing liquid according to any one of claims 1 to 3, wherein the concentration of (A) is in the range of 1 to 50 mass%.

One or more of each primary phosphate of Al, Mg, Ca, Sr, Ba and Zn (A) in an aqueous solvent, and a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) The number of moles of metal atoms contained in one or more primary phosphates of Al, Mg, Ca, Sr, Ba, and Zn (A) and their valencies When the sum of the products of the numbers is ΣMi and the sum of the products of the number of moles of the phosphonic acid compound or the phosphonic acid compound and the carboxylic acid compound (B) and the number of acid groups in the molecule is ΣOi, (A) and (B) A treatment liquid for forming an insulating film of a magnetic steel sheet, wherein the ratio satisfies the following formula (1) (provided that one or more of Mo, Ti, V, and Zr oxysulfates, a P compound, and a Zn compound) And phosphonate Except when).
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)

One or more of each primary phosphate of Al, Mg, Ca, Sr, Ba and Zn (A) in an aqueous solvent, and a phosphonic acid compound or a phosphonic acid compound and a carboxylic acid compound (B) The number of moles of metal atoms contained in one or more primary phosphates of Al, Mg, Ca, Sr, Ba, and Zn (A) and their valencies When the sum of the products of the numbers is ΣMi and the sum of the products of the number of moles of the phosphonic acid compound or the phosphonic acid compound and the carboxylic acid compound (B) and the number of acid groups in the molecule is ΣOi, (A) and (B) Ratio is the following formula (1) A method for treating an electrical steel sheet, comprising: applying a treatment liquid for forming an insulating film of an electrical steel sheet satisfying at least one surface of the electrical steel sheet, then heating and baking the coating film to form an insulating film on the surface of the electrical steel sheet.
0.1 ≦ ΣOi / ΣMi ≦ 5 (1)

The method according to claim 6 , wherein the concentration of (A) is in the range of 1 to 50 mass%.

A treatment of an electromagnetic steel sheet comprising applying the treatment liquid according to any one of claims 1 to 4 to at least one surface of an electromagnetic steel sheet, then heating and baking the coating film to form an insulating film on the surface of the electromagnetic steel sheet. Method.

The method according to claim 6 , wherein an adhesion amount of the formed insulating film is 1.0 g / m ² or less per side.

The method in any one of Claim 6 thru | or 9 whose baking temperature (maximum reach | attainment board temperature) of a coating film exists in the range of 200-330 degreeC.