JP3981652B2

JP3981652B2 - Manufacturing method of unidirectional electrical steel sheet without inorganic material film such as forsterite, and annealing separator water slurry excellent in storage and coating properties

Info

Publication number: JP3981652B2
Application number: JP2003163834A
Authority: JP
Inventors: 浩康藤井; 收田中; 健一八ヶ代; 紀宏山本; 義行牛神; 健一村上; 修一中村; 修一山崎
Original assignee: Nittetsu Plant Designing Corp; Nippon Steel Corp
Current assignee: Nippon Steel Corp; Nippon Steel Plant Designing Corp
Priority date: 2003-06-09
Filing date: 2003-06-09
Publication date: 2007-09-26
Anticipated expiration: 2023-06-09
Also published as: JP2005002362A

Description

【０００１】
【発明の属する技術分野】
本発明は、フォルステライト（Ｍｇ₂ ＳｉＯ₄ ）等で構成される無機物質皮膜が仕上げ焼鈍中に生成するのを防止できる一方向性電磁鋼仕上げ焼鈍用の焼鈍分離剤水スラリーに関するものであって、該スラリーが、タンク内で沈殿を生じる事なく、安定に貯蔵でき、かつ、脱炭焼鈍板に対し、ロールコーター等の装置を用いて塗布する際、塗布ムラの発生なく高速度で塗布できる焼鈍分離剤水スラリー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ができ、皮膜密着性も優れている。
【０００３】
一方、特許文献１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。
【０００４】
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。
【０００５】
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、減殺させていることが明らかになってきた。そこで、例えば、特許文献２に開示されている如く、仕上げ焼鈍工程で生じるフォルステライト系皮膜を除去したり、更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、更なる鉄損低減を試みる技術が開発された。
【０００６】
しかしながら、鋼板側に嵌入した形態を取っているフォルステライト系皮膜を除去するには多大の労力を要する。例えば、酸洗によって除去しようとした場合、フォルステライトはシリカ成分を含んでいるので、酸液にはふっ酸など、シリカ成分をも溶解できる強力な酸液中に長時間浸漬する必要がある。また、機械的表面研削等の手段で除去しようとすれば、嵌入部分まで完全に除去するには１０μｍ近く研削する必要があり、歩留まり上からも採用しにくい。更には研削による皮膜除去法では研削の際に鋼板側への歪導入が不可避で、いくばくかの磁気特性の劣化を招いてしまうという欠点もあった。
【０００７】
このような認識のもと、仕上げ焼鈍工程で生成したフォルステライトを焼鈍後に除去するという方法ではなく、仕上げ焼鈍中にフォルステライト等の無機鉱物質の皮膜を形成させない技術が検討された。その中で、仕上げ焼鈍後に無機鉱物質が残留しにくい焼鈍分離剤としてアルミナが注目され、アルミナを主体とする焼鈍分離剤に関し、種々の技術が開示された。
【０００８】
まず、特許文献３において、純度９９％以上、粒度１００メッシュから４００メッシュのアルミナを焼鈍分離剤として用いる方法が、また、特許文献４においては、水酸化アルミニウムを主体とする焼鈍分離剤を用いる方法が開示された。
【０００９】
ついで、特許文献５においてはアルミナにほう酸成分を含むアルカリ金属化合物を添加した焼鈍分離剤を用いる方法が開示された。
【００１０】
更に、特許文献６に含水珪酸塩鉱物粉末を５から４０％含み、残部をアルミナとする焼鈍分離剤を用いる方法や、特許文献７には含水珪酸塩鉱物粉末の他にストロンチウムやバリウムの化合物を０．２％から２０％と、カルシアや水酸化カルシウムを２％から３０％含有し、残部をアルミナとする焼鈍分離剤を用いる技術がそれぞれ開示された。
【００１１】
最近では、特許文献８に平均粒径が１μｍから５０μｍの粗粒アルミナに平均粒径１μｍ以下の微粒アルミナを混合して使用する方法も開示されている。
【００１２】
アルミナ粉末を中心に開示された上述の技術はアルミナ粉末の粒径を規定したものが多く、特に、粗粒アルミナと呼ばれる粒径数十μｍ以上の粒径の大きなアルミナに関するものが多い。これは、粒径の小さいアルミナを使用した場合、鋼板へのアルミナの焼き付き、即ち、無機物質の残留が起こる一方で、粗粒アルミナの場合は焼き付きが比較的軽微である事が理由であると推測される。つまり、焼き付きの観点からはアルミナは粒径の大きいものが望ましい。ところが、焼鈍分離剤として粗粒アルミナを採用した場合、後述するような諸課題が発生してしまう。
【００１３】
粗粒アルミナを焼鈍分離剤として使用する場合の課題を説明する前に、方向性電磁鋼板の一般的な製造方法を冷間圧延以降の工程について説明する。
【００１４】
冷間圧延された鋼板はまず、鋼中からの炭素成分除去と鋼組織の一次再結晶を目的とし、脱炭焼鈍と呼ばれる、温度８５０℃前後での熱処理が施される。ついで、この脱炭焼鈍済みの鋼板に対し、鋼中から硫黄成分や窒素成分の除去と、二次再結晶と言う結晶粒の粗大化を目的として、仕上げ焼鈍と呼ばれる温度１２００℃前後の長時間焼鈍が行なわれる。
【００１５】
１２００℃と言う高温でかつ、鋼板をコイル状に重ねた状態で焼鈍を施す事から、鋼板どうしの焼き付きを防止するため、仕上げ焼鈍に先立ち、脱炭焼鈍板表面に水スラリー状態にした粒径２μｍ程度の微粒マグネシア粉末が塗布される。粒径２μｍ程度のマグネシア粉末は水スラリーを調製し、静置しても、その粒径が小さいが故に沈降速度がおそく、短時間のうちに沈殿を生じる事はなく、また、配管内で堆積し、管の閉塞を起こす事もない。更には、ロールコーターを使って鋼板に塗布する事も容易である。
【００１６】
ここで、微粒マグネシアに替えて、仕上げ焼鈍中に焼き付きが少ないと言われている粗粒アルミナを焼鈍分離剤として採用し、マグネシアと同じように水スラリー状態にした上で鋼板に塗布しようとした場合、次に説明するような課題が発生する。
【００１７】
粒径の大きなアルミナの場合、スラリーを攪拌し、せん断力を付加している間は特段、問題はないが、一旦攪拌を停止すると、アルミナと水とが極めて短時間のうちに分離し、アルミナが底部に沈殿してしまう。沈殿したアルミナは硬い堆積物を形成し、その除去には多大の労力を要する。また、アルミナ水スラリーを配管中、大きな流速で流している時は問題ないものの、流速を低下させたり、あるいは流通を止めた時はタンク中と同じく、アルミナが沈降、堆積し、ひいては配管を詰まらせてしまう。
【００１８】
そこで、貯蔵タンク中や配管内でのアルミナの沈殿を防止するため、スラリー粘度を増加させる方法が提案がなされた。例えば、特許文献９や特許文献１０には、スラリー安定性に加え、アルミナの鋼板への付着性確保をも目的として、水溶性高分子粘結剤を添加する方法が開示された。
【００１９】
【特許文献１】
特開昭４８−３９３３８号公報
【特許文献２】
特開昭４９−９６９２０号公報
【特許文献３】
米国特許３７８５８８２号公報
【特許文献４】
特開昭５６−６５９８３号公報
【特許文献５】
特公昭４８−１９０５０号公報
【特許文献６】
特公昭５６−３４１４号公報
【特許文献７】
特公昭５８−４４１５２号公報
【特許文献８】
特開平７−１８４５７号公報
【特許文献９】
特開平７−６２４２７号公報
【特許文献１０】
特開２０００−１１９７５５号公報
【００２０】
【発明が解決しようとする課題】
上述の技術、即ち、水溶性高分子粘結剤を添加し、粘度を増加させた水スラリーでは、アルミナの沈降を抑制した上で、アルミナの鋼板への付着性も向上でき、それなりの効果は認められる。しかしながら、特許文献９や特許文献１０で提案された、ポリビニルアルコールに代表される水溶性高分子を添加したスラリーは、粘度を単純に増加させるだけで、アルミナを分散させた水スラリーを長時間放置した時は、アルミナの沈殿が必然的に生じてしまう。そのため、貯蔵タンク等の流速がおそく、せん断力のかかりにくい状態でも、一定期間、沈殿発生を防止しようとすれば、相当に高濃度の液を作製せざるを得ない。そうした高濃度の水溶性高分子溶液では、確かにアルミナの沈殿をそれなりの期間、抑制できる。
【００２１】
但し、今度は鋼板への塗布工程において、次のような問題点が新たに起こってくる。即ち、スラリーをロールコーターで塗布しようとした際、液の粘度が高すぎると、鋼板とコーターロール間でのスラリーの分離が容易でないため、リング模様とかダブルトラックと称される、塗布ムラの発生が避けられない事態となる。塗布ムラ部のうち、塗布量の多い部分では塗布量の少ない部分の数倍、あるいは１０倍以上も厚くなる。一方、塗布量の少ない部分では場合によっては鋼板上に焼鈍分離剤がほとんど塗布されていない状態となる。
【００２２】
こうした塗布ムラの発生した鋼板では、仕上げ焼鈍中に板オレや変形を生じる。電磁鋼板では鋼板の変形はすぐさま磁気特性の劣化を招くので、最も回避すべき事とされている。また、焼鈍分離剤の塗布量が少ない部分では鋼板どうしの焼き付きが起こり、コイルの展開すらできない事態をも引き起こす。このような理由から、焼鈍分離剤の塗布ムラは出来るだけ起こさない事が必要である。
【００２３】
以上述べてきたように、粗粒アルミナの沈殿を防止する目的でスラリー粘度を増加させると言う方策は沈殿防止には有効であるが、塗布ムラを引き起こす事につながってしまう。逆に塗布ムラの発生を軽減するためには、スラリー粘度はできるだけ低い事が望ましいが、そうすると、今度はアルミナの沈殿が起こり易くなってしまう。
【００２４】
アルミナの沈殿防止の点からは高粘度のスラリーが、一方、塗布ムラ防止の点からは低粘度のスラリーが、それぞれ好ましいと言う結論で、この両立をいかにして果たすかが大きな技術課題であった。
【００２５】
【課題を解決するための手段】
本発明者らはスラリー粘度を増加させる増粘剤の特性を制御する事で、アルミナの沈殿防止と塗布ムラの発生防止とを両立できるのではないかと考えた。すなわち、貯蔵タンクにおいて攪拌を停止した時や流通を止めた配管内といった、スラリーに対しせん断力がかからなくなった時は、高い粘度を示し、アルミナの沈降を抑制する。一方で、ロールコーターで塗布する際のロールと鋼板の界面部分のような、大きなせん断力がかかり、塗布ムラ発生防止の観点からは低い粘度である事が望まれる状況では、低い粘度を示す、そのような粘度特性をもつスラリーにしてやれば課題を解決できるのではないかと考えた。
【００２６】
本発明者らは目標とするスラリー特性の把握を目指すとともに、目標のスラリー特性を持たせる事のできる手段がないか、種々、検討を重ねた。その結果、本目的に合致する粘度特性の把握に成功し、さらには、添加剤としてそうした特性を示す一連の化合物群を見出し、課題を解決する事に成功した。本発明の要旨は次の通りである。
【００２７】
（１）一方向性電磁鋼板用の脱炭焼鈍板に焼鈍分離剤水スラリーを塗布し、仕上げ焼鈍を施すに際し、前記焼鈍分離剤水スラリーがチキソトロピー性を有し、焼鈍分離剤水スラリーの粘度が（１）式と（２）式の両方を満足し、無機物質からなる増粘剤を添加し、前記無機物質の増粘剤が（３）式の化学組成式で表される結晶性板状スメクタイト群の粘土系物質であることを特徴とする鋼板上にフォルステライト皮膜のない一方向性電磁鋼板用仕上げ焼鈍板の製造方法。
（１）式：平衡粘度≦２００ｍＰａ・ｓ
（２）式：静置粘度≧５００ｍＰａ・ｓ
但し、平衡粘度は、ずり速度１０（１／秒）以上のせん断力で１０分間以上攪拌し、攪拌停止１５秒後にＢ型粘度計を用いて測定した粘度、静置粘度は同じく攪拌停止５分後に測定した粘度。
（３）式：｛Ｅ・ｎＨ _２Ｏ｝（Ｘ）［Ｙ］Ｏ _１０（Ｚ） _２
但し、｛｝内は層間物質を表し、Ｅは一価または二価の交換性陽イオン、ｎＨ _２Ｏは層間水を示す、また、ＸはＡｌ，Ｍｇ，Ｆｅ，Ｃｒ，Ｚｎ，Ｌｉのうちから選ばれる１種または２種以上の金属イオンで構造中で８面体型イオンを構成し、ＹはＳｉ，Ａｌのうちから選ばれる１種または２種の金属イオンで構造中で４面体型イオンを構成し、Ｚは水酸基またはハロゲン類である。
【００３３】
（２）前記無機物質の増粘剤の濃度が、水に対して１０質量％以下であることを特徴とする（１）記載の鋼板上にフォルステライト皮膜のない一方向性電磁鋼板用仕上げ焼鈍板の製造方法。
【００３４】
（３）焼鈍分離剤がアルミナ単独、またはマグネシア単独、またはアルミナとマグネシアの混合物であることを特徴とする（１）または（２）に記載の鋼板上にフォルステライト皮膜のない一方向性電磁鋼板用仕上げ焼鈍板の製造方法。
【００３５】
（４）鋼板上にフォルステライト皮膜のない一方向性電磁鋼用仕上げ焼鈍板を得るために、仕上げ焼鈍前に脱炭焼鈍板に塗布する焼鈍分離剤水スラリーであって、チキソトロピー性を有し、焼鈍分離剤水スラリーのチキソトロピー性粘度が（１）式と（２）式の両方を満足し、無機物質からなる増粘剤を添加し、前記増粘剤が（３）式の化学組成式で表される結晶性板状スメクタイト群の粘土系物質であることを特徴とする貯蔵性と塗布性に優れる焼鈍分離剤水スラリー。
（１）式：平衡粘度≦２００ｍＰａ・ｓ
（２）式：静置粘度≧５００ｍＰａ・ｓ
但し、平衡粘度は、ずり速度１０（１／秒）以上のせん断力で１０分間以上攪拌し、攪拌停止１５秒後にＢ型粘度計を用いて測定した粘度、静置粘度は同じく攪拌停止５分後に測定した粘度。
（３）式：｛Ｅ・ｎＨ _２Ｏ｝（Ｘ）［Ｙ］Ｏ _１０（Ｚ） _２
但し、｛｝内は層間物質を表し、Ｅは一価または二価の交換性陽イオン、ｎＨ _２Ｏは層間水を示す、また、ＸはＡｌ，Ｍｇ，Ｆｅ，Ｃｒ，Ｚｎ，Ｌｉのうちから選ばれる１種または２種以上の金属イオンで構造中で８面体型イオンを構成し、ＹはＳｉ，Ａｌのうちから選ばれる１種または２種の金属イオンで構造中で４面体型イオンを構成し、Ｚは水酸基またはハロゲン類である。
【００４１】
（５）前記増粘剤の濃度が水に対して１０質量％以下であることを特徴とする（４）記載の貯蔵性と塗布性に優れる焼鈍分離剤水スラリー。
【００４２】
（６）焼鈍分離剤がアルミナ単独、またはマグネシア単独、またはアルミナとマグネシアの混合物であることを特徴とする（４）または（５）に記載の貯蔵性と塗布性に優れる焼鈍分離剤水スラリー。
【００４３】
【発明の実施の形態】
以下、本発明を完成するに至った内容を詳細に説明する。
【００４４】
発明者らは、課題を解決するためにスラリーに具備させるべき粘度特性とは、チキソトロピー性ではないかと考えた。チキソトロピー性とは攪拌等のせん断力がかかると低い粘度を示し、いわゆる、サラサラとした状態になるが、時間が経過するにつれ、粘度が上昇し、ヨーグルトのような状態になり、攪拌等により、再度、せん断力をかけると元の低粘度状態に戻ると言う特性で、こうした特性が可逆的である時、チキソトロピー性があると言う。
【００４５】
本発明者らは、水溶液がチキソトロピー性をもつナトリウム−水酸基型ヘクトライトと、水溶液がチキソトロピー性をもたない有機高分子化合物である水溶性セルロースエーテル（分子量＝１０万）で、濃度の異なる水溶液を種々調製し、焼鈍分離剤であるアルミナ（平均粒径６０μｍ）を分散させ、その粘度を測定するとともに、アルミナの沈殿程度やロールコーターで塗布した時の塗布状況を評価した。
【００４６】
スラリーの調製と粘度の測定は次のような手順と条件で行った。
【００４７】
まず、深さ２５cm、直径１４cmの円筒形プラスティック製ビーカーに、増粘剤の濃度１質量％水溶液１２００ml入れ、ここに４５０ｇのアルミナ粉末を投入し、直径４cmのノコギリ羽根式攪拌機を用い、１５００回転／分のせん断力で１０分間攪拌した。この時のずり速度は３１（１／秒）であった。ついで、Ｂ型粘度計でＮｏ．１ローター、回転数１．５回／分の条件で攪拌停止１５秒後の粘度を測定した。この時の粘度を平衡粘度とした。その後、攪拌停止５分後に同じ条件で粘度を測定した。この時の粘度を静置粘度とした。温度は２０℃で測定した。
【００４８】
貯蔵性を示す、アルミナの沈殿状況の判定は、作製したスラリーを１００mlメスシリンダーに入れ、５分間経過した時に、底部におけるアルミナの沈殿有無を目視やガラス棒を用いて観察して評価した。評価は次の基準で行った。即ち、目視でアルミナ沈殿層と水相とが明瞭に区別でき、ガラス棒を用いて底部を押さえた時、硬いアルミナの沈殿層が生成した事が確認された場合を×、目視では沈殿の有無が確認できず、底部をガラス棒で押さえた時、柔らかい沈殿が生成している事が確認できた場合を○、沈殿が全く生成しなかった場合を◎と判定した。
【００４９】
塗布性は正回転ロールコーターを用い、板厚０．２３mmの脱炭焼鈍板にスラリーを塗布し、塗布ムラの発生度合いで評価した。鋼板金属面が露出している事が明らかに確認できるほど顕著な塗布ムラが発生した場合を×、小さな塗布ムラが発生した場合を○、塗布ムラが全く発生しなかった場合を◎と判定した。測定・評価結果を表１にまとめた。
【００５０】
【表１】

【００５１】
まず、増粘剤がナトリウム−水酸基型ヘクトライトであるスラリー番号１から７の評価結果について説明する。
【００５２】
貯蔵性が良好、即ち、アルミナの沈殿が少ないか全く生成しなかったのは、増粘剤濃度が０．１％から１５．０％で、静置粘度が５００ｍＰａ・ｓ以上のスラリー番号２から７の条件であった。スラリー番号１の増粘剤濃度が０．０５％で静置粘度が１５０ｍＰａ・ｓの条件ではアルミナの沈殿が生成し、貯蔵性と言う点では良好ではなかった。一方、塗布性が良好、即ち、ロールコーターでの塗りムラの発生が少ないか、全く発生しなかったのは増粘剤濃度が０．０５％から１０．０％で、平衡粘度が３５ｍＰａ・ｓから２００ｍＰａ・ｓのスラリー番号が１から６の条件であった。スラリー番号７の増粘剤濃度１５．０％で平衡粘度が３００ｍＰａ・ｓの条件では塗布ムラが発生し、塗布性の点からは良好ではなかった。
【００５３】
増粘剤がナトリウム−水酸基型ヘクトライトである系列の中で、総合的に評価した時、貯蔵性と塗布性が両立できるのは増粘剤濃度が０．１％から１０．０％、静置粘度が５００ｍＰａ・ｓ以上、平衡粘度が２００ｍＰａ・ｓ以下の条件であった。
【００５４】
次に、増粘剤がセルロースエーテルであるスラリー番号８から１１の評価結果について説明する。
【００５５】
貯蔵性が良好なのは、スラリー番号が１０と１１の増粘剤濃度が０．２と１．０％で、静置粘度が５５０ｍＰａ・ｓ以上の条件であった。スラリー番号８と９の増粘剤濃度が０．０５％と０．１％で静置粘度が５０ｍＰａ・ｓと１５０ｍＰａ・ｓの条件ではアルミナの沈殿が生成し、貯蔵性と言う点では良好ではなかった。一方、塗布性が良好なのはスラリー番号が８と９の増粘剤濃度が０．０５％と０．１％で、平衡粘度が５０ｍＰａ・ｓと１５０ｍＰａ・ｓの条件であった。スラリー番号１０と１１の増粘剤濃度０．２％と１．０％で平衡粘度が５５０ｍＰａ・ｓ以上の条件では塗布ムラが発生し、塗布性の点からは良好でなかった。
【００５６】
増粘剤がセルロースエーテルである系列の中で、総合的に評価して貯蔵性と塗布性が両立できる条件は見い出せなかった。
【００５７】
以上の結果から、次に述べる事が結論できる。
【００５８】
まず、チキソトロピー性をもつスラリーでは貯蔵性と塗布性を両立できる事がわかる。
【００５９】
特に、スラリーの粘度特性を静置粘度と平衡粘度と言う指標で定義した時、静置粘度が５００ｍＰａ・ｓ以上で、かつ、平衡粘度が２００ｍＰａ・ｓ以下のスラリーである時、貯蔵性と塗布性がともに良好である。
【００６０】
一方、チキソトロピー性を持たないスラリーでは貯蔵性と塗布性を両立できる条件が全く見出せなかった。これは、チキソトロピー性を持たないスラリー中において、粘度が時間経過とともに変化しない事に起因する。
【００６１】
塗布性を優先し、塗布ムラが発生しないよう、増粘剤濃度が低く、粘度の低い条件で作製したスラリーの場合、たしかに塗布ムラは発生しない。しかしながら、粘度が時間経過とともに変化しないため、スラリー中に分散させた粒子、例えば、アルミナ粒子の沈降が、いわゆるストークスの沈降速度式に従って起こる。一旦沈降を開始したアルミナ粒子は数分間程度静置すると液底に沈殿してしまう。つまり、貯蔵性と言う点からは適していない。
【００６２】
逆に、貯蔵性を優先し、増粘剤濃度を高め、粘度を高めたスラリーでは、ある程度の期間、アルミナの沈殿を抑制する事は可能である。しかしながら、今度はロールコーターで塗布しようとした時、粘度が高過ぎるため、激しい塗布ムラが発生してしまう。つまり、塗布性と言う点では適していない。
【００６３】
本発明に開示した、時間経過とともにスラリー粘度が上昇するチキソトロピー性を持つスラリーの場合、粘度が時間とともに上昇し、スラリー中に分散した粒子、例えば、アルミナ粒子の沈降自体がそもそも開始しない。言い換えると、ストークス式による沈降自体が起きることがない。アルミナ粒子の沈降そのものが始まらないので、アルミナの顕著な沈殿が生じる事がないわけである。
【００６４】
また、静置によってスラリー粘度が上昇しても、スラリーに対し、再度、せん断力をかけると、もとの低粘度に容易に戻るので、ロールコーター等で塗布しようとした場合、塗布ムラの発生なく、塗布する事が可能となる。
【００６５】
ただし、増粘剤が有機物である場合、仕上げ焼鈍中に浸炭反応が起こし、炭素分が鋼中に浸入してしまう可能性がある。浸炭した炭素分は鋼中で介在物を形成し、磁気特性を劣化させる。そのため、浸炭反応防止と言う点から、使用する増粘剤は無機物質である事が望ましい。
【００６６】
本発明者らは無機物質の中で増粘作用のある物質を選択し、水溶液を作製し評価を重ねた。その結果、結晶性板状スメクタイト群の粘土系物質が優れている事を突き止めた。結晶性板状スメクタイト群の粘土系物質とは、（３）式の化学組成式で表される一群の物質である。
【００６７】
（３）式：｛Ｅ・ｎＨ₂ Ｏ｝（Ｘ）［Ｙ］Ｏ₁₀（Ｚ）₂
ここで｛｝内は層間物質を表し、Ｅは一価または二価の交換性陽イオン、ｎＨ₂ Ｏは層間水を示す、また、ＸはＡｌ，Ｍｇ，Ｆｅ，Ｃｒ，Ｚｎ，Ｌｉのうちから選ばれる１種または２種以上の金属イオンで構造中で８面体型イオンを構成し、ＹはＳｉ，Ａｌのうちから選ばれる１種または２種の金属イオンで構造中で４面体型イオンを構成し、Ｚは水酸基またはハロゲン類である。
【００６８】
表１に示した評価実験はＥ（交換性陽イオン）がＮａで、かつＺがＯＨ（水酸基）であるナトリウム−水酸基型のヘクトライトで、結晶性板状スメクタイト群の粘土系物質の１つである。
【００６９】
本発明者らは、以下に述べる一連の評価実験から、結晶性板状スメクタイト群の粘土系物質を添加したスラリーがチキソトロピー性に優れ、貯蔵性と塗布性とを両立できる事を確認した。
【００７０】
まず、（３）式におけるＥの交換性陽イオンがナトリウムで、Ｚは水酸基（ＯＨ）ではなくふっ素（Ｆ）である、ナトリウム−ふっ素型ヘクトライトで評価した。スラリー作製は表１に示した実験と同じ条件で実施し、貯蔵性と塗布性の評価も表１で示した実験と同じ基準で行なった。結果を表２にまとめた。
【００７１】
【表２】

【００７２】
静置粘度と平衡粘度の異なる、チキソトロピー性を示すＮａ−Ｆ型ヘクトライトを増粘剤として用いる場合は、Ｎａ−ＯＨ型ヘクトライトを増粘剤として用いる場合と同様に、貯蔵性と塗布性を両立できるアルミナ水スラリーを実現できる事がわかった。
【００７３】
特に、貯蔵性と塗布性が良好なのは静置粘度が５００ｍＰａ・ｓ以上、平衡粘度が２００ｍＰａ・ｓ以下の条件であった。この時、増粘剤の濃度は０．１％から１０．０％であった。
【００７４】
更に、本発明者らは表３に示す一連の結晶性板状スメクタイト群の粘土系物質を増粘剤とする濃度１．０％の水溶液を調製の後、アルミナ水スラリーを作り、その貯蔵性と塗布性を評価した。スラリー作製や粘度測定は表１でまとめた評価実験と同じ条件でおこなった。比較例として分子量１０万のセルロースエーテルの１％水溶液も調製し、評価した。評価結果を表３にまとめた。
【００７５】
【表３】

【００７６】
静置粘度と平衡粘度が異なる、チキソトロピー性を示すスラリー番号１から７の、結晶性板状スメクタイト群の粘土系物質を増粘剤として形成した水スラリーにおいては、貯蔵性と塗布性を両立できる事がわかった。特に、貯蔵性と塗布性が良好なのは静置粘度が５００ｍＰａ・ｓ以上、平衡粘度が２００ｍＰａ・ｓ以下の条件であった。
【００７７】
以上の事から、（３）式で表される結晶性板状スメクタイト群の粘土系物質を増粘剤として形成した水スラリーは、貯蔵性と塗布性を両立できるチキソトロピー性を発現できることが確認できた。
【００７８】
本発明に適用できる結晶性板状スメクタイト群の粘土系物質として、Ｚが水酸基型のものとしては次のようなものが挙げられる。ここでは｛Ｅ_1/3 ・ｎＨ₂ Ｏ｝の部分を省略して示すが、Ｅの交換性陽イオンとしてはナトリウムやマグネシウムが一般的であり、これらの１種または２種以上の混合物を適用すれば良い。
【００７９】

また、Ｚがふっ素型のものとしては次のようなものが本発明に適している。
【００８０】

増粘剤濃度は、水に対して１０質量％を越えると鋼板の鏡面化度に影響を及ぼす可能性があるので１０質量％以下にする事が好ましい。
【００８１】
本発明で開示した増粘剤は焼鈍分離剤の種類を問わず活用できるが、焼鈍分離剤の主体がアルミナ単独、またはマグネシア単独、またはアルミナとマグネシアの混合物などの時、特に有効である。特に、鋼板鏡面化には適しているものの、スラリー中で沈降を起こしやすいが故に、従来使用条件が狭かった、粒径数μｍ以上のアルミナまたはマグネシアの沈降防止に絶大な効果を発揮すると同時に、ロールコーターで塗布し易いスラリーを形成できる。
【００８２】
【実施例】
＜実施例１＞
水溶液がチキソトロピー性をもつナトリウム−水酸基型ヘクトライトとチキソトロピー性をもたない有機高分子化合物である水溶性セルロースエーテル（分子量＝１０万）の１．０質量％の水溶液１２００mlをそれぞれ、深さ２５cm、直径１４cmの円筒形プラスティック製ビーカーに、ここに焼鈍分離剤であるアルミナ４５０ｇを入れ、直径４cmのノコギリ羽根式攪拌機を用い、５００回転／分のせん断力で３０分間攪拌した。この時のずり速度は１１（１／秒）であった。ついで、Ｂ型粘度計でＮｏ．１ローター、回転数１．５回／分の条件で攪拌停止１５秒後粘度を測定した。この時の粘度を平衡粘度とした。その後、攪拌停止５分後に同じ条件で粘度を測定した。この時の粘度を静置粘度とした。粘度は温度２０℃の条件で測定した。
【００８３】
貯蔵性と塗布性の評価は表１で示した実験と同じ条件と基準で行なった。測定・評価結果を表４にまとめた。
【００８４】
【表４】

【００８５】
比較例であるセルロースエーテルを増粘剤とするスラリー番号２の条件ではアルミナの顕著な沈殿は起こらず、貯蔵性は良好であるものの、スラリー粘度が高すぎるため、塗布ムラの発生が激しく、塗布性は極めて悪かった。
【００８６】
一方、実施例であるＮａ−ＯＨ型ヘクトライトを増粘剤とするスラリー番号１の条件ではアルミナの沈殿がなく貯蔵性に優れる上、塗布ムラの発生がなく、塗布性も優れていた。
【００８７】
なお、実施例であるスラリー番号１の水スラリーを厚さ０．２３mmの脱炭焼鈍済みの鋼板に塗布し、仕上げ焼鈍を実施したところ、アルミナの焼き付きが無く、鏡面光沢を呈する二次再結晶済みの鋼板を得る事ができた。
＜実施例２＞
水溶液がチキソトロピー性をもつナトリウム／マグネシウム−水酸基型サポナイトとチキソトロピー性をもたない有機高分子化合物である水溶性セルロースエーテル（分子量＝１０万）の１．０質量％の水溶液１２００mlをそれぞれ、深さ２５cm、直径１４cmの円筒形プラスティック製ビーカーに入れ、ここに焼鈍分離剤であるアルミナ４５０ｇを入れ、直径４cmのノコギリ羽根式攪拌機を用い、２５００回転／分のせん断力で１０分間攪拌した。この時のずり速度は５２（１／秒）であった。ついで、Ｂ型粘度計でＮｏ．１ローター、回転数１．５回／分の条件で攪拌停止１５秒後粘度を測定した。この時の粘度を平衡粘度とした。その後、攪拌停止５分後に同じ条件で粘度を測定した。この時の粘度を静置粘度とした。粘度は温度２０℃の条件で測定した。貯蔵性と塗布性の評価は表１で示した実験と同じ条件と基準で行なった。測定・評価結果を表５にまとめた。
【００８８】
【表５】

【００８９】
比較例である、セルロースエーテルを増粘剤とするスラリー番号２の条件では、アルミナの顕著な沈殿は起こらず、貯蔵性は良好であるものの、スラリー粘度が高すぎるため、塗布ムラの発生が激しく、塗布性は極めて悪かった。
【００９０】
一方、実施例であるＮａ／Ｍｇ−ＯＨ型サポナイトを増粘剤とするスラリー番号１の条件ではアルミナの沈殿がなく貯蔵性に優れる上、塗布ムラの発生もなく、塗布性も優れていた。
【００９１】
なお、実施例であるスラリー番号１の水スラリーを厚さ０．２３mmの脱炭焼鈍済みの鋼板に塗布し、仕上げ焼鈍を実施したところ、アルミナの焼き付きが無く、鏡面光沢を呈する二次再結晶済みの鋼板を得る事ができた。
＜実施例３＞
水溶液がチキソトロピー性をもつナトリウム−ふっ素型ヘクトライトとチキソトロピー性をもたない有機高分子化合物である水溶性セルロースエーテル（分子量＝１０万）の１．０質量％の水溶液１２００mlをそれぞれ、深さ２５cm、直径１４cmの円筒形プラスティック製ビーカーに入れ、ここに焼鈍分離剤であるアルミナ４５０ｇを入れ、直径４cmのノコギリ羽根式攪拌機を用い、１５００回転／分のせん断力で１５分間攪拌した。この時のずり速度は３１（１／秒）であった。ついで、Ｂ型粘度計でＮｏ．１ローター、回転数１．５回／分の条件で攪拌停止１５秒後粘度を測定した。この時の粘度を平衡粘度とした。その後、攪拌停止５分後に同じ条件で粘度を測定した。この時の粘度を静置粘度とした。粘度は温度２０℃の条件で測定した。貯蔵性と塗布性の評価は表１で示した実験と同じ条件と基準で行なった。測定・評価結果を表６にまとめた。
【００９２】
【表６】

【００９３】
比較例である、セルロースエーテルを増粘剤とするスラリー番号２の条件では、アルミナの顕著な沈殿は起こらず、貯蔵性は良好であるものの、スラリー粘度が高すぎるため、塗布ムラの発生が激しく、塗布性は極めて悪かった。
【００９４】
一方、実施例であるＮａ−Ｆ型ヘクトライトを増粘剤とするスラリー番号１の条件ではアルミナの沈殿がなく貯蔵性に優れる上、塗布ムラの発生もなく、塗布性も優れていた。
【００９５】
なお、実施例であるスラリー番号１の水スラリーを厚さ０．２３mmの脱炭焼鈍済みの鋼板に塗布し、仕上げ焼鈍を実施したところ、アルミナの焼き付きが無く、鏡面光沢を呈する二次再結晶済みの鋼板を得る事ができた。
【００９６】
【発明の効果】
以上述べたように本発明によれば、フォルステライト等の無機物質皮膜のない一方向性電磁鋼用仕上げ焼鈍板の製造に用いる焼鈍分離剤水スラリーとして、タンクや配管での焼鈍分離剤の沈殿防止とロールコーターでの塗布性、すなわち焼鈍分離剤スラリーの貯蔵性と塗布性を両立させることができるので、産業上の効果は大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to forsterite (Mg₂ SiO_Four ), Etc., which relates to an aqueous slurry for annealing separator for unidirectional electrical steel finish annealing that can prevent formation of an inorganic material film during finish annealing, and the slurry causes precipitation in a tank. The present invention relates to an annealing separator water slurry that can be stably stored and applied to a decarburized and annealed plate using a roll coater or the like at a high speed without application unevenness.
[0002]
[Prior art]
Unidirectional silicon steel sheets are frequently 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-based film produced by the reaction of the oxide on the surface of the steel sheet and the annealing separator in the final annealing step can give tension to the steel sheet and has excellent film adhesion.
[0003]
On the other hand, the method of forming an insulating film by applying the coating liquid mainly composed of colloidal silica and phosphate disclosed in Patent Document 1 to the surface of the steel sheet and baking it has a great effect of imparting tension to the steel sheet. It is effective for reducing loss.
[0004]
Therefore, it is a general method for producing a unidirectional silicon steel sheet to leave the forsterite-based film produced in the finish annealing step and form an insulating film mainly composed of phosphate.
[0005]
In recent years, it has been clarified that the interface structure in which the forsterite film and the ground iron are disturbed reduces the iron loss improvement effect by the film tension to some extent. Therefore, for example, as disclosed in Patent Document 2, after removing the forsterite-based film generated in the finish annealing process or performing a mirror-finished finish, a further tension loss film is formed to further increase the iron loss. Technology to try to reduce it has been developed.
[0006]
However, a great deal of labor is required to remove the forsterite film that is in the form of being fitted on the steel plate side. For example, when removing by pickling, forsterite contains a silica component, the acid solution needs to be immersed in a strong acid solution capable of dissolving the silica component such as hydrofluoric acid for a long time. Further, if it is intended to be removed by means such as mechanical surface grinding, it is necessary to grind nearly 10 μm in order to completely remove the inserted portion, and it is difficult to adopt from the viewpoint of yield. Furthermore, in the film removal method by grinding, it is inevitable that strain is introduced into the steel plate side during grinding, and there is also a drawback that some magnetic characteristics are deteriorated.
[0007]
Based on this recognition, a technique that does not form a film of an inorganic mineral substance such as forsterite during the final annealing was examined instead of the method of removing the forsterite generated in the final annealing process after the annealing. Among them, alumina has attracted attention as an annealing separator that hardly retains inorganic minerals after finish annealing, and various techniques have been disclosed regarding an annealing separator mainly composed of alumina.
[0008]
First, in Patent Document 3, a method using alumina having a purity of 99% or more and a particle size of 100 mesh to 400 mesh as an annealing separator, and in Patent Document 4, a method using an annealing separator mainly composed of aluminum hydroxide. Was disclosed.
[0009]
Next, Patent Document 5 discloses a method using an annealing separator in which an alkali metal compound containing a boric acid component is added to alumina.
[0010]
Further, Patent Document 6 includes a method using an annealing separator containing 5 to 40% hydrated silicate mineral powder and the remainder being alumina, and Patent Document 7 includes strontium and barium compounds in addition to the hydrated silicate mineral powder. Techniques using an annealing separator containing 0.2% to 20%, 2% to 30% calcia and calcium hydroxide, and the balance being alumina have been disclosed.
[0011]
Recently, Patent Document 8 discloses a method in which coarse alumina having an average particle diameter of 1 μm to 50 μm is mixed with fine alumina having an average particle diameter of 1 μm or less.
[0012]
Many of the above-described techniques disclosed centering on alumina powder define the particle size of alumina powder, and in particular, there are many related to alumina having a large particle size of several tens of μm or more called coarse-grained alumina. This is because when alumina having a small particle diameter is used, alumina is seized onto the steel sheet, that is, inorganic substances remain, while in the case of coarse alumina, the seizure is relatively slight. Guessed. That is, from the viewpoint of seizure, alumina having a large particle size is desirable. However, when coarse-grained alumina is employed as the annealing separator, problems as described later occur.
[0013]
Before explaining the problem when using coarse-grained alumina as an annealing separator, a general method for producing a grain-oriented electrical steel sheet will be described with respect to the steps after cold rolling.
[0014]
The cold-rolled steel sheet is first subjected to heat treatment at a temperature of about 850 ° C., called decarburization annealing, for the purpose of removing carbon components from the steel and primary recrystallization of the steel structure. Next, for this decarburized and annealed steel sheet, for the purpose of removing sulfur components and nitrogen components from the steel and coarsening of crystal grains called secondary recrystallization, a long time of about 1200 ° C. called final annealing is performed. Annealing is performed.
[0015]
Since the annealing is performed at a high temperature of 1200 ° C. and the steel plates are stacked in a coil shape, the particle size of the decarburized and annealed plate surface in a water slurry state prior to the finish annealing in order to prevent the steel plates from being seized. A fine magnesia powder of about 2 μm is applied. The magnesia powder with a particle size of about 2μm is prepared in water slurry, and even if it is allowed to stand, its particle size is small, so the settling speed is slow, and no precipitation occurs in a short time. However, the tube does not become blocked. Furthermore, it is easy to apply to a steel plate using a roll coater.
[0016]
Here, instead of fine-grained magnesia, coarse alumina, which is said to have less seizure during finish annealing, was adopted as an annealing separator. In such a case, the problem described below occurs.
[0017]
In the case of alumina having a large particle size, there is no particular problem while stirring the slurry and applying the shearing force, but once the stirring is stopped, the alumina and water are separated in a very short time, and the alumina Will settle to the bottom. Precipitated alumina forms hard deposits that require a lot of effort to remove. Also, although there is no problem when the alumina water slurry is flowing at a high flow rate in the piping, when the flow rate is reduced or the flow is stopped, the alumina settles and deposits as in the tank and eventually clogs the piping. I will let you.
[0018]
Therefore, a method for increasing the slurry viscosity has been proposed in order to prevent precipitation of alumina in the storage tank or in the piping. For example, Patent Document 9 and Patent Document 10 disclosed a method of adding a water-soluble polymer binder for the purpose of ensuring adhesion of alumina to a steel sheet in addition to slurry stability.
[0019]
[Patent Document 1]
JP 48-39338 A
[Patent Document 2]
JP-A 49-96920
[Patent Document 3]
U.S. Pat. No. 3,785,882
[Patent Document 4]
JP-A-56-65983
[Patent Document 5]
Japanese Patent Publication No. 48-19050
[Patent Document 6]
Japanese Patent Publication No.56-3414
[Patent Document 7]
Japanese Examined Patent Publication No. 58-44152
[Patent Document 8]
Japanese Patent Laid-Open No. 7-18457
[Patent Document 9]
JP 7-62427 A
[Patent Document 10]
JP 2000-119755 A
[0020]
[Problems to be solved by the invention]
In the above-described technique, that is, a water slurry in which a water-soluble polymer binder is added to increase the viscosity, the alumina can be prevented from settling and the adhesion of alumina to the steel sheet can be improved. Is recognized. However, the slurry added with a water-soluble polymer typified by polyvinyl alcohol proposed in Patent Document 9 and Patent Document 10 simply left the water slurry in which alumina was dispersed for a long time simply by increasing the viscosity. When this occurs, precipitation of alumina will inevitably occur. Therefore, even if the flow rate of the storage tank or the like is slow and it is difficult to apply a shearing force, if a precipitation is to be prevented for a certain period, a considerably high concentration liquid must be prepared. Such a high-concentration water-soluble polymer solution can certainly suppress the precipitation of alumina for a reasonable period of time.
[0021]
However, this time, the following new problems occur in the coating process on the steel sheet. That is, when trying to apply the slurry with a roll coater, if the viscosity of the liquid is too high, it is not easy to separate the slurry between the steel plate and the coater roll. Is an unavoidable situation. Of the uneven coating portion, the portion with a large coating amount is several times thicker than the portion with a small coating amount, or 10 times or more. On the other hand, in a portion with a small amount of application, the annealing separator is hardly applied on the steel sheet in some cases.
[0022]
In the steel plate in which such coating unevenness occurs, the plate and deformation occur during finish annealing. In electrical steel sheets, deformation of the steel sheet immediately leads to deterioration of magnetic properties, and it is considered to be most avoided. Further, in a portion where the application amount of the annealing separator is small, the steel plates are seized and cause a situation where even the coil cannot be developed. For these reasons, it is necessary to prevent uneven application of the annealing separator as much as possible.
[0023]
As described above, the measure of increasing the slurry viscosity for the purpose of preventing the precipitation of coarse-grained alumina is effective in preventing the precipitation, but leads to uneven coating. Conversely, in order to reduce the occurrence of coating unevenness, it is desirable that the slurry viscosity is as low as possible. However, in this case, precipitation of alumina is likely to occur.
[0024]
From the point of view of preventing alumina precipitation, a high-viscosity slurry is preferable, while from the point of preventing coating unevenness, a low-viscosity slurry is preferable. It was.
[0025]
[Means for Solving the Problems]
The inventors of the present invention thought that it was possible to achieve both prevention of alumina precipitation and prevention of uneven coating by controlling the properties of the thickener that increases the slurry viscosity. That is, when the shearing force is no longer applied to the slurry, such as when the agitation is stopped in the storage tank or in the piping where the circulation is stopped, the slurry exhibits high viscosity and suppresses the settling of alumina. On the other hand, a large shearing force is applied, such as the interface between the roll and the steel sheet when applied with a roll coater, and in a situation where a low viscosity is desired from the viewpoint of preventing uneven coating, a low viscosity is shown. We thought that the problem could be solved if the slurry had such viscosity characteristics.
[0026]
The inventors of the present invention have made various investigations as to whether or not there is a means capable of providing the target slurry characteristics while grasping the target slurry characteristics. As a result, we succeeded in grasping the viscosity characteristics meeting this purpose, and found a series of compounds showing such characteristics as additives and succeeded in solving the problems. The gist of the present invention is as follows.
[0027]
(1) When the annealing separator water slurry is applied to a decarburized annealing plate for a unidirectional electrical steel sheet and subjected to finish annealing, the annealing separator water slurry has thixotropic properties.In addition, the viscosity of the annealing separator water slurry satisfies both the formulas (1) and (2), and a thickener made of an inorganic substance is added. It is a clay-based material of the crystalline plate-like smectite group represented by the composition formulaA method for producing a finish-annealed plate for a unidirectional electrical steel sheet having no forsterite film on the steel sheet.
(1) Formula: Equilibrium viscosity ≦ 200 mPa · s
(2) Formula: Static viscosity ≧ 500 mPa · s
However, the equilibrium viscosity is stirred for 10 minutes or more with a shearing force of 10 (1 / second) or higher, and the viscosity measured using a B-type viscometer after 15 seconds of stirring is stopped, and the static viscosity is also 5 minutes after stirring. Viscosity measured later.
(3) Formula: {E · nH ₂ O} (X) [Y] O ₁₀ (Z) ₂
However, {} represents an interlayer substance, E is a monovalent or divalent exchangeable cation, nH ₂ O represents interlayer water, X represents octahedral ions in the structure with one or more metal ions selected from Al, Mg, Fe, Cr, Zn, and Li, and Y represents One or two metal ions selected from Si and Al form a tetrahedral ion in the structure, and Z is a hydroxyl group or a halogen.
[0033]
(2)The concentration of the inorganic thickener is 10% by mass or less with respect to water.(1)A method for producing a finish-annealed plate for a unidirectional electrical steel sheet having no forsterite film on the steel sheet described.
[0034]
(3)The annealing separator is alumina alone, magnesia alone, or a mixture of alumina and magnesia.(1) or (2)The manufacturing method of the finish annealing plate for unidirectional electrical steel sheets which does not have a forsterite film | membrane on the steel plate of description.
[0035]
(4)An annealing separator water slurry applied to a decarburized annealed plate before finish annealing to obtain a finish annealed plate for unidirectional electrical steel without a forsterite film on the steel plate, and has thixotropic properties.In addition, the thixotropic viscosity of the annealing separator water slurry satisfies both the formulas (1) and (2), a thickener made of an inorganic substance is added, and the thickener is a chemical composition of the formula (3) It is a clay-based material of the crystalline plate-like smectite group represented by the formulaAn annealing separator water slurry excellent in storability and applicability.
(1) Formula: Equilibrium viscosity ≦ 200 mPa · s
(2) Formula: Static viscosity ≧ 500 mPa · s
However, the equilibrium viscosity is stirred for 10 minutes or more with a shearing force of 10 (1 / second) or higher, and the viscosity measured using a B-type viscometer after 15 seconds of stirring is stopped, and the static viscosity is also 5 minutes after stirring. Viscosity measured later.
(3) Formula: {E · nH ₂ O} (X) [Y] O ₁₀ (Z) ₂
However, {} represents an interlayer substance, E is a monovalent or divalent exchangeable cation, nH ₂ O represents interlayer water, X represents octahedral ions in the structure with one or more metal ions selected from Al, Mg, Fe, Cr, Zn, and Li, and Y represents One or two metal ions selected from Si and Al form a tetrahedral ion in the structure, and Z is a hydroxyl group or a halogen.
[0041]
(5)The concentration of the thickener is 10% by mass or less with respect to water.(4)An annealing separator water slurry having excellent storage and coating properties.
[0042]
(6)The annealing separator is alumina alone, magnesia alone, or a mixture of alumina and magnesia.(4) or (5)An annealing separator water slurry excellent in storability and applicability described in 1.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the contents that led to the completion of the present invention will be described in detail.
[0044]
In order to solve the problem, the inventors thought that the viscosity characteristic to be provided in the slurry is thixotropic property. Thixotropic property indicates a low viscosity when a shearing force such as stirring is applied, and it becomes a so-called smooth state, but as time passes, the viscosity increases and becomes a yogurt-like state. When the shearing force is applied again, it returns to its original low viscosity state. When these properties are reversible, it is said to have thixotropic properties.
[0045]
The inventors of the present invention are aqueous solutions having different concentrations of sodium-hydroxyl type hectorite having thixotropic properties and water-soluble cellulose ether (molecular weight = 100,000) which is an organic polymer compound having no thixotropic properties. Were prepared, and an alumina (an average particle size of 60 μm) as an annealing separator was dispersed, the viscosity was measured, and the degree of precipitation of alumina and the coating condition when coated with a roll coater were evaluated.
[0046]
The slurry was prepared and the viscosity was measured according to the following procedure and conditions.
[0047]
First, in a cylindrical plastic beaker having a depth of 25 cm and a diameter of 14 cm, 1200 ml of a 1% by weight aqueous solution of a thickener is placed, 450 g of alumina powder is put therein, and a 1500-rpm saw blade agitator is used. The mixture was stirred for 10 minutes with a shearing force of / min. The shear rate at this time was 31 (1 / second). Next, with a B-type viscometer, No. The viscosity was measured 15 seconds after the stirring was stopped under the condition of 1 rotor and a rotational speed of 1.5 times / minute. The viscosity at this time was defined as an equilibrium viscosity. Thereafter, the viscosity was measured under the same conditions 5 minutes after stirring was stopped. The viscosity at this time was defined as a static viscosity. The temperature was measured at 20 ° C.
[0048]
Judgment of the state of precipitation of alumina, which indicates storability, was evaluated by placing the prepared slurry in a 100 ml graduated cylinder and observing the presence or absence of precipitation of alumina at the bottom using a visual or glass rod when 5 minutes had passed. Evaluation was performed according to the following criteria. That is, when the alumina precipitation layer and the aqueous phase can be clearly distinguished visually, and when the bottom is pressed with a glass rod, it is confirmed that a hard alumina precipitation layer has been formed. When it was not confirmed and it was confirmed that a soft precipitate was formed when the bottom part was pressed with a glass rod, it was judged as ◯, and when no precipitate was formed at all, it was judged as ◎.
[0049]
The coating property was evaluated by the degree of occurrence of coating unevenness by applying a slurry to a decarburized and annealed plate having a thickness of 0.23 mm using a forward rotating roll coater. The case where the coating unevenness was so noticeable that the steel plate metal surface was clearly confirmed was judged as x, the case where the small coating unevenness occurred was judged as ◯, and the case where the coating unevenness did not occur at all was judged as ◎. . The measurement and evaluation results are summarized in Table 1.
[0050]
[Table 1]

[0051]
First, the evaluation results of slurry numbers 1 to 7 in which the thickener is sodium-hydroxyl type hectorite will be described.
[0052]
The storage stability was good, that is, the precipitate of alumina was little or not produced at all from the slurry No. 2 having a thickener concentration of 0.1% to 15.0% and a static viscosity of 500 mPa · s or more. The condition was 7. Under the conditions where the thickener concentration of slurry No. 1 was 0.05% and the static viscosity was 150 mPa · s, precipitation of alumina was generated, which was not good in terms of storability. On the other hand, the coating property was good, that is, the occurrence of uneven coating on the roll coater was little or not at all. The thickener concentration was 0.05% to 10.0%, and the equilibrium viscosity was 35 mPa · s. The slurry number from 1 to 200 mPa · s was from 1 to 6. Under the condition that the thickener concentration of the slurry No. 7 was 15.0% and the equilibrium viscosity was 300 mPa · s, coating unevenness occurred, which was not good in terms of coating properties.
[0053]
Among the series in which the thickener is a sodium-hydroxyl type hectorite, when comprehensively evaluated, it is possible to achieve both storage properties and coating properties with a thickener concentration of 0.1% to 10.0%, static The in-situ viscosity was 500 mPa · s or more and the equilibrium viscosity was 200 mPa · s or less.
[0054]
Next, the evaluation results of slurry numbers 8 to 11 in which the thickener is cellulose ether will be described.
[0055]
The storage stability was good under the conditions where the thickener concentrations of slurry numbers 10 and 11 were 0.2 and 1.0%, and the static viscosity was 550 mPa · s or more. Under the conditions where the thickener concentrations of the slurry numbers 8 and 9 are 0.05% and 0.1% and the static viscosities are 50 mPa · s and 150 mPa · s, precipitation of alumina is generated, which is not good in terms of storability. There wasn't. On the other hand, the coating properties were good when the thickener concentrations of slurry numbers 8 and 9 were 0.05% and 0.1%, and the equilibrium viscosities were 50 mPa · s and 150 mPa · s. Under the conditions where the thickener concentrations of slurry numbers 10 and 11 were 0.2% and 1.0% and the equilibrium viscosity was 550 mPa · s or more, coating unevenness occurred, which was not good in terms of coating properties.
[0056]
In the series in which the thickener is cellulose ether, it was not possible to find a condition that could be comprehensively evaluated to achieve both storage and coating properties.
[0057]
From the above results, the following can be concluded.
[0058]
First, it can be seen that a slurry having thixotropic properties can achieve both storage and coating properties.
[0059]
In particular, when the viscosity characteristics of the slurry are defined by the indices of static viscosity and equilibrium viscosity, when the static viscosity is 500 mPa · s or more and the equilibrium viscosity is 200 mPa · s or less, the storability and coating Both properties are good.
[0060]
On the other hand, in a slurry having no thixotropy, no conditions were found that can achieve both storage and coating properties. This is due to the fact that the viscosity does not change over time in a slurry that does not have thixotropic properties.
[0061]
In the case of a slurry prepared under conditions where the thickening agent concentration is low and the viscosity is low so that the coating property is given priority and coating unevenness does not occur, the coating unevenness does not occur. However, since the viscosity does not change with the passage of time, the particles dispersed in the slurry, for example, alumina particles, settle according to the so-called Stokes sedimentation rate equation. Once the alumina particles have started to settle, they will settle to the bottom of the liquid when left for a few minutes. In other words, it is not suitable from the viewpoint of storability.
[0062]
On the contrary, it is possible to suppress the precipitation of alumina for a certain period of time in a slurry in which storage property is given priority, the thickener concentration is increased, and the viscosity is increased. However, this time, when trying to apply with a roll coater, since the viscosity is too high, intense application unevenness occurs. That is, it is not suitable in terms of applicability.
[0063]
In the case of a slurry having a thixotropic property in which the slurry viscosity increases with the lapse of time disclosed in the present invention, the viscosity increases with time, and sedimentation of particles dispersed in the slurry, for example, alumina particles themselves does not start in the first place. In other words, sedimentation by the Stokes equation itself does not occur. Since the precipitation of the alumina particles itself does not start, no significant precipitation of alumina occurs.
[0064]
Even if the slurry viscosity rises due to standing, if a shear force is applied to the slurry again, it will easily return to its original low viscosity. It becomes possible to apply without.
[0065]
However, when the thickener is an organic substance, a carburization reaction may occur during finish annealing, and the carbon content may enter the steel. Carburized carbon forms inclusions in the steel and degrades the magnetic properties. Therefore, it is desirable that the thickener used is an inorganic substance from the viewpoint of preventing carburization reaction.
[0066]
The inventors selected a substance having a thickening action among inorganic substances, produced an aqueous solution, and repeated evaluation. As a result, it was found that the clay-based material of the crystalline plate-like smectite group is excellent. The clay-based material of the crystalline plate-like smectite group is a group of materials represented by the chemical composition formula (3).
[0067]
(3) Formula: {E · nH₂ O} (X) [Y] O_Ten(Z)₂
Here, {} represents an interlayer substance, E is a monovalent or divalent exchangeable cation, nH₂ O represents interlayer water, X represents octahedral ions in the structure with one or more metal ions selected from Al, Mg, Fe, Cr, Zn, and Li, and Y represents One or two metal ions selected from Si and Al form a tetrahedral ion in the structure, and Z is a hydroxyl group or a halogen.
[0068]
The evaluation experiment shown in Table 1 is a sodium-hydroxyl type hectorite in which E (exchangeable cation) is Na and Z is OH (hydroxyl group), and is one of the clay-based materials of the crystalline plate-like smectite group. It is.
[0069]
The present inventors have confirmed from a series of evaluation experiments described below that a slurry to which a clay-based material of the crystalline plate-like smectite group is added has excellent thixotropic properties and can achieve both storability and applicability.
[0070]
First, the exchangeable cation of E in the formula (3) was sodium, and Z was evaluated by sodium-fluorine type hectorite in which fluorine (F) was not hydroxyl group (OH). Slurry preparation was performed on the same conditions as the experiment shown in Table 1, and the evaluation of storability and applicability was performed on the same basis as the experiment shown in Table 1. The results are summarized in Table 2.
[0071]
[Table 2]

[0072]
When using Na-F type hectorite, which has different static viscosity and equilibrium viscosity and exhibits thixotropy as a thickener, storage and coating properties are the same as when using Na-OH type hectorite as a thickener. It was found that an alumina water slurry capable of satisfying both conditions can be realized.
[0073]
In particular, the storage and coating properties were good under the conditions of a static viscosity of 500 mPa · s or more and an equilibrium viscosity of 200 mPa · s or less. At this time, the concentration of the thickener was 0.1% to 10.0%.
[0074]
Furthermore, the present inventors prepared an aqueous solution with a concentration of 1.0% using a series of crystalline platy smectite group clay-based materials shown in Table 3 as a thickener, and then made an alumina water slurry, which was then stored. The applicability was evaluated. Slurry preparation and viscosity measurement were performed under the same conditions as the evaluation experiments summarized in Table 1. As a comparative example, a 1% aqueous solution of cellulose ether having a molecular weight of 100,000 was also prepared and evaluated. The evaluation results are summarized in Table 3.
[0075]
[Table 3]

[0076]
In the water slurry formed by using a clay-based material of the crystalline plate-like smectite group having slurry numbers 1 to 7 having different static viscosity and equilibrium viscosity and exhibiting thixotropy as a thickener, both storage property and coating property can be achieved. I understood that. In particular, the storage and coating properties were good under the conditions of a static viscosity of 500 mPa · s or more and an equilibrium viscosity of 200 mPa · s or less.
[0077]
From the above, it can be confirmed that the water slurry formed by using the clay-based material of the crystalline plate-like smectite group represented by the formula (3) as a thickener can exhibit thixotropy capable of achieving both storage and applicability. It was.
[0078]
Examples of the clay-based material of the crystalline plate-like smectite group that can be applied to the present invention include the following as Z-hydroxyl type. Here {E_1/3 ・ NH₂ Although the O} portion is omitted, sodium or magnesium is generally used as the exchangeable cation for E, and one or a mixture of two or more of these may be applied.
[0079]

In addition, the following is suitable for the present invention as a fluorine type having Z.
[0080]

If the concentration of the thickener exceeds 10% by mass with respect to water, the mirror surface degree of the steel sheet may be affected.
[0081]
The thickener disclosed in the present invention can be used regardless of the type of the annealing separator, but is particularly effective when the main component of the annealing separator is alumina alone, magnesia alone, or a mixture of alumina and magnesia. In particular, although it is suitable for mirror finishing of steel sheets, it tends to cause sedimentation in the slurry, so it has a great effect in preventing sedimentation of alumina or magnesia with a particle size of several μm or more, which has been narrow in conventional use conditions. A slurry that can be easily applied with a roll coater can be formed.
[0082]
【Example】
<Example 1>
Aqueous solution of 1,200 ml of 1.0 mass% aqueous solution of sodium-hydroxyl-type hectorite having thixotropic property and water-soluble cellulose ether (molecular weight = 100,000) which is an organic polymer compound having no thixotropic property, each having a depth of 25 cm Into a cylindrical plastic beaker having a diameter of 14 cm, 450 g of alumina as an annealing separator was put, and the mixture was stirred for 30 minutes with a shear force of 500 rotations / minute using a saw blade type stirrer having a diameter of 4 cm. The shear rate at this time was 11 (1 / second). Next, with a B-type viscometer, No. The viscosity was measured 15 seconds after the stirring was stopped under the condition of 1 rotor and a rotation number of 1.5 times / minute. The viscosity at this time was defined as an equilibrium viscosity. Thereafter, the viscosity was measured under the same conditions 5 minutes after stirring was stopped. The viscosity at this time was defined as a static viscosity. The viscosity was measured at a temperature of 20 ° C.
[0083]
Evaluation of storage property and applicability was performed under the same conditions and criteria as the experiment shown in Table 1. Table 4 summarizes the measurement and evaluation results.
[0084]
[Table 4]

[0085]
Under the conditions of slurry No. 2 using cellulose ether as a thickener as a comparative example, no remarkable precipitation of alumina occurs and storage stability is good, but the slurry viscosity is too high, so that coating unevenness occurs severely. Sex was extremely bad.
[0086]
On the other hand, under the conditions of slurry No. 1 using Na-OH type hectorite as a thickener as an example, there was no precipitation of alumina and storage stability was excellent, coating unevenness was not generated, and coating properties were excellent.
[0087]
In addition, when the water slurry of the slurry number 1 which is an Example was apply | coated to the 0.23 mm-thick steel plate which has been decarburized annealing, and the final annealing was performed, there was no seizure of alumina and secondary recrystallization exhibiting specular gloss I was able to get a finished steel plate.
<Example 2>
Depth of each 1200 ml of 1.0% by weight aqueous solution of sodium / magnesium-hydroxyl type saponite having thixotropic properties and water-soluble cellulose ether (molecular weight = 100,000) which is an organic polymer compound having no thixotropic properties. Into a cylindrical plastic beaker having a diameter of 25 cm and a diameter of 14 cm, 450 g of alumina as an annealing separator was added, and the mixture was stirred for 10 minutes with a shear force of 2500 rpm with a saw blade impeller having a diameter of 4 cm. The shear rate at this time was 52 (1 / second). Next, with a B-type viscometer, No. The viscosity was measured 15 seconds after the stirring was stopped under the condition of 1 rotor and a rotation number of 1.5 times / minute. The viscosity at this time was defined as an equilibrium viscosity. Thereafter, the viscosity was measured under the same conditions 5 minutes after stirring was stopped. The viscosity at this time was defined as a static viscosity. The viscosity was measured at a temperature of 20 ° C. Evaluation of storage property and applicability was performed under the same conditions and criteria as the experiment shown in Table 1. Table 5 summarizes the measurement and evaluation results.
[0088]
[Table 5]

[0089]
Under the conditions of slurry No. 2 using cellulose ether as a thickener, which is a comparative example, no significant precipitation of alumina occurs and storage stability is good, but the slurry viscosity is too high, so that coating unevenness is severely generated. The applicability was extremely poor.
[0090]
On the other hand, under the conditions of slurry No. 1 using Na / Mg—OH type saponite as a thickener as an example, there was no precipitation of alumina and storage stability was excellent, coating unevenness was not generated, and coating properties were excellent.
[0091]
In addition, when the water slurry of the slurry number 1 which is an Example was apply | coated to the 0.23 mm-thick steel plate which has been decarburized annealing, and the final annealing was performed, there was no seizure of alumina and secondary recrystallization exhibiting specular gloss I was able to get a finished steel plate.
<Example 3>
Aqueous solution of 1,200 ml of 1.0% by weight aqueous solution of sodium-fluorine hectorite with thixotropic property and water-soluble cellulose ether (molecular weight = 100,000), which is an organic polymer compound without thixotropic property, is 25 cm in depth. Into a cylindrical plastic beaker having a diameter of 14 cm, 450 g of alumina as an annealing separator was added, and the mixture was stirred for 15 minutes with a shear force of 1500 revolutions / minute using a saw blade type stirrer having a diameter of 4 cm. The shear rate at this time was 31 (1 / second). Next, with a B-type viscometer, No. The viscosity was measured 15 seconds after the stirring was stopped under the condition of 1 rotor and a rotation number of 1.5 times / minute. The viscosity at this time was defined as an equilibrium viscosity. Thereafter, the viscosity was measured under the same conditions 5 minutes after stirring was stopped. The viscosity at this time was defined as a static viscosity. The viscosity was measured at a temperature of 20 ° C. Evaluation of storage property and applicability was performed under the same conditions and criteria as the experiment shown in Table 1. Table 6 summarizes the measurement and evaluation results.
[0092]
[Table 6]

[0093]
Under the conditions of slurry No. 2 using cellulose ether as a thickener, which is a comparative example, no significant precipitation of alumina occurs and storage stability is good, but the slurry viscosity is too high, so that coating unevenness is severely generated. The applicability was extremely poor.
[0094]
On the other hand, under the conditions of slurry No. 1 using Na-F type hectorite as an example as a thickener, there was no precipitation of alumina and storage stability was excellent, coating unevenness was not generated, and coating properties were excellent.
[0095]
In addition, when the water slurry of the slurry number 1 which is an Example was apply | coated to the 0.23 mm-thick steel plate which has been decarburized annealing, and the final annealing was performed, there was no seizure of alumina and secondary recrystallization exhibiting specular gloss I was able to get a finished steel plate.
[0096]
【The invention's effect】
As described above, according to the present invention, as an annealing separator water slurry used for the production of a finish annealed plate for unidirectional electrical steel without an inorganic substance film such as forsterite, precipitation of the annealing separator in tanks and pipes. Since it is possible to achieve both prevention and coating property with a roll coater, that is, storage property and coating property of the annealing separator slurry, the industrial effect is great.

Claims

The annealing separator water slurry was applied to a decarburization annealed sheet for grain-oriented electrical steel sheet, when subjected to a finish annealing, the annealing separator water slurry have a thixotropic, the viscosity of the annealing separator water slurry (1 ) And (2) are satisfied, a thickener composed of an inorganic substance is added, and the thickener of the inorganic substance is a crystalline plate smectite group represented by the chemical composition formula (3) A method for producing a finish-annealed sheet for a unidirectional electrical steel sheet having no forsterite film on the steel sheet, characterized by being a clay-based material .
(1) Formula: Equilibrium viscosity ≦ 200 mPa · s
(2) Formula: Static viscosity ≧ 500 mPa · s
However, the equilibrium viscosity is stirred for 10 minutes or more with a shearing force of 10 (1 / second) or higher, and the viscosity measured using a B-type viscometer after 15 seconds of stirring is stopped, and the static viscosity is also 5 minutes after stirring. Viscosity measured later.
(3) Formula: {E · nH ₂ O} (X) [Y] O ₁₀ (Z) ₂
However, {} represents an interlayer substance, E represents a monovalent or divalent exchangeable cation, nH ₂ O represents interlayer water, and X represents Al, Mg, Fe, Cr, Zn, or Li. One or two or more metal ions selected from the above form an octahedral ion in the structure, and Y is one or two metal ions selected from Si and Al in the structure. Z is a hydroxyl group or a halogen.

The concentration of the inorganic thickener is 10% by mass or less with respect to water, and manufacturing a finish-annealed sheet for unidirectional electrical steel sheets without a forsterite film on a steel sheet according to claim 1 Method.

The annealing separator for a unidirectional electrical steel sheet having no forsterite film on a steel sheet according to claim 1 or 2 , wherein the annealing separator is alumina alone, magnesia alone, or a mixture of alumina and magnesia. Production method.

To obtain a grain-oriented electrical steel finishing annealed sheet with no forsterite film on the steel sheet, a annealing separator water slurry to be applied to decarburization annealed sheet before final annealing, have a thixotropic, annealing separator The thixotropic viscosity of the agent water slurry satisfies both formulas (1) and (2), a thickener made of an inorganic substance is added, and the thickener is represented by the chemical composition formula of formula (3). An annealing separator water slurry excellent in storability and applicability, characterized by being a clay-based material of the crystalline plate-like smectite group .
(1) Formula: Equilibrium viscosity ≦ 200 mPa · s
(2) Formula: Static viscosity ≧ 500 mPa · s
However, the equilibrium viscosity is stirred for 10 minutes or more with a shearing force of 10 (1 / second) or higher, and the viscosity measured using a B-type viscometer after 15 seconds of stirring is stopped, and the static viscosity is also 5 minutes after stirring. Viscosity measured later.
(3) Formula: {E · nH ₂ O} (X) [Y] O ₁₀ (Z) ₂
However, {} represents an interlayer substance, E represents a monovalent or divalent exchangeable cation, nH ₂ O represents interlayer water, and X represents Al, Mg, Fe, Cr, Zn, or Li. One or two or more metal ions selected from the above form an octahedral ion in the structure, and Y is one or two metal ions selected from Si and Al in the structure. Z is a hydroxyl group or a halogen.

The concentration of the thickener is 10% by mass or less with respect to water, and the annealing separator water slurry having excellent storability and applicability according to claim 4.

6. An annealing separator water slurry excellent in storability and applicability according to claim 4 or 5 , wherein the annealing separator is alumina alone, magnesia alone, or a mixture of alumina and magnesia.