JP4232407B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

【００２６】
表１に示すように、化学気相蒸着に先立ち、鋼中炭素量を20ppm以上とした鋼板は、最小曲げ径10mmφ以下の極めて優れた密着性を示した。とりわけ、鋼中炭素量を40ppm以上とした鋼板では、測定限界である５mmφ以下という、さらに優れた密着性が得られた。
【００２７】
表１に示した結果は、鋼中に予め窒素を含有させ、その後化学気相蒸着法によりTiＮ膜を形成した場合、そして鋼中に予め炭素および窒素の少なくともいずれか一方を含有させ、その後化学気相蒸着法によりTiＣＮ膜を形成した場合、でも同様であった。
以上より、通常は炭素で10ppm以下および窒素で５ppm以下の組成を有する、最終仕上焼鈍後の方向性電磁鋼板に対し、20ppm以上の炭素または／および窒素を鋼中に含有させることによって、その後の化学気相蒸着膜の密着性を飛躍的に向上できることがわかった。
【００２８】
さらに、適正な厚みのTiＣ膜の形成に必要な炭素量を予め鋼中に確保しておけば、化学気相蒸着中に炭素源であるＣＨ_４ガスを使用しなくても、密着性の良好なTiＣ膜を形成できることがわかった。これは、上述した熱壁型反応炉を用いて化学気相蒸着処理を行う場合に問題となる、炉の内壁への析出抑止にも効果的であり、また原料ガスからＣＨ_４を除いた混合ガス組成で蒸着を行えば、炭素源を持つ鋼板表面でのみTiＣの析出反応を起こすことができ、TiＣの収率向上の点でも極めて有効である。かような効果は、Ti ＮおよびTi ＣＮの被膜形成においても同様である。
【００２９】
また、鋼中炭素量が多い素材ほど短時間で成膜が終了する傾向が見られた。この理由として、一つは炭素原料の供給経路が二つとなることである。しかしもう一つ、通常は炭素源となるＣＨ_４の分解がTiＣ膜形成の反応律速となっているのに対し、この発明の場合には鋼中より原子状の炭素が直接供給されることが、成膜速度の向上に寄与したのではないかと考えられる。かような効果は、Ti ＮおよびTi ＣＮの被膜形成においても同様である。
【００３０】
ここで、化学気相蒸着法としては、TiC1₄等の金属塩化物ガスと、もう一方の原料ガスとして、Ti ＮならばN₂， NH₃, (CH₃)₃N, (CH₃)₂NHガスなど、Ti ＣならばCH₄, CO, C₂H₄, C₃H₆, C₃H₈, C₂H₆, i-C₅H₁₂などを混合した雰囲気中にて、鋼板を加熱することにより、セラミックスの被膜を得る。もちろん、両者を混合してTi ＣＮとしても何ら問題はないし、酸化物や硼化物等も公知の方法で実施可能である。その他、バランスガスとしてArガスなどが使用される。
【００３１】
また、金属源として、有機金属ガスを用いる、いわゆるMO−CVD法やプラズマやレーザー、光誘起などを併用し、より低温化を指向したCVD手法も近年盛んになりつつあるが、この発明の場合、後続の熱処理温度にもよるが、試料あるいは化学蒸着槽全体を加熱する熱CVD法がより適していると思われる。ただし、蒸着速度向上等を目的として、上記手法を併用するのは、この発明の範囲内であれば、何ら差し支えない。
【００３２】
かくして得られる被膜物質は、Ti Ｎ、Ti ＣまたはTi ＣＮであり、その２種以上を積層しても構わず、鋼中の炭素か窒素の少なくともいずれかの鋼中含有量が20ppm以上を満たしていれば、TiCN 膜の密着性にも顕著な効果が見られた。
【００３３】
被膜の厚みについては、0.01μｍ以上５μｍ以下の範囲が適合し、0.01μｍに満たない場合は、十分な張力付与効果や被膜密着性が得られず、５μｍを越えると膜自身の密着性や電磁鋼板の占有率において不利となる。
【００３４】
この発明に従って化学蒸着処理を適用する仕上焼鈍後の鋼板表面としては、単にフォルステライト被膜の形成を抑制した、もしくはフォルステライト被膜を除去しただけの地鉄面でも有効ではあるが、さらに表面に平滑化処理を施した方が、鉄損値の低下により効果的である。例えば、酸洗、サーマルエッチングや化学研磨等により表面粗さを極力小さくし、鏡面状態に仕上げた表面やハロゲン化物水溶液中での電解による結晶方位強調処理で得られるグレイニング様面等が挙げられる。
【００３５】
また、打ち抜き性等の加工性を重視して最終仕上焼鈍に使用する焼純分離剤の主成分を替えたり、添加物を加えることにより、最終仕上焼鈍被膜の形成を抑止した、方向性電磁鋼板も好適である。
【００３６】
化学気相蒸着前に鋼中の炭素や窒素量を高める方法は、多々あるため、適宜選択して適用すればよい。例えば、炭素であれば、前述のように一次再結晶焼鈍時に脱炭反応を抑制する雰囲気中で行い、鋼中に炭素を残留させるのが最も簡便であるが、COガス等を利用したガス浸炭処理を行ったり、炭化物を密着させたり、その粉末を塗布する固体浸炭処理を行うことも可能である。窒素についても、AlＮやBNなどの窒化物をインヒビターとして使用している場合には、最終仕上焼鈍時に行われるＨ_２による純化処理を行わずに、窒素源を残留させたり、ＮＨ_３分解を利用したり、イオン窒化やプラズマ窒化法を利用したりすることができる。いずれにしても、化学気相蒸着前に20ppm以上の炭素または／および窒素を含有させることが肝要である。
【００３７】
なお、化学気相蒸着後に鋼中に残留する炭素および窒素の上限量は、Ti ＣまたはTi Ｎの析出による時効劣化を抑制するために、それぞれ30mass ppmおよび100mass ppmとすることが好ましい。
【００３８】
さらに、化学気相蒸着したTi Ｎ、Ti ＣまたはTi ＣＮの被膜上に被成する絶縁被膜としては、方向性電磁鋼板に使用される無機質コートが利用可能である。特に、張力付与効果を有するコーティングは、超低鉄損化を達成するために表面を平滑化した方向性電磁鋼板と組合せると、極めて有効である。張力付与型コーティングとしては、熱膨張係数を低下させるシリカを含むコーティングが推奨され、従来、フォルステライト被膜を有する方向性電磁鋼板に用いられている、リン酸塩−コロイダルシリカークロム酸系のコーティング等が、その効果およびコスト、均一処理性などの点から、適している。また、絶縁被膜の厚みとしては、張力付与効果や占積率、被膜密着性等の点から、0.3μｍ以上10μｍ以下の範囲が好ましい。
【００３９】
また、張力コーティングとしては、上記以外にも、特開平６-65754号公報、特開平6-65755号公報および特開平6-299366号公報などで提案されている、ホウ酸−アルミナ等の酸化物系被膜を適用することも可能である。
【００４０】
以下、この発明の方法について、まず電磁鋼板の成分組成から順に説明する。
この発明で使用される鋼板の成分としては、Siを1.5〜7.0mass％含有することが望ましい。すなわち、Siは製品の電気抵抗を高め鉄損を低減するのに有効な成分であるが、Siは7.0mass％を超えると硬度が高くなり、製造や加工が困難になりがちである。一方、1.5％未満であると、最終仕上げ焼鈍中に変態を生じて安定した2次再結晶組織が得られない。
【００４１】
また、インヒビター元素として、Alを初期鋼中に0.006mass％以上含有することにより、結晶配向性をより一層向上することができる。上限は0.06mass％程度であり、これを越えると再び結晶配向の劣化が生じる。
【００４２】
さらに、鋼中には、上記の元素の他に、公知の方向性電磁鋼板の製造に適するインヒビター成分として、Ｂ，Bi，Sb，Mo，Te，Sn，Ｐ，Ge，As，Nb，Cr，Ti，Cu，Pb，ZnおよびInなどが知られていて、これらの元素を単独、または複合で含有させることができる。また、インヒビターを使用しない方法による方向性電磁鋼板に対しても、この発明の適用が可能である。
【００４３】
次に、この発明の電磁鋼板の製造方法について、詳しく説明する。
上記した所定成分に調整された鋼スラブは、通常スラブ加熱に供された後、熱間圧延により熱延コイルとされるが、この鋼スラブの加熱温度については1300℃以上の高温度とする場合と、1250℃以下の低温度とする場合のいずれでも良い。また、近年、スラブ加熱を行わず連続鋳造後、直接熱間圧延を行う方法が開発されているが、この方法で熱間圧延される場合にも適用できる。
【００４４】
熱間圧延後の鋼板は必要に応じて熱延板焼鈍を施し、１回の冷間圧廷もしくは中間焼鈍を挟む複数回の圧延によって最終冷間圧延板とされる。これらの圧延については、動的時効を狙ったいわゆる温間圧延や、静的時効を狙ったパス間時効を施したものであっても良い。
【００４５】
最終冷間圧延後の鋼板は、脱炭焼鈍を兼ねる1次再結晶焼鈍に供され、最終仕上焼純により２次再結晶処理をされ、方向性電磁鋼板を得る。通常、１次再結晶焼鈍後に焼鈍分離剤を塗布し、最終仕上焼純の際にフォルステライト被膜を形成させるが、このフォルステライト被膜を酸洗や研磨等により除去するか、もしくは焼鈍分離剤の組成を調整して、鋼板表面上のフォルステライト被膜の生成を抑制し、実質的に金属外観を有する状態とする。
【００４６】
このようにして得られた鋼板に、更なる鉄損低減を目的として、レーザーあるいはプラズマ炎等を照射して磁区の細分化を行うことは、絶縁コーティングの密着性にはなんら問題ない。また、この発明の方向性電磁鋼板の製造工程の任意の段階において、磁区細分化のために、鋼板表面にエッチングや歯形ロールで一定間隔の溝を形成することも、一層の鉄損低減をはかる手段として有効である。
【００４７】
【実施例】
実施例１
Ｃ：0.06mass％、Si：3.2mass％、Mn：0.07mass％およびSe：0.04mass％を含有する、最終板厚0.23mmに圧延された冷延コイルに、磁区細分化のために５mm間隔で、圧延方向に延びる複数の溝をエッチングにて形成してから、脱炭を兼ねた一次再結晶焼鈍を施した後、MgOを主成分とし塩化鉛を含む焼純分離剤を塗布し、フォルステライト被膜のない平滑な表面を有する、最終仕上焼鈍済の鋼板を作製した。得られた鋼板の窒素含有量は、測定限界（５ppm）以下であった。この鋼板に対して、550℃、50torrの窒素および水素の混合雰囲気下でイオン窒化させ、種々の鋼中窒素含有量を有する試料とした。なお、一部の試料については、増窒化処理を実施しなかった。
【００４８】
その後、TiCl_４、Ｈ_２およびＮ_２の混合ガスからなる雰囲気中にて、TiNを片面当たり1.0μm厚で形成した。TiCl_４は、気化器で150℃に加熱することによってガス化させ、Ｈ_２およびＮ_２ガスと種々の混合比率でミキシングし、それぞれの分圧を調整した。次いで、TiN膜の被成後、第一リン酸Mgに重クロム酸Kを15重量部加えた水溶液に、30mass％コロイダルシリカを30重量部混合したものを、ロールコーターで塗布し、800℃で1分間焼き付け、絶縁被膜を形成させた。さらに、歪取焼鈍として850℃で3時間の焼鈍を行った。
【００４９】
かくして得られた鋼板について、850℃で３時間の歪取焼鈍後の被膜密着性を最小剥離径で評価した。その評価結果を、TiN化学気相蒸着前の鋼中窒素量および被膜外外観と併せて、表２に示す。試料４〜６は、化学気相蒸着前の鋼中窒素含有量がこの発明の要件を満足するものであり、美麗で優れた外観と極めて優れた被膜密着性を示している。これらに対し、化学気相蒸着前にイオン窒化による増窒化処理を行わなかった試料１や、窒素含有量が十分でない試料２および３は、歪取焼鈍後の被膜密着性が劣り、もともと金色に近かったTiN膜も茶褐色に変化した。
【００５０】
【表２】

【００５１】
実施例２
Ｃ：0.07mass％、Si：3.3mass％、酸化溶性Al：0.026mass％、Ｎ：0.008mass％およびSb：0.05mass％を含有する、最終板厚0.23mmに圧延された冷延板に、一次再結晶焼鈍を施すに当たり、一次再結晶焼鈍における雰囲気酸化性を変化させ、種々の炭素量を含有させた素材を作製した。次いで、酸洗によりSiO_２被膜を主体とする酸化膜を除去した後、焼鈍分離剤としてアルミナを用いることにより、フォルステライト被膜のない平滑な表面を有する最終仕上焼鈍板を得た。得られた鋼板に対し、TiCl_４、Ｈ_２およびCH_４の混合ガスからなる雰囲気中にて、TiCを片面当たり0.5μm厚で形成した。Ｈ_２ガスおよびCH_４ガスは種々の混合比とし、TiCl_４濃度はＨ_２ガスをキャリアガスとしTiCl_４液中をバブリングさせることで調整した。
【００５２】
次いで、硼酸とベーマイトを主成分とする絶縁コーティング液（酸化物換算モル比Ｂ_２Ｏ_３／Al_２Ｏ_３＝0.5）をロールコーターにて塗布し、800℃で120秒間焼き付けた。さらに、張力付与のために、900℃で１時間の焼鈍を行った。その後、歪取焼鈍として、850℃で３時間の焼鈍を行った。
【００５３】
かくして得られた鋼板について、850℃で３時間の歪取焼鈍後の被膜密着性を最小剥離径で評価した。その評価結果を、TiC化学気相蒸着前の鋼中窒素量および被膜外外観と併せて、表３に示す。試料４〜６は、化学気相蒸着前の鋼中炭素含有量がこの発明の要件を満足するものであり、美麗な外観と極めて優れた被膜密着性が得られた。これらに対し、化学気相蒸着前の炭素含有量が十分でない試料１〜３は、歪取焼鈍後の被膜密着性が劣り、被膜外観も黒変化が著しく均一な被膜外観は得られなかった。
【００５４】
【表３】

【００５５】
実施例３
実施例２と同様に作製した最終仕上焼鈍板に対し、TiCl_４、CH_４、Ｎ_２、Ｈ_２およびArの混合ガスからなる雰囲気中にて、TiCNを片面当たり0.7μm厚で形成した。ＣとＮのモル比は１：１ではなく多少変動したが、密着性、磁気特性に対する影響は特にみとめられなかった。
ついで、第一リン酸Alに硝酸マンガンとコロイダルシリカを添加・混合したクロムフリーコートを塗布し、850℃で焼き付けた。その後、820℃で３時間の歪取焼鈍を行い、被膜密着性を評価した。その評価結果を表４に示す。試料４〜６はこの発明に適合する例であり、美麗な外観と極めて優れた被膜密着性を示した。これらに対し、化学気相蒸着前の炭素含有量が十分でない試料１〜３は、歪取焼鈍後の被膜密着性に劣り、白味ががった金色のTiCNは茶褐色に変化した。
【００５６】
【表４】

【００５７】
【発明の効果】
この発明により、フォルステライト被膜のない平滑な方向性電磁鋼板の表面に、張力付与効果が大きく、かつ密着性に極めて優れる被膜を化学蒸着処理にて被成することができるため、被膜密着性に優れる極めて鉄損値の低い方向性電磁鋼板の製造が可能となる。[0001]
BACKGROUND OF THE INVENTION
[Industrial application fields]
The present invention relates to a method of manufacturing a grain-oriented electrical steel sheet, and particularly intends to improve the iron loss characteristics by forming a coating film having a very large tensioning effect on the surface of the steel sheet.
[0002]
[Prior art]
There are two types of electrical steel sheets: non-oriented electrical steel sheets and directional electrical steel sheets. Non-oriented electrical steel sheets are mainly used for iron core materials such as rotating machines, and directional electrical steel sheets are used mainly for transformers and other electrical equipment. In order to reduce energy loss, both are used as iron core materials, and low iron loss materials are required.
[0003]
To reduce the iron loss of grain-oriented electrical steel sheets, there are methods such as reducing the plate thickness, increasing the Si content, or increasing the orientation of the crystal orientation, but in addition, it is effective to give tension to the steel sheet It is. As a method for imparting tension to a steel plate, it is common to provide a coating made of a material having a smaller thermal expansion coefficient than that of the steel plate. That is, in the final finish annealing process, which finally serves as secondary recrystallization that aligns the crystal orientation and purification of the steel sheet, the forsterite reacts with the oxide on the surface of the steel sheet and the quenching separation agent applied to the steel sheet surface. A film having a main component is formed. This film has a large tension applied to the steel sheet, and is effective in reducing iron loss. Furthermore, in order to increase the tension effect, it is generally performed to produce a product by applying a low thermal expansion coating on the forsterite film.
[0004]
However, in recent years, a method for magnetically smoothing the surface of a steel sheet has been developed, and after the forsterite film has been intentionally suppressed in the finish tempering process or the formed forsterite film has been removed, the surface is removed. It has become clear that a smooth finish is effective in reducing iron loss. For example, Japanese Examined Patent Publication No. 52-24499 discloses a method of removing surface products by pickling after finish annealing and then finishing to a mirror state by chemical polishing or electrolytic polishing. JP-A-5-43943 discloses that after removing the forsterite film, the H₂A method for thermal etching is disclosed. The reason why the iron loss is reduced by such a surface treatment is that pinning sites that hinder the domain wall movement in the vicinity of the steel sheet surface are reduced in the magnetization process.
[0005]
Note that a magnetically smooth surface that reduces hysteresis loss is generally expressed by Ra (arithmetic mean roughness), not only by so-called surface roughness, but described in Japanese Patent Publication No. 4-72920. There are also known those obtained by crystal orientation emphasis treatment in which electrolysis is performed in a halogenated aqueous solution after removing the surface product.
[0006]
In addition, since an insulating coating is required on the surface of the electrical steel sheet, an insulating coating is usually applied, and is currently applied to a grain-oriented electrical steel sheet having a forsterite coating. Insulating coating is formed by applying and baking a treatment liquid mainly composed of Al or alkaline earth metal phosphate and colloidal silica, chromic anhydride or chromate on a steel plate. There are many things. The tension-added insulation coating forms an inorganic coating typified by colloidal silica, which has a smaller coefficient of thermal expansion than that of a steel plate, at a high temperature. It is given to the steel plate. The insulating coating formed by this method has a great effect of imparting tension to the steel sheet and is effective in reducing iron loss. For example, the forming method is shown in Japanese Patent Publication No. 53-28375 or Japanese Patent Publication No. 56-52117.
[0007]
However, the higher the tension applied to the steel sheet, the more the film will peel off if the adhesion to the substrate is not strong.Therefore, the forsterite-type coating has a forsterite-type final finish annealed film on the steel sheet surface. However, the film could not be deposited when there was no forsterite film after final finish annealing such as surface smoothing such as mirror finishing. For this reason, it has been difficult to achieve both a technique for magnetically smoothing the surface and reducing iron loss and a technique for reducing iron loss using a tension-imparting coating.
[0008]
Conventionally, several methods have been proposed as a method for depositing a tension-applying coating on a surface without a forsterite coating, or even on a smooth surface that has been adjusted. For example, JP-B 52-24499 discloses after metal plating, and JP-A-6-184762 discloses SiO.₂A method of applying and baking a tensioned coating solution after each thin film is formed is shown. Japanese Patent Publication No. 56-4150 discloses a method of forming a ceramic thin film by vapor deposition, sputtering, or thermal spraying, and Japanese Patent Publication No. 63-54767 discloses a nitride or carbide ceramic film by ion plating or Each method of forming by ion plantation is shown. Furthermore, Japanese Patent Application Laid-Open No. 2-243770 discloses a method of directly forming a high-tension imparting ceramic film on the surface of a steel sheet by a so-called sol-gel method.
[0009]
These methods have been developed as methods for applying tension to a steel plate having a smoothed surface, but have some problems and have not yet been put into practical use.
That is, in the method of coating a thin metal plating as a base and the coating treatment thereon, due to the smoothness of the uniform plating surface, the adhesion of the film is not sufficient, and SiO₂The method of forming a thin film was inferior in the effect of imparting tension, and the effect of improving iron loss was not sufficient. In addition, the ceramic coating made of nitride, carbide, etc., or a combination of both has a much lower thermal expansion coefficient than that of the base iron, so the tension effect due to the difference in the thermal expansion coefficient is great, and therefore during bending. There was a problem in the adhesion between the steel and the coating.
[0010]
Furthermore, the formation of ceramic coatings by vapor deposition, sputtering, thermal spraying, ion plating, and ion plantation is expensive, and it is difficult to ensure uniformity when large areas are processed in large quantities. Although it is possible to form a film by coating and baking, it is extremely difficult to form a healthy film with a thickness of 0.5 μm or more, so it does not bring about a large tension imparting effect, and the expected iron loss improving effect It was not obtained.
[0011]
Japanese Patent Laid-Open No. 63-57781 discloses a method of forming an insulating film mainly composed of chromic acid or phosphoric acid after providing a silicate-based film. Although the adhesion is improved, neither the silicate film nor the chromic acid-phosphoric acid film has the effect of imparting tension to the steel sheet, and the effect of reducing the iron loss value due to the film tension cannot be obtained.
[0012]
On the other hand, the chemical vapor deposition method disclosed in Japanese Patent Laid-Open No. 61-201732 is a powerful technique capable of forming a uniform ceramic film over a large area without requiring a vacuum chamber with many restrictions. It is a technique. That is, because of the high temperature reaction, the adhesion between the ceramics and the steel sheet is also good, and compared with the physical vapor deposition such as sputtering, thermal spraying, ion plating, ion plantation, etc., the impact of the product on the steel sheet surface is weak. It is possible to deposit a ceramic film without compromising the very low hysteresis loss achieved with a smoothed surface. In particular, it is suitable for depositing a nitride or carbide having a high Young's modulus and a small thermal expansion coefficient on the steel sheet surface.
[0013]
[Problems to be solved by the invention]
However, after the ceramic film is formed, when the tension-applying type insulation coating is applied or the strain relief annealing is performed for the purpose of removing the shear strain, the coating may change in quality such as discoloration or insufficient adhesion. The problem of peeling off still occurred. This is probably due to the dissociation due to the difference in thermal expansion coefficient between the steel sheet and the ceramic film, but the difference in thermal expansion coefficient is an indispensable element in order to obtain a strong tensioning effect. There is a need to improve sex.
[0014]
Further, in the chemical vapor deposition method, in order to promote a chemical reaction which is a thermal activation-determining rate, it is usual to raise the temperature, use plasma together, or excite the reaction gas with a laser, light or the like. In the thermal chemical vapor deposition method, a so-called cold wall type reactor that heats only the substrate and a so-called external heating type reactor that heats the entire reactor and heats the steel sheet are used. The cold wall type is advantageous when the substrate is small, but it is difficult to heat the entire substrate to a uniform temperature, and the temperature-sensitive thermochemical vapor reaction method has a problem that the coating thickness varies depending on the site. Arise. On the other hand, in the case of the external heating type, although the uniformity of the substrate temperature is excellent, the problem that the product is simultaneously deposited on the reaction furnace wall cannot be avoided.
[0015]
Therefore, the present invention provides an excellent film even when a film is formed by chemical vapor deposition and further subjected to heat treatment such as baking of the tension-imparting type coating or strain relief annealing on the film. It aims at proposing about the manufacturing method of a low iron loss directionality electrical steel sheet in which adhesiveness is maintained in the said film.
[0016]
[Means for Solving the Problems]
The inventors have intensively studied about means for improving the adhesion of a film formed by chemical vapor deposition, and by incorporating elements, which are basic components in the film, into the steel in advance, on the steel sheet surface. As a result, the present invention was completed.
[0017]
  That is, the gist configuration of the present invention is as follows.
(1)FOf olsterite coatingSuppressed formation or removed forsterite filmOn the surface of the grain-oriented electrical steel sheet after final finish annealing,Heat that heats the entire steel plate or chemical vapor deposition layerBy chemical vapor depositionTiNWhen forming a coating, the steel sheet contains 20 ppm or more of nitrogen.In the thermal chemical vapor deposition process, the TiN film is formed by reacting nitrogen in the steel sheet with Ti in the raw material gas.It is characterized byWhoA method for producing a grain-oriented electrical steel sheet.
[0018]
(2)FOf olsterite coatingSuppressed formation or removed forsterite filmOn the surface of the grain-oriented electrical steel sheet after final finish annealing,Heat that heats the entire steel plate or chemical vapor deposition layerBy chemical vapor depositionTiCWhen forming a coating, the steel sheet contains 20 ppm or more of carbon.In the thermal chemical vapor deposition process, the TiC film is formed by reacting nitrogen in the steel sheet with Ti in the raw material gas.It is characterized byWhoA method for producing a grain-oriented electrical steel sheet.
[0019]
(3)FOf olsterite coatingSuppressed formation or removed forsterite filmOn the surface of the grain-oriented electrical steel sheet after final finish annealing,Heat that heats the entire steel plate or chemical vapor deposition layerBy chemical vapor depositionTiCNWhen forming a film, the steel sheet contains at least one of carbon and nitrogen at 20 ppm or more.In the thermal chemical vapor deposition process, the TiCN film is formed by reacting nitrogen in the steel sheet with Ti in the source gas.It is characterized byWhoA method for producing a grain-oriented electrical steel sheet.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the experimental results leading to the present invention will be described in detail.
C: 0.07 mass%, Si: 3.3 mass%, Mn: 0.07 mass%, S: 0.025 mass%, acid-soluble Al: 0.026 mass%, N: 0.008 mass% and Sn: 0.1 mass%, including 2.0 mm The hot-rolled steel sheet was annealed at 1120 ° C. for 2 minutes and then cold-rolled to a final thickness of 0.23 mm. This cold-rolled sheet is mixed with nitrogen and hydrogen in an atmosphere with an oxidizing property (partial pressure ratio PH of water vapor and hydrogen).₂O / PH₂The degree of oxidation expressed by the following formula was varied in various ways, annealed at a temperature of 850 ° C. for 90 seconds, and subjected to primary recrystallization. The carbon concentrations in the steel after annealing were 5, 10, 20, 40, 100, 200, 400 and 600 ppm, respectively.
[0021]
Subsequently, after applying an annealing separator mainly composed of alumina as a water slurry to the surface of the steel sheet, the final finish annealing is performed up to 1200 ° C.₂: 15vol% + H₂: Performed at 85 vol%, H at 1200 ° C₂: Switched to 100 vol% and annealed for 20 hours. In the obtained steel sheet, a good mirror surface was obtained with a material whose carbon content in the steel after primary recrystallization was 200 to 600 ppm.
[0022]
This is presumed to be due to the low oxidizability and insufficient oxide film formed on the surface of the steel sheet. An oxide film was formed on the later sample surface. These samples were subjected to chemical polishing with hydrofluoric acid-hydrogen peroxide to give a mirror finish.
[0023]
Then TiCl at 1000 ° C_FourGas, H₂Gas, CH₄TiC was formed to a thickness of 0.5 μm by chemical vapor deposition in a mixed gas atmosphere. Subsequently, the coating liquid which has phosphoric acid and colloidal silica as a main component was apply | coated, and the insulating film was formed at 850 degreeC. After that, 100vol% N₂Strain relief annealing was performed in gas at 800 ° C. for 3 hours.
[0024]
The material after this strain relief annealing was subjected to a bending adhesion test to evaluate the adhesion of the film. That is, the sample was pressed against a round bar to bend, and the minimum diameter at which the film did not peel was evaluated as an index. The evaluation results are shown in Table 1 together with the amount of carbon in the steel before chemical vapor deposition of TiC.
[0025]
[Table 1]

[0026]
As shown in Table 1, prior to chemical vapor deposition, a steel sheet having a carbon content in the steel of 20 ppm or more exhibited extremely excellent adhesion with a minimum bending diameter of 10 mmφ or less. In particular, a steel sheet having a carbon content in the steel of 40 ppm or more obtained a further excellent adhesion of 5 mmφ or less, which is the measurement limit.
[0027]
The results shown in Table 1 indicate that when steel is preliminarily containing nitrogen and then a TiN film is formed by chemical vapor deposition, and at least one of carbon and nitrogen is preliminarily contained in the steel, and then the chemical Even when the TiCN film was formed by vapor deposition, the same was true.
From the above, by adding 20 ppm or more of carbon and / or nitrogen to the grain-oriented electrical steel sheet after final finish annealing, which usually has a composition of 10 ppm or less of carbon and 5 ppm or less of nitrogen, It was found that the adhesion of chemical vapor deposition films can be dramatically improved.
[0028]
  Furthermore, if the amount of carbon necessary for forming a TiC film having an appropriate thickness is secured in the steel in advance, the carbon source CH₄It was found that a TiC film having good adhesion can be formed without using a gas. This is effective in suppressing precipitation on the inner wall of the furnace, which is a problem when performing the chemical vapor deposition process using the hot wall type reactor described above.₄If the vapor deposition is performed with the mixed gas composition excluding, the TiC precipitation reaction can be caused only on the surface of the steel plate having a carbon source, which is extremely effective in improving the yield of TiC. Such an effectTi NandTi CNThe same applies to the formation of the film.
[0029]
  Moreover, the tendency for the film-forming to be completed in a short time was seen as the material with more carbon in steel. One reason for this is that there are two supply paths for carbon raw materials. But one more thing, usually CH as a carbon source₄In the case of this invention, the atomic carbon is directly supplied from the steel, which may have contributed to the improvement of the film formation rate. Conceivable. Such an effectTi NandTi CNThe same applies to the formation of the film.
[0030]
  Here, as the chemical vapor deposition method, TiC1_FourAs a metal chloride gas such asTi NThen N₂, NH_Three, (CH_Three)_ThreeN, (CH_Three)₂NH gas, etc.Ti CThen CH_Four, CO, C₂H_Four, C_ThreeH₆, C_ThreeH₈, C₂H₆, I c_FiveH₁₂A ceramic film is obtained by heating the steel sheet in an atmosphere in which the above are mixed. Of course, bothTi CNHowever, there is no problem, and oxides, borides and the like can be implemented by a known method. In addition, Ar gas or the like is used as a balance gas.
[0031]
In addition, the so-called MO-CVD method that uses an organometallic gas as a metal source, combined with plasma, laser, photo induction, etc., and CVD methods aimed at lowering temperatures are becoming popular recently. Depending on the temperature of the subsequent heat treatment, the thermal CVD method that heats the sample or the entire chemical vapor deposition tank seems to be more suitable. However, any combination of the above methods for the purpose of improving the deposition rate is acceptable as long as it is within the scope of the present invention.
[0032]
  The coating material thus obtained isTi N,Ti COrTi CNTwo or more of them may be laminated, and if the content of at least one of carbon and nitrogen in the steel satisfies 20 ppm or more, TiCN filmA remarkable effect was also seen in the adhesion of the film.
[0033]
As for the thickness of the film, the range of 0.01 μm or more and 5 μm or less is suitable, and if it is less than 0.01 μm, sufficient tension imparting effect and film adhesion cannot be obtained, and if it exceeds 5 μm, the adhesion of the film itself or electromagnetic This is disadvantageous in terms of steel sheet occupancy.
[0034]
  The steel plate surface after finish annealing to which the chemical vapor deposition treatment is applied according to the present invention is effective even on a steel plate surface in which the formation of a forsterite film is simply suppressed or the forsterite film is removed, but the surface is smoother. It is more effective to reduce the iron loss value. For example, the surface roughness is made as small as possible by pickling, thermal etching, chemical polishing, etc., and the surface is finished in a mirror state or the graining-like surface obtained by the crystal orientation enhancement treatment by electrolysis in an aqueous halide solution. .
[0035]
In addition, the grain-oriented electrical steel sheet that suppresses the formation of the final finish annealed film by changing the main component of the sinter separation agent used in the final finish annealing with emphasis on workability such as punchability and adding additives. Is also suitable.
[0036]
Since there are many methods for increasing the amount of carbon and nitrogen in steel before chemical vapor deposition, they may be selected and applied as appropriate. For example, in the case of carbon, it is most convenient to carry out in an atmosphere that suppresses the decarburization reaction during primary recrystallization annealing as described above, and to leave carbon in the steel, but gas carburization using CO gas or the like It is also possible to perform a solid carburizing process in which a treatment is performed, a carbide is adhered, or the powder is applied. As for nitrogen, when nitrides such as AlN and BN are used as inhibitors, H is performed during the final finish annealing.₂Without purifying with nitrogen, nitrogen source remains or NH₃Decomposition can be used, or ion nitriding or plasma nitriding can be used. In any case, it is important to contain 20 ppm or more of carbon and / or nitrogen before chemical vapor deposition.
[0037]
  The upper limit of carbon and nitrogen remaining in the steel after chemical vapor deposition isTi COrTi NIn order to suppress the aging deterioration due to precipitation, it is preferable to set to 30 mass ppm and 100 mass ppm, respectively.
[0038]
  In addition, chemical vapor depositionTi N,Ti COrTi CNAs the insulating coating formed on the coating, an inorganic coating used for grain-oriented electrical steel sheets can be used. In particular, a coating having a tension imparting effect is extremely effective when combined with a grain-oriented electrical steel sheet having a smooth surface in order to achieve ultra-low iron loss. As the tension-imparting coating, a coating containing silica that lowers the coefficient of thermal expansion is recommended, and a phosphate-colloidal silica-chromic acid type coating conventionally used for grain oriented electrical steel sheets having a forsterite film Are suitable from the viewpoints of the effect and cost, uniform processability, and the like. In addition, the thickness of the insulating coating is preferably in the range of 0.3 μm or more and 10 μm or less from the viewpoint of tension application effect, space factor, coating adhesion, and the like.
[0039]
In addition to the above, as the tension coating, oxides such as boric acid-alumina proposed in JP-A-6-65754, JP-A-6-65755, JP-A-6-299366, etc. It is also possible to apply a system coating.
[0040]
Hereinafter, the method of the present invention will be described in order from the component composition of the electromagnetic steel sheet.
As a component of the steel plate used in the present invention, it is desirable to contain 1.5 to 7.0 mass% of Si. In other words, Si is an effective component for increasing the electrical resistance of the product and reducing iron loss, but if Si exceeds 7.0 mass%, the hardness tends to be high and manufacturing and processing tend to be difficult. On the other hand, if it is less than 1.5%, transformation occurs during final finish annealing, and a stable secondary recrystallized structure cannot be obtained.
[0041]
Moreover, crystal orientation can be further improved by containing 0.006 mass% or more of Al as an inhibitor element in the initial steel. The upper limit is about 0.06 mass%, and if it exceeds this, the crystal orientation deteriorates again.
[0042]
Further, in addition to the above-mentioned elements, the steel contains B, Bi, Sb, Mo, Te, Sn, P, Ge, As, Nb, Cr, as inhibitor components suitable for the production of known grain-oriented electrical steel sheets. Ti, Cu, Pb, Zn, and In are known, and these elements can be contained alone or in combination. The present invention can also be applied to grain-oriented electrical steel sheets by a method that does not use an inhibitor.
[0043]
Next, the manufacturing method of the electrical steel sheet of this invention is demonstrated in detail.
The steel slab adjusted to the above-mentioned predetermined components is usually subjected to slab heating and then hot-rolled coil by hot rolling. The heating temperature of this steel slab is set to a high temperature of 1300 ° C or higher. And a low temperature of 1250 ° C. or lower. In recent years, a method of directly performing hot rolling after continuous casting without performing slab heating has been developed. However, it can also be applied to the case of hot rolling by this method.
[0044]
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing as necessary, and is made into a final cold-rolled sheet by a plurality of rollings with one cold pressing or intermediate annealing. About these rolling, what was called warm rolling aiming at dynamic aging, and what carried out aging between passes aiming at static aging may be given.
[0045]
The steel sheet after the final cold rolling is subjected to primary recrystallization annealing that also serves as decarburization annealing, and is subjected to secondary recrystallization treatment by final finishing annealing to obtain a grain-oriented electrical steel sheet. Usually, after the primary recrystallization annealing, an annealing separator is applied to form a forsterite film at the final finish annealing, but this forsterite film is removed by pickling or polishing, or an annealing separator. The composition is adjusted to suppress the formation of a forsterite film on the surface of the steel sheet, so that it has a substantially metallic appearance.
[0046]
For the purpose of further reducing the iron loss, the magnetic domain is subdivided by irradiating the obtained steel plate with a laser or a plasma flame or the like without any problem in the adhesion of the insulating coating. In addition, at any stage of the manufacturing process of the grain-oriented electrical steel sheet according to the present invention, it is possible to further reduce iron loss by forming grooves at regular intervals by etching or tooth profile rolls on the steel sheet surface for magnetic domain fragmentation. It is effective as a means.
[0047]
【Example】
Example 1
Cold rolled coils containing C: 0.06 mass%, Si: 3.2 mass%, Mn: 0.07 mass% and Se: 0.04 mass%, rolled to a final sheet thickness of 0.23 mm, at 5 mm intervals for magnetic domain refinement After forming a plurality of grooves extending in the rolling direction by etching and performing primary recrystallization annealing that also serves as decarburization, a pure separation agent containing MgO as a main component and containing lead chloride is applied, and forsterite A final finish annealed steel sheet having a smooth surface with no coating was produced. The nitrogen content of the obtained steel sheet was below the measurement limit (5 ppm). The steel sheet was ion nitrided in a mixed atmosphere of nitrogen and hydrogen at 550 ° C. and 50 torr to obtain samples having various nitrogen contents in steel. Note that nitriding treatment was not performed on some samples.
[0048]
Then TiCl₄, H₂And N₂TiN was formed at a thickness of 1.0 μm per side in an atmosphere composed of the above mixed gas. TiCl₄Is gasified by heating to 150 ° C. with a vaporizer, and H₂And N₂Mixing was carried out at various mixing ratios with gas, and the respective partial pressures were adjusted. Next, after deposition of the TiN film, a solution obtained by adding 15 parts by weight of dichromic acid K to primary phosphoric acid Mg, 30 parts by weight of 30 mass% colloidal silica was mixed with a roll coater at 800 ° C. The insulating film was formed by baking for 1 minute. Further, annealing was performed at 850 ° C. for 3 hours as strain relief annealing.
[0049]
About the steel plate thus obtained, the film adhesion after strain relief annealing at 850 ° C. for 3 hours was evaluated by the minimum peel diameter. The evaluation results are shown in Table 2 together with the amount of nitrogen in the steel before TiN chemical vapor deposition and the appearance outside the coating. In Samples 4 to 6, the nitrogen content in the steel before chemical vapor deposition satisfies the requirements of the present invention, and exhibits a beautiful and excellent appearance and extremely excellent film adhesion. On the other hand, Sample 1 that was not subjected to nitridation by ion nitriding before chemical vapor deposition, and Samples 2 and 3 with insufficient nitrogen content had poor film adhesion after strain relief annealing and were originally gold. The close TiN film also turned brown.
[0050]
[Table 2]

[0051]
Example 2
C: 0.07 mass%, Si: 3.3 mass%, oxidation-soluble Al: 0.026 mass%, N: 0.008 mass%, and Sb: 0.05 mass%, a cold rolled sheet rolled to a final sheet thickness of 0.23 mm, primary In performing recrystallization annealing, the atmosphere oxidation property in primary recrystallization annealing was changed, and the raw material containing various carbon content was produced. Then, pickling₂After removing the oxide film mainly composed of the coating, alumina was used as an annealing separator, thereby obtaining a final finish annealing plate having a smooth surface without a forsterite coating. For the steel plate obtained, TiCl₄, H₂And CH₄TiC was formed with a thickness of 0.5 μm per side in an atmosphere composed of the above mixed gas. H₂Gas and CH₄The gas has various mixing ratios and TiCl₄Concentration is H₂TiCl using gas as carrier gas₄Adjustment was made by bubbling the liquid.
[0052]
Next, an insulating coating solution containing boric acid and boehmite as main components (molar ratio in terms of oxide B)₂O₃/ Al₂O₃= 0.5) was applied with a roll coater and baked at 800 ° C. for 120 seconds. Further, annealing was performed at 900 ° C. for 1 hour for tension application. Thereafter, annealing was performed at 850 ° C. for 3 hours as strain relief annealing.
[0053]
About the steel plate thus obtained, the film adhesion after strain relief annealing at 850 ° C. for 3 hours was evaluated by the minimum peel diameter. The evaluation results are shown in Table 3 together with the amount of nitrogen in the steel before TiC chemical vapor deposition and the appearance outside the coating. In Samples 4 to 6, the carbon content in the steel before chemical vapor deposition satisfied the requirements of the present invention, and a beautiful appearance and extremely excellent film adhesion were obtained. On the other hand, Samples 1 to 3 in which the carbon content before chemical vapor deposition was insufficient were inferior in film adhesion after strain relief annealing, and the film appearance was also remarkably black and a uniform film appearance was not obtained.
[0054]
[Table 3]

[0055]
Example 3
For the final finish annealed plate produced in the same manner as in Example 2, TiCl₄, CH_4,N_2,H₂TiCN was formed to a thickness of 0.7 μm per side in an atmosphere composed of a mixed gas of Ar and Ar. The molar ratio of C and N was not 1: 1 but varied somewhat, but no particular effect on adhesion and magnetic properties was found.
Next, a chromium-free coat in which manganese nitrate and colloidal silica were added to and mixed with primary aluminum phosphate was applied and baked at 850 ° C. Thereafter, strain relief annealing was performed at 820 ° C. for 3 hours to evaluate film adhesion. The evaluation results are shown in Table 4. Samples 4 to 6 are examples suitable for the present invention, and showed a beautiful appearance and extremely excellent film adhesion. On the other hand, Samples 1 to 3 in which the carbon content before chemical vapor deposition was insufficient were inferior in film adhesion after strain relief annealing, and the whitish golden TiCN changed to brown.
[0056]
[Table 4]

[0057]
【The invention's effect】
According to the present invention, a film having a large tension imparting effect and extremely excellent adhesion can be formed on the surface of a smooth grain-oriented electrical steel sheet without a forsterite film by chemical vapor deposition. It is possible to produce a grain-oriented electrical steel sheet having excellent iron loss value.

Claims (3)

It inhibited the formation of full Orusuteraito coating, or the surface of the grain-oriented electrical steel sheet final annealing already removing the forsterite film, a TiN film by thermal chemical vapor deposition process to heat the entire steel sheet or chemical vapor deposition layer upon, by containing nitrogen or 20ppm in the steel plate, in the thermal chemical vapor deposition process, and forming the TiN film by the reaction of Ti of nitrogen and the raw material gas in said steel sheet manufacturing method of a square oriented electrical steel sheet. It inhibited the formation of full Orusuteraito coating, or the surface of the grain-oriented electrical steel sheet final annealing already removing the forsterite film to form a TiC coating by a thermal chemical vapor deposition process to heat the entire steel sheet or chemical vapor deposition layer upon, is contained carbon than 20ppm in the steel plate, in the thermal chemical vapor deposition process, you and forming the TiC coating by reacting a Ti of nitrogen and the raw material gas in said steel sheet manufacturing method of a square oriented electrical steel sheet. It inhibited the formation of full Orusuteraito coating, or the surface of the grain-oriented electrical steel sheet final annealing already removing the forsterite film to form a TiCN coating by a thermal chemical vapor deposition process to heat the entire steel sheet or chemical vapor deposition layer At the time, at least one of carbon and nitrogen is contained in the steel plate in an amount of 20 ppm or more , and in the thermal chemical vapor deposition process, the nitrogen in the steel plate and Ti in the source gas are reacted to form the TiCN film. method for producing oriented electrical steel sheets towards you, characterized in that.