JP4029432B2 - Method for producing grain-oriented silicon steel sheet - Google Patents

Description

【００２０】
表１のNo.1とNo.2は、この発明の範囲の脱珪層を有する試料をこの発明に従う条件にて一次再結晶焼鈍したものであり、Ｃ含有量は十分に低く、酸素目付量も確保されており、また酸洗減量も低い値を示している。これに対して、No.3〜No.6は一次再結晶焼鈍条件はこの発明の範囲であるが、脱珪層がこの発明の範囲外の場合である。このうち、No.4のように脱珪層の大きさが過大である場合には、酸素目付量が不十分であり、酸洗減量も高めとなっている。そして、No.3, No.5, No.6のように脱珪層の大きさが過小である場合には、酸素目付量が若干高めであり、また酸洗減量が増大している。
次に、No.7〜No.12 は一次再結晶焼鈍時における昇温過程雰囲気と均熱過程雰囲気とを同一にした場合であり、Ｃ含有量が増大し、酸素目付量が不十分となり、酸洗減量が高めとなっている。そして、No.13 〜No.18 は均熱過程のP(H₂O)／P(H₂) が0.70を超えた場合であり、酸洗減量が著しく増大している。
【００２１】
以上に述べたところから、最終冷延板の状態で、表面から板厚方向に１μm の範囲において、板厚中心部でのSi濃度に対するSi濃度の比を0.90以下とし、かつ板厚中心部でのSi濃度に対するSi濃度の比が0.98以下となる板厚方向距離を表面から５μm 以下の範囲とする脱珪層を形成させ、かつ均熱過程のP(H₂O)／P(H₂) を0.70未満とし昇温過程のP(H₂O)／P(H₂) を均熱過程のそれよりも低下することによって、良好な物性を有するサブスケールが得られることがわかる。
【００２２】
このように一次再結晶焼鈍工程において、昇温過程の雰囲気酸化性を均熱過程のそれよりも低下させることによってサブスケール品質が向上するメカニズムはまだ明らかでないが、昇温過程でのサブスケール形成を均熱過程よりも緩やかに進行させることにより、酸化初期に生成する酸化物の形態や物性が変化し、その後の均熱過程における酸素の鋼中への拡散に影響を及ぼすためと考えられる。また、一次再結晶焼鈍時の均熱過程のP(H₂O)／P(H₂) が0.70以上になるとサブスケール品質が劣化するのは、図２に示すけい素鋼板の表面に生成する酸化物から考えると、FeO の生成によるものと思われる。このFeO は酸素の内部拡散ではなく、Feの外部拡散によって生成する酸化物であり、このような酸化物が表面にいったん生成すると被膜の形成過程に重大な悪影響を及ぼすものと思われる。
【００２３】
更に、脱珪層が過小である場合にサブスケール品質が劣化するのは、表面付近でのSi濃度が高すぎるため昇温過程でのサブスケール生成が過剰に進行する結果、酸化初期に生成する酸化物の形態が均熱過程における酸化の鋼中への拡散に好影響を及ぼす状態にはならないためと考えられる。逆に、脱珪層が過大である場合にサブスケール品質が劣化するのは、表面近傍でのSi濃度が低すぎるためサブスケール形成が遅滞するためと考えられる。
【００２４】
次に、発明者らは適正な脱珪層を得るための最終冷延前の焼鈍の条件についても検討した。
Ｃ含有量が0.04wt％であり、インヒビターとしてMnSe及びSbを含むけい素鋼冷延板（板厚0.6 mm）を脱脂して表面を清浄化した後、湿水素中にて900 ℃に１分間保持する中間焼鈍を行った。このとき水素濃度と露点との調節によってP(H₂O)／P(H₂) を0.10から1.20の範囲で変化させた。その後、外部スケールの生成した試料についてはHCl 酸洗を施して外部スケールだけを除去した。このときの板厚方向Si分布をEPMAマッピングによって調べ、最終冷延板厚0.23mmに換算した脱珪層プロファイルを図３に示す。図３によれば、中間焼鈍雰囲気がP(H₂O)／P(H₂) 0.20未満になると、脱珪層の形成が抑制されている。また、中間焼鈍雰囲気がP(H₂O)／P(H₂)1.00 を超えると、表面近傍でのSi濃度は大きく低下するが脱珪層の深さが小さくなっている。
【００２５】
以上に述べたように、最終冷延板の状態で、表面から板厚方向１μm の範囲において、板厚中心部でのSi濃度に対するSi濃度の比を0.90以下とし、かつ板厚中心でのSi濃度に対するSi濃度の比が0.98以下になる板厚方向の距離を５μm 以下とする脱珪層を形成させるためには、中間焼鈍を、水素分圧に対する水蒸気分圧の比が0.20以上1.00以下の範囲で行えばよいことがわかる。なお、中間焼鈍後の酸洗は外部スケールの除去にとどめることが肝要であり、過剰な酸洗を行った場合には、適正に形成された脱珪層が除去されてしまうので注意が必要である。この他に脱珪層プロファイルを制御する方法として中間焼鈍後に研削する方法があるが、酸洗の場合と同様に、過剰な研削を行った場合には、適正に形成された脱珪層が除去されてしまうので注意が必要である。また、中間焼鈍の時間が長すぎる場合には、雰囲気をP(H₂O)／P(H₂) で0.20以上1.00以下の範囲に設定しても脱珪層の大きさが過大になり過ぎてサブスケール物性に悪影響を及ぼすうえに、仕上げ焼鈍におけるインヒビターの一次粒成長抑制力の劣化が生じることがあるため、中間焼鈍の均熱時間は30秒〜120 秒程度とするのが適当である。
【００２６】
このような中間焼鈍での脱珪層形成メカニズムはまだ十分に明らかになってはいないが、雰囲気のP(H₂O)／P(H₂) が0.2 未満の場合に脱珪層の生成が抑制されるのは、雰囲気酸化性が低すぎて中間焼鈍での内部酸化の進行が遅滞するためと推定される。逆に、雰囲気のP(H₂O)／P(H₂) が1.00を超える場合に表面のSi濃度が大きく低下するが脱珪層の深さが小さくなるのは、外部スケールの生成が増大した結果、表面近傍のFe消費量が多くなってSi濃度が高くなるためと推定される。
【００２７】
この発明に従う脱珪層を脱炭焼鈍前の鋼板表面に形成させるには、上述した中間焼鈍での雰囲気制御に限られず、熱延板焼鈍の際に、雰囲気制御することによっても可能である。具体的には、冷延１回法において水素分圧に対する水蒸気分圧の比を0.20以上・1.00以下の範囲で熱延板焼鈍を行うことによって所定の脱珪層プロファイルを得ることができる。
さらに、熱延板焼鈍及び中間焼鈍の双方で雰囲気制御を行うことも可能であるが、この場合は、所定の脱珪層を得るために、熱延板焼鈍雰囲気をP(H₂O)／P(H₂) で0.6 〜1.0 、中間焼鈍雰囲気をP(H₂O)／P(H₂) で0.2 〜0.7 となるように雰囲気を調整することが好ましい。
【００２８】
なお、以上の実験例はインヒビターとして、MnSeとSbを含有する鋼種で示したが、この発明はこれに限らずAlN-MnSe系、AlN-MnS 系、MnS 系等、他のインヒビターを含有する方向性けい素鋼のいずれに対しても適用できる。
【００２９】
次に、この発明における方向性けい素鋼用素材の好適成分組成について説明する。
Ｃは、熱間圧延時のα−γ変態を利用して結晶組織の改善を行うために有効であるが、多すぎると脱炭が困難となるため、0.02〜0.10wt％の範囲が好適である。
Siは、少な過ぎると鋼板の電気抵抗が小さくなって渦電流損が増大するために良好な鉄損特性が得られず、多過ぎると冷間圧延が困難となるので、2.5 〜4.5 wt％程度の範囲が好適である。
Mnは、インヒビター成分として必要であるが、過剰になるとインヒビターの粒子径が粗大化して粒成長抑制力が低下するため、0.03〜0.30wt％の範囲が好適である。
Se及び／又はＳはインヒビター成分として必要であるが、過剰になると仕上げ焼鈍での純化が困難となるため、合計で0.01〜0.05wt％の範囲が好適である。
Al及びＮはAlN インヒビターを形成するために必要である。Alは少な過ぎると磁束密度が低下し、多過ぎると二次再結晶が安定しなくなるため、酸可溶性Alとして0.01〜0.05wt％の範囲が好適である。一方、Ｎは少な過ぎるとAlN インヒビターの量が不足して磁束密度が低下し、多過ぎるとスラブ加熱中のふくれに起因する表面欠陥が製品に多発するため、0.004 〜0.012 wt％の範囲が好適である。
【００３０】
さらに、粒界偏析型インヒビターとしてSbやSn等の添加が有効である。これらは、添加量が少な過ぎると磁気特性の改善効果が少なく、多過ぎると脆性の低下やフォルステライト質絶縁被膜への悪影響が生じるため、0.01〜0.03wt％の範囲が好適である。また、フォルステライト質絶縁被膜への悪影響を減ずるためには、0.03〜0.20wt％のCuを添加したうえで、この発明に従って一次再結晶焼鈍を行うことが有効である。
また、熱間圧延時の表面脆化に起因する表面欠陥を防止するために、0.10wt％以下のMoを添加することも有効である。
【００３１】
【実施例】
〈実施例１〉
Ｃ：0.073 wt％, Si：3.30wt％, Mn：0.075 wt％, Se：0.024 wt％, sol.Al：0.024 wt％, Ｎ：0.008 wt％及びSb：0.025 wt％を含有する方向性けい素鋼スラブを板厚2.3 mmに熱間圧延した後、1000℃で熱延板焼鈍を行い、1100℃での中間焼鈍を挟む２回の冷間圧延によって0.23mmの最終冷延板厚とした。このとき中間焼鈍時間と中間焼鈍後の酸洗時間の制御によって最終冷延板の状態での脱珪層を図４のように変化させた。これらの冷延板をアルカリ脱脂して表面を清浄化した後、湿水素雰囲気中にて、840 ℃で120 秒の一次再結晶焼鈍を行った。このとき、昇温過程及び均熱過程の雰囲気酸化性をそれぞれ独立に表２に示す値に制御した。次いで、５％のTiO₂を含有するMgO 焼鈍分離剤をスラリーとして塗布、乾燥後、H₂雰囲気中での1200℃で10時間の二次再結晶、純化焼鈍を行った。この後、リン酸マグネシウムとコロイダルシリカを主成分とするコーティングを施した。
【００３２】
このようにして得られた製品の、磁界800 A/m における磁束密度Ｂ₈ 値、1.7 T, 50Hz における鉄損W_17/50値、被膜の曲げ密着性、及び被膜外観の均一性について調査した。被膜の曲げ密着性は、５mm間隔の種々の径を有する丸棒に試験片を巻き付け、被膜の剥離が生じない最小径で評価した。また、一次再結晶後の鋼板のＣ含有量、酸素目付量、酸洗減量についても分析を行った。これらの結果を表２に併記する。
【００３３】
表２によれば、脱珪層が過大であるNo.7では酸素目付量が不十分であり、その結果、磁気特性、被膜特性が劣っている。脱珪層が過小であるNo.8では、酸洗減量が高く、磁気特性、被膜特性が劣っている。均熱過程のP(H₂O)／P(H₂) が0.70を超えたNo.9、No.10 は、酸洗減量が著しく高く、磁気特性、被膜特性が劣っている。また、昇温過程のP(H₂O)／P(H₂) を均熱過程のそれよりも低くしなかったNo.11 、No.12 は脱炭と酸素目付量が不十分であり、かつ磁気特性、被膜特性も劣っている。これらに対して、この発明に従うNo.1〜No.6は、脱炭、酸素目付量、酸洗減量が良好なレベルであり、製品の磁気特性、被膜特性ともに優れている。
【００３４】
【表２】

【００３５】
〈実施例２〉
Ｃ：0.073 wt％, Si：3.30wt％, Mn：0.075 wt％, Se：0.024 wt％, sol.Al：0.024 wt％, Ｎ：0.008 wt％及びSb：0.025 wt％を含有する方向性けい素鋼スラブを板厚2.7 mmに熱間圧延した後、1000℃で熱延板焼鈍を行い、次いで湿水素中で1120℃での中間焼鈍及びそれに引き続く外部スケール除去の目的で行う酸洗をはさむ２回の冷間圧延によって0.35mmの最終冷延板厚とした。このとき中間焼鈍の雰囲気酸化性を表３に示す値に制御した。これらの冷延板をアルカリ脱脂して表面を清浄化した後、湿水素雰囲気中にて、840 ℃で150 秒の一次再結晶焼鈍を行った。このとき、昇温過程及び均熱過程の雰囲気酸化性をそれぞれ独立に表３に示す値に制御した。次いで、５％のTiO₂を含有するMgO 焼鈍分離剤をスラリーとして塗布、乾燥後、H₂雰囲気中での1200℃で10時間の二次再結晶、純化焼鈍を行った。この後、リン酸マグネシウムとコロイダルシリカを主成分とするコーティングを施した。このようにして得られた製品について、実施例１と同様の調査を行った結果を表３に示す。
【００３６】
表３によれば、中間焼鈍雰囲気のP(H₂O)／P(H₂) が0.20未満であるNo.7、及びP(H₂O)／P(H₂) が1.00を超えているNo.8では酸素目付量が不十分であり、その結果、磁気特性、被膜特性が劣っている。均熱過程のP(H₂O)／P(H₂) が0.70を超えたNo.9、No.10 は、酸洗減量が著しく高く、磁気特性、被膜特性が劣っている。また、昇温過程のP(H₂O)／P(H₂) を均熱過程のそれよりも低くしなかったNo.11 、No.12 は脱炭と酸素目付量が不十分であり、かつ磁気特性、被膜特性も劣っている。これらに対して、この発明に従うNo.1〜No.6は、脱炭、酸素目付量、酸洗減量が良好なレベルであり、製品の磁気特性、被膜特性ともに優れている。
【００３７】
【表３】

【００３８】
〈実施例３〉
Ｃ：0.042 wt％, Si：3.32wt％, Mn：0.073 wt％, Se：0.023 wt％及びSb：0.026 wt％を含有する方向性けい素鋼スラブを板厚2.0 mmに熱間圧延した後、950 ℃で熱延板焼鈍を行い、次いで湿水素中で970 ℃での中間焼鈍及びそれに引き続く外部スケール除去の目的で行う酸洗をはさむ２回の冷間圧延によって0.23mmの最終冷延板厚とした。このとき中間焼鈍の雰囲気酸化性を表４に示す値に制御した。これらの冷延板をアルカリ脱脂して表面を清浄化したあと、湿水素雰囲気中にて、820 ℃で120 秒の一次再結晶焼鈍を行った。このとき、昇温過程及び均熱過程の雰囲気酸化性をそれぞれ独立に表４に示す値に制御した。次いで、１％のTiO₂及び２％のSrSO₄ を含有するMgO 焼鈍分離剤をスラリーとして塗布、乾燥後、H₂雰囲気中での1150℃で８時間の二次再結晶、純化焼鈍を行った。この後、リン酸マグネシウムとコロイダルシリカを主成分とするコーティングを施した。このようにして得られた製品について、実施例１と同様の調査を行った結果を表４に示す。
【００３９】
表４によれば、中間焼鈍雰囲気のP(H₂O)／P(H₂) が0.20未満であるNo.5、及びP(H₂O)／P(H₂) が1.00を超えているNo.6では酸素目付量が不十分であり、その結果、磁気特性、被膜特性が劣っている。均熱過程のP(H₂O)／P(H₂) が0.70を超えたNo.7では、酸洗減量が著しく高く、磁気特性、被膜特性が劣っている。また、昇温過程のP(H₂O)／P(H₂) を均熱過程のそれよりも低くしなかったNo.8では、脱炭と酸素目付量が不十分であり、且つ磁気特性、被膜特性も劣っている。これらに対して、この発明例であるNo.1〜No.4は、脱炭、酸素目付量、酸洗減量が良好なレベルであり、製品の磁気特性、被膜特性ともに優れている。
【００４０】
【表４】

【００４１】
【発明の効果】
この発明によれば、被膜特性に優れ且つ磁気特性も良好な方向性けい素鋼板の安定して生産することができる。
【図面の簡単な説明】
【図１】最終冷延板の状態での脱珪層プロファイルを示すグラフである。
【図２】３wt％けい素鋼の湿水素中における生成酸化物の平衡状態図である。
【図３】中間焼鈍雰囲気のP(H₂O)／P(H₂) を変化させたときの、最終冷延板の状態での脱珪層プロファイルを示すグラフである。
【図４】実施例１に供した試料の最終冷延板の状態での脱珪層プロファイルを示すグラフである。[0001]
[Industrial application fields]
The present invention relates to a method of manufacturing a grain-oriented silicon steel sheet, and in particular, attempts to improve magnetic properties and forsterite insulating coating properties by devising both the annealing before the final cold rolling and the primary recrystallization annealing process. It is.
[0002]
[Prior art]
Oriented silicon steel sheets are used as soft magnetic materials mainly as iron core materials such as transformers and rotators, and are required to have high magnetic flux density and small iron loss and magnetostriction as magnetic properties. With the recent deterioration of energy situation, the need for grain oriented silicon steel sheets with excellent magnetic properties is increasing.
In order to obtain a grain oriented silicon steel sheet having excellent magnetic properties, it is necessary to obtain a secondary crystal structure that is highly integrated in the {110} <001> orientation, the so-called Goth orientation.
[0003]
In order to obtain a secondary recrystallized structure that is highly accumulated in such Goss orientation, grain-oriented silicon steel sheets are generally required after heating and rolling the grain-oriented silicon steel slab containing the inhibitor. In accordance with the hot-rolled sheet annealing, the final product sheet thickness is obtained by one or more cold rollings with one or more intermediate annealings, and after primary recrystallization annealing, the steel sheet is annealed with MgO as the main component. It is manufactured by applying an agent, winding it into a coil, and performing high-temperature finish annealing. There are several important points that greatly affect product quality in the manufacturing process of such a directional silicon steel sheet, and one of them is the primary recrystallization annealing process.
[0004]
Normal primary recrystallization annealing is performed by performing soaking for a certain period of time in a temperature range of 700 to 900 ° C in a wet hydrogen atmosphere gas whose atmosphere oxidizability is controlled by adjusting the H ₂ concentration and dew point. The At this time, C diffused from the inside of the steel plate to the steel plate surface reacts with H ₂ O on the steel plate surface to become CO gas, and C is removed from the steel plate. The reaction at this time is as shown in Formula 1.
C + H ₂ O → CO + H ₂ (Formula 1)
[0005]
Because this reaction occurs, primary recrystallization annealing is also called decarburization annealing. At the same time as the decarburization reaction occurs according to the above reaction formula, Si contained in the grain-oriented silicon steel sheet is oxidized by H ₂ O to form a subscale mainly composed of SiO ₂ and Fe ₂ SiO ₄ . The reaction at this time is as shown in Formulas 2 and 3.
Si + 2H ₂ O → SiO ₂ + 2H ₂ (Formula 2)
Si + 2Fe + 4H ₂ O → Fe ₂ SiO ₄ + 4H ₂ (Formula 3)
Among these reactions, since the reaction of Formula 2 proceeds from a very low dew point, the formation of subscales is unavoidable when ordinary industrial gases are used.
[0006]
As described above, the generation of subscale is an inevitable phenomenon in the primary recrystallization annealing of the grain-oriented silicon steel sheet. The forsterite insulating coating formed on the surface of the steel sheet of the product is a clever use of this subscale. This forsterite insulating coating is generally formed by the following process.
[0007]
First, primary recrystallization annealing as described above is performed on the final cold-rolled sheet of grain-oriented silicon steel sheet cold-rolled to a desired final sheet thickness. That is, continuous annealing is performed in wet hydrogen at a temperature of 700 ° C to 900 ° C, and the structure after cold rolling is subjected to secondary recrystallization so that proper secondary recrystallization occurs in final finish annealing, and at the same time, secondary In order to completely recrystallize and prevent aging deterioration of the magnetic properties of the product, carbon contained in the steel in an amount of about 0.01 to 0.10% is decarburized to 0.003% or less. At the same time, a subscale mainly composed of SiO ₂ is generated on the steel sheet surface layer by oxidation of Si in the steel. This subscale is one of the raw materials for the forsterite insulating coating.
[0008]
After that, an annealing separator mainly composed of MgO is applied on the steel sheet, wound into a coil, and subjected to high-temperature finish annealing at a temperature of about 1000 to 1200 ° C in a reducing or non-oxidizing atmosphere. A forsterite insulating film is formed by a solid-phase reaction represented by Formula 4.
2MgO + SiO ₂ → Mg ₂ SiO ₄ (Formula 4)
[0009]
This forsterite insulating coating is a ceramic coating in which fine crystals of about 1 μm are densely accumulated. As described above, one of the subscales mainly composed of SiO ₂ formed on the steel sheet surface layer during primary recrystallization annealing is used. Since it is formed on the steel sheet as a raw material, the type, amount, distribution, etc. of this oxide affect the nucleation and grain growth behavior of forsterite, and further the grain boundary of forsterite crystal grains. It also affects the strength of the grains themselves and therefore has a great influence on the quality of the coating after finish annealing.
[0010]
In addition, the annealing separation agent mainly composed of MgO, which is the other raw material, is applied to the steel sheet as a slurry suspended in water, so that it retains physically adsorbed H ₂ O after drying, Since a part of it is hydrated and changed to Mg (OH) ₂ , H ₂ O continues to be released in a small amount until around 800 ° C. during the final annealing. This H ₂ O oxidizes the steel sheet surface during finish annealing. This oxidation also affects the formation behavior of the forsterite insulating coating and leads to oxidation and decomposition of the inhibitor. Therefore, if this oxidation is large, the magnetic properties are deteriorated. The susceptibility to oxidation by H ₂ O released from MgO is also greatly influenced by the physical properties of the subscale formed by primary recrystallization annealing.
[0011]
As described above, it is important from the viewpoint of preventing the quality deterioration of the forsterite insulating coating and the deterioration of the magnetic properties to appropriately control the subscale quality generated in the primary recrystallization annealing of the grain-oriented silicon steel sheet. Technical issue.
[0012]
Regarding the primary recrystallization annealing of grain-oriented silicon steel sheets, for example, as disclosed in Japanese Patent Publication No. 57-1575, the oxidation degree of the atmosphere is 0.15 or more in the first half of decarburization, and 0.75 or less for steel sheets and As disclosed in JP-A-6-336616, the ratio of water vapor partial pressure to hydrogen partial pressure in the soaking process is less than 0.70 and the hydrogen partial pressure in the temperature rising process is as disclosed in JP-A-6-336616. A method for setting the ratio of water vapor partial pressure to a value lower than that in the soaking process is known.
[0013]
[Problems to be solved by the invention]
However, although the above method is recognized to have a certain effect, it is not always sufficient, and the magnetic properties and the adhesion, thickness, and uniformity of the forsterite insulating film may deteriorate in the width direction or longitudinal direction of the strip. There was still room for improvement in order to stably produce products with excellent quality and to further improve yields.
[0014]
The present invention is intended to advantageously solve the above-described problems, and provides a forsterite insulating coating film having good magnetic characteristics over the entire width and length of the coil, and having no defects and uniform adhesion. It aims at proposing about the manufacturing method for obtaining the grain-oriented silicon steel plate which has stably.
[0015]
[Means for Solving the Problems]
The inventors investigated in detail the influence of the surface state of the final cold-rolled sheet on the subscale physical properties generated by the primary recrystallization annealing. As a result, the profile of the desiliconized layer formed in the thickness direction of the final cold-rolled sheet greatly fluctuates within and between the coils, and the profile of the desiliconized layer is within an appropriate range. In particular, the effect of the method disclosed in JP-A-6-336616 can be sufficiently obtained, and the pickling condition following the intermediate annealing atmosphere and the intermediate annealing, or the hot rolled sheet annealing condition and the hot rolled sheet annealing can be used. It has been clarified that the subsequent pickling conditions have a great influence on the profile of the desiliconized layer, and the present invention has been completed.
[0016]
That is, this invention, after the directional silicon steel slab was hot-rolled, and facilities the hot-rolled sheet annealing emergence line cold rolling two or more times sandwiching once or intermediate annealing or hot-rolled sheet, Perform cold rolling at least twice with intermediate annealing and omitting annealing , then decarburize annealing to form a subscale on the steel plate surface, and then apply annealing separator mainly composed of MgO In the method for producing a directional silicon steel sheet comprising a series of steps in which finish annealing is performed to form a forsterite film on the steel sheet surface,
By controlling the ratio of steam partial pressure to hydrogen partial pressure in the atmosphere of the hot-rolled sheet annealing and / or intermediate annealing, the steel sheet surface before decarburization annealing to form a de-珪層, if necessary, the final cold By pickling and / or grinding before rolling, the ratio of Si concentration to the Si concentration at the center of the thickness of the desiliconized layer is determined in the region from the steel sheet surface to the thickness direction of 1 μm in the final cold-rolled sheet state. Adjusting the region where the Si concentration ratio is 0.98 or less from the surface to 5 μm in the thickness direction, and the decarburization annealing, the ratio of the water vapor partial pressure to the hydrogen partial pressure in the soaking process is less than 0.70, and a method for producing tropism silicon steel sheet towards you and performs the ratio of steam partial pressure to hydrogen partial pressure in the temperature rising process at a lower value than the soaking process (the first invention).
Further, according to the present invention, in the first invention, the desiliconization layer is formed by controlling the ratio of the water vapor partial pressure to the hydrogen partial pressure within the range of 0.20 to 1.00 during annealing performed before the decarburization annealing. which is a method for producing tropism silicon steel sheet toward you characterized (second invention).
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The inventors investigated in detail the influence of the desiliconized layer profile formed in the thickness direction of the final cold-rolled sheet on the subscale physical properties generated by the primary recrystallization annealing. The experimental results will be described below.
After hot rolling a directional silicon steel material with a C content of 0.04wt% and containing MnSe and Sb as inhibitors, hot-rolled sheet annealing is performed at 900 ° C, followed by two colds sandwiching the intermediate annealing. A final cold-rolled sheet having a thickness of 0.23 mm was obtained by rolling. At this time, the desiliconized layer profile in the plate thickness direction shown in FIG. 1 was formed by variously changing the time of the intermediate annealing and the pickling time after the intermediate annealing. The atmosphere during hot-rolled sheet annealing is P (H ₂ O) / P (H ₂ ) = 0.70, and the atmosphere during intermediate annealing is P (H ₂ O) / P (H ₂ ) = 0.50. About the formed siliconization layer, Si distribution of the sample cross section before the final cold rolling was examined by EPMA mapping, and this was converted into a profile at the final cold rolled sheet thickness and evaluated.
Next, these cold-rolled plates were degreased to clean the surface, and then subjected to primary recrystallization annealing in wet hydrogen at 830 ° C. for 2 minutes. At this time, the atmospheric oxidation property of the temperature raising process and the soaking process was controlled to the values shown in Table 1.
[0018]
Thereafter, the amount of C and the amount of oxygen in the steel were determined by chemical analysis. Further, the dissolution amount of the sample after primary recrystallization annealing by pickling for 60 seconds in 5% HCl at 60 ° C. (hereinafter referred to as pickling loss) was determined. These results are shown in Table 1. This amount of oxygen is important as a subscale quantitative index. If this amount is insufficient, the adhesion and appearance uniformity of the forsterite insulating coating deteriorate, and the magnetic properties also deteriorate. In addition, pickling loss is important as a subscale qualitative index, and if this value is large, the chemical activity of the surface is so high that it is susceptible to additional oxidation during finish annealing, and the forsterite insulation coating Degradation of quality and magnetic properties occurs.
[0019]
[Table 1]

[0020]
No. 1 and No. 2 in Table 1 are obtained by subjecting a sample having a desiliconized layer within the scope of the present invention to primary recrystallization annealing under the conditions according to the present invention, the C content being sufficiently low, and the oxygen basis weight. The pickling weight loss is also low. On the other hand, in No. 3 to No. 6, the primary recrystallization annealing conditions are within the scope of the present invention, but the desiliconized layer is outside the scope of the present invention. Among these, when the size of the desiliconized layer is excessive as in No. 4, the amount of oxygen per unit area is insufficient and the pickling loss is also increased. When the size of the desiliconized layer is too small, such as No. 3, No. 5, and No. 6, the oxygen basis weight is slightly higher and the pickling loss is increased.
Next, No. 7 to No. 12 are cases where the temperature raising process atmosphere and the soaking process atmosphere at the time of primary recrystallization annealing are the same, the C content increases, the oxygen basis weight becomes insufficient, Pickling weight loss is high. No. 13 to No. 18 are cases where P (H ₂ O) / P (H ₂ ) in the soaking process exceeds 0.70, and the pickling weight loss is remarkably increased.
[0021]
As described above, in the final cold-rolled sheet state, the ratio of the Si concentration to the Si concentration at the center of the plate thickness is 0.90 or less in the range of 1 μm from the surface to the plate thickness direction, and at the center of the plate thickness. Forming a desiliconized layer with a thickness direction distance of 5 μm or less from the surface so that the ratio of the Si concentration to the Si concentration is 0.98 or less, and P (H ₂ O) / P (H ₂ ) in the soaking process It can be seen that a subscale having good physical properties can be obtained by reducing P (H ₂ O) / P (H ₂ ) in the temperature rising process to be lower than that in the soaking process with a value of less than 0.70.
[0022]
In this way, in the primary recrystallization annealing process, the mechanism by which the subscale quality is improved by lowering the atmospheric oxidizability in the temperature rising process than that in the soaking process is not yet clear, but the subscale formation in the temperature rising process is still unclear. This is thought to be due to the fact that the form and physical properties of the oxide formed in the initial stage of oxidation change by affecting the diffusion of oxygen into the steel during the subsequent soaking process. In addition, when P (H ₂ O) / P (H ₂ ) in the soaking process during primary recrystallization annealing is 0.70 or more, the subscale quality deteriorates on the surface of the silicon steel sheet shown in FIG. From the viewpoint of oxides, this is probably due to the formation of FeO. This FeO is an oxide generated not by oxygen internal diffusion but by Fe external diffusion, and once such oxide is formed on the surface, it seems to have a serious adverse effect on the film formation process.
[0023]
Furthermore, when the siliconized layer is too small, the subscale quality deteriorates because the Si concentration in the vicinity of the surface is too high, resulting in excessive subscale generation during the temperature rising process, resulting in early oxidation. This is presumably because the oxide morphology does not positively affect the diffusion of oxidation into the steel during the soaking process. On the contrary, when the siliconized layer is excessive, the subscale quality is deteriorated because the subscale formation is delayed because the Si concentration near the surface is too low.
[0024]
Next, the inventors also examined the annealing conditions before the final cold rolling to obtain an appropriate desiliconized layer.
After degreasing a silicon steel cold-rolled sheet (thickness 0.6 mm) containing MnSe and Sb as inhibitors with a C content of 0.04 wt%, the surface was cleaned at 900 ° C for 1 minute in wet hydrogen The intermediate annealing to hold | maintain was performed. At this time, P (H ₂ O) / P (H ₂ ) was changed in the range of 0.10 to 1.20 by adjusting the hydrogen concentration and the dew point. Thereafter, the sample with the external scale formed was subjected to HCl pickling to remove only the external scale. The thickness distribution Si distribution at this time was examined by EPMA mapping, and a desiliconized layer profile converted to a final cold-rolled sheet thickness of 0.23 mm is shown in FIG. According to FIG. 3, when the intermediate annealing atmosphere is less than P (H ₂ O) / P (H ₂ ) 0.20, formation of the desiliconized layer is suppressed. When the intermediate annealing atmosphere exceeds P (H ₂ O) / P (H ₂ ) 1.00, the Si concentration near the surface is greatly reduced, but the depth of the desiliconized layer is reduced.
[0025]
As described above, in the state of the final cold-rolled sheet, the ratio of the Si concentration to the Si concentration at the center of the plate thickness is 0.90 or less in the range from the surface to the plate thickness direction of 1 μm, and the Si at the center of the plate thickness. In order to form a desiliconized layer in which the distance in the thickness direction where the ratio of Si concentration to concentration is 0.98 or less is 5 μm or less, intermediate annealing is performed with the ratio of water vapor partial pressure to hydrogen partial pressure being 0.20 or more and 1.00 or less. It turns out that it is sufficient to do within a range. In addition, it is important that the pickling after the intermediate annealing is limited to the removal of the external scale. If excessive pickling is performed, care must be taken because the properly formed silicon removal layer will be removed. is there. In addition to this, there is a method of grinding after intermediate annealing as a method of controlling the desiliconization layer profile, but in the same way as pickling, when excessive grinding is performed, the properly formed desiliconization layer is removed. It is necessary to be careful. If the annealing time is too long, the size of the desiliconized layer will be too large even if the atmosphere is set to a range of 0.20 or more and 1.00 or less in P (H ₂ O) / P (H ₂ ). In addition to adversely affecting the physical properties of subscales, the primary grain growth inhibitory force of the inhibitor in finish annealing may deteriorate, so it is appropriate to set the soaking time for intermediate annealing to about 30 to 120 seconds. .
[0026]
The mechanism of desiliconization layer formation in such intermediate annealing has not been clarified yet, but the formation of desiliconization layer occurs when the atmosphere P (H ₂ O) / P (H ₂ ) is less than 0.2. It is presumed that the atmospheric oxidation is too low, and the progress of internal oxidation in the intermediate annealing is delayed. Conversely, when the P (H ₂ O) / P (H ₂ ) in the atmosphere exceeds 1.00, the Si concentration on the surface is greatly reduced, but the depth of the desiliconized layer is reduced, which increases the generation of external scales. As a result, it is estimated that the Fe concentration near the surface increases and the Si concentration increases.
[0027]
The formation of the desiliconized layer according to the present invention on the surface of the steel sheet before decarburization annealing is not limited to the above-described atmosphere control in the intermediate annealing, and it is also possible to control the atmosphere during the hot-rolled sheet annealing. Specifically, a predetermined desiliconized layer profile can be obtained by performing hot-rolled sheet annealing in a single cold rolling method with a ratio of water vapor partial pressure to hydrogen partial pressure in the range of 0.20 to 1.00.
Furthermore, it is possible to control the atmosphere in both hot-rolled sheet annealing and intermediate annealing. In this case, in order to obtain a predetermined desiliconized layer, the hot-rolled sheet annealing atmosphere is changed to P (H ₂ O) / P (H ₂ ) 0.6 to 1.0, intermediate annealing atmosphere is P (H ₂ O) / P (H ₂ ) It is preferable to adjust the atmosphere to be 0.2 to 0.7.
[0028]
In addition, although the above experiment example showed the steel type containing MnSe and Sb as an inhibitor, this invention is not restricted to this, The direction which contains other inhibitors, such as AlN-MnSe system, AlN-MnS system, MnS system, etc. It can be applied to any of the characteristic silicon steels.
[0029]
Next, the preferred component composition of the directional silicon steel material in this invention will be described.
C is effective for improving the crystal structure by utilizing the α-γ transformation during hot rolling, but if it is too much, decarburization becomes difficult, so a range of 0.02 to 0.10 wt% is preferable. is there.
If Si is too little, the electrical resistance of the steel sheet will decrease and eddy current loss will increase, so that good iron loss characteristics will not be obtained, and if it is too much, cold rolling will be difficult, so about 2.5 to 4.5 wt% The range of is preferable.
Mn is necessary as an inhibitor component, but if it is excessive, the particle diameter of the inhibitor becomes coarse and the ability to suppress grain growth decreases, so a range of 0.03 to 0.30 wt% is suitable.
Se and / or S is necessary as an inhibitor component , but if it is excessive, purification by finish annealing becomes difficult, so a total range of 0.01 to 0.05 wt% is preferable.
Al and N are necessary to form an AlN inhibitor. If the Al content is too small, the magnetic flux density will decrease, and if it is too much, secondary recrystallization will not be stable, so a range of 0.01 to 0.05 wt% is preferred as the acid-soluble Al. On the other hand, if the amount of N is too small, the amount of AlN inhibitor is insufficient and the magnetic flux density is lowered. If the amount is too large, surface defects due to blistering during slab heating frequently occur in the product, so the range of 0.004 to 0.012 wt% is preferable. It is.
[0030]
Furthermore, addition of Sb, Sn, etc. is effective as a grain boundary segregation type inhibitor. If the added amount is too small, the effect of improving the magnetic properties is small. If the added amount is too large, the brittleness is lowered or the forsterite insulating film is adversely affected. Therefore, the range of 0.01 to 0.03 wt% is preferable. In order to reduce the adverse effect on the forsterite insulating coating, it is effective to add 0.03 to 0.20 wt% of Cu and perform primary recrystallization annealing according to the present invention.
In order to prevent surface defects caused by surface embrittlement during hot rolling, it is also effective to add 0.10 wt% or less of Mo.
[0031]
【Example】
<Example 1>
Directional silicon containing C: 0.073 wt%, Si: 3.30 wt%, Mn: 0.075 wt%, Se: 0.024 wt%, sol.Al: 0.024 wt%, N: 0.008 wt% and Sb: 0.025 wt% after hot rolling the steel slab thickness 2.3 mm, subjected to hot rolled sheet annealing at 1000 ° C., and a final cold-rolled sheet thickness of 0.23mm by two cold rolling sandwiching an intermediate annealing at 1100 ° C.. At this time, the desiliconized layer in the state of the final cold-rolled sheet was changed as shown in FIG. 4 by controlling the intermediate annealing time and the pickling time after the intermediate annealing. These cold-rolled sheets were degreased with alkali to clean their surfaces, and then subjected to primary recrystallization annealing at 840 ° C. for 120 seconds in a wet hydrogen atmosphere. At this time, the atmospheric oxidizability of the temperature raising process and the soaking process was independently controlled to the values shown in Table 2. Next, an MgO annealing separator containing 5% TiO ₂ was applied as a slurry, dried, and then subjected to secondary recrystallization and purification annealing at 1200 ° C. for 10 hours in an H ₂ atmosphere. Thereafter, a coating mainly composed of magnesium phosphate and colloidal silica was applied.
[0032]
The product thus obtained was investigated for magnetic flux density B ₈ value at a magnetic field of 800 A / m, iron loss W _17/50 value at 1.7 T, 50 Hz, bending adhesion of the coating, and uniformity of coating appearance. . The bending adhesion of the film was evaluated by the minimum diameter at which the test piece was wound around a round bar having various diameters at intervals of 5 mm, and no peeling of the film occurred. In addition, the C content, oxygen basis weight, and pickling loss of the steel sheet after the primary recrystallization were also analyzed. These results are also shown in Table 2.
[0033]
According to Table 2, in No. 7 in which the siliconized layer is excessive, the oxygen basis weight is insufficient, and as a result, the magnetic characteristics and the film characteristics are inferior. In No. 8, where the siliconized layer is too small, the pickling loss is high, and the magnetic properties and the film properties are inferior. In No. 9 and No. 10 where P (H ₂ O) / P (H ₂ ) in the soaking process exceeded 0.70, the pickling loss was remarkably high, and the magnetic characteristics and film characteristics were inferior. In addition, No.11 and No.12 in which P (H ₂ O) / P (H ₂ ) in the heating process was not lower than that in the soaking process had insufficient decarburization and oxygen basis weight, In addition, the magnetic properties and film properties are inferior. On the other hand, No. 1 to No. 6 according to the present invention have good levels of decarburization, oxygen basis weight, and pickling weight loss, and are excellent in both magnetic properties and film properties of the product.
[0034]
[Table 2]

[0035]
<Example 2>
Directional silicon containing C: 0.073 wt%, Si: 3.30 wt%, Mn: 0.075 wt%, Se: 0.024 wt%, sol.Al: 0.024 wt%, N: 0.008 wt% and Sb: 0.025 wt% After hot rolling the steel slab to a thickness of 2.7 mm, hot-rolled sheet annealing is performed at 1000 ° C, followed by intermediate annealing at 1120 ° C in wet hydrogen and subsequent pickling for the purpose of removing the external scale 2 A final cold-rolled sheet thickness of 0.35 mm was obtained by cold rolling. At this time, the atmospheric oxidation property of the intermediate annealing was controlled to the values shown in Table 3. These cold-rolled sheets were degreased with alkali to clean their surfaces, and then subjected to primary recrystallization annealing at 840 ° C. for 150 seconds in a wet hydrogen atmosphere. At this time, the atmospheric oxidation properties of the temperature raising process and the soaking process were independently controlled to the values shown in Table 3. Next, an MgO annealing separator containing 5% TiO ₂ was applied as a slurry, dried, and then subjected to secondary recrystallization and purification annealing at 1200 ° C. for 10 hours in an H ₂ atmosphere. Thereafter, a coating mainly composed of magnesium phosphate and colloidal silica was applied. Table 3 shows the results of the same investigation as in Example 1 for the product thus obtained.
[0036]
According to Table 3, the intermediate annealing atmosphere _{P (H 2 O) / P} (H 2) is less than 0.20 No.7, and _{P (H 2 O) / P} (H 2) is greater than 1.00 In No. 8, the oxygen basis weight is insufficient, and as a result, the magnetic properties and the film properties are inferior. In No. 9 and No. 10 where P (H ₂ O) / P (H ₂ ) in the soaking process exceeded 0.70, the pickling loss was remarkably high, and the magnetic characteristics and film characteristics were inferior. In addition, No.11 and No.12 in which P (H ₂ O) / P (H ₂ ) in the heating process was not lower than that in the soaking process had insufficient decarburization and oxygen basis weight, In addition, the magnetic properties and film properties are inferior. On the other hand, No. 1 to No. 6 according to the present invention have good levels of decarburization, oxygen basis weight, and pickling weight loss, and are excellent in both magnetic properties and film properties of the product.
[0037]
[Table 3]

[0038]
<Example 3>
After hot rolling a directional silicon steel slab containing C: 0.042 wt%, Si: 3.32 wt%, Mn: 0.073 wt%, Se: 0.023 wt% and Sb: 0.026 wt% to a thickness of 2.0 mm, Final cold-rolled sheet thickness of 0.23mm by hot rolling at 950 ° C followed by two cold rollings with intermediate annealing at 970 ° C in wet hydrogen followed by pickling to remove external scale It was. At this time, the atmospheric oxidation property of the intermediate annealing was controlled to the values shown in Table 4. These cold-rolled sheets were degreased with alkali to clean their surfaces, and then subjected to primary recrystallization annealing at 820 ° C. for 120 seconds in a wet hydrogen atmosphere. At this time, the atmospheric oxidizability in the temperature raising process and the soaking process was independently controlled to the values shown in Table 4. Next, a MgO annealing separator containing 1% TiO ₂ and 2% SrSO ₄ was applied as a slurry, dried, and then subjected to secondary recrystallization and purification annealing at 1150 ° C. for 8 hours in an H ₂ atmosphere. . Thereafter, a coating mainly composed of magnesium phosphate and colloidal silica was applied. Table 4 shows the results of the same investigation as in Example 1 for the product thus obtained.
[0039]
According to Table 4, the intermediate annealing atmosphere _{P (H 2 O) / P} (H 2) is less than 0.20 No.5, and _{P (H 2 O) / P} (H 2) is greater than 1.00 In No. 6, the oxygen basis weight is insufficient, and as a result, the magnetic properties and the film properties are inferior. In No. 7 where P (H ₂ O) / P (H ₂ ) in the soaking process exceeded 0.70, the pickling loss was remarkably high, and the magnetic properties and film properties were inferior. In No. 8, where P (H ₂ O) / P (H ₂ ) in the heating process was not lower than that in the soaking process, decarburization and oxygen basis weight were insufficient, and the magnetic properties Also, the film properties are inferior. On the other hand, No. 1 to No. 4 as examples of the present invention have good levels of decarburization, oxygen basis weight, and pickling loss, and are excellent in both magnetic properties and film properties of the product.
[0040]
[Table 4]

[0041]
【The invention's effect】
According to the present invention, it is possible to stably produce a grain-oriented silicon steel sheet having excellent coating properties and good magnetic properties.
[Brief description of the drawings]
FIG. 1 is a graph showing a desiliconized layer profile in a state of a final cold-rolled sheet.
FIG. 2 is an equilibrium diagram of a product oxide in wet hydrogen of 3 wt% silicon steel.
FIG. 3 is a graph showing a desiliconized layer profile in a state of a final cold-rolled sheet when P (H ₂ O) / P (H ₂ ) in an intermediate annealing atmosphere is changed.
4 is a graph showing a desiliconized layer profile of a sample subjected to Example 1 in a state of a final cold-rolled sheet. FIG.

Claims (2)

After the directional silicon steel slab was hot-rolled, intermediate omit provide Reinforced hot-rolled sheet annealing emergence once or row to cold rolling twice or more sandwiching the intermediate annealing, or the hot-rolled sheet annealing Cold rolling is performed at least twice with annealing, followed by decarburization annealing to form a subscale on the steel sheet surface, and after applying an annealing separator mainly composed of MgO, final finishing annealing is then performed. In the method of manufacturing a grain-oriented silicon steel sheet comprising a series of steps for forming a forsterite film on the surface,
By controlling the ratio of steam partial pressure to hydrogen partial pressure in the atmosphere of the hot-rolled sheet annealing and / or intermediate annealing, the steel sheet surface before decarburization annealing to form a de-珪層, if necessary, the final cold By pickling and / or grinding before rolling, the ratio of Si concentration to the Si concentration at the center of the thickness of the desiliconized layer is determined in the region from the steel sheet surface to the thickness direction of 1 μm in the final cold-rolled sheet state. Adjusting the region where the Si concentration ratio is 0.98 or less from the surface to 5 μm in the thickness direction, and the decarburization annealing, the ratio of the water vapor partial pressure to the hydrogen partial pressure in the soaking process is less than 0.70, and method for producing tropism silicon steel sheet towards you and performs the ratio of steam partial pressure to hydrogen partial pressure in the temperature rising process at a lower value than the soaking process. De珪層, during annealing is subjected prior to decarburization annealing, and forming by controlling the ratio of water vapor partial pressure in the range of 0.20 to 1.00 with respect to hydrogen partial pressure, towards the claim 1, wherein A method for producing a directional silicon steel sheet.

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