JP3951369B2 - Manufacturing method of unidirectional electrical steel sheet - Google Patents

Description

【００１５】
かかる製造工程を施す際、熱延焼鈍温度を700 ℃〜1150℃、冷間圧延温度を常温〜350 ℃、脱炭焼鈍温度750 ℃〜900 ℃の範囲で種々に変化させた。脱炭焼鈍後、試料の一部を採取し、組織観察と集合組織の測定とを行った。また、最終仕上げ焼鈍後は未反応の焼鈍分離剤を除去し、コロイダルシリカを含有するリン酸マグネシウムを主成分とする絶縁コーテイングを塗布し800 ℃で焼き付けて製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度Ｂ₈ を測定した。
【００１６】
脱炭焼鈍後の集合組織は、試料の表面から板厚方向に１／５厚だけ化学研磨した位置で、Ｘ線極点図により測定した。また、極点図の測定データから３次元集合組織を計算により求めた。集合組織の解析にあたっては、｛１１０｝〈００１〉方位，｛１１１｝〈１１２〉方位及び｛１００｝〈０１１〉方位を含むＴＤ方向（板幅方向）回りの回転系列（Bunge 表示のオイラー角でφ₁ ＝90°、φ₂ ＝45°) にまず着目した。着目した理由は、どの試料においても、φ₁ ＝90°、φ₂ ＝45°上に極大値が存在するからである。
【００１７】
図１に例として、鋼スラブとしてａを用い、熱延板焼鈍温度が850 ℃、冷間圧延温度が150 ℃、脱炭焼鈍温度が825 ℃の場合の集合組織について、φ₁ ＝90°、φ₂ ＝45°でΦが変化したときのランダム強度比を示した。なおΦ≧０°とΦ≦０°では対称になるので、ここでは０≦Φ≦90°の範囲を図示した。
図１の場合、極大値を与えるΦは60.1°である。この値は｛１１１｝〈１１２〉( Φ＝54.7°) よりは５°以上大きく、｛１１０｝〈００１〉と〈１１０〉軸回り29.9°の回転関係であることから、｛１１０｝〈００１〉とΣ９対応関係にある範囲から外れている。しかし、その製品はＢ₈ にして1.88T の比較的良好な磁性を示した。そこで、実験した全ての試料について、脱炭焼鈍後の集合組織のφ₁ ＝90°、φ₂ ＝45°上で極大を与える｜Φ｜の値と、製品の磁束密度Ｂ₈ との関係を調査し、図２に示した。図２から、｛１１０｝〈００１〉とΣ９対応関係の範囲であるΦ：46.1〜 56.1 °に極大値が存在した場合は全て、製品の磁束密度はＢ₈ にして1.7 T 以下で劣っているという、従来知見から予測される結果とは異なる結果が得られた。また、極大を与える｜Φ｜の値は大きすぎても製品の磁性不良をもたらす。良好な磁性を得るには、極大を与える｜Φ｜の値が、58°以上62°以下であることが必要条件であることがわかった。
【００１８】
しかし、極大を与える｜Φ｜の値が、58°以上62°以下であっても、製品の磁束密度が1.8 以下になる場合もある。その原因を解明するために、集合組織解析の２つ目の着目点として、副方位の強度を調査した。
脱炭焼鈍後の集合組織において、二番目に強い強度をもつ方位は、｛12４１｝〈０１４〉近傍の方位であった。そこで、｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度の関係を調査した。図３には、φ₁ ＝90°、φ₂ ＝45°上で極大を与える｜Φ｜の値が、58°以上62°以下であった試料に関して、｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度Ｂ₈ の関係を示した。｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上の場合に製品のＢ₈ は1.85T 以上となった。ただし、｛12４１｝〈０１４〉方位のランダム強度比が8.6 と極端に高かった試料は、Ｂ₈ が1.8 T 以下となった。この試料のみ、脱炭焼鈍板における｛12４１｝〈０１４〉方位は、φ₁ ＝90°、φ₂ ＝45°上での極大方位を超えて、最大のピークになっていた。このことから、製品の磁束密度を向上させるには副方位｛12４１｝〈０１４〉方位の強度を高めることが大切であるが、最大ピークになるほどに強度が大きくなることは有害であることがわかった。
【００１９】
以上の実験結果から、スラブ加熱温度が低く、インヒビターの抑制力が弱い条件下では、最終仕上げ焼鈍時にΣ９対応粒界が移動し易いという現象は確認できなかった。しかも、
・図２でΦ＝60°前後で製品の磁性が良好であったこと、
・｛12４１｝〈０１４〉方位と｛１１０｝〈００１〉方位との角度差が約30°であり、この方位の適度な増加が製品の磁性向上に有効であること、
から、スラブ加熱温度が低い条件下では、仕上げ焼鈍時の粒成長において、Σ９対応粒界が特に移動しやすいわけではなく、30°前後の角度差をもつ粒界が移動しやすいと考えられる。
【００２０】
次に、脱炭焼鈍板の｛12４１｝〈０１４〉方位の強度が二次再結晶に及ぼす影響について考察する。｛12４１｝〈０１４〉方位も、φ₁ ＝90°、｜Φ｜＝60°、φ₂ ＝45°方位も、｛１１０｝〈００１〉方位から30°の角度差である。したがって、仕上げ焼鈍時の粒成長において、30°前後の角度差をもつ粒界が移動し易いという点のみからは、脱炭焼鈍板の地がφ₁ ＝90°、｜Φ｜＝60°、φ₂ ＝45°方位であることも、｛12４１｝〈０１４〉方位であることも｛１１０｝〈００１〉の成長に関しては同等である。しかし、実験結果からは、φ₁ ＝90°、｜Φ｜＝60°、φ₂ ＝45°方位が強いだけでは良好な二次再結晶は生じず、｛12４１｝〈０１４〉方位もある程度強くないといけない。この理由を解明すべく、脱炭焼鈍板の断面組織観察を行った。この断面組織観察には、電子線後方散乱図形、以下ＥＢＳＰ（Electron Back Scattering diffraction Patteen) を用いた。ＥＢＳＰでは、0.1 μm 以下の空間分解能で結晶方位が測定できる。また、一点の測定に１秒程度しか要しない。更に、結晶粒径よりも十分小さいピッチで二次元試料面上を自動測定し、結晶方位が変化するところを粒界とみなし、測定した領域をマッピングすることができる。そしてマッピングした領域について、粒径分布、平均粒径など解析可能である。ここでは、粒径分布を求める目的でＥＢＳＰを利用した。
【００２１】
図４に脱炭焼鈍板の｛12４１｝〈０１４〉方位のランダム強度比と粒径の変動係数との関係を示す。ここでは、図３同様、φ₁ ＝90°、φ₂ ＝45°上で極大を与える｜Φ｜の値が、58°以上62°以下であった試料について調査した。図４より、｛12４１｝〈０１４〉方位の増加に伴い、変動係数が大きくなって、非整粒になっていくが、｛12４１｝〈０１４〉方位が最大ピークになるまで増加すると再び粒径がそろってくることがわかる。そして、製品の磁束密度が高くなるのは変動係数が大きい条件下であるという、従来知見とは異なる結果が得られた。
【００２２】
以上から、｛12４１｝〈０１４〉方位の適度な増加は、粒径を不均一にし、良好な二次再結晶につながることがわかった。脱炭焼鈍板の粒径が不均一であることは、スラブ加熱温度が高い場合や、途中窒化を施す場合、すなわち、インヒビターの抑制力が強い場合には有害であると、これまで報告されてきたが、この発明のように、インヒビター抑制力が弱い場合には、組織の不均一性がインヒビション効果を補う働きをするのではないかと考えられる。
【００２３】
以上の実験から、この発明においては、普通鋼並に低いスラブ加熱温度範囲において、熱延板焼鈍温度および冷間圧延温度を調整することにより、脱炭焼鈍後の板の板厚１／５層で測定した集合組織が、下記の条件を満たすように制御することとしたのである。
記
集合組織の最大ピーク方位が、Bunge のオイラー角表示で
φ₁ ＝90°、Φ:58 〜62°又は−58〜−62°、φ₂ ＝45°
の範囲内に存在し、かつ、
｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上。
【００２４】
なお、集合組織を板厚１／５層で評価する理由は、最終仕上げ焼鈍時に｛１１０｝〈００１〉方位の二次再結晶が板厚１／５層付近を起点に発生しやすく、二次再結晶前のこの部分の集合組織が特に重要であるからである。
上記のように、脱炭焼鈍板の集合組織を制御することが必要なのであるが、そのためには、以下に示す条件に従う必要がある。
【００２５】
（成分について）
Ｃ：0.02wt％以上、0.07wt％以下；
Ｃは、組織を改善し、二次再結晶を安定化させるために必要な成分で、そのために0.02wt％以上が必要である。しかし、0.07wt％を超えると冷延時の破断が増加すること、また、脱炭焼鈍後の組織が均一になり過ぎて、この発明には適さないことから、0.07wt％以下とする。
【００２６】
Si：2.0 wt％以上、4.5 wt％以下；
Siは電気抵抗を増加させ鉄損を低減させるために必須の成分であり、このためには2.0 wt％以上含有させることが必要であるが、4.5 wt％を超えると加工性が劣化し、製造や製品の加工が極めて困難になるので、2.0 wt％以上4.5 wt％以下の範囲とする。
【００２７】
Mn：0.03wt％以上、2.5 wt％以下；
MnもSiと同じく電気抵抗を高める成分であり、また製造時の熱間加工性を向上させるので必要な成分である。この目的のためには、0.03wt％以上の含有が必要であるが、2.5 wt％を超えて含有した場合、γ変態を誘起して磁気特性が劣化するので、0.03wt％以上、2.5 wt％以下の範囲とする。
【００２８】
Al：0.005 wt％以上、0.030 wt％以下；
Alはインヒビター成分として、0.005 wt％以上、0.030 wt％以下で含有させることが必要である。すなわち、AlはＮと結びついてAlN としてインヒビターの役割を果たし、特にAlN をスラブ加熱時に固溶させ、熱延板焼鈍の昇温過程で微細析出させることにより、一次再結晶粒の成長抑制効果が高まる。しかし、Alの含有量が0.005 wt％未満の場合、熱延板焼鈍の昇温過程において析出するAlN の量が不足し、逆に0.030 wt％を超える場合も、1260℃以下でのスラブ加熱の際にAlN の固溶が困難となるために熱延板焼鈍の昇温過程において微細に析出するAlN の量が不足する。したがって、インヒビターとしての効果を有効に発揮させるために、Alの含有量は0.005 wt％以上、0.030 wt％以下とする。
【００２９】
Ｎ：0.0030wt％以上、0.0100wt％以下；
ＮはAlN を形成し、Alと共にインヒビターとして機能するので0.0030wt％以上含有させることが必要である。しかしながら、0.0100wt％を超えて含有すると鋼中でガス化し、フクレなどの欠陥をもたらすので、0.0030wt％以上、0.0100wt％以下の範囲にしなければならない。
【００３０】
その他のインヒビター；
Sb, Nb, Sn, Cr, Se, Ｓ等を必要に応じて添加し、インヒビターとして機能させることもできる。特にSbもしくはSnは、熱間圧延において微細な析出物を形成し、次工程の熱延板焼鈍の昇温過程におけるAlN の析出核を増加させる作用を有するので有効である。かかる作用を得るためにはこれらの成分を0.001 wt％以上添加することが必要であるが、0.30wt％を超えると製品のベンド特性など機械的特性が劣化するので、その含有量は0.001 wt％以上、0.3 wt％以下とするのが好ましい。
【００３１】
(熱間圧延)
以上の成分に調整されたスラブは、通常の方法に従い、スラブ加熱に供された後、熱間圧延により熱間コイルとされる。
スラブ加熱温度は1260℃以下とする。スラブ加熱温度が低いことは、エネルギーコスト低減のために特に好ましいだけでなく、AlN 等のインヒビター成分の析出状態に適度な不均一性を生じさせ、脱炭焼鈍後の粒径分布の不均一性を助長するという点で好ましい。
なお、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示されているが、この方法は、スラブ加熱温度を低くとれるので、この発明においても好適に実施し得る。
【００３２】
(熱延板焼鈍)
熱延板焼鈍は950 ℃以下で行うことが好ましい。熱延板焼鈍の目的は、熱延板の組織を均一化することとインヒビターの微細析出を促すことにあるので、一般には1000℃以上の高温で行われるが、この発明では組織の均一化は必要なく、むしろ有害であるため、極めて低温で行うこととする。もっとも、インヒビターを微細析出させることは必要であるから、熱延板焼鈍を省略したり、800 ℃未満で行うことは好ましくない。
【００３３】
（冷間圧延）
冷間圧延はタンデム圧延機で100 ℃以上の温度で行うことが好ましい。タンデム圧延は歪速度が大きく、パス間時間が短いので、かかるタンデム圧延機で100 ℃以上の温度で温間圧延を施すと、不均一変形が促進される。圧延時の不均一変形は、脱炭焼鈍時の一次再結晶粒の成長の不均一性を助長する。脱炭焼鈍板の粒径の不均一性は｛12４１｝〈０１４〉方位の適度な増加に対応し、製品の磁気特性向上に結びつくので好ましい。
【００３４】
（最終仕上げ焼鈍、コーティング）
冷間圧延後、脱炭焼鈍を常法に従い施した後、焼鈍分離剤を塗布し、最終仕上げ焼鈍を施す。最終仕上げ焼鈍後は、必要に応じて絶縁コーティングを塗布焼き付け、更に平坦化焼鈍を施し、製品とする。
【００３５】
【実施例】
〔実施例１〕
表１に示すｅ、ｆの成分組成になる200 mm厚の鋼スラブ各９本を1150℃の温度に加熱後、熱間圧延して2.4 mmの熱延コイルとした。これらのコイルは、60秒間の熱延板焼鈍を施し、酸洗した後、タンデム圧延機で0.34mmの厚みに冷間圧延した。この際、表２に示すように熱延板焼鈍温度を850 ℃、940 ℃、1030℃の３通り、冷間圧延温度を60℃、120 ℃、200 ℃の３通りに変化させた。その後、脱脂処理を行い、830 ℃で120 秒間の脱炭焼鈍を施した後、焼鈍分離剤を塗布して最終仕上げ焼鈍を施した。
脱炭焼鈍後、試料の一部を採取し、板厚１／５層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
【００３６】
最終仕上げ焼鈍後、未反応の焼鈍分離剤を除去し、コロイダリシリカを含有するリン酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付け製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度Ｂ₈ とＷ_17/50 （磁束密度1.7 T における鉄損）を測定した。
表２に、脱炭焼鈍板の集合組織と製品の磁気特性を示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°上で極大を与える｜Φ｜の値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料は、備考欄に※印を付与した。他の試料はφ₁ ＝90°、φ₂ ＝45°上に最大ピークが存在した。
表２に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−58〜−62°、φ₂ ＝45°の範囲内に存在し、かつ｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱延板焼鈍を950 ℃以下の温度で行い、冷間圧延をタンデム圧延機で100 ℃以上の温度で行う条件を遵守することが極めて有効であることがわかる。
【００３７】
【表２】

【００３８】
〔実施例２〕
表１に示すｇ、ｈの成分組成になる250 mm厚の鋼スラブ各９本を1220℃の温度に加熱後、熱間圧延して2.7 mmの熱延コイルとした。これらのコイルは、60秒間の熱延板焼鈍を施し、酸洗した後、80℃の温度で1.6 mmの厚みまでの第１回目のタンデム圧延機による冷間圧延を施し、950 ℃の温度で中間焼鈍を施した後、酸洗し、0.22mmの厚みまでの第２回目のタンデム圧延機による冷間圧延を施した。この際、表３に示すように熱延板焼鈍温度を800 ℃、900 ℃、1000℃の３通り、２回目の冷間圧延温度を80℃、150 ℃、250 ℃の３通りに変化させた。その後、脱脂処理を行い、850 ℃で120 秒間の脱炭焼鈍を施した後、焼鈍分離剤を塗布して最終仕上げ焼鈍を施した。
脱炭焼鈍後、試料の一部を採取し、板厚１／５層の集合組織の測定を行った。集合組織は、Ｘ線極点図により測定し、測定データから３次元集合組織を計算により求めた。
【００３９】
最終仕上げ焼鈍後、未反応の焼鈍分離剤を除去し、コロイダリシリカを含有するリン酸マグネシウムを主成分とする絶縁コーティングを塗布し、800 ℃で焼き付けて製品とした。各製品から、圧延方向に沿ってエプスタインサイズの試験片を切り出し、磁束密度Ｂ₈ とＷ_17/50 （磁束密度1.7 T における鉄損）を測定した。
【００４０】
表３に、脱炭焼鈍後の集合組織と製品の磁気特性を示す。集合組織については、φ₁ ＝90°、φ₂ ＝45°上で極大を与える｜Φ｜の値と、｛12４１｝〈０１４〉方位のランダム強度比を示した。なお、｛12４１｝〈０１４〉方位が最大ピークとなった試料は、備考欄に※印を付与した。他の試料はφ₁ ＝90°、φ₂ ＝45°上に最大ピークが存在した。
表３に示されるように、脱炭焼鈍板の集合組織の最大ピークが、Bunge のオイラー角表示でφ₁ ＝90°、Φ：58〜62°又は−68〜−62°、φ₂ ＝45°の範囲内に存在し、かつ｛12４１｝〈０１４〉方位のランダム強度比が3.0 以上である場合に、製品の磁気特性が良好となった。また、脱炭焼鈍板の集合組織を上記のごとく制御するためには、熱延板焼鈍を950 ℃以下の温度で行い、冷間圧延をタンデム圧延機で100 ℃以上の温度で行う条件を遵守することが極めて有効であることがわかる。
【００４１】
【表３】

【００４２】
【発明の効果】
この発明により、磁気特性を良好に保った汎用一方向性電磁鋼板を安定して製造することが可能になった。
【図面の簡単な説明】
【図１】脱炭焼鈍版の集合組織のφ₁ ＝90°、φ₂ ＝45°断面においてΦが変化したときのランダム強度比を示す図である。
【図２】φ₁ ＝90°、φ₂ ＝45°断面上で極大を与える｜Φ｜の値と、製品の磁束密度Ｂ₈ との関係を示す図である。
【図３】｛12４１｝〈０１４〉方位のランダム強度比と製品の磁束密度Ｂ₈ の関係を示す図である。
【図４】脱炭焼鈍板の｛12４１｝〈０１４〉方位のランダム強度比と粒径の変動係数との関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a unidirectional electrical steel sheet, and more particularly to a method for stably producing a general-purpose unidirectional electrical steel sheet having good magnetic properties.
[0002]
[Prior art]
Unidirectional electrical steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and it is basically important that they have excellent magnetic properties such as magnetic flux density and iron loss value. Therefore, a slab having a thickness of 100 to 300 mm is hot-rolled after high-temperature heating, and then this hot-rolled sheet is made into a final sheet thickness by one or more cold rollings sandwiching intermediate annealing, and after decarburization annealing, It is manufactured through a complicated process of applying an annealing separator and then performing a final finish annealing for the purpose of secondary recrystallization and purification. In order to enhance the magnetic properties of such a unidirectional electrical steel sheet, the <001> axis, which is the easy axis of magnetization, is aligned in the rolling direction by secondary recrystallization in the finish annealing process during the manufacturing process {110} It is important to grow crystal grains with <001> orientation (so-called Goth orientation).
[0003]
In order to effectively promote secondary recrystallization such that such {110} <001> oriented crystal grains accumulate, the following three points are important.
The first is to disperse a dispersed phase called an inhibitor that suppresses the growth of primary recrystallized grains to a uniform and appropriate size, and the second is to properly control the grain size distribution after primary recrystallization. The third is proper control of the primary recrystallization texture. With these goals as a goal, research and development are underway to improve the magnetic properties of unidirectional electrical steel sheets.
[0004]
First, when we talk about dispersing a dispersed phase called an inhibitor that suppresses the growth of primary recrystallized grains to a uniform and appropriate size, the inhibitor suppresses the growth of primary recrystallized grains during final finish annealing. Thus, only the grains having the {110} <001> orientation, which has the highest superiority of grain growth, engulf grains of other orientations and grow large. Therefore, the inhibitory force of the inhibitor must be controlled to such a strength that only the grains of {110} <001> orientation can grow and the growth of other grains can be stopped.
[0005]
Typical examples of such inhibitors are sulfides such as MnS, MnSe, AlN and VN, selenium compounds and nitrides, and those having extremely low solubility in steel are used. In order to exert the action as an inhibitor, in the manufacturing process, a method has been adopted in which the inhibitor is once completely dissolved in the slab before the hot rolling and then finely precipitated in the subsequent process. The slab heating temperature for sufficiently dissolving this inhibitor is about 1400 ° C, which is about 200 ° C higher than the slab heating temperature of ordinary steel. Such high temperature slab heating has the following drawbacks.
1) High energy intensity due to high temperature heating.
2) Melt scale is likely to occur and slab sag is likely to occur.
3) Over decarburization of the slab surface occurs.
4) In order to solve the problems 2) and 3), an induction furnace dedicated to unidirectional electrical steel was devised, but the problem of increased energy costs remained.
[0006]
Many studies have been made to achieve low temperature slab heating of unidirectional electrical steel to overcome the above drawbacks. A decrease in the slab heating temperature inevitably leads to a decrease in the inhibitory ability of the inhibitor because it results in an insufficient amount of solid solution of the inhibitor component. Therefore, an intermediate nitriding technique has been developed as a technique to compensate for the decrease in the suppression force caused by low-temperature slab heating in a later process. As this nitriding technique, for example, Japanese Patent Laid-Open No. 57-207114 discloses a technique of nitriding at the time of decarburization annealing, and Japanese Patent Laid-Open No. 62-70521 specifies finish annealing conditions, and nitriding in the middle of finishing annealing. Thus, a technique enabling low temperature slab heating has been disclosed. Furthermore, Japanese Patent Application Laid-Open No. 62-40315 discloses a method of containing an amount of AlN that cannot be dissolved during slab heating and controlling the inhibitor to an appropriate state by nitriding in the middle.
However, among the above-described intermediate nitriding techniques, the method of performing nitridation before entering the final annealing requires new equipment, and there is a problem that the cost increases, and the nitriding during the final annealing is controlled. The problem remains that is difficult.
[0007]
Next, a description will be given of appropriately controlling the crystal grain size distribution after the primary recrystallization. Studies have been conducted on the crystal grain size of the primary recrystallization structure from the viewpoint of controlling the driving force of secondary recrystallization. For example, in JP-A-2-182866, the primary recrystallized grains have a primary recrystallized structure having an average diameter of 15 μm or more and a coefficient of variation (standard deviation of particle size distribution normalized by the average diameter) of 0.6 or less. It was disclosed that it was important. In JP-A-4-337029, the amount of N in the steel in the annealing process before the final cold rolling is detected, and the primary recrystallized grains in the range of 15 to 25 μm are obtained based on the result. A technique for changing the set temperature of crystal annealing has been disclosed. Furthermore, in JP-A-6-33141, the primary recrystallized grains after decarburization annealing have an average diameter of 6 to 11 μm and a coefficient of variation of 0.5 or less, and the primary recrystallization immediately before the start of secondary recrystallization of final finish annealing. A technique for increasing the average diameter of recrystallized grains by 5 to 30% has been disclosed. As in these publications, there are various theories on the optimal primary recrystallization grain size. In order to produce appropriate secondary recrystallization, it is important to finely control the balance between the driving force of grain growth and the inhibitory power of the inhibitor that suppresses it. When the inhibitor's inhibitory force changes due to the above, the optimal driving force, that is, the optimal primary recrystallized grain size also changes. However, the fact that a smaller coefficient of variation is better is a consistent view of previous technologies. As a technique for controlling both inhibitor inhibitory force and driving force for grain growth, Japanese Patent Laid-Open No. 4-297524 discloses that the average grain size of primary recrystallized grains is 18 to 35 μm, and after hot rolling until the start of secondary recrystallization. Discloses a technique for performing a nitriding treatment.
[0008]
Next, the third, proper control of the primary recrystallization texture will be described. In order to further enhance the superiority of grain growth in the {110} <001> orientation during the final finish annealing, the ground orientation is strongly accumulated in the {111} <112> orientation, and secondary recrystallization is included therein. It has been considered important to have a {110} <001> orientation with a high degree of sharpness, which is the core of.
This concept is based on the theory that grain boundaries in a Σ9 correspondence are easy to move. Strictly speaking, the Σ9 correspondence relationship means that the grains on both sides of the grain boundary are in a rotational relationship of 38.9 degrees around the <110> axis, but in general, in the range where the rotation angle is 38.9 ± 5.0 degrees, Σ9 It can be regarded as a correspondence (Brandon condition). Here, the {110} <001> orientation and the {111} <112> orientation have a rotational relationship of 35.3 ° C. around the <110> axis, and are within a range that can be regarded as a correspondence relationship of Σ9. Therefore, in the primary recrystallized texture, a state in which {110} <001> oriented grains with high sharpness are scattered in the ground that is strongly accumulated in the {111} <112> orientation is {110} <112 It has been considered advantageous for secondary recrystallization of the 001> orientation.
[0009]
[Problems to be solved by the invention]
In summary, in the prior art, in order to generate secondary recrystallized grains highly accumulated in the {110} <001> orientation,
(B) A strong inhibitor suppressing power is required, and for that purpose, the slab heating temperature should be raised to about 1400 ° C, or nitridation in the middle is required.
(B) The primary recrystallized structure needs to be controlled in a state where the variation in particle size is small, that is, in a sized state,
(C) The primary recrystallization texture should be controlled so that the orientation of the ground is strongly accumulated in {111} <112>, and {110} <001> with high sharpness is scattered therein. ,
These three points have been considered important. However, as described above, when the slab heating temperature is increased, a problem may be caused in terms of quality, which is disadvantageous in terms of cost. The intermediate nitriding method also has a problem in terms of cost and controllability, and it has been difficult to achieve both good magnetic properties of the product and reduction in manufacturing cost. The primary recrystallized structure that has been considered desirable in the past has not solved the problem of achieving both good magnetic properties and cost reduction.
[0010]
The problem to be solved by the present invention is that, in the manufacture of general-purpose unidirectional electrical steel sheets that require cost reduction, the slab heating temperature is as low as that of ordinary steel, and the unidirectional electromagnetic characteristics are kept good. It is the development of an advantageous manufacturing method for steel sheets. In particular, the objective is to produce a unidirectional electrical steel sheet with stable magnetic properties without aggressive nitriding.
[0011]
[Means for Solving the Problems]
  Researchers of this invention have made slab heating temperature as low as that of ordinary steel and have good magnetic properties in the manufacture of general-purpose unidirectional electrical steel sheets that require cost reduction after extensive research. A new method has been found for producing grain-oriented electrical steel sheets without active nitriding.
  That is, the present invention relates to silicon containing C: 0.02 to 0.07 wt%, Si: 2.0 to 4.5 wt%, Mn: 0.03 to 2.5 wt%, Al: 0.005 to 0.030 wt%, and N: 0.003 to 0.010 wt%. Steel slab,After heating, hot-rolled, and then subjected to hot-rolled sheet annealing, followed by cold rolling at least once with intermediate or intermediate annealing to the final sheet thickness, followed by decarburization annealing and then applying an annealing separator In the method of manufacturing a unidirectional electrical steel sheet that is then subjected to finish annealing,
  Slab heating temperature 1260 By adjusting the hot-rolled sheet annealing temperature and adjusting the rolling temperature as tandem rolling, while adjusting the rolling temperature,It is the manufacturing method of the unidirectional electrical steel sheet characterized by making the texture in the plate | board thickness 1/5 layer area | region of a board after decarburization annealing into the structure | tissue which satisfies the following conditions.
                      Record
The maximum peak direction of the texture is determined by Bunge's Euler angle method.
  φ₁ = 90 °, Φ: 58 to 62 ° or −58 to −62 °, φ₂ = 45 °
Within the scope of
Random intensity ratio of {1241} <014> orientation is 3.0 or more.
  In particularIn the invention, hot-rolled sheet annealing is performed at a temperature of 950 ° C. or lower,AndBy performing cold rolling at 100 ° C. or higher with a tandem rolling mill, it is possible to produce a unidirectional electrical steel sheet with more stable and good magnetic properties.
  The Euler angle is described in “Aggregate Texture” (written by Keiichi Nagashima; published on January 20, 1984, published by Maruzen Co., Ltd.) p.7-9. See pages 35-36 of the same book.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The experiment that led to the above invention will be described below, and the embodiment of the present invention will be described in detail.
In the prior art, the primary recrystallized structure is sized (under (b) described above) and the primary recrystallized texture is changed to {111} under the condition that the inhibitor has a very strong inhibitory force as described in (a) above. There have been many reports that it is effective to strongly accumulate <112> (the above-mentioned (c)). However, the inventors have conducted intensive research based on the idea that (b) (c) is not necessarily effective under conditions where the inhibitor is weak.
[0013]
(Experiment 1)
Ten steel slabs each having a thickness of 220 mm and having a composition of a to d shown in Table 1 were heated to a temperature of 1200 ° C. and then hot rolled to form a 2.5 mm hot rolled coil. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm with a tandem rolling mill. Thereafter, degreasing treatment was performed, and decarburization annealing was performed for 120 seconds in a wet hydrogen atmosphere, and then an annealing separator was applied to perform final finish annealing.
[0014]
[Table 1]

[0015]
When performing this manufacturing process, the hot rolling annealing temperature was varied in the range of 700 ° C. to 1150 ° C., the cold rolling temperature was from room temperature to 350 ° C., and the decarburization annealing temperature was 750 ° C. to 900 ° C. After decarburization annealing, a part of the sample was collected, and the structure was observed and the texture was measured. In addition, after the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product. From each product, an Epstein-sized test piece is cut out along the rolling direction, and the magnetic flux density B₈Was measured.
[0016]
The texture after decarburization annealing was measured by an X-ray pole figure at a position where the surface was chemically polished by 1/5 thickness from the surface of the sample. In addition, a three-dimensional texture was calculated from the measurement data of the pole figure. In the analysis of the texture, the rotation sequence around the TD direction (plate width direction) including the {110} <001> orientation, the {111} <112> orientation and the {100} <011> orientation (Bunge's Euler angle) φ₁= 90 °, φ₂= 45 °). The reason for focusing on₁= 90 °, φ₂This is because there is a local maximum above 45 °.
[0017]
As an example in FIG. 1, for a texture when a is used as a steel slab, the hot-rolled sheet annealing temperature is 850 ° C, the cold rolling temperature is 150 ° C, and the decarburization annealing temperature is 825 ° C.₁= 90 °, φ₂= Random intensity ratio when Φ changed at 45 °. Since Φ ≧ 0 ° and Φ ≦ 0 ° are symmetric, the range of 0 ≦ Φ ≦ 90 ° is illustrated here.
In the case of FIG. 1, Φ giving the maximum value is 60.1 °. This value is 5 ° or more larger than {111} <112> (Φ = 54.7 °), and has a rotational relationship of 29.9 ° around the {110} <001> and <110> axes, so {110} <001> Is out of the range corresponding to Σ9. However, the product is B₈It showed relatively good magnetism of 1.88T. Therefore, for all samples tested, the texture φ after decarburization annealing₁= 90 °, φ₂= Maximum value above 45 ° | | Φ | value and magnetic flux density B of product₈The relationship between and is shown in FIG. From FIG. 2, in all cases where there is a maximum value in the range of {110} <001> and Σ9, Φ: 46.1 to 56.1 °, the magnetic flux density of the product is B₈As a result, it was inferior at 1.7 T or less, and a result different from the result predicted from the conventional knowledge was obtained. Further, even if the value of | Φ | that gives the maximum is too large, it causes a magnetic defect of the product. In order to obtain good magnetism, it has been found that the value of | Φ | that gives the maximum is 58 ° or more and 62 ° or less.
[0018]
However, even if the value of | Φ | that gives the maximum is 58 ° or more and 62 ° or less, the magnetic flux density of the product may be 1.8 or less. In order to elucidate the cause, the strength of the sub-azimuth was investigated as the second point of interest in the texture analysis.
In the texture after decarburization annealing, the orientation having the second strongest strength was the orientation in the vicinity of {1241} <014>. Therefore, the relationship between the random intensity ratio in the {1241} <014> orientation and the magnetic flux density of the product was investigated. In FIG.₁= 90 °, φ₂= Maximum value at 45 ° || With respect to a sample whose value of | Φ | is 58 ° or more and 62 ° or less, the random intensity ratio in the {1241} <014> direction and the magnetic flux density B of the product₈Showed the relationship. If the random intensity ratio of {1241} <014> orientation is 3.0 or more, B₈Became 1.85T or more. However, the sample whose random intensity ratio in the {1241} <014> orientation was extremely high at 8.6 is B₈Became 1.8 T or less. Only in this sample, the {1241} <014> orientation in the decarburized annealing plate is φ₁= 90 °, φ₂= Beyond the maximum direction at 45 °, it was the largest peak. From this, it is important to increase the strength of the sub-azimuth {1241} <014> orientation to improve the magnetic flux density of the product, but it is detrimental to increase the strength to the maximum peak. It was.
[0019]
From the above experimental results, it was not possible to confirm the phenomenon that the Σ9-corresponding grain boundary easily moves during the final finish annealing under the condition that the slab heating temperature is low and the inhibitor suppressing force is weak. Moreover,
・ In Fig. 2, the magnetism of the product was good around Φ = 60 °.
The angular difference between the {1241} <014> orientation and the {110} <001> orientation is about 30 °, and a moderate increase in this orientation is effective in improving the magnetic properties of the product,
Therefore, under the condition where the slab heating temperature is low, it is considered that the grain boundary corresponding to Σ9 is not particularly easy to move during grain growth during finish annealing, and that the grain boundary having an angular difference of about 30 ° is likely to move.
[0020]
Next, the influence of the strength of the {1241} <014> orientation of the decarburized annealed plate on the secondary recrystallization will be considered. {1241} <014> orientation is φ₁= 90 °, | Φ | = 60 °, φ₂= 45 ° azimuth is also an angle difference of 30 ° from the {110} <001> azimuth. Therefore, the ground of the decarburized annealing plate is φ only because the grain boundaries with an angle difference of around 30 ° are easy to move in the grain growth during finish annealing.₁= 90 °, | Φ | = 60 °, φ₂= 45 ° azimuth and {1241} <014> azimuth are equivalent for the growth of {110} <001>. However, from the experimental results,₁= 90 °, | Φ | = 60 °, φ₂If the = 45 ° orientation is strong, good secondary recrystallization does not occur, and the {1241} <014> orientation must be strong to some extent. In order to elucidate the reason, the cross-sectional structure of the decarburized annealed plate was observed. For this cross-sectional structure observation, an electron beam backscattering pattern, hereinafter referred to as EBSP (Electron Back Scattering Diffraction Patteen), was used. With EBSP, crystal orientation can be measured with a spatial resolution of 0.1 μm or less. In addition, only one second is required for one point of measurement. Furthermore, it is possible to automatically measure the two-dimensional sample surface with a pitch sufficiently smaller than the crystal grain size, and to regard the place where the crystal orientation changes as the grain boundary, and to map the measured region. The mapped region can be analyzed for particle size distribution, average particle size, and the like. Here, EBSP was used for the purpose of obtaining the particle size distribution.
[0021]
FIG. 4 shows the relationship between the random strength ratio of the {1241} <014> orientation of the decarburized annealed plate and the coefficient of variation of the particle size. Here, as in FIG.₁= 90 °, φ₂= A sample having a value of | Φ | that gives a maximum above 45 ° was 58 ° or more and 62 ° or less. From FIG. 4, as the {1241} <014> orientation increases, the coefficient of variation increases and becomes non-sized, but when the {1241} <014> orientation increases to the maximum peak, the particle size is increased again. You can see that And the result which differs from the conventional knowledge that the magnetic flux density of a product becomes high under the condition where a coefficient of variation is large was obtained.
[0022]
From the above, it was found that a moderate increase in the {1241} <014> orientation makes the grain size non-uniform and leads to good secondary recrystallization. It has been reported so far that the particle size of the decarburized annealed sheet is harmful when the slab heating temperature is high or when nitriding is performed during the slab heating, that is, when the inhibitor's inhibitory power is strong. However, when the inhibitor suppressive force is weak as in the present invention, it is considered that the tissue non-uniformity may serve to supplement the inhibition effect.
[0023]
  From the above experiment, in the present invention,By adjusting the hot-rolled sheet annealing temperature and the cold rolling temperature in the slab heating temperature range as low as that of ordinary steel,The texture measured at 1/5 layer thickness of the plate after decarburization annealing is controlled to satisfy the following conditions:didIt is.
                        Record
The maximum peak orientation of the texture is displayed in Bunge's Euler angle display.
  φ₁ = 90 °, Φ: 58 to 62 ° or −58 to −62 °, φ₂ = 45 °
Within the scope of
Random intensity ratio of {1241} <014> orientation is 3.0 or more.
[0024]
The reason why the texture is evaluated with a thickness of 1/5 layer is that secondary recrystallization in the {110} <001> orientation is likely to occur starting from the vicinity of the thickness of 1/5 layer during the final finish annealing. This is because the texture of this part before recrystallization is particularly important.
As described above, it is necessary to control the texture of the decarburized and annealed plate. To that end, it is necessary to comply with the following conditions.
[0025]
(About ingredients)
C: 0.02 wt% or more, 0.07 wt% or less;
C is a component necessary for improving the structure and stabilizing the secondary recrystallization, and therefore 0.02 wt% or more is necessary. However, if it exceeds 0.07 wt%, the fracture at the time of cold rolling increases, and the structure after decarburization annealing becomes too uniform, which is not suitable for the present invention, so 0.07 wt% or less.
[0026]
Si: 2.0 wt% or more, 4.5 wt% or less;
Si is an essential component for increasing electrical resistance and reducing iron loss. For this purpose, it is necessary to contain 2.0 wt% or more, but if it exceeds 4.5 wt%, the workability deteriorates and it is manufactured. And processing of the product becomes extremely difficult, so the range is 2.0 wt% to 4.5 wt%.
[0027]
Mn: 0.03 wt% or more, 2.5 wt% or less;
Mn, like Si, is a component that increases electrical resistance, and is also a necessary component because it improves hot workability during manufacturing. For this purpose, it is necessary to contain 0.03 wt% or more. However, if it exceeds 2.5 wt%, the gamma transformation is induced and the magnetic properties deteriorate, so 0.03 wt% or more, 2.5 wt% The following range.
[0028]
Al: 0.005 wt% or more, 0.030 wt% or less;
Al must be contained as an inhibitor component in an amount of 0.005 wt% or more and 0.030 wt% or less. In other words, Al is combined with N to act as an inhibitor as AlN. In particular, AlN is dissolved during slab heating and finely precipitated during the temperature rising process of hot-rolled sheet annealing, thereby suppressing the growth of primary recrystallized grains. Rise. However, when the Al content is less than 0.005 wt%, the amount of AlN that precipitates during the temperature rising process of hot-rolled sheet annealing is insufficient, and conversely, when it exceeds 0.030 wt%, the slab heating at 1260 ° C or less At this time, since it becomes difficult to dissolve AlN, the amount of AlN finely precipitated in the temperature rising process of hot-rolled sheet annealing is insufficient. Therefore, in order to effectively exhibit the effect as an inhibitor, the Al content is set to 0.005 wt% or more and 0.030 wt% or less.
[0029]
N: 0.0030 wt% or more, 0.0100 wt% or less;
N forms AlN and functions as an inhibitor together with Al, so it is necessary to contain 0.0030 wt% or more. However, if it exceeds 0.0100 wt%, it will gasify in steel and cause defects such as blistering, so it must be in the range of 0.0030 wt% or more and 0.0100 wt% or less.
[0030]
Other inhibitors;
Sb, Nb, Sn, Cr, Se, S or the like can be added as necessary to function as an inhibitor. In particular, Sb or Sn is effective because it has the effect of forming fine precipitates in hot rolling and increasing the precipitation nuclei of AlN in the temperature rising process of the next hot-rolled sheet annealing. In order to obtain such effects, it is necessary to add these components in an amount of 0.001 wt% or more. However, if it exceeds 0.30 wt%, the mechanical properties such as the bend characteristics of the product deteriorate, so the content is 0.001 wt%. As mentioned above, it is preferable to set it as 0.3 wt% or less.
[0031]
(Hot rolling)
The slab adjusted to the above components is subjected to slab heating in accordance with a normal method, and is then formed into a hot coil by hot rolling.
Slab heating temperature shall be 1260 ℃ or less. A low slab heating temperature is not only preferable for reducing energy costs, but also causes moderate heterogeneity in the precipitation state of inhibitor components such as AlN, and non-uniformity in particle size distribution after decarburization annealing. It is preferable in that it promotes.
In recent years, a method of directly performing hot rolling after continuous casting without performing slab heating has been disclosed, but since this method can reduce the slab heating temperature, it can also be suitably implemented in the present invention.
[0032]
(Hot rolled sheet annealing)
The hot-rolled sheet annealing is preferably performed at 950 ° C or lower. The purpose of hot-rolled sheet annealing is to homogenize the structure of the hot-rolled sheet and to promote fine precipitation of the inhibitor, so it is generally performed at a high temperature of 1000 ° C or higher. Since it is unnecessary and rather harmful, it should be carried out at a very low temperature. However, since it is necessary to finely precipitate the inhibitor, it is not preferable to omit the hot-rolled sheet annealing or to perform it at less than 800 ° C.
[0033]
(Cold rolling)
Cold rolling is preferably performed at a temperature of 100 ° C. or higher with a tandem rolling mill. Tandem rolling has a high strain rate and a short time between passes. Therefore, when the tandem rolling is performed at a temperature of 100 ° C. or higher with such a tandem rolling mill, non-uniform deformation is promoted. Non-uniform deformation during rolling promotes non-uniform growth of primary recrystallized grains during decarburization annealing. The non-uniformity of the grain size of the decarburized annealed plate is preferable because it corresponds to a moderate increase in the {1241} <014> orientation and leads to an improvement in the magnetic properties of the product.
[0034]
(Final finish annealing, coating)
After cold rolling, decarburization annealing is performed according to a conventional method, and then an annealing separator is applied and final finishing annealing is performed. After the final finish annealing, if necessary, an insulating coating is applied and baked, and further flattened annealing is performed to obtain a product.
[0035]
【Example】
[Example 1]
Nine 200 mm-thick steel slabs having the component compositions e and f shown in Table 1 were heated to a temperature of 1150 ° C. and hot-rolled to form 2.4 mm hot-rolled coils. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm with a tandem rolling mill. At this time, as shown in Table 2, the hot-rolled sheet annealing temperature was changed in three ways: 850 ° C., 940 ° C., and 1030 ° C., and the cold rolling temperature was changed in three ways: 60 ° C., 120 ° C., and 200 ° C. Thereafter, degreasing was performed, and decarburization annealing was performed at 830 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing.
After decarburization annealing, a part of the sample was collected and the texture of the 1/5 layer thickness was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
[0036]
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied, and a baked product was obtained at 800 ° C. From each product, an Epstein-sized test piece is cut out along the rolling direction, and the magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
Table 2 shows the texture of the decarburized annealed plate and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂The value of | Φ | that gives a maximum at = 45 ° and the random intensity ratio of {1241} <014> orientation are shown. In addition, the * mark was given to the remarks column for the sample whose {1241} <014> orientation had the maximum peak. Other samples are φ₁= 90 °, φ₂= There was a maximum peak above 45 °.
As shown in Table 2, the maximum peak of the texture of the decarburized annealed plate is φ in the Bunge Euler angle display.₁= 90 °, Φ: 58-62 ° or -58--62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the magnetic characteristics of the product are good. In addition, in order to control the texture of the decarburized annealed sheet as described above, the conditions of performing hot-rolled sheet annealing at a temperature of 950 ° C or lower and cold rolling at a temperature of 100 ° C or higher with a tandem rolling mill must be observed. It can be seen that it is extremely effective.
[0037]
[Table 2]

[0038]
[Example 2]
Nine 250 mm-thick steel slabs having the composition of g and h shown in Table 1 were each heated to a temperature of 1220 ° C. and hot-rolled to form a 2.7 mm hot-rolled coil. These coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then cold-rolled by a first tandem rolling mill to a thickness of 1.6 mm at a temperature of 80 ° C and at a temperature of 950 ° C. After performing the intermediate annealing, pickling and cold rolling with a second tandem rolling mill to a thickness of 0.22 mm were performed. At this time, as shown in Table 3, the hot-rolled sheet annealing temperature was changed in three ways: 800 ° C, 900 ° C and 1000 ° C, and the second cold rolling temperature was changed in three ways: 80 ° C, 150 ° C and 250 ° C. . Thereafter, degreasing treatment was performed, decarburization annealing was performed at 850 ° C. for 120 seconds, and then an annealing separator was applied to perform final finish annealing.
After decarburization annealing, a part of the sample was collected and the texture of the 1/5 layer thickness was measured. The texture was measured by an X-ray pole figure, and a three-dimensional texture was calculated from the measured data.
[0039]
After the final finish annealing, the unreacted annealing separator was removed, and an insulating coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product. From each product, an Epstein-sized test piece is cut out along the rolling direction, and the magnetic flux density B₈And W_17/50(Iron loss at a magnetic flux density of 1.7 T) was measured.
[0040]
Table 3 shows the texture after decarburization annealing and the magnetic properties of the product. For texture, φ₁= 90 °, φ₂The value of | Φ | that gives a maximum at = 45 ° and the random intensity ratio of {1241} <014> orientation are shown. In addition, the * mark was given to the remarks column for the sample whose {1241} <014> orientation had the maximum peak. Other samples are φ₁= 90 °, φ₂= There was a maximum peak above 45 °.
As shown in Table 3, the maximum peak of the decarburized and annealed sheet texture is φ in the Bunge Euler angle display.₁= 90 °, Φ: 58 to 62 ° or −68 to −62 °, φ₂When the random intensity ratio in the {1241} <014> orientation is 3.0 or more, the magnetic characteristics of the product are good. In addition, in order to control the texture of the decarburized annealed sheet as described above, the conditions of performing hot-rolled sheet annealing at a temperature of 950 ° C or lower and cold rolling at a temperature of 100 ° C or higher with a tandem rolling mill must be observed. It can be seen that it is extremely effective.
[0041]
[Table 3]

[0042]
【The invention's effect】
According to the present invention, it has become possible to stably produce a general-purpose unidirectional electrical steel sheet having good magnetic properties.
[Brief description of the drawings]
[Fig. 1] φ of texture of decarburized and annealed plate₁= 90 °, φ₂= It is a figure which shows random intensity ratio when (PHI) changes in a 45 degree cross section.
[Fig. 2] φ₁= 90 °, φ₂= The value of | Φ | which gives the maximum on the 45 ° section and the magnetic flux density B of the product₈It is a figure which shows the relationship.
FIG. 3: {1241} <014> orientation random intensity ratio and product magnetic flux density B₈It is a figure which shows the relationship.
FIG. 4 is a diagram showing a relationship between a random strength ratio of {1241} <014> orientation of a decarburized and annealed plate and a coefficient of variation of particle diameter.

Claims (2)

C: 0.02~0.07wt%, Si: 2.0 ~4.5 wt%, Mn: 0.03~2.5 wt%, Al: 0.005 ~0.030 wt% and N: 0.003 to 0.010 a silicon steel slab containing wt%, after heating After hot rolling and then hot-rolled sheet annealing, the final sheet thickness is obtained by one or more cold rollings sandwiching intermediate annealing, and further decarburization annealing and then applying an annealing separator. In the manufacturing method of the unidirectional electrical steel sheet that performs finish annealing from
The plate thickness after decarburization annealing is adjusted by adjusting the hot-rolled sheet annealing temperature while setting the slab heating temperature to 1260 ° C or less, and adjusting the rolling temperature as tandem rolling. A method for producing a unidirectional electrical steel sheet, wherein the texture in the layer region is a structure satisfying the following conditions.
The maximum peak orientation of the texture is Bunge's Euler angle notation: φ ₁ = 90 °, Φ: 58 to 62 ° or -58 to -62 °, φ ₂ = 45 °
Within the scope of
Random intensity ratio of {1241} <014> orientation is 3.0 or more.   The method for producing a unidirectional electrical steel sheet according to claim 1, wherein the hot-rolled sheet annealing is performed at a temperature of 950 ° C or lower, and the cold rolling is performed at a temperature of 100 ° C or higher with a tandem rolling mill.

Images