JP4292707B2 - Method for producing non-oriented electrical steel sheet - Google Patents

Description

【００１３】
ここで、[％Si],[％Mn],[％Ｐ]は、それぞれSi、Mn、Ｐの含有量を示し、dnは一辺の長さが４×ｄの正方形領域において測定した鋼板の平均結晶粒径、Ｋは測定領域の数を示す。
【００１４】
前記課題を解決するための第２の手段は、前記第１の手段であって、鋼板組成に応じて鋼板の平均結晶粒径ｄ(μｍ)が(3)式を満たすように、前記鋼スラブの加熱温度、熱延板焼鈍を行う場合はその焼鈍温度、冷間圧延率、仕上焼鈍時の昇温温度、焼鈍時間を調整することを特徴とするもの（請求項２）である。
18≦d≦40×([%Si]+0.7[%Mn]＋４[％Ｐ]+0.5) ^0.55 …(3)
前記課題を解決するための第３の手段は、前記第１の手段又は第２の手段であって、前記粒度分布Ａと結晶粒径ｄの比が0.20以下の範囲となるように、前記鋼スラブの加熱温度、熱延板焼鈍を行う場合はその焼鈍温度、冷間圧延率、仕上焼鈍時の昇温温度、焼鈍時間を調整することを特徴とするもの（請求項３）である。
前記課題を解決するための第４の手段は、前記第１の手段〜第３の手段のいずれかであって、鋼スラブに、さらにCu：0.2％以下および／またはCr：1.0％以下含有することを特徴とするもの（請求項４）である。
【００１５】
なお、本明細書及び図面において、鋼の成分を示す％は全て重量％である。
【００１６】
（発明に至る過程と結晶粒径、Si、Mn、Ｐ含有量の限定理由）
本発明者らは、無方向性電磁鋼板のかしめ性、すなわちかしめ結束力の向上方法について鋭意研究を重ねた。その結果、打ち抜き方式のかしめ締結では、打ち抜き端面形状の平滑化と、端面の強度向上がかしめ結束力の向上に有効であること、そして端面形状の平滑化および端面の強度向上には結晶粒径、結晶粒度分布、Si、Mn、Ｐ含有量の適正化が重要であることを見いだした。以下、本発明の詳細をその限定理由とともに説明する。
【００１７】
まず、かしめ性に及ぼす材質因子を見いだすために、ユーザー側でかしめ締結を行ったコアについてかしめ部の詳細調査を行った。その結果、まず、かしめ部の結束力は半打ち抜き状態のかしめ部の端面と、打ち抜かれた鋼板の端面の摩擦力が担っていることが判明した。
【００１８】
そして、さらに詳細に調査を行った結果、かしめ性に優れたコアとかしめ性に劣るコアでは、硬度はほぼ同一でもかしめ性に優れたコアとかしめ性に劣るコアがあることが認められ、かしめ性に劣るコアではかしめ端部の形状が粗く、しかもかしめ部が所定の深さまで押し込まれていないことが判明した。また、そのような端面形態を有する鋼板では、結晶粒径がやや粗大であったり、組織が不均一である傾向が見受けられた。
【００１９】
このような知見に基づき、まず、かしめ部の結束力に及ぼす結晶粒径の影響について調査を行った。Ｃ：0.0025％、Si：1.3％、Mn：0.3％、Ｐ：0.04％、Ｓ：0.0025％、sol.Al：0.31％、Ｎ：0.0018％、Ｏ：0.0011％を含有する鋼板について、種々の焼鈍温度で仕上げ焼鈍を実施して結晶粒径を11〜140μｍの範囲で変化させ、かしめ部の結束力の定量評価を行った。結晶粒径は、鋼板断面の板厚方向に直線を引き、その直線と交差する結晶粒の数を測定することにより求めた。
【００２０】
また、測定個所は20箇所とした。かしめ部の結束力は、自動打ち抜き・かしめ装置にて、スリットフープから20枚のディスクを打ち抜いて自動かしめを行った後に、積層コアを接着剤で冶具に固定して引張試験を行い、その剥離強度を測定て求めた。なお、このときのかしめ形状は、図１に示す平Ｖ形状とした。また、かしめ部の寸法は、幅２mm、長さ５mmとした。
【００２１】
剥離強度の測定結果を図２に示す。なお、図２に示す各点の結晶粒径は、左から順に、１１、１４、１６、１９、３０、４７、５８、６８、７８、８０、８３、９０、９３、107、123、140μｍである。
【００２２】
これより、結晶粒径には適正範囲が存在しており、本成分鋼では結晶粒径が14μｍ付近と80μｍ付近で剥離強度は臨界的に変化しており、この範囲内の結晶粒径で剥離強度は特に優れていることがわかる。また、かしめ部の寸法を幅2.5mm、長さ7mmとして同様の試験を実施したが、剥離強度の絶対値は増加するものの臨界粒径に相違は認められなかった。
【００２３】
そこで、実モータ部材におけるかしめ性と結晶粒径の関係を調査するために、結晶粒径を30μｍ、60μｍ、80μｍ、85μｍ、90μｍに調整した６種類の鋼板からステータコアを200台製造し、かしめ試験を実施した。かしめ性は、ステータコアの上部を固定して持ち上げ、自重でばらけが生じるかどうかで良否を判断した。なお、ステータコアの形状は、上面形状を外寸110mm、一辺約30mmの12角形とし、鋼板の板厚は0.5mm、1個あたりの積層枚数は180枚、ヨーク幅およびティース長さは約13mmとした。コアの重量は約3.5kgであった。かしめ部は、幅2mm、長さ5mm、押し込み量板厚１枚の平Ｖかしめとし、ステータのヨーク部に間隔が均等になるようにかしめ結束部を４箇所施した。金型のクリアランスは7％とした。その結果を表１に示す。
（表１）
【００２４】
【表１】

【００２５】
まず、結晶粒径が80μｍを超える鋼板Ｄ、Ｅでは、かしめ部の結束力が弱く、自重によりばらけるコアが頻発した。かしめ部の押し込み量の調整後も３〜８％のばらけコアが発生し、安定製造は困難であった。該鋼板でコアを一体化するには、かしめ部を６個としなければならなかった。一方、結晶粒径が80μｍの鋼板Ｃでは、ばらけの発生頻度は格段に低減され、２％であった。この場合、押し込み量の調整によりばらけは解消された。結晶粒径が60μｍ以下の鋼板Ａ、Ｂでは、コアはさらに強く結束しており、全くばらけは生じなかった。
【００２６】
このように、かしめ部の剥離強度とかしめ性はよく対応しており、剥離強度が弱い鋼板ではコアのばらけが生じやすいことがわかる。また、剥離強度が45Ｎ以上ではコアのばらけの発生頻度が著しく低減され、52Ｎ以上では少ないかしめ部でも十分良好なかしめ性が得られることがわかる。図２において、結晶粒径80μｍおよび60μｍは、それぞれ剥離強度45Ｎおよび52Ｎに対応する。
【００２７】
かしめ試験を実施したコアのかしめ部の断面観察、かしめ部表面のSEM観察を行ったところ、結晶粒径が80μｍを超えたコアでは、押し込み時の摩擦力でかしめ部表層に塑性変形が生じ、所定の位置まで押し込まれていないかしめ部が発生していることが判明した。さらに、塑性変形の発生原因を調査するために、かしめ結束前のかしめ部（Ｖノッチ部）の観察を行った。その結果、かしめ性良好材とかしめ性不良材とで打ち抜き外周寸法に大きな差は認められないものの、かしめ端面においては、かしめ不良材では数100μｍピッチで10〜40μｍ幅の微小なダレが生じており、微小な範囲での寸法精度が劣化していることが判明した。これは、結晶粒径が所定範囲を超えると打ち抜き端面の形態に個々の結晶粒の機械特性の影響が現れてくるためと推測される。また、鋼板の降伏強度が低下したことも塑性変形の発生原因の一つと考えられる。
一方、結晶粒径が20μｍ以下の鋼板では、かしめ端面のせん断面の比率が少ないことが判明した。つまり、細粒材ではせん断面同士の接触面積が減少して剥離強度が低下したものと考えられる。
【００２８】
以上により、かしめ性を支配する因子のひとつとして、鋼板の強度があることが示唆された。そこで次に、かしめ性に及ぼす鋼板成分の影響を調査した。Ｃ：0.001〜0.005％、Si：tr.〜4％、Mn：0.05〜2％、Ｐ：tr.〜0.2％、Ｓ：tr.〜0.02％、sol.Al：tr.〜2％、Ｎ：0.0008〜0.01％、Cr：tr.〜1.5％、Cu：tr.〜0.1％、Ni：tr.〜0.1％、Mo：tr.〜0.2％、Ca：tr.〜0.004％、Ｂ：tr.〜0.002％、Sb：tr.〜0.05％、Sn：tr.〜0.05％を含有する鋼を溶製し、かしめ部の剥離強度に及ぼす各種元素の影響を調査した。
【００２９】
その結果、鋼板成分の中でもSi含有量、Mn含有量、Ｐ含有量が剥離強度に大きな影響を及ぼしており、およそMnはSiの0.7倍、ＰはSiの４倍の効果を有していることが判明した。それ以外の元素は上記の添加量の範囲の中で顕著な効果は認められなかった。また、Ｓ、Ｎ等の元素は、後述するようにMnＳ、AlＮを形成して鋼板の粒度分布に影響を及ぼすが、結晶粒径と粒度分布がほぼ同一であれば、これら自身による顕著な効果は認められなかった。
【００３０】
そこで、Si、Mn、P含有量の異なる種々の鋼板に対してかしめ性の向上する適正粒径を調査した。その結果を図３に示す。これより、鋼板の結晶粒径ｄを
14≦ｄ≦60×([%Si]+0.7[%Mn]＋4[%P]＋0.3)^0.45 …(1)
の範囲に制御したときにかしめ部の剥離強度が著しく向上することが判明した。鋼板組成と結晶粒径がこの範囲にあるときに、45N以上の高い剥離強度が得られる。このとき、端面での変形が著しく軽減されていた。以上より、本発明では鋼板の結晶粒径は、上式の範囲に限定する。
【００３１】
さらに鋼板の結晶粒径dを、
18≦ｄ≦40×([%Si]+0.7[%Mn]＋４[%Ｐ]＋0.5)^0.55…(3)
の範囲に制御することにより、52Ｎ以上のさらに高い剥離強度が得られる。したがって、結晶粒径はこの範囲とすることが望ましい。
【００３２】
ところが、結晶粒径を本発明範囲に制御しても依然かしめ不良の発生する場合が認められた。そこで、本発明者らがその原因について詳細な調査を実施したところ、鋼板の結晶組織が不均一な場合にかしめ不良が高い頻度で発生していることが判明し、よって、かしめ性に優れた鋼板を得るためには、鋼板の結晶平均粒径と結晶粒度分布を同時に制御する必要があることが明らかになった。
【００３３】
そこで、かしめ部の剥離強度と鋼板組織の均一性との関係を調査するために、Ｃ：0.0025％、Si：1.3％、Mn：0.3％、Ｐ：0.04％、Ｓ：0.0025％、sol.Al：0.31％、Ｎ：0.0018％、Ｏ：0.0011％を含有する鋼板について、スラブの加熱温度、熱延板焼鈍温度、冷間圧延率、仕上げ焼鈍時の昇温速度、焼鈍時間等を調整して鋼板の粒度分布を変化させた鋼板を作製し、剥離強度を調査した。なお、鋼板の結晶粒径は78μｍに調整した。ここで、粒度分布は、鋼板の平均粒径をdとしたときに、一辺が4dで囲まれる正方形領域内での平均粒径dnを個別に20箇所以上求め、それぞれの領域で測定されたdnとｄから下式で求められるＡにより定義した。なお、Ｋは結晶粒径を測定した領域の数を示す（Ｋ≧20）。このようにして得られたＡとｄの比を採用することにより、鋼板の結晶粒度のばらつきが精度よく示されることが確認された。
【００３４】
【数３】

【００３５】
得られた結果を図４に示す。図４より、鋼板の粒度分布もかしめ性に多大な影響を及ぼしており、Ａ／ｄを0.24以下とすことにより、高い剥離強度が得られることがわかる。さらにＡ／ｄが0.20以下とすると剥離強度はさらに向上する。A／ｄが0.24以下の鋼板は結晶組織が均一であり、微小範囲での打ち抜き端面の寸法精度が向上していることが判明した。
【００３６】
したがって、本発明において鋼板の結晶粒径ｄと粒度分布を示すＡはこれらの比で0.24以下とする。さらに、これらの比は0.20以下とすることが望ましい。
【００３７】
このように、かしめ締結では、打ち抜き加工で必要とされてきた硬度とは別の結晶粒径、粒度分布といった材質因子を鋼板組成に応じて制御することも重要である。なお、図４に示された点のＡ／ｄの値は、左から順に、0.12、0.15、0.17、0.20、0.22、0.24、0.25、0.26、0.28、0.30である。
【００３８】
このように、かしめ締結では、かしめ部での互いのせん断面での変形を防止することが重要であり、従来、打ち抜き加工で必要とされてきた硬度とは別の因子である結晶粒径、粒度分布も適正化する必要があることがわかる。
【００３９】
（その他の成分の限定理由）
以下に、その他の成分の限定理由について説明する。
Ｃ：Ｃは0.005％を超えて含有されると磁気時効により磁気特性が劣化するので、0.005％以下とする。
Si：Siは鋼板の強度を上昇させてかしめ性を向上させる元素である。また、固有抵抗を上げて鉄損を低減するのに有効な元素である。しかしながら、４％超えでは硬度が高くなり打ち抜き性が著しく劣化するので、Siの含有量は４％以下（但し、０％の場合を含む）とする。
Mn：Mnは鋼板の強度を上昇させてかしめ性を向上させる元素である。また、熱間圧延時の赤熱脆性の防止や、粒成長性の向上にも有効な元素である。しかしながら、２％超えになると磁気特性が劣化するので、Mn の含有量は２％以下（但し、0％の場合を含む）とする。
【００４０】
sol.Al：sol.Alは、Ｎを固定して粒成長性を向上させる元素である。しかしながら、２％を超えで含有させても鉄損の低減効果は小さく、いたずらにコスト上昇を招くので２％以下（但し、０％の場合を含む）とする。
Ｓ：Ｓは0.012％を超えると組織が不均一となりやすい。また、磁気特性が劣化する。したがって、Sは0.012％以下（但し、0％の場合を含む）とする。
Ｐ：ＰはSiと同様に鋼板の強度、固有抵抗を上げてかしめ性、磁気特性を向上させる元素である。ただし、0.2％を超えて添加すると著しい脆化を招くため、0.2％以下(但し、０％の場合を含む)とする。
Ｎ：Ｎは0.005％を超えると磁気特性が劣化する。また、組織も不均一となりやすい。したがって、値は0.005％以下とする。
【００４１】
これ以外の元素として、Cu、Cr、Ni、Mo、Ca、Ｂ、Sb、Sn等を添加しても本発明の効果は損なわれないので磁気特性を向上させる目的で添加してもよい。例えば、Cuは集合組織を改善する目的で、Cr、Ni、Moは固有抵抗を高める目的で、Caは硫化物や酸化物を粗大化して粒成長性を向上させる目的で、Ｂは窒化物を粗大化して粒成長性を向上させる目的で、または鋼板の内部酸化を防止する目的で、Sb、Snは集合組織を向上させる目的で、または鋼板表層の酸化や窒化を防止する目的で添加することができる。
【００４２】
（製造方法）
次に本発明のかしめ性に優れた無方向性電磁鋼板の製造方法について説明する。
まずはじめに、仕上焼鈍後の粒度分布を制御する方法について述べる。鋼板成分においては、Ｓ、Ｎを極力少なくすることが重要である。これは、MnＳ、AlＮなどの析出物はクラスター化しやすいので、これらが存在すると熱延板焼鈍後や引き続く仕上焼鈍後の組織が不均一になりやすいためである。
熱延時のスラブ加熱温度は出来るだけ高い方が良く、好ましくは1140℃以上とすることである。これにより、MnＳ、AlＮのクラスター化が軽減され、より結晶組織が均一化する。熱延板の焼鈍温度は低い方が好ましい。磁気特性、とりわけＬ方向の磁気特性を改善するには、冷延前の結晶粒径を大きくすることが効果的であるが、かしめ性を考慮する場合にはむしろ冷延前の結晶粒径は小さいほどよい。冷延前粒径は300μｍ以下とすることが好ましい。
【００４３】
冷間圧延率は高い方が好ましい。最終冷間圧延率を50〜70％とすると磁気特性は効果的に改善されるが、冷間圧延率が65％以下では組織が不均一になりやすいので、かしめ性の観点からは65％以上とすることが好ましい。
【００４４】
引き続く仕上焼鈍では焼鈍速度を極力小さくすることが重要である。これは、焼鈍後の結晶組織は仕上焼鈍の再結晶組織の影響を特に強く受けるためであり、仕上焼鈍の昇温速度が速いと、冷延前組織や冷延での転位密度の分布状態の影響を顕著に受けて再結晶組織が不均一になる。生産性の観点からはライン速度を大きくすることが望ましいが、かしめ性の観点からはライン速度を小さくして昇温速度を小さくすることが肝要である。
【００４５】
昇温速度は30℃/sec以下とすることが望ましい。なお、ここで昇温速度は、400〜740℃の範囲の平均昇温速度を採用するのがよい。これは、この温度範囲で再結晶が顕著に進行するためである。焼鈍時間は長い方が好ましい。これは、焼鈍時間の長時間化により再結晶組織がある程度均質化されるためである。好ましくは40sec以上とすることである。
【００４６】
以上の製造条件を組み合わせることにより、結晶組織がより均一になり、かしめ性が向上する。とくに、この中でも冷延前の結晶粒径と仕上焼鈍の昇温速度の効果が大きい。また、スラブの加熱温度、Ｓ、Ｎ量、冷間圧延率も含めて、これらはその効果が互いに加算されるので磁気特性、生産性等を勘案しながら製造条件を適正化する必要がある。
【００４７】
例えば、磁気特性を向上させるために冷延前の結晶粒径を300μｍ以上とする場合には、引き続く仕上焼鈍の昇温速度を20℃/sec以下にすることが有効である。あるいは、ある程度の生産性も考慮して昇温速度を25℃/sec程度とするならば、Ｓ、Ｎはともに0.002％以下に低減し、スラブの加熱温度は1140℃以上、冷間圧延率は77％以上とし、均熱時間も極力長くすることが有効である。
【００４８】
適正粒径を得るためには、焼鈍温度、焼鈍時間を適正化する必要がある。適正焼鈍条件は、Si含有量、Ｓ、Ｎ含有量、冷延前粒径、冷圧率により変化するが、730〜950℃の範囲で30〜80sec行うのがよい。
【００４９】
本発明においては、その他の製造条件は通常の無方向性電磁鋼板を製造する方法で構わない。すなわち、転炉で吹練した溶鋼を脱ガス処理し所定の成分に調整し、引き続き鋳造を行う。熱間圧延条件は、スラブの加熱温度を1100〜1250℃、仕上圧延温度は750〜850℃、巻取り温度は600〜730℃の範囲とするのが好ましいが特に規定するものではない。また、熱間圧延後の熱延板焼鈍は行ってもよいが必須ではない。次いで一回の冷間圧延、もしくは中間焼鈍をはさむ２回以上の冷間圧延により所定の板厚とした後に、仕上げ焼鈍を行う。
【００５０】
また、打ち抜き性や絶縁性を向上する目的で有機／無機混合被膜を塗布してもよい。この場合、皮膜厚は薄い方が好ましい。好ましい範囲は、0.5μｍ以下である。
【００５１】
【実施例】
転炉で吹練した溶鋼を脱ガス処理し、所定の成分に鋳造後、スラブを1150℃で１hr加熱して板厚3.6mm、2.0mm、1.4mmまで熱間圧延を行い、680℃で巻取った後、酸洗を行った。Siを1％以上含有する鋼については800〜900℃×３hrの熱延板焼鈍を実施して冷延前の結晶粒径を調整した。その後、板厚0.5mmまで冷間圧延を行った後に、10％Ｈ₂−Ｎ₂の雰囲気で昇温速度を14〜35℃/secとして740℃〜945℃×34〜78secの仕上焼鈍を行った。
【００５２】
仕上げ焼鈍後の鋼板をスリットして幅100mmのフープとした後に、20枚のディスクを打ち抜いて自動かしめを行い、かしめサンプルを作製した。このときのかしめ部の形状は平Ｖ形状とした。かしめ部の結束力は、積層コアを接着剤で冶具に固定して引張試験を行い、その剥離強度を測定して求めた。また、幅2mm、長さ5mmのかしめ部を４箇所有するコアをそれぞれ200個作製し、かしめ性を評価した。コア形状および重量は、外寸110mm、鋼板積層枚数180枚、重量約3.5kgとした。かしめ性は、３段階で評価し、コアのばらけが、押し込み量を板厚1枚で全く生じなかった場合に◎、最大で板厚２枚までの押し込み量の調整によりコアのばらけが防止できた場合を○、押し込み量を調整しても1個以上のばらけが発生した場合を×とした。
【００５３】
鋼板の化学成分を表２に示す。
鋼板の冷延前粒径、冷間圧延率、仕上焼鈍の昇温速度、仕上焼鈍の焼鈍温度、焼鈍温度における均熱時間、結晶粒径、粒度分布および、かしめ部の剥離強度、かしめ性の評価結果を表３に示す。なお、昇温速度は、400℃から740℃の範囲の平均値を記載した。また、表３において臨界粒径d*として示されているものは、
d*=60([%Si]+0.7[%Mn]+4[%Ｐ]+0.3)^0.45 …(4)
で示される値であり、(1)式で示されたｄの上限値に対応する値である。
【００５４】
表２及び表３より、鋼板の化学成分、結晶粒径、粒度分布を適正範囲に制御した本発明例においては、かしめ部の剥離強度が高いことがわかる。
一方、鋼板No.13では焼鈍温度が高く、鋼板の結晶粒径が本発明範囲外となっている。鋼板No.14では焼鈍温度が低く、焼鈍時間も短いので鋼板の結晶粒径が本発明範囲外となっている。鋼板No.15では焼鈍温度が高く、鋼板の結晶粒径が本発明範囲外となっている。鋼板No.16では熱延板の結晶粒径が大きいうえに昇温速度も大きいため、粒度分布が本発明範囲外となっている。鋼板No.17では冷間圧延率が低いうえに昇温速度も速いため、粒度分布が本発明範囲外となっている。鋼板No.18ではS量が高いうえに昇温速度がやや大きくなっているため、粒度分布が本発明範囲外となっている。したがって、鋼板No.13〜18の鋼板はいずれもかしめ性に劣る。
【００５５】
（表２）
【表２】

【００５６】
(表３)
【表３】

【００５７】
【発明の効果】
以上述べたように、本発明により製造された無方向性電磁鋼板は、かしめ性に優れており、製品とする際にかしめ加工を行う無方向性電磁鋼板として用いるのに好適である。本発明に係る無方向性電磁鋼板を使用すれば、かしめ部の小径化によるモータ類の小型化、コア特性の向上、あるいはユーザー側での生産性の向上に寄与することができる。
【図面の簡単な説明】
【図１】かしめの剥離強度を測定した測定サンプルの形状を示す概要図である。
【図２】鋼板の結晶粒径とかしめ部の剥離強度の関係を示す図である。
【図３】 Si、Mn、Ｐの含有量、結晶粒径とかしめ部の剥離強度の関係を示す図である。
【図４】鋼板の結晶粒径、粒度分布とかしめ部の剥離強度の関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-oriented electrical steel sheet suitable for use as a core material for motors and transformers, and particularly relates to a method for producing a non-oriented electrical steel sheet suitable for caulking. Is.
[0002]
[Prior art]
Since non-oriented electrical steel sheets that are widely used as iron core materials for motors and transformers are used by laminating steel sheets, caulking is often used as a method for fastening laminated steel sheets. This caulking is a continuous punching process in which a convex part with a width of a few millimeters is formed on the steel sheet, and then in the continuous automatic caulking process, the convex half punched part is fitted into the upper and lower steel sheets. Is a method of fastening. Conventionally, rivet type caulking that presses and fastens aluminum bars with a diameter of 1 to 2 mm and fastening using laser welding and TIG welding have been widely performed. The stamping method is the mainstream.
[0003]
On the other hand, recently, as the motors become smaller and more efficient, further reduction in the diameter and the number of caulking portions are being demanded. For example, in a spindle motor for a hard disk of a computer, 4 to 12 pieces of caulking with a diameter of about 0.5 mm are employed for a motor with a diameter of about 3 cm, and further reduction in the diameter of the caulking portion is required. In addition, in a motor core for a compressor, it is important to reduce the diameter or the number of caulking portions whose magnetic characteristics are deteriorated due to plastic deformation in order to improve efficiency.
[0004]
However, since the required level for caulking becomes stricter along with this, caulking defects often occur when conventional steel sheets are used as they are. This caulking failure is a phenomenon in which the binding force of the core is weak and scatters until the core caulked by the automatic caulking device is transported to the next process.
[0005]
From such a background, the development of a caulking fastening method that further improves the binding force or the development of a technique for improving the caulking binding force from the material surface has been eagerly desired. Conventionally, the improvement of caulking has often depended on the design and adjustment of the mold because there is little material knowledge about caulking. That is, for each target steel sheet, the shape and number of caulking fastening portions, clearance, push-in amount (die height), and the like have been optimized. However, since the material is different for each target steel plate, the actual situation is that sufficient measures are not necessarily taken.
[0006]
On the other hand, several techniques have been disclosed from the standpoint of materials. For example, in JP-A-1-315104, the film thickness of a steel sheet is 0.3 to 0.4 μm, which is thinner than usual. A method for reducing the amount of sulfide and improving the binding force of the caulking fastening portion is disclosed. In JP-A-5-33063, a steel plate containing 0.015 to 0.05% of C is subjected to skin pass rolling, and then subjected to an aging treatment to adjust the hardness of the steel plate to Hv: 135 to 165, thereby punching and skewing. A method for improving the above is disclosed.
[0007]
[Problems to be solved by the invention]
However, in the technique disclosed in Japanese Patent Laid-Open No. 1-315104, although the binding force is improved by reducing the film thickness, the wear of the mold increases. Further, the effect of improving the binding force by reducing MnS is small, and further material improvements are necessary.
[0008]
On the other hand, in the technique disclosed in JP-A-5-33063, in addition to containing a large amount of C, skin pass rolling is essential, so that excellent magnetic properties are imparted even if it is excellent in caulking. It ’s difficult.
[0009]
Many technologies that focus on punchability have been disclosed, but most of them are related to the reduction of die wear by adjusting the hardness and the improvement of the outer peripheral dimensional accuracy of the punched core. Did not give.
[0010]
This invention is made | formed in view of such a situation, and makes it a subject to provide the manufacturing method of the non-oriented electrical steel plate excellent in caulking property, and suitable as a member which performs a caulking process.
[0011]
[Means for Solving the Problems]
The first means for solving the above-mentioned problems is, by weight%, C: 0.005% or less, Si: 4% or less, Mn: 2% or less, sol.Al: 1.5% or less (including 0) , S: A steel slab containing 0.012% or less, P: 0.2% or less, and N: 0.005% or less , the balance being Fe and inevitable impurities is heated and hot-rolled, then cold-rolled, and further subjected to finish annealing A non-oriented electrical steel sheet manufacturing method in which the average grain size d (μm) of the steel sheet satisfies the formula (1) according to the steel plate composition, and the grain size distribution A of the crystal grains is defined by the formula (2) When the steel slab is heated and hot-rolled sheet annealed so that the ratio of the grain size distribution A and the average crystal grain size d of the steel sheet is 0.24 or less, the annealing temperature and the cold rolling rate The method for producing a non-oriented electrical steel sheet (Claim 1), characterized in that the temperature rise temperature and the annealing time during finish annealing are adjusted.
14 ≦ d ≦ 60 × ([% Si] +0.7 [% Mn] +4 [% P] +0.3) ^0.45 … (1)
[0012]
[Expression 2]

[0013]
Here, [% Si], [% Mn], and [% P] indicate the contents of Si, Mn, and P, respectively, and dn is the average of the steel sheet measured in a square region with a side length of 4 × d. The crystal grain size, K, indicates the number of measurement regions.
[0014]
The second means for solving the above-mentioned problem is the first means, wherein the steel slab is adjusted so that the average crystal grain size d (μm) of the steel sheet satisfies the formula (3) according to the steel sheet composition. In the case where the heating temperature and the hot-rolled sheet annealing are performed, the annealing temperature, the cold rolling rate, the temperature rise temperature during finish annealing, and the annealing time are adjusted (Claim 2).
18 ≦ d ≦ 40 × ([% Si] +0.7 [% Mn] +4 [% P] +0.5 ) ^0.55 … (3)
A third means for solving the problem is the first means or the second means, wherein the steel has a ratio of the grain size distribution A and the crystal grain size d of 0.20 or less. When performing slab heating temperature and hot-rolled sheet annealing, the annealing temperature, the cold rolling rate, the temperature rise temperature during finish annealing, and the annealing time are adjusted (Claim 3).
A fourth means for solving the above-mentioned problems is any one of the first to third means, and further contains Cu: 0.2% or less and / or Cr: 1.0% or less in the steel slab. (Claim 4).
[0015]
In the present specification and drawings, all the percentages indicating the steel components are percentages by weight.
[0016]
(The process leading to the invention and the reasons for limiting the crystal grain size, Si, Mn, and P content)
The inventors of the present invention have made extensive studies on a method for improving the caulking property of the non-oriented electrical steel sheet, that is, the caulking binding force. As a result, in stamping-type caulking, it is effective to smooth the punched end face shape and improve the end face strength to improve the caulking binding force, and to smooth the end face shape and improve the end face strength, the crystal grain size It was found that optimization of crystal grain size distribution, Si, Mn, and P content is important. Hereinafter, the details of the present invention will be described together with the reasons for limitation.
[0017]
First, in order to find the material factor that affects the caulking property, a detailed investigation of the caulking part was performed on the core that was caulked by the user. As a result, first, it was found that the binding force of the caulking part is caused by the frictional force between the end face of the caulking part in the half-punched state and the end face of the punched steel sheet.
[0018]
As a result of further detailed investigation, it was found that a core with excellent caulking properties and a core with poor caulking properties have a core with excellent caulking properties and a core with poor caulking properties, although the hardness is almost the same. It has been found that in the core having poor properties, the shape of the caulking end portion is rough and the caulking portion is not pushed to a predetermined depth. Moreover, in the steel plate which has such an end surface form, the tendency for the crystal grain diameter to be a little coarse and the structure | tissue to be uneven was seen.
[0019]
Based on these findings, first, the effect of the crystal grain size on the caulking force was investigated. Various annealing for steel sheets containing C: 0.0025%, Si: 1.3%, Mn: 0.3%, P: 0.04%, S: 0.0025%, sol.Al: 0.31%, N: 0.0018%, O: 0.0011% Finish annealing was carried out at a temperature to change the crystal grain size in the range of 11 to 140 μm, and quantitative evaluation of the binding force of the caulking portion was performed. The crystal grain size was determined by drawing a straight line in the thickness direction of the cross section of the steel sheet and measuring the number of crystal grains intersecting the straight line.
[0020]
In addition, 20 measurement locations were used. The binding force of the caulking part is automatically punched by punching 20 discs from the slit hoop with an automatic punching and caulking device, and then the laminated core is fixed to the jig with an adhesive, and a tensile test is performed. The strength was determined by measurement. The caulking shape at this time was a flat V shape shown in FIG. The size of the caulking portion was 2 mm in width and 5 mm in length.
[0021]
The measurement result of peel strength is shown in FIG. The crystal grain size at each point shown in FIG. 2 is 11, 14, 16, 19, 30, 47, 58, 68, 78, 80, 83, 90, 93, 107, 123, and 140 μm in order from the left. is there.
[0022]
As a result, there is an appropriate range for the crystal grain size, and in this component steel, the peel strength changes critically around the crystal grain size of 14 μm and 80 μm. It can be seen that the strength is particularly excellent. A similar test was carried out with the caulking portion dimensions of 2.5 mm in width and 7 mm in length. However, although the absolute value of the peel strength increased, no difference was observed in the critical particle size.
[0023]
Therefore, in order to investigate the relationship between the caulking property and the crystal grain size in actual motor members, 200 stator cores were manufactured from six types of steel plates with crystal grain sizes adjusted to 30 μm, 60 μm, 80 μm, 85 μm, and 90 μm, and caulking tests were performed. Carried out. The caulking property was judged as good or bad by whether the upper part of the stator core was fixed and lifted, and whether or not the weight was scattered by its own weight. The shape of the stator core is a dodecagonal shape with an outer dimension of 110 mm and a side of about 30 mm.The thickness of the steel sheet is 0.5 mm, the number of laminated sheets per piece is 180, and the yoke width and teeth length are about 13 mm. did. The weight of the core was about 3.5 kg. The caulking portion was a flat V caulking with a width of 2 mm, a length of 5 mm, and a pushing thickness of one sheet, and four caulking and bundling portions were applied to the yoke portion of the stator so that the intervals were uniform. The mold clearance was 7%. The results are shown in Table 1.
(Table 1)
[0024]
[Table 1]

[0025]
First, in the steel plates D and E having a crystal grain size of more than 80 μm, the binding force of the caulking portion was weak, and the core that was scattered by its own weight frequently occurred. Even after adjusting the pushing amount of the caulking portion, 3 to 8% of loose cores were generated, and stable production was difficult. In order to integrate the core with the steel plate, the number of caulking portions had to be six. On the other hand, in the steel plate C having a crystal grain size of 80 μm, the occurrence frequency of the fluctuation was significantly reduced to 2%. In this case, the variation was eliminated by adjusting the push-in amount. In the steel plates A and B having a crystal grain size of 60 μm or less, the cores were bound more strongly and no scatter occurred.
[0026]
Thus, it can be seen that the peel strength and the caulking property of the caulking portion correspond well, and that the steel sheet with low peel strength is likely to cause the core to be scattered. It can also be seen that when the peel strength is 45 N or more, the occurrence frequency of the core variation is remarkably reduced, and when 52 N or more, sufficiently good caulking properties can be obtained even with a small caulking portion. In FIG. 2, crystal grain sizes of 80 μm and 60 μm correspond to peel strengths of 45 N and 52 N, respectively.
[0027]
When the cross-sectional observation of the caulked portion of the core subjected to the caulking test and the SEM observation of the surface of the caulking portion were performed, in the core where the crystal grain size exceeded 80 μm, plastic deformation occurred in the surface of the caulked portion due to the frictional force during indentation, It has been found that a caulking portion that has not been pushed into a predetermined position has occurred. Furthermore, in order to investigate the cause of the plastic deformation, the caulking part (V notch part) before caulking was observed. As a result, although there is no significant difference in the punching outer peripheral size between the caulking good material and the caulking poor material, the caulking end surface has a small sag of 10 to 40 μm width at a pitch of several hundreds μm. As a result, it was found that the dimensional accuracy in a minute range was deteriorated. This is presumably because when the crystal grain size exceeds a predetermined range, the influence of the mechanical properties of the individual crystal grains appears on the form of the punched end face. In addition, a decrease in the yield strength of the steel sheet is considered to be one of the causes of plastic deformation.
On the other hand, it was found that the ratio of the shear surface of the caulking end face is small in the steel sheet having a crystal grain size of 20 μm or less. That is, in the fine-grained material, it is considered that the contact area between the shear surfaces is reduced and the peel strength is reduced.
[0028]
From the above, it was suggested that the strength of the steel sheet is one of the factors governing the caulking property. Then, next, the influence of the steel plate component on the caulking property was investigated. C: 0.001 to 0.005%, Si: tr. To 4%, Mn: 0.05 to 2%, P: tr. To 0.2%, S: tr. To 0.02%, sol. Al: tr. To 2%, N: 0.0008-0.01%, Cr: tr.-1.5%, Cu: tr.-0.1%, Ni: tr.-0.1%, Mo: tr.-0.2%, Ca: tr.-0.004%, B: tr.- Steels containing 0.002%, Sb: tr. To 0.05%, Sn: tr. To 0.05% were melted, and the influence of various elements on the peel strength of the caulking portion was investigated.
[0029]
As a result, among the steel plate components, the Si content, the Mn content, and the P content have a great influence on the peel strength, and Mn has an effect 0.7 times that of Si and P has an effect 4 times that of Si. It has been found. The other elements did not show a significant effect within the above range of addition amount. In addition, elements such as S and N form MnS and AlN as will be described later, and affect the particle size distribution of the steel sheet. Was not recognized.
[0030]
Therefore, the appropriate grain size for improving the caulking property was investigated for various steel sheets having different Si, Mn and P contents. The result is shown in FIG. From this, the crystal grain size d of the steel sheet
14 ≦ d ≦ 60 × ([% Si] +0.7 [% Mn] +4 [% P] +0.3) ^0.45 … (1)
It was found that the peel strength of the caulked portion was remarkably improved when the amount was controlled in this range. When the steel plate composition and the crystal grain size are in this range, a high peel strength of 45 N or more can be obtained. At this time, the deformation at the end face was remarkably reduced. From the above, in the present invention, the crystal grain size of the steel sheet is limited to the range of the above formula.
[0031]
Furthermore, the grain size d of the steel sheet is
18 ≦ d ≦ 40 × ([% Si] +0.7 [% Mn] +4 [% P] +0.5) ^0.55 … (3)
By controlling in this range, an even higher peel strength of 52 N or more can be obtained. Therefore, the crystal grain size is preferably within this range.
[0032]
However, even when the crystal grain size is controlled within the range of the present invention, a case where a caulking defect still occurs has been recognized. Therefore, when the present inventors conducted a detailed investigation on the cause, it was found that when the crystal structure of the steel sheet is non-uniform, caulking defects occur frequently, and thus the caulking property is excellent. In order to obtain a steel sheet, it became clear that the crystal mean grain size and crystal grain size distribution of the steel sheet must be controlled simultaneously.
[0033]
Therefore, C: 0.0025%, Si: 1.3%, Mn: 0.3%, P: 0.04%, S: 0.0025%, sol.Al in order to investigate the relationship between the peel strength of the caulking part and the uniformity of the steel sheet structure. : For steel sheets containing 0.31%, N: 0.0018%, O: 0.0011%, adjust the slab heating temperature, hot-rolled sheet annealing temperature, cold rolling rate, temperature rise rate during finish annealing, annealing time, etc. Steel sheets with varying particle size distribution were prepared and the peel strength was investigated. The crystal grain size of the steel sheet was adjusted to 78 μm. Here, when the average particle size of the steel sheet is d, the particle size distribution is obtained for 20 or more individual average particle sizes dn in a square region surrounded by 4d on one side, and dn measured in each region And d is defined by A obtained from the following equation. K represents the number of regions in which the crystal grain size was measured (K ≧ 20). By adopting the ratio of A and d thus obtained, it was confirmed that the variation in the crystal grain size of the steel sheet was accurately shown.
[0034]
[Equation 3]

[0035]
The obtained results are shown in FIG. As can be seen from FIG. 4, the particle size distribution of the steel plate has a great influence on the caulking properties, and a high peel strength can be obtained by setting A / d to 0.24 or less. Further, when A / d is 0.20 or less, the peel strength is further improved. It was found that the steel sheet having A / d of 0.24 or less has a uniform crystal structure and improved dimensional accuracy of the punched end face in a minute range.
[0036]
Accordingly, in the present invention, the crystal grain size d of the steel sheet and A indicating the particle size distribution are 0.24 or less in these ratios. Furthermore, it is desirable that these ratios be 0.20 or less.
[0037]
Thus, in the caulking, it is also important to control material factors such as crystal grain size and particle size distribution, which are different from the hardness required in the punching process, according to the steel plate composition. The values of A / d at the points shown in FIG. 4 are 0.12, 0.15, 0.17, 0.20, 0.22, 0.24, 0.25, 0.26, 0.28, and 0.30 in order from the left.
[0038]
Thus, in caulking, it is important to prevent deformation at each shearing surface at the caulking portion, and the crystal grain size, which is a factor different from the hardness conventionally required for punching, It can be seen that the particle size distribution also needs to be optimized.
[0039]
(Reason for limitation of other ingredients)
Below, the reason for limitation of another component is demonstrated.
C: If C exceeds 0.005%, the magnetic properties deteriorate due to magnetic aging, so 0.005% or less.
Si: Si is an element that increases the strength of the steel sheet and improves the caulking property. Moreover, it is an element effective in increasing the specific resistance and reducing the iron loss. However, if it exceeds 4%, the hardness becomes high and the punchability deteriorates remarkably, so the Si content is 4% or less (including the case of 0%).
Mn: Mn is an element that increases the strength of the steel sheet and improves the caulking property. In addition, it is an element effective for preventing red heat embrittlement during hot rolling and improving grain growth. However, since the magnetic properties deteriorate when it exceeds 2%, the Mn content is 2% or less (including the case of 0%).
[0040]
sol.Al: sol.Al is an element that fixes N and improves grain growth. However, even if the content exceeds 2%, the effect of reducing the iron loss is small, and the cost is unnecessarily increased. Therefore, the content is made 2% or less (including the case of 0%).
S: When S exceeds 0.012%, the structure tends to be non-uniform. In addition, the magnetic properties deteriorate. Therefore, S is 0.012% or less (including the case of 0%).
P: Like Si, P is an element that increases the strength and specific resistance of the steel sheet to improve the caulking properties and magnetic properties. However, if added over 0.2%, significant embrittlement will be caused, so the content should be 0.2% or less (including the case of 0%).
N: When N exceeds 0.005%, the magnetic properties deteriorate. In addition, the structure tends to be uneven. Therefore, the value is 0.005% or less.
[0041]
Even if Cu, Cr, Ni, Mo, Ca, B, Sb, Sn, or the like is added as an element other than this, the effect of the present invention is not impaired, so it may be added for the purpose of improving magnetic properties. For example, Cu is for the purpose of improving the texture, Cr, Ni, and Mo are for the purpose of increasing specific resistance, Ca is for the purpose of coarsening sulfides and oxides to improve grain growth, and B is for nitride. Sb and Sn are added for the purpose of coarsening and improving grain growth, or for the purpose of preventing internal oxidation of the steel sheet, for the purpose of improving the texture or for the purpose of preventing oxidation and nitriding of the steel sheet surface layer. Can do.
[0042]
(Production method)
Next, the manufacturing method of the non-oriented electrical steel sheet excellent in the caulking property of the present invention will be described.
First, a method for controlling the particle size distribution after finish annealing will be described. In steel plate components, it is important to reduce S and N as much as possible. This is because precipitates such as MnS and AlN are likely to be clustered, and if they are present, the structure after hot-rolled sheet annealing and subsequent finish annealing tends to be non-uniform.
The slab heating temperature during hot rolling should be as high as possible, preferably 1140 ° C. or higher. Thereby, clustering of MnS and AlN is reduced, and the crystal structure becomes more uniform. The annealing temperature of the hot-rolled sheet is preferably lower. In order to improve the magnetic properties, particularly the magnetic properties in the L direction, it is effective to increase the crystal grain size before cold rolling, but when considering caulking properties, the crystal grain size before cold rolling is rather Smaller is better. The particle size before cold rolling is preferably 300 μm or less.
[0043]
A higher cold rolling rate is preferable. When the final cold rolling rate is 50 to 70%, the magnetic properties are effectively improved. However, when the cold rolling rate is 65% or less, the structure tends to be non-uniform, so that it is 65% or more from the viewpoint of caulking. It is preferable that
[0044]
In the subsequent finish annealing, it is important to reduce the annealing speed as much as possible. This is because the crystal structure after annealing is particularly strongly affected by the recrystallization structure of finish annealing. When the temperature increase rate of finish annealing is high, the dislocation density distribution state in the structure before cold rolling or in cold rolling The recrystallized structure becomes non-uniform due to the influence. From the viewpoint of productivity, it is desirable to increase the line speed, but from the viewpoint of caulking, it is important to decrease the line speed and decrease the temperature rising speed.
[0045]
The temperature rising rate is desirably 30 ° C./sec or less. In addition, it is good to employ | adopt the average temperature increase rate of the range of 400-740 degreeC here as a temperature increase rate. This is because recrystallization proceeds remarkably in this temperature range. A longer annealing time is preferred. This is because the recrystallized structure is homogenized to some extent by increasing the annealing time. Preferably, it is 40 sec or longer.
[0046]
By combining the above manufacturing conditions, the crystal structure becomes more uniform and the caulking property is improved. In particular, the effect of the crystal grain size before cold rolling and the temperature increase rate of finish annealing is great. Moreover, since the effects of these, including the heating temperature of the slab, the amount of S, N, and the cold rolling rate, are added together, it is necessary to optimize the manufacturing conditions while taking into consideration magnetic characteristics, productivity, and the like.
[0047]
For example, in order to improve the magnetic properties, when the crystal grain size before cold rolling is set to 300 μm or more, it is effective to set the temperature increase rate of the subsequent finish annealing to 20 ° C./sec or less. Alternatively, if the heating rate is about 25 ° C / sec in consideration of a certain degree of productivity, both S and N are reduced to 0.002% or less, the slab heating temperature is 1140 ° C or more, and the cold rolling rate is It is effective to set it to 77% or more and make the soaking time as long as possible.
[0048]
In order to obtain an appropriate particle size, it is necessary to optimize the annealing temperature and annealing time. The proper annealing condition varies depending on the Si content, the S and N contents, the grain size before cold rolling, and the cold pressure ratio, but it is preferable that the annealing is performed in the range of 730 to 950 ° C. for 30 to 80 seconds.
[0049]
In the present invention, other manufacturing conditions may be a method for manufacturing a normal non-oriented electrical steel sheet. That is, the molten steel blown in the converter is degassed and adjusted to a predetermined component, and then casting is performed. The hot rolling conditions are not particularly specified, although the heating temperature of the slab is preferably 1100 to 1250 ° C, the finish rolling temperature is 750 to 850 ° C, and the winding temperature is 600 to 730 ° C. Moreover, although hot-rolled sheet annealing after hot rolling may be performed, it is not essential. Next, after a predetermined sheet thickness is obtained by one cold rolling or two or more cold rolling sandwiching intermediate annealing, finish annealing is performed.
[0050]
Further, an organic / inorganic mixed film may be applied for the purpose of improving punchability and insulation. In this case, it is preferable that the film thickness is thinner. A preferred range is 0.5 μm or less.
[0051]
【Example】
The molten steel blown in the converter is degassed and cast to the prescribed components, and the slab is heated at 1150 ° C for 1 hour, hot rolled to 3.6mm, 2.0mm, and 1.4mm, and wound at 680 ° C. After taking, pickling was performed. The steel containing 1% or more of Si was subjected to hot-rolled sheet annealing at 800 to 900 ° C. for 3 hours to adjust the crystal grain size before cold rolling. Then, after cold rolling to a sheet thickness of 0.5 mm, finish annealing at 740 ° C to 945 ° C x 34 to 78 sec is performed at an increase rate of 14 to 35 ° C / sec in an atmosphere of 10% H ₂ -N _2. It was.
[0052]
The steel plate after finish annealing was slit into a 100 mm wide hoop, and then 20 discs were punched out and subjected to automatic caulking to produce a caulking sample. The shape of the caulking portion at this time was a flat V shape. The binding force of the caulking portion was obtained by fixing the laminated core to a jig with an adhesive, performing a tensile test, and measuring the peel strength. In addition, 200 cores each having four caulking portions with a width of 2 mm and a length of 5 mm were prepared, and the caulking property was evaluated. The core shape and weight were 110 mm in outer dimensions, 180 steel sheets laminated, and a weight of about 3.5 kg. The caulking property is evaluated in three stages. When the core does not disperse at all with a thickness of 1 sheet, the core can be prevented by adjusting the amount of indentation up to 2 sheets. Was marked with ◯, and when one or more fluctuations occurred even if the amount of pushing was adjusted, it was marked with ×.
[0053]
Table 2 shows the chemical composition of the steel sheet.
Pre-cold rolling grain size, cold rolling rate, finish annealing rate, finish annealing temperature, soaking time at annealing temperature, crystal grain size, grain size distribution, caulking peel strength, caulking The evaluation results are shown in Table 3. In addition, the temperature increase rate described the average value of the range of 400 degreeC to 740 degreeC. In Table 3, the critical particle diameter d * is
d * = 60 ([% Si] +0.7 [% Mn] +4 [% P] +0.3) ^0.45 … (4)
This is a value corresponding to the upper limit value of d shown in the equation (1).
[0054]
From Tables 2 and 3, it can be seen that the peel strength of the caulking portion is high in the present invention examples in which the chemical composition, crystal grain size, and particle size distribution of the steel sheet are controlled within appropriate ranges.
On the other hand, in steel plate No. 13, the annealing temperature is high, and the crystal grain size of the steel plate is outside the scope of the present invention. In steel plate No. 14, the annealing temperature is low and the annealing time is short, so the crystal grain size of the steel plate is outside the scope of the present invention. In steel plate No. 15, the annealing temperature is high, and the crystal grain size of the steel plate is outside the scope of the present invention. In steel plate No. 16, the grain size distribution is outside the scope of the present invention because the crystal grain size of the hot-rolled plate is large and the heating rate is also large. In steel plate No. 17, the cold rolling rate is low and the heating rate is fast, so the particle size distribution is outside the scope of the present invention. Steel plate No. 18 has a high S content and a slightly high temperature rise rate, and therefore the particle size distribution is outside the scope of the present invention. Therefore, all of the steel plates Nos. 13 to 18 have poor caulking properties.
[0055]
(Table 2)
[Table 2]

[0056]
(Table 3)
[Table 3]

[0057]
【The invention's effect】
As described above, the non-oriented electrical steel sheet produced according to the present invention has excellent caulking properties, and is suitable for use as a non-oriented electrical steel sheet that is caulked when used as a product. If the non-oriented electrical steel sheet according to the present invention is used, it can contribute to miniaturization of motors by reducing the diameter of the caulking portion, improvement of core characteristics, or improvement of productivity on the user side.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the shape of a measurement sample obtained by measuring the peel strength of caulking.
FIG. 2 is a diagram showing the relationship between the crystal grain size of a steel sheet and the peel strength at the caulking portion.
FIG. 3 is a graph showing the relationship between the content of Si, Mn and P, the crystal grain size, and the peel strength at the caulking part.
FIG. 4 is a graph showing the relationship between the crystal grain size and particle size distribution of a steel sheet and the peel strength at the caulking portion.

Claims (4)

By weight%, C: 0.005% or less, Si: 4% or less, Mn: 2% or less, sol.Al: 1.5% or less (including 0) , S: 0.012% or less, P: 0.2% or less, N: 0.005 Is a non-oriented electrical steel sheet manufacturing method, in which a steel slab containing the balance of Fe and the balance of Fe and inevitable impurities is heated and hot-rolled, then cold-rolled and further subjected to finish annealing, Depending on the composition, when the average grain size d (μm) of the steel sheet satisfies the formula (1) and the grain size distribution A of the grain is defined by the formula (2), the grain size distribution A and the average grain size of the steel plate Adjust the heating temperature of the steel slab and the annealing temperature, the cold rolling rate, the temperature rise temperature during finish annealing, and the annealing time so that the ratio of the diameter d is in the range of 0.24 or less. The manufacturing method of the non-oriented electrical steel sheet characterized by performing.
14 ≦ d ≦ 60 × ([% Si] +0.7 [% Mn] +4 [% P] +0.3) ^0.45 … (1)

Here, [% Si], [% Mn], and [% P] indicate the contents of Si, Mn, and P, respectively, and dn is the average of the steel sheet measured in a square region with a side length of 4 × d. The crystal grain size, K, indicates the number of measurement regions. It is a manufacturing method of the non-oriented electrical steel sheet according to claim 1, wherein the heating temperature of the steel slab is set so that the average crystal grain size d (μm) of the steel sheet satisfies the formula (3) according to the steel sheet composition. A method for producing a non-oriented electrical steel sheet characterized by adjusting the annealing temperature, the cold rolling rate, the temperature rise temperature during finish annealing, and the annealing time when performing hot-rolled sheet annealing.
18 ≦ d ≦ 40 × ([% Si] +0.7 [% Mn] +4 [% P] +0.5 ) ^0.55 … (3)   It is a manufacturing method of the non-oriented electrical steel sheet according to claim 1 or 2, wherein the heating temperature of the steel slab so that the ratio of the particle size distribution A and the crystal grain size d is 0.20 or less. A method for producing a non-oriented electrical steel sheet characterized by adjusting the annealing temperature, the cold rolling rate, the temperature rise temperature during finish annealing, and the annealing time when performing hot-rolled sheet annealing. The method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the steel slab further contains Cu: 0.2% or less and / or Cr: 1.0% or less. Method for producing an electrical steel sheet.

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