JP4718749B2 - High magnetic flux density non-oriented electrical steel sheet for rotating machine and member for rotating machine - Google Patents
High magnetic flux density non-oriented electrical steel sheet for rotating machine and member for rotating machine Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、回転機の組み立てに用いられる無方向性電磁鋼板、特に回転機のロータに組み立てたときには高磁束密度であるとともに高強度であり、ステータ用として用いるときには高磁束密度であるとともに低鉄損である、すぐれた性質を有する無方向性電磁鋼板及びそれを利用して組み立てた回転器用部材に関する。
【０００２】
【従来の技術】
回転機のエネルギー消費を低下させるには、その鉄心（ロータ及びステータ）の磁束密度を上げるとともに、低鉄損化を図ることが効果的である。このうち、鉄損を低減する手段としては、Si，Al，Mn等の含有量を高めて鉄心材料の電気抵抗を増加させる手段が一般に用いられてきた。また、これらの手段のほか、たとえば特開昭58-15143号公報のBを添加する方法、特開平3-281758号公報のNiを添加する方法等が知られている。また、電磁鋼板の集合組織を、たとえば〈100〉〈UVW〉方位を有する結晶粒を優先的に成長させたものとすることにより磁気特性を向上させる方法があり、たとえば特開昭58−181822号公報等に提案されている。この手段により回転機鉄心内の磁束流を適正化することができ、高磁束密度で低鉄損の鉄心の製造が可能になっている。
【０００３】
ところで、回転機用鉄心の製造に当たっては、材料の歩留まりを高く維持するために、一般に、同一の鋼板からロータ用鉄心板とステータ用鉄心板がプレスによって打ち抜かれる。そして、これらロータ用鉄心板とステータ用鉄心板をそれぞれ積層してロータ及びステータに組み立てることが行われる。
【０００４】
このうち、ロータは、回転部材であり、高速回転に伴う高い応力が掛かるので強度が高いことが必要とされる。特に近年においては、回転機（モータ）の効率を上げるために、希土類磁石を埋め込んだ形式のロータが発達し、ロータの回転速度は著しく高くなっている。そのため、ロータを構成する電磁鋼板に対しては磁束密度及び強度、たとえば上降伏点（YP）、が従来に比べてより高いことが要求されるようになっている。一方、ステータは、高い磁束密度を有し、かつ鉄損が低いことが回転機の小型化と省エネルギー化のため重要である。
【０００５】
【発明が解決しようとする課題】
このように、同じモータに使用される電磁鋼板であっても、ロータの組み立てに使用される鋼板（以下、「ロータ材」という）とステータの組み立てに使用される鋼板（以下、「ステータ材」という）とでは、要求特性が大きく異なる。従来提案されている技術は、ロータ材あるいはステータ材としての特性を個別に満たすものであっても、これら双方の特性を満たすように仕向けられたものではなかった。
【０００６】
本発明は、同一の鋼板からロータ材及びステータ材の同時採取をしながら、ロータ材においては高い磁束密度及び高強度を、ステータ材においては高い磁束密度及び低鉄損を達成し得る高磁束密度無方向性電磁鋼板を提案し、さらにそれを用いた回転機用部材を提案することを目的とする。
【０００７】
【課題を解決するための手段】
本発明者は、無方向性電磁鋼板の飽和磁束密度は素材の鉄の含有量（主として質量%によって表される）によって決まるものであり、鉄以外の元素、Siの含有量が高いと飽和磁束密度が低下することは避けられないこと、一方、磁束密度および強度は鋼板の結晶粒径によって支配されることに着目した。また、需要家での回転機のロータ及びステータの組み立て工程においては、鋼板からロータ用鉄心板とステータ用鉄心板を打ち抜いた後、歪取り焼鈍が行われることに着目した。さらに、Si含有量の低い無方向性電磁鋼板の結晶粒径を上記ロータおよびステータの製造プロセスにおいて適正化することによりロータおよびステータにそれぞれ必要な特性を付与できることに着目した。
【０００８】
さらに、ステータの組み立て過程で行われる歪取り焼鈍工程で結晶粒径の成長を支配する要因を探求し、AlNなどの微細析出物を抑制し、かつ鋼板中に分散する延性非金属介在物の個数密度を最終焼鈍された鋼板の平均結晶粒径と関係付けて所定値以下に制限することにより需要家でのステータの組み立て過程で行われる歪取り焼鈍工程（750℃で2時間程度）で結晶粒径を十分成長させることができることの知見を得て本発明に至った。
【０００９】
本発明の回転機用無方向性電磁鋼板は、質量比でＳｉ：０．１％〜１．２％及びＭｎ：０．００５〜０．３０％を含有し、Ｃ：０．００５０％以下（０を含む）、Ｓｏｌ．Ａｌ：０．０００４％以下（０を含む）、Ｎ：０．００２５％以下（０を含む）に制限され、残部Ｆｅ及び不可避不純物からなり、最終焼鈍された鋼板の平均再結晶粒径Ｄが６〜２５μｍであり、鋼板中に分散する粒成長阻害延性非金属介在物の個数密度が１０００個／ｃｍ２以下（０を含む）である。ここに粒成長阻害延性非金属介在物とは最終焼鈍された鋼板の平均再結晶粒径をＤとしたとき、長さが３×Ｄ〜９×Ｄの介在物をいう。また、介在物の個数は板幅方向に垂直な観察断面において１０μｍ以内の距離にある２以上の介在物が圧延方向に対して±５°以内の方向に並んでいるときは、１つの延性介在物としてみなして計測し、介在物の長さは、前記観察断面において地鉄と前記１の介在物の界面における任意の２点間で引いた線分の長さの最大値、すなわち延性介在物の両端部間の距離をいう。
【００１０】
上記発明において、質量比でSb：0.005〜0.10%およびSn：0.005〜0.2%から選んだ1種または2種をさらに含有すること、あるいは質量比でP：0.001〜0.2%およびNi：0.001〜0.2%から選んだ1種または2種をさらに含有することが好ましい。また、質量比でREM：0.0001〜0.10%およびCa：0.0001〜0.01%から選んだ1種または2種をさらに含有させることができる。
【００１１】
また、上記不可避不純物のうちS及びOは、質量比でS：0.0050%以下（0を含む）、0：0．0100%以下（0を含む）に制限されていることが好ましい。同様に上記不可避不純物のうちTi、Nb及びVが質量比でTi：0.0020%以下（0を含む）、Nb：0.0050%以下（0を含む）、およびV：0.0060%以下（0を含む）に制限されていることが好ましい。
【００１３】
上記各発明に係る無方向性電磁鋼板は、無方向性電磁鋼板用スラブを常法により処理して最終板厚を有する冷延鋼板とした後、700〜800℃で最終焼鈍を施してなるものが好ましい。
【００１４】
上記各発明に係る無方向性電磁鋼板は、打ち抜き後、積層して回転機ロータ部材とすることができる。また、打ち抜き後、積層した後さらに歪取り焼鈍を施して回転機ステータ部材とすることもできる。
【００１５】
また上記各発明に係る無方向性電磁鋼は、無方向性電磁鋼板用スラブを常法により処理して最終板厚を有する冷延鋼板とした後、700〜800℃で最終焼鈍を施し、これにさらに700〜800℃で歪取り焼鈍を施して結晶粒径を最終焼鈍後の粒径の2倍以上に成長させたものとすることもできる。
【００１６】
【発明の実施の形態】
本発明の電磁鋼板は、質量比で以下の化学組成を有する。
【００１７】
Si：0.1〜1.2%
鋼板の電気抵抗を増大させ、鉄損を低減するには、少なくとも0.1%のSiを含有させる必要があるが、Si含有量が1.2%を超えると、磁束密度が低下するだけでなく、硬度が上昇し、加工性が劣化する。したがって、Si含有量は0.1〜1.2%の範囲とする。
【００１８】
Mn：0.005〜0.30%
Mnは良好な熱間圧延の際の加工性を得るために必要な成分であり、そのためには0.005%以上含有させることが必要である。しかし、0.30%を超えると磁束密度が低下する。したがってMnの含有量は0.005〜0.30%とする。
【００１９】
C：0.0050%以下（0を含む）
Cは、磁気時効劣化を抑制するためには極力低くする必要がある。また、本発明で採用される極低Al化の条件の下で集合組織の改善効果を十分に発揮させるためには、0.0050%以下に低減する必要がある。しかしながら、このCの低減は、必ずしも出発材料である溶鋼あるいはスラブの段階で達成されていなければならないものではなく、鋼板の製造過程中最終焼鈍を行うまでに達成されればよい。
【００２０】
Sol.Al：0．0004%以下（0を含む）
優れた粒成長性と磁気特性を得るためには、鋼板のAl量を0.0004%以下に低減することが必要である。Al含有量が0.0004%を超えると鋼板中にAlNが析出し、最終焼鈍された製品の磁束密度が低下する。また、ステータに打ち抜き後に行われる歪取り焼鈍の際の粒成長性が阻害され、鉄損値を十分低下させることができなくなる。
【００２１】
Ｎ：０．００２５％以下（０を含む）
ＮはＡｌと結合して窒化物（ＡｌＮ）の析出原因となるほか、Ｔｉ等と結合して種々の窒化物を形成し、最終焼鈍された製品の磁束密度を低下させる原因になる。また、ステータに打ち抜き後行われる歪取り焼鈍の際の粒成長性を阻害し、鉄損値の十分な低下を阻害する原因になる。そのためＮ量は０．００２５％以下に低減させることが必要である。
【００２２】
本発明の無方向性電磁鋼板は、以上の基本組成を有するが、それだけでは本発明の目的を達成し得ない。最終焼鈍された鋼板中に分散する粒成長阻害延性非金属介在物、すなわち延性非金属介在物のうち鋼板の平均再結晶粒径をDとしたとき、長さが3×D〜9×Dの延性非金属介在物の個数密度が1000個/cm2以下（0を含む）であることが必要である。
【００２３】
ここに、平均再結晶粒径とは、鋼板の0.5mm2の面積中に存在する結晶粒の個数を測定し、それに基づいて結晶粒1個あたりの平均面積を算出し、その平均面積に等しい円の直径をいう。この平均結晶粒径は鋼板の板幅方向に垂直な断面を光学顕微鏡で観察することにより測定される。
【００２４】
延性非金属介在物とは、圧延方向に長く延びた棒状の介在物及び圧延方向に連続して並ぶ介在物をいう。また、板幅方向に垂直な断面観察において１０μｍ以内の距離にある２以上の介在物が圧延方向に対して±５°以内の方向に並んでいるときは、これらの介在物を繋がっているものととして１の延性介在物とみなす。
【００２５】
延性介在物の長さとは、板幅方向に垂直な断面観察において地鉄と介在物の界面における任意の２点間で引いた線分の長さの最大値、すなわち延性介在物の両端部間の距離をいう。その存在個数の測定は、鋼板の板幅方向に垂直な断面を研磨し、研磨まま（腐食処理等は行わずに）の面を光学顕微鏡で観察し、地鉄部分と色が異なる小さな領域を介在物と認定し、１つの試料に対しての観察視野を５ｍｍ２として上記により認定した介在物のうち延性介在物と認められるものの個数を計測し１ｃｍ２当たりに割り戻して個数密度とする。介在物には上記延性介在物のほかに孤立した円形の介在物があるが、これは非延性介在物として延性介在物にはカウントしない。
【００２６】
（実験１）
C：0.002%、Si：0.7%、Mn：0.2%、Sol.Al：0.0004%以下、S：0.002%、残部不可避不純物を基本成分とし、これにNを0.0010〜0.0060%の範囲で変更したスラブを製造した。得られたスラブを1100℃に加熱し2.3mm厚まで熱延したのち、酸洗し、冷間圧延して0.35mmの最終板厚に仕上げ、さらに、800℃、15秒間の再結晶焼鈍を施して最終焼鈍板（製品）とした。なお、延性介在物の存在量、及び形態（長さ）の調整は、たとえば、酸素含有量とAl含有量の変更や熱間圧延での圧下スケジュールを変えることによって行った。
【００２７】
得られた製品について平均結晶粒径の測定を行うとともに介在物の観察を行って延性介在物の長さ及び個数密度を測定した。ついで、上記製品に対し、需要家での歪取り焼鈍に相当する条件であるアルゴン（Ar）雰囲気にて750℃、2時間の焼鈍（以下、単に「歪取り焼鈍」という）を施し、最終焼鈍板と同様平均結晶粒径の測定を行った。
【００２８】
図１はこのようにして得られた最終焼鈍後の鋼板の平均結晶粒径に対する歪取り焼鈍後の鋼板の平均結晶粒径の比（以下「歪取り焼鈍結晶粒成長比」という）とN含有量の関係を、平均再結晶粒径をDとしたとき、長さが3×D〜9×Dの介在物（以下「粒成長阻害延性介在物」という）の個数密度をパラメータとして表したグラフである。
【００２９】
図１から分かるように、N含有量が0.0030%以下のとき、粒成長阻害延性介在物の個数密度が、1000個／cm2以下であれば、歪取り焼鈍結晶粒成長比が2以上となる。しかしながら、粒成長阻害延性介在物の個数密度が、1000個／cm2以下であっても、N含有量が0.0030%を超えるとき、あるいは粒成長阻害延性介在物の個数密度が、1000個/cm2を超えるときは、歪取り焼鈍結晶粒成長比が2未満となる。
【００３０】
（実験2）
同様の結果が次の実験２からも確かめられる。表１に示す組成を有する厚さ250mmのスラブを3本製造し、これらのスラブから機械加工により、厚さが25、50、100、200mm厚さになるように試料をそれぞれ切り出した。その後、これらの試料を1070℃に加熱後、熱間圧延にて2.5mmとした後、酸洗してから冷間圧延によって最終板厚0.5mmに仕上げた。ついで、再結晶焼鈍条件を700〜800℃の範囲で調整し、製品板の結晶粒径が12μmまたは14μmである製品板とした。
【００３１】
得られた製品板にはAr雰囲気中で750℃、2時間の歪取り焼鈍を施した。これらの製品板（再結晶焼鈍板）および歪取り焼鈍板の板幅方向に垂直な断面を光学顕微鏡で観察し、その平均結晶粒径を測定した。また、製品板については粒成長阻害延性介在物の個数密度を測定した。その結果を表２に示す。同表に示したように、製品板の粒成長阻害延性介在物の個数密度が1000個/cm2以下である試料では、歪取り焼鈍結晶粒成長比が大きい。
【００３２】
【表１】
【表２】
上記により組成を制限し、かつ粒成長阻害延性介在物の個数密度を適正に制限すれば、歪取り焼鈍後の鋼板（ステータに組み上げられた鉄心材料）の平均結晶粒径を前記最終焼鈍後の粒径の2倍以上とすることができる。これによりステータにおける鉄損は大きく低減される。一方、ロータは最終焼鈍された状態の結晶粒が前記のように相対的に小さい状態の鋼板で組み立てられるから、その状態で使用することにより、強度、特に上降伏点（YP）を高く維持することができ、高速回転用の回転機を効率的に組み立てることが可能になる。
【００３５】
鋼板強度を支配する平均結晶粒径の大きさは、回転機の特性に応じて要求されるロータの強度レベルに応じて設計すればよい。しかしながら、一般的な回転機であれば鋼板の最終焼鈍後における平均結晶粒径は6〜25μmが好適である。
【００３６】
なお、本発明の権利範囲の解釈に影響を与えるものではないが、粒成長阻害延性介在物の個数密度によって歪取り焼鈍結晶粒成長比が支配される理由は以下のように考えられる。
【００３７】
まず、結晶粒径と同程度の長さの介在物が、最も粒成長性を阻害すると考えられるからである。すなわち、延性介在物は一つの、あるいは二つ以上の結晶粒界を横切って存在し、その結晶粒の成長性を阻害する確率が高くなる。しかしながら、電磁鋼板中に存在する非金属介在物の総量が一定の場合は、その鋼中に占める体積分率はほぼ一定と見られるので、ツェナー（Zener）の式の示すところにより、結晶粒径に比べて極端に長い介在物は粒成長性を阻害する可能性が低くなる。いいかえれば、延性介在物が粒成長性を阻害する程度は、介在物の長さによって異なり、本発明者等の知見では延性非金属介在物の長さが最終焼鈍板の平均結晶粒の3〜9倍であるとき、すなわち粒成長阻害延性介在物のとき、最大となるのである。一方、非金属介在物の量は、直接、結晶粒の成長性を支配する。したがって、この範囲の長さの延性非金属介在物、すなわち「粒成長阻害延性介在物」の個数密度により「歪取り焼鈍結晶粒成長比」が影響を受けるのである。
【００３８】
上記のように、無方向性電磁鋼板のSi、Mn、C、Sol.Al及びN含有量を制限しさらに粒成長阻害延性介在物の個数密度を1000個/cm2以下に押さえることによって歪取り焼鈍結晶粒成長比を大きくとることができ、回転機用に適した高磁束密度無方向性電磁鋼板とすることができるが、鋼板組成においてTi、Nb及びV、さらにSb、Snを制限あるいは添加することにより、その効果を一層確実にすることができる。そのことは、以下の実験により確認できた。
【００３９】
（実験３）
表３に示す組成からなる鋼塊を製造し、これらの鋼塊を1070℃に加熱後、熱間圧延にて2.5mmとした後、酸洗してから冷間圧延によって最終板厚0.5mmに仕上げた。ついで、800℃、10秒間の再結晶焼鈍をおこない製品板としたのち、750℃、2時間の歪取り焼鈍を施して製品板とした。得られた製品板および歪取り焼鈍後の製品板から、圧延方向と平行および圧延方向に直角に、それぞれサンプルを切りだし、JIS C 2550に準拠して磁束密度および鉄損を測定し、それらの平均値を求めた。測定結果は表３に併せて示す。
【００４０】
【表３】
表３から分かるように、Tiを0.0020%以下、Nbを0.0050%以下、およびV量を0．0060%以下に制限することによって歪取り焼鈍後の磁気特性を一層良好にすることができる。また、SbまたはSnの1種または2種を添加することによって、歪取り焼鈍後の鉄損が大幅に改善できる。Ti、NbおよびV量を低減することによって、磁気特性が改善する理由は必ずしも明らかでないが、TiおよびNb、そしてVはともに窒化物形成元素であり、これらの窒化物が微細に析出すると、集合組織形成および結晶粒成長性に悪影響を及ぼす微細析出AlNと同様の害を与えるため、これらの元素を低減することによってこの種の害が防止される結果、良好な磁気特性が得られるものと考えられる。
【００４２】
歪取り焼鈍後の磁気特性に影響を及ぼす理由も明らかではないが、低Alの含Si鋼にTi、NbおよびV量が多いと、熱延板焼鈍や再結晶焼鈍時に部分的に固溶した窒化物または炭化物が、歪取り焼鈍時に窒化物または炭化物として析出し、磁壁の移動を阻害する結果、鉄損の劣化が生じるものと考えられる。
【００４３】
また、SbまたはSnの1種または2種を添加することによって、歪取り焼鈍後の鉄損が大幅に改善される理由も明らかではないが、SbやSnの偏析がV等の析出挙動に影響を与え、析出の抑制と析出物の粗大化が起こるためであると考えられる。
【００４４】
このように溶銑やSi原料から不可避的にに混入する、Ti，NbおよびVの量を制限することによって、上記したSol.Alの低減による効果が一層高まるとともに、磁気特性のさらなる向上が達成される。特に、Alを極力低減した成分系では、TiおよびNb量の制限に加えて、V量を制限することが有利である。その効果は、特に歪取り焼鈍後の鉄損のが劣化防止において大きい。上記微量元素の制限についてまとめると以下のとおりである。
【００４５】
Ti：0.0020%以下（0を含む）、Nb：0.0050%以下（0を含む）、およびV：0.0060%以下（0を含む）
Ti、NbおよびVは、微細な窒化物又は炭化物を形成して、集合組織の形成および結晶粒の成長性を阻害する。特に本発明にしたがい、Sol.Al及びN含有量を低く制限した無方向性電磁鋼板ではその傾向が著しい。これら元素をそれぞれTi：0.0020%以下、Nb：0.0050%以下、V：0.0060%以下に低減すれば、その窒化物又は炭化物形成傾向が抑制されて、特に歪取り焼鈍後の鉄損の劣化が防止できる。
【００４６】
Sb：0.005〜0.10%およびSn：0.005〜0.2%から選んだ1種または2種
SbおよびSnは、窒化物の微細析出を抑制するとともにその粒成長阻害効果を低減することにより、磁気特性上有利な集合組織の形成を効果的に促進させる。その効果はSb：0.005%以上、Sn：0.005%以上で現れるが、それぞれ0.10%超え、0.2%超えでは却って粒成長性を阻害する。
【００４７】
上記のほか、下記の元素を制限あるいは添加することにより本発明鋼の特性をより効果的に発揮させることができる。
【００４８】
P：0.001〜0.2%およびNi：0.001〜0.2%から選んだ1種または2種
本発明の無方向性電磁鋼板は、低Siであるためその硬度が低く、打ち抜きの際にダレやつぶれが発生したり、打ち抜き時に発生するカエリが大きくなって鋼板の占積率を低下させる等の問題が発生するおそれがある。Ｐ及びNiは電磁鋼板の硬度を上昇させる効果がある。したがって、電磁特性、特に磁束密度を害しない範囲内で需要家の要求に応じこれら元素を添加することができる。
【００４９】
REM：0.0001〜0.10%およびCa：0.0001〜0.01%から選んだ1種または2種
REMやCaは硫化物を粗大化して鉄損を向上する作用を有する。したがって、これら元素をその効果の発現範囲、すなわちREM：0.0001〜0.10%、Ca：0.0001〜0.01%において適宜添加することができる。
【００５０】
S：0.0050%以下（0を含む）、0：0．0100%以下（0を含む）
Sは、0.0050%を超えると、MnやトランプエレメントのCuなどと結合してMnSやCu2Sを形成する傾向が強くなり、結晶粒成長を妨げる。また、Oは、0.0100%を超えると酸化物が増え、結晶粒成長を妨げる。したがってこれら元素は上記範囲内に制限するのが好ましい。
【００５１】
本発明においては、最終焼鈍された鋼板の結晶粒径は、無方向性電磁鋼板に要求される強度レベル、鉄損レベルが、製造される回転機の特性によって変化するので一律に決定する必要はない。しかしながら、平均再結晶粒径Dを6〜25μmとすることは、先に述べた歪取り焼鈍結晶粒成長比を比較的大きく、たとえば、3以上とすることに有利に作用する。
【００５２】
上記本発明に係る無方向性電磁鋼板の製造方法は、特に制限されない。代表的には、下記のプロセスによって製造することができる。まず、好適成分組成に調整された溶鋼を連続鋳造法によってスラブする。ついで、これを熱間圧延して熱延板とする。これに必要に応じて熱延板焼鈍した後、必要に応じて中間焼鈍を挟んで1回以上の冷間圧延を施して最終板厚に仕上げる。得られた冷延板に連続焼鈍を施した上で必要に応じて絶縁コーティングを施す。
【００５３】
本発明においては介在物のうち延性介在物の量、及び存在形態、特に平均結晶粒径に対する長さが所定範囲内となる延性介在物を低減すること、すなわち粒成長阻害延性介在物の量を1000個/cm2以下にすることが肝要である。このようなコントロールは以下の手段のいずれか一又はそれらの組み合わせによって達成することができる。
【００５４】
まず、酸素含有量を低減することによりスラブ中の介在物の絶対量を減少させる手段がある。また、スラブ中の介在物をAlやMn量の増加により延性化させたり、逆にAlやMn量の低減により非延性化（微細化）させる手段が有効である。さらに、熱延以後の累積圧下率が大きくなれば延性介在物は長くなり小さくなれば短くなる傾向にあるので、スラブ圧下率を増減、あるいは製品板厚の増減により非金属介在物の長さを調整して最終焼鈍された鋼板の平均再結晶粒径の3倍未満または9倍超とすることもできる。逆に最終焼鈍での温度や均熱時間等の条件を変更して平均結晶粒径を増減させ、その結果として非金属介在物の長さを平均結晶粒径の3倍未満または9倍超とすることもできる。
【００５５】
また、上記製造プロセスにおいて、最終板厚に冷間圧延した冷延板に施す連続焼鈍の焼鈍温度を700〜800℃とすることは、平均結晶粒径を6〜25μmに調整し、あるいは鋼板の硬度を適当なレベル、たとえばビッカース硬さ（Hv）を100〜170に調整するのに好ましい。
【００５６】
このようにして製造された無方向性電磁鋼板は、回転機用の鉄心に打ち抜き、ロータ及びステータに組み立てることができる。その際、同一の鋼板からロータとステータようの鉄心材料を同時に打ち抜き、それぞれ積層してロータ及びステータ部材に組み立てた後、ステータ部材にのみ歪取り焼鈍を施して、粒成長を促し、その鉄損を下げることができる。この歪取り焼鈍の条件は、歪取り焼鈍結晶粒成長比が2以上になるものであればよいが、たとえば不活性ガス雰囲気中で750℃、2時間程度とすることが望ましい。この際、ロータ用鉄心部材には粒成長を伴う歪取り焼鈍は行わず、高い強度を保ったままにするのがよい。
【００５７】
なお、最終焼鈍された無方向性電磁鋼板には、さらに軽度の歪み、たとえば0.5〜5%程度の圧延歪みを付与した後、700〜800℃の歪取り焼鈍を施し、再結晶を促して結晶粒径を30〜100μmに成長させることができる。このように処理された鋼板は、特に低鉄損が要求されるステータの組み立てに利用することができる。
【００５８】
【実施例】
以下、実施例に基づき本発明の実施形態をより具体的にする。
【００５９】
（実施例１）
表４に示す成分組成を有するスラブを連続鋳造法により製造した。これらのスラブを1110℃で40分間加熱した後、仕上圧延を行い厚さ2.5mmの熱延板とした。得られた熱延板を酸洗し、スケール除去を施してから冷間圧延により厚さ0.50mmの冷延板に仕上げた。ついで、容量比で水素：50%と窒素：50%の雰囲気中で、780℃、10秒の最終焼鈍を施した。得られた最終焼鈍板には重クロム酸塩と樹脂からなる半有機コーティング液を塗布し、300℃で焼きつけて最終製品とした。なお、粒成長阻害延性介在物の量は、スラブ厚さの変更や熱間圧延での圧下スケジュールの変更によって変動させた。
【００６０】
得られた製品からサンプルを切出し、JIS C2550に準拠して磁束密度、鉄損、上降伏点（YP）およびビッカース硬さ（Hv）を測定した。また、平均結晶粒径および粒成長阻害延性介在物の個数密度を測定した。なお、測定は幅方向に垂直な面について行った。
【００６１】
ついで、上記製品をアルゴン雰囲気中にて750℃、2時間の歪取り焼鈍を行ったのち、前記製品について行ったのと同様にして鉄損および平均結晶粒径を測定するとともに、歪取り焼鈍結晶粒成長比を求めた。
【００６２】
【表４】
得られた結果を表５に示す。表４及び表５に示すように、本発明にしたがう成分組成及び粒成長阻害介在物個数密度を有するものは歪取り焼鈍結晶粒成長比が大きく、製品（最終焼鈍状態）の上降伏点（YP）およびビッカース硬さ（Hv）が比較的高いことと相俟って、回転機のロータ及びステータを同時に打ち抜いて製作するのに適したものとなっている。
【００６４】
【表５】
（実施例２）
表６に示す成分組成を有する厚さ210mmの連続鋳造スラブを製造した。その際、製鋼プロセスにおけるスラグ組成の適正化と成分組成によるスラブ厚および熱延条件の適正化により結晶粒阻害延性介在物量が1000個/cm2の範囲に収まるようにした。得られたスラブを実施例１の場合と同様に処理して製品とし、実施例１の場合と同様に試験した。ただし、鋼記号58の最終焼鈍は680℃、鋼記号59の最終焼鈍は850℃で行った。得られた結果を表７に示す。表７に示したとおり、本発明にしたがう成分組成、平均結晶粒径を有するものはいずれも優れた歪取り焼鈍結晶粒成長比を有し、それにより回転機のロータ及びステータの同時打ち抜き製造に適したものとなっている。
【００６６】
【表６】
【表７】
上記のように本発明により、回転機用ロータ及びステータを製造するのに極めて適した無方向性電磁鋼板を提供できる。しかしながら、本発明に係る無方向性電磁鋼板は、それに留まらず、いわゆるリサイクル性が優れているという特徴を有する。すなわち、鋼板のAl含有量が高いときは、鉄心材料をリサイクルしてモータのシャフトなどを鋳造する場合、溶鋼の表面酸化が進行して粘性が増大して溶鋼の鋳型内充填性が低下するために、健全な鋳物が得られないことがあり、一般にAlを含むスクラップはリサイクル性に乏しいとされていたが、本発明に係る無方向性電磁鋼板は低Al材であり、鋳造のためのリサイクル性は極めて高い。
【００６９】
【発明の効果】
本発明にしたがう高磁束密度無方向性電磁鋼板により、同一の鋼板からロータ材及びステータ材の同時採取をしながら、ロータ材には高い磁束密度及び高強度を、ステータ材には高い磁束密度及び低鉄損を付与し得る。これにより、回転機用部材、ひいては回転機の製造効率、出力特性を大幅に向上し得る。併せて、本発明に係る無方向性電磁鋼板は、鋳造の際のリサイクル性に優れ、打ち抜き材のスクラップをリサイクルする場合の鋳造性が改善される。
【図面の簡単な説明】
【図１】 最終焼鈍後の鋼板の平均結晶粒径に対する歪取り焼鈍後の鋼板の平均結晶粒径の比とN含有量の関係を粒成長阻害延性非金属介在物の存在個数をパラメータとして表したグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-oriented electrical steel sheet used for assembling a rotating machine, particularly high magnetic flux density and high strength when assembled on a rotor of a rotating machine, and high magnetic flux density and low iron when used for a stator. The present invention relates to a non-oriented electrical steel sheet having excellent properties that is a loss and a member for a rotator assembled using the non-oriented electrical steel sheet.
[0002]
[Prior art]
In order to reduce the energy consumption of the rotating machine, it is effective to increase the magnetic flux density of the iron core (rotor and stator) and to reduce the iron loss. Among these, as means for reducing the iron loss, means for increasing the electric resistance of the iron core material by increasing the content of Si, Al, Mn and the like has been generally used. In addition to these means, for example, a method of adding B in JP-A-58-15143 and a method of adding Ni in JP-A-3-281758 are known. Further, there is a method for improving magnetic properties by preferentially growing crystal grains having a <100><UVW> orientation, for example, in the texture of an electromagnetic steel sheet. For example, Japanese Patent Laid-Open No. 58-181822 It is proposed in the gazette. By this means, the magnetic flux flow in the rotating machine iron core can be optimized, and a high magnetic flux density and low iron loss iron core can be manufactured.
[0003]
By the way, when manufacturing the iron core for a rotating machine, in order to keep the material yield high, generally, the rotor iron core plate and the stator iron core plate are punched out of the same steel plate by a press. Then, the rotor core plate and the stator core plate are laminated and assembled into the rotor and the stator.
[0004]
Among these, the rotor is a rotating member and is required to have high strength because high stress is applied due to high-speed rotation. Particularly in recent years, in order to increase the efficiency of a rotating machine (motor), a rotor of a type embedded with a rare earth magnet has been developed, and the rotational speed of the rotor has been remarkably increased. For this reason, the magnetic steel sheets constituting the rotor are required to have a higher magnetic flux density and strength, for example, an upper yield point (YP), as compared with the prior art. On the other hand, the stator has a high magnetic flux density and a low iron loss is important for miniaturization and energy saving of the rotating machine.
[0005]
[Problems to be solved by the invention]
In this way, even steel sheets used for the same motor, steel plates used for rotor assembly (hereinafter referred to as “rotor material”) and steel plates used for stator assembly (hereinafter referred to as “stator material”). The required characteristics are very different. Conventionally proposed technologies have not been designed to satisfy both of these characteristics, even if the characteristics of the rotor material or the stator material are individually satisfied.
[0006]
The present invention provides a high magnetic flux density capable of achieving high magnetic flux density and high strength in the rotor material and high magnetic flux density and low iron loss in the stator material while simultaneously collecting the rotor material and the stator material from the same steel plate. It aims at proposing a non-oriented electrical steel sheet and further proposing a member for a rotating machine using the same.
[0007]
[Means for Solving the Problems]
The present inventor has determined that the saturation magnetic flux density of the non-oriented electrical steel sheet is determined by the content of iron (mainly expressed by mass%) of the material. If the content of elements other than iron and Si is high, the saturation magnetic flux It was noticed that a decrease in density was inevitable, while magnetic flux density and strength were governed by the crystal grain size of the steel sheet. Further, in the assembly process of the rotor and the stator of the rotating machine at the customer, attention was paid to the fact that after the rotor core plate and the stator core plate are punched from the steel plate, the strain relief annealing is performed. Furthermore, the inventors focused on the fact that the rotor and stator can each have the necessary characteristics by optimizing the crystal grain size of the non-oriented electrical steel sheet having a low Si content in the rotor and stator manufacturing processes.
[0008]
In addition, the number of ductile non-metallic inclusions that suppress the fine precipitates such as AlN and are dispersed in the steel sheet are investigated by investigating the factors governing the growth of crystal grain size in the stress relief annealing process performed in the stator assembly process. Grain grains in the stress relief annealing process (approximately 2 hours at 750 ° C) performed in the stator assembly process at the customer by restricting the density to a predetermined value or less in relation to the average crystal grain size of the final annealed steel sheet Obtaining knowledge that the diameter can be sufficiently grown, the present invention has been achieved.
[0009]
The non-oriented electrical steel sheet for rotating machines of the present invention contains Si: 0.1% to 1.2% and Mn: 0.005 to 0.30% by mass ratio, and C: 0.0050% or less ( 0), Sol. Al: 0.0004% or less (including 0), N: 0.0025 % Or less (including 0), consisting of the balance Fe and inevitable impurities, The average recrystallized grain size D of the finally annealed steel sheet is 6 to 25 μm, The number density of the grain growth-inhibiting ductile nonmetallic inclusions dispersed in the steel sheet is 1000 / cm. 2 The following (including 0). Here, the grain growth-inhibiting ductile nonmetallic inclusion means an inclusion having a length of 3 × D to 9 × D, where D is the average recrystallized grain size of the finally annealed steel sheet. The number of inclusions is one ductile inclusion when two or more inclusions at a distance of 10 μm or less in the observation cross section perpendicular to the sheet width direction are arranged in a direction within ± 5 ° with respect to the rolling direction. The length of the inclusion is the maximum value of the length of the line segment drawn between any two points at the interface between the ground iron and the one inclusion in the observation section, that is, the ductile inclusion. The distance between both ends.
[0010]
In the said invention, it further contains 1 type or 2 types selected from Sb: 0.005-0.10% and Sn: 0.005-0.2% by mass ratio, or P: 0.001-0.2% and Ni: 0.001-0.2 by mass ratio It is preferable to further contain one or two selected from%. Moreover, 1 type or 2 types selected from REM: 0.0001-0.10% and Ca: 0.0001-0.01% by mass ratio can further be contained.
[0011]
Of the above inevitable impurities, S and O are preferably limited by mass ratio to S: 0.0050% or less (including 0) and 0: 0.0100% or less (including 0). Similarly, among the above inevitable impurities, Ti, Nb and V are in mass ratios of Ti: 0.0020% or less (including 0), Nb: 0.0050% or less (including 0), and V: 0.0060% or less (including 0) It is preferably limited.
[0013]
The non-oriented electrical steel sheets according to the above inventions are obtained by subjecting a slab for non-oriented electrical steel sheets to a cold-rolled steel sheet having a final thickness by subjecting the slab to a final annealing at 700 to 800 ° C. Is preferred.
[0014]
The non-oriented electrical steel sheets according to the above inventions are laminated after punching. Rotating machine rotor member It can be. In addition, after punching, laminating, and then applying strain relief annealing Rotating machine stator member It can also be.
[0015]
Further, the non-oriented electrical steel according to each of the above inventions is obtained by subjecting a slab for non-oriented electrical steel sheets to a cold-rolled steel sheet having a final thickness by subjecting the slab to a final annealing at 700 to 800 ° C. Further, strain relief annealing is performed at 700 to 800 ° C., and the crystal grain size can be grown to more than twice the grain size after the final annealing.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The electrical steel sheet of the present invention has the following chemical composition in mass ratio.
[0017]
Si: 0.1-1.2%
In order to increase the electrical resistance of the steel sheet and reduce iron loss, it is necessary to contain at least 0.1% Si. However, if the Si content exceeds 1.2%, not only the magnetic flux density is lowered, but also the hardness is reduced. As a result, the processability deteriorates. Therefore, the Si content is in the range of 0.1 to 1.2%.
[0018]
Mn: 0.005-0.30%
Mn is a component necessary for obtaining good workability in hot rolling, and for that purpose, it is necessary to contain 0.005% or more. However, if it exceeds 0.30%, the magnetic flux density decreases. Therefore, the Mn content is set to 0.005 to 0.30%.
[0019]
C: 0.0050% or less (including 0)
C must be made as low as possible in order to suppress magnetic aging degradation. Further, in order to sufficiently exhibit the texture improvement effect under the extremely low Al condition employed in the present invention, it is necessary to reduce it to 0.0050% or less. However, this reduction in C does not necessarily have to be achieved at the stage of the molten steel or slab, which is the starting material, but may be achieved by the final annealing during the manufacturing process of the steel sheet.
[0020]
Sol.Al: 0.004% or less (including 0)
In order to obtain excellent grain growth and magnetic properties, it is necessary to reduce the Al content of the steel sheet to 0.0004% or less. When the Al content exceeds 0.0004%, AlN precipitates in the steel sheet, and the magnetic flux density of the final annealed product decreases. Further, the grain growth property at the time of the stress relief annealing performed after punching into the stator is hindered, and the iron loss value cannot be sufficiently reduced.
[0021]
N: 0.0025 % Or less (including 0)
N combines with Al to cause precipitation of nitride (AlN), and also combines with Ti and the like to form various nitrides and to reduce the magnetic flux density of the final annealed product. Moreover, the grain growth property at the time of the stress relief annealing performed after being punched into the stator is hindered, and this causes a sufficient decrease in the iron loss value. for that reason N amount is 0.0025% or less It is necessary to reduce it.
[0022]
Although the non-oriented electrical steel sheet of the present invention has the above basic composition, the object of the present invention cannot be achieved by itself. Grain growth inhibition ductile non-metallic inclusions dispersed in the final annealed steel sheet, that is, the average recrystallized grain size of the steel sheet among the ductile non-metallic inclusions is 3 × D to 9 × D. The number density of ductile non-metallic inclusions is 1000 / cm 2 The following (including 0) is required.
[0023]
Here, the average recrystallization grain size is 0.5mm of steel sheet 2 The number of crystal grains existing in the area is measured, the average area per crystal grain is calculated based on the number, and the diameter of a circle equal to the average area is said. The average crystal grain size is measured by observing a cross section perpendicular to the plate width direction of the steel sheet with an optical microscope.
[0024]
The ductile non-metallic inclusions refer to rod-like inclusions extending in the rolling direction and inclusions continuously arranged in the rolling direction. Also, In cross-sectional observation perpendicular to the plate width direction When two or more inclusions at a distance of 10 μm or less are aligned in a direction within ± 5 ° with respect to the rolling direction, these inclusions are regarded as being connected as one ductile inclusion.
[0025]
What is the length of ductile inclusions? In cross-sectional observation perpendicular to the plate width direction The maximum value of the length of the line segment drawn between any two points at the interface between the ground iron and the inclusions, that is, the distance between both ends of the ductile inclusions. The number of the existing pieces is measured by polishing a cross section perpendicular to the plate width direction of the steel sheet, observing the polished surface (without performing corrosion treatment, etc.) with an optical microscope, Accredited as inclusions, 5 mm observation field for one sample 2 The number of inclusions recognized as ductile inclusions among the inclusions certified as described above was measured as 1 cm. 2 The number density is divided back to the hit. In addition to the above-described ductile inclusions, there are isolated circular inclusions, which do not count as ductile inclusions as non-ductile inclusions.
[0026]
(Experiment 1)
C: 0.002%, Si: 0.7%, Mn: 0.2%, Sol.Al: 0.0004% or less, S: 0.002%, the remainder unavoidable impurities are the basic components, and N is changed within the range of 0.0010 to 0.0060% Manufactured. The resulting slab was heated to 1100 ° C and hot-rolled to 2.3mm thickness, pickled, cold-rolled to a final thickness of 0.35mm, and further subjected to recrystallization annealing at 800 ° C for 15 seconds. The final annealed plate (product). The amount of ductile inclusions and the form (length) were adjusted by, for example, changing the oxygen content and Al content or changing the rolling schedule during hot rolling.
[0027]
For the obtained product, the average crystal grain size was measured and the inclusions were observed to measure the length and number density of the ductile inclusions. Next, the above products are annealed at 750 ° C for 2 hours in the argon (Ar) atmosphere, which is the condition equivalent to the strain relief annealing at the customer (hereinafter simply referred to as "strain relief annealing"), and finally annealed. The average crystal grain size was measured in the same manner as the plate.
[0028]
FIG. 1 shows the ratio of the average crystal grain size of the steel plate after strain relief annealing to the average crystal grain size of the steel plate after final annealing thus obtained (hereinafter referred to as “strain relief annealed crystal grain growth ratio”) and N content. A graph showing the quantity relationship, with the number density of inclusions having a length of 3 × D to 9 × D (hereinafter referred to as “grain growth-inhibiting ductile inclusions”) as a parameter when the average recrystallized grain size is D It is.
[0029]
As can be seen from FIG. 1, when the N content is 0.0030% or less, the number density of the grain growth inhibiting ductile inclusions is 1000 / cm. 2 If it is below, the strain relief annealing crystal grain growth ratio is 2 or more. However, the number density of grain growth inhibiting ductile inclusions is 1000 / cm. 2 Even when the N content exceeds 0.0030% or the number density of the grain growth inhibiting ductile inclusions is 1000 / cm 2 When it exceeds, the strain relief annealing crystal grain growth ratio is less than 2.
[0030]
(Experiment 2)
Similar results can be confirmed from Experiment 2 below. Three 250 mm-thick slabs having the composition shown in Table 1 were manufactured, and samples were cut from these slabs to a thickness of 25, 50, 100, and 200 mm by machining. Thereafter, these samples were heated to 1070 ° C., hot rolled to 2.5 mm, pickled, and then finished to a final thickness of 0.5 mm by cold rolling. Subsequently, the recrystallization annealing conditions were adjusted in the range of 700 to 800 ° C. to obtain a product plate having a crystal grain size of 12 μm or 14 μm.
[0031]
The obtained product plate was subjected to strain relief annealing at 750 ° C. for 2 hours in an Ar atmosphere. Cross sections perpendicular to the plate width direction of these product plates (recrystallized annealed plates) and strain relief annealed plates were observed with an optical microscope, and the average crystal grain size was measured. For the product plate, the number density of the grain growth-inhibiting ductile inclusions was measured. The results are shown in Table 2. As shown in the table, the number density of grain growth-inhibiting ductile inclusions on the product plate is 1000 / cm. 2 In the following samples, the strain relief annealing crystal grain growth ratio is large.
[0032]
[Table 1]
[Table 2]
If the composition is limited by the above and the number density of the grain growth-inhibiting ductile inclusions is appropriately limited, the average crystal grain size of the steel plate after the strain relief annealing (the iron core material assembled in the stator) is determined after the final annealing. The particle size can be 2 or more times the particle size. Thereby, the iron loss in the stator is greatly reduced. On the other hand, since the rotor is assembled with the steel plate having a relatively small crystal grain in the final annealed state as described above, the strength, particularly the upper yield point (YP), is maintained high when used in that state. This makes it possible to efficiently assemble a rotating machine for high-speed rotation.
[0035]
What is necessary is just to design the magnitude | size of the average grain size which controls steel plate intensity | strength according to the strength level of the rotor requested | required according to the characteristic of a rotary machine. However, in the case of a general rotating machine, the average grain size after the final annealing of the steel sheet is preferably 6 to 25 μm.
[0036]
Although not affecting the interpretation of the scope of rights of the present invention, the reason why the strain relief annealing crystal grain growth ratio is governed by the number density of grain growth inhibiting ductile inclusions is considered as follows.
[0037]
First, it is because inclusions having the same length as the crystal grain size are considered to most inhibit the grain growth. That is, the ductile inclusions exist across one or more crystal grain boundaries, and the probability of inhibiting the growth of the crystal grains becomes high. However, when the total amount of non-metallic inclusions present in the electrical steel sheet is constant, the volume fraction of the steel is considered to be almost constant. Therefore, according to the Zener equation, the crystal grain size In contrast, extremely long inclusions are less likely to inhibit grain growth. In other words, the extent to which ductile inclusions inhibit grain growth depends on the length of the inclusions.According to the inventors' knowledge, the length of ductile nonmetallic inclusions is 3 to 3 of the average grain size of the final annealed plate. When it is 9 times, that is, when it is a grain growth-inhibiting ductile inclusion, the maximum value is obtained. On the other hand, the amount of non-metallic inclusions directly dominates crystal grain growth. Therefore, the “strain relief annealing crystal grain growth ratio” is affected by the number density of ductile nonmetallic inclusions having a length in this range, that is, “grain growth inhibiting ductile inclusions”.
[0038]
As mentioned above, the non-oriented electrical steel sheet contains Si, Mn, C, Sol. Al, and N content, and further the number density of grain growth inhibiting ductile inclusions is 1000 / cm. 2 By suppressing to the following, it is possible to increase the strain relief annealing grain growth ratio, it can be a high magnetic flux density non-oriented electrical steel sheet suitable for rotating machines, but in the steel sheet composition Ti, Nb and V, The effect can be further ensured by limiting or adding Sb and Sn. This was confirmed by the following experiment.
[0039]
(Experiment 3)
Steel ingots having the composition shown in Table 3 were manufactured, these steel ingots were heated to 1070 ° C., hot rolled to 2.5 mm, pickled, and then cold rolled to a final thickness of 0.5 mm. Finished. Next, after recrystallization annealing was performed at 800 ° C. for 10 seconds to obtain a product plate, strain product annealing was performed at 750 ° C. for 2 hours to obtain a product plate. Samples were cut out from the obtained product plate and the product plate after strain relief annealing in parallel to the rolling direction and perpendicular to the rolling direction, respectively, and the magnetic flux density and iron loss were measured in accordance with JIS C 2550. The average value was obtained. The measurement results are also shown in Table 3.
[0040]
[Table 3]
As can be seen from Table 3, by limiting Ti to 0.0020% or less, Nb to 0.0050% or less, and the V content to 0.0006% or less, the magnetic properties after strain relief annealing can be further improved. Further, by adding one or two of Sb and Sn, the iron loss after the strain relief annealing can be greatly improved. The reason why the magnetic properties are improved by reducing the amount of Ti, Nb, and V is not necessarily clear, but Ti, Nb, and V are both nitride-forming elements. Since it causes the same damage as finely precipitated AlN, which adversely affects structure formation and grain growth, reducing these elements will prevent this kind of damage, resulting in good magnetic properties. It is done.
[0042]
The reason for the influence on the magnetic properties after strain relief annealing is not clear, but if the amount of Ti, Nb, and V is high in low-Al Si-containing steel, it partially dissolves during hot-rolled sheet annealing and recrystallization annealing. It is believed that nitride or carbide precipitates as nitride or carbide during strain relief annealing and inhibits domain wall movement, resulting in deterioration of iron loss.
[0043]
In addition, it is not clear why the addition of one or two of Sb or Sn greatly improves the iron loss after strain relief annealing, but segregation of Sb and Sn affects the precipitation behavior of V, etc. This is considered to be because the suppression of precipitation and the coarsening of the precipitate occur.
[0044]
By limiting the amount of Ti, Nb and V that are inevitably mixed from the hot metal and Si raw material in this way, the effect of reducing the above-mentioned Sol.Al is further enhanced, and further improvement in magnetic properties is achieved. The In particular, in a component system in which Al is reduced as much as possible, it is advantageous to limit the amount of V in addition to limiting the amounts of Ti and Nb. The effect is particularly great in preventing deterioration after ironing after strain relief annealing. The restrictions on the trace elements are summarized as follows.
[0045]
Ti: 0.0020% or less (including 0), Nb: 0.0050% or less (including 0), and V: 0.0060% or less (including 0)
Ti, Nb, and V form fine nitrides or carbides to inhibit formation of texture and crystal grain growth. In particular, according to the present invention, the tendency is remarkable in the non-oriented electrical steel sheet in which the contents of Sol.Al and N are limited to be low. If these elements are reduced to Ti: 0.0020% or less, Nb: 0.0050% or less, and V: 0.0060% or less, the tendency to form nitrides or carbides thereof is suppressed, and deterioration of iron loss especially after stress relief annealing is prevented. it can.
[0046]
One or two selected from Sb: 0.005-0.10% and Sn: 0.005-0.2%
Sb and Sn effectively promote formation of a texture that is advantageous in terms of magnetic properties by suppressing fine precipitation of nitrides and reducing the effect of inhibiting grain growth. The effect appears when Sb is 0.005% or more and Sn is 0.005% or more, but when it exceeds 0.10% and 0.2%, respectively, grain growth is inhibited.
[0047]
In addition to the above, the characteristics of the steel of the present invention can be exhibited more effectively by limiting or adding the following elements.
[0048]
One or two selected from P: 0.001 to 0.2% and Ni: 0.001 to 0.2%
Since the non-oriented electrical steel sheet of the present invention is low Si, its hardness is low, sagging or crushing occurs at the time of punching, burrs generated at the time of punching are increased, and the space factor of the steel sheet is reduced, etc. May cause problems. P and Ni have the effect of increasing the hardness of the electrical steel sheet. Therefore, these elements can be added according to the demands of customers within a range that does not harm the electromagnetic characteristics, particularly the magnetic flux density.
[0049]
One or two types selected from REM: 0.0001-0.10% and Ca: 0.0001-0.01%
REM and Ca have the effect of coarsening sulfides to improve iron loss. Therefore, these elements can be appropriately added in the expression range of the effect, that is, REM: 0.0001 to 0.10%, Ca: 0.0001 to 0.01%.
[0050]
S: 0.0050% or less (including 0), 0: 0.0100% or less (including 0)
If S exceeds 0.0050%, it will combine with Mn and Cu of the playing element and so on. 2 The tendency to form S becomes strong and hinders crystal grain growth. If O exceeds 0.0100%, the amount of oxide increases and hinders crystal grain growth. Therefore, these elements are preferably limited to the above ranges.
[0051]
In the present invention, the crystal grain size of the finally annealed steel sheet needs to be determined uniformly because the strength level and iron loss level required for the non-oriented electrical steel sheet vary depending on the characteristics of the rotating machine to be manufactured. Absent. However, setting the average recrystallized grain size D to 6 to 25 μm is advantageous in that the strain relief annealing crystal grain growth ratio described above is relatively large, for example, 3 or more.
[0052]
The manufacturing method of the non-oriented electrical steel sheet according to the present invention is not particularly limited. Typically, it can be produced by the following process. First, the molten steel adjusted to a suitable component composition is slabd by a continuous casting method. Next, this is hot-rolled to obtain a hot-rolled sheet. This is subjected to hot-rolled sheet annealing as necessary, and then subjected to cold rolling one or more times with intermediate annealing as required to finish the final sheet thickness. The obtained cold-rolled sheet is subjected to continuous annealing, and then an insulating coating is applied as necessary.
[0053]
In the present invention, the amount of ductile inclusions among inclusions, and the amount of existing inclusions, particularly the ductile inclusions whose length with respect to the average crystal grain size is within a predetermined range, that is, the amount of grain growth inhibiting ductile inclusions are reduced. 1000 pieces / cm 2 It is important to do the following. Such control can be achieved by any one or combination of the following means.
[0054]
First, there is a means for reducing the absolute amount of inclusions in the slab by reducing the oxygen content. In addition, it is effective to make the inclusions in the slab ductile by increasing the amount of Al or Mn, or conversely, by reducing the amount of Al or Mn. Furthermore, since the ductile inclusions tend to be longer as the cumulative rolling reduction after hot rolling becomes larger and shorter as the rolling reduction becomes smaller, the length of nonmetallic inclusions can be increased by increasing or decreasing the slab rolling ratio or by increasing or decreasing the product sheet thickness. It can also be less than 3 times or more than 9 times the average recrystallized grain size of the steel sheet that has been adjusted and finally annealed. Conversely, the average crystal grain size is increased or decreased by changing conditions such as the temperature and soaking time in the final annealing, and as a result, the length of the nonmetallic inclusion is less than 3 times or more than 9 times the average crystal grain size. You can also
[0055]
In the above manufacturing process, the annealing temperature of continuous annealing applied to the cold-rolled sheet cold-rolled to the final sheet thickness is set to 700 to 800 ° C., by adjusting the average crystal grain size to 6 to 25 μm, or It is preferable for adjusting the hardness to an appropriate level, for example, Vickers hardness (Hv) of 100 to 170.
[0056]
The non-oriented electrical steel sheet manufactured in this way can be punched into an iron core for a rotating machine and assembled into a rotor and a stator. At that time, the core material such as the rotor and stator is simultaneously punched from the same steel plate, laminated and assembled to the rotor and stator member, and then only the stator member is subjected to strain relief annealing to promote grain growth and its iron loss. Can be lowered. The conditions for the strain relief annealing may be those in which the strain relief annealing crystal grain growth ratio is 2 or more. For example, it is desirable to set the strain relief annealing at 750 ° C. for about 2 hours in an inert gas atmosphere. At this time, it is preferable that the rotor core member is not subjected to strain relief annealing accompanied by grain growth, and maintains a high strength.
[0057]
The non-oriented electrical steel sheet finally annealed is further subjected to mild distortion, for example, rolling distortion of about 0.5 to 5%, and then subjected to strain relief annealing at 700 to 800 ° C. to promote recrystallization. The particle size can be grown to 30-100 μm. The steel plate thus treated can be used for assembling a stator that requires particularly low iron loss.
[0058]
【Example】
Hereinafter, based on an Example, embodiment of this invention is made more concrete.
[0059]
Example 1
Slabs having the composition shown in Table 4 were produced by a continuous casting method. These slabs were heated at 1110 ° C. for 40 minutes, and then finish-rolled to obtain hot rolled sheets having a thickness of 2.5 mm. The obtained hot-rolled sheet was pickled and scale-removed, and then finished into a cold-rolled sheet having a thickness of 0.50 mm by cold rolling. Then, final annealing was performed at 780 ° C. for 10 seconds in an atmosphere of 50% hydrogen and 50% nitrogen by volume ratio. A semi-organic coating liquid composed of dichromate and resin was applied to the final annealed plate, and baked at 300 ° C. to obtain a final product. Note that the amount of the grain growth-inhibiting ductile inclusion was varied by changing the slab thickness or the reduction schedule in hot rolling.
[0060]
A sample was cut out from the obtained product, and the magnetic flux density, iron loss, upper yield point (YP), and Vickers hardness (Hv) were measured according to JIS C2550. Further, the average crystal grain size and the number density of grain growth-inhibiting ductile inclusions were measured. The measurement was performed on a plane perpendicular to the width direction.
[0061]
Next, after the above product was subjected to strain relief annealing at 750 ° C. for 2 hours in an argon atmosphere, the core loss and the average crystal grain size were measured in the same manner as the above product, and the strain relief annealed crystal The grain growth ratio was determined.
[0062]
[Table 4]
The results obtained are shown in Table 5. As shown in Tables 4 and 5, those having the component composition and the grain growth inhibiting inclusion number density according to the present invention have a large strain relief annealing grain growth ratio, and the upper yield point (YP) of the product (final annealing state) ) And a relatively high Vickers hardness (Hv), it is suitable for manufacturing by simultaneously punching the rotor and stator of a rotating machine.
[0064]
[Table 5]
(Example 2)
A 210 mm thick continuous cast slab having the component composition shown in Table 6 was produced. At that time, the amount of grain-inhibited ductile inclusions was 1000 / cm2 by optimizing the slag composition in the steelmaking process and the slab thickness and hot rolling conditions by the component composition. 2 It was made to be within the range. The obtained slab was processed in the same manner as in Example 1 to obtain a product and tested in the same manner as in Example 1. However, the final annealing of steel symbol 58 was performed at 680 ° C., and the final annealing of steel symbol 59 was performed at 850 ° C. The results obtained are shown in Table 7. As shown in Table 7, those having a component composition and an average crystal grain size according to the present invention all have an excellent strain relief annealed crystal grain growth ratio, thereby making it possible to simultaneously produce a rotor and a stator of a rotating machine. It is suitable.
[0066]
[Table 6]
[Table 7]
As described above, the present invention can provide a non-oriented electrical steel sheet that is extremely suitable for manufacturing a rotor for a rotating machine and a stator. However, the non-oriented electrical steel sheet according to the present invention is not limited to this, and has a feature of excellent so-called recyclability. That is, when the Al content of the steel sheet is high, when casting the shaft of a motor by recycling the iron core material, the surface oxidation of the molten steel proceeds and the viscosity increases and the moldability of the molten steel decreases. In addition, sound castings may not be obtained, and scraps containing Al are generally considered to be poorly recyclable. However, the non-oriented electrical steel sheet according to the present invention is a low Al material and is recycled for casting. The nature is extremely high.
[0069]
【The invention's effect】
The high magnetic flux density non-oriented electrical steel sheet according to the present invention enables high magnetic flux density and high strength for the rotor material, high magnetic flux density and high for the stator material while simultaneously collecting the rotor material and the stator material from the same steel plate. Low iron loss can be imparted. Thereby, the manufacturing efficiency and output characteristics of the rotating machine member, and thus the rotating machine, can be greatly improved. In addition, the non-oriented electrical steel sheet according to the present invention is excellent in recyclability at the time of casting, and the castability when recycling scraps of punched material is improved.
[Brief description of the drawings]
FIG. 1 shows the relationship between the ratio of the average crystal grain size of a steel sheet after strain relief annealing to the average crystal grain size of the steel sheet after final annealing and the N content, with the number of grain growth-inhibiting ductile nonmetallic inclusions as a parameter. It is a graph.
Claims (8)
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002229251A JP4718749B2 (en) | 2002-08-06 | 2002-08-06 | High magnetic flux density non-oriented electrical steel sheet for rotating machine and member for rotating machine |
| PCT/JP2003/009947 WO2004013365A1 (en) | 2002-08-06 | 2003-08-05 | Nonoriented magnetic steel sheet, member for rotary machine and rotary machine |
| CN 03801038 CN1277945C (en) | 2002-08-06 | 2003-08-05 | Nonoriented magnetic steel sheet, member for rotary machine and rotary machine |
| KR1020047004538A KR100567239B1 (en) | 2002-08-06 | 2003-08-05 | Nonoriented magnetic steel sheet, member for rotary machine and rotary machine |
| TW92121498A TWI276693B (en) | 2002-08-06 | 2003-08-06 | Nonoriented magnetic steel sheet, member for rotary machine and rotary machine |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002229251A JP4718749B2 (en) | 2002-08-06 | 2002-08-06 | High magnetic flux density non-oriented electrical steel sheet for rotating machine and member for rotating machine |
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| Publication Number | Publication Date |
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| JP2004068084A JP2004068084A (en) | 2004-03-04 |
| JP4718749B2 true JP4718749B2 (en) | 2011-07-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP2002229251A Expired - Lifetime JP4718749B2 (en) | 2002-08-06 | 2002-08-06 | High magnetic flux density non-oriented electrical steel sheet for rotating machine and member for rotating machine |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JP4718749B2 (en) |
| KR (1) | KR100567239B1 (en) |
| CN (1) | CN1277945C (en) |
| TW (1) | TWI276693B (en) |
| WO (1) | WO2004013365A1 (en) |
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| KR20170104546A (en) | 2015-02-18 | 2017-09-15 | 제이에프이 스틸 가부시키가이샤 | Non-oriented electrical steel sheet, manufacturing method thereof, and motor core |
| US10975451B2 (en) | 2015-08-04 | 2021-04-13 | Jfe Steel Corporation | Method for producing non-oriented electrical steel sheet having excellent magnetic properties |
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| JP4218136B2 (en) * | 1999-06-24 | 2009-02-04 | Ｊｆｅスチール株式会社 | Non-oriented electrical steel sheet with high magnetic flux density and low iron loss and method for producing the same |
| JP2002206114A (en) * | 2000-12-28 | 2002-07-26 | Nippon Steel Corp | Method for manufacturing nonoriented silicon steel sheet |
| CN108454769A (en) * | 2018-03-29 | 2018-08-28 | 曾东斌 | A kind of super labour-saving bicycle |
-
2002
- 2002-08-06 JP JP2002229251A patent/JP4718749B2/en not_active Expired - Lifetime
-
2003
- 2003-08-05 WO PCT/JP2003/009947 patent/WO2004013365A1/en active Application Filing
- 2003-08-05 CN CN 03801038 patent/CN1277945C/en not_active Expired - Fee Related
- 2003-08-05 KR KR1020047004538A patent/KR100567239B1/en active IP Right Grant
- 2003-08-06 TW TW92121498A patent/TWI276693B/en not_active IP Right Cessation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20170104546A (en) | 2015-02-18 | 2017-09-15 | 제이에프이 스틸 가부시키가이샤 | Non-oriented electrical steel sheet, manufacturing method thereof, and motor core |
| US10941458B2 (en) | 2015-02-18 | 2021-03-09 | Jfe Steel Corporation | Non-oriented electrical steel sheet, production method therefor, and motor core |
| US10975451B2 (en) | 2015-08-04 | 2021-04-13 | Jfe Steel Corporation | Method for producing non-oriented electrical steel sheet having excellent magnetic properties |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004013365A1 (en) | 2004-02-12 |
| TW200403346A (en) | 2004-03-01 |
| CN1556869A (en) | 2004-12-22 |
| TWI276693B (en) | 2007-03-21 |
| KR20040039438A (en) | 2004-05-10 |
| KR100567239B1 (en) | 2006-04-03 |
| CN1277945C (en) | 2006-10-04 |
| JP2004068084A (en) | 2004-03-04 |
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