JP3823548B2

JP3823548B2 - Electrical steel sheet with excellent machinability and magnetic properties

Info

Publication number: JP3823548B2
Application number: JP19747298A
Authority: JP
Inventors: 光代前田; 裕義屋鋪; 康孝岡田
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1998-07-13
Filing date: 1998-07-13
Publication date: 2006-09-20
Anticipated expiration: 2018-07-13
Also published as: JP2000030922A

Description

【０００１】
【発明の属する技術分野】
本発明は、電気機器の鉄心として用いられる電磁鋼板に関し、特に回転機の回転子、固定子の旋盤加工における切削性に優れ、かつ磁気特性に優れた電磁鋼板に関する。
【０００２】
【従来の技術】
電磁鋼板は変圧器、安定器などの静止機器や、電動機、発電機等の回転機の鉄心材料として用いられる。このような材料には優れた磁気特性が要求されるが、鉄心を製作する段階で、打ち抜き性・かしめ性・切削性などの加工性の良いことも要求される。しかしながらこれまで、無方向性電磁鋼板における切削性は、打ち抜き性やかしめ性と比較して重要視されることが少なかった。
【０００３】
回転機の回転子、固定子は電磁鋼板を打ち抜き、積層後、回転子−固定子間のエアギャップの寸法精度を高めるため、旋盤による切削加工が行われる。とくに回転子の鉄心は回転中の動的バランスが重要であるため精度の高い切削を行うことが多い。切削性に劣る材料を用いると、鉄心の製作段階で切削工具の取り替え頻度が高くなり作業性や生産コストが低下する。
【０００４】
また、切削性に劣る材料では、切削によるバリが発生しやすい。回転子や固定子には磁極を形成するための溝が設けられているが、バリはこの溝の縁部または端部で発生しやすい。切削バリを残したまま回転機に組み込むと、鉄心の積層間で電気的な短絡を起こし鉄損が増加したり、鉄心が過熱する恐れがある。あるいは、バリが回転子−固定子間のエアギャップに巻き込まれて積層の破損やコイルの絶縁破壊を生じたりする。そのため、組み立て前に切削バリを除去しなければならないが、このバリ除去作業は余分な作業工数が発生すること、バリ除去設備が必要なこと、ハンドリング作業の安全が損なわれること等の問題がある。
【０００５】
従って、切削が容易でバリが発生しない電磁鋼板が求められている。この要請に対して例えば下記の技術が提案されている。
【０００６】
特公昭５４−１１７６９号公報には、電磁鋼または電磁鋼板に黒鉛を添加することで切欠き効果、潤滑効果が生じ、切削性が良くなるとしているが、黒鉛添加は鋼板の磁気特性に悪影響を与えることから好ましくない。
【０００７】
特公昭５６−３４６１６号公報には、無方向性電磁鋼板にＭｎを１〜３％と多量に添加すると切削性が向上する技術が開示されているが、その理由は明確にはしておらず、Ｍｎの多量添加はコスト上昇となるため好ましくない。
【０００８】
特開平４−２９３７２４号公報には、鋼板中にＰを添加することにより、無方向性電磁鋼板の磁気特性を悪化させずに切削性を改善するとしているが、Ｐ添加による靭性低下を補償するため、極低Ｃ、極低Ｓ化が必要であり脱Ｃ脱Ｓコストが増加すること、および（Ｓｉ＋Ａｌ）＜１．５重量％の制約があり、電磁鋼板の基本成分であるＳｉ添加量の制約を受けるという問題がある。
【０００９】
特開平５−３３１６０２号公報には鋼板中のＭｎ量とＡｌ量を規制することにより、鋼板の硬度を調整して切削性を保持する技術が開示されているが、単に鋼板の硬度を維持するだけでは十分な切削性が得られるとは言い難い。
【００１０】
【発明が解決しようとする課題】
本発明の課題は、切削性と磁気特性に優れた電磁鋼板を提供することにある。
【００１１】
【課題を解決するための手段】
本発明者らは、切削加工を多用する回転子の材料である無方向性電磁鋼板につき、各種の製造条件で素材鋼を溶製し、各種の圧延、焼鈍条件で試験材を作成した。
【００１２】
これらの試験材の鋼中の介在物の個数と磁気特性の関係について調査し、おおむね粒子径０．１μｍ以上の介在物について、顕微鏡観察断面で１００００個／ｍｍ²以下であれば所定の磁気特性を満足することを確認した。
【００１３】
次いで、試験材を鉄心の形に積層し、切削性の試験を行った。各種の試験片のうち、工具損傷が少なく工具寿命の長い試験片について、つまり切削性が良いと評価された試験片について丹念に観察すると、切削性に劣ると評価された試験片に比べて、介在物のサイズが大きいものが多いという知見を得た。
【００１４】
さらに、切削性が良いと評価された試験片のうち磁気特性が良いものを調査すると、介在物の粒子径２μｍ以上の比較的大きな介在物数が全体の介在物の中である程度以上の比率（１０％以上）を有することが分かった。
【００１５】
上記の知見に基づき完成した本発明の要旨は「断面で観察される鋼中の介在物の粒子のうち、粒子径２μｍ以上の粒子数が、粒子径０．１μｍ以上の粒子数に対して１０％以上であることを特徴とする切削性と磁気特性に優れた電磁鋼板」にある。
【００１６】
ここで介在物とは、硫化物、酸化物、炭化物、窒化物、およびこれらの複合体をいう。粒子径とは等面積の円の直径として表したものをいう。
【００１７】
【発明の実施の形態】
本発明の実施に際して、各条件を限定した理由を以下に述べる。
図１は（Ｓｉ＋Ａｌ）量が約０．２重量％である化学組成を有する試験片の鋼中介在物の個数と磁気特性（鉄損Ｗ１５／５０）の関係を示すグラフである。同図に示すように、粒子数が１００００個／ｍｍ²を超えると磁気特性が劣化することがわかる。これは結晶粒の成長が介在物に抑制されるためと考えられる。
【００１８】
なお、粒子数の測定は、光学顕微鏡で効率よく観察できる０．１μｍ以上の介在物を対象とした。
【００１９】
次に、発明者らは介在物のサイズと磁気特性に注目し、化学組成がほぼ同じ鋼材で、０．１μｍ以上の粒子径の介在物の個数がほぼ同じ（８０００〜１００００個／ｍｍ²）試験片を選び出し、その磁気特性を調査した。これらの材料の試験片の中に、磁気特性に優れたものと劣るものとがあった。磁気特性に劣る材料を光学顕微鏡で調べると、微細な介在物が多数分散しており、磁気特性に優れた材料では微細な介在物の個数が少なく、粒子径の大きな介在物が多いことがわかった。すなわち、介在物粒子数が同じ場合、粒子径が大きい側に分布しているものが磁気特性に優れている。この時、介在物の個数を粒子径の大きさで層別したところ、下記のように、磁気特性を劣化させるのは粒子径が２μｍ未満の介在物であることがわかった。
【００２０】
図２は介在物の粒子径と介在物個数比率の関係を示すグラフである。同図において、各試験片の粒子径０．１μｍ以上の全介在物個数はほぼ同数（８０００〜１００００個／ｍｍ²）であるが、２μｍ以上の介在物が少なく、微細な介在物が多い鋼板Ａでは他の鋼板に比べて鉄損が劣っている。
【００２１】
同図に示すように、粒子径を２μｍで整理すると、介在物の粒子個数と磁気特性との相関が強いことがわかる。
【００２２】
次に、切削性のよい試験体について、その切削面を走査型電子顕微鏡（ＳＥＭ）で観察すると、切削破断の起点には介在物が存在することがわかった。このことから、材料が切削加工を受ける際に、工具に介在物粒子が当たることで被削材に亀裂を生じ、割れが促進され切削が進むものと推定した。さらに、切削屑および切削バリの形態と介在物の形態とを比較したところ、介在物が切削時の破断起点になるためには、そのサイズがある程度以上の大きさである方がより効果的であることがわかった。
【００２３】
図３は、介在物粒子径と切削工具の磨耗量の関係を示すグラフである。
同図は粒子径０．１μｍ以上の全介在物個数がほぼ同数（８０００〜１００００個／ｍｍ²）、（Ｓｉ＋Ａｌ）が約１重量％、ビッカース硬度が１１０〜１３０である種々の介在物粒子径分布を有する無方向性電磁鋼板の試験片について調査したものである。同図では、横軸は粒子径が０．１μｍ以上の介在物の単位面積当たりの個数を分母とし、粒子径が２μｍ以上の介在物の個数を分子とした比率（％）で整理した。同図からわかるように、粒子径２μｍ以上の介在物個数が、粒子径０．１μｍ以上の粒子個数全体の１０％を超えると、電磁鋼板の切削性は向上することがわかる。
【００２４】
以上のことから、切削性と磁気特性を両立させるためには、０．１μｍ以上の介在物を対象としたときの個数比率で、２μｍ以上のものが少なくとも１０％以上でなければならないといえる。望ましくはこの比率が１５％以上、さらに望ましくは２０％以上である。また、磁気特性への影響および切削性への影響からみて、介在物の種類は問わない。
【００２５】
次に、本発明の電磁鋼板を製造する方法を述べる。
本発明の電磁鋼板の種類は無方向性、１方向性、２方向性いずれに適用してもよい。切削性が重要なものは回転機の回転子であるため、とくに無方向性電磁鋼板に好適である。
【００２６】
鋼成分は電磁鋼板の場合は、化学組成が重量％で、Ｃ：≦０．００５％、Ｍｎ：０．１〜４％、Ｓｉ：０．１〜４．５％、Ａｌ：≦８％、Ｐ：≦０．１％、Ｓ：≦０．０５％、残部がＦｅおよび不可避的不純物、が代表的組成である。
【００２７】
本発明では鋼中に比較的粒径の大きな介在物を分散させるため、介在物の種類は大きなものが得られ易くて圧延工程で細粒化しにくい強固なものが望ましく、硫化物、酸化物あるいはそれらの複合体を主体に析出させるのが好適である。従って、上記の化学組成ではＳ量とＯ量の両者のバランスを調整するのが望ましい。炭化物、窒化物も本発明の介在物として好適であるが、それらを形成させ得るＴｉ、Ｚｒ、Ａｌ、Ｖ、Ｎｂ、Ｃｒ、Ｂ、Ｗなどを添加するのが望ましい。
【００２８】
溶製は常法にしたがって、転炉で出鋼後、真空脱ガス装置で脱炭処理、脱酸処理を行い、電磁鋼板の基本組成に必要なＳｉ、Ａｌ、Ｍｎを添加する。このとき脱酸、脱硫方法を制御することで介在物の粒子径が大きくなるようにするのが望ましい。この溶鋼を常法に従い連続鋳造する。
【００２９】
熱延条件は特に規定するものではないが、介在物を細粒化しないように、加熱温度は１１５０℃以下とするのが望ましい。その後、酸洗、冷間圧延、必要に応じて温間圧延、焼鈍、必要に応じて再冷間圧延、再焼鈍を行う。焼鈍はバッチ焼鈍でも連続焼鈍でもよいが、制御の容易な連続焼鈍が望ましい。焼鈍温度は所定の磁気特性を付与するため、７５０〜１１００℃とするのが望ましい。
【００３０】
【実施例】
（実施例１）
化学組成が重量％で、Ｃ：０．００２〜０．００５％、Ｍｎ：０．１〜０．４％、Ｓｉ：０．１〜０．２％、Ａｌ：０．０００１〜０．００５０％、Ｐ：０．０５〜０．０８％、Ｓ：０．００５〜０．０５０％、Ｏ：０．００３〜０．０２０％、残部がＦｅおよび不可避的不純物からなる鋼を常法により溶製し、熱間圧延、冷間圧延、焼鈍を行って番号Ａ〜Ｉの無方向性電磁鋼板を作成した。製造条件として番号Ａ〜Ｃのグループに対して、番号ＤはＳを低めとし、番号Ｅは熱延加熱温度を高くし、番号ＦはＳ量を低く熱延加熱温度を高くし、番号Ｇは冷間圧下率を高くし、番号Ｈは酸素量を少なくし、番号Ｉは酸素量を高くして各種の介在物の粒子径が得られるようにした。
【００３１】
得られた鋼板に絶縁皮膜を施し、最終板厚０．５０ｍｍとした。この鋼板を円盤状に打ち抜いて積層し、鋼板番号Ａ〜Ｉに対応した切削試験体Ａ〜Ｉとした。
【００３２】
この試験体を旋盤で切削し、切削性を比較した。切削試験条件は切削速度：１５０ｍ／ｍｉｎ、送り：０．２ｍｍ／ｒｅｖ、切り込み量：０．５ｍｍとした。切削工具はブレーカー付サーメットチップを使用した。切削性は、工具摩耗をチップの逃げ面平均摩耗量で評価した。磁気特性はＪＩＳに表記されているエプスタイン試験法で鉄損と磁束密度を測定した。
【００３３】
試験体の介在物は、光学顕微鏡により板厚断面を倍率４００倍で６０視野につき観察し、画像処理装置にて個々の介在物粒子径を円相当径として算出した。各試験体とも介在物は大部分が硫化物、酸化物およびそれらの複合介在物であり、他にはわずかな窒化物、および炭化物が分散していた。
【００３４】
図４は試験体の種類と粒子径２μｍ以上の介在物比率の関係を示すグラフである。
【００３５】
図４に示すように、試験体Ａ〜Ｃは、粒子径２μｍ以上の介在物の比率が１０％以上であり、本発明の範囲を満足するものであった（試験体Ａ〜Ｃを本発明例とする）。試験体Ｄ〜Ｉは、本発明の範囲を満足していなかった（試験体Ｄ〜Ｉを比較例とする）。
【００３６】
図５は試験体別の切削時間と工具磨耗量の関係を示すグラフである。また、表１に各試験体の磁気特性（鉄損：Ｗ１５／５０および磁束密度：Ｂ５０）を示す。
【００３７】
【表１】

【００３８】
図５において、本発明例である試験体Ａ〜Ｃは工具摩耗量が小さく、表１に示すように磁気特性も良好（鉄損７．０（Ｗ／ｋｇ）以下、磁束密度１．８（Ｔ）以上）であった。比較例である被削材Ｄ、Ｅ、Ｆは、同図に示すように工具摩耗量が大きく、また、表１に示すように磁気特性も不良であった。比較例である試験体Ｇ、Ｈ、Ｉは、同図に示すように工具摩耗量は小さいが、表１に示すように磁気特性に劣っていた。
【００３９】
（実施例２）
化学組成が重量％で、Ｃ：０．００２〜０．００３％、Ｍｎ：０．１〜０．３％、Ｓｉ：０．９〜１．１％、Ａｌ：０．３〜０．５％、Ｐ：０．０６〜０．０８％、Ｓ：０．０００５〜０．０５０％、Ｏ：０．００２〜０．０１２、残部がＦｅおよび不可避的不純物からなる鋼を常法により溶製し、熱間圧延、冷間圧延、焼鈍を行って番号Ｐ〜Ｘの無方向性電磁鋼板を作成した。製造条件として番号Ｐ〜Ｒのグループに対し、番号Ｓは冷間圧下率を高めにし、番号ＴはＳ量を低くし、番号Ｕは熱延加熱温度高くし、番号Ｖは酸素量を低くし、番号Ｗは酸素量を高くし、番号Ｘは酸素量を低くし熱延加熱温度を高くして、各種の介在物の粒子径が得られるようにした。
【００４０】
これらの鋼板に絶縁皮膜を施し、最終板厚０．３５ｍｍとした。この鋼板を外周に４本の溝の付いた円盤状に打ち抜いて積層し、番号Ｐ〜Ｘに対応して断続切削の試験体Ｐ〜Ｘとした。断続切削試験条件は切削速度：３２０ｍ／ｍｉｎ，送り：０．０５ｍｍ／ｒｅｖ，切り込み量：０．０５ｍｍとし、切削工具は超硬チップを使用した。
【００４１】
実施例１と同じ手順で切削性（工具磨耗）、磁気特性（鉄損、磁束密度）を評価した。
被削材の切り欠き溝部に発生した切削バリを調査するために、切削時間１２００秒後に切削バリの長さを計測した。
【００４２】
図６は試験体の種類と粒子径２μｍ以上の介在物比率の関係を示すグラフである。
同図に示すように、試験体Ｐ〜Ｒは、粒子径２μｍ以上の介在物の比率が１０％以上であり、本発明の範囲を満足するものであった（試験体Ｐ〜Ｒを本発明例とする）。試験体Ｓ〜Ｘは、本発明の範囲を満足していなかった（試験体Ｓ〜Ｘを比較例とする）。
【００４３】
図７は試験体別の切削時間と工具磨耗量の関係を示すグラフである。
図８は試験体別の切削バリ長さを示すグラフである。また、表２に各試験体の磁気特性（鉄損：Ｗ１５／５０および磁束密度：Ｂ５０）を示す。
【００４４】
【表２】

【００４５】
図７に示すように、本発明例の試験体Ｐ、Ｑ、Ｒは、工具摩耗量が少なく、図８に示すように切削バリ長さも小さかった。また、表２に示すように、試験体Ｐ、Ｑ、Ｒの磁気特性は良好（鉄損４．０（Ｗ／ｋｇ）以下、磁束密度１．８（Ｔ）以上）であった。
【００４６】
図７に示すように、比較例の試験体Ｓ、Ｔでは、工具摩耗量が大きく、図８に示すように、切削バリ長さも大きかった。また、表２に示すように、試験体Ｓ、Ｔの磁気特性も不良であった。
【００４７】
比較例である試験体Ｕでは切削試験途中で工具欠損が発生し、試験を中止したため工具磨耗量、切削バリ長さのデータは採取しなかった。また、試験体Ｕの磁気特性も劣っていた。
【００４８】
図７に示すように、比較例である試験体Ｖ、Ｗ、Ｘについては、工具摩耗量は試験体Ｓ、Ｔより小さく、図８に示すように、切削バリも比較的小さかったが、表２に示すように磁気特性が劣っていた。
【００４９】
【発明の効果】
本発明の電磁鋼板は、切削性と磁気特性の両方を満足し、積層鉄心に組み立て切削加工を行う場合、切削工具の寿命が長くなり、切削バリの発生もないため、作業能率が向上し、バリ除去作業を省略することができる。
【図面の簡単な説明】
【図１】鋼中介在物個数と磁気特性（鉄損Ｗ１５／５０）の関係を示すグラフである。
【図２】介在物の粒子径と介在物個数比率の関係を示すグラフである。
【図３】介在物粒子径と切削工具の磨耗量の関係を示すグラフである。
【図４】試験体の種類と粒子径２μｍ以上の介在物比率の関係を示すグラフである。
【図５】試験体別の切削時間と工具磨耗量の関係を示すグラフである。
【図６】試験体の種類と粒子径２μｍ以上の介在物比率の関係を示すグラフである。
【図７】試験体別の切削時間と工具磨耗量の関係を示すグラフである。
【図８】試験体別の切削バリ長さを示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic steel sheet used as an iron core of an electric device, and more particularly to an electromagnetic steel sheet excellent in machinability in lathe processing of a rotor and a stator of a rotating machine and excellent in magnetic properties.
[0002]
[Prior art]
Electrical steel sheets are used as iron core materials for stationary equipment such as transformers and ballasts, and rotating machines such as motors and generators. Such a material is required to have excellent magnetic properties, but is also required to have good workability such as punchability, caulking property, and cutting property at the stage of manufacturing the iron core. However, until now, machinability in non-oriented electrical steel sheets has been less important than punchability and caulking.
[0003]
The rotor and stator of the rotating machine are punched out of magnetic steel sheets, and after laminating, cutting with a lathe is performed to increase the dimensional accuracy of the air gap between the rotor and the stator. In particular, the core of the rotor is often cut with high precision because the dynamic balance during rotation is important. If a material inferior in machinability is used, the frequency of replacement of the cutting tool is increased at the production stage of the iron core, and workability and production cost are reduced.
[0004]
Moreover, in the material inferior to machinability, the burr | flash by cutting tends to generate | occur | produce. Grooves for forming magnetic poles are provided in the rotor and the stator, but burrs are likely to occur at the edges or ends of the grooves. If it is incorporated in a rotating machine with the cutting burrs left, there is a risk of causing an electrical short circuit between the laminated cores, increasing iron loss or overheating the iron core. Or a burr | flash is caught in the air gap between a rotor and a stator, and a damage of lamination | stacking and a dielectric breakdown of a coil will be produced. Therefore, it is necessary to remove the cutting burrs before assembling. However, this deburring work has problems such as extra work man-hours, the need for deburring equipment, and the safety of handling work being impaired. .
[0005]
Accordingly, there is a need for an electrical steel sheet that is easy to cut and does not generate burrs. In response to this request, for example, the following techniques have been proposed.
[0006]
In Japanese Patent Publication No. 54-11769, the addition of graphite to an electromagnetic steel or an electrical steel sheet produces a notch effect and a lubrication effect, which improves the machinability. However, the addition of graphite has an adverse effect on the magnetic properties of the steel sheet. It is not preferable from giving.
[0007]
Japanese Patent Publication No. 56-34616 discloses a technique for improving machinability when Mn is added to a non-oriented electrical steel sheet in a large amount of 1 to 3%, but the reason is not clarified. , Addition of a large amount of Mn is not preferable because it increases costs.
[0008]
In JP-A-4-293724, the addition of P in the steel sheet improves the machinability without deteriorating the magnetic properties of the non-oriented electrical steel sheet, but compensates for the reduction in toughness due to the addition of P. Therefore, there is a need for extremely low C and extremely low S, which increases the cost of removing C and removing S, and there is a restriction of (Si + Al) <1.5% by weight. There is a problem of being restricted.
[0009]
Japanese Patent Application Laid-Open No. 5-331602 discloses a technique for maintaining the machinability by adjusting the hardness of the steel sheet by regulating the amount of Mn and the amount of Al in the steel sheet, but simply maintaining the hardness of the steel sheet. It is hard to say that sufficient machinability can be obtained by just using this.
[0010]
[Problems to be solved by the invention]
The subject of this invention is providing the electromagnetic steel plate excellent in machinability and a magnetic characteristic.
[0011]
[Means for Solving the Problems]
The present inventors have melted raw steel under various production conditions and produced test materials under various rolling and annealing conditions for non-oriented electrical steel sheets, which are rotor materials that frequently use cutting.
[0012]
The relationship between the number of inclusions in the steel of these test materials and the magnetic properties was investigated, and for inclusions with a particle diameter of 0.1 μm or more, the predetermined magnetic properties were 10000 / mm ² or less in the microscopic observation cross section. Confirmed that you are satisfied.
[0013]
Next, the test material was laminated in the form of an iron core, and a machinability test was performed. Of the various test specimens, the specimens with little tool damage and long tool life, that is, the specimens evaluated as having good machinability, were carefully observed, compared to the specimens evaluated as inferior in machinability. It was found that many inclusions were large in size.
[0014]
Further, when a test piece having a good magnetic property among the test pieces evaluated to have good machinability is investigated, a relatively large number of inclusions having a particle diameter of 2 μm or more of inclusions is a ratio of a certain amount or more in the whole inclusions ( 10% or more).
[0015]
The gist of the present invention completed on the basis of the above knowledge is that “the number of particles having a particle diameter of 2 μm or more out of inclusion particles in steel observed in a cross section is 10 times the number of particles having a particle diameter of 0.1 μm or more. % Of electrical steel sheet excellent in machinability and magnetic properties, characterized by being at least%.
[0016]
Here, inclusions refer to sulfides, oxides, carbides, nitrides, and composites thereof. The particle diameter is expressed as the diameter of a circle of equal area.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The reason why each condition is limited in the implementation of the present invention will be described below.
FIG. 1 is a graph showing the relationship between the number of inclusions in steel and magnetic properties (iron loss W15 / 50) of a test piece having a chemical composition in which the amount of (Si + Al) is about 0.2% by weight. As shown in the figure, it can be seen that the magnetic properties deteriorate when the number of particles exceeds 10,000 / mm ² . This is presumably because the growth of crystal grains is suppressed by inclusions.
[0018]
The number of particles was measured for inclusions of 0.1 μm or more that can be efficiently observed with an optical microscope.
[0019]
Next, the inventors pay attention to the size and magnetic properties of inclusions, and the number of inclusions having a particle diameter of 0.1 μm or more is substantially the same (8000 to 10,000 pieces / mm ² ) with steel materials having substantially the same chemical composition. Test specimens were selected and their magnetic properties were investigated. Some specimens of these materials were excellent in magnetic properties and inferior. Examining materials with inferior magnetic properties with an optical microscope reveals that many fine inclusions are dispersed, and materials with excellent magnetic properties have a small number of fine inclusions and many inclusions with a large particle size. It was. That is, when the number of inclusion particles is the same, those distributed on the larger particle diameter side are excellent in magnetic properties. At this time, when the number of inclusions was stratified according to the size of the particle diameter, it was found that the inclusions having a particle diameter of less than 2 μm deteriorate the magnetic properties as described below.
[0020]
FIG. 2 is a graph showing the relationship between the particle diameter of inclusions and the number ratio of inclusions. In the figure, the number of all inclusions having a particle diameter of 0.1 μm or more in each test piece is almost the same number (8000 to 10000 / mm ² ), but there are few inclusions of 2 μm or more and many fine inclusions. In A, iron loss is inferior compared with other steel plates.
[0021]
As shown in the figure, when the particle diameter is arranged at 2 μm, it can be seen that the correlation between the number of inclusion particles and the magnetic characteristics is strong.
[0022]
Next, when the cutting surface of the test body having good cutting properties was observed with a scanning electron microscope (SEM), it was found that inclusions exist at the starting point of the cutting fracture. From this, when the material was subjected to the cutting process, it was estimated that the inclusion particles hit the tool to cause a crack in the work material, which promotes the cracking and advances the cutting. Furthermore, when the shape of the cutting waste and the cutting burr is compared with the shape of the inclusion, it is more effective that the size is larger than a certain size in order for the inclusion to be the starting point of breakage during cutting. I found out.
[0023]
FIG. 3 is a graph showing the relationship between the inclusion particle diameter and the amount of wear of the cutting tool.
The figure shows various inclusion particle sizes in which the number of all inclusions having a particle diameter of 0.1 μm or more is approximately the same number (8000 to 10000 / mm ² ), (Si + Al) is about 1% by weight, and Vickers hardness is 110 to 130. It investigated about the test piece of the non-oriented electrical steel sheet which has distribution. In the figure, the horizontal axis is arranged in a ratio (%) where the number per unit area of inclusions having a particle diameter of 0.1 μm or more is used as the denominator and the number of inclusions having a particle diameter of 2 μm or more is used as the numerator. As can be seen from the figure, when the number of inclusions having a particle diameter of 2 μm or more exceeds 10% of the total number of particles having a particle diameter of 0.1 μm or more, the machinability of the electrical steel sheet is improved.
[0024]
From the above, it can be said that in order to achieve both machinability and magnetic properties, the number ratio when inclusions of 0.1 μm or more are targeted should be at least 10%. This ratio is desirably 15% or more, and more desirably 20% or more. Moreover, the kind of inclusion is not ask | required from the influence on a magnetic characteristic and the influence on machinability.
[0025]
Next, a method for producing the electrical steel sheet of the present invention will be described.
The type of the electrical steel sheet of the present invention may be applied to any of non-directionality, unidirectionality, and bidirectionality. Since what is important for cutting is a rotor of a rotating machine, it is particularly suitable for a non-oriented electrical steel sheet.
[0026]
In the case where the steel component is an electromagnetic steel sheet, the chemical composition is weight%, C: ≦ 0.005%, Mn: 0.1-4%, Si: 0.1-4.5%, Al: ≦ 8%, P: ≦ 0.1%, S: ≦ 0.05%, the balance being Fe and inevitable impurities are typical compositions.
[0027]
In the present invention, inclusions having a relatively large particle size are dispersed in the steel. Therefore, it is desirable that the inclusions be strong and easily obtained, and are not easily finely divided in the rolling process. It is preferable to deposit these composites mainly. Therefore, it is desirable to adjust the balance between the S amount and the O amount in the above chemical composition. Carbides and nitrides are also suitable as inclusions in the present invention, but it is desirable to add Ti, Zr, Al, V, Nb, Cr, B, W, etc. that can form them.
[0028]
Melting is performed in accordance with a conventional method, after steel is output in a converter, decarburized and deoxidized in a vacuum degasser, and Si, Al, and Mn necessary for the basic composition of the electrical steel sheet are added. At this time, it is desirable to increase the particle size of the inclusions by controlling the deoxidation and desulfurization methods. This molten steel is continuously cast according to a conventional method.
[0029]
The hot rolling conditions are not particularly specified, but the heating temperature is preferably 1150 ° C. or lower so as not to make the inclusions fine. Then, pickling, cold rolling, warm rolling and annealing as necessary, re-cold rolling and re-annealing as necessary. The annealing may be batch annealing or continuous annealing, but continuous annealing that is easy to control is desirable. The annealing temperature is desirably 750 to 1100 ° C. in order to impart predetermined magnetic properties.
[0030]
【Example】
Example 1
Chemical composition is weight%, C: 0.002-0.005%, Mn: 0.1-0.4%, Si: 0.1-0.2%, Al: 0.0001-0.0050% , P: 0.05 to 0.08%, S: 0.005 to 0.050%, O: 0.003 to 0.020%, the balance is made of steel consisting of Fe and inevitable impurities by a conventional method Then, hot rolling, cold rolling, and annealing were performed to create non-oriented electrical steel sheets with numbers A to I. With respect to the group of numbers A to C as manufacturing conditions, number D is set to lower S, number E is set to higher hot rolling heating temperature, number F is set to lower S amount and hot rolling heating temperature is increased, number G is The cold rolling reduction was increased, the number H reduced the amount of oxygen, and the number I increased the amount of oxygen to obtain particle sizes of various inclusions.
[0031]
An insulating film was applied to the obtained steel sheet to a final thickness of 0.50 mm. This steel plate was punched into a disk shape and laminated to obtain cutting test bodies A to I corresponding to the steel plate numbers A to I.
[0032]
This specimen was cut with a lathe and the machinability was compared. The cutting test conditions were cutting speed: 150 m / min, feed: 0.2 mm / rev, and cutting depth: 0.5 mm. The cutting tool used was a cermet tip with a breaker. For machinability, tool wear was evaluated by the average flank wear amount of the chip. For the magnetic characteristics, iron loss and magnetic flux density were measured by the Epstein test method described in JIS.
[0033]
The inclusions of the test specimens were observed for 60 fields of view with a magnification of 400 times with an optical microscope, and each inclusion particle diameter was calculated as an equivalent circle diameter with an image processing apparatus. In each specimen, the inclusions were mostly sulfides, oxides, and complex inclusions, and in addition, a small amount of nitrides and carbides were dispersed.
[0034]
FIG. 4 is a graph showing the relationship between the type of specimen and the ratio of inclusions having a particle diameter of 2 μm or more.
[0035]
As shown in FIG. 4, the specimens A to C had a ratio of inclusions having a particle diameter of 2 μm or more of 10% or more, and satisfied the scope of the present invention (the specimens A to C were represented by the present invention). Example). The test bodies D to I did not satisfy the scope of the present invention (the test bodies D to I are used as comparative examples).
[0036]
FIG. 5 is a graph showing the relationship between the cutting time and the tool wear amount for each specimen. Table 1 shows the magnetic properties (iron loss: W15 / 50 and magnetic flux density: B50) of each specimen.
[0037]
[Table 1]

[0038]
In FIG. 5, the specimens A to C, which are examples of the present invention, have a small amount of tool wear and good magnetic properties as shown in Table 1 (iron loss 7.0 (W / kg) or less, magnetic flux density 1.8 ( T) or more). Work materials D, E, and F, which are comparative examples, had a large amount of tool wear as shown in the figure, and also had poor magnetic properties as shown in Table 1. The specimens G, H, and I, which are comparative examples, had a small amount of tool wear as shown in the figure, but were inferior in magnetic properties as shown in Table 1.
[0039]
(Example 2)
Chemical composition is weight%, C: 0.002-0.003%, Mn: 0.1-0.3%, Si: 0.9-1.1%, Al: 0.3-0.5% , P: 0.06 to 0.08%, S: 0.0005 to 0.050%, O: 0.002 to 0.012, and the balance of Fe and inevitable impurities are melted by a conventional method. Then, hot rolling, cold rolling, and annealing were performed to produce non-oriented electrical steel sheets with numbers P to X. As a manufacturing condition, the number S increases the cold reduction rate, the number T decreases the S amount, the number U increases the hot rolling heating temperature, and the number V decreases the oxygen amount for the groups of the numbers P to R as manufacturing conditions. The number W increased the amount of oxygen, the number X decreased the amount of oxygen, and the hot rolling heating temperature was increased so that the particle sizes of various inclusions were obtained.
[0040]
An insulating film was applied to these steel plates to a final thickness of 0.35 mm. This steel plate was punched into a disk shape with four grooves on the outer periphery and laminated, and test pieces P to X for intermittent cutting were made corresponding to the numbers P to X. The intermittent cutting test conditions were cutting speed: 320 m / min, feed: 0.05 mm / rev, cutting depth: 0.05 mm, and a carbide tool was used as the cutting tool.
[0041]
Machinability (tool wear) and magnetic properties (iron loss, magnetic flux density) were evaluated in the same procedure as in Example 1.
In order to investigate the cutting burr generated in the notch groove portion of the work material, the length of the cutting burr was measured after a cutting time of 1200 seconds.
[0042]
FIG. 6 is a graph showing the relationship between the type of specimen and the ratio of inclusions having a particle diameter of 2 μm or more.
As shown in the figure, the specimens P to R have a ratio of inclusions having a particle diameter of 2 μm or more of 10% or more, and satisfy the scope of the present invention (the specimens P to R are represented by the present invention). Example). The test bodies S to X did not satisfy the scope of the present invention (the test bodies S to X are comparative examples).
[0043]
FIG. 7 is a graph showing the relationship between the cutting time and the tool wear amount for each specimen.
FIG. 8 is a graph showing the cutting burr length for each specimen. Table 2 shows the magnetic properties (iron loss: W15 / 50 and magnetic flux density: B50) of each specimen.
[0044]
[Table 2]

[0045]
As shown in FIG. 7, the specimens P, Q, and R of the example of the present invention had a small amount of tool wear, and the cutting burr length was small as shown in FIG. Moreover, as shown in Table 2, the magnetic properties of the test specimens P, Q, and R were good (iron loss 4.0 (W / kg) or less, magnetic flux density 1.8 (T) or more).
[0046]
As shown in FIG. 7, in the test bodies S and T of the comparative example, the tool wear amount was large, and the cutting burr length was also large as shown in FIG. Moreover, as shown in Table 2, the magnetic properties of the specimens S and T were also poor.
[0047]
In the test body U as a comparative example, a tool defect occurred during the cutting test, and the test was stopped, so data on tool wear and cutting burr length were not collected. Moreover, the magnetic characteristics of the test body U were also inferior.
[0048]
As shown in FIG. 7, for the test specimens V, W, and X, which are comparative examples, the tool wear amount was smaller than that of the test specimens S and T, and the cutting burr was relatively small as shown in FIG. As shown in FIG. 2, the magnetic properties were inferior.
[0049]
【The invention's effect】
The electrical steel sheet of the present invention satisfies both machinability and magnetic properties, and when performing assembly cutting on a laminated iron core, the life of the cutting tool is prolonged, and there is no generation of cutting burrs. Deburring work can be omitted.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the number of inclusions in steel and magnetic properties (iron loss W15 / 50).
FIG. 2 is a graph showing the relationship between the particle diameter of inclusions and the number ratio of inclusions.
FIG. 3 is a graph showing the relationship between inclusion particle diameter and the amount of wear of a cutting tool.
FIG. 4 is a graph showing the relationship between the type of specimen and the ratio of inclusions having a particle diameter of 2 μm or more.
FIG. 5 is a graph showing a relationship between a cutting time and a tool wear amount for each specimen.
FIG. 6 is a graph showing the relationship between the type of specimen and the ratio of inclusions having a particle diameter of 2 μm or more.
FIG. 7 is a graph showing the relationship between the cutting time and the amount of tool wear for each specimen.
FIG. 8 is a graph showing the cutting burr length for each specimen.

Claims

Chemical composition is mass%, C: 0.002-0.005%, Mn: 0.1-0.4%, Si: 0.1-1.1%, Al: 0.0001-0.5% , P: 0.05 to 0.08%, S: 0.005 to 0.050%, O: 0.002 to 0.020%, the balance being Fe and inevitable impurities, steel observed in the cross section of the particles of inclusions in the number of particles greater than the particle size 2μm is, the total number from 8,000 to 10,000 pieces / mm ² An electrical steel sheet excellent in machinability and magnetic properties, characterized by being 10% to 30% with respect to the number of particles having a particle diameter of 0.1 μm or more.