【０００１】
【発明の属する技術分野】
本発明は、金属部品、セラミックス部品等の研磨に用いる磁気研磨用砥粒に関する。
【０００２】
【従来の技術】
一般に、磁界中に磁気研磨用砥粒(磁化される性質と研磨する能力を兼ね備えた砥粒)を充填すると、磁場の影響により磁気研磨用砥粒は磁気ブラシを形成する。この磁気ブラシをひとつの研磨工具として利用し、工作物の円筒外周面、平面、曲面、多少の形状的複雑性のある面など、表面仕上げを行う砥粒加工法の一種が磁気研磨法である。
【０００３】
最近、この磁気研磨法が金型表面の仕上げ等の自動化、簡易化の手段として有用であるとされ、注目を集めている。
【０００４】
特許文献１には、Ｆｅに代表される強磁性金属のマトリクス中に、研磨材／強磁性金属＝（５〜４０）／（９５〜６０）(体積比)で研磨材粒子を分散させ、この強磁性金属に対してＡｌ、ＳｉまたはＢの少なくとも１種を脆化剤として添加することで粉砕を容易にし、砥粒製造の生産性を高めた磁気研磨用砥粒が開示されている。
【０００５】
また、特許文献２には、真球度が６０％以下で、平均粒子径が１〜１０００μｍの軟磁性フェライト粒子と研磨材からなる磁気研磨用砥粒が開示されている。
【０００６】
磁気研磨法に用いる磁気研磨用砥粒は、特許文献１および２に開示されているように、磁化される性質と研磨する能力を備えた一種の複合砥粒で、その主要構成は鉄等の強磁性体とアルミナ質砥粒等の高研磨材とから成っている。このような磁気研磨用砥粒は、鉄等の強磁性体と研磨材の微粉を加圧成形後、雰囲気炉で焼結させることで得られる。
【０００７】
また、例えば特許文献２に開示されているように、通常研磨用砥粒の粒径と仕上面粗さとは密接な関係があるが、磁気研磨法を用いた場合、粒径数百μｍの比較的粗い砥粒を使用しても表面粗さは、最大高さＲmax約２μｍのオーダーの仕上面粗さが得られる。これは、研磨時に磁力で結合された砥粒群が全体として柔軟な加工挙動をすることと、硬い研磨材成分の粒子が応力下で受けた加工歪を強磁性体である金属が分担し、緩和するからである。
【０００８】
また、磁気研磨における加工能率は、装置のファクターすなわち磁極の強さや回転周速度、被加工部品の送り速度、加工間隙等の諸条件のほか、砥粒が群を形成したときの粘弾性的な挙動にも左右される。従って、個々の砥粒の性状は、磁気研磨の研磨量や研磨精度を決定する重要な要素であり、その使用寿命をも決定する。
【０００９】
さらに、軟磁性フェライト成分に対する研磨材成分の含有量は５０重量％以下となっている。これは、軟磁性フェライト成分の磁気吸着力によって一定の加工圧力を得、研磨材成分の硬さによって被研磨物に対する研磨力を利用するものである。
【００１０】
【特許文献１】
特開平６−１１６５４９号公報
【特許文献２】
特開２００２−０８０８２６号公報
【００１１】
【発明が解決しようとする課題】
しかしながら、従来の磁気研磨用砥粒は、研磨材の種類が限られるうえに、研磨特性も十分満足できるものではなく、使用寿命が短いものであった。これは、研磨材粒子が金属粉末の焼結により結合しているという構成に起因するものであり、研磨材粒子であるＡｌ2Ｏ3やＣｅＯ2等のセラミックスと強磁性体である金属との密着性が低いことや、セラミックスの比重と金属の比重が大きく異なっているため、砥粒中に研磨材粒子が均一に分散していないこと等によるものであった。
【００１２】
以上の点を改善する試みとして、特許文献１に磁気研磨用砥粒のホットプレスによる圧密化、焼結、粉砕後の球状化処理などの技術が開示されているが、この様な方法は製造コストを高くするという欠点を有していた。
【００１３】
また、特許文献１の磁気研磨用砥粒のような、研磨材粒子が均一に分散した磁気研磨用砥粒を作製するためには、成形、金属溶融、粉砕などの多くの工程が必要なため製造コストが高かった。また、この強磁性金属から成る磁気研磨用砥粒を用いて研磨加工した場合、研磨量を増加させるために磁気研磨用砥粒の粒径を大きくすると、強磁性金属の磁力が強いため研磨面の表面粗さが大きくなるという問題があった。
【００１４】
また、特許文献２の磁気研磨用砥粒は、平均粒子径が１〜１０００μｍであるが、軟磁性フェライト成分と研磨材成分との結合力は軟磁性フェライト成分の粒子径によって左右され、軟磁性フェライト成分のうち大きな粒子径の粒子によって、軟磁性フェライトと研磨材の結合力が小さくなり、被研磨物の研磨量が極端に少なくなるという問題があった。
【００１５】
また、磁気研磨用砥粒がアスペクト比の小さい球状粒子であるため、被研磨物への磁気研磨用砥粒が被研磨物に対して平行に揃わずに接触しやすく、磁気研磨用砥粒と被研磨物との接触面積が小さくなるので、単位時間当たりの研磨量が減少し、加工時間を要するという問題があった。
【００１６】
そこで、本発明は、被研磨物の研磨量が多く、表面粗さが小さい面を得ることができるとともに、製造コストが安価である磁気研磨用砥粒を提供することを目的とする。
【００１７】
【課題を解決するための手段】
本発明の磁気研磨用砥粒は、軟磁性フェライト成分１５〜８５重量％と研磨材成分１５〜８５重量％を含有してなり、上記軟磁性フェライト成分の平均粒子径が０．５〜２０μｍであることを特徴とする。
【００１８】
また、本発明の磁気研磨用砥粒は、軟磁性フェライト成分１５〜８５重量％と研磨材成分１５〜８５重量％とを含有してなる磁気研磨用砥粒であって、該磁気研磨用砥粒の平均粒子径に対する上記軟磁性フェライト成分の平均粒子径の比が１０-5〜１０-1であることを特徴とする。
【００１９】
さらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の平均粒子径が５０〜５０００μｍであることを特徴とする。
【００２０】
さらにまた、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒のアスペクト比が１．５以上であることを特徴とする。
【００２１】
さらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の飽和磁束密度が０．０１テスラ以上であることを特徴とする。
【００２２】
またさらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の密度が５ｇ／ｃｍ3以上であることを特徴とする。
【００２３】
さらにまた、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の圧縮強度が５０ＭＰa以上であることを特徴とする。
【００２４】
本発明の磁気研磨用砥粒によれば、軟磁性フェライト成分１５〜８５重量％と研磨材成分１５〜８５重量％とを含有し、上記軟磁性フェライト成分の平均粒子径を０．５〜２０μｍに制御することによって、磁気研磨用砥粒内に含まれる軟磁性粒子数を増やし、かつ研磨材と軟磁性フェライト間の結合力を大きくすることができるため、磁気研磨用砥粒の強度を向上させると共に、被研磨物の表面加工における研磨量を増加させることができる。
【００２５】
また、本発明の磁気研磨用砥粒によれば、軟磁性フェライト成分１５〜８５重量％と研磨材成分１５〜８５重量％とを含有する磁気研磨用砥粒であって、該磁気研磨用砥粒の平均粒子径に対する上記軟磁性フェライト成分の平均粒子径の比を１０-5〜１０-1とすることによって、磁気研磨用砥粒内に含まれる軟磁性粒子数を増やし、かつ研磨材と軟磁性フェライト間の結合力を大きくすることができるため、磁気研磨用砥粒の強度を向上させると共に、被研磨物の表面加工における研磨量を増加させることができる。
【００２６】
さらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の平均粒子径が５０〜５０００μｍであることから、磁気研磨用砥粒の磁気吸着力が向上するので、さらに研磨量を増加させることができる。
【００２７】
さらにまた、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒のアスペクト比が１．５以上であることから、被研磨物へ磁気研磨用砥粒の長軸方向が接触し易くなるため、磁気研磨用砥粒と被研磨物との接触面積を大きくすることができる。これによって、単位時間当たりの研磨量をさらに増加させることができるとともに、被研磨物の単位面積当たりにかかる加工応力が小さくなるので、砥粒の回転磁心への付着力を保持したまま被研磨物の表面粗さを低減し、さらには研磨面の表面粗さが優れた研磨精度の高い被研磨物を得ることができる。
【００２８】
またさらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の飽和磁束密度が０．０１テスラ以上であることから、砥粒にかかる磁力が大きくなり、加工圧力が増加して被研磨物の研磨量をさらに増加させることができるとともに、磁気研磨用砥粒の磁力が大きいので研磨量を高精度に制御したり、被研磨物の加工精度を高精度に制御したりすることが可能となる。
【００２９】
また、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の密度が５ｇ／ｃｍ3以上であることから、被研磨物へ加工応力が加わった際、研磨用砥粒自身の破壊を有効に防止して、被研磨物の研磨量をさらに増加させることができる。
【００３０】
さらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の圧縮強度が５０ＭＰa以上であることから、被研磨物へ加工応力が加わった際、磁気研磨用砥粒自身の破壊を抑制することができるので、被研磨物の研磨量を増加させることができる。
【００３１】
【発明の実施の形態】
本発明の磁気研磨用砥粒は、軟磁性フェライトを主成分とする粒子（軟磁性フェライト成分）と研磨材を主成分とする粒子（研磨材成分）との複合粒子からなる。
【００３２】
上記軟磁性フェライト成分、研磨材成分とから成る磁気研磨用砥粒においては、各成分が添加混合され粒子を形成するものであり、上記軟磁性フェライト成分とは、磁場が印加された際に磁化されやすいものと定義する。
【００３３】
上記軟磁性フェライト成分は、強磁性体として作用し、Ｆｅ、Ｚｎ、Ｎｉ、Ｃｕ、Ｍｎ等を含有した軟磁性フェライト成分が好ましい。また、Ｆｅを５０モル％以上含有する軟磁性フェライト成分を用いることが、製造コストを低減しかつ磁気研磨用砥粒の磁気感応性を高くするために特に好ましい。
【００３４】
より好ましい組成範囲は、Ｍｎ系の軟磁性フェライト成分の場合は、Ｆｅ2Ｏ3を４０〜９５モル％、ＺｎＯを１〜３０モル％、ＭｎＯを１〜３０モル％、ＣｕＯを１０モル％以下含有し、Ｎｉ系の軟磁性フェライト成分の場合は、Ｆｅ2Ｏ3を４０〜９５モル％、ＺｎＯを１〜３０モル％、ＮｉＯを１〜３０モル％、ＣｕＯを１０モル％以下含有したものである。
【００３５】
なお、軟磁性フェライトの軟磁性とは磁場が印加された際に磁化されやすいものと定義されるものである。
【００３６】
また、上記研磨材成分としては、種々の酸化物セラミックス、非酸化物セラミックス又はダイヤモンドを用いることができ、より好ましくは酸化物セラミックスの粒子、具体的にはＡｌ2Ｏ3、ＺｒＯ2、ＳｉＯ2、Ｃｒ2Ｏ3、ＣｅＯ2等であり、これらの１種又は２種以上を混合したものである。
【００３７】
なお、本発明の磁気研磨用砥粒は、上記研磨材成分や上記軟磁性フェライト成分の他に非磁性成分を含んでいてもよい。例えば、ＣａＯ、Ｋ2Ｏ、ＭｇＯ、ＣｏＯ、Ｔａ2Ｏ5、Ｎｂ2Ｏ5、ＷＯ3、ＰｂＯ等を合計で２０重量％以下含んでもよい。
【００３８】
本発明の磁気研磨用砥粒は、軟磁性フェライト成分と研磨材成分との界面に、各成分が固溶した薄い粒界層を有するため、軟磁性フェライトを主成分とする粒子と研磨材を主成分とする粒子とを強固に結合させることができ、その結果機械的強度の特に高い磁気研磨用砥粒を提供することができる。
【００３９】
また、本発明の磁気研磨用砥粒は、軟磁性フェライト成分が１５〜８５重量％、研磨材成分が１５〜８５重量％との割合で含有してなり、上記軟磁性フェライト成分の平均粒子径が０．５〜２０μｍであることが重要である。
【００４０】
これにより、磁気研磨用砥粒内に含まれる軟磁性フェライト粒子数を増やし、かつ研磨材と軟磁性フェライト間の結合力を大きくすることができるため、磁気研磨用砥粒の強度を向上させるとともに、被研磨物の表面加工における研磨量を増加させることができる。
【００４１】
軟磁性フェライト成分が１５重量％未満の場合、および研磨材成分が８５重量％を越える場合は、磁気研磨用砥粒の磁気吸着力が低下することにより、被研磨物への加工圧力が低下し、被研磨物の研磨量が減少する。一方、軟磁性フェライト成分が８５重量％を越える場合、および研磨材成分が１５重量％未満の場合は、研磨成分が少なくなり、磁気研磨用砥粒の軟磁性フェライトと研磨材成分の結合力が低下するため、磁気研磨用砥粒の強度が低下し、被研磨物の研磨量が減少する。
【００４２】
また、軟磁性フェライト成分の平均粒子径は０．５〜２０μｍに特定される。これにより、軟磁性フェライト成分の研磨材へ結合力が高まり、磁気研磨砥粒の強度が向上し、研磨の際に砥粒が破壊しにくくなり、被研磨物の研磨量が多くなる。
【００４３】
軟磁性フェライト成分の平均粒子径が０．５μｍ未満の場合は、軟磁性フェライト成分の磁気特性が低下するため被研磨物の研磨量が減少するからであり、２０μｍよりも大きい場合は、軟磁性フェライト成分と研磨材成分との結合力が減少するので被研磨物の研磨量が減少するからである。これは結合力が低下すると磁気研磨用砥粒の機械的強度が低下し、研磨の際に磁気研磨用砥粒に加わる研磨圧力によって磁気研磨用砥粒が破壊しやすくなるためであると考えられる。結合力を大きくして磁気研磨用砥粒の機械的強度を更に向上させるためには、粒界層の平均厚みが３μｍ以下であることが好ましく、このような磁気研磨用砥粒とするには、軟磁性フェライト成分中に含まれるＣｕＯのモル％を５〜１０モル％とすることで得られる。
【００４４】
また、本発明の磁気研磨用砥粒は、磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比が１０-5〜１０-1であることが重要である。
【００４５】
これにより、磁気研磨用砥粒内に含まれる軟磁性粒子数を増やし、かつ研磨材と軟磁性フェライト間の結合力を大きくすることができるため、磁気研磨用砥粒の強度を向上させると共に、被研磨物の表面加工における研磨量を増加させることができる。
上記磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比が１０-5未満の場合は、軟磁性フェライト成分の磁気特性が低下するため被研磨物の研磨量が減少するからであり、１０-1よりも大きい場合は上記結合力の低下により被研磨物の研磨量が減少するからである。
【００４６】
なお、上記軟磁性フェライトの平均粒子径は、磁性研磨用砥粒をＳＥＭ、実体顕微鏡または拡大鏡などを用いて写真を撮り、２０個以上の各磁気研磨用砥粒内に観察される、軟磁性フェライト粒子２０個以上を無作為に選び、選んだ軟磁性粒子の各々の内接円と外接円の直径の平均値を更に平均した値をいう。ただし、平均粒子径が０．２μｍ以下の軟磁性フェライトは、粒径測定が困難のため、上記軟磁性フェライト粒子の平均粒子径の対象外とする。
【００４７】
また、上記磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比とは、軟磁性フェライトの平均粒子径を磁気研磨用砥粒の平均粒子径で割ったものであり、上記磁気研磨用砥粒の平均粒子径は、磁性研磨用砥粒をＳＥＭ、実体顕微鏡または拡大鏡などで写真を撮り、無作為に１０個選んだ各磁性研磨用砥粒に接する内接円と外接円の直径の平均値を更に平均した値とする。ただし、平均粒子径が０．２μｍ以下の磁気研磨用砥粒は、粒径測定が困難のため、磁気研磨用砥粒の平均粒子径の対象外とする。
【００４８】
さらに、本発明の磁気研磨用砥粒は、上記磁気研磨用砥粒の平均粒子径が５０〜５０００μｍであることが好ましく、被研磨物の表面加工における研磨量をより多くすることができる。上記磁気研磨用砥粒の平均粒子径が５０μｍ未満とした場合、被研磨物の研磨量が低下し、一方、５０００μｍを超える場合、研磨精度を高く維持したまま研磨面の表面粗さを小さくすることができない。
【００４９】
また、本発明の磁気研磨用砥粒は、その平均粒子径を５０〜５０００μｍ、その短軸方向の平均長さを５０〜１０００μｍ、長軸方向の平均長さを７５〜５０００μｍとすることが特に好ましい。この理由は、被研磨物の研磨量を特に増加させ、研磨精度を特に向上させることができるからである。
【００５０】
さらに、本発明の磁気研磨用砥粒は、アスペクト比が１．５以上であることが好ましく、例えば図1に示す本発明の磁気研磨用砥粒の集合体の拡大斜視図のように、磁気研磨用砥粒１の各粒子の形状が柱状をなし、磁気研磨用砥粒の回転磁心への付着力を保持したまま、磁気研磨用砥粒の長軸方向の面が回転磁心方向へ付着するため、磁気研磨用砥粒の被研磨物への接触面積を大きくすることができ、被研磨物の単位時間当たりの研磨量を増加させることができる。また、被研磨物の単位面積当たりにかかる加工応力が小さくなることから、研磨面の表面粗さが優れた研磨精度の高い被研磨物を得ることができる。
【００５１】
研磨時の磁場中では磁束が磁気研磨用砥粒の端部に集中しやすいため、上記アスペクト比が１．５未満の場合、磁気研磨用砥粒の回転磁心及び被研磨物への接触が長軸方向に揃い難く、長軸、短軸方向にランダムに接触することになり、その結果研磨面の表面粗さを優れたものにできず、研磨量の向上が著しくない。
【００５２】
また、上記アスペクト比は２０以下とすることがより好ましく、被研磨物の研磨量をより増加させ、研磨精度を特に向上させることができる。これはアスペクト比が大きくなり過ぎると、一定の平均粒子径を有する粒子において、その形状が糸状に近いものとなり、強度が低下することから研磨量を著しく向上させることができないからである。
【００５３】
なお、上記アスペクト比とは、磁性研磨用砥粒のＳＥＭ、実体顕微鏡又は、拡大鏡などで写真を撮り、任意に１０個取り出した各磁性研磨用砥粒の長軸方向の長さと短軸方向の長さの比を求め、これらを平均した値のことである。
【００５４】
ここで、アスペクト比が１．５以上の磁気研磨用砥粒を作製する方法としては、例えば軟磁性フェライト粒子、研磨材粒子、および有機バインダーを混合、混練してコンパウンドとし、棒状や角棒等に押し出し成形を行いチョッパーにて寸断し、その後酸化雰囲気にて焼成する。
【００５５】
また、本発明の磁気研磨用砥粒は、飽和磁束密度を０．０１テスラ以上とすることが好ましく、被研磨物への磁気研磨用砥粒の加工力を大きくして研磨量をさらに増加させることができる。なお、飽和磁束密度は振動磁力計にて求めることができる。
【００５６】
さらに、本発明の磁気研磨用砥粒は、密度を５ｇ／ｃｍ3以上とすることが好ましく、被研磨物に加工応力が加わった際、研磨用砥粒自身の破壊を有効に防止し、被研磨物の研磨量をさらに多くすることができる。なお、上記密度は、ＪＩＳ Ｒ１６２０（１９９５）に準拠した粒子密度測定方法で測定する。
【００５７】
またさらに、本発明の磁気研磨用砥粒は、圧縮強度が５０ＭＰa以上とすることが好ましく、被研磨物に加工応力が加わった際、研磨砥粒自身の破壊を防止し、被研磨物の研磨量を多くすることができる。なお、上記圧縮強度は、例えば微少圧縮試験機(島津製)を用いて測定する。
【００５８】
上述のように磁気研磨用砥粒の飽和磁束密度を０．０１テスラ以上、密度を５ｇ／ｃｍ3以上及び圧縮強度を５０ＭＰａ以上とするには、詳細を後述の製造方法において説明するように仮焼温度、焼成温度、焼成時間を制御することによってできる。
【００５９】
本発明の磁気研磨用砥粒の製造方法は例えば次の通りである。
【００６０】
軟磁性フェライト粒子１５〜８５重量％と研磨材粒子１５〜８５重量％とを含有する複合粒子を作製する。軟磁性フェライト粒子は、Ｆｅ、Ｚｎ、Ｎｉ、Ｃｕ及びＭｎの酸化物、または焼成によりこれらの酸化物を生成する炭酸塩、硝酸塩等の金属塩を用い、ＭｎＺｎ系の軟磁性フェライトの場合は、Ｆｅ2Ｏ3を４０〜９５モル％、ＺｎＯを１〜３０モル％、ＭｎＯを１〜３０モル％、ＣｕＯを１０モル％以下含有する組成、ＮｉＺｎ系の軟磁性フェライトの場合は、Ｆｅ2Ｏ3を４０〜９５モル％、ＺｎＯを１〜３０モル％、ＮｉＯを１〜３０モル％、ＣｕＯを１０モル％以下含有する組成とする。研磨材粒子の組成としては、Ａｌ、Ｚｒ等の酸化物例えばＡｌ2Ｏ3、ＺｒＯ2、ＳｉＯ2、Ｃｒ2Ｏ3、ＣｅＯ2あるいは焼成によりこれらの酸化物を生成する炭酸塩、硝酸塩等の金属塩を１種又は２種以上を含有する組成とする。これらの軟磁性粒子２０〜８０重量％と研磨材粒子２０〜８０重量％とを混合し、振動ミル等で粉砕、仮焼後、有機バインダーを加えてニーダーで混練しコンパウンドとなし、棒状に押し出すと同時にチョッパーにて寸断して所望のアスペクト比に調整した原料顆粒を得、その後焼成する。
【００６１】
また、成形方法としては、加圧成形、射出成形、アトマイズ法、延伸急冷法、ロール法等を用いることができる。例えば、加圧成形の場合は、仮焼して得られた原料にバインダーを加え種々の造粒機にて造粒し、所定のアスペクト比の金型に原料を充填し加圧成形すればよい。射出成形の場合は、仮焼して得られた原料に可塑性バインダーを加えスラリーを作成し、そのスラリーを所定のアスペクト比に設計した金型へ射出し、熱硬化させることによって、所望のアスペクト比の磁気研磨用砥粒を得ることができる。
【００６２】
このような製造方法によって得られた磁気研磨用砥粒の個々の粒子は、軟磁性フェライト成分と研磨材成分とが強固に焼結したものとなる。
【００６３】
上述の製造方法において、磁気研磨用砥粒の軟磁性フェライト成分の平均粒子径を０．５〜２０μｍとするには、一次原料の選定、仮焼条件の制御、仮焼後の粉砕条件の制御が特に重要である。
【００６４】
軟磁性フェライトの一次原料については、その平均粒子径が１０μｍ以下とすることで、仮焼、焼成の段階で結晶粒成長が生じても軟磁性フェライト成分の平均粒子径を０．５〜２０μｍとすることができる。
【００６５】
そして、磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を１０-5〜１０-1とするには、軟磁性フェライト成分と研磨材成分を造粒することによって磁気研磨用砥粒となる粉末を得る際に乾式造粒機等の条件を変更することで調整する。
【００６６】
また、仮焼条件については、大気雰囲気中で７５０〜９００℃の範囲で１〜１０時間仮焼することが重要であり、７５０℃未満の温度で１時間未満の保持であると軟磁性フェライトが完全にフェライト化しないので磁気特性が低下するためであり、９００℃を越えた温度で１０時間を超えて保持するとフェライト成分が一部蒸発することにより磁気特性が低下するからである。また、軟磁性フェライト成分の平均粒子径を最低でも０．５μｍとするには、仮焼後の粉砕において十分な粉砕を行う必要がある。十分な粉砕は、例えば湿式のボールミルやビーズミルにおいて、ＺｒＯ2ボールを用いて粉砕することにより可能となる。
【００６７】
また、上述した一次原料の選定、仮焼条件の制御、仮焼後の粉砕条件の制御は、ＭｎＺｎ系の軟磁性フェライト、ＮｉＺｎ系の軟磁性フェライトを含有する磁気研磨用砥粒を製造方法するために特に重要であり、被研磨物の研磨量が特に多く、表面粗さが特に小さな被研磨物を得るための磁気研磨用砥粒を製造することができる。
【００６８】
また、最終的な磁気研磨用砥粒のアスペクト比を１．５以上とするには、押し出し成形によって調整する場合、押し出し後の寸断の長さを制御することが必要である。例えば、１０００μｍ角の直方体形状をなす砥粒を得る場合、押し出し速度を１０００μｍ／ｓ、寸断時間を１．５秒／回以上とする必要がある。
【００６９】
さらに、得られた磁気研磨用砥粒の飽和磁束密度を０．０１テスラ以上、密度を５ｇ／ｃｍ3以上、圧縮強度を５０ＭＰａ以上とするには、焼結を促進しなければならないため、大気雰囲気中７５０〜９００℃の範囲で１〜１０時間仮焼し、大気雰囲気中で約１０００〜１１００℃の範囲で１０〜２０時間焼成することが必要である。焼成温度が１０００℃未満となると、焼結が十分促進しないため十分な圧縮強度が得られず１１００℃を超えると軟磁性フェライト成分が大量に蒸発してしまい、密度、圧縮強度とも減少するためである。
【００７０】
なお、研磨材成分は仮焼後に加えることを拘束するものではなく、仮焼前に軟磁性フェライト成分に加えても本発明の磁気研磨用砥粒の特性に何ら影響するものではない。
【００７１】
本発明は上述の実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲であれば種々の変更は可能である。図１には形状が柱状体形状の磁気研磨用砥粒を示したが、楕円体形状、直方体形状、針状形状等の様々の形状のアスペクト比１．５以上の磁気研磨用砥粒を用いても、同様に研磨量が多く、表面粗さの優れた加工が可能となる。
【００７２】
【実施例】
（実施例１）
Ｆｅ2Ｏ3、ＺｎＯ、ＮｉＯ、ＣｕＯ及びＭｎＯから成る軟磁性フェライト成分を振動ミルで混合した後、６００〜１０００℃で仮焼することにより仮焼体を得た。この仮焼体に、研磨材成分としてＡｌ2Ｏ3の量を表１のように変化させて加え、ボールミルにて粉砕した後、バインダーを加え、スプレードライヤーを用いて任意の形状、大きさを有する造粒体を得た。そして、この造粒体を大気雰囲気中９５０〜１４００℃で焼成することにより試料Ｎｏ．１〜１４を得た。
【００７３】
以上のような試料をそれぞれフライス盤に磁極を取り付けて回転させた装置で使用して、次の条件で磁気研磨を行った。
【００７４】
回転磁極：直径２０ｍｍ 回転磁極の先端部曲率半径：１０ｍｍ
回転磁極の回転数：２０００ｒｐｍ 被研磨物：Ｓ５５Ｃ鋼 砥粒：２．５ｇ
磁束密度Ｔ：１．０テスラ 磁極と被研磨物のギャップＧ：１．４ｍｍ
研磨時間：１５分間 研磨前表面粗さＲｙ：２μｍ
各砥粒に関して得られた研磨量の測定値を軟磁性フェライト成分の重量％、軟磁性フェライトの平均粒子径とともに表１に示す。
【００７５】
表１に示す結果より、軟磁性フェライト成分の平均粒子径が、０．５〜２０μｍの試料Ｎｏ．２〜６を用いた場合は研磨量が１８０ｍｇ以上と多く優れた研磨特性が得られた。
【００７６】
一方、軟磁性フェライト成分の平均粒子径が、０．５μｍ未満または２０μｍを超える試料Ｎｏ．１、７、８を用いた場合は研磨量が１６０ｍｇ以下と少なかった。
【００７７】
また、軟磁性フェライト成分の重量％が、１５〜８５重量％の試料Ｎｏ．１１〜１４を用いた場合は研磨量が１８０ｍｇ以上と多く優れた研磨特性が得られた。
【００７８】
一方、軟磁性フェライト成分の重量％が、１５重量％未満で８５重量％を超える試料Ｎｏ．９、１０を用いた場合は研磨量が１７０ｍｇ以下と少なかった。
【００７９】
【表１】
【００８０】
（実施例２）
次に、実施例１と同様な方法で軟磁性フェライト成分の平均粒子径を種々変化させ、軟磁性フェライト成分の平均粒子径対する上記磁気研磨用砥粒の平均粒子径の比を１０-5〜１０-1とした磁気研磨用砥粒を作成した。
【００８１】
磁気研磨は実施例１と同条件にて行った。
【００８２】
磁気研磨用砥粒の軟磁性フェライト成分の重量％と平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を種々変更し、各砥粒を用いた場合の研磨量の測定値を表２に示した。
【００８３】
磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を１０-5〜１０-1とした試料Ｎｏ.１６〜２０を用いた場合は、研磨量が１９０ｍｇ以上と多くなり優れた研磨特性が得られた。
【００８４】
一方、軟磁性フェライト成分の平均粒子径に対する磁気研磨用砥粒の平均粒子径の比が、１０-5未満で、１０-1を超える試料Ｎｏ．１５、２１、２２を用いた場合は、研磨量が１５５ｍｇ以下と研磨量が少なくなった。
また、軟磁性フェライト成分の重量％が、１５〜８５重量％の試料Ｎｏ．２５〜２８を用いた場合は研磨量が１９０ｍｇ以上と多く優れた研磨特性が得られた。
【００８５】
一方、軟磁性フェライト成分の重量％が、１５重量％未満で８５重量％を超える試料Ｎｏ．２３、２４を用いた場合は研磨量が１７０ｍｇ以下と少なかった。
【００８６】
【表２】
【００８７】
（実施例３）
次に、軟磁性フェライト成分の平均粒子径を０．５〜２０μｍとし、平均粒子径を１０〜６０００μｍとした磁気研磨用砥粒を作製した。
【００８８】
なお、磁気研磨は実施例１と同条件にて行った。研磨材成分の含有量は、いずれも軟磁性フェライト成分に対し５０重量％とした。
【００８９】
各砥粒に関して得られた研磨量と表面粗さの測定値を磁気研磨用砥粒の平均粒子径と共に表３に示した。
【００９０】
なお、表面粗さの測定は、ＪＩＳＢ０６０１に基づき算術平均粗さ（Ｒａ）を触針式表面粗さ計にて測定した。
【００９１】
表３に示した結果より、平均粒子径を５０〜５０００μｍとした磁気研磨用砥粒とした試料Ｎｏ.３０〜３４を用いた場合は、研磨量が２１０ｍｇ以上と多く、表面粗さＲａが０．２μｍ以下と研磨精度が優れていた。
【００９２】
また、磁気研磨用砥粒の平均粒子径が５０μｍ未満の試料Ｎｏ．２９を用いた場合は研磨量が２００ｍｇ以下と少なかった。
【００９３】
一方、磁気研磨用砥粒の平均粒子径が５０００μｍを超える試料Ｎｏ．３５を用いた場合は、表面粗さＲａが０．２μｍ以上と研磨精度を著しく向上させることはできなかった。
【００９４】
【表３】
【００９５】
（実施例４）
先ず、Ｆｅ2Ｏ3、ＺｎＯ、ＮｉＯ、ＣｕＯ及びＭｎＯから成る軟磁性フェライト成分を振動ミルで混合した後、７５０〜９００℃で１〜１０時間仮焼することにより仮焼体を得た。この仮焼体に研磨材成分としてＡｌ2Ｏ3を５０重量％加え、ボールミルにて粉砕、混合した後、バインダーを加えてニーダーで混練しコンパウンドとなし、押し出し成形機を用いて所望のアスペクト比を有する顆粒を得た。
【００９６】
なお、磁気研磨用砥粒の平均粒子径は約１０００μｍ、軟磁性フェライト成分の平均粒子径は１０μｍとし、磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を１０-2とした。
【００９７】
そして、この顆粒を大気雰囲気中にて１０００〜１１００℃で焼成することにより表４に示す試料Ｎｏ．３６〜４０の軟磁性フェライト及び研磨材成分からなる磁気研磨用砥粒を得た。
【００９８】
得られた各試料のアスペクト比は、ＳＥＭで写真を撮影し、任意に１０個の粒子を取り出し、各磁気研磨用砥粒の長軸方向の長さと短軸方向の長さの比を求め、これらの平均を算出した。
【００９９】
表４より明らかなように、磁気研磨用砥粒のアスペクト比が１．５以上の試料（Ｎｏ．３８〜４０）を用いた場合は研磨量が２２０ｍｇ以上と多く、研磨後の被研磨物の表面粗さ（Ｒａ）が０．１０μｍ以下と特に滑らかとなった。
【０１００】
これに対し、磁気研磨用砥粒のアスペクト比が１.５より小さな試料（Ｎｏ．３６、３７）を用いた場合は、研磨量が２００ｍｇ以下となり著しく研磨量を増大させることができず、また、研磨後の被研磨物の表面粗さ（Ｒａ）が０．１５μｍ以上となり著しく滑らかな面を得ることができなかった。
【０１０１】
【表４】
【０１０２】
（実施例５）
次に、実施例１と同様な方法で種々の飽和磁束密度を有する磁気研磨用砥粒試料を作製した。
【０１０３】
研磨条件は、実施例１と同様であり、研磨材成分としてＡｌ2Ｏ3を用い、その含有量を軟磁性フェライト成分に対し５０重量％とした試料Ｎｏ．４１〜４４を作製した。
【０１０４】
なお、磁気研磨用砥粒の平均粒子径を約１０００μｍ、軟磁性フェライト成分の平均粒子径を１０μｍ、磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を１０-2、各試料のアスペクト比を１．７とし、飽和磁束密度は振動型磁力計を用いて求めた。
【０１０５】
そして、各試料を用いて実施例1と同様な条件で研磨を行い、各被研磨物の研磨量を測定した。
【０１０６】
その結果を表５に示した。
【０１０７】
表５より明らかなように、飽和磁束密度が０．０１テスラ以上の試料（Ｎｏ.４２〜４４）は、研磨量が２３０ｍｇと大きく、飽和磁束密度の小さな試料（Ｎｏ．４１）に比し、２０ｍｇ以上も研磨量が増加していることが判った。
【０１０８】
【表５】
【０１０９】
（実施例６）
次に、実施例１と同様な方法で種々の密度、圧縮強度を有する磁気研磨用砥粒を作成した。
【０１１０】
磁気研磨は実施例１と同条件で行った。研磨材成分としてＡｌ2Ｏ3を用い、その含有量を軟磁性フェライト成分に対し５０重量％とした試料を作製した。
【０１１１】
なお、磁気研磨用砥粒の平均粒子径を約１０００μｍ、軟磁性フェライト成分の平均粒子径を１０μｍ、磁気研磨用砥粒の平均粒子径に対する軟磁性フェライト成分の平均粒子径の比を１０-2、各試料のアスペクト比を１．７、飽和磁束密度を０．１テスラとし、密度はＪＩＳ Ｒ１６２０（１９９５）に準拠した粒子密度測定方法で、圧縮強度は微少圧縮試験機(島津製)を用いて求めた。
【０１１２】
各試料を用いて実施例1と同様な条件で研磨したＳ５５Ｃ鋼の研磨量の測定値を表６に示した。
【０１１３】
表６より、研磨材の密度が５ｇ／ｃｍ3以上、圧縮強度が５０ＭＰａ以上の試料（Ｎｏ．４９、５０、５２、５３）を用いた場合は、研磨量が２８０ｍｇ以上と特に多くなった。
【０１１４】
これに対し、密度が４.５ｇ／ｃｍ3、または圧縮強度が１０ＭＰａの試料（Ｎｏ．４５〜４８、５１）を用いた場合は、研磨量が２４０〜２６０ｍｇとなった。
【０１１５】
【表６】
【０１１６】
【発明の効果】
本発明の磁気研磨用砥粒によれば、軟磁性フェライト成分１５〜８５重量％と上記研磨材成分１５〜８５重量％とを含有してなり、上記軟磁性フェライト成分の平均粒子径を０．５〜２０μｍとすることにより、磁気研磨用砥粒の強度を向上させると共に、被研磨物の表面加工における研磨量を向上させることができる。
【０１１７】
また、本発明の磁気研磨用砥粒によれば、軟磁性フェライト成分１５〜８５重量％と研磨材成分１５〜８５重量％とを含有してなり、上記軟磁性フェライト成分の平均粒子径に対する上記磁気研磨用砥粒の平均粒子径の比が１０-5〜１０-1とすることにより、磁気研磨用砥粒の強度を向上させると共に、被研磨物の表面加工における研磨量を向上させることができる。
【０１１８】
さらに、本発明の磁気研磨用砥粒によれば、磁気研磨用砥粒の平均粒子径を５０〜５０００μｍに制御することによって、単位時間当たりの研磨量をさらに増加させることができるとともに、被研磨物の単位面積当たりにかかる加工応力が小さくなるので、砥粒の回転磁心への付着力を保持したまま被研磨物の表面粗さを低減し、さらには研磨面の表面粗さが優れた研磨精度の高い被研磨物を得ることができる。
【０１１９】
さらに、本発明の磁気研磨用砥粒によれば、軟磁性フェライト粒子からなるアスペクト比が１．５以上であることから、被研磨物への磁気研磨用砥粒の接触形態が長軸方向に揃い易く、被研磨物への接触面積が大きくなることによって単位時間当たりの研磨量が増加するとともに、単位面積当たりにかかる加工応力が小さくなり、砥粒の回転磁心への付着力を保持したまま、被研磨物の表面粗さの優れた研磨精度の高いものとすることができる。
【０１２０】
さらに、本発明の磁気研磨用砥粒によれば、砥粒の飽和磁束密度を０．０１テスラ以上としたことから、砥粒にかかる磁力が大きくなり、加工圧力が増加して被研磨物の研磨量をさらに多くすることができるとともに、磁気研磨用砥粒の磁力が大きいので研磨量を高精度に制御したり、被研磨物の加工精度を高精度に制御したりすることが可能となる。
【０１２１】
またさらに、本発明の磁気研磨用砥粒によれば、密度を５ｇ／ｃｍ3以上としたことから、被研磨物へ加工応力が加わった際、研磨用砥粒自身の破壊を有効に防止して、被研磨物の研磨量をさらに多くすることができる。
【０１２２】
またさらに、本発明の磁気研磨用砥粒は、圧縮強度が５０ＭＰa以上であることから、被研磨物へ加工応力が加わった際、研磨砥粒自身の破壊を抑制することができるので、被研磨物の研磨量を多くすることができる。
【図面の簡単な説明】
【図１】本発明の磁気研磨用砥粒の一実施形態を示す拡大斜視図である。
【符号の説明】
１：磁気研磨用砥粒
２：被研磨物[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to magnetic polishing abrasive grains used for polishing metal parts, ceramic parts, and the like.
[0002]
[Prior art]
Generally, when magnetic polishing abrasive grains (abrasive grains having both magnetizing properties and polishing ability) are filled in a magnetic field, the magnetic polishing abrasive grains form a magnetic brush under the influence of the magnetic field. Magnetic polishing is a type of abrasive processing that uses this magnetic brush as a single polishing tool to finish the surface of the workpiece, such as the outer peripheral surface of a cylinder, a flat surface, a curved surface, or a surface with some form of complexity. .
[0003]
Recently, the magnetic polishing method is considered to be useful as a means for automation and simplification of finishing of a mold surface, and has attracted attention.
[0004]
In Patent Literature 1, abrasive particles are dispersed in a matrix of a ferromagnetic metal represented by Fe at a ratio of abrasive / ferromagnetic metal = (5 to 40) / (95 to 60) (volume ratio). An abrasive for magnetic polishing has been disclosed in which at least one of Al, Si and B is added to a ferromagnetic metal as an embrittlement agent to facilitate pulverization and increase productivity in the production of an abrasive.
[0005]
Patent Document 2 discloses magnetic polishing abrasive grains comprising soft magnetic ferrite particles having a sphericity of 60% or less and an average particle diameter of 1 to 1000 μm and an abrasive.
[0006]
The abrasive grains for magnetic polishing used in the magnetic polishing method are, as disclosed in Patent Documents 1 and 2, a kind of composite abrasive grains having the property of being magnetized and the ability to polish. It is made of a ferromagnetic material and a high abrasive such as alumina abrasive grains. Such magnetic polishing abrasive grains can be obtained by subjecting a ferromagnetic material such as iron and fine powder of an abrasive to pressure molding and then sintering in an atmosphere furnace.
[0007]
Further, for example, as disclosed in Patent Document 2, although the particle size of the abrasive grains for polishing and the roughness of the finished surface have a close relationship, when the magnetic polishing method is used, the particle size is several hundred μm. The surface roughness is the maximum height R max A finished surface roughness on the order of about 2 μm is obtained. This is because the abrasive grains combined by magnetic force at the time of polishing have a flexible processing behavior as a whole, and the metal that is a ferromagnetic material shares the processing strain received by the particles of the hard abrasive component under stress, It is because it is relaxed.
[0008]
In addition, the processing efficiency in magnetic polishing depends on the factors of the equipment, such as the strength of the magnetic pole, the rotational peripheral speed, the feed speed of the workpiece, the processing gap, etc., as well as the viscoelasticity when the abrasive grains form a group. It also depends on the behavior. Therefore, the properties of the individual abrasive grains are important factors that determine the polishing amount and polishing accuracy of magnetic polishing, and also determine the service life thereof.
[0009]
Further, the content of the abrasive component relative to the soft magnetic ferrite component is 50% by weight or less. In this method, a certain processing pressure is obtained by the magnetic attraction force of the soft magnetic ferrite component, and the polishing force on the object to be polished is used by the hardness of the abrasive component.
[0010]
[Patent Document 1]
JP-A-6-116549
[Patent Document 2]
JP-A-2002-080826
[0011]
[Problems to be solved by the invention]
However, the conventional abrasives for magnetic polishing have a limited use of abrasives, have insufficient polishing characteristics, and have a short service life. This is due to the configuration in which the abrasive particles are bonded by sintering of the metal powder, and the abrasive particles Al Two O Three And CeO Two Due to the low adhesion between ceramics such as ferromagnetic metals and the fact that the specific gravity of ceramics and the specific gravity of metal are significantly different, the abrasive particles are not evenly dispersed in the abrasive grains. Was something.
[0012]
As an attempt to improve the above points, Patent Document 1 discloses techniques such as consolidation, sintering, and spheroidizing after grinding of abrasive grains for magnetic polishing. It has the disadvantage of increasing costs.
[0013]
Further, in order to produce magnetic polishing abrasive grains in which abrasive particles are uniformly dispersed, such as the magnetic polishing abrasive grains of Patent Document 1, many steps such as molding, metal melting, and pulverization are required. Manufacturing costs were high. Also, in the case of polishing using magnetic abrasive grains made of this ferromagnetic metal, if the grain diameter of the magnetic abrasive grains is increased to increase the polishing amount, the magnetic force of the ferromagnetic metal is strong, so that the polishing surface However, there was a problem that the surface roughness became large.
[0014]
In addition, the abrasive grains for magnetic polishing disclosed in Patent Document 2 have an average particle diameter of 1 to 1000 μm, but the bonding force between the soft magnetic ferrite component and the abrasive component depends on the particle size of the soft magnetic ferrite component, Among the ferrite components, particles having a large particle diameter cause a problem that the bonding force between the soft magnetic ferrite and the abrasive is reduced, and the amount of polishing of the object to be polished is extremely reduced.
[0015]
In addition, since the abrasive grains for magnetic polishing are spherical particles having a small aspect ratio, the abrasive grains for magnetic polishing on the object to be polished are likely to come into contact with the object to be polished without being aligned in parallel, and the abrasive grains for magnetic polishing are Since the contact area with the object to be polished is reduced, the amount of polishing per unit time is reduced, and there is a problem that processing time is required.
[0016]
Therefore, an object of the present invention is to provide a magnetic polishing abrasive grain that can obtain a surface having a large polishing amount and a small surface roughness and is inexpensive to manufacture.
[0017]
[Means for Solving the Problems]
The abrasive for magnetic polishing of the present invention contains 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of an abrasive component, and the soft magnetic ferrite component has an average particle diameter of 0.5 to 20 μm. There is a feature.
[0018]
Further, the magnetic polishing abrasive grain of the present invention is a magnetic polishing abrasive grain containing 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of an abrasive component. The ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the particles is 10 -Five -10 -1 It is characterized by being.
[0019]
Further, the abrasive grains for magnetic polishing of the present invention are characterized in that the average grain diameter of the abrasive grains for magnetic polishing is 50 to 5000 μm.
[0020]
Furthermore, the magnetic polishing abrasive grain of the present invention is characterized in that the magnetic polishing abrasive grain has an aspect ratio of 1.5 or more.
[0021]
Further, the magnetic polishing abrasive grain of the present invention is characterized in that the magnetic polishing abrasive grain has a saturation magnetic flux density of 0.01 Tesla or more.
[0022]
Still further, in the abrasive for magnetic polishing of the present invention, the density of the abrasive for magnetic polishing is 5 g / cm. Three It is characterized by the above.
[0023]
Furthermore, the abrasive for magnetic polishing of the present invention is characterized in that the compressive strength of the abrasive for magnetic polishing is 50 MPa or more.
[0024]
According to the abrasive for magnetic polishing of the present invention, the abrasive contains 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of an abrasive component, and has an average particle diameter of 0.5 to 20 μm. By increasing the number of soft magnetic particles contained in the magnetic polishing abrasive grains and increasing the bonding force between the abrasive and the soft magnetic ferrite, the strength of the magnetic polishing abrasive grains is improved. At the same time, the polishing amount in the surface processing of the object to be polished can be increased.
[0025]
According to the magnetic polishing abrasive grain of the present invention, the magnetic polishing abrasive grain contains 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of an abrasive component. The ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the particles is 10 -Five -10 -1 By increasing the number of soft magnetic particles contained in the magnetic polishing abrasive grains and increasing the bonding force between the abrasive and the soft magnetic ferrite, the strength of the magnetic polishing abrasive grains is improved. At the same time, the polishing amount in the surface processing of the object to be polished can be increased.
[0026]
Further, since the average particle diameter of the magnetic polishing abrasive grains of the present invention is 50 to 5000 μm, the magnetic attraction force of the magnetic polishing abrasive grains is improved, so that the polishing amount is further increased. Can be done.
[0027]
Furthermore, since the magnetic abrasive grains of the present invention have an aspect ratio of the magnetic abrasive grains of 1.5 or more, the long axis direction of the magnetic abrasive grains easily comes into contact with an object to be polished. Therefore, the contact area between the abrasive for magnetic polishing and the object to be polished can be increased. As a result, the polishing amount per unit time can be further increased, and the processing stress applied per unit area of the object to be polished is reduced, so that the object to be polished while maintaining the adhesion of the abrasive grains to the rotating magnetic core is maintained. The surface roughness of the polished surface can be reduced, and an object to be polished having excellent polishing surface roughness and high polishing accuracy can be obtained.
[0028]
Furthermore, the magnetic polishing abrasive grain of the present invention has a saturation magnetic flux density of 0.01 tesla or more, so that the magnetic force acting on the abrasive grain increases, and the processing pressure increases, thereby increasing the coating pressure. The polishing amount of the polished object can be further increased, and the magnetic force of the abrasive grains for magnetic polishing is large, so that the polishing amount can be controlled with high accuracy, and the processing accuracy of the object to be polished can be controlled with high accuracy. It becomes possible.
[0029]
The abrasive for magnetic polishing of the present invention has a density of 5 g / cm for the abrasive for magnetic polishing. Three As described above, when a processing stress is applied to the object to be polished, destruction of the polishing abrasive grains itself can be effectively prevented, and the polishing amount of the object to be polished can be further increased.
[0030]
Furthermore, the abrasive for magnetic polishing of the present invention suppresses the destruction of the abrasive for magnetic polishing itself when a processing stress is applied to the workpiece because the compressive strength of the abrasive for magnetic polishing is 50 MPa or more. Therefore, the polishing amount of the object to be polished can be increased.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
The abrasive grain for magnetic polishing of the present invention is composed of composite particles of particles mainly composed of soft magnetic ferrite (soft magnetic ferrite component) and particles mainly composed of abrasive (abrasive component).
[0032]
In the abrasive grains for magnetic polishing comprising the soft magnetic ferrite component and the abrasive component, each component is added and mixed to form particles, and the soft magnetic ferrite component is magnetized when a magnetic field is applied. Is defined as something that is easy to be done.
[0033]
The soft magnetic ferrite component functions as a ferromagnetic material, and is preferably a soft magnetic ferrite component containing Fe, Zn, Ni, Cu, Mn, or the like. It is particularly preferable to use a soft magnetic ferrite component containing 50 mol% or more of Fe in order to reduce the production cost and increase the magnetic sensitivity of the abrasive grains for magnetic polishing.
[0034]
A more preferable composition range is Fe in the case of a Mn-based soft magnetic ferrite component. Two O Three 40 to 95 mol%, ZnO 1 to 30 mol%, MnO 1 to 30 mol%, CuO 10 mol% or less. Two O Three , 40 to 95 mol%, ZnO 1 to 30 mol%, NiO 1 to 30 mol%, and CuO 10 mol% or less.
[0035]
The soft magnetism of soft magnetic ferrite is defined as a material that is easily magnetized when a magnetic field is applied.
[0036]
Further, as the abrasive component, various oxide ceramics, non-oxide ceramics or diamond can be used, and more preferably, particles of oxide ceramics, specifically, Al Two O Three , ZrO Two , SiO Two , Cr Two O Three , CeO Two And a mixture of one or more of these.
[0037]
The magnetic polishing abrasive grain of the present invention may contain a non-magnetic component in addition to the abrasive component and the soft magnetic ferrite component. For example, CaO, K Two O, MgO, CoO, Ta Two O Five , Nb Two O Five , WO Three , PbO, etc., in a total amount of 20% by weight or less.
[0038]
The abrasive for magnetic polishing of the present invention has a thin grain boundary layer in which each component is dissolved in the interface between the soft magnetic ferrite component and the abrasive component. The particles as the main component can be firmly bonded, and as a result, abrasive grains for magnetic polishing having particularly high mechanical strength can be provided.
[0039]
The abrasive for magnetic polishing according to the present invention contains the soft magnetic ferrite component in a proportion of 15 to 85% by weight and the abrasive component in a proportion of 15 to 85% by weight. Is important to be 0.5 to 20 μm.
[0040]
Thereby, the number of soft magnetic ferrite particles contained in the magnetic polishing abrasive grains can be increased, and the bonding force between the abrasive and the soft magnetic ferrite can be increased, thereby improving the strength of the magnetic polishing abrasive grains. In addition, the polishing amount in the surface processing of the object to be polished can be increased.
[0041]
When the soft magnetic ferrite component is less than 15% by weight and when the abrasive component exceeds 85% by weight, the magnetic attraction force of the abrasive grains for magnetic polishing is reduced, and the processing pressure on the object to be polished is reduced. As a result, the polishing amount of the object to be polished is reduced. On the other hand, when the soft magnetic ferrite component exceeds 85% by weight and when the abrasive component is less than 15% by weight, the polishing component is reduced, and the bonding force between the soft magnetic ferrite of the abrasive grains for magnetic polishing and the abrasive component is reduced. As a result, the strength of the abrasive grains for magnetic polishing decreases, and the polishing amount of the object to be polished decreases.
[0042]
The average particle size of the soft magnetic ferrite component is specified to be 0.5 to 20 μm. As a result, the bonding force of the soft magnetic ferrite component to the abrasive is increased, the strength of the magnetic abrasive grains is improved, the abrasive grains are less likely to break during polishing, and the amount of the object to be polished is increased.
[0043]
When the average particle size of the soft magnetic ferrite component is less than 0.5 μm, the magnetic property of the soft magnetic ferrite component is reduced, and the polishing amount of the object to be polished is reduced. This is because the bonding force between the ferrite component and the abrasive component is reduced, so that the amount of polishing of the object to be polished is reduced. This is considered to be because when the bonding force decreases, the mechanical strength of the magnetic polishing abrasive grain decreases, and the magnetic polishing abrasive grain is easily broken by the polishing pressure applied to the magnetic polishing abrasive grain during polishing. . In order to further improve the mechanical strength of the magnetic polishing abrasive grains by increasing the bonding force, the average thickness of the grain boundary layer is preferably 3 μm or less. The soft magnetic ferrite component is obtained by setting the mole% of CuO to 5 to 10 mole%.
[0044]
The abrasive for magnetic polishing of the present invention has a ratio of the average particle diameter of the soft magnetic ferrite component to the average particle of the abrasive for magnetic polishing of 10%. -Five -10 -1 It is important that
[0045]
Thereby, since the number of soft magnetic particles contained in the magnetic polishing abrasive grains can be increased, and the bonding force between the abrasive and the soft magnetic ferrite can be increased, the strength of the magnetic polishing abrasive grains can be improved, The polishing amount in the surface processing of the object to be polished can be increased.
The ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the magnetic polishing abrasive grains is 10 -Five If it is less than 10%, the magnetic properties of the soft magnetic ferrite component are reduced, so that the polishing amount of the object to be polished is reduced. -1 If it is larger than this, the amount of polishing of the object to be polished will decrease due to the decrease in the bonding force.
[0046]
The average particle diameter of the soft magnetic ferrite is determined by taking a photograph of the abrasive grains for magnetic polishing using a SEM, a stereoscopic microscope, a magnifying glass, or the like, and observing the soft abrasive particles in each of the 20 or more magnetic abrasive grains. A value obtained by randomly selecting 20 or more magnetic ferrite particles and further averaging the average value of the diameters of the inscribed circle and the circumscribed circle of each of the selected soft magnetic particles. However, soft magnetic ferrites having an average particle size of 0.2 μm or less are excluded from the average particle size of the soft magnetic ferrite particles because the particle size measurement is difficult.
[0047]
The ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the magnetic polishing abrasive grains is obtained by dividing the average particle diameter of the soft magnetic ferrite by the average particle diameter of the magnetic polishing abrasive grains, The average particle diameter of the magnetic polishing abrasive grains is determined by taking a photograph of the magnetic polishing abrasive grains with an SEM, a stereoscopic microscope, a magnifying glass, or the like, and selecting an inscribed circle in contact with each of the 10 randomly selected magnetic polishing abrasive grains. The average value of the diameters of the circumscribed circles is further averaged. However, abrasive grains for magnetic polishing having an average particle diameter of 0.2 μm or less are excluded from the subject of the average particle diameter of the abrasive grains for magnetic polishing because the particle diameter measurement is difficult.
[0048]
Further, the magnetic polishing abrasive grains of the present invention preferably have an average particle diameter of the magnetic polishing abrasive grains of 50 to 5000 μm, and can increase the polishing amount in the surface processing of the object to be polished. When the average particle diameter of the abrasive grains for magnetic polishing is less than 50 μm, the polishing amount of the object to be polished decreases. On the other hand, when the average particle diameter exceeds 5000 μm, the surface roughness of the polished surface is reduced while maintaining high polishing accuracy. I can't.
[0049]
Further, the abrasive grains for magnetic polishing of the present invention have an average particle diameter of 50 to 5000 μm, an average length in the short axis direction of 50 to 1000 μm, and an average length in the long axis direction of 75 to 5000 μm. preferable. This is because the polishing amount of the object to be polished can be particularly increased, and the polishing accuracy can be particularly improved.
[0050]
Further, the magnetic polishing abrasive grains of the present invention preferably have an aspect ratio of 1.5 or more. For example, as shown in an enlarged perspective view of an aggregate of the magnetic polishing abrasive grains of the present invention shown in FIG. The long axis surface of the magnetic polishing abrasive grains adheres in the direction of the rotating core while maintaining the adhesive force of the magnetic polishing abrasive grains to the rotating magnetic core while the shape of each particle of the polishing abrasive grains 1 is columnar. Therefore, the contact area of the magnetic polishing abrasive grains with the object to be polished can be increased, and the amount of polishing of the object to be polished per unit time can be increased. Further, since the processing stress applied per unit area of the object to be polished is reduced, it is possible to obtain an object to be polished having excellent surface roughness of the polished surface and high polishing accuracy.
[0051]
In the magnetic field during polishing, the magnetic flux tends to concentrate on the end of the abrasive grains for magnetic polishing. Therefore, when the aspect ratio is less than 1.5, the contact between the rotating core of the abrasive grains for magnetic polishing and the workpiece is long. It is difficult to align in the axial direction and comes into random contact in the major axis and minor axis directions. As a result, the surface roughness of the polished surface cannot be improved, and the polishing amount is not significantly improved.
[0052]
The aspect ratio is more preferably 20 or less, and the polishing amount of the object to be polished can be further increased, and the polishing accuracy can be particularly improved. This is because, if the aspect ratio is too large, particles having a certain average particle diameter have a shape close to a thread, and the strength is reduced, so that the polishing amount cannot be significantly improved.
[0053]
In addition, the above aspect ratio means that the length of the major axis direction and the minor axis direction of each magnetic polishing abrasive grain taken out by taking a photograph of the magnetic polishing abrasive grain with an SEM, a stereoscopic microscope, a magnifying glass, or the like, and arbitrarily taking out 10 magnetic abrasive grains. Is the average of these values.
[0054]
Here, as a method for producing abrasive grains for magnetic polishing having an aspect ratio of 1.5 or more, for example, soft magnetic ferrite particles, abrasive particles, and an organic binder are mixed and kneaded to form a compound, and a rod-shaped or square rod is used. Extrusion molding is performed, cut by a chopper, and then fired in an oxidizing atmosphere.
[0055]
Also, the magnetic polishing abrasive grains of the present invention preferably have a saturation magnetic flux density of 0.01 Tesla or more, and further increase the polishing amount by increasing the processing power of the magnetic polishing abrasive grains on the object to be polished. be able to. Note that the saturation magnetic flux density can be obtained with an oscillating magnetometer.
[0056]
Further, the abrasive for magnetic polishing of the present invention has a density of 5 g / cm. Three It is preferable that the polishing abrasive grains themselves are effectively prevented from being destroyed when a processing stress is applied to the object to be polished, and the polishing amount of the object to be polished can be further increased. In addition, the said density is measured by the particle density measuring method based on JISR1620 (1995).
[0057]
Further, the abrasive grains for magnetic polishing of the present invention preferably have a compressive strength of 50 MPa or more, and when a processing stress is applied to the object to be polished, the abrasive grains themselves are prevented from being destroyed, and the polishing object is polished. The amount can be increased. The compressive strength is measured using, for example, a micro compression tester (manufactured by Shimadzu).
[0058]
As described above, the magnetic flux abrasive grains have a saturation magnetic flux density of at least 0.01 Tesla and a density of 5 g / cm. Three The above and the compression strength of 50 MPa or more can be achieved by controlling the calcination temperature, the calcination temperature, and the calcination time, as described in detail in a manufacturing method described later.
[0059]
The method for producing the abrasive grains for magnetic polishing of the present invention is, for example, as follows.
[0060]
A composite particle containing 15 to 85% by weight of soft magnetic ferrite particles and 15 to 85% by weight of abrasive particles is prepared. Soft magnetic ferrite particles are made of oxides of Fe, Zn, Ni, Cu and Mn, or metal salts such as carbonates and nitrates that generate these oxides by firing. In the case of MnZn soft magnetic ferrite, Fe Two O Three 40 to 95 mol%, ZnO 1 to 30 mol%, MnO 1 to 30 mol%, CuO 10 mol% or less. In the case of NiZn soft magnetic ferrite, Two O Three Of 40 to 95 mol%, 1 to 30 mol% of ZnO, 1 to 30 mol% of NiO, and 10 mol% or less of CuO. As the composition of the abrasive particles, oxides such as Al and Zr, for example, Al Two O Three , ZrO Two , SiO Two , Cr Two O Three , CeO Two Alternatively, the composition contains one or more metal salts such as carbonates and nitrates that generate these oxides by firing. 20 to 80% by weight of the soft magnetic particles and 20 to 80% by weight of the abrasive particles are mixed, pulverized by a vibration mill or the like, calcined, added with an organic binder, kneaded with a kneader to form a compound, and extruded into a rod shape. At the same time, raw material granules adjusted to a desired aspect ratio by cutting with a chopper are obtained, and then fired.
[0061]
As a molding method, pressure molding, injection molding, an atomizing method, a stretching quenching method, a roll method, or the like can be used. For example, in the case of pressure molding, a binder may be added to the raw material obtained by calcining, granulation may be performed by various granulators, and the raw material may be filled in a mold having a predetermined aspect ratio and subjected to pressure molding. . In the case of injection molding, a plastic binder is added to the raw material obtained by calcining to form a slurry, and the slurry is injected into a mold designed to have a predetermined aspect ratio, and is thermally cured to obtain a desired aspect ratio. Can be obtained.
[0062]
The individual particles of the abrasive grains for magnetic polishing obtained by such a manufacturing method are obtained by firmly sintering the soft magnetic ferrite component and the abrasive component.
[0063]
In the above-mentioned manufacturing method, in order to make the average particle diameter of the soft magnetic ferrite component of the abrasive grains for magnetic polishing 0.5 to 20 μm, selection of the primary raw material, control of the calcination conditions, and control of the pulverization conditions after calcination. Is particularly important.
[0064]
Regarding the primary material of soft magnetic ferrite, the average particle size of the soft magnetic ferrite component is set to 0.5 to 20 μm even when crystal grains grow in the calcination and firing stages by setting the average particle size to 10 μm or less. can do.
[0065]
Then, the ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the abrasive grains for magnetic polishing is set to 10 -Five -10 -1 In order to obtain the powder as the abrasive for magnetic polishing by granulating the soft magnetic ferrite component and the abrasive component, the condition is adjusted by changing the conditions of a dry granulator or the like.
[0066]
Regarding the calcination conditions, it is important that the calcination is performed in the air atmosphere at a temperature of 750 to 900 ° C. for 1 to 10 hours. This is because the ferrite does not completely turn into ferrite, so that the magnetic properties are deteriorated. If the temperature is maintained at a temperature exceeding 900 ° C. for more than 10 hours, the ferrite components are partially evaporated to deteriorate the magnetic properties. Further, in order to make the average particle diameter of the soft magnetic ferrite component at least 0.5 μm, it is necessary to perform sufficient pulverization in pulverization after calcination. Sufficient pulverization is performed, for example, in a wet ball mill or bead mill by using ZrO. Two It becomes possible by crushing using a ball.
[0067]
In addition, selection of the above-mentioned primary raw materials, control of calcination conditions, and control of pulverization conditions after calcination are performed by a method for producing magnetic polishing abrasive grains containing MnZn-based soft magnetic ferrite and NiZn-based soft magnetic ferrite. Therefore, it is possible to manufacture magnetic polishing abrasive grains for obtaining a polished object having a particularly large polishing amount and a particularly small surface roughness.
[0068]
Further, in order to make the final aspect ratio of the abrasive grains for magnetic polishing 1.5 or more, when adjusting by extrusion molding, it is necessary to control the cut length after extrusion. For example, when obtaining 1000 μm square abrasive grains, it is necessary to set the extrusion speed to 1000 μm / s and the cutting time to 1.5 seconds / time or more.
[0069]
Further, the obtained magnetic abrasive grains have a saturation magnetic flux density of 0.01 Tesla or more and a density of 5 g / cm. Three As described above, since the sintering must be promoted in order to make the compressive strength 50 MPa or more, it is calcined for 1 to 10 hours in the range of 750 to 900 ° C. in the air atmosphere. It is necessary to bake in the range for 10 to 20 hours. If the sintering temperature is lower than 1000 ° C., sufficient compression strength cannot be obtained because sintering is not sufficiently promoted, and if it exceeds 1100 ° C., a large amount of soft magnetic ferrite components evaporate, and both the density and the compressive strength decrease. is there.
[0070]
The abrasive component is not restricted to be added after the calcination, and even if it is added to the soft magnetic ferrite component before the calcination, it does not affect the characteristics of the abrasive for magnetic polishing of the present invention.
[0071]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. FIG. 1 shows magnetic polishing abrasive grains having a columnar shape, but using magnetic abrasive grains having an aspect ratio of 1.5 or more in various shapes such as an elliptical shape, a rectangular parallelepiped shape, and a needle shape. Even in this case, similarly, a large amount of polishing can be performed and processing with excellent surface roughness can be performed.
[0072]
【Example】
(Example 1)
Fe Two O Three , ZnO, NiO, CuO and MnO were mixed in a vibration mill, and then calcined at 600 to 1000 ° C. to obtain a calcined body. This calcined body was added with Al as an abrasive component. Two O Three Was changed as shown in Table 1, and after pulverizing with a ball mill, a binder was added, and a granule having an arbitrary shape and size was obtained using a spray drier. Then, the granules were fired at 950 to 1400 ° C. in an air atmosphere to obtain a sample No. 1-14 were obtained.
[0073]
Each of the samples described above was used in an apparatus in which a magnetic pole was attached to a milling machine and rotated, and magnetic polishing was performed under the following conditions.
[0074]
Rotating magnetic pole: diameter 20 mm Radius of curvature of tip of rotating magnetic pole: 10 mm
Number of rotation of rotating magnetic pole: 2000 rpm Polishing object: S55C steel Abrasive grains: 2.5 g
Magnetic flux density T: 1.0 Tesla Gap between magnetic pole and workpiece to be polished: 1.4 mm
Polishing time: 15 minutes Surface roughness before polishing Ry: 2 μm
Table 1 shows the measured values of the polishing amount obtained for each abrasive grain together with the weight% of the soft magnetic ferrite component and the average particle diameter of the soft magnetic ferrite.
[0075]
From the results shown in Table 1, the average particle diameter of the soft magnetic ferrite component was 0.5 to 20 μm. When 2 to 6 were used, the polishing amount was as much as 180 mg or more, and excellent polishing characteristics were obtained.
[0076]
On the other hand, Sample No. 1 in which the average particle diameter of the soft magnetic ferrite component was less than 0.5 μm or more than 20 μm. When 1, 7, and 8 were used, the polishing amount was as small as 160 mg or less.
[0077]
Further, in the case of Sample No. where the weight percentage of the soft magnetic ferrite component was 15 to 85% by weight. When 11 to 14 were used, the polishing amount was as large as 180 mg or more, and excellent polishing characteristics were obtained.
[0078]
On the other hand, the sample No. in which the weight% of the soft magnetic ferrite component is less than 15% and more than 85% by weight. When 9 and 10 were used, the polishing amount was as low as 170 mg or less.
[0079]
[Table 1]
[0080]
(Example 2)
Next, the average particle size of the soft magnetic ferrite component was variously changed in the same manner as in Example 1, and the ratio of the average particle size of the magnetic polishing abrasive grains to the average particle size of the soft magnetic ferrite component was 10%. -Five -10 -1 A magnetic abrasive grain was prepared.
[0081]
Magnetic polishing was performed under the same conditions as in Example 1.
[0082]
Table 2 shows the measured values of the polishing amount when each abrasive grain was used by changing variously the weight percentage of the soft magnetic ferrite component and the ratio of the average particle size of the soft magnetic ferrite component to the average particle size of the abrasive grains for magnetic polishing. Indicated.
[0083]
The ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the magnetic polishing abrasive grains is 10 -Five -10 -1 In the case of using Sample Nos. 16 to 20, the polishing amount was as large as 190 mg or more, and excellent polishing characteristics were obtained.
[0084]
On the other hand, the ratio of the average particle diameter of the abrasive grains for magnetic polishing to the average particle diameter of the soft magnetic ferrite component is 10%. -Five Less than 10 -1 Sample no. When 15, 21, and 22 were used, the polishing amount was as small as 155 mg or less.
Further, in the case of Sample No. where the weight percentage of the soft magnetic ferrite component was 15 to 85% by weight. When 25 to 28 were used, the polishing amount was as large as 190 mg or more, and excellent polishing characteristics were obtained.
[0085]
On the other hand, the sample No. in which the weight% of the soft magnetic ferrite component is less than 15% and more than 85% by weight. When 23 and 24 were used, the polishing amount was as low as 170 mg or less.
[0086]
[Table 2]
[0087]
(Example 3)
Next, abrasive grains for magnetic polishing were prepared with an average particle size of the soft magnetic ferrite component of 0.5 to 20 μm and an average particle size of 10 to 6000 μm.
[0088]
The magnetic polishing was performed under the same conditions as in Example 1. The content of the abrasive component was 50% by weight based on the soft magnetic ferrite component.
[0089]
The measured values of the polishing amount and the surface roughness obtained for each abrasive grain are shown in Table 3 together with the average particle diameter of the magnetic abrasive grains.
[0090]
In addition, the measurement of surface roughness measured the arithmetic average roughness (Ra) based on JISB0601 with a stylus type surface roughness meter.
[0091]
From the results shown in Table 3, when using the sample Nos. 30 to 34 as abrasives for magnetic polishing with an average particle diameter of 50 to 5000 μm, the polishing amount was as large as 210 mg or more and the surface roughness Ra was 0. The polishing accuracy was excellent at 0.2 μm or less.
[0092]
In addition, Sample No. in which the average particle diameter of the magnetic polishing abrasive grains was less than 50 μm. When 29 was used, the polishing amount was as small as 200 mg or less.
[0093]
On the other hand, Sample No. 1 in which the average particle size of the magnetic polishing abrasive grains exceeded 5000 μm. In the case where 35 was used, the polishing accuracy could not be remarkably improved when the surface roughness Ra was 0.2 μm or more.
[0094]
[Table 3]
[0095]
(Example 4)
First, Fe Two O Three , ZnO, NiO, CuO and MnO were mixed in a vibration mill, and then calcined at 750 to 900 ° C. for 1 to 10 hours to obtain a calcined body. This calcined body is made of Al as an abrasive component. Two O Three Was added and mixed by a ball mill, kneaded with a kneader to form a compound, and a granule having a desired aspect ratio was obtained using an extruder.
[0096]
The average particle diameter of the abrasive grains for magnetic polishing was about 1000 μm, the average particle diameter of the soft magnetic ferrite component was 10 μm, and the ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the abrasive grains for magnetic polishing was 10 μm. -2 And
[0097]
The granules were fired at 1000 to 1100 ° C. in an air atmosphere to obtain sample Nos. Shown in Table 4. Magnetic abrasive grains comprising soft magnetic ferrite of 36 to 40 and an abrasive component were obtained.
[0098]
The aspect ratio of each of the obtained samples was obtained by taking a photograph with a SEM, arbitrarily taking out 10 particles, and calculating the ratio of the length in the major axis direction to the length in the minor axis direction of each magnetic polishing abrasive grain. The average of these was calculated.
[0099]
As is clear from Table 4, when the sample (No. 38 to 40) in which the aspect ratio of the magnetic polishing abrasive grains is 1.5 or more is used, the polishing amount is as large as 220 mg or more, and the polishing object after polishing is high. The surface roughness (Ra) was particularly smooth at 0.10 μm or less.
[0100]
On the other hand, when the samples (Nos. 36 and 37) having an aspect ratio of the magnetic polishing abrasive grains smaller than 1.5 were used, the polishing amount was 200 mg or less, and the polishing amount could not be increased significantly. The surface roughness (Ra) of the object to be polished after polishing was 0.15 μm or more, and a remarkably smooth surface could not be obtained.
[0101]
[Table 4]
[0102]
(Example 5)
Next, abrasive samples for magnetic polishing having various saturation magnetic flux densities were produced in the same manner as in Example 1.
[0103]
The polishing conditions were the same as in Example 1, and the polishing material component was Al. Two O Three And the content thereof was adjusted to 50% by weight with respect to the soft magnetic ferrite component. 41 to 44 were produced.
[0104]
The average particle diameter of the abrasive grains for magnetic polishing was about 1000 μm, the average particle diameter of the soft magnetic ferrite component was 10 μm, and the ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the abrasive grains for magnetic polishing was 10 μm. -2 The aspect ratio of each sample was 1.7, and the saturation magnetic flux density was determined using a vibrating magnetometer.
[0105]
Then, each sample was polished under the same conditions as in Example 1, and the polishing amount of each polished object was measured.
[0106]
Table 5 shows the results.
[0107]
As is clear from Table 5, the samples having a saturation magnetic flux density of 0.01 Tesla or more (Nos. 42 to 44) have a large polishing amount of 230 mg and are compared with the sample having a small saturation magnetic flux density (No. 41). It was found that the polishing amount was increased by 20 mg or more.
[0108]
[Table 5]
[0109]
(Example 6)
Next, abrasive grains for magnetic polishing having various densities and compressive strengths were prepared in the same manner as in Example 1.
[0110]
Magnetic polishing was performed under the same conditions as in Example 1. Al as an abrasive component Two O Three Was used to prepare a sample whose content was 50% by weight based on the soft magnetic ferrite component.
[0111]
The average particle diameter of the abrasive grains for magnetic polishing was about 1000 μm, the average particle diameter of the soft magnetic ferrite component was 10 μm, and the ratio of the average particle diameter of the soft magnetic ferrite component to the average particle diameter of the abrasive grains for magnetic polishing was 10 μm. -2 The aspect ratio of each sample was 1.7 and the saturation magnetic flux density was 0.1 Tesla. I asked.
[0112]
Table 6 shows measured values of the polishing amount of S55C steel polished under the same conditions as in Example 1 using each sample.
[0113]
From Table 6, the density of the abrasive is 5 g / cm. Three As described above, when the samples having compressive strengths of 50 MPa or more (Nos. 49, 50, 52, and 53) were used, the polishing amount was particularly large at 280 mg or more.
[0114]
On the other hand, the density is 4.5 g / cm Three When the sample (No. 45 to 48, 51) having a compressive strength of 10 MPa was used, the polishing amount was 240 to 260 mg.
[0115]
[Table 6]
[0116]
【The invention's effect】
According to the abrasive for magnetic polishing of the present invention, the abrasive contains 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of the abrasive component, and the soft magnetic ferrite component has an average particle diameter of 0.1%. When the thickness is 5 to 20 μm, the strength of the abrasive grains for magnetic polishing can be improved, and the polishing amount in the surface processing of the object to be polished can be improved.
[0117]
Further, according to the abrasive for magnetic polishing of the present invention, the abrasive contains 15 to 85% by weight of a soft magnetic ferrite component and 15 to 85% by weight of an abrasive component. The ratio of the average particle diameter of the magnetic polishing abrasive grains is 10 -Five -10 -1 By doing so, the strength of the abrasive grains for magnetic polishing can be improved, and the polishing amount in the surface processing of the object to be polished can be improved.
[0118]
Furthermore, according to the magnetic polishing abrasive grain of the present invention, the polishing amount per unit time can be further increased by controlling the average particle diameter of the magnetic polishing abrasive grain to 50 to 5000 μm, and the polishing target Since the processing stress applied per unit area of the object is reduced, the surface roughness of the object to be polished is reduced while maintaining the adhesion of the abrasive grains to the rotating core, and furthermore, the polishing with the excellent surface roughness of the polished surface An object to be polished with high accuracy can be obtained.
[0119]
Further, according to the magnetic polishing abrasive grains of the present invention, since the aspect ratio of the soft magnetic ferrite particles is 1.5 or more, the contact form of the magnetic polishing abrasive grains to the object to be polished is in the long axis direction. It is easy to align, the polishing area per unit time is increased by increasing the contact area to the object to be polished, the processing stress applied per unit area is reduced, and the adhesion of the abrasive grains to the rotating magnetic core is maintained. In addition, the object to be polished can have excellent surface roughness and high polishing accuracy.
[0120]
Furthermore, according to the abrasive for magnetic polishing of the present invention, since the saturation magnetic flux density of the abrasive is set to 0.01 Tesla or more, the magnetic force applied to the abrasive increases, the processing pressure increases, and the The polishing amount can be further increased, and the magnetic force of the magnetic polishing abrasive grains is large, so that the polishing amount can be controlled with high accuracy, and the processing accuracy of the object to be polished can be controlled with high accuracy. .
[0121]
Furthermore, according to the abrasive grains for magnetic polishing of the present invention, the density is 5 g / cm. Three As described above, when processing stress is applied to the object to be polished, destruction of the polishing abrasive grains itself can be effectively prevented, and the amount of polishing of the object to be polished can be further increased.
[0122]
Further, since the abrasive for magnetic polishing of the present invention has a compressive strength of 50 MPa or more, when a processing stress is applied to the object to be polished, it is possible to suppress the destruction of the abrasive grains themselves, The polishing amount of the object can be increased.
[Brief description of the drawings]
FIG. 1 is an enlarged perspective view showing an embodiment of a magnetic polishing abrasive grain of the present invention.
[Explanation of symbols]
1: Abrasive grains for magnetic polishing
2: Object to be polished
