JP3737830B2

JP3737830B2 - Corrosion-resistant permanent magnet and method for manufacturing the same

Info

Publication number: JP3737830B2
Application number: JP16628693A
Authority: JP
Inventors: 雅子鈴木; 文秋菊井
Original assignee: Neomax Co Ltd
Current assignee: Hitachi Metals Ltd
Priority date: 1993-06-11
Filing date: 1993-06-11
Publication date: 2006-01-25
Anticipated expiration: 2021-01-25
Also published as: JPH06349619A

Description

【0001】
【産業上の利用分野】
この発明は、高磁気特性を有しかつ密着性がすぐれ、耐食性、耐酸、耐アルカリ性、耐摩耗性にすぐれた耐食性被膜を設けたFe-B-Ra系永久磁石に係り、耐食性、特に80℃、相対湿度90%の雰囲気に長時間放置した場合の初期磁石特性からの劣化が少なく、きわめて安定した磁石特性を有する耐食性永久磁石およびその製造方法に関する。
【0002】
【従来の技術】
先に、NdやPrを中心とする資源的に豊富な軽希土類を用いてB,Feを主成分とし、高価なSmやCoを含有せず、従来の希土類コバルト磁石の最高特性を大幅に超える新しい高性能永久磁石として、Fe-B-Ra系永久磁石が提案されている(特開昭59-46008号公報、特開昭59-89401号公報)。
【0003】
前記磁石合金のキュリー点は、一般に300℃〜370℃であるが、Feの一部をCoにて置換することにより、より高いキュリー点を有するFe-B-Ra系永久磁石(特開昭59-64733号、特開昭59-132104号)を得ており、さらに、前記Co含有のFe-B-Ra系希土類永久磁石と同等以上のキュリー点並びにより高い(BH)maxを有し、その温度特性、特にiHcを向上させるため、希土類元素(Ra)としてNdやPr等の軽希土類を中心としたCo含有のFe-B-Ra系希土類永久磁石のRaの一部にDy、Tb等の重希土類のうち少なくとも1種を含有することにより、25MGOe以上の極めて高い(BH)maxを保有したままで、iHcをさらに向上させたCo含有のFe-B-Ra系希土類永久磁石が提案(特開昭60-34005号)されている。
【0004】
しかしながら、上記のすぐれた磁気特性を有するFe-B-Ra系磁気異方性焼結体からなる永久磁石は主成分として、空気中で酸化し易い希土類元素及び鉄を含有するため、磁気回路に組込んだ場合に、磁石表面に生成する酸化物により、磁気回路の出力低下及び磁気回路間のばらつきを惹起し、また、表面酸化物の脱落による周辺機器への汚染の問題があった。
【0005】
【発明が解決しようとする課題】
そこで、上記のFe-B-Ra系永久磁石の耐食性の改善のため、磁石体表面に無電解めっき法あるいは電解めっき法により耐食性金属めっき層を被覆した永久磁石(特願昭58ー162350号)が提案されているが、このめっき法では永久磁石体が焼結体で有孔性のため、この孔内にめっき前処理での酸性溶液またはアルカリ溶液が残留し、経年変化とともに腐食する恐れがあり、また磁石体の耐薬品性が劣るため、めっき時に磁石表面が腐食されて密着性、防蝕性が劣る問題があった。
また、耐食性めっきを設けても、温度60℃、相対湿度90%の条件下の耐食性試験で100時間放置にて、磁石特性は初期磁石特性の10%以上劣化し、非常に不安定であった。
【0006】
そのため、Fe-B-Ra系永久磁石の耐食性の改善向上のため、前記磁石表面にイオンプレーティング法、イオンスパッタリング法等により、TiN、Ti被膜を被着して耐食性の改善向上することが提案(特開昭61-150201号公報)されている。
しかし、TiN被膜はFe-B-Ra系磁石体と結晶構造の他熱膨張係数、延性等が相違するため密着性が悪く、またTi被膜は密着性、耐食性は良好であるが、耐摩耗性が低い等の欠点があり、そのためFe-B-Ra系永久磁石体表面にTiとTiNの積層被膜を被着することが提案(特開昭63-9919号)されている。
ところが、Ti被膜とTiN被膜は結晶構造、熱膨張係数及び延性等が異なるため、その密着性が悪く、剥離等を生じて、耐食性の低下を招来する問題があった。
【0007】
この発明は、Fe-B-Ra系永久磁石下地との密着性にすぐれ、耐摩耗性、耐食性の改善向上を目的に、特に温度80℃、相対湿度90%の雰囲気条件下で長時間放置した場合の初期磁石特性からの劣化を極力少なくし、安定した高磁石特性、耐摩耗性、耐食性を有するFe-B-Ra系永久磁石を安価に提供することを目的とする。
【0008】
【課題を解決するための手段】
この発明は、すぐれた耐食性、特に温度80℃、相対湿度90%の雰囲気条件下で長時間放置した場合においても、下地との密着性がすぐれ、被着した耐食性金属被膜の耐食性、耐摩耗性により、その磁石特性の安定したFe-B-Ra系永久磁石を目的に永久磁石体表面へのTiN被膜形成法について種々検討した結果、磁石体表面をイオンスパッター法等により清浄化した後、前記磁石体表面にイオンプレーティング法等の薄膜形成法により特定膜厚のTi被膜を形成後、特定条件のArガスとN₂ガスとの混合ガスを導入しながらイオンプレーティング等の薄膜形成法を行って、前記Ti被膜表面上に、特定層厚で外側表面に近づくにつれて窒素濃度が連続的に増加する組成 TiNx からなる層を形成後、N₂ガス中にてイオン反応プレーティング等の薄膜形成法を行って、特定膜厚のTiN被膜を形成することにより、Ti被膜とTiN被膜との密着性が著しく改善できることを知見し、この発明を完成した。
【0009】
すなわち、この発明は
主相が正方晶相からなるFe-B-Ra系永久磁石体表面に直接成膜された膜厚0.1μm〜3.0μmのTi被膜を有し、前記Ti被膜上に磁石体側より順次窒素濃度が連続的に増加する膜厚0.05μm〜2.0μmの組成TiNxからなる層を有し、該組成 TiNx からなる層上に膜厚 0.5 μ m 〜 10 μ m の TiN 被膜層が形成されたことを特徴とする耐食性永久磁石である。
また、この発明は
主相が正方晶相からなるFe-B-Ra系永久磁石体表面を洗浄化した後、ターゲットに Ti を用いたイオンプレーティング法により、200℃〜500℃に保持した前記磁石体面に膜厚0.1μm〜3.0μmのTi被膜を形成し、前記方法により処理容器内にArとN₂混合ガスをガス圧一定でN₂量を連続的に増加させながら導入して、前記Ti被膜上に膜内の窒素濃度が連続的に増加する膜厚0.05μ m〜2.0μmの組成TiNxからなる層を形成し、前記方法により該処理容器内をガス圧一定の N ₂ ガス雰囲気にして前記組成 TiNx からなる層上に膜厚0.5μm〜10μmのTiN被膜層を形成することを特徴とする耐食性永久磁石の製造方法である。
【0010】
Fe-B-Ra系永久磁石体表面に設けたTi被膜の上に窒素濃度が連続的に増加する組成TiNxからなる層を介してTiN被膜層を設けたことを特徴とする耐食性永久磁石の製造方法の一例を以下に詳述する。
例えば、アークイオンプレーティング装置を用いて、真空容器を到達真空度1×10^-3Pa以下まで真空排気した後、Arガス圧10Pa、-500VでArイオンによる表面スパッターにてFe-B-Ra系磁石体表面を清浄化する。
次にArガス圧0.1Pa、バイアス電圧-80Vにより、ターゲットのTiを蒸発させて、アークイオンプレーティング法にて、磁石体表面に0.1μm〜3.0μm膜厚のTi被膜層を形成する。
続いて、Ti被膜層表面上に特定厚に組成TiNxからなる層を形成するため、Tiを蒸発させながら、基板の磁石温度を400℃に保持して、ガス圧1Pa、バイアス電圧-100V、アーク電流100A条件にて、Arガスと窒素混合ガスを導入後、混合ガス中のN₂量を増加させることにより、特定厚のかつTiN被膜層に向かって窒素濃度の増加する組成 TiNx からなる層を形成する。
その後、さらに窒素量ガスの圧力1Paでアークイオンプレーティングを行って、前記Ti被膜層上に設けた組成 TiNx からなる層上に特定厚のTiN被膜を形成することができる。
【0011】
この発明において、Fe-B-Ra系永久磁石体表面に被着のTi被膜層、組成 TiNx からなる層の形成方法としては、イオンプレーティング法や蒸着法など公知の薄膜形成法を適宜選定できるが、被膜の緻密性、均一性、膜形成速度等の理由から、イオンプレーティング法、イオン反応プレーティング法が好ましい。
反応被膜生成時の基板磁石の温度は200℃〜500℃に設定するのが好ましく、200℃未満では基板磁石との反応密着が十分でなく、また500℃を超えると常温(-25℃)との温度差が大きくなり、処理後の冷却過程で被膜に亀裂が入り、一部基板より剥離を発生するため、基板磁石の温度を200℃〜500℃に設定する。
【0012】
この発明において、磁石体表面のTi被膜厚を0.1μm〜3.0μmに限定した理由は、0.1μm未満では磁石表面との密着性が十分でなく、3.0μmを超えると効果的には問題ないが、下地膜としてはコスト上昇を招来して、実用的でなく好ましくないので、Ti被膜厚は0.1μm〜3.0μmとする。
また、前記Ti被膜層上に形成の組成 TiNx からなる層厚を0.05μm〜2.0μmに限定した理由は、0.05μm未満では組成 TiNx からなる層が十分でなく、良好な密着性が得られず、2.0μmを超えると効果上は問題ないが、製造コスト上昇を招来するので実用的でなく、好ましくない。
この発明において、Ti被膜層上の組成 TiNx からなる層は、さらに成膜するTiN被膜層に向かって窒素濃度が連続的に増加することが好ましい。
また、TiN被膜厚を0.5μm〜10μmに限定した理由は、0.5μm未満ではTiNとしての耐食性、耐摩耗性が十分でなく、10μmを超えると効果的には問題ないが、製造コスト上昇を招来するので好ましくない。
【0013】
この発明の永久磁石に用いる希土類元素Raは、組成の10原子%〜30原子%を占めるが、Nd、Pr、Dy、Ho、Tbのうち少なくとも1種、あるいはさらに、La、Ce、Sm、Gd、Er、Eu、Tm、Yb、Lu、Yのうち少なくとも1種を含むものが好ましい。
また、通常Raのうち1種をもって足りるが、実用上は2種以上の混合物(ミッシュメタル、ジジム等)を入手上の便宜等の理由により用いることができる。なお、このRaは純希土類元素でなくてもよく、工業上入手可能な範囲で製造上不可避な不純物を含有するものでも差支えない。
Raは、上記系永久磁石における必須元素であって、10原子%未満では結晶構造がα-鉄と同一構造の立方晶組織となるため、高磁気特性、特に高保磁力が得られず、30原子%を超えるとRaリッチな非磁性相が多くなり、残留磁束密度(Br)が低下してすぐれた特性の永久磁石が得られない。よって、Ra10原子%〜30原子%の範囲が望ましい。
【0014】
Bは、上記系永久磁石における必須元素であって、2原子%未満では菱面体構造が主相となり、高い保磁力(iHc)は得られず、28原子%を超えるとBリッチな非磁性相が多くなり、残留磁束密度(Br)が低下するため、すぐれた永久磁石が得られない。よって、Bは2原子%〜28原子%の範囲が望ましい。
【0015】
Feは、上記系永久磁石において必須元素であり、65原子%未満では残留磁束密度(Br)が低下し、80原子%を超えると高い保磁力が得られないので、Feは65原子%〜80原子%の含有が望ましい。
また、Feの一部をCoで置換することは、得られる磁石の磁気特性を損うことなく、温度特性を改善することができるが、Co置換量がFeの20%を超えると、逆に磁気特性が劣化するため、好ましくない。Coの置換量がFeとCoの合計量で5原子%〜15原子%の場合は、(Br)は置換しない場合に比較して増加するため、高磁束密度を得るために好ましい。
【0016】
また、Ra、B、Feの他、工業的生産上不可避的不純物の存在を許容でき、例えば、Bの一部を4.0wt%以下のC、2.0wt%以下のP、2.0wt%以下のS、2.0wt%以下のCuのうち少なくとも1種、合計量で2.0wt%以下で置換することにより、永久磁石の製造性改善、低価格化が可能である。
さらに、Al、Ti、V、Cr、Mn、Bi、Nb、Ta、Mo、W、Sb、Ge、Sn、Zr、Ni、Si、Zn、Hf、のうち少なくとも1種は、Fe-B-Ra系永久磁石材料に対してその保磁力、減磁曲線の角型性を改善あるいは製造性の改善、低価格化に効果があるため添加することができる。なお、添加量の上限は、磁石材料の(BH)maxを20MGOe以上とするには、(Br)が少なくとも9kG以上必要となるため、該条件を満す範囲が望ましい。
【0017】
また、この発明の永久磁石は平均結晶粒径が1〜80μmの範囲にある正方晶系の結晶構造を有する化合物を主相とし、体積比で1%〜50%の非磁性相(酸化物相を除く)を含むことを特徴とする。
この発明による永久磁石は、保磁力iHc≧1kOe、残留磁束密度Br>4kG、を示し、最大エネルギー積(BH)maxは、(BH)max≧10MGOeを示し、最大値は25MGOe以上に達する。
【0018】
【作用】
この発明は、Fe-B-Ra系永久磁石体表面をイオンスパッター法等により清浄化した後、前記磁石体表面にイオンプレーティング法等の薄膜形成法によりTi被膜を形成後、特定条件のArガスとN₂ガスとの混合ガスを導入しながらイオンプレーティング等の薄膜形成法を行って、前記Ti被膜表面に順次窒素濃度が増加する組成 TiNx からなる層を形成後、N₂ガス中にてイオン反応プレーティング等の薄膜形成法を行って、TiN被膜を形成したことを特徴とし、組成 TiNx からなる層を介在させてTi被膜上にTiN被膜を積層するため、両被膜の密着性が著しく改善され、すぐれた耐食性、特に温度80℃、相対湿度90%の雰囲気条件下で長時間放置した場合においても、下地との密着性がすぐれ、被着した耐食性金属被膜の耐食性、耐摩耗性により、その磁石特性の安定したFe-B-Ra系永久磁石が得られる。
【0019】
【実施例】
実施例1
公知の鋳造インゴットを粉砕し、微粉砕後に成形、焼結、熱処理後に、16Nd-77Fe-7B組成の径12mm×厚み2mm寸法の磁石体試験片を得た。その磁石特性を表1に示す。
真空容器内を1×10^-3Pa以下に真空排気し、Arガス圧10Pa、-500Vで20分間、表面スパッターを行って、磁石体表面を清浄化した後、Arガス圧0.1Pa、バイアス電圧-80V、アーク電流100A、基板磁石温度を400℃にて、ターゲットとして金属Tiをアークイオンプレーティング法にて、磁石体表面に0.1μm厚のTi被膜層を形成する。
次に基板磁石400℃、バイアス電圧-100V、アーク電流100Aで、Ar:N₂=9:1の混合ガス1Paを導入し、混合ガス比率をAr:N₂比率を9:1→7:3→5:5→3:7→0:10と連続的に混合ガス組成を変えて、30分でTi被膜表面に膜厚0.3μmの組成TiNxからなる層を形成した。
さらに、N2ガス1Pa、バイアス電圧-100V、アーク電流100Aでアークイオンプレーティングを行って、3時間で前記組成 TiNx からなる層上にTiN被膜を3μm形成した。
その後、放冷後、得られたTiN被膜を表面に有する永久磁石を温度80℃、相対湿度90%の条件下で1000時間放置した後の磁石特性及びその劣化状況を測定し、その結果を第2表に示す。
【0020】
比較例1
実施例1と同一組成の磁石体試験片を実施例1と同一条件にて表面清浄化した後、実施例1と同一条件にて1.0μm厚のTi被膜を形成後、Ti被膜上に実施例1と同一条件にてTiN被膜を3μm厚に形成した。
その後、実施例1と同一の温度80℃、相対湿度90%の条件下で1000時間放置後の磁石特性及びその劣化状況を測定し、その結果を第2表に示す。
【0021】
【表1】

【0022】
【表2】

【0023】
表2に示すように、同一磁石特性を有するFe-B-Ra系永久磁石体表面にTi被膜とTiN被膜層を設けた比較例磁石は、温度80℃、相対湿度90%の条件下で1000時間放置した耐食試験前後の磁石特性の劣化が大きくかつ発錆しているのに対して、Ti被膜の上に窒素濃度が連続的に増加する組成TiNxからなる層を介してTiN被膜層を設けたこの発明のFe-B-Ra系永久磁石は、錆は発生せず、磁石特性もほとんど変わらないことが明らかである。
【0024】
【発明の効果】
この発明による磁石表面に設けたTi被膜の上に窒素濃度が連続的に増加する組成TiNxからなる層を介してTiN被膜層を設けたFe-B-Ra系永久磁石体は、実施例の如く、苛酷な耐食試験条件、特に、温度80℃、相対湿度90%の条件下で、1000時間放置した後、その磁石特性の劣化はほとんどなく、現在、最も要求されている高性能かつ安価な永久磁石として極めて適している。[0001]
[Industrial application fields]
The present invention relates to a Fe-B-Ra permanent magnet provided with a corrosion-resistant film having high magnetic properties, excellent adhesion, and excellent corrosion resistance, acid resistance, alkali resistance, and wear resistance. The present invention relates to a corrosion-resistant permanent magnet that has little deterioration from the initial magnet characteristics when left in an atmosphere with a relative humidity of 90% for a long time and has extremely stable magnet characteristics, and a method for producing the same.
[0002]
[Prior art]
First, it uses B and Fe as the main components using light rare earths rich in resources such as Nd and Pr, does not contain expensive Sm and Co, and greatly exceeds the highest characteristics of conventional rare earth cobalt magnets. Fe-B-Ra permanent magnets have been proposed as new high performance permanent magnets (Japanese Patent Laid-Open Nos. 59-46008 and 59-89401).
[0003]
The Curie point of the magnet alloy is generally 300 ° C. to 370 ° C., but a Fe—B—Ra permanent magnet having a higher Curie point can be obtained by substituting part of Fe with Co (Japanese Patent Laid-Open No. Sho 59). No.-64733, JP-A-59-132104), and has a Curie point equal to or higher than that of the Co-containing Fe-B-Ra rare earth permanent magnet and a higher (BH) max. In order to improve temperature characteristics, especially iHc, as part of Ra of Co-containing Fe-B-Ra rare earth permanent magnets with light rare earth such as Nd and Pr as rare earth elements (Ra), such as Dy and Tb Proposed Co-containing Fe-B-Ra rare earth permanent magnets with a further improved iHc while retaining an extremely high (BH) max of 25 MGOe or more by containing at least one of the heavy rare earths. No. 60-34005).
0004
However, a permanent magnet made of an Fe-B-Ra magnetic anisotropic sintered body having excellent magnetic properties described above contains, as a main component, a rare earth element that easily oxidizes in air and iron. When incorporated, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and a variation between the magnetic circuits, and there is a problem of contamination of peripheral devices due to the drop of the surface oxide.
[0005]
[Problems to be solved by the invention]
Therefore, in order to improve the corrosion resistance of the above-mentioned Fe-B-Ra permanent magnets, permanent magnets whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Application No. 58-162350) However, in this plating method, since the permanent magnet body is a sintered body and porous, an acidic solution or an alkaline solution in the plating pretreatment remains in the hole and may corrode with aging. In addition, since the chemical resistance of the magnet body is inferior, the surface of the magnet is corroded during plating, resulting in poor adhesion and corrosion resistance.
Even with corrosion-resistant plating, the magnet characteristics deteriorated by more than 10% of the initial magnet characteristics and remained extremely unstable after standing for 100 hours in a corrosion resistance test under conditions of a temperature of 60 ° C and a relative humidity of 90%. .
[0006]
Therefore, in order to improve the corrosion resistance of Fe-B-Ra permanent magnets, it is proposed to improve the corrosion resistance by depositing TiN or Ti coating on the magnet surface by ion plating method, ion sputtering method, etc. (Japanese Patent Laid-Open No. 61-150201).
However, TiN coating has poor adhesion due to differences in thermal expansion coefficient, ductility, etc. in addition to crystal structure and Fe-B-Ra magnet body, and Ti coating has good adhesion and corrosion resistance, but wear resistance For this reason, it has been proposed that a multilayer coating of Ti and TiN be deposited on the surface of the Fe-B-Ra permanent magnet body (Japanese Patent Laid-Open No. 63-9919).
However, since the Ti coating and the TiN coating differ in crystal structure, thermal expansion coefficient, ductility, etc., there is a problem in that the adhesion is poor, peeling occurs and the corrosion resistance is lowered.
[0007]
The present invention has excellent adhesion to the base of the Fe-B-Ra permanent magnet, and is left to stand for a long time under atmospheric conditions of a temperature of 80 ° C. and a relative humidity of 90%, with the aim of improving and improving wear resistance and corrosion resistance. It is an object of the present invention to provide an Fe-B-Ra permanent magnet having stable high magnet characteristics, wear resistance, and corrosion resistance at low cost by minimizing deterioration from initial magnet characteristics.
[0008]
[Means for Solving the Problems]
This invention has excellent corrosion resistance, especially when it is left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%, and the adhesion to the substrate is excellent, and the corrosion resistance and wear resistance of the deposited corrosion-resistant metal film. As a result of various studies on the TiN film formation method on the surface of the permanent magnet body for the purpose of the Fe-B-Ra permanent magnet having stable magnet characteristics, the surface of the magnet body was cleaned by ion sputtering, etc. After forming a Ti film with a specific thickness on the surface of the magnet body by a thin film formation method such as ion plating, a thin film formation method such as ion plating is performed while introducing a mixed gas of Ar gas and N ₂ gas under specific conditions. On the surface of the Ti coating, after forming a layer made of a composition TiNx with a specific layer thickness and a nitrogen concentration that increases continuously as the outer surface is approached, thin film formation such as ion reaction plating is performed in N ₂ gas Go the law, special By forming a constant thickness of the TiN film, and found that adhesion between the Ti film and the TiN film it can be remarkably improved, and have completed the present invention.
[0009]
That is, the present invention has a Ti film with a film thickness of 0.1 μm to 3.0 μm formed directly on the surface of a Fe—B—Ra permanent magnet body whose main phase is a tetragonal phase , and the magnet body side is formed on the Ti film. more it has a layer comprising the composition TiNx film thickness 0.05μm~2.0μm sequentially nitrogen concentration increases continuously, TiN coating layer with a thickness of 0.5 μ m ~ 10 μ m in a layer on a made of the composition TiNx is formed It is the corrosion-resistant permanent magnet characterized by being made .
Further, in the present invention, after cleaning the surface of the Fe-B-Ra permanent magnet body whose main phase is a tetragonal phase, the temperature was maintained at 200 ° C. to 500 ° C. by ion plating using Ti as a target. A Ti film having a film thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body, and Ar and N ₂ mixed gas is introduced into the processing vessel by the above method while continuously increasing the amount of N _{2 at a} constant gas pressure. nitrogen concentration within the membrane on the Ti coating layer to form having a composition TiNx continuously increasing thickness 0.05 μ m ~2.0μm, the processing chamber and the gas pressure constant N ₂ gas atmosphere by the method And a TiN coating layer having a thickness of 0.5 μm to 10 μm is formed on the layer made of the composition TiNx .
[0010]
Fe-B-Ra-based corrosion-resistant permanent magnet, characterized in that the nitrogen concentration on the Ti coating film provided on the permanent magnet surface is via a layer of a composition TiNx you increase continuously provided a TiN coating film layer An example of the manufacturing method will be described in detail below.
For example, after evacuating the vacuum vessel to an ultimate vacuum of 1 × 10 ⁻³ Pa or less using an arc ion plating apparatus, Fe—B-Ra is formed by surface sputtering with Ar ions at an Ar gas pressure of 10 Pa and −500 V. Clean the surface of the magnet body.
Next, Ti of the target is evaporated at an Ar gas pressure of 0.1 Pa and a bias voltage of −80 V, and a Ti coating layer having a thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body by an arc ion plating method.
Subsequently, to form a layer having a composition TiNx the particular thickness on the Ti coating film layer surface, while evaporating Ti, and holds the magnet temperature of the substrate 400 ° C., gas pressure 1 Pa, the bias voltage -100 V, the arc at current 100A condition, after the introduction of Ar gas and nitrogen mixed gas, by increasing the N ₂ content in the mixed gas, a layer made of a composition TiNx of increasing nitrogen concentration towards a specific thickness and TiN coating layer Form.
Thereafter, arc ion plating is further performed at a nitrogen gas pressure of 1 Pa to form a TiN film having a specific thickness on the layer made of the composition TiNx provided on the Ti film layer.
[0011]
In the present invention, Ti coating layer deposited on Fe-B-Ra-based permanent magnet surface, as a method of forming the layer composed of the composition TiNx can be suitably selected ion plating method or a vapor deposition method such as a known thin film forming method However, the ion plating method and the ion reaction plating method are preferable because of the denseness, uniformity, and film formation speed of the coating film.
The temperature of the substrate magnet during reaction film formation is preferably set to 200 ° C to 500 ° C. If it is less than 200 ° C, the reaction adhesion with the substrate magnet is not sufficient, and if it exceeds 500 ° C, it will be at room temperature (-25 ° C). The temperature difference between the substrate magnets becomes large and cracks occur in the coating during the cooling process after the treatment, causing some peeling from the substrate. Therefore, the temperature of the substrate magnet is set to 200 ° C to 500 ° C.
[0012]
In the present invention, the reason why the Ti film thickness on the surface of the magnet body is limited to 0.1 μm to 3.0 μm is that the adhesion with the magnet surface is not sufficient if it is less than 0.1 μm, and if it exceeds 3.0 μm, there is no problem effectively. Since the base film causes an increase in cost and is not practical and not preferable, the Ti film thickness is set to 0.1 μm to 3.0 μm.
Also, the reason for limiting the layer thickness having a composition TiNx of forming on the Ti coating layer to 0.05μm~2.0μm is not sufficient layer having the composition TiNx is less than 0.05 .mu.m, no satisfactory adhesion is obtained If it exceeds 2.0 μm, there is no problem in effect, but it is not practical and preferable because it causes an increase in production cost.
In the present invention, it is preferable that the layer of the composition TiNx on the Ti coating layer has a nitrogen concentration continuously increasing toward the TiN coating layer to be further formed .
The reason for limiting the TiN film thickness to 0.5 μm to 10 μm is that if it is less than 0.5 μm, the corrosion resistance and wear resistance as TiN are not sufficient, and if it exceeds 10 μm, there is no problem effectively, but it causes an increase in manufacturing cost This is not preferable.
[0013]
The rare earth element Ra used in the permanent magnet of the present invention occupies 10 atomic% to 30 atomic% of the composition, but at least one of Nd, Pr, Dy, Ho, and Tb, or even La, Ce, Sm, Gd , Er, Eu, Tm, Yb, Lu, and Y are preferred.
In addition, one kind of Ra is usually sufficient, but in practice, a mixture of two or more kinds (Misch metal, zidim, etc.) can be used for reasons of convenience. The Ra does not have to be a pure rare earth element, and may contain impurities that are inevitable in production within a commercially available range.
Ra is an essential element in the above system permanent magnet, and if it is less than 10 atomic%, the crystal structure has the same cubic structure as α-iron, so high magnetic properties, particularly high coercive force cannot be obtained, and 30 atoms If it exceeds%, the Ra-rich nonmagnetic phase increases, and the residual magnetic flux density (Br) decreases, making it impossible to obtain a permanent magnet with excellent characteristics. Therefore, the range of Ra 10 atom% to 30 atom% is desirable.
[0014]
B is an essential element in the above system permanent magnets, and if it is less than 2 atomic%, the rhombohedral structure is the main phase, and high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic%, it is a B-rich nonmagnetic phase. And the residual magnetic flux density (Br) decreases, so that an excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atomic% to 28 atomic%.
[0015]
Fe is an essential element in the above system permanent magnet, and if it is less than 65 atomic%, the residual magnetic flux density (Br) decreases, and if it exceeds 80 atomic%, a high coercive force cannot be obtained. An atomic% content is desirable.
Substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet, but conversely, when the Co substitution amount exceeds 20% of Fe, Since magnetic characteristics deteriorate, it is not preferable. When the substitution amount of Co is 5 atom% to 15 atom% in terms of the total amount of Fe and Co, (Br) is increased as compared with the case where no substitution is made, and thus it is preferable for obtaining a high magnetic flux density.
0016
In addition to Ra, B, and Fe, the presence of inevitable impurities in industrial production can be allowed.For example, a part of B is 4.0 wt% or less C, 2.0 wt% or less P, 2.0 wt% or less S. By replacing at least one of 2.0 wt% or less of Cu with a total amount of 2.0 wt% or less, it is possible to improve the manufacturability of permanent magnets and reduce the price.
Furthermore, at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, and Hf is Fe-B-Ra. It can be added to the permanent magnet material because it has the effect of improving the coercive force and the squareness of the demagnetization curve, improving the manufacturability, and reducing the price. It should be noted that the upper limit of the amount of addition is preferably in a range that satisfies this condition because (Br) needs to be at least 9 kG or more in order to make (BH) max of the magnetic material 20 MGOe or more.
[0017]
Further, the permanent magnet of the present invention comprises a compound having a tetragonal crystal structure with an average crystal grain size in the range of 1 to 80 μm as a main phase, and a nonmagnetic phase (oxide phase) having a volume ratio of 1% to 50%. Is included).
The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe and a residual magnetic flux density Br> 4 kG, the maximum energy product (BH) max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.
[0018]
[Action]
In the present invention, the surface of the Fe-B-Ra permanent magnet body is cleaned by an ion sputtering method or the like, and then a Ti film is formed on the surface of the magnet body by a thin film forming method such as an ion plating method. Perform a thin film formation method such as ion plating while introducing a mixed gas of gas and N ₂ gas, and after forming a layer of composition TiNx with increasing nitrogen concentration on the Ti coating surface, in N ₂ gas It is characterized by forming a TiN film by performing a thin film formation method such as ion reaction plating, and because the TiN film is laminated on the Ti film with a layer made of composition TiNx interposed, the adhesion of both films is Significantly improved and excellent corrosion resistance, especially when it is left for a long period of time at an ambient temperature of 80 ° C and relative humidity of 90%, it has excellent adhesion to the substrate and the corrosion resistance and wear resistance of the deposited metal film. Stabilizes its magnet characteristics Fe-B-Ra permanent magnets can be obtained.
[0019]
【Example】
Example 1
A known cast ingot was pulverized, and after fine pulverization, molding, sintering, and heat treatment, a magnet body test piece having a diameter of 12 mm and a thickness of 2 mm having a composition of 16Nd-77Fe-7B was obtained. Table 1 shows the magnet characteristics.
The inside of the vacuum vessel is evacuated to 1 × 10 ⁻³ Pa or less, surface sputtering is performed for 20 minutes at an Ar gas pressure of 10 Pa and −500 V to clean the magnet body surface, and then the Ar gas pressure is 0.1 Pa and a bias voltage is applied. A Ti film layer having a thickness of 0.1 μm is formed on the surface of the magnet body by arc ion plating using -80 V, an arc current of 100 A, a substrate magnet temperature of 400 ° C., and a metal Ti as a target.
Next, with a substrate magnet of 400 ° C, a bias voltage of -100V, and an arc current of 100A, Ar: N ₂ = 9: 1 mixed gas 1Pa was introduced, and the mixed gas ratio Ar: N ₂ ratio 9: 1 → 7: 3 → 5: 5 → 3: 7 → 0: 10 The mixed gas composition was changed continuously, and a layer made of a composition TiNx having a film thickness of 0.3 μm was formed on the surface of the Ti coating in 30 minutes.
Further, arc ion plating was performed at 1 Pa of N2 gas, a bias voltage of −100 V, and an arc current of 100 A, and a 3 μm TiN film was formed on the layer made of the composition TiNx in 3 hours.
Then, after allowing to cool, the permanent magnet having the TiN coating obtained on its surface was measured for 1000 hours after standing for 1000 hours at a temperature of 80 ° C. and a relative humidity of 90%. Shown in Table 2.
[0020]
Comparative Example 1
After cleaning the surface of a magnet test piece having the same composition as in Example 1 under the same conditions as in Example 1, after forming a 1.0 μm thick Ti film under the same conditions as in Example 1, the Example was formed on the Ti film. A TiN film was formed to a thickness of 3 μm under the same conditions as in 1.
Thereafter, the magnet properties after 1000 hours of standing under the conditions of the same temperature of 80 ° C. and 90% relative humidity as in Example 1 were measured, and the results are shown in Table 2.
[0021]
【table 1】

[0022]
[Table 2]

[0023]
As shown in Table 2, a comparative example magnet in which a Ti coating and a TiN coating layer are provided on the surface of an Fe-B-Ra permanent magnet body having the same magnet characteristics has a temperature of 80 ° C. and a relative humidity of 90%. whereas the degradation of time left for the magnetic properties before and after the corrosion test is large and rusting, TiN coating layer through a layer of nitrogen concentration of the composition TiNx you increase continuously on the Ti film and It is clear that the provided Fe—B—Ra permanent magnet of the present invention does not generate rust and has almost no change in magnet characteristics.
[0024]
【The invention's effect】
Fe-B-Ra-based permanent magnet body nitrogen concentration through a layer having a composition TiNx you increase continuously provided a TiN coating layer on the Ti coating film provided on the magnet surface according to the present invention, examples As described above, after standing for 1000 hours under severe corrosion resistance test conditions, especially at a temperature of 80 ° C and a relative humidity of 90%, there is almost no deterioration of the magnetic properties, and the most demanded high performance and low cost at present. Very suitable as a permanent magnet.

Claims

It has a Ti film with a film thickness of 0.1 μm to 3.0 μm formed directly on the surface of the Fe-B-Ra permanent magnet body, the main phase of which is a tetragonal phase, and the nitrogen concentration is sequentially increased from the magnet body side on the Ti film. a layer having a composition TiNx film thickness 0.05μm~2.0μm which increases continuously, characterized in that the TiN coating layer with a thickness of 0.5 μ m ~ 10 μ m is formed in a layer on a made of the composition TiNx Corrosion resistant permanent magnet.

After cleaning the surface of the Fe-B-Ra permanent magnet body, the main phase of which is a tetragonal phase, the film thickness is maintained on the surface of the magnet body maintained at 200 ° C to 500 ° C by ion plating using Ti as the target. A 0.1 μm to 3.0 μm Ti film is formed, and a mixed gas of Ar and N _{2 is} introduced into the processing vessel by the above method while continuously increasing the amount of N _{2 at a} constant gas pressure, and the film is formed on the Ti film. a layer of nitrogen concentration of the composition TiNx having a thickness of 0.05 μ m ~2.0μm continuously increases in internal form, the processing chamber from the composition TiNx in the gas pressure constant N ₂ gas atmosphere by the method A method for producing a corrosion-resistant permanent magnet, comprising forming a TiN coating layer having a thickness of 0.5 μm to 10 μm on a layer to be formed.