JP3667783B2 - Method for producing raw powder for anisotropic bonded magnet - Google Patents
Method for producing raw powder for anisotropic bonded magnet Download PDFInfo
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- JP3667783B2 JP3667783B2 JP27624593A JP27624593A JP3667783B2 JP 3667783 B2 JP3667783 B2 JP 3667783B2 JP 27624593 A JP27624593 A JP 27624593A JP 27624593 A JP27624593 A JP 27624593A JP 3667783 B2 JP3667783 B2 JP 3667783B2
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- 239000000843 powder Substances 0.000 title claims description 57
- 238000004519 manufacturing process Methods 0.000 title claims description 17
- 239000013078 crystal Substances 0.000 claims description 50
- 238000000034 method Methods 0.000 claims description 39
- 229910045601 alloy Inorganic materials 0.000 claims description 29
- 239000000956 alloy Substances 0.000 claims description 29
- 238000005266 casting Methods 0.000 claims description 28
- 239000002994 raw material Substances 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 24
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 19
- 239000007789 gas Substances 0.000 claims description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 14
- 239000001257 hydrogen Substances 0.000 claims description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims description 13
- 239000011261 inert gas Substances 0.000 claims description 11
- 229910052779 Neodymium Inorganic materials 0.000 claims description 6
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052733 gallium Inorganic materials 0.000 claims description 6
- 229910052735 hafnium Inorganic materials 0.000 claims description 6
- 229910052738 indium Inorganic materials 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 6
- 229910052715 tantalum Inorganic materials 0.000 claims description 6
- 229910052718 tin Inorganic materials 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 229910052721 tungsten Inorganic materials 0.000 claims description 6
- 229910052720 vanadium Inorganic materials 0.000 claims description 6
- 229910052726 zirconium Inorganic materials 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 12
- 150000001875 compounds Chemical class 0.000 description 8
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 8
- 238000000354 decomposition reaction Methods 0.000 description 8
- 230000005415 magnetization Effects 0.000 description 7
- 238000005096 rolling process Methods 0.000 description 7
- 238000005984 hydrogenation reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000001953 recrystallisation Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 description 1
- 229910000521 B alloy Inorganic materials 0.000 description 1
- 229910000758 Br alloy Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910052692 Dysprosium Inorganic materials 0.000 description 1
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910052689 Holmium Inorganic materials 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 229910052775 Thulium Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229930003836 cresol Natural products 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- 229920003986 novolac Polymers 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0573—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes obtained by reduction or by hydrogen decrepitation or embrittlement
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- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Powder Metallurgy (AREA)
Description
【０００１】
【産業上の利用分野】
この発明は、Ｒ（Ｒは希土類元素の少なくとも１種）、Ｆｅ、Ｂ、Ｍ1（ＭはＣｏ，Ｎｉ，Ｃｒの１種または２種以上）、Ｍ2（Ｍ2はＡｌ，Ｇａ，Ｚｒ，Ｔｉ，Ｖ，Ｎｂ，Ｍｏ，Ｉｎ，Ｓｎ，Ｈｆ，Ｔａ，Ｗのうち少なくとも１種）を主成分とする異方性ボンド磁石用原料粉末の製造方法、特に、ストリップキャスティング法による鋳片から異方性ボンド磁石用合金粉末を得る製造方法に係り、Ｆｅ，Ｂ，Ｒ，Ｍ1，Ｍ2を主成分とする合金溶湯よりストリップキャスティング法にて特定板厚の微細均質組織を有する鋳片を得た後、真空中あるいはＡｒガス中にて特定温度で熱処理することにより、結晶方位が一方向に揃った領域を有する結晶粒を粒成長させ、これに特定条件の水素処理、脱水素処理して、特定の結晶粒度を有する異方性ボンド磁石用合金粉末を得る製造方法に関する。
【０００２】
【従来の技術】
従来、異方性ボンド磁石用原料粉末としては、鋳造法にて磁石組成の鋳塊を得た後、微細な金属組織を生成して保磁力を発現させるため、特定のパターンの熱処理をした後、粉砕して、磁石用粉末として樹脂と混合後、磁場中にて成形、固化して異方性ボンド磁石の製造方法が提案されている。
【０００３】
しかしながら、磁化を高めるために組成を主相となる化合物に近づけると、前記鋳造法によって得られた原料粉末中の結晶方位が一方向に揃った領域での最も短い方向に測定した直径は磁石粉末としての粉末直径よりも小さくなるため、磁石粉末中に方位の異なった多数の結晶が含まれる可能性が大きくなり、十分な配向度が得られず、かえって磁石粉末の磁気的特性（Ｂｒ，（ＢＨ）ｍａｘ）が低下する問題があった。
【０００４】
また、従来の鋳塊粉砕法によるＦｅ−Ｂ−Ｒ系合金粉末の欠点であるα−Ｆｅの残留及び偏析を防止するため、磁石組成の溶湯をストリップキャスティング法により特定厚に急冷凝固した鋳片を粉砕後、前記粉砕粉を磁場中で成形、焼結するＦｅ−Ｂ−Ｒ系焼結磁石の製造方法が提案（特開昭６３−３１７６４３号公報）されている。
【０００５】
【発明が解決しようとする課題】
ストリップキャスティング法により得られた原料粉末は、従来の鋳塊粉砕法により得られた原料粉末に比べ、結晶粒は微細化し、焼結磁石の磁気特性の改善向上には有効であるが、微粉末中の結晶の磁気的方向性がアトランダムであるため、異方性ボンド磁石用原料粉末としては不適であり、異方性ボンド磁石を得ることができなかった。
【０００６】
一方、従来の超急冷法により得られた粉末は熱処理して結晶化し、結晶粒の成長を起こさせることが可能であり、また、超急冷粉末よりボンド磁石を製造する方法としては、前記超急冷粉末をホットプレスしさらに温間塑性変形させる方法や、金属容器に封入した状態にて温間圧延後に粉砕して、異方性ボンド磁石用原料粉末を得て、異方性ボンド磁石を製造することが提案されているが、いずれの方法も製造効率が低く、実用的でない問題があった。
【０００７】
この発明は、Ｆｅ−Ｂ−Ｒ系異方性ボンド磁石を製造するため、磁気特性がすぐれた同系異方性ボンド磁石用原料粉末を製造効率よく得ることを目的とし、特に、製造効率のすぐれたストリップキャスティング法による鋳片より磁気特性がすぐれた異方性ボンド磁石用原料粉末を得る製造方法の提供を目的としている。
【０００８】
【課題を解決するための手段】
発明者らは、従来、異方性ボンド磁石用原料粉末の製造が不可能視されたストリップキャスティング法にて得られた鋳片より、異方性ボンド磁石用原料粉末を得る方法について、種々検討した結果、ストリップキャスティング法により得られた特定組成の鋳片あるいは該鋳片を粗粉砕した粉末を特定の雰囲気、温度条件にて熱処理して、粉末中の結晶内の結晶方位が、一定方向に揃った結晶領域の大きさを最短方向にて２０μｍ以上に粒成長させた後、鋳片あるいは粉砕粉を特定の雰囲気、温度条件で加熱して水素処理した後、特定Ｈ2分圧の雰囲気、温度条件にて脱水素処理を行なうことにより、平均結晶粒径が０．０５〜０．５μｍである磁気的に異方性を有する平均粒度２０〜４００μｍの合金粉末が得られ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、
R(但し、RはYを含む希土類元素のうち少なくとも1種でかつPrまたはNdの1種または2種をRのうち90%以上含有)9.0at%〜15at%、
B5.5at%〜8.0at%、
M1(但し、M1はCo,Ni,Crの1種または2種以上)2at%〜20at%、
M2(但し、M2はAl,Ga,Zr,Ti,V,Nb,Mo,In,Sn,Hf,Ta,Wのうち1種または2種以上)0.01at%〜2.0at%、
残部Fe及び不可避的不純物からなる合金溶湯をストリップキャスティング法にて、主相のR2Fe14B結晶の短軸方向寸法が0.1μm〜50μm、長軸方向寸法が 5 μ m 〜 200 μ m である板厚0.03mm〜10mmの鋳片に鋳造後、
真空中または不活性ガス雰囲気中で1000℃〜1200℃の温度で30分〜48時間の熱処理をして、結晶内の結晶方位が一定方向に揃った結晶領域の大きさを最短方向に20μm以上に粒成長させた後、
前記鋳片及び/又は粉末(前記鋳片又は粉末あるいは鋳片及び粉末)を10kPa〜1000kPaのH2ガス中で750〜900℃に15分〜8時間加熱保持する水素処理を施し、
更にH2分圧10kPa以下にて700〜900℃に5分〜8時間保持する脱水素処理を行ない、
次いで冷却し、熱処理工程の前工程または水素処理及び脱水素処理工程の前工程あるいは後工程で粉砕を行い、平均結晶粒径が0.05〜0.5μmである磁気的に異方性を有する平均粒度20〜400μmの合金粉末を得ることを特徴とする異方性ボンド磁石用合金粉末の製造方法である。
【００１０】
この発明は、上記の構成において、
熱処理または水素処理及び脱水素処理工程の前工程あるいは後工程で粉砕を行う異方性ボンド磁石用合金粉末の製造方法、
また、ストリップキャスティング法にて鋳造し、熱処理を施した後、冷却された鋳片及び／又は粉末を、真空中または不活性ガス中で温度７５０℃以上の温度域まで昇温後、水素処理を施す異方性ボンド磁石用原料粉末の製造方法を併せて提案する。
【００１１】
この発明に使用する原料合金に用いるＲすなわち希土類元素は、Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，Ｌｕが包含され、このうち少なくとも１種以上で、Ｐｒ，Ｎｄのうち少なくとも１種または２種をＲのうち９０％以上含有し、さらにＲのすべてがＰｒ，Ｎｄのうち１種または２種の場合がある。
Ｒの９０％以上をＰｒ，Ｎｄのうち少なくとも１種以上とするのは、９０％未満では十分な磁化が得られないためである。
Ｒは、９．０ａｔ％未満ではα−Ｆｅ相の析出により保磁力が低下し、また１５ａｔ％を超えると、目的とする正方晶Ｎｄ2Ｆｅ14Ｂ型化合物以外に、Ｒリッチの第２相が多く析出し、この第２相が多すぎると合金の磁化を低下させる。従って、Ｒの範囲は、９．０〜１５．０ａｔ％とする。
【００１２】
Ｂについては、正方晶Ｎｄ2Ｆｅ14Ｂ型結晶構造を安定して析出させるためには必須である。添加量は５．５ａｔ％以下ではＲ2Ｔ17相が析出して保磁力を低下させ、また減磁曲線の角型性が著しく損なわれる。また、８．０ａｔ％を超えて添加した場合は、磁化の小さい第２相が析出して粉末の磁化を低下させる。従って、Ｂは５．５〜８．０ａｔ％とした。
【００１３】
Ｍ1はＣｏ，Ｎｉ，Ｃｒの１種または２種以上であり、Ｍ1が２ａｔ％未満では低保磁力、低磁化の第２相が析出して磁気的特性が低下し、また２０ａｔ％を超えるとα−Ｆｅ相の析出により保磁力、角型性が低下するため、Ｍ1は２〜２０ａｔ％とする。
【００１４】
添加元素Ｍ2の効果は、水素処理時に母相の分解反応を完全に終了させずに、母相すなわちＲ2Ｔ14Ｂ相を安定化して故意に残存させるのに有効な元素が望まれる。特に顕著な効果を持つものとして、Ａｌ，Ｔｉ，Ｖ，Ｇａ，Ｚｒ，Ｎｂ，Ｍｏ，Ｉｎ，Ｓｎ，Ｈｆ，Ｔａ，Ｗがある。
Ｍ2が０．０１ａｔ％未満では添加効果が十分発揮できず、また２．０ａｔ％を超えると水素化反応の進行が抑制されすぎて、保磁力角型性が低下する問題があり、好ましくないため、Ｍ2は０．０１〜２．０ａｔ％とする。
【００１５】
Ｆｅは、本系組成の基幹をなし上述の各元素の含有残余を占める。
【００１６】
この発明のストリップキャスティング法により得られた特定組成のＲ−Ｆｅ−Ｂ系合金の断面組織は、主相のＲ2Ｆｅ14Ｂ結晶が従来の鋳型に鋳造して得られた鋳塊のものに比べて約１／１０以上も微細であり、例えば、その短軸方向の寸法は０．１〜５０μｍ、長軸方向は５〜２００μｍの微細結晶であり、かつその主相結晶粒を取り囲むようにＲリッチ相が微細に分散されており、局部に遍在している領域においても、その大きさは２０μｍ以下である。Ｒリッチ相の存在はこの発明の目的のために必要でなく、Ｎｄを９〜１２ａｔ％、Ｂを５．５〜６．５ａｔ％に限定することによって、その存在を実質的になくすことができる。
【００１７】
この発明の特定組成のＲリッチ相が微細に分離した組織を有する磁石材料の鋳片は、特定組成の合金溶湯を単ロール法、あるいは双ロール法によるストリップキャスティング法にて製造される。得られた鋳片は板厚が０．０３〜１０ｍｍの薄板材であり、所望の鋳片板厚により、単ロール法と双ロール法を使い分けるが、板厚が厚い場合は双ロール法を、また板厚が薄い場合は単ロール法を採用したほうが好ましい。
鋳片の板厚を０．０３〜１０ｍｍに限定した理由は、０．０３ｍｍ未満では急冷効果が大となり、結晶粒径が０．１μｍより小となり、溶態化による結晶粒の拡大が困難となるため、磁気特性の劣化を招来するので好ましくなく、また１０ｍｍを超えると、冷却速度が遅くなり、α−Ｆｅが晶出しやすく、Ｎｄリッチ層の遍在も生じるため、磁気特性が低下するので好ましくないことによる。
【００１８】
この発明において、ストリップキャスティング法により得られた特定組成の鋳片を真空中または不活性ガス雰囲気中の熱処理条件として、温度が1000℃未満では拡散速度が十分ではなく、結晶粒が成長せず、また1200℃を超えるとNd2Fe14B相の融点を超えるので好ましくない。
また、加熱時間も30分未満では十分な結晶粒成長が行なわれず、また1000℃〜1200℃の高温での処理時間が48時間を超えると処理のコスト上昇を招来するので好ましくない。
この発明において、上記処理が重要であり、この熱処理により結晶内の結晶方位が定方向に揃った結晶領域の大きさを最短方向にて20μm以上に粒成長させることができる。粒成長が20μm未満では製品粉末が方位の異なる多数個の結晶粒からなる多結晶組織の粉末粒子を多く含むことになり、磁化が低下するので好ましくない。
【００１９】
この発明において、水素処理法は、所要粒度の粗粉砕粉が外観上その大きさを変化させることなく、極微細結晶組織の集合体が得られることを特徴とする。すなわち、正方晶Ｎｄ2Ｆｅ14Ｂ型化合物に対し、高温、実際上は６００℃〜９００℃の温度範囲でＨ2ガスと反応させると、ＲＨ2〜 3、αＦｅ、Ｆｅ2Ｂなどに相分離し、さらに同温度域でＨ2ガスを脱Ｈ2処理により除去すると、再度正方晶Ｎｄ2Ｆｅ14Ｂ型化合物の再結晶組織が得られる。
しかしながら、現実には、水素処理条件によって分解生成物の結晶粒径、反応の度合いが異なり、水素化状態の金属組織は、水素化温度７５０℃未満と７５０℃以上で明らかに異なる。この金属組織上の違いが、脱水素処理を行った後の磁粉の磁気的性質に大きく影響する。
【００２０】
水素処理におけるＨ2ガス中での加熱処理温度は、６００℃未満ではＲＨ2〜 3、αＦｅ、Ｆｅ2Ｂなどへの分解反応が起こらない。また、６００℃〜７５０℃の温度範囲では分解反応がほぼ完全に進行してしまい、分解生成物中に適量のＲ2Ｔ14Ｂ相が残存せず、脱水素処理後に磁気的、また結晶方位的に充分な異方性が得られない。また９００℃を超えるとＲＨ2〜 3が不安定となり、かつ生成物が粒成長して正方晶Ｎｄ2Ｆｅ14Ｂ型化合物極微細結晶組織を得ることが困難になる。
水素化の温度範囲が７５０℃〜９００℃の領域であれば、脱水素時の再結晶反応の核となるＲ2Ｔ14Ｂ相が分散して適量残存するため、脱水素後のＲ2Ｔ14Ｂ相の結晶方位が残存Ｒ2Ｔ14Ｂ相によって決定され、結果的に再結晶組織の結晶方位が原料インゴットの結晶方位と一致し、少なくとも原料インゴットの結晶粒径の範囲内では大きな異方性を示すことになる。そのため、水素化処理の温度範囲を７５０℃〜９００℃とする。
また、加熱処理保持時間については、上記の分解反応を充分に行わせるためには１５分以上必要であり、また、８時間を越えると残存Ｒ2Ｔ14Ｂ相が減少するため、脱水素後の異方性が低下するので好ましくない、よって、１５分〜８時間の加熱保持とする。
この発明において、Ｈ2ガス中での熱処理に際し、Ｈ2ガス圧力が１０ｋＰａ未満では、前述の分解反応が充分に進行せず、また１０００ｋＰａを超えると処理設備が大きくなりすぎ、工業的にコスト面、また安全面で好ましくないため、圧力範囲を１０〜１０００ｋＰａとした。さらに好ましい圧力範囲は２０〜１５０ｋＰａである。
【００２１】
また、この発明における真空中または不活性ガス中での昇温は、昇温速度、保持時間などを特に規定するものではなく、目的は７５０℃以下で水素ガスと原料を反応させないことである。従って、７５０℃以下での処理条件は、雰囲気以外は特に規定しない。なお、ここでの不活性ガスとはＡｒガスまたはＨｅガスであって、通常不活性ガスとして扱われることの多いＮ2ガスは、本系原料と高温域で反応してしまうため、不活性ガスとしては好ましくない。
【００２２】
この発明において、脱水素処理時のＨ2分圧は、１０ｋＰａを超えると下記の温度範囲、すなわち９００℃以下ではＲＨ2〜 3相の分解条件に至らないため、１０ｋＰａ以下とする。また好ましくは１Ｐａ〜１ｋＰａの範囲である。
脱水素処理時の温度が７００℃未満では、ＲＨ2〜 3相からのＨ2の離脱が起こらないか、正方晶Ｎｄ2Ｆｅ14Ｂ型化合物の再結晶が充分進行しない。また、９００℃を超えると正方晶Ｎｄ2Ｆｅ14Ｂ型化合物は生成するが、再結晶粒が粗大に成長し、高い保磁力が得られない。そのため、脱Ｈ2処理の温度範囲は７００℃〜９００℃とする。
また、脱水素処理保持時間は、処理設備の排気能力にもよるが、上記の再結晶反応を充分に行わせることも重要であり、少なくとも５分以上保持する必要があるが、２次的な再結晶反応によって結晶が粗大化すれば保磁力の低下を招くので、できる限り短時間の方が好ましい。そのため、５分〜８時間の加熱保持で充分である。
脱水素処理は、原料の酸化防止の観点から、また処理設備の熱効率の観点で、水素化処理に引き続いて行うのがよいが、水素化処理後、一旦原料を冷却して、再び改めて脱水素のための熱処理を行うこともできる。
【００２３】
この発明において、脱水素処理後の正方晶Ｎｄ2Ｆｅ14Ｂ型化合物の再結晶粒径は実質的に０．０５μｍ以下の平均再結晶粒径を得ることは困難であり、またたとえ得られたとしても磁気特性上の利点がない。一方、平均再結晶粒径が０．５μｍを超えると、粉末の保磁力が低下するため好ましくない。そのため、平均再結晶粒径を０．０５μｍ〜０．５μｍとした。
【００２４】
この発明において、得られた合金粉末の平均粒度を２０〜４００μｍに限定したのは、２０μｍ未満では粉末の酸化による磁性劣化の恐れがあり、また４００μｍを超えると小型磁気部品の精密成形に際して、ボンド磁石の原料として粗大化して好ましくないことによる。
平均粒度２０〜４００μｍの合金粉末を得るには、粒成長させるための特定条件の熱処理工程の前に粉砕するか、また、この熱処理工程後、極微細結晶組織の集合体を得るための特定条件の水素処理及び脱水素処理前に粉砕するか、あるいは水素処理及び脱水素処理工程の後に粉砕するとよい。
【００２５】
【作用】
この発明は、Ｒ（Ｒは希土類元素の少なくとも１種）、Ｆｅ、Ｂ、Ｍ1（ＭはＣｏ，Ｎｉ，Ｃｒの１種または２種以上）、Ｍ2（Ｍ2はＡｌ，Ｇａ，Ｚｒ，Ｔｉ，Ｖ，Ｎｂ，Ｍｏ，Ｉｎ，Ｓｎ，Ｈｆ，Ｔａ，Ｗのうち少なくとも１種）を主成分とする合金溶湯を用いて、ストリップキャスティング法にて所要厚みの鋳片となした後、真空中または不活性ガス雰囲気中で１０００℃〜１２００℃に３０分〜４８時間の熱処理を施すことにより、鋳片あるいは粉末内の結晶方位が一定方向に揃った結晶領域の大きさを最短方向に２０μｍ以上に粒成長させて、その後、極微細結晶組織の集合体が得られる特定条件の水素処理と脱水素処理を行うことにより、従来、異方性ボンド磁石用原料粉末の製造が不可能視されたストリップキャスティング法にて得られた鋳片より、磁気特性がすぐれた異方性ボンド磁石用原料粉末を得ることができる。
【００２６】
【実施例】
実施例１
高周波溶解炉にて、溶解して得られたＮｄ１３．４−Ｆｅ残−Ｃｏ１１−Ｂ６．７−Ｇａ１−Ｚｒ０．１組成の合金溶湯を直径２００ｍｍの銅製ロールを用いた片ロール法にて、板厚０．５ｍｍの薄板状鋳片を得た。この合金を真空中で１１２０℃に１２時間の熱処理を行ない、結晶粒を成長させた。この場合の平均結晶粒径は約８０μｍになった。
この合金を真空中で８４０℃まで加熱し、絶対圧２気圧のＨ2ガスを導入して４時間保持した後、１気圧に減圧し、１気圧のＡｒ流気を２０分行ない、その後８４０℃に保持したまま減圧し、１００Ｔｏｒｒの圧力で２時間保持する脱Ｈ2処理を行なった。
その後合金を粉砕して、３８〜１５０μｍの粒度に粉砕粉を得た。前記粉砕粉に２．５ｗｔ％のクレゾールノボラソク型樹脂を混合し、１５ｋＯｅの磁界中で６Ｔｏｎ／ｃｍ2の圧力を印加して成形、１６０℃に１時間硬化して、１０ｍｍ角の立方体ボンド磁石を得た。ＢＨトレーサーにて磁気特性を測定した結果を表１に示す。
【００２７】
比較例１
実施例１と同一組成のストリップキャスティング法による鋳片を熱処理することなく、直接実施例１と同一条件のＨ2処理後、実施例１と同一条件にてボンド磁石化した。得られたボンド磁石の特性を表１に示す。
【００２８】
【表１】
実施例２
表２に示す組成（ａｔ％）の合金溶湯を、実施例１と同様にストリップキャスティング法にて板厚０．５ｍｍの薄板状鋳片を得た。その後薄板状鋳片を粉砕し、さらに真空中で１１５０℃に１２時間の熱処理を行ない、結晶粒を成長させた。この場合の平均結晶粒径は約９５μｍになった。
この合金を真空中で８５０℃まで加熱し、１８気圧のＨ2ガスを導入して４時間保持した後、１気圧に減圧し、１気圧のＡｒ流気を２０分行ない、その後８５０℃に保持したまま、８５０Ｔｏｒｒの圧力で３時間保持する脱Ｈ2処理を行なった。
その後、実施例１と同一条件にてボンド磁石化した。得られたボンド磁石の特性を表３に示す。
【００３０】
実施例３
表２に示す組成（ａｔ％）の合金溶湯を、実施例１と同様にストリップキャスティング法にて板厚０．５ｍｍの薄板状鋳片を得た。この合金をＡｒガス中で１１２０℃に２０時間の熱処理を行ない、結晶粒を成長させた。この場合の平均結晶粒径は約８０μｍになった。その後合金を粉砕して、３８〜１５０μｍの粒度に粉砕粉を得た。
この合金を真空中で８５０℃まで加熱し、２気圧のＨ2ガスを導入して４時間保持した後、１気圧に減圧し、気圧のＡｒ流気を２０分行ない、その後８５０℃に保持したまま、８５０Ｔｏｒｒの圧力で３時間保持する脱Ｈ2処理を行なった。
その後、実施例１と同一条件にてボンド磁石化した。得られたボンド磁石の特性を表３に示す。
【００３１】
【表２】
【表３】
【発明の効果】
この発明は、従来、異方性ボンド磁石用原料粉末の製造が不可能視されたストリップキャスティング法にて得られた鋳片より、磁気特性がすぐれた異方性ボンド磁石用原料粉末を得るもので、実施例に明らかなように、Ｒ（Ｒは希土類元素の少なくとも１種）、Ｆｅ、Ｂ、Ｍ1（ＭはＣｏ，Ｎｉ，Ｃｒの１種または２種以上）、Ｍ2（Ｍ2はＡｌ，Ｇａ，Ｚｒ，Ｔｉ，Ｖ，Ｎｂ，Ｍｏ，Ｉｎ，Ｓｎ，Ｈｆ，Ｔａ，Ｗのうち少なくとも１種）を主成分とする合金溶湯を用いて、ストリップキャスティング法にて所要厚みの鋳片となした後、真空中または不活性ガス雰囲気中で１０００℃〜１２００℃に３０分〜４８時間の熱処理を施すことにより、鋳片あるいは粉末内の結晶方位が一定方向に揃った結晶領域の大きさを最短方向に２０μｍ以上に粒成長させて、その後、極微細結晶組織の集合体が得られる特定条件の水素処理と脱水素処理を行うことにより、生産効率よく、高性能の異方性ボンド磁石用原料粉末を得ることができる。[0001]
[Industrial application fields]
In the present invention, R (R is at least one of rare earth elements), Fe, B, M 1 (M is one or more of Co, Ni, Cr), M 2 (M 2 is Al, Ga, Zr). , Ti, V, Nb, Mo, In, Sn, Hf, Ta, and W) as a main component, a method for producing a raw material powder for an anisotropic bonded magnet, particularly from a slab by strip casting. TECHNICAL FIELD The present invention relates to a manufacturing method for obtaining an alloy powder for an anisotropic bonded magnet, and a slab having a fine homogeneous structure having a specific plate thickness by a strip casting method from a molten alloy containing Fe, B, R, M 1 and M 2 as main components. Then, heat treatment is performed at a specific temperature in a vacuum or Ar gas to grow crystal grains having a region where crystal orientations are aligned in one direction, and hydrogen treatment and dehydrogenation treatment are performed under specific conditions. An anisotropic bob with a specific grain size The present invention relates to a manufacturing method for obtaining an alloy powder for a green magnet.
[0002]
[Prior art]
Conventionally, as a raw material powder for anisotropic bonded magnets, after obtaining an ingot of a magnet composition by a casting method, after heat treatment of a specific pattern in order to generate a fine metal structure and express coercive force A method for producing an anisotropic bonded magnet has been proposed that is pulverized and mixed with a resin as a magnet powder and then molded and solidified in a magnetic field.
[0003]
However, when the composition is brought close to the main phase compound to increase the magnetization, the diameter measured in the shortest direction in the region where the crystal orientations in the raw material powder obtained by the casting method are aligned in one direction is the magnet powder. Therefore, the possibility that a large number of crystals with different orientations are included in the magnet powder increases, and a sufficient degree of orientation cannot be obtained. On the contrary, the magnetic properties (Br, ( There was a problem that BH) max) decreased.
[0004]
In addition, in order to prevent α-Fe residual and segregation, which is a defect of the Fe-BR alloy powder by the conventional ingot crushing method, the slab was rapidly solidified to a specific thickness by a strip casting method. Has been proposed (JP-A-63-317643) for producing a Fe—BR—sintered magnet in which the pulverized powder is molded and sintered in a magnetic field.
[0005]
[Problems to be solved by the invention]
The raw material powder obtained by the strip casting method is effective in improving the magnetic properties of the sintered magnet, although the crystal grains are refined compared to the raw material powder obtained by the conventional ingot crushing method. Since the magnetic orientation of the crystal inside is at random, it was unsuitable as a raw material powder for an anisotropic bonded magnet, and an anisotropic bonded magnet could not be obtained.
[0006]
On the other hand, the powder obtained by the conventional ultra-quenching method can be crystallized by heat treatment to cause the growth of crystal grains. Also, as a method for producing a bonded magnet from the ultra-quenched powder, the ultra-quenching method can be used. A method of hot-pressing the powder and further plastically deforming it, or crushing after warm rolling in a state of being enclosed in a metal container to obtain a raw material powder for anisotropic bonded magnet, and manufacturing an anisotropic bonded magnet However, each method has a problem in that the production efficiency is low and it is not practical.
[0007]
An object of the present invention is to produce a Fe—B—R system anisotropic bonded magnet, and to obtain a raw material powder for the same type anisotropic bonded magnet having excellent magnetic properties with high manufacturing efficiency. Another object of the present invention is to provide a production method for obtaining a raw material powder for anisotropic bonded magnets having better magnetic properties than a cast slab produced by strip casting.
[0008]
[Means for Solving the Problems]
The inventors conducted various studies on methods for obtaining raw material powder for anisotropic bonded magnets from slabs obtained by the strip casting method in which production of raw material powder for anisotropic bonded magnets has been impossible. As a result, the slab of a specific composition obtained by the strip casting method or a powder obtained by roughly pulverizing the slab is heat-treated in a specific atmosphere and temperature condition, and the crystal orientation in the crystal in the powder is in a certain direction. After the grain size of the aligned crystal region is grown to 20 μm or more in the shortest direction, the slab or pulverized powder is heated in a specific atmosphere and temperature condition to be subjected to hydrogen treatment, and then an atmosphere having a specific H 2 partial pressure, It has been found that by performing dehydrogenation treatment under temperature conditions, an alloy powder having an average grain size of 0.05 to 0.5 μm and magnetically anisotropic average grain size of 20 to 400 μm can be obtained. Complete the invention It was.
[0009]
That is, this invention
R (provided that R is at least one of rare earth elements including Y and contains one or two of Pr or Nd in 90% or more of R) 9.0 at% to 15 at%,
B5.5at% ~ 8.0at%,
M 1 (where M 1 is one or more of Co, Ni, Cr) 2at% to 20at%,
M 2 (where M 2 is one or more of Al, Ga, Zr, Ti, V, Nb, Mo, In, Sn, Hf, Ta, W) 0.01 at% to 2.0 at%,
The molten alloy and the balance Fe and unavoidable impurities by a strip casting method, the minor axis dimension of the R 2 Fe 14 B crystal main phase 0.1Myuemu～50myuemu, longitudinal dimension at 5 μ m ~ 200 μ m after casting to cast pieces of a certain thickness 0.03mm~10mm,
Heat treatment in a vacuum or in an inert gas atmosphere at a temperature of 1000 ° C. to 1200 ° C. for 30 minutes to 48 hours, the size of the crystal region in which the crystal orientation in the crystal is aligned in a certain direction is 20 μm or more in the shortest direction After growing the grains into
The slab and / or powder (the slab or powder or slab and powder) is subjected to hydrogen treatment in which heat is maintained at 750 to 900 ° C. for 15 minutes to 8 hours in H 2 gas of 10 kPa to 1000 kPa,
In addition, dehydrogenation treatment is performed at 700 to 900 ° C. for 5 minutes to 8 hours at a H 2 partial pressure of 10 kPa or less,
Next, it is cooled and pulverized in the pre-process of the heat treatment process or the pre-process or post-process of the hydrogen treatment and dehydrogenation process, and the average crystal grain size is 0.05 to 0.5 μm. An alloy powder for anisotropic bonded magnets is obtained by obtaining an alloy powder of ˜400 μm.
[0010]
The present invention is configured as described above,
A method for producing an alloy powder for anisotropic bonded magnet, which is pulverized in a pre-process or post-process of heat treatment or hydrogen treatment and dehydrogenation treatment process,
Also, after casting by strip casting and heat treatment, the cooled slab and / or powder is heated to a temperature range of 750 ° C. or higher in vacuum or inert gas, and then subjected to hydrogen treatment. The manufacturing method of the raw material powder for anisotropic bonded magnets to apply is also proposed.
[0011]
R, that is, a rare earth element used in the raw material alloy used in the present invention includes Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and at least one of them is included. In some cases, at least one or two of Pr and Nd are contained in 90% or more of R, and all of R may be one or two of Pr and Nd.
The reason why 90% or more of R is at least one of Pr and Nd is that if it is less than 90%, sufficient magnetization cannot be obtained.
If R is less than 9.0 at%, the coercive force decreases due to precipitation of the α-Fe phase, and if it exceeds 15 at%, in addition to the target tetragonal Nd 2 Fe 14 B type compound, R-rich second phase When a large amount of the second phase is precipitated, the magnetization of the alloy is lowered. Accordingly, the range of R is 9.0 to 15.0 at%.
[0012]
For B, and order to stably precipitate the tetragonal Nd 2 Fe 14 B type crystal structure is essential. If the addition amount is 5.5 at% or less, the R 2 T 17 phase precipitates to lower the coercive force, and the squareness of the demagnetization curve is significantly impaired. Moreover, when adding exceeding 8.0 at%, the 2nd phase with small magnetization precipitates and the magnetization of powder is reduced. Therefore, B is set to 5.5 to 8.0 at%.
[0013]
M 1 is one or more of Co, Ni, and Cr. If M 1 is less than 2 at%, a second phase having a low coercive force and low magnetization is precipitated and the magnetic properties are lowered, and 20 at% is reduced. If exceeding, coercive force and squareness will decrease due to precipitation of the α-Fe phase, so M 1 is made 2 to 20 at%.
[0014]
The effect of the additive element M 2 is desired to be an element effective for stabilizing and deliberately leaving the parent phase, that is, the R 2 T 14 B phase, without completely terminating the decomposition reaction of the parent phase during the hydrogen treatment. Examples of particularly remarkable effects include Al, Ti, V, Ga, Zr, Nb, Mo, In, Sn, Hf, Ta, and W.
If M 2 is less than 0.01 at%, the effect of addition cannot be sufficiently exhibited, and if it exceeds 2.0 at%, the progress of the hydrogenation reaction is excessively suppressed, and there is a problem that the coercivity squareness is lowered, which is not preferable. Therefore, M 2 is a 0.01~2.0at%.
[0015]
Fe forms the basis of this system composition, and occupies the remainder of the content of each element described above.
[0016]
The cross-sectional structure of the R—Fe—B alloy having a specific composition obtained by the strip casting method of the present invention is that of an ingot obtained by casting the main phase R 2 Fe 14 B crystal in a conventional mold. Compared to, for example, a fine crystal having a minor axis dimension of 0.1 to 50 μm and a major axis direction of 5 to 200 μm, and surrounding the main phase crystal grains. Even in the region where the R-rich phase is finely dispersed and is ubiquitous locally, the size is 20 μm or less. The presence of the R-rich phase is not necessary for the purposes of this invention, and its presence can be substantially eliminated by limiting Nd to 9-12 at% and B to 5.5-6.5 at%. .
[0017]
The slab of a magnet material having a structure in which the R-rich phase having a specific composition according to the present invention is finely separated is manufactured by strip casting using a single-roll method or a twin-roll method with a molten alloy having a specific composition. The obtained slab is a thin plate material having a plate thickness of 0.03 to 10 mm. Depending on the desired slab plate thickness, the single roll method and the twin roll method are used separately. Further, when the plate thickness is thin, it is preferable to adopt the single roll method.
The reason for limiting the thickness of the slab to 0.03 to 10 mm is that if it is less than 0.03 mm, the rapid cooling effect becomes large, the crystal grain size becomes smaller than 0.1 μm, and it is difficult to expand the crystal grains by solution treatment. Therefore, it is not preferable because it causes deterioration of the magnetic characteristics. When the thickness exceeds 10 mm, the cooling rate becomes slow, α-Fe is easily crystallized, and the ubiquity of the Nd-rich layer occurs, so that the magnetic characteristics deteriorate. Because it is not preferable.
[0018]
In this invention, as a heat treatment condition in a vacuum or an inert gas atmosphere for a slab of a specific composition obtained by a strip casting method, if the temperature is less than 1000 ° C., the diffusion rate is not sufficient, crystal grains do not grow, the excess of 1200 ° C. is not preferable since above the melting point of the Nd 2 Fe 14 B phase.
Further, sufficient grain growth is not performed in the heating time is also less than 30 minutes, and since the processing time at a high temperature of 1000 ° C. ~ 1200 ° C. to lead to cost increase of the process exceeds 48 hours is not preferable.
In the present invention, the above treatment is important, and by this heat treatment, the size of the crystal region in which the crystal orientation in the crystal is aligned in a fixed direction can be grown to 20 μm or more in the shortest direction. If the grain growth is less than 20 μm, the product powder contains many powder particles having a polycrystalline structure consisting of a large number of crystal grains having different orientations, and this is not preferable because the magnetization is lowered.
[0019]
In the present invention, the hydrotreating method is characterized in that a coarsely pulverized powder having a required particle size can obtain an aggregate of an ultrafine crystal structure without changing its size in appearance. That is, when a tetragonal Nd 2 Fe 14 B type compound is reacted with H 2 gas at a high temperature, practically in a temperature range of 600 ° C. to 900 ° C., phase separation into RH 2 to 3 , αFe, Fe 2 B, etc. When the H 2 gas is further removed by de-H 2 treatment in the same temperature range, a recrystallized structure of tetragonal Nd 2 Fe 14 B type compound is obtained again.
However, in reality, the crystal grain size of the decomposition product and the degree of reaction differ depending on the hydrotreating conditions, and the metal structure in the hydrogenated state clearly differs between the hydrogenation temperature of less than 750 ° C. and 750 ° C. or more. This difference in metal structure greatly affects the magnetic properties of the magnetic powder after the dehydrogenation treatment.
[0020]
When the heat treatment temperature in H 2 gas in the hydrogen treatment is less than 600 ° C., the decomposition reaction into RH 2 to 3 , αFe, Fe 2 B or the like does not occur. In addition, the decomposition reaction proceeds almost completely in the temperature range of 600 ° C. to 750 ° C., and an appropriate amount of R 2 T 14 B phase does not remain in the decomposition product. Therefore, sufficient anisotropy cannot be obtained. On the other hand, if it exceeds 900 ° C., RH 2 to 3 become unstable, and the product grows and it becomes difficult to obtain a tetragonal Nd 2 Fe 14 B type compound ultrafine crystal structure.
When the temperature range of hydrogenation is in the range of 750 ° C. to 900 ° C., an appropriate amount of R 2 T 14 B phase, which becomes the nucleus of the recrystallization reaction during dehydrogenation, is dispersed and remains, so that R 2 T after dehydrogenation remains. 14 crystal orientation of the B phase is determined by the residual R 2 T 14 B phase, resulting in crystal orientation of the recrystallized structure is consistent with the crystal orientation of the material ingot, large within the range of the crystal grain size of at least a raw material ingot different Will show direction. Therefore, the temperature range of the hydrogenation treatment is set to 750 ° C to 900 ° C.
In addition, the heat treatment holding time is required to be 15 minutes or longer in order to sufficiently perform the above decomposition reaction, and when it exceeds 8 hours, the remaining R 2 T 14 B phase is reduced. This is not preferable because the anisotropy of the film is lowered. Therefore, the heat holding is performed for 15 minutes to 8 hours.
In this invention, when heat treatment with H 2 gas, H in 2 gas pressure is less than 10 kPa, it does not proceed sufficiently that the above decomposition reaction, also processing facility becomes too large and exceeds 1000 kPa, industrial cost Moreover, since it is not preferable in terms of safety, the pressure range was set to 10 to 1000 kPa. A more preferable pressure range is 20 to 150 kPa.
[0021]
In the present invention, the temperature rise in vacuum or in an inert gas does not particularly define the temperature rise rate, the holding time, etc., and the object is not to react the hydrogen gas and the raw material at 750 ° C. or lower. Accordingly, the processing conditions at 750 ° C. or lower are not particularly defined except for the atmosphere. Note that the inert gas here is Ar gas or He gas, and N 2 gas, which is usually handled as an inert gas, reacts with the raw material in a high temperature range, so that it is an inert gas. It is not preferable.
[0022]
In the present invention, if the H 2 partial pressure during the dehydrogenation process exceeds 10 kPa, the RH 2 to 3 phase decomposition conditions are not reached in the following temperature range, that is, 900 ° C. or less, so that it is 10 kPa or less. Moreover, it is preferably in the range of 1 Pa to 1 kPa.
If the temperature during the dehydrogenation treatment is less than 700 ° C., the separation of H 2 from the RH 2 to 3 phases does not occur or the recrystallization of the tetragonal Nd 2 Fe 14 B type compound does not proceed sufficiently. When the temperature exceeds 900 ° C., a tetragonal Nd 2 Fe 14 B type compound is produced, but the recrystallized grains grow coarsely, and a high coercive force cannot be obtained. Therefore, the temperature range of the de-H 2 treatment is set to 700 ° C to 900 ° C.
In addition, although the dehydrogenation holding time depends on the exhaust capacity of the processing equipment, it is important that the above-mentioned recrystallization reaction is sufficiently performed, and it is necessary to hold at least 5 minutes or more. If the crystal is coarsened by the recrystallization reaction, the coercive force is lowered, so that a shorter time is preferable. Therefore, heating and holding for 5 minutes to 8 hours is sufficient.
The dehydrogenation treatment is preferably performed subsequent to the hydrogenation treatment from the viewpoint of preventing oxidation of the raw materials and from the viewpoint of the thermal efficiency of the processing equipment, but after the hydrogenation treatment, the raw materials are once cooled and dehydrogenated again. It is also possible to perform heat treatment for the purpose.
[0023]
In this invention, the recrystallized grain size of the tetragonal Nd 2 Fe 14 B type compound after the dehydrogenation treatment is substantially difficult to obtain an average recrystallized grain size of 0.05 μm or less. However, there is no advantage in magnetic properties. On the other hand, if the average recrystallized grain size exceeds 0.5 μm, the coercive force of the powder decreases, which is not preferable. Therefore, the average recrystallized grain size is set to 0.05 μm to 0.5 μm.
[0024]
In the present invention, the average particle size of the obtained alloy powder is limited to 20 to 400 μm because if it is less than 20 μm, there is a risk of magnetic deterioration due to oxidation of the powder. This is because it is not preferable because it becomes coarse as a raw material of the magnet.
In order to obtain an alloy powder having an average grain size of 20 to 400 μm, it is pulverized before the heat treatment step under specific conditions for grain growth, or after the heat treatment step, specific conditions for obtaining an aggregate of ultrafine crystal structures. It may be pulverized before the hydrogen treatment and dehydrogenation treatment, or pulverized after the hydrogen treatment and dehydrogenation treatment steps.
[0025]
[Action]
In the present invention, R (R is at least one of rare earth elements), Fe, B, M 1 (M is one or more of Co, Ni, Cr), M 2 (M 2 is Al, Ga, Zr). , Ti, V, Nb, Mo, In, Sn, Hf, Ta, W using a molten alloy whose main component is a slab of the required thickness by the strip casting method, By performing heat treatment at 1000 ° C. to 1200 ° C. for 30 minutes to 48 hours in a vacuum or in an inert gas atmosphere, the size of the crystal region in which the crystal orientation in the slab or powder is aligned in a certain direction is reduced to the shortest direction. Conventionally, it is impossible to produce raw material powder for anisotropic bonded magnets by growing grains to 20 μm or more and then performing hydrogen treatment and dehydrogenation treatment under specific conditions to obtain an aggregate of ultrafine crystal structure. Strip casting method The raw material powder for anisotropic bonded magnets with excellent magnetic properties can be obtained from the slab obtained as described above.
[0026]
【Example】
Example 1
In a high frequency melting furnace, a molten alloy having a composition of Nd13.4-Fe remaining-Co11-B6.7-Ga1-Zr0.1 obtained by melting is obtained by a one-roll method using a copper roll having a diameter of 200 mm. A thin plate cast with a thickness of 0.5 mm was obtained. This alloy was heat-treated at 1120 ° C. for 12 hours in a vacuum to grow crystal grains. In this case, the average crystal grain size was about 80 μm.
This alloy was heated to 840 ° C. in a vacuum, H 2 gas having an absolute pressure of 2 atm was introduced and held for 4 hours, then the pressure was reduced to 1 atm, and 1 atmosphere of Ar was flowed for 20 minutes, and then 840 ° C. The pressure was reduced while the pressure was maintained, and a de-H 2 treatment was performed in which the pressure was maintained at 100 Torr for 2 hours.
Thereafter, the alloy was pulverized to obtain a pulverized powder having a particle size of 38 to 150 μm. The pulverized powder is mixed with 2.5 wt% cresol novolac type resin, molded by applying a pressure of 6 Ton / cm 2 in a magnetic field of 15 kOe, cured at 160 ° C. for 1 hour, and a 10 mm square cube bond A magnet was obtained. Table 1 shows the results of measuring the magnetic properties with a BH tracer.
[0027]
Comparative Example 1
A cast slab by the strip casting method having the same composition as in Example 1 was directly heat treated with H 2 under the same conditions as in Example 1 and then made into a bonded magnet under the same conditions as in Example 1. The properties of the obtained bonded magnet are shown in Table 1.
[0028]
[Table 1]
Example 2
A thin plate-shaped slab having a thickness of 0.5 mm was obtained from the molten alloy having the composition (at%) shown in Table 2 by the strip casting method in the same manner as in Example 1. Thereafter, the thin plate-shaped slab was pulverized and further subjected to heat treatment at 1150 ° C. for 12 hours in a vacuum to grow crystal grains. In this case, the average crystal grain size was about 95 μm.
This alloy is heated to 850 ° C. in a vacuum, 18 atmospheres of H 2 gas is introduced and maintained for 4 hours, then reduced to 1 atmosphere, and 1 atmosphere of Ar is flown for 20 minutes, and then maintained at 850 ° C. In this state, a de-H 2 treatment was performed by maintaining the pressure at 850 Torr for 3 hours.
Thereafter, a bonded magnet was formed under the same conditions as in Example 1. Table 3 shows the properties of the obtained bonded magnet.
[0030]
Example 3
A thin plate-shaped slab having a thickness of 0.5 mm was obtained from the molten alloy having the composition (at%) shown in Table 2 by the strip casting method in the same manner as in Example 1. This alloy was heat-treated at 1120 ° C. for 20 hours in Ar gas to grow crystal grains. In this case, the average crystal grain size was about 80 μm. Thereafter, the alloy was pulverized to obtain a pulverized powder having a particle size of 38 to 150 μm.
This alloy was heated to 850 ° C. in a vacuum, introduced with 2 atmospheres of H 2 gas and maintained for 4 hours, then reduced to 1 atmosphere, and Ar pressure was applied for 20 minutes, and then maintained at 850 ° C. The de-H 2 treatment was performed while maintaining the pressure at 850 Torr for 3 hours.
Thereafter, a bonded magnet was formed under the same conditions as in Example 1. Table 3 shows the properties of the obtained bonded magnet.
[0031]
[Table 2]
[Table 3]
【The invention's effect】
This invention obtains a raw material powder for anisotropic bonded magnets with excellent magnetic properties from a slab obtained by a strip casting method in which production of raw material powder for anisotropic bonded magnets has been impossible in the past. As is apparent from the examples, R (R is at least one rare earth element), Fe, B, M 1 (M is one or more of Co, Ni, Cr), M 2 (M 2 Is a cast alloy having a required thickness by a strip casting method using a molten alloy mainly composed of Al, Ga, Zr, Ti, V, Nb, Mo, In, Sn, Hf, Ta, and W). After being formed into pieces, a heat treatment is performed at 1000 ° C. to 1200 ° C. for 30 minutes to 48 hours in a vacuum or in an inert gas atmosphere, so that a crystal region in which the crystal orientation in the slab or powder is aligned in a certain direction is obtained. Increase the size to 20μm or more in the shortest direction It is possible to obtain a high-performance raw material powder for anisotropic bonded magnet with high production efficiency by carrying out hydrogen treatment and dehydrogenation treatment under specific conditions to obtain an aggregate of ultrafine crystal structure after grain growth. it can.
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| JP27624593A JP3667783B2 (en) | 1993-10-06 | 1993-10-06 | Method for producing raw powder for anisotropic bonded magnet |
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| JP27624593A JP3667783B2 (en) | 1993-10-06 | 1993-10-06 | Method for producing raw powder for anisotropic bonded magnet |
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| JP3667783B2 true JP3667783B2 (en) | 2005-07-06 |
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| JP4754739B2 (en) * | 2001-09-03 | 2011-08-24 | 昭和電工株式会社 | Alloy ingot for rare earth magnet, method for producing the same, and sintered magnet |
| WO2003020993A1 (en) * | 2001-09-03 | 2003-03-13 | Showa Denko K.K. | Rare earth magnet alloy ingot, manufacturing method for the same, r-t-b type magnet alloy ingot, r-t-b type magnet, r-t-b type bonded magnet, r-t-b type exchange spring magnet alloy ingot, r-t-b type exchange spring magnet, and r-t-b type exchange spring bonded magnet |
| US7014718B2 (en) | 2001-09-03 | 2006-03-21 | Showa Denko K.K. | Rare earth magnet alloy ingot, manufacturing method for the same, R-T-B type magnet alloy ingot, R-T-B type magnet, R-T-B type bonded magnet, R-T-B type exchange spring magnet alloy ingot, R-T-B type exchange spring magnet, and R-T-B type exchange spring bonded magnet |
| US8907755B2 (en) * | 2012-03-30 | 2014-12-09 | Toda Kogyo Corporation | R-T-B-based rare earth magnet particles, process for producing the R-T-B- based rare earth magnet particles, and bonded magnet |
| CN111029075B (en) * | 2019-12-31 | 2020-12-29 | 烟台首钢磁性材料股份有限公司 | Preparation method of neodymium iron boron magnetic powder |
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