JP2005057191A - Method of manufacturing rare-earth magnet powder - Google Patents

Method of manufacturing rare-earth magnet powder Download PDF

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JP2005057191A
JP2005057191A JP2003288992A JP2003288992A JP2005057191A JP 2005057191 A JP2005057191 A JP 2005057191A JP 2003288992 A JP2003288992 A JP 2003288992A JP 2003288992 A JP2003288992 A JP 2003288992A JP 2005057191 A JP2005057191 A JP 2005057191A
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powder
rare earth
earth magnet
decarburized
rare
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Akihiko Saguchi
明彦 佐口
Kazutaka Asabe
和孝 阿佐部
Tadashi Fukuda
匡 福田
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/82—Recycling of waste of electrical or electronic equipment [WEEE]

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recycling the powder scrap of rare-earth magnets to raw-material powder for rare-earth magnets. <P>SOLUTION: The method of manufacturing the rare-earth magnet powder includes an oxidation/decarbonization step in which decarbonized powder is obtained by heat-treating the powder scrap of rare-earth magnets at a temperature of 700-1,200°C for 1-10 hours in an atmosphere containing oxygen, and if necessary, carrying out reduction by hydrogen to carry out oxidation/decarbonization treatment; a deacidification step in which deacidification treatment is carried out by adding and mixing a reducing agent composed of an alkaline earth metal and rare-earth oxide powder to the decarbonized powder, further adding, if necessary, metal powder that constitutes alloy components of the rare-earth magnets, and heating the resultant mixture; a rinsing step in which the decarbonized deacidified mixture obtained in the deacidification step is rinsed with deionized water repeatedly for a plurality of times; a vacuum-treatment step in which the reducing agent is removed by heat-treating the decarbonized deacidified mixture obtained in the rinsing step at a temperature of 900°C or higher in a vacuum of 10 Pa or lower for 0.5 hour or longer; and a grinding step in which the rare-earth magnet alloy obtained in the vacuum-treatment step is ground to a prescribed grain size. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、希土類磁石粉末の製造方法に関するものであり、特にNd-Fe-Ｂ系に代表されるＲ-Fe-Ｂ系合金から成る希土類磁石 (Ｒは、Nd、Pr、Dy、Ho、Tbの少なくとも１種類を主成分とする希土類金属、以下、同じ) の製造工程または使用済み機器から発生する希土類磁石の粉末スクラップを、希土類磁石原料粉としてリサイクルするための方法に関する。   The present invention relates to a method for producing a rare earth magnet powder, and in particular, a rare earth magnet made of an R—Fe—B alloy represented by Nd—Fe—B alloy (R is Nd, Pr, Dy, Ho, Tb). The present invention relates to a method for recycling rare earth magnet powder scrap generated from a manufacturing process or used equipment of a rare earth metal containing at least one of the following as a main component (hereinafter the same) as rare earth magnet raw material powder.

希土類磁石のうちでNd-Fe-Ｂ系等のＲ-Fe-Ｂ系希土類磁石は、優れた磁気特性を有すると共に、機械的性質や加工性が比較的良好であることから、一般の各種電化製品から、高性能パソコン、携帯電話、携帯端末、自動車等の主要エレクトロニクス部品に幅広く利用されている。   Among rare earth magnets, Nd-Fe-B and other R-Fe-B rare earth magnets have excellent magnetic properties and relatively good mechanical properties and workability. It is widely used in major electronic components such as products, high-performance personal computers, mobile phones, mobile terminals, and automobiles.

希土類磁石は一般に焼結磁石と、磁石粉末をゴムやプラスチックで結合したボンド磁石に分別されるが、上記用途には、磁気特性の高い焼結磁石が一般的に使用されている。例えば、焼結型のNd-Fe-Ｂ系合金から成る希土類磁石 (以下、単にNd-Fe-Ｂ系またはＲ-Fe-Ｂ系希土類磁石という) の生産量は増加の一途を辿り、世界で約10000 トン／年、国内では約5500トン/ 年が生産されている。このうち、国内の製造工程では、固形、粉末スクラップが約2400トン発生している。さらに希土類磁石原料は、ほとんどが中国に偏在しており、国際情勢によっては価格高騰といった状況も発生する。従って、希土類磁石スクラップのリサイクル技術を確立することは資源節約、価格安定化のためにも重要である。   Rare earth magnets are generally classified into sintered magnets and bonded magnets in which magnet powder is bonded with rubber or plastic, and sintered magnets with high magnetic properties are generally used for the above applications. For example, the production of rare earth magnets made of sintered Nd-Fe-B alloys (hereinafter simply referred to as Nd-Fe-B or R-Fe-B rare earth magnets) has been increasing, About 10,000 tons / year is produced, and about 5500 tons / year is produced in Japan. Of these, approximately 2400 tons of solid and powder scrap are generated in domestic manufacturing processes. Moreover, most rare earth magnet raw materials are unevenly distributed in China, and depending on the international situation, prices may rise. Therefore, establishing rare earth magnet scrap recycling technology is important for resource saving and price stabilization.

さらに環境保護の観点からも、使用済み機器からの有価資源回収の動きが高まっており、本系磁石も例外ではなくリサイクル技術の確立が求められている。   Furthermore, from the viewpoint of environmental protection, there is an increasing trend of recovering valuable resources from used equipment, and this magnet is no exception and establishment of recycling technology is required.

現在、希土類焼結磁石の一般的な製造方法は、原料合金溶製→粉砕→磁場中プレス成形→焼成 (粉末焼結) →加工→防錆 (メッキ等による表面処理) の各工程を経て行われる粉末冶金法による方法である。そのため、長尺焼結品からの小型高寸法精度品の加工 (外周刃、ワイヤソ一等を使った切断) や、予め余肉成形した焼結品の加工 (中ぐり、グラインダ等) 、バリ取り (バレル研磨等) が必須である。   Currently, the general manufacturing method of rare earth sintered magnets is through the following steps: raw material alloy melting → grinding → press forming in magnetic field → firing (powder sintering) → processing → rust prevention (surface treatment by plating etc.) It is a method by the powder metallurgy method. For this reason, processing of small and high dimensional accuracy products from long sintered products (cutting using outer peripheral blades, wire saws, etc.), processing of sintered products that have been pre-molded (boring, grinders, etc.), deburring, etc. (Barrel polishing etc.) is essential.

このような加工工程で発生する粉末スクラップ発生量は、製造工程中に発生するスクラップの中で最も多い。従って、資源の有効活用という点で、加工工程で発生する粉末スクラップの再生方法を早急に確立することが求められている。   The amount of powder scrap generated in such a processing process is the largest among the scraps generated during the manufacturing process. Therefore, it is required to quickly establish a method for reclaiming powder scrap generated in the processing step in terms of effective use of resources.

上記加工工程で発生した希土類磁石の粉末スクラップは、非常に微細であり、乾燥状態では発火性が高いため、一般に研削液と混和したスラリーとして取り扱われている。このスラリーを乾燥して得た粉末スクラップは、一般に約１〜２質量％の炭素を含有している。この炭素量は、Ｒ-Fe-Ｂ系希土類磁石原料粉末中の炭素量(0.08 質量％未満) に比較して極めて高くなっている。この炭素は、本系磁石製造工程中の粉砕助剤 (ステアリン酸亜鉛など) の添加により焼結体中に生成した希土類元素炭化物と、外部炭素源 (加工時の不可避混入) とが主供給源である。そのような具体的な外部炭素源として、水溶性研削油(W/0エマルジョン) 、加工に用いる研削砥石屑 (タングステンカーバイド等の炭化物やダイヤモンド) 、砥石結合剤 (レジン粉) 、研削補助板 (カーボン板) 摩砕粉などが挙げられる。   Since the rare earth magnet powder scrap generated in the above-described processing steps is very fine and has high ignitability in a dry state, it is generally handled as a slurry mixed with a grinding fluid. The powder scrap obtained by drying this slurry generally contains about 1-2% by mass of carbon. This carbon amount is extremely higher than the carbon amount (less than 0.08 mass%) in the R—Fe—B rare earth magnet raw material powder. The main sources of this carbon are rare earth element carbides formed in the sintered body by the addition of grinding aids (such as zinc stearate) during the production process of this magnet and an external carbon source (inevitable contamination during processing). It is. As such specific external carbon sources, water-soluble grinding oil (W / 0 emulsion), grinding wheel scraps (carbide and diamond such as tungsten carbide) used for processing, grinding wheel binder (resin powder), grinding auxiliary plate ( Carbon plate) Examples include ground powder.

このような高炭素含量の粉末スクラップを希土類磁石の原料としてそのまま用いると、そのとき製造される希土類磁石の磁気特性は劣化する。この理由を次に説明する。   If such powder scrap with a high carbon content is used as a raw material for a rare earth magnet as it is, the magnetic properties of the rare earth magnet produced at that time will deteriorate. The reason for this will be described next.

すなわち、Ｒ-Fe-Ｂ系希土類磁石は、強磁性相である主相(R2Fe14B) と非磁性相である粒界相 (Ｒ酸化物、Ｒ炭化物、Ｒ炭酸化物を含んだＲリッチ相およびＢリッチ相) の２相で構成される液相焼結磁石である。原料合金中の初期炭素量が0.08質量％以上では、粒界相に多量のＲ炭化物やＲ炭酸化物が生成されて有効Ｒ量が不足するため、十分な保磁力(Hc)を得ることができない。このために高炭素含量の粉末スクラップに対しては脱炭処理を必要とするのである。 That is, the R—Fe—B rare earth magnet has a main phase (R 2 Fe 14 B) that is a ferromagnetic phase and a grain boundary phase that is a nonmagnetic phase (R containing R oxide, R carbide, R carbonate). A liquid-phase sintered magnet composed of two phases (rich phase and B-rich phase). When the initial carbon content in the raw material alloy is 0.08% by mass or more, a large amount of R carbides and R carbonates are generated in the grain boundary phase and the effective R amount is insufficient, so that sufficient coercive force (Hc) cannot be obtained. . For this reason, decarburization is required for powder scrap with a high carbon content.

一方、加工工程で発生する希土類磁石の粉末スクラップは、通気式粒度測定法により測定した平均粒径が１〜２μm と、非常に微細なスラリー粉末であるため、酸素含量は1.O 質量％以上と、Ｒ-Fe-Ｂ系希土類磁石の原料合金中の酸素含量(0.7質量％未満) に比べて高い。このような高酸素原料粉末をそのまま用いて製造される希土類磁石も磁気特性は劣化する。この理由を次に説明する。   On the other hand, the rare earth magnet powder scrap generated in the processing process is an extremely fine slurry powder with an average particle diameter of 1 to 2 μm as measured by the air-flow-type particle size measurement method, so the oxygen content is 1.O% by mass or more. And the oxygen content (less than 0.7% by mass) in the raw material alloy of the R—Fe—B rare earth magnet. The magnetic properties of a rare earth magnet manufactured using such a high oxygen raw material powder as it is also deteriorated. The reason for this will be described next.

すなわち、酸素含量が高いと粒子表面が過剰な高融点希土類酸化物に覆われるため、焼成における密度の上昇がほとんど認められず、さらに粒界相のＲ酸化物の体積が大きくなるために相対的に主相体積が減少するので、残留磁束密度(Br)が低下する。このため高酸素含量の粉末スクラップに対しては脱酸処理を必要とするのである。   That is, when the oxygen content is high, the particle surface is covered with an excessively high melting point rare earth oxide, so that almost no increase in density is observed during firing, and the volume of the R oxide in the grain boundary phase is increased. Since the main phase volume decreases, the residual magnetic flux density (Br) decreases. For this reason, deoxidation treatment is required for powder scrap having a high oxygen content.

希土類磁石の粉末スクラップの再生方法として、次の各方法が考えられる。
溶媒抽出法:
これは、粉末スクラップを完全酸化物とした後、水と共に攪拌槽に投入、スラリー化させて硝酸、硫酸等の酸溶液を添加して希土類元素イオンとして浸出、分離後、鉄酸化物等の不溶解性沈殿物は濾別分離する方法である。
溶解鋳造法:
これは、粉末スクラップと他の合金成分となる種々の金属等からなる母合金塊とを所要組成に調合し、高周波溶解等で溶解、鋳造後、これを粉砕して所要粒度の合金粉末を得る方法である。
直接還元法:
これは、粉末スクラップを還元剤、例えば金属Caと共に混合加熱・ 脱酸してから、副生成物 (例えばCaO)を崩壊、洗浄除去した後、得られた還元粉末を、微粉砕し、焼結磁石原料粉末として用いる方法である。 The following methods are conceivable as methods for recycling powder scrap of rare earth magnets.
Solvent extraction method:
After making powder scrap into a complete oxide, it is put into a stirring tank together with water, slurried, added with an acid solution such as nitric acid and sulfuric acid, leached as rare earth element ions, separated, and then free of iron oxide and the like. The soluble precipitate is separated by filtration.
Melting casting method:
This consists of preparing powder scrap and mother alloy ingots made of various metals as other alloy components to the required composition, melting and casting by high frequency melting, etc., and then crushing this to obtain alloy powder of the required particle size Is the method.
Direct reduction method:
This is because powder scrap is mixed and heated and deoxidized with a reducing agent, such as metallic Ca, and then by-products (for example, CaO) are disintegrated, washed and removed, and then the resulting reduced powder is pulverized and sintered. It is a method used as a magnet raw material powder.

しかしながら、上記溶媒抽出法は、希土類元素を高純度で分離精製できる特徴を持つ反面、抽出に掛かるコストが高く、また、鉄酸化物等のスクラップを副生成するため、環境負荷の点で問題となっている。   However, the solvent extraction method has a feature that the rare earth element can be separated and purified with high purity. However, the extraction cost is high, and the scrap of iron oxide or the like is by-produced. It has become.

溶解鋳造法は、上記溶媒抽出法に比べると低コストであるが、実用的には、再生スクラップ品の酸素を大幅に低下 (例えば<0.05 質量％) させない限り、通常の母材溶解に比べて高コストとなる。   The melt casting method is less expensive than the solvent extraction method described above, but practically, compared to the conventional base material melting unless the oxygen in the recycled scrap product is significantly reduced (for example, <0.05% by mass). High cost.

直接還元法は、得られる還元粉末が合金粉末として磁石製造に直接適用できるため、最も低コストであり、環境負荷の面でも優れている。しかし、高炭素スクラップを適用した場合に脱炭が行われないという問題と、還元剤として用いたCaが残留するという問題がある。一方で、原料粉末として直接用いるためには成分調整 (主に希土類成分) を必要とする場合がある。この成分調整の方法として、次のような３つの方法が考えられる。   The direct reduction method has the lowest cost and is excellent in terms of environmental load because the obtained reduced powder can be directly applied to magnet production as an alloy powder. However, there is a problem that decarburization is not performed when high carbon scrap is applied, and a problem that Ca used as a reducing agent remains. On the other hand, component adjustment (mainly rare earth components) may be required for direct use as raw material powder. The following three methods are conceivable as methods for adjusting the components.

(1) 所定成分の合金粗粉末と混合して微粉砕を行い、原料粉末の成分を調整する。   (1) The raw material powder components are adjusted by mixing and pulverizing with a predetermined alloy coarse powder.

(2) 予め微粉砕された所定成分の合金微粉末を混練して原料粉末の成分を調整する。   (2) The alloy powder of a predetermined component finely pulverized in advance is kneaded to adjust the component of the raw material powder.

(3) 粉末スクラップを還元剤と共に還元する際に、所定成分となるような金属成分を添加して拡散合金化により所定成分の合金粉末を形成させる。   (3) When reducing powder scrap together with a reducing agent, a metal component that becomes a predetermined component is added and alloy powder of the predetermined component is formed by diffusion alloying.

これらの方法のなかで、(1) 、(2) の方法は、添加合金粉末の別途作製が必須となり、高コスト化の要因となる。(3) の方法は、安価な酸化物粉末などの形態で直接に脱酸、合金化できるため、低コストが期待できる。ところが、(3) の方法では、直接還元法を用いる場合には、前述と同様に高炭素スクラップを適用した場合に脱炭が行われないという問題と、還元剤として用いたCaが残留するという問題がある。   Among these methods, the methods (1) and (2) require the additional alloy powder to be separately prepared, which causes an increase in cost. Since the method (3) can be directly deoxidized and alloyed in the form of an inexpensive oxide powder or the like, low cost can be expected. However, in the method (3), when the direct reduction method is used, the problem that the decarburization is not performed when the high carbon scrap is applied as described above, and the Ca used as the reducing agent remains. There's a problem.

ところで、希土類磁石の粉末スクラップの直接還元中の脱炭については、金属Caを還元剤として、脱酸のみならず脱炭も同時に行う方法が、特許文献１および特許文献２に提案されている。   By the way, for decarburization during direct reduction of powder scrap of rare earth magnets, Patent Document 1 and Patent Document 2 propose a method of simultaneously performing decarburization as well as deoxidation using Ca as a reducing agent.

しかし、これらの方法では十分な脱炭は行えない。なぜなら、熱力学的にはＲ炭化物の方がCaC2より安定であり(NdC2+Ca→Nd+CaC2 ΔG=34.548kcal (1000℃))、Ｒ炭化物からCaC2を生成させて炭素を除去することは困難である。 However, these methods cannot perform sufficient decarburization. This is because the thermodynamic stable than it is CaC 2 of R carbide (NdC 2 + Ca → Nd + CaC 2 ΔG = 34.548kcal (1000 ℃)), remove carbon by generating a CaC 2 from R carbide It is difficult to do.

従って、炭素量の高い希土類磁石の粉末スクラップの脱炭を含めた工業的な再生方法は確立していないのが現状である。   Therefore, at present, an industrial regeneration method including decarburization of powder scrap of a rare earth magnet having a high carbon content has not been established.

Ca残留については、直接還元時に還元剤、例えば金属Caの一部が希土類磁石合金中に固溶 (500ppm以上) することが知られており、そのうち70％は希土類粒界相に存在するとされている。このため、単なる物理洗浄では除去できない。この固溶Caは、磁石製造の焼成工程における炉体汚染 (蒸発Caの付着) のみならず、製品として長期間使用した場合の表面錆 (防錆メッキ下部にピット錆形成) が発生する恐れがあり、原料粉末として用いる場合には、100ppm以下まで残留Caを低減する必要がある。
特開昭58−73731 号公報 特開昭58-136728 号公報 Regarding Ca residue, it is known that a reducing agent, for example, a part of metallic Ca, dissolves in the rare earth magnet alloy (500 ppm or more) during direct reduction, 70% of which is considered to exist in the rare earth grain boundary phase. Yes. For this reason, it cannot be removed by simple physical cleaning. This solute Ca may cause not only furnace body contamination (adhesion of evaporated Ca) in the firing process of magnet production, but also surface rust (pit rust formation under the antirust plating) when used for a long time as a product. When used as a raw material powder, it is necessary to reduce residual Ca to 100 ppm or less.
JP 58-73731 A JP 58-136728 A

本発明は、希土類磁石の粉末スクラップを、酸素存在下の雰囲気中で、700 ℃〜1200℃の温度で１〜10時間加熱する酸化脱炭処理を行い、得られた脱炭粉末を好ましくはさらに粉砕後、Ca系還元剤と、必要により成分調整用の粉末 (希土類酸化物粉末および／または他の金属粉末) とを添加、混練し、次いで加熱脱酸処理を行って脱炭脱酸混合物とし、この脱炭脱酸混合物を純水デカンテーションにより１回または複数回洗浄してCa系副生成物の低減処理を行った後、減圧熱処理によって固溶Ca分を蒸発除去し、最後に所定粒度に微粉砕することを特徴とする希土類磁石粉末の製造法である。   The present invention performs an oxidative decarburization treatment in which a rare earth magnet powder scrap is heated at a temperature of 700 ° C. to 1200 ° C. for 1 to 10 hours in an atmosphere in the presence of oxygen, and the obtained decarburized powder is preferably further After pulverization, a Ca-based reducing agent and, if necessary, powder for adjusting the ingredients (rare earth oxide powder and / or other metal powder) are added and kneaded, and then heat deoxidation treatment is performed to obtain a decarburized deoxidized mixture After this decarburization deoxidation mixture is washed once or multiple times with pure water decantation to reduce Ca-based by-products, the solid solution Ca is evaporated and removed by heat treatment under reduced pressure, and finally the predetermined particle size is obtained. It is a method for producing a rare earth magnet powder, characterized by being finely pulverized.

本発明における酸化脱炭処理については、酸素存在下の雰囲気が酸素分圧140Pa 以下の酸素含有雰囲気であるが、あるいは、酸化脱炭処理を酸素分圧が140Pa を超える酸素存在下の雰囲気で行う場合には、水素還元を付加することが必要である。   As for the oxidative decarburization treatment in the present invention, the atmosphere in the presence of oxygen is an oxygen-containing atmosphere having an oxygen partial pressure of 140 Pa or less, or the oxidative decarburization treatment is performed in an atmosphere in the presence of oxygen having an oxygen partial pressure exceeding 140 Pa. In some cases it is necessary to add hydrogen reduction.

また、本発明における脱酸処理は、不活性ガス中で加熱する直接還元法により行われることが望ましい。   Further, the deoxidation treatment in the present invention is desirably performed by a direct reduction method in which heating is performed in an inert gas.

本発明における固溶Ca分の蒸発除去は、温度900 ℃以上で10Pa以下の真空度において0.5 時間以上加熱することにより行う。   The evaporative removal of the solid solution Ca in the present invention is performed by heating at a temperature of 900 ° C. or higher and a vacuum of 10 Pa or lower for 0.5 hour or longer.

また、本発明における還元粉末の微粉砕は気流粉砕 (ジェットミル粉砕) で行うことが望ましい。   Further, it is desirable that fine grinding of the reduced powder in the present invention is performed by airflow grinding (jet mill grinding).

さらに、本発明に係る希土類磁石の原料粉の製造法では、希土類磁石が、Ｒ-Fe-Ｂ系合金 (Ｒは、Nd,Pr,Dy,Ho,Tbの少なくとも１種を主成分とする希土類金属) からなることが望ましい。   Furthermore, in the method for producing a raw material powder for a rare earth magnet according to the present invention, the rare earth magnet is an R—Fe—B alloy (R is a rare earth mainly comprising at least one of Nd, Pr, Dy, Ho, and Tb. (Metal) is desirable.

本発明によれば、従来、低炭素化が困難であった希土類磁石の粉末スクラップを酸素分圧の制御により低コストで酸化脱炭し、さらに直接還元によって脱酸および必要により成分調整することで低炭素化および低酸素化が可能となった。さらに減圧熱処理によって固溶Caを除去することで、不純物が少なく従来のバージン合金粉末に比べて遜色ない希土類合金粗粉末を得ることができる。続いて、上記粗粉末を既存の粉砕方法により単独で微粉砕、あるいはバージン合金粉末と混練して微粉砕することにより良質な再生プレス原料として希土類磁石を製造することが可能となり、希土類金属の有効活用、省資源化に極めて効果があるものである。   According to the present invention, it is possible to oxidize and decarburize rare earth magnet powder scrap, which has conventionally been difficult to achieve low carbonization, at low cost by controlling the oxygen partial pressure, and further to deoxidize by direct reduction and adjust the components as necessary. Low carbon and low oxygen became possible. Further, by removing solid solution Ca by reduced pressure heat treatment, it is possible to obtain a rare earth alloy coarse powder that has few impurities and is inferior to conventional virgin alloy powder. Subsequently, the above coarse powder can be finely pulverized by an existing pulverization method alone, or kneaded with virgin alloy powder and pulverized to produce a rare earth magnet as a high-quality recycled press raw material. It is extremely effective for utilization and resource saving.

次に、本発明に係る希土類磁石の原料粉末の製造法の実施態様を詳述する。以下の説明では、希土類磁石がＲ-Fe-Ｂ系希土類磁石である場合を例とするが、本発明はＲ-Fe-Ｂ系希土類磁石に限定されず、例えば、Sm-Co 系やSm-Fe-N 系の磁石スクラップ等についても適用されることは本明細書の記載からも当業者には容易に理解されるところである。   Next, an embodiment of the method for producing the raw material powder for the rare earth magnet according to the present invention will be described in detail. In the following description, the case where the rare earth magnet is an R—Fe—B rare earth magnet is taken as an example. However, the present invention is not limited to the R—Fe—B rare earth magnet, and examples thereof include Sm—Co and Sm— Those skilled in the art can easily understand that the present invention is applicable to Fe-N-based magnet scraps and the like.

本発明は、 (炭素を含む) Ｒ-Fe-Ｂ系希土類磁石の粉末スクラップに、 (1)酸化脱炭工程、 (2)必要により成分調整を含む脱酸工程、 (3)Ca低減のための洗浄処理を行う洗浄工程、 (4)固溶Ca低減のために真空下での熱処理によりＲ-Fe-Ｂ系希土類磁石用原料となる再生合金粗粉末とする真空処理工程、 (5)微粉砕後、所要粒度に分級して希土類磁石原料粉末とする粉砕工程から構成される。以下に各工程について説明する。   The present invention includes (1) an oxidative decarburization step, (2) a deoxidation step including component adjustment as necessary, (3) for reducing Ca (including carbon) R-Fe-B rare earth magnet powder scrap (4) Vacuum treatment step to obtain a regenerated alloy coarse powder as a raw material for R-Fe-B rare earth magnets by heat treatment under vacuum to reduce solid solution Ca, (5) Fine After the pulverization, it is composed of a pulverization step that classifies to the required particle size to make the rare earth magnet raw material powder. Each step will be described below.

(1)酸化脱炭工程:
希土類磁石中の粒界相に存在するＲ炭化物は、1000℃程度の高温で熱処理すると、酸素によって脱炭 (酸化脱炭) される。 (1) Oxidation decarburization process:
The R carbides present in the grain boundary phase in the rare earth magnet are decarburized (oxidative decarburization) by oxygen when heat-treated at a high temperature of about 1000 ° C.

例えば、RC2 で示される組成のＲ炭化物の酸化脱炭は、下記の式(1) および(2) の連鎖反応によって起こり、R2O3で示される希土類酸化物が生成する。 For example, the oxidative decarburization of R carbide having a composition represented by RC 2 occurs by a chain reaction of the following formulas (1) and (2) to produce a rare earth oxide represented by R 2 O 3 .

2RC2+3.5O2(g) →R2O3＋４CO(g) ・・・(1)
ΔG ＝−440kcal(1000℃)
2RC2+5.5O2(g) →R2O3＋４CO2(g)・・・(2)
ΔG ＝−610kcal(1000℃)
また、フリーカーボンについても下記の式(3) で示される酸化脱炭が行われる。 2RC 2 + 3.5O 2 (g) → R 2 O 3 + 4CO (g) (1)
ΔG = -440kcal (1000 ° C)
2RC 2 + 5.5O 2 (g) → R 2 O 3 + 4CO 2 (g) (2)
ΔG = −610kcal (1000 ° C)
Also, free carbon is subjected to oxidative decarburization represented by the following formula (3).

C+20(g) →CO2(g)・・・(3)
ΔG ＝−176kcal(1000℃) .
粉末スクラップの場合は、比表面積が大きく、また、フリーカーボンについても粉末状で存在しているため、上式の反応は微量の酸素が存在すれば容易に進行する。逆に雰囲気中の酸素濃度が高すぎる場合、例えば大気雰囲気中の場合には過剰酸化となり、主相が熱分解され、一部が酸化鉄となる。この酸化鉄は水素雰囲気あるいは水素水蒸気雰囲気によって熱処理を行うことで還元される。酸化鉄の存在は、続く脱酸処理において、還元剤 (例えば金属Ca) の添加量を増大させるばかりでなく、酸化鉄の還元反応において融鉄を形成するほどの大きな反応熱を発生するため、処理量の如何によらず、容器損傷、還元融着による歩留劣化、さらには炉体損傷等の事態を招く恐れがある。すなわち、より低コストで酸化鉄の生成を極小化するために、雰囲気中の酸素分圧を140Pa 以下で酸化脱炭を行うことが望ましい。 C + 20 (g) → CO 2 (g) (3)
ΔG = -176kcal (1000 ° C).
In the case of powder scrap, since the specific surface area is large and free carbon is also present in powder form, the above reaction proceeds easily in the presence of a small amount of oxygen. On the other hand, when the oxygen concentration in the atmosphere is too high, for example, in the air atmosphere, excessive oxidation occurs, the main phase is thermally decomposed, and part of it becomes iron oxide. This iron oxide is reduced by heat treatment in a hydrogen atmosphere or a hydrogen steam atmosphere. The presence of iron oxide not only increases the amount of reducing agent (e.g., metallic Ca) added in the subsequent deoxidation process, but also generates reaction heat that is large enough to form molten iron in the iron oxide reduction reaction. Regardless of the amount of processing, there is a risk of causing damage to the container, yield deterioration due to reduction fusion, and further damage to the furnace body. That is, in order to minimize the production of iron oxide at a lower cost, it is desirable to perform oxidative decarburization at an oxygen partial pressure in the atmosphere of 140 Pa or less.

140Pa 以下という酸素分圧は、圧力が667Pa 以下であるため、減圧によって得ることが経済的であるが、不活性ガスと酸素または空気を混合した混合ガスを用いても良い。例えば、１質量％の炭素を有する粉末スクラップであれば、酸化脱炭に必要な酸素量はわずかであり、工業的な熱処理炉で実現可能な0.01Pa (酸素分圧で0.002Pa)で十分である。つまり酸素分圧の下限は特に制限されない。特に大気減圧雰囲気で脱炭する場合の好ましい圧力は、0.01Pa以上１Pa以下 (酸素分圧では、0.002Pa 以上0.2Pa 以下) である。なお、研削スラッジのような油や防錆剤を含むスクラップの場合には、過剰な酸素雰囲気下にて酸化脱炭する方が熱処理炉のメンテナンスを考えれば工業的には低コストとなる場合がある。このような場合には、酸素分圧が140Pa を超える雰囲気下の脱炭に続いて脱酸工程の前に、水素雰囲気下で酸化鉄の還元をあらかじめ行うことが有効である。   The oxygen partial pressure of 140 Pa or less is economical because it is 667 Pa or less, and it is economical to obtain it by pressure reduction. However, a mixed gas in which an inert gas and oxygen or air are mixed may be used. For example, in the case of powder scrap having 1% by mass of carbon, the amount of oxygen required for oxidative decarburization is small, and 0.01 Pa (0.002 Pa in oxygen partial pressure) that can be realized in an industrial heat treatment furnace is sufficient. is there. That is, the lower limit of the oxygen partial pressure is not particularly limited. In particular, a preferable pressure when decarburizing in an atmospheric reduced pressure atmosphere is 0.01 Pa or more and 1 Pa or less (in oxygen partial pressure, 0.002 Pa or more and 0.2 Pa or less). In addition, in the case of scraps containing oil and rust preventives such as grinding sludge, it may be industrially cheaper to oxidatively decarburize in an excessive oxygen atmosphere considering the maintenance of the heat treatment furnace. is there. In such a case, it is effective to reduce iron oxide in a hydrogen atmosphere in advance before the deoxidation step following decarburization in an atmosphere where the oxygen partial pressure exceeds 140 Pa.

前述した酸化脱炭には、製造工程で発生する粉末スクラップのみならず、急冷希土類合金スクラップ、固形スクラップ、メッキ済スクラップ、あるいは電気機器から回収された使用済み希土類磁石にも適用できる。メッキ済スクラップのみ予めショットブラストでメッキ除去を必要とするが、他のスクラップでは、水素化粉砕させて、機械粉砕 (例えばディスクミル、ボールミル等) すれば良く、あるいは、機械粉砕のみでも良い。粉砕粒度は特に限定されないが、平均粒径が２〜10μm であれば充分であり、過剰な微粉砕は発火等の要因となり避けるべきである。   The oxidative decarburization described above can be applied not only to powder scrap generated in the manufacturing process, but also to quenched rare earth alloy scraps, solid scraps, plated scraps, or used rare earth magnets recovered from electrical equipment. Only plated scraps need to be removed by shot blasting in advance, but other scraps may be hydro-pulverized and mechanically pulverized (eg, disk mill, ball mill, etc.), or only mechanically pulverized. The pulverized particle size is not particularly limited, but it is sufficient if the average particle size is 2 to 10 μm, and excessive fine pulverization should be avoided due to factors such as ignition.

スラリー状のスクラップについては、脱炭前にストレーナ等で異物除去および濾過脱水等を施してケーキ状にした後に、酸化脱炭させれば良い。   The slurry-like scrap may be oxidatively decarburized after debris removal, filtration dehydration, and the like with a strainer or the like to form a cake before decarburization.

熱処理温度、熱処理時間についてはそれぞれ、700 ℃以上1200℃以下、１時間以上10時間以下とする。   The heat treatment temperature and the heat treatment time are 700 ° C. to 1200 ° C., 1 hour to 10 hours, respectively.

熱処理温度が700 ℃未満では、酸化脱炭反応が充分に進行せず、単なる乾燥処理となるため、取り出し時の発火等の要因となる。熱処理温度が1200℃超では、脱炭は充分であるが、低融点の希土類粒界相が、容器へ垂れ落ちる現象が発生して回収歩留低下に繋がる。   If the heat treatment temperature is less than 700 ° C., the oxidative decarburization reaction does not proceed sufficiently, and it becomes a simple drying process, which may cause ignition during removal. When the heat treatment temperature is higher than 1200 ° C., decarburization is sufficient, but a phenomenon that the low melting point rare earth grain boundary phase hangs down to the container occurs, leading to a decrease in recovery yield.

また、熱処理時間が１時間より短いと、熱処理温度を1200℃と高くしても、希土類粒界相の脱炭反応は充分に進行しない。また、熱処理温度が10時間超では、脱炭性は良好だが、操炉コストが大きくなり、また熱処理温度を700 ℃と低くしても、粒子同士の溶着が進行し、粗大焼結粒子となるため、続く脱酸処理において粗大焼結粒子の内部脱酸が不充分となり脱酸性が低下する。   If the heat treatment time is shorter than 1 hour, the decarburization reaction of the rare earth grain boundary phase does not proceed sufficiently even if the heat treatment temperature is increased to 1200 ° C. In addition, when the heat treatment temperature exceeds 10 hours, decarburization is good, but the operating cost increases, and even when the heat treatment temperature is lowered to 700 ° C, the welding of the particles proceeds, resulting in coarse sintered particles. Therefore, in the subsequent deoxidation treatment, the internal deoxidation of the coarse sintered particles becomes insufficient, and the deacidification is lowered.

(2)必要により成分調整を含む脱酸工程:
上述した酸化脱炭処理により得られるＲ-Fe-Ｂ系脱炭スクラップに、還元剤として金属Ca、そして必要により、成分調整用として希土類酸化物粉末 (例えば Nd2O3、Dy2O3)およびＢ合金粉末 (例えばFeB)、その他の金属粉末を添加、混練し、不活性ガス中で加熱する直接還元法を用いて、脱酸処理を行う。このときの脱酸法は、例えばステンレス鋼製等の還元容器に、脱炭スクラップ、金属Ca、所定量の希土類酸化物粉末 (例えばNd2 O3粉末、 Dy2O3粉末) 、Ｂ合金粉末 (例えばFeB)、その他の金属粉末 (例えばCo粉末) を入れて大気圧程度の不活性雰囲気下 (例えばAr) で還元剤が溶融する温度まで加熱して還元 (固相拡散還元) させる。この場合、Ca低減洗浄処理時の崩壊性を容易にするために、フラックスを脱炭スクラップと予備混練しておくことが好ましい。 (2) Deoxidation process including component adjustment if necessary:
R-Fe-B decarburized scrap obtained by the above-mentioned oxidative decarburization treatment, metal Ca as a reducing agent, and, if necessary, rare earth oxide powder (for example, Nd 2 O 3 , Dy 2 O 3 ) for component adjustment And B alloy powder (for example, FeB) and other metal powder are added, kneaded, and deoxidized using a direct reduction method of heating in an inert gas. In this case, the deoxidation method includes, for example, decarburization scrap, metal Ca, a predetermined amount of rare earth oxide powder (for example, Nd 2 O 3 powder, Dy 2 O 3 powder), B alloy powder in a reduction vessel made of stainless steel or the like. (For example, FeB) and other metal powder (for example, Co powder) are added and heated to a temperature at which the reducing agent melts in an inert atmosphere (for example, Ar) at atmospheric pressure to reduce (solid phase diffusion reduction). In this case, it is preferable to pre-knead the flux with decarburized scrap in order to facilitate disintegration during the Ca reduction cleaning process.

還元剤としては、Ｒ酸化物を脱酸できるアルカリ土類金属ならば特に限定されないが、工業的には、取り扱いに優れる粒状金属Caが好ましい。   The reducing agent is not particularly limited as long as it is an alkaline earth metal capable of deoxidizing R oxide, but industrially, granular metal Ca that is excellent in handling is preferable.

添加量としては、溶融時の蒸発分および脱炭スクラップ中の希土類酸化物の還元に必要な反応当量の1.0 〜2.0 倍程度とすることが望ましい。また、上記フラックスについては、還元剤として金属Caを用いる場合、不揮発性の無水CaCl2 を用いることが好ましく、添加量は脱炭スクラップの３〜20質量％程度が良い。還元反応に必要な加熱温度は、金属Caの場合、839 ℃以上であり、加熱時間は１〜５時間程度とすることが好ましい。冷却条件は特に限定されない。加熱温度が1200℃以上では、金属Caの蒸発量が多くなるため、実用上は加熱温度を1200℃以下とすべきである。 The amount of addition is preferably about 1.0 to 2.0 times the reaction equivalent necessary for the evaporation during melting and the reduction of the rare earth oxide in the decarburized scrap. As for the flux, When a metal Ca as the reducing agent, it is preferable to use anhydrous CaCl 2 in the non-volatile, the amount should preferably be about 3 to 20 wt% of the decarburization scrap. In the case of metallic Ca, the heating temperature required for the reduction reaction is 839 ° C. or higher, and the heating time is preferably about 1 to 5 hours. The cooling conditions are not particularly limited. When the heating temperature is 1200 ° C. or higher, the amount of evaporation of metallic Ca increases, so the heating temperature should be 1200 ° C. or lower for practical use.

(3)Ca低減のための洗浄工程:
続いて、上述の脱酸生成混合物を純水によって１回または複数回のデカンテーション洗浄を行って副生成物CaO の低減処理を行い、再生粗粉末を製造する。本実施形態では、還元反応後に冷却した脱炭・脱酸混合物を反応容器から取り出し、例えば比抵抗が 15MΩ・cm/25 ℃程度の純水で繰り返し洗浄を行う。 (3) Cleaning process to reduce Ca:
Subsequently, the deoxidation product mixture described above is subjected to decantation washing one or more times with pure water to reduce the by-product CaO to produce a regenerated coarse powder. In this embodiment, the decarburized / deoxidized mixture cooled after the reduction reaction is taken out of the reaction vessel, and repeatedly washed with pure water having a specific resistance of about 15 MΩ · cm / 25 ° C., for example.

純水洗浄によって、脱炭脱酸混合物中の未反応脱酸剤 (例えば金属Ca) や副生成物 (例えばCaO)は、水中でCa(OH)2 となり、デカンテーション洗浄によってCa成分が除去され、還元された粉末スラリーを得ることができる。なお、この場合に消和反応[Ca(OH)2形成時の発熱反応] による還元粉末の再酸化を防ぐために、脱炭脱酸混合物を粗砕して投入し、さらに低水温とすることが望ましい。また、デカンテーション洗浄の際にCa成分の除去性を向上させるために適当な攪拌装置を用いるとより好ましい。デカンテーション洗浄の終点としては、溶液のpH＝10以下となるまで洗浄を繰り返すことが望ましい。 Unreacted deoxidizer (e.g., metallic Ca) and by-products (e.g., CaO) in the decarburized and deoxidized mixture are converted to Ca (OH) 2 in water by the pure water cleaning, and the Ca component is removed by decantation cleaning. A reduced powder slurry can be obtained. In this case, in order to prevent reoxidation of the reduced powder due to the exothermic reaction [exothermic reaction during the formation of Ca (OH) 2 ], the decarburized and deoxidized mixture is roughly crushed and further cooled to a low water temperature. desirable. In addition, it is more preferable to use an appropriate stirring device in order to improve the removability of the Ca component during decantation cleaning. As the end point of decantation washing, it is desirable to repeat washing until the pH of the solution is 10 or less.

こうして得られた還元粉末スラリーを、濾過脱水して、室温程度で減圧乾燥することで再生粗粉末を得ることができる。   The reduced powder slurry thus obtained is filtered and dehydrated and dried under reduced pressure at about room temperature to obtain a regenerated coarse powder.

(4)固溶Ca低減のため加熱を行う真空処理工程：
直接還元による再生粉末中の固溶Caを除去するために、減圧熱処理を行う。Ca融液は希土類磁石の粒界相に優先的に固溶することが知られている。この固溶Caを粒界相から除去するにはCaの蒸気圧以下の真空度で熱処理を行えばよい。この条件として種々の検討から、熱処理温度は900 ℃以上、熱処理時間0.5 時間以上、真空度10Pa以下が必要であることを知見した。熱処理温度が900 ℃未満の場合は、粒界相の活性化が不充分となり固溶Caの蒸発が困難となる。また、900 ℃以上ではCaの蒸気圧が増加するため蒸発しやすいが、熱処理温度を上げすぎると粒界相が優先的に再酸化されやすい。熱処理時間については、0.5 時間未満になるとCaの蒸発が不十分となるため、0.5 時間以上を必要とする。 (4) Vacuum treatment process for heating to reduce dissolved Ca:
In order to remove solute Ca in the regenerated powder by direct reduction, a heat treatment under reduced pressure is performed. It is known that Ca melt preferentially dissolves in the grain boundary phase of rare earth magnets. In order to remove this solid solution Ca from the grain boundary phase, heat treatment may be performed at a vacuum level lower than the vapor pressure of Ca. As a result of various studies, it has been found that the heat treatment temperature is required to be 900 ° C. or higher, the heat treatment time is 0.5 hours or longer, and the degree of vacuum is 10 Pa or lower. When the heat treatment temperature is less than 900 ° C., the activation of the grain boundary phase is insufficient and it becomes difficult to evaporate the solid solution Ca. At 900 ° C. or higher, the vapor pressure of Ca increases, so it tends to evaporate. However, if the heat treatment temperature is raised too much, the grain boundary phase is preferentially reoxidized. As for the heat treatment time, if it is less than 0.5 hours, the evaporation of Ca becomes insufficient, so 0.5 hours or more are required.

(5)所要粒度への粉砕工程：
上述のCa低減処理済みの再生粉末は、粒径数十μm の粗大粒子であるため、希土類磁石の原料粉末として利用するために、所要粒度への粉砕を行う。この場合、必要により成分再調整として、所定成分のバージン合金粉末を配合して粉砕しても良い。この粉砕には酸化および汚染を防止して、さらに所要粒度への分級装置を有する気流粉砕装置 (例えばジェットミル) を用いて不活性ガス中で、例えば窒素ガスを用いて粉砕することが望ましい。 (5) Grinding process to required particle size:
Since the above-mentioned regenerated powder after Ca reduction treatment is coarse particles having a particle size of several tens of μm, it is pulverized to a required particle size in order to be used as a raw material powder for a rare earth magnet. In this case, a virgin alloy powder of a predetermined component may be blended and pulverized as necessary for component readjustment. For this pulverization, it is desirable to prevent oxidization and contamination, and further pulverize in an inert gas, for example, using nitrogen gas, using an airflow pulverizer (for example, a jet mill) having a classification device to a required particle size.

さらに好ましくは、Ca低減処理済みの再生粉末を予め水素化粉砕および脱ガス処理をしておくと良い。水素は、希土類磁石の粒界相と優先的に反応し水素化物を形成することで粒界相の体積膨張を促し自然粉砕を引き起こす。水素化処理を行うことで続く気流粉砕による微粉砕性が大幅に改善されるのである。   More preferably, the regenerated powder that has been subjected to the Ca reduction treatment is preliminarily hydroground and degassed. Hydrogen preferentially reacts with the grain boundary phase of the rare earth magnet to form a hydride, thereby promoting the volume expansion of the grain boundary phase and causing natural pulverization. By performing the hydrogenation treatment, the fine pulverization property by the subsequent air pulverization is greatly improved.

水素化粉砕の条件としては、特に限定されないが、水素吸収性を向上させるために水素圧力0.2MPa (絶対圧) 以上で行うことが望ましい。   The conditions for the hydropulverization are not particularly limited, but it is desirable to carry out at a hydrogen pressure of 0.2 MPa (absolute pressure) or more in order to improve hydrogen absorption.

脱ガス処理は、長期保存に伴う酸化およびプレス成形体の酸化を防止するために必要である。脱ガス条件としては特に限定されないが、真空中またはAr雰囲気中で100 ℃以上に加熱し、0.5 時間以上の脱ガスを行うと良い。   The degassing treatment is necessary to prevent oxidation accompanying long-term storage and oxidation of the press-molded product. The degassing conditions are not particularly limited, but it is preferable to degas for 0.5 hours or more by heating to 100 ° C. or higher in a vacuum or Ar atmosphere.

このようにして得られた再生粉末の不純物は、バージン鋳造凝固インゴットもしくはバージン急冷凝固薄片から得られる粉末と同レベルまで低減されるため、この再生微粉末をプレス原料粉末として用いることにより、バージン原料と遜色ない希土類磁石を製造することができる。また、本発明にかかる再生微粉末は焼結型、ボンド型への適用が可能である。   Impurities in the regenerated powder thus obtained are reduced to the same level as the powder obtained from the virgin cast solidified ingot or the virgin rapidly solidified flakes. By using this regenerated fine powder as the press raw material powder, A rare earth magnet comparable to the above can be manufactured. The regenerated fine powder according to the present invention can be applied to a sintered mold and a bond mold.

以上から、本発明によりＲ-Fe-Ｂ系希土類磁石の製造工程または使用済み機器等から発生する希土類磁石の炭素量および酸素量が高い粉末スクラップを希土類磁石原料として安価に工業的規模で再生することが可能となるのである。   From the above, according to the present invention, powder scrap having a high carbon content and high oxygen content of rare earth magnets generated from the manufacturing process of R-Fe-B rare earth magnets or used equipment, etc. is recycled at low cost on an industrial scale as rare earth magnet raw materials. It becomes possible.

次に、実施例により、焼結希土類磁石の多様な製造工程で発生したスクラップの再生方法を例示する。以下の実施例および比較例において、「％」は特に指定のない限り、「質量％」である。使用した試料の測定方法を次にまとめて示す:
金属組成値および希土類量：ICP(プラズマ発光分光分析)
含水率: 大気加熱式含水率測定装置
炭素量、酸素量：LECO (赤外線吸収法)
平均粒径：通気式粒度計
エネルギー積：Ｂ−Ｈトレーサ Next, a method for recycling scrap generated in various manufacturing processes for sintered rare earth magnets will be described by way of example. In the following Examples and Comparative Examples, “%” is “% by mass” unless otherwise specified. The sample measurement method used is summarized below:
Metal composition value and rare earth content: ICP (plasma emission spectroscopy)
Moisture content: Air heating type moisture content measuring device Carbon content, oxygen content: LECO (infrared absorption method)
Average particle size: Ventilation type particle size meter Energy product: BH tracer

本例は、Nd-Fe-Ｂ系磁石の加工工程で発生した、スラリー状スクラップ(A) の再生処理を例示する。スラリーの金属組成値および含水率は次の通りであった：
スラリー状スクラップ(A) の金属組成
25.2％Nd-3.9％Dy-0.9％Ｂ-70 ％Fe、含水率：38％。 This example illustrates the regeneration processing of the slurry-like scrap (A) generated in the processing process of the Nd—Fe—B magnet. The metal composition values and moisture content of the slurry were as follows:
Metal composition of slurry scrap (A)
25.2% Nd-3.9% Dy-0.9% B-70% Fe, moisture content: 38%.

このスラリー状スクラップ(A) 50kgを、濾過脱水し、24時間の減圧乾燥を行い、約30kgの乾燥した粉末を得た。この粉末(A) の成分および平均粒径を表１に示す。炭素含量および酸素含量ともに極めて高い値であった。   50 kg of this slurry-like scrap (A) was filtered and dehydrated and dried under reduced pressure for 24 hours to obtain about 30 kg of dried powder. Table 1 shows the components and average particle size of the powder (A). Both the carbon content and the oxygen content were extremely high.

この粉末(A) ５kgづつをステンレス鋼製容器に入れ、雰囲気炉中で加熱処理を行って、酸化脱炭を行った。加熱処理条件は、昇温速度５℃/min、圧力0.05Pa (酸素分圧0.01Pa) および650Pa(酸素分圧130Pa)、加熱時間５時間、最高温度を700 ℃、950 ℃および1100℃とし、熱処理後はAr雰囲気中で炉冷を行い、６種類の粉末 (Al〜A6)(以下、脱炭粉末という) を得た。脱炭粉末性状 (炭素量、酸素量、希土類量) を表２に示す。酸素量は8.5 ％以上となり、炭素量は0.03％以下と大幅に低減していた。   Each 5 kg of this powder (A) was put into a stainless steel container and heat-treated in an atmospheric furnace to carry out oxidative decarburization. The heat treatment conditions were as follows: heating rate 5 ° C / min, pressure 0.05Pa (oxygen partial pressure 0.01Pa) and 650Pa (oxygen partial pressure 130Pa), heating time 5 hours, maximum temperature 700 ° C, 950 ° C and 1100 ° C, After the heat treatment, furnace cooling was performed in an Ar atmosphere to obtain six types of powders (Al to A6) (hereinafter referred to as decarburized powder). Table 2 shows the decarburized powder properties (carbon content, oxygen content, rare earth content). The oxygen content was 8.5% or more, and the carbon content was significantly reduced to 0.03% or less.

脱炭粉末 (Al〜A6) 各３kgを用いて、次のように直接還元法により脱酸、成分調整を行った。   Using 3 kg of decarburized powder (Al to A6), deoxidation and component adjustment were performed by the direct reduction method as follows.

脱酸剤には粒子径２〜７mmの純度99％粒状金属Ca用い、添加量はスクラップ中の酸素が全てCaO となるような脱酸当量を1.0 とした場合の1.5 倍とした。フラックスには純度95％の無水CaC12 を用い、脱炭粉末 (Al〜A6) に対して10％の量で添加した。さらに成分調整として純度99.9％、粒径７μm のNd2O3 粉末および純度99.9％、粒径７μm のDy2O3 粉末および粒径45μm 以下の19.9Ｂ-Fe 合金粉末を30.5％Nd-5.0％Dy-1.1％Ｂ-63.4％Feとなるように配合し充分に混練を行った。 As the deoxidizer, 99% granular metal Ca having a particle diameter of 2 to 7 mm was used, and the amount added was 1.5 times the deoxidation equivalent of 1.0 so that all the oxygen in the scrap was CaO. Flux used 95% pure anhydrous CaCl 2 in, was added in an amount of 10% relative to decarburization powder (Al~A6). In addition, Nd 2 O 3 powder with a purity of 99.9% and particle size of 7μm and Dy 2 O 3 powder with a purity of 99.9% and particle size of 7μm and 19.9B-Fe alloy powder with a particle size of 45μm or less were added as component adjustments to 30.5% Nd-5.0%. Dy-1.1% B-63.4% Fe was mixed and kneaded thoroughly.

得られた混合物をステンレス鋼製反応容器に入れ、Ar気流中で1000℃まで３時間かけて昇温し、５時間保持した後、室温まで冷却し、６種類の還元反応混合物、つまり脱炭・脱酸混合物を取り出し、５mm程度に粗砕した。   The obtained mixture was put into a stainless steel reaction vessel, heated to 1000 ° C. over 3 hours in an Ar stream, held for 5 hours, then cooled to room temperature, and six kinds of reduction reaction mixtures, namely decarburization / The deoxidized mixture was taken out and roughly crushed to about 5 mm.

粗砕した６種類の還元反応混合物各３kgを、15℃以下に冷却した、比抵抗15M Ω・cm/25 ℃の純水30リットルを用いて初期崩壊を行った。初期崩壊によるCa(OH)2 懸濁液 (未反応金属Caおよび副生成物CaO が水と反応した生成物) をデカンテーション洗浄 (再生希土類粉末を沈降分離、上澄液排出) の繰り返しによりスラリーがpH＝10以下になるまで行った。 Initial degradation was carried out using 30 liters of pure water having a specific resistance of 15 MΩ · cm / 25 ° C., which was cooled to 15 ° C. or less and 3 kg of each of the 6 kinds of roughly crushed reduction reaction mixtures. Slurry by repeated decantation washing of Ca (OH) 2 suspension (product obtained by reacting unreacted metal Ca and by-product CaO with water) by initial disintegration (regenerated rare earth powder separated by settling and discharging supernatant) Until pH = 10 or lower.

続いて上記スラリーを脱水濾過し、室温で減圧乾燥を24時間行った。   Subsequently, the slurry was dehydrated and filtered, and dried under reduced pressure at room temperature for 24 hours.

このようにして得られた６種類の脱炭・脱酸混合物、つまり還元粉末 (A7〜A12)２kgの成分と平均粒径を表３に示す。全てにおいて、希土類成分およびＢ量は、ほぼ目標成分通りであり、かつＣ＜0.03％、０＜0.4 ％の清浄な再生粉末であったが、残留Caについては全て0.05％以上であった。また全てについてＸ線回折による相同定の結果、本系希土類磁石の特徴である主相(Nd2Fe14Ｂ) のみで構成される希土類磁石合金粉末であることが判明した。 Table 3 shows the components and average particle diameters of the 6 types of decarburized / deoxidized mixtures thus obtained, that is, 2 kg of reduced powder (A7 to A12). In all cases, the rare earth component and the B content were almost the same as the target components and were clean regenerated powders with C <0.03% and 0 <0.4%, but the residual Ca was all 0.05% or more. As a result of phase identification by X-ray diffraction for all, it was found to be a rare earth magnet alloy powder composed only of the main phase (Nd 2 Fe 14 B), which is a feature of the present rare earth magnet.

上記で得られた６種類の還元粉末各２kgを、ステンレス鋼製容器に入れて、９Paの真空度で910 ℃まで１時間かけて昇温し、0.5 時間保持してから室温まで冷却して固溶Ca除去を行った。このようにして得られた６種類の熱処理粉末(A13〜A18)のCa量を表４に示す。全てにおいてCa＜0.01％まで低減されていることを確認した。   2 kg of each of the 6 kinds of reduced powders obtained above are put in a stainless steel container, heated to 910 ° C. over 1 hour at a vacuum of 9 Pa, held for 0.5 hours, then cooled to room temperature and solidified. Dissolved Ca was removed. Table 4 shows the Ca content of the six types of heat-treated powders (A13 to A18) thus obtained. It was confirmed that Ca was reduced to <0.01% in all cases.

続いて、上記の６種類の熱処理粉末(A13〜A18)各２kgをステンレス鋼製密閉容器に装入し、真空引き後、水素を導入し圧力を0.3MPaとして常温で水素化粉砕を実施した。その後、真空炉にて１×10-2Paで温度500 ℃で１時間の脱水素処理を行い、Ar雰囲気で冷却を行った。 Subsequently, 2 kg of each of the above 6 kinds of heat treated powders (A13 to A18) were charged into a stainless steel sealed container, and after evacuation, hydrogen was introduced and hydrogen pulverization was performed at room temperature at a pressure of 0.3 MPa. Thereafter, dehydrogenation treatment was performed in a vacuum furnace at 1 × 10 −2 Pa at a temperature of 500 ° C. for 1 hour, and cooling was performed in an Ar atmosphere.

これらの６種類の粗粉砕粉末各２kgを、ステアリン酸亜鉛0.6gとともに十分に混練したのち、N2ガスを用い、圧力７kg/cm2でジェットミルにより微粉末(A19〜A24)を得た。表５にこれら微粉末の成分および平均粒径を示す。全てにおいてＣ＜0.08％、Ｏ＜0.7 ％、Ca＜0.01％と不純物量の少ない清浄な品質のものであった。 After 2 kg of each of these 6 kinds of coarsely pulverized powders were sufficiently kneaded with 0.6 g of zinc stearate, fine powders (A19 to A24) were obtained by a jet mill using N 2 gas at a pressure of 7 kg / cm 2 . Table 5 shows the components and average particle size of these fine powders. In all cases, C <0.08%, O <0.7%, Ca <0.01% and clean quality with few impurities.

得られた６種類の微粉末を用いて、磁界796kA/m 中で配向させながら1.5kg/cm2 の成形圧力で磁場成形を行い10個の圧粉体を得た。続いて真空中で1070℃、３時間で焼結を行い、500 ℃、１時間の熱処理を施した後に、着磁を行い永久磁石とした。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。 Using the obtained 6 kinds of fine powders, magnetic field molding was performed at a molding pressure of 1.5 kg / cm 2 while orienting in a magnetic field of 796 kA / m 2 to obtain 10 compacts. Subsequently, sintering was performed in vacuum at 1070 ° C. for 3 hours, and after heat treatment at 500 ° C. for 1 hour, magnetization was performed to obtain a permanent magnet. These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

本例は、プレス成形工程で発生した、圧粉成形不良品からなるスクラップの再生処理例である。この圧粉成形不良品(B) の組成、形状は次の通りであった：
圧粉成形不良品(B) の組成：30.4％Nd-1.0％Dy-1.1％Ｂ-67.5 ％Fe
圧粉成形不良品(B) の形状：直径約30mm、高さ約10mmの中実円筒品。 This example is an example of a recycling process for scrap made of defective compacting products generated in the press molding process. The composition and shape of this defective green compact (B) were as follows:
Composition of defective green compact (B): 30.4% Nd-1.0% Dy-1.1% B-67.5% Fe
Shape of defective green compact (B): Solid cylindrical product with a diameter of about 30mm and a height of about 10mm.

この圧粉成形不良品(B) 20kgを、ボールミルにより、Ar雰囲気中で軽粉砕して、粉末(B) を得た。粉末(B) の成分および粒子径を表１に示す。スラリー状スクラップ(A) に比べて、炭素量、酸素量とも少ないことがわかる。   20 kg of the compacted green compact (B) was lightly pulverized with a ball mill in an Ar atmosphere to obtain a powder (B). Table 1 shows the components and particle size of the powder (B). It can be seen that both the amount of carbon and the amount of oxygen are small compared to the slurry-like scrap (A).

この粉末(B) を用いて、実施例１と全く同様に酸化脱炭を行った。得られた脱炭粉末 (B1〜B6) 性状を表２に示す。酸素量は２〜３倍に増大し、炭素量は0.03％以下であった。   Using this powder (B), oxidative decarburization was performed in exactly the same manner as in Example 1. Table 2 shows the properties of the obtained decarburized powder (B1 to B6). The amount of oxygen increased 2-3 times, and the amount of carbon was 0.03% or less.

脱炭粉末 (Bl〜B6) 各３kgを用いて、目標成分を31.0％Nd-5.0％Dy-1.1Ｂ-62.9 ％Feと変更した以外は実施例１と全く同様にして直接還元法による脱酸、成分調整を行い、還元反応混合物、つまり脱炭・脱酸混合物を得た。続いて実施例１と全く同様に純水洗浄、乾燥を行い、還元粉末 (B7〜B12)を得た。表３に示すように、実施例１と同様にCa残留を除いては高品位な希土類合金粉末であることが認められた。   Deoxidization powder by direct reduction method in exactly the same way as in Example 1 except that 3kg each of decarburized powder (Bl to B6) and the target component was changed to 31.0% Nd-5.0% Dy-1.1B-62.9% Fe The components were adjusted to obtain a reduction reaction mixture, that is, a decarburized / deoxidized mixture. Subsequently, pure water was washed and dried in the same manner as in Example 1 to obtain reduced powders (B7 to B12). As shown in Table 3, in the same manner as in Example 1, it was recognized that the powder was a high-quality rare earth alloy powder except for Ca residue.

上記の６種類の還元粉末各２kgを、実施例１と全く同様に固溶Ca除去を行い、６種類の熱処理粉末(B13〜B18)を得た。このようにして得られた６種類の熱処理粉末(B13〜BL8)の成分Ca量を表４に示す。全てにおいて実施例１と同様にCaは0.01％未満まで低減されていた。   2 kg of each of the above 6 types of reduced powders was subjected to removal of solid solution Ca in the same manner as in Example 1 to obtain 6 types of heat treated powders (B13 to B18). Table 4 shows the component Ca content of the six types of heat-treated powders (B13 to BL8) thus obtained. In all, as in Example 1, Ca was reduced to less than 0.01%.

続いて６種類の熱処理粉末(B13〜B18)を実施例１と全く同様にジェットミルにより粉砕し微粉末(B19〜B24)を得た。表５にこれら微粉末の成分と平均粒径を示す。実施例１と同様に不純物の少ない良好な品質であった。   Subsequently, six kinds of heat-treated powders (B13 to B18) were pulverized by a jet mill in the same manner as in Example 1 to obtain fine powders (B19 to B24). Table 5 shows the components and average particle diameter of these fine powders. Like Example 1, it was a good quality with few impurities.

得られた６種類の微粉末を用いて、実施例１と同様に永久磁石を作製した。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。   A permanent magnet was produced in the same manner as in Example 1 by using the obtained 6 kinds of fine powders. These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

本例は、焼結工程で発生した、焼結不良品からなるスクラップの再生処理を例示する。本例で用いた焼結不良品(C) の組成、形状は次の通りであった:
焼結不良品(C) の組成：29.9％Nd-1.0％Dy-1.1％Ｂ-68 ％Fe
焼結不良品(C) の形状：直径約30mm、高さ約30mmの中実円筒品。 This example exemplifies a recycling process for scraps made of defective sintered products generated in the sintering process. The composition and shape of the poorly sintered product (C) used in this example were as follows:
Composition of defective sintered product (C): 29.9% Nd-1.0% Dy-1.1% B-68% Fe
Shape of defective sintered product (C): Solid cylindrical product with a diameter of about 30 mm and a height of about 30 mm.

この焼結不良品(C) 20kgをステンレス鋼製密閉容器に装入し、真空引き後、水素を導入し圧力を0.3MPaとして常温で水素化粉砕を行った。その後、真空炉で１×10-2Pa以下で温度300 ℃で１時間の脱水素処理を行い、Arガスで冷却を行った。続いてディスクミルによりAr雰囲気中で粉砕を行い、粉末(C) を得た。粉末(C) の成分と平均粒径を表１に示す。 20 kg of this poorly sintered product (C) was placed in a stainless steel sealed container, and after evacuation, hydrogen was introduced and hydrogen pulverization was performed at room temperature at a pressure of 0.3 MPa. After that, dehydrogenation treatment was performed in a vacuum furnace at 1 × 10 −2 Pa or less at a temperature of 300 ° C. for 1 hour, and then cooled with Ar gas. Subsequently, it was pulverized in an Ar atmosphere by a disk mill to obtain a powder (C). Table 1 shows the components and average particle diameter of the powder (C).

この粉末(C) を用いて、実施例１と全く同様に酸化脱炭を行った。得られた脱炭粉末 (Cl〜C6) 性状を表２に示す。実施例１と同様に酸素量が増加し、炭素量は0.03％以下であった。   Using this powder (C), oxidative decarburization was performed in exactly the same manner as in Example 1. Table 2 shows the properties of the obtained decarburized powder (Cl to C6). The amount of oxygen increased as in Example 1, and the amount of carbon was 0.03% or less.

脱炭粉末 (C1〜C6) を用いて、目標成分を31％Nd-5.0％Dy-1.1％Ｂ-62.9 ％Feと変更した以外は実施例１と全く同様にして直接還元法による脱酸、成分調整を行い、還元反応混合物 (脱炭脱酸混合物) を得た。続いて実施例１と全く同様に純水洗浄、乾燥を行い、還元粉末 (C7〜C12)を得た。表３に示すように、実施例１と同様にCa残留を除いては高品位な希土類合金粉末であることが認められた。   Deoxidization by the direct reduction method in exactly the same manner as in Example 1 except that decarburized powder (C1 to C6) was used and the target component was changed to 31% Nd-5.0% Dy-1.1% B-62.9% Fe. The components were adjusted to obtain a reduction reaction mixture (decarburized and deoxidized mixture). Subsequently, pure water was washed and dried in the same manner as in Example 1 to obtain reduced powder (C7 to C12). As shown in Table 3, in the same manner as in Example 1, it was recognized that the powder was a high-quality rare earth alloy powder except for Ca residue.

これらの還元粉末 (C7〜C12)を、実施例１と全く同様に固溶Ca除去を行い、６種類の熱処理粉末(C13〜Cl8)を得た。このようにして得られた６種類の熱処理粉末(C13〜C18)の成分Ca量を表４に示す。全てにおいて実施例１と同様にCaは0.01％以下まで低減されていた。   These reduced powders (C7 to C12) were subjected to solid solution Ca removal in exactly the same manner as in Example 1 to obtain six kinds of heat treated powders (C13 to Cl8). Table 4 shows the component Ca content of the six types of heat-treated powders (C13 to C18) thus obtained. In all, as in Example 1, Ca was reduced to 0.01% or less.

続いて６種類の熱処理粉末(C13〜C18)を実施例１と全く同様にジェットミルにより微粉末(C19〜C24)を得た。表５に、これらの微粉末の成分と平均粒径を示す。実施例１と同様に不純物の少ない良好な品質であった。   Subsequently, six kinds of heat treated powders (C13 to C18) were obtained in the same manner as in Example 1 by using a jet mill to obtain fine powders (C19 to C24). Table 5 shows the components and average particle diameter of these fine powders. Like Example 1, it was a good quality with few impurities.

得られた微粉末(C19〜C24)を用いて、実施例１と同様に永久磁石を作製した。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。   A permanent magnet was produced in the same manner as in Example 1 using the obtained fine powder (C19 to C24). These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

本例は、銅メッキとNiメッキによる防錆工程で発生した、メッキ不良品からなるスクラップの再生処理を例示する。本例で用いたメッキ不良品(D) は、メッキ前の状態では、実施例３の焼結不良品と全く同じ組成および形状有していた。   This example exemplifies a scrap recycling process that is caused by a plating failure product generated in a rust prevention process using copper plating and Ni plating. The defective plating product (D) used in this example had the same composition and shape as the defective sintering product of Example 3 before plating.

このメッキ不良品(D) 20kgをショットブラストにより銅メッキとNiメッキを完全に剥離した後、ステンレス鋼製密閉容器に装入し、真空引き後、水素を導入し圧力を0.3MPaとして常温で水素化粉砕を行った。その後、真空炉で１×10-2Pa以下で温度300 ℃で１時間の脱水素処理を行い、Arガスで冷却を行った。続いてディスクミルによりAr雰囲気中で粉砕を行い、粉末(D) を得た。粉末(D) の成分と平均粒径を表1 に示す。 After 20kg of this defective plating product (D) is completely removed by copper blasting and Ni plating by shot blasting, it is placed in a stainless steel sealed container, evacuated, hydrogen is introduced and the pressure is set to 0.3MPa at room temperature. Chemical milling was performed. After that, dehydrogenation treatment was performed in a vacuum furnace at 1 × 10 −2 Pa or less at a temperature of 300 ° C. for 1 hour, and then cooled with Ar gas. Subsequently, it was pulverized in an Ar atmosphere by a disk mill to obtain a powder (D). Table 1 shows the components of powder (D) and the average particle size.

この粉末(D) を用いて、実施例１と全く同様に酸化脱炭を行った。得られた脱炭粉末 (D1〜D6) の性状を表２に示す。実施例１〜３と同様に酸素量が増加し、炭素量は0.03％以下であった。   Using this powder (D), oxidative decarburization was performed in exactly the same manner as in Example 1. Table 2 shows the properties of the obtained decarburized powder (D1 to D6). The amount of oxygen increased as in Examples 1 to 3, and the amount of carbon was 0.03% or less.

脱炭粉末 (Dl〜D6) を用いて、目標成分を31％Nd-5.0％Dy-1.1％Ｂ-62.9 ％Feと変更した以外は実施例１と全く同様にして直接還元法による脱酸、成分調整を行い、還元反応混合物を得た。続いて実施例１と全く同様に純水洗浄、乾燥を行い、還元粉末(D7 〜D12)を得た。表３に示すように、実施例１と同様にCa残留を除いては高品位な希土類合金粉末であることが認められた。   Deoxidization by the direct reduction method in exactly the same manner as in Example 1 except that the decarburized powder (Dl to D6) was used and the target component was changed to 31% Nd-5.0% Dy-1.1% B-62.9% Fe. The components were adjusted to obtain a reduction reaction mixture. Subsequently, pure water was washed and dried in the same manner as in Example 1 to obtain reduced powders (D7 to D12). As shown in Table 3, in the same manner as in Example 1, it was recognized that the powder was a high-quality rare earth alloy powder except for Ca residue.

これらの還元粉末 (D7〜D12)を、実施例１と全く同様に固溶Ca除去を行い、６種類の熱処理粉末(D13〜D18)を得た。このようにして得られた６種類の熱処理粉末(D13〜D18)の成分Ca量を表４に示す。全てにおいて実施例１と同様にCaは0.01％以下まで低減されていた。   These reduced powders (D7 to D12) were subjected to solid solution Ca removal in exactly the same manner as in Example 1 to obtain six types of heat treated powders (D13 to D18). Table 4 shows the component Ca content of the six types of heat-treated powders (D13 to D18) thus obtained. In all, as in Example 1, Ca was reduced to 0.01% or less.

続いて６種類の熱処理粉末(D13〜D18)を実施例１と全く同様にジェットミルにより粉砕し微粉末(D19〜D24)を得た。表５に、これらの微粉末の成分と平均粒径を示す。実施例１と同様に不純物の少ない良好な品質であった。   Subsequently, six kinds of heat-treated powders (D13 to D18) were pulverized by a jet mill in the same manner as in Example 1 to obtain fine powders (D19 to D24). Table 5 shows the components and average particle diameter of these fine powders. Like Example 1, it was a good quality with few impurities.

得られた微粉末(D19〜D24)を用いて、実施例１と同様に永久磁石を作製した。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。   A permanent magnet was produced in the same manner as in Example 1 using the obtained fine powder (D19 to D24). These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

実施例１〜４で用いた各種希土類磁石スクラップ粉末(A) 、(B) 、(C) 、(D) を、大気雰囲気で加熱時間２時間、最高温度1000℃の酸化脱炭を行い、続いて水素雰囲気中で加熱時間７時間、最高温度1000℃の水素還元を行って炉冷し、４種類の脱炭粉末(A25) 、(B25) 、(C25) 、(D25) を得た。これらの脱炭粉末の性状 (炭素量、酸素量、希土類量) を表２に示す。炭素量は0.03％以下に低減し、酸素量8.5 ％以上であった。続いて脱炭粉末(A25) 、(B25) 、(C25) 、(D25) を用いて、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥を実施した後に固溶Ca除去を行って、熱処理粉末を得た後、実施例１と全く同様の条件で微粉砕まで行い、微粉末(A26) 、(B26) 、(C26) 、(D26) を得た。   The various rare earth magnet scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were subjected to oxidative decarburization at a maximum temperature of 1000 ° C. in an air atmosphere for 2 hours, followed by In a hydrogen atmosphere, hydrogen reduction was performed at a maximum temperature of 1000 ° C. for 7 hours, and the furnace was cooled to obtain four types of decarburized powders (A25), (B25), (C25), and (D25). Table 2 shows the properties (carbon content, oxygen content, rare earth content) of these decarburized powders. The carbon content was reduced to 0.03% or less, and the oxygen content was 8.5% or more. Subsequently, using decarburized powder (A25), (B25), (C25), (D25), deoxidation and component adjustment were carried out by a direct reduction method to achieve the target compositions of Examples 1 to 4, respectively. After removing the solid solution Ca after washing with pure water and drying to obtain a heat-treated powder, the powder is finely pulverized under the same conditions as in Example 1 to obtain fine powders (A26), (B26), ( C26) and (D26) were obtained.

表５に、これらの微粉末の成分と平均粒径を示す。実施例１と同様に不純物の少ない良好な品質であった。得られた微粉末(A26) 、(B26) 、(C26) 、(D26) を用いて、実施例１と同様に永久磁石を作製した。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。   Table 5 shows the components and average particle diameter of these fine powders. Like Example 1, it was a good quality with few impurities. Using the obtained fine powders (A26), (B26), (C26) and (D26), permanent magnets were produced in the same manner as in Example 1. These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

実施例１〜４で用いた各種希土類磁石スクラップ粉末(A) 、(B) 、(C) 、(D) を、大気の一部導入により真空度を760Pa(酸素分圧160Pa)および1333Pa (酸素分圧280Pa)に増大させた以外は、実施例５と同様の条件で、酸化脱炭および水素還元を実施した。得られた脱炭粉末(A27〜A28)、(B27〜B28)、(C27〜C28)、(D27〜D28)の性状 (炭素量、酸素量、希土類量) を表２に示す。全ての粉末において炭素量は0.03％以下に低減し、酸素量は８〜９％であった。続いて脱炭粉末(A27〜A28)、(B27〜B28)、(C27〜C28)、(D27〜D28)を用いて、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥を実施した後に固溶Ca除去を行って、熱処理粉末を得た後、実施例１と全く同様の条件で微粉砕まで行い、微粉末(A29〜A30)、(B29〜B30)、(C29〜C30)、(D29〜D30)を得た。   Various rare earth magnet scrap powders (A), (B), (C), and (D) used in Examples 1 to 4 were subjected to a partial introduction of the atmosphere to a degree of vacuum of 760 Pa (oxygen partial pressure 160 Pa) and 1333 Pa (oxygen). Oxidation decarburization and hydrogen reduction were performed under the same conditions as in Example 5 except that the partial pressure was increased to 280 Pa). Table 2 shows properties (carbon content, oxygen content, rare earth content) of the obtained decarburized powders (A27 to A28), (B27 to B28), (C27 to C28), and (D27 to D28). In all the powders, the carbon content was reduced to 0.03% or less, and the oxygen content was 8-9%. Subsequently, decarburized powders (A27 to A28), (B27 to B28), (C27 to C28), and (D27 to D28) were used, respectively, so that the target composition of Examples 1 to 4 was obtained by direct reduction. After adjusting the acid and components, followed by washing with pure water and drying, removing the solid solution Ca to obtain a heat-treated powder, the powder was finely ground (under the same conditions as in Example 1). A29 to A30), (B29 to B30), (C29 to C30), and (D29 to D30) were obtained.

表５に、これらの微粉末の成分と平均粒径を示す。実施例１と同様に不純物の少ない良好な品質であった。得られた微粉末(A29〜A30)、(B29〜B30)、(C29〜C30)、(D29〜D30)を用いて、実施例１と同様に永久磁石を作製した。これらのエネルギ積(BHmax) は、表６に示すとおり2.45GA/m以上と良好であった。   Table 5 shows the components and average particle diameter of these fine powders. Like Example 1, it was a good quality with few impurities. Using the obtained fine powders (A29 to A30), (B29 to B30), (C29 to C30), and (D29 to D30), permanent magnets were produced in the same manner as in Example 1. These energy products (BHmax) were as good as 2.45 GA / m or more as shown in Table 6.

(比較例１)
実施例１〜４で用いた各種希土類磁石スクラップ粉末(A) 、(B) 、(C) 、(D) を、実施例１の方法による酸化脱炭を行わない以外は、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥を実施した後に固溶Ca除去を行って、熱処理粉末(A31) 、(B31) 、(C31) 、(D31) を得た。しかし、表３に示すように、酸素量は低減されるが、炭素量の低下は認められなかった。 (Comparative Example 1)
The various rare earth magnet scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were not used in Examples 1 to 4 except that they were not subjected to oxidative decarburization by the method of Example 1. The deoxidation and component adjustment were performed by a direct reduction method so as to achieve the target composition of 4, followed by washing with pure water and drying, followed by removal of solute Ca, and heat treated powders (A31), (B31), ( C31) and (D31) were obtained. However, as shown in Table 3, the amount of oxygen was reduced, but no decrease in the amount of carbon was observed.

続いて、これらの熱処理粉末を、実施例１と全く同様にして、微粉砕まで行い、微粉末(A32) 、(B32) 、(C32) 、(D32) を得た。表５に示すように、炭素量は高いままであり、希土類磁石原料粉末としては不適当な品質であることが判った。   Subsequently, these heat-treated powders were subjected to fine pulverization in the same manner as in Example 1 to obtain fine powders (A32), (B32), (C32), and (D32). As shown in Table 5, the amount of carbon remained high, and it was found that the quality was inappropriate as a rare earth magnet raw material powder.

(比較例２)
実施例１〜４で用いた各種希土類磁石粉末スクラップ粉末(A) 、(B) 、(C) 、(D) を、酸化脱炭の最高温度を550 ℃または1250℃に変更した以外は、実施例1 と同様の条件で、酸化脱炭を実施した。 (Comparative Example 2)
Various rare earth magnet powder scrap powders (A), (B), (C), (D) used in Examples 1 to 4 were used except that the maximum temperature for oxidative decarburization was changed to 550 ° C or 1250 ° C. Under the same conditions as in Example 1, oxidative decarburization was performed.

最高温度1250℃の場合は、全ての粉末において容器底面との溶着が激しく、脱炭粉末を回収することができなかった。最高温度550 ℃で得られた脱炭粉末(A33) 、(B33) 、(C33) 、(D33) の成分を表２に示す。全ての粉末において、炭素量は低減されなかった。   When the maximum temperature was 1250 ° C., all the powders were strongly welded to the bottom of the container, and the decarburized powder could not be recovered. Table 2 shows the components of the decarburized powders (A33), (B33), (C33) and (D33) obtained at the maximum temperature of 550 ° C. In all powders, the carbon content was not reduced.

続いて、最高温度550 ℃の各脱炭粉末について、実施例１〜４の目標組成と全く同様にして直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥を実施した後に固溶Ca除去を行って、還元粉末(A34) 、(B34) 、(C34) 、(D34) を得たが、表３に示すように炭素量は高いままであった。さらに実施例１と同様に、微粉砕まで行い、微粉末(A35) 、(B35) 、(C35) 、(D35) を得たが、表５に示すように、炭素量は高いままであり、希土類磁石原料粉末としては不適当であることが判った。   Subsequently, for each decarburized powder having a maximum temperature of 550 ° C., after performing deoxidation and component adjustment by a direct reduction method in exactly the same manner as the target compositions of Examples 1 to 4, followed by pure water washing and drying Solid solution Ca was removed to obtain reduced powders (A34), (B34), (C34), and (D34). However, as shown in Table 3, the amount of carbon remained high. Further, as in Example 1, fine grinding (A35), (B35), (C35), (D35) was obtained until the pulverization, but as shown in Table 5, the carbon amount remained high, It was found to be inappropriate as a rare earth magnet raw material powder.

(比較例３)
実施例１〜４で用いた各種希土類磁石粉末スクラップ粉末(A) 、(B) 、(C) 、(D) を、最高温度を1000℃とし、加熱時間を0.5 時間または1l時間に変化させた以外は、実施例１と同様の条件で、酸化脱炭を実施した。加熱時間が11時間の場合、炭素量は大幅に低下するものの、全ての粉末において粒子同士が完全に溶着し、且つ低融点相が容器底部に垂れ落ち、回収不能であった。 (Comparative Example 3)
The various rare earth magnet powder scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were set to a maximum temperature of 1000 ° C., and the heating time was changed to 0.5 hours or 1 liter hours. Except for the above, oxidative decarburization was performed under the same conditions as in Example 1. When the heating time was 11 hours, the carbon amount was significantly reduced, but the particles were completely welded in all the powders, and the low melting point phase dropped on the bottom of the container, making it impossible to recover.

加熱時間が0.5 時間において得られた脱炭粉末(A36) 、(B36) 、(C36) 、(D36) の成分を表２に示す。全ての粉末において炭素量は高いままであったため、直接還元を実施しなかった。   Table 2 shows components of the decarburized powders (A36), (B36), (C36), and (D36) obtained at a heating time of 0.5 hours. Direct reduction was not performed because the carbon content remained high in all powders.

(比較例４)
実施例１〜４で用いた各種希土類磁石粉末スクラップ粉末(A) 、(B) 、(C) 、(D) を、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥まで行なった後、加熱温度を800 ℃および700 ℃に変更した以外は、実施例１と全く同様に固溶Ca除去を行った。続いて実施例１と全く同様に微粉砕まで行い、微粉末(A37〜A38)、(B37〜B38)、(C37〜C38)、(D37〜D38)を得た。表７に示すように全ての微粉末において、Ca量が200ppm以上であり希土類磁石原料粉末としては、不適当であることが判った。 (Comparative Example 4)
The various rare earth magnet powder scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were deoxidized by a direct reduction method so as to have the target compositions of Examples 1 to 4, respectively. The solid solution was removed in the same manner as in Example 1 except that the components were adjusted, subsequently washed with pure water and dried, and then the heating temperature was changed to 800 ° C. and 700 ° C. Subsequently, the fine pulverization was performed in the same manner as in Example 1 to obtain fine powders (A37 to A38), (B37 to B38), (C37 to C38), and (D37 to D38). As shown in Table 7, in all the fine powders, the Ca content was 200 ppm or more, which proved to be inappropriate as a rare earth magnet raw material powder.

(比較例５)
実施例１〜４で用いた各種希土類磁石粉末スクラップ粉末(A) 、(B) 、(C) 、(D) を、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥まで行なった後、真空度を15Paおよび20Paとした以外は、実施例１と全く同様に固浴Ca除去を行った。続いて実施例１と全く同様に微粉砕まで行い、微粉末(A33〜A40)、(B39〜B40)、(C39〜C40)、(D39〜D40)を得た。表７に示すように全ての微粉末において、Ca量が200ppm以上であり希土類磁石原料粉末としては、不適当であることが判った。 (Comparative Example 5)
The various rare earth magnet powder scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were deoxidized by a direct reduction method so as to have the target compositions of Examples 1 to 4, respectively. The solid bath was removed in the same manner as in Example 1 except that the components were adjusted, followed by pure water washing and drying, and then the vacuum was changed to 15 Pa and 20 Pa. Subsequently, the fine pulverization was performed in the same manner as in Example 1 to obtain fine powders (A33 to A40), (B39 to B40), (C39 to C40), and (D39 to D40). As shown in Table 7, in all the fine powders, the Ca content was 200 ppm or more, which proved to be inappropriate as a rare earth magnet raw material powder.

(比較例６)
実施例１〜４で用いた各種希土類磁石粉末スクラップ粉末(A) 、(B) 、(C) 、(D) を、それぞれ実施例１〜４の目標組成となるように直接還元法により脱酸、成分調整を行い、続いて純水洗浄、乾燥まで行なった後、熱処理時間を0.1 時間および0.3 時間とした以外は、実施例１と全く同様に固溶Ca除去を行った。続いて実施例１と全く同様に微粉砕まで行い、微粉末(A41〜A42)、(B41〜B42)、(C41〜C42)、(D41〜D42)を得た。表７に示すように全ての微粉末において、Ca量が200ppm以上であり希土類磁石原料粉末としては、不適当であることが判った。 (Comparative Example 6)
The various rare earth magnet powder scrap powders (A), (B), (C) and (D) used in Examples 1 to 4 were deoxidized by a direct reduction method so as to have the target compositions of Examples 1 to 4, respectively. Then, after the components were adjusted, followed by washing with pure water and drying, the solid solution Ca was removed in the same manner as in Example 1 except that the heat treatment time was 0.1 hour and 0.3 hour. Subsequently, the fine pulverization was performed in exactly the same manner as in Example 1 to obtain fine powders (A41 to A42), (B41 to B42), (C41 to C42), and (D41 to D42). As shown in Table 7, in all the fine powders, the Ca content was 200 ppm or more, which proved to be inappropriate as a rare earth magnet raw material powder.

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Claims (6)

希土類磁石の粉末スクラップを、 酸素分圧が140Pa 以下である酸素存在下の雰囲気中で、700 〜1200℃の温度で１〜10時間加熱して酸化脱炭処理を行い脱炭粉末を得る酸化脱炭工程、前記脱炭粉末にアルカリ土類金属からなる還元剤を混合し、得られる混合物を加熱することにより脱酸処理を行う脱酸工程、前記脱酸工程で得られた脱炭脱酸混合物を純水により１回または複数回繰り返して洗浄する洗浄工程、前記洗浄工程で得られた脱炭脱酸混合物を10Pa以下の真空度、900 ℃以上の温度で0.5 時間以上加熱することにより前記還元剤を除去する真空処理工程、および前記真空処理工程で得られた希土類磁石合金を所要粒度に粉砕する粉砕工程とを含む希土類磁石粉末の製造方法。   Oxidation and decarburization powder is obtained by heating rare earth magnet powder scraps in an oxygen-containing atmosphere with an oxygen partial pressure of 140 Pa or less at a temperature of 700 to 1200 ° C for 1 to 10 hours for oxidative decarburization treatment. A deoxidation step in which a deoxidation treatment is performed by mixing a reducing agent composed of an alkaline earth metal with the decarburized powder and heating the resulting mixture, and a decarburized and deoxidized mixture obtained in the deoxidation step Washing step with pure water one or more times, and the reduction by heating the decarburized deoxidized mixture obtained in the washing step at a vacuum degree of 10 Pa or less and a temperature of 900 ° C. or more for 0.5 hour or more. A rare earth magnet powder production method comprising: a vacuum treatment step for removing the agent; and a grinding step for grinding the rare earth magnet alloy obtained in the vacuum treatment step to a required particle size. 希土類磁石の粉末スクラップを、 酸素分圧が140Pa を超える酸素存在下の雰囲気中で、700 〜1200℃の温度で１〜10時間加熱して酸化脱炭処理を行い、次いで、水素還元を行って、脱炭粉末を得る酸化脱炭工程、前記脱炭粉末にアルカリ土類金属からなる還元剤を混合し、得られる混合物を加熱することにより脱酸処理を行う脱酸工程、前記脱酸工程で得られた脱炭脱酸混合物を純水により１回または複数回繰り返して洗浄する洗浄工程、前記洗浄工程で得られた脱炭脱酸混合物を10Pa以下の真空度、900 ℃以上の温度で0.5 時間以上加熱することにより前記還元剤を除去する真空処理工程、および前記真空処理工程で得られた希土類磁石合金を所要粒度に粉砕する粉砕工程とを含む希土類磁石粉末の製造方法。   Rare earth magnet powder scraps were heated in a 700 to 1200 ° C temperature for 1 to 10 hours in an oxygen atmosphere with an oxygen partial pressure exceeding 140 Pa, and then subjected to oxidative decarburization, followed by hydrogen reduction. In the deoxidizing step of obtaining decarburized powder, in the deoxidizing step of mixing the reducing agent composed of alkaline earth metal with the decarburized powder and performing deoxidation treatment by heating the resulting mixture. A washing step of washing the obtained decarburized and deoxidized mixture with pure water once or a plurality of times, and the decarburized and deoxidized mixture obtained in the washing step at a vacuum degree of 10 Pa or less and a temperature of 900 ° C. or more and 0.5 A method for producing rare earth magnet powder, comprising: a vacuum treatment step for removing the reducing agent by heating for at least an hour; and a grinding step for grinding the rare earth magnet alloy obtained in the vacuum treatment step to a required particle size. 前記還元剤がカルシウム系還元剤である請求項１または２記載の希土類磁石粉末の製造方法。   The method for producing a rare earth magnet powder according to claim 1 or 2, wherein the reducing agent is a calcium-based reducing agent. 前記粉砕工程において、水素化粉砕を行うことを特徴とする請求項１〜３のいずれかに記載の希土類磁石粉末の製造方法。   The method for producing a rare earth magnet powder according to any one of claims 1 to 3, wherein hydropulverization is performed in the pulverization step. 前記酸化脱炭工程後、得られた脱炭粉末に、前記還元剤とともに、希土類磁石の合金成分を構成する金属粉末および／または希土類酸化物粉末を添加して前記混合物とする、請求項１ないし４のいずれかに記載の希土類磁石粉末の製造方法。   The metal powder and / or rare earth oxide powder which comprise the alloy component of a rare earth magnet with the said reducing agent are added to the obtained decarburized powder after the said oxidation decarburization process, and it is set as the said mixture. 5. A method for producing a rare earth magnet powder according to any one of 4 above. 前記希土類磁石が、Ｒ-Fe-Ｂ系合金 (Ｒは、Nd、Pr、Dy、Ho、Tbの少なくとも１種を主成分とする希土類金属) からなる請求項１〜５のいずれかに記載の希土類磁石粉末の製造方法。   The said rare earth magnet consists of R-Fe-B type-alloy (R is a rare earth metal which has at least 1 sort (s) of Nd, Pr, Dy, Ho, and Tb as a main component). Method for producing rare earth magnet powder.
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Cited By (6)

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CN100404175C (en) * 2006-05-30 2008-07-23 成都科力铁硬质合金有限公司 Hard alloy recovery method
JP2016532287A (en) * 2013-06-17 2016-10-13 アーバン マイニング テクノロジー カンパニー，エルエルシー Regeneration of magnets to form ND-FE-B magnets with improved or restored magnetic performance
JP2017157663A (en) * 2016-03-01 2017-09-07 大同特殊鋼株式会社 PRODUCTION METHOD OF BASE POWDER OF RFeB-BASED SINTERED MAGNET, AND MANUFACTURING METHOD OF RFeB-BASED SINTERED MAGNET
JP2018003089A (en) * 2016-06-30 2018-01-11 日立金属株式会社 Method for separating both of light rare earth elements and heavy rare earth elements from processing object containing them
CN111477445A (en) * 2020-03-02 2020-07-31 浙江东阳东磁稀土有限公司 Grain boundary diffusion method for sintering neodymium iron boron
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100404175C (en) * 2006-05-30 2008-07-23 成都科力铁硬质合金有限公司 Hard alloy recovery method
JP2016532287A (en) * 2013-06-17 2016-10-13 アーバン マイニング テクノロジー カンパニー，エルエルシー Regeneration of magnets to form ND-FE-B magnets with improved or restored magnetic performance
JP2020047926A (en) * 2013-06-17 2020-03-26 アーバン マイニング テクノロジー カンパニー，エルエルシー Regeneration of magnet for forming nd-fe-b magnet in which magnetic performance is improved or recovered
JP2022062051A (en) * 2013-06-17 2022-04-19 アーバン マイニング テクノロジー カンパニー，エルエルシー Magnet recycling to create nd-fe-b magnets with improved or restored magnetic performance
JP2017157663A (en) * 2016-03-01 2017-09-07 大同特殊鋼株式会社 PRODUCTION METHOD OF BASE POWDER OF RFeB-BASED SINTERED MAGNET, AND MANUFACTURING METHOD OF RFeB-BASED SINTERED MAGNET
JP2018003089A (en) * 2016-06-30 2018-01-11 日立金属株式会社 Method for separating both of light rare earth elements and heavy rare earth elements from processing object containing them
US11491545B2 (en) 2018-08-24 2022-11-08 Lg Chem, Ltd. Method of preparing magnetic powder, and magnetic powder
CN111477445A (en) * 2020-03-02 2020-07-31 浙江东阳东磁稀土有限公司 Grain boundary diffusion method for sintering neodymium iron boron

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