JPH03169001A - Dry-process stabilization of metal powder - Google Patents
Dry-process stabilization of metal powderInfo
- Publication number
- JPH03169001A JPH03169001A JP1307516A JP30751689A JPH03169001A JP H03169001 A JPH03169001 A JP H03169001A JP 1307516 A JP1307516 A JP 1307516A JP 30751689 A JP30751689 A JP 30751689A JP H03169001 A JPH03169001 A JP H03169001A
- Authority
- JP
- Japan
- Prior art keywords
- oxygen
- temperature
- gas
- magnetic powder
- metal magnetic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000002184 metal Substances 0.000 title claims abstract description 33
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 33
- 238000011105 stabilization Methods 0.000 title abstract description 26
- 230000006641 stabilisation Effects 0.000 title abstract description 25
- 239000000843 powder Substances 0.000 title abstract description 3
- 238000001035 drying Methods 0.000 title 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000001301 oxygen Substances 0.000 claims abstract description 40
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 17
- 230000005291 magnetic effect Effects 0.000 claims abstract description 13
- 239000011261 inert gas Substances 0.000 claims abstract description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000007789 gas Substances 0.000 claims abstract description 9
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910001882 dioxygen Inorganic materials 0.000 claims abstract description 7
- 229910052742 iron Inorganic materials 0.000 claims abstract description 5
- 239000006247 magnetic powder Substances 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 14
- 230000000087 stabilizing effect Effects 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 230000003647 oxidation Effects 0.000 abstract description 23
- 238000007254 oxidation reaction Methods 0.000 abstract description 23
- 239000012530 fluid Substances 0.000 abstract description 4
- 238000000137 annealing Methods 0.000 description 19
- 239000002245 particle Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 239000010419 fine particle Substances 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- KYARBIJYVGJZLB-UHFFFAOYSA-N 7-amino-4-hydroxy-2-naphthalenesulfonic acid Chemical compound OC1=CC(S(O)(=O)=O)=CC2=CC(N)=CC=C21 KYARBIJYVGJZLB-UHFFFAOYSA-N 0.000 description 1
- 241001168730 Simo Species 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000010405 reoxidation reaction Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005987 sulfurization reaction Methods 0.000 description 1
- 239000002023 wood Substances 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
- H01F1/06—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 in the form of particles, e.g. powder
- H01F1/061—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 in the form of particles, e.g. powder with a protective layer
Abstract
Description
【発明の詳細な説明】
産業上の利用分野
この発明はＳｉ０２で表面処理された鉄を主体とする磁
気記録用、金属磁性粉末の乾式安定化処理に関するもの
である．
従来の技術
鉄を主体とする磁気記録用金属磁性粉末は保磁力（Ｈｃ
）．飽和磁化（σＳ）が大きく高密度記録が可能であり
、今後の磁気記録の中核を威す材料として注目されてい
る．しかしながらこの金属磁性粉末は酸化安定性が劣る
という最大の欠点を有する．即ち，比表面積が大きく化
学的に極めて活性であるために、発火の危険性や酸化に
よる経時劣化が大きい．またこれらの欠点は微粒子化し
た場合やＳｉモで表面処理した場合に顕著になって〈る
．
Ｌ，かしながら今後、磁気記録用金属磁性粉末は記録′
ｐＥ度向上やノイズ低減のために微粒子化する傾向にあ
り、酸化安定性の問題がさらにクローズアップされてく
ることが容易に予想される．そこで、微粒子化しても高
σＳを保持し、かつ大気中に取り出しても発火せず，ま
た経時劣化を抑制する安定化処理技術の確立が待ち望ま
れている．これまでに様々な安定化方法が提案されてお
り、その中でも不活性ガス中で加熱焼鈍することで酸化
皮膜を結晶化させ、安定性を向上させる方法が知られて
いるが（特開昭８１− １５４１１２、特開昭８２−
１１２７０２、特開昭８２一目２７０３など），加熱焼
鈍中に酸化皮膜が再活性化されるため、再び安定化が必
要となり、σＳが必要以上に低下する．そのため微粒子
金属磁性粉末の安定化処理方法として満足できる方法と
はいい難い．
発明が解決しようとする課題
従来の方法では、不活性ガス中で加熱焼鈍する事により
安定性は向上するものの，再安定化によるσＳの低下は
避けられず、微粒子化した場合に酸化安定性とσＳを両
立させることは極めて困難となってくる．
本発明は微粒子金属磁性粉末において、表面を準安定化
状態まで均一に酸化した後に、加熱焼鈍することでこの
問題を解決し，酸化安定性を良好に保ったまま高σＳを
確保できる磁気記録用、微粒子金属磁性粉末の安定化方
法を提供するものである．
課題を解決するための手段
本発明は、鉄を主体とする金属磁性粉末を常温〜１２０
℃の一定温度で不活性ガスで流動させ、酸素濃度の増加
率が毎分１０〜２０００ｐｐｍとなるように酸素ガスを
混合し続け、流動層内の温度がピークに達した時点およ
び／または出側ガス中に酸素を検出した時点で酸素の供
給を遮断する．その後、層内温度を１５０〜６００℃ま
で加熱し０．２〜２４時間保持した後に冷却し、前述と
同様の方法で酸素を混合し続ける．
流動層内の温度がピークに達した時点および／または出
側ガス中に酸素を検出した時点で酸素濃度を保持し、出
側、入側の酸素濃度が等しくなった時点および／または
層内温度が安定化開始時の温度まで低下した時点で，室
温まで冷却し安定化を終了する．
その結果、均一かつ緻密な酸化皮膜を形威し、高σＳ、
高酸化安定性を付与する磁気記録用微粒子金属磁性粉末
の安定化方法である．
以下に本発明を詳細に説明する．
本発明において，金属磁性粉末を均一に酸化するために
は、適正な流動状態にあることが大切であり、そのため
金属磁性粉末は造粒物を用いることが望ましい．この金
属磁性粉末の造粒物の粒度範囲は０．１〜５ｓ＋一が適
切である．すなわち粒度が０．１■未満では流動層外へ
の飛散が著しく、逆に５■超では流動化の状態が悪く均
一な酸化が出来ない．金属磁性粉末を流動化する際に使
用する不活性ガスはＨｅ． Ｘｓ， Ａｒ．（：０２
， Ｎ２等があるが、通常は西ガスを用いるのが実用的
である．次に流動層内の温度が常温〜１２０℃で一定と
なるように流動層外周の温度を制御する．この時の温度
が安定化開始温度であり、金属磁性粉末表面の酸化量を
決定し、σＳをコントロールする上で極めて重要である
．この際の温度が常温より低くなると表面酸化が充分に
行なわれず、この後の加熱焼鈍による結晶化の効果が十
分発揮されない．またこの時の温度が１２０℃超では表
面酸化が必要以上に進み高いσＳは得られない．ここで
常温とはＯ〜３０℃である．
次に、金属磁性粉末の造粒物を不活性ガスで流動化させ
，ここに酸素ガスあるいは空気を混合していき金属磁性
粉末表面を徐酸化する．この酸化方法が木発明の第１工
程である．すなわち、流動層外周の温度を一定に保ちな
がら，酸素濃度の増加率が一定となるように、不活性ガ
スに酸素ガスまたは空気を混合していく．
ここで酸素濃度増加率は毎分１０〜２００ＯＰＰ雪とす
るのが好ましい．酸素濃度増加率が毎分ｔｏｐｐ口未満
では安定化に長時間を要し実用的ではない．逆に酸素濃
度増加率が毎分２０００ｐｐｍ超では酸化にむらが生じ
て効果的な安定化ができず、高いσＳが得られない．
このようにして徐酸化を続けて行くと、その温度におい
て金属磁性粉末が準安定化するに要する酸化皮膜を形威
したところで，Ｓ化速度は自動的に減速する．つまり上
昇してきた流動層内の温度が低下し、同時に出側ガス中
に酸素が検出されるため、準安定化状態に達したことが
極めて容易に判断できる．
この準安定化状態とは、ほとんどの酸化皮膜は完威して
いるが，部分的に活性点が残存している状態である．大
気中に安定に取り出すためにはさらに酸化が必要であり
、この傾向は金属磁性粉末がＳｉ０２で表面処理されて
いる場合に顕著に現れる．
準安定化状態まで酸化した後に不活性ガス中で加熱焼鈍
することが本発明の第２工程であり、酸化安定性を高く
保ち、σＳを向上することができる．すなわち、焼鈍前
の初ｗＪ酸化が不十分の場合、つまり準安定化状態とな
る前に初期酸化を終了した場合は，加熱焼鈍により得ら
れる安定性の向上効果が小さい．逆に初期酸化が過剰の
場合、つまり準安定化状態よりも酸化が進んでから加熱
焼鈍した場合は，酸化安定性は向上するが，加熱焼鈍後
の再安定化のためにσＳが低下してしまう．
加熱焼鈍温度は１５０〜６００℃が適当である．１５０
℃未満では加熱焼鈍の効果が得られ難く，逆に６００℃
超では粒子が焼結し、形状を悪化させてしまう．加熱焼
鈍時間は温度によって決定されるが、０．２〜２４時間
が適当である．これが０．２時間未満では加熱焼鈍の効
果が現れにくく、逆に２４時間超では実用的ではない．
加熱焼鈍することで金属磁性粉末の酸化皮膜は結晶化す
るが、酸素の拡散等が起こり再び活性になるため、加熱
焼鈍後に再安定化する第３工程が必要である．この再酸
化は加熱焼鈍後、常温〜１２０℃まで冷却したのち第１
工程と同様の方法で行ない、温度ピークおよび／または
出側ガス中に酸素を検出した時点で入側酸素濃度を保定
し、出側酸素濃度が入側酸素濃度と等しくなった時点で
，流動層の温度を常温まで冷却し安定化処理を終了する
．この工程によりσＳを高く保つことができる．
尚、第ｌ工程の酸化が不十分でも、第３工程を完全に行
えば、本発明の目的が達或される．
このように準安定化状態まで初期安定化し、その後不活
性ガス中で加熱焼鈍後，再安定化することにより、均一
かつ緻密な酸化皮膜を有しσＳが高く、酎食性の良好な
金属磁性粉末を製造することができる．
実施例ｌ
安定化に用いた流動層は内径４０ｍｍのバイレックスガ
ラス製であり，目皿にはガラスフィルターを使用してあ
る．この流動層は２重管になっており、外側にジャケッ
トを設け、恒温水槽より温水を循環させることで流動層
内の温度制御を行なラ．
還元直後の粒度範囲０．２５〜０．５ｓ■の金属磁性粉
末の造粒物２８ｇを，大気に触れさせることなく安定化
に用いる流動層に移送した．ここで使用した金属磁性粉
末は長袖０．１５ｇｍの微粒子であり，Ｓｉ％で表面処
理し，４８０℃で還元したものである．この金属磁性粉
末の安定化処理前の磁気特性は、トルエンに浸漬し，自
然風乾した状態で、Ｈｃｌ７１４０ｅ、ｃｒ ｓ １４
４ｅｍｕ／ｇ、角型比０．５２であった．まず第１工程
として，流動層内の温度を８０℃に保ち、１０ ｆＬ
／ｗｉｎで窒素ガスを吹き込むことで強磁性金属粉末を
良好な流動状態とした．次いで，この窒素ガスに空気を
毎分１０＋ａＱ／ｓｉｎ （酸素濃度増加＝１１Ｋ０．
０２％／ｓｉｎ）で混合し続けた．安定化開始後２Ｂ分
で流ｇｈ層内の温度は７３℃でピークに達し、出側の酸
素濃度が検出された．この時の入側酸素濃度は０．５２
％であった．
この時点で空気の導入を中止し、第２工程として、流動
層の温度を４００℃まで昇温し１時間加熱焼鈍した．
その後，再び流動層の温度を８０℃とし、第３工程とし
て前記第ｌ工程と同様の方法で再安定化を行なった．再
安定化開始後１２分で流動層内の温度は６４℃でピーク
に達し、出側の酸素濃度が検出された．この時の入｛Ｉ
Ｉ酸稟濃度は０．２４％であった．この時点で入側酸素
濃度を０．２４％で１０分保定し，出側酸素濃度が０．
２２％となったところで流動層を室温（１５℃）まで冷
却し安定化処理を終えた．実施例２
加熱焼鈍温度を３００℃とした以外は実施例１と同様の
方法で安定化処理を行なった．
実施例３
初期酸化を酸化開始後１５分（酸素濃度０．３％）で打
ち切った以外は、実施例１と同様の方法で安定化処理を
行なった．この時、再安定化には２ｌ分を要した．
実施例４
安定化開始温度を２４℃とした以外は、実施例ｌと同様
の方法で安定化処理を行なった．この時、初期安定化に
は２０分、再安定化には１７分を要した．
比較例１
実施例ｌの第１工程と同様の方法で安定化を行い、温度
ピークに達したところで入側酸素濃度を一定に保ち、出
側酸素濃度入側酸素濃度と等しくなった後に流動層を室
温まで冷却し安定化を終了した．
第ｌ表に、各実施例および比較例の方法で得られた、酸
化皮膜を有する金属磁性粉末のＶＳＭによる最大印加磁
場１ ０ｋＯｅでの磁気特性、ＤＴＡを用いた昇温速度
１０℃／ｗｉｎでの発火点、および６０℃、相対温度９
０％、１週１’ｌＪｌ後のσＳを示した．発明の効果
本発明の方法により，微粒子化された金属磁性粉末にお
いても、高σＳ、かつ高酸化安定性を付与する安定化処
理が可能となり、発火の危険性がなく、磁気特性が優れ
、経時劣化の少ない酸化皮膜を有する金属磁性粉末が得
られた．また本発明による方法は安定化処理の終点判定
が極めて容易であり、しかも短時間で処理を終了できる
ために工業的スケールでの実施においても実用的な方法
である．DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to dry stabilization treatment of metal magnetic powder for magnetic recording, mainly made of iron whose surface has been treated with Si02. Conventional technology The metal magnetic powder for magnetic recording mainly made of iron has a coercive force (Hc
). It has a large saturation magnetization (σS) and enables high-density recording, and is attracting attention as a material that will play a central role in future magnetic recording. However, this metal magnetic powder has the biggest drawback of poor oxidation stability. In other words, because it has a large specific surface area and is extremely chemically active, it poses a high risk of ignition and deteriorates over time due to oxidation. Furthermore, these drawbacks become more noticeable when the particles are made into fine particles or when the surface is treated with SiMo. However, in the future, metal magnetic powder for magnetic recording will not be used for recording.
There is a trend toward finer particles in order to improve the pE degree and reduce noise, and it is easy to predict that the problem of oxidation stability will become more of a focus. Therefore, there is a need for the establishment of a stabilizing treatment technology that maintains a high σS even after being reduced to fine particles, does not ignite even when taken out into the atmosphere, and suppresses deterioration over time. Various stabilization methods have been proposed so far, and among them, a method is known in which the stability is improved by crystallizing the oxide film by heating and annealing it in an inert gas (Japanese Unexamined Patent Publication No. 81 - 154112, JP-A-1982-
112702, Japanese Unexamined Patent Publication No. 112702, JP-A-1982-112 Ichimoku 2703, etc.), the oxide film is reactivated during heat annealing, so stabilization is required again, and σS decreases more than necessary. Therefore, it is difficult to say that this is a satisfactory method for stabilizing fine-grained metal magnetic powder. Problems to be Solved by the Invention In the conventional method, although the stability is improved by heating and annealing in an inert gas, a decrease in σS due to restabilization is unavoidable, and when the particles are made into fine particles, the oxidation stability It becomes extremely difficult to achieve both σS. The present invention solves this problem by uniformly oxidizing the surface of fine-grained metal magnetic powder to a quasi-stable state and then annealing it by heating. , provides a method for stabilizing fine particle metal magnetic powder. Means for Solving the Problems The present invention provides metal magnetic powder mainly composed of iron at room temperature to 120°C.
Fluidize with inert gas at a constant temperature of ℃, continue to mix oxygen gas so that the rate of increase in oxygen concentration is 10 to 2000 ppm per minute, and when the temperature in the fluidized bed reaches its peak and/or at the exit side When oxygen is detected in the gas, the oxygen supply is cut off. Thereafter, the temperature inside the layer is heated to 150 to 600°C, held for 0.2 to 24 hours, and then cooled, and oxygen is continued to be mixed in the same manner as described above. The oxygen concentration is maintained at the time when the temperature in the fluidized bed reaches its peak and/or when oxygen is detected in the outlet gas, and the time when the oxygen concentrations on the outlet and inlet sides become equal and/or the temperature in the bed is maintained. When the temperature has decreased to the temperature at the start of stabilization, it is cooled to room temperature and stabilization is completed. As a result, a uniform and dense oxide film is formed, with high σS,
This is a method for stabilizing fine-grain metal magnetic powder for magnetic recording that provides high oxidation stability. The present invention will be explained in detail below. In the present invention, in order to uniformly oxidize the metal magnetic powder, it is important that the metal magnetic powder be in an appropriate fluid state, and therefore it is preferable to use granules as the metal magnetic powder. The appropriate particle size range of the granulated metal magnetic powder is 0.1 to 5s+1. That is, if the particle size is less than 0.1 sq., scattering outside the fluidized bed is significant, whereas if it exceeds 5 sq., fluidization is poor and uniform oxidation cannot be achieved. The inert gas used to fluidize the metal magnetic powder is He. Xs, Ar. (:02
, N2, etc., but it is usually practical to use Western gas. Next, the temperature around the fluidized bed is controlled so that the temperature within the fluidized bed remains constant between room temperature and 120°C. The temperature at this time is the stabilization start temperature, which is extremely important in determining the amount of oxidation on the surface of the metal magnetic powder and controlling σS. If the temperature at this time is lower than room temperature, sufficient surface oxidation will not occur, and the crystallization effect of subsequent heat annealing will not be fully demonstrated. Furthermore, if the temperature at this time exceeds 120°C, surface oxidation will proceed more than necessary, making it impossible to obtain a high σS. Here, normal temperature is 0 to 30°C. Next, the granulated metal magnetic powder is fluidized with an inert gas, and oxygen gas or air is mixed therein to slowly oxidize the surface of the metal magnetic powder. This oxidation method is the first step in wood invention. In other words, while keeping the temperature around the fluidized bed constant, oxygen gas or air is mixed with the inert gas so that the rate of increase in oxygen concentration remains constant. Here, it is preferable that the oxygen concentration increase rate is 10 to 200 OPP snow per minute. If the rate of increase in oxygen concentration is less than TOPP per minute, it will take a long time to stabilize, which is not practical. On the other hand, if the oxygen concentration increase rate exceeds 2000 ppm per minute, oxidation becomes uneven and effective stabilization cannot be achieved, making it impossible to obtain a high σS. If gradual oxidation is continued in this manner, the rate of sulfurization will automatically slow down once the oxide film required to make the metal magnetic powder metastable at that temperature is formed. In other words, the temperature inside the fluidized bed, which has been rising, decreases, and at the same time oxygen is detected in the outlet gas, making it extremely easy to determine that a metastable state has been reached. This metastable state is a state in which most of the oxide film is completely destroyed, but some active sites remain. Further oxidation is necessary for stable extraction into the atmosphere, and this tendency is noticeable when the metal magnetic powder is surface-treated with Si02. The second step of the present invention is to oxidize to a quasi-stable state and then heat and anneal in an inert gas, which makes it possible to maintain high oxidation stability and improve σS. That is, if the initial wJ oxidation before annealing is insufficient, that is, if the initial oxidation is completed before a metastable state is reached, the effect of improving stability obtained by heat annealing is small. On the other hand, if initial oxidation is excessive, that is, if heating and annealing is performed after oxidation has progressed beyond the metastable state, oxidation stability will improve, but σS will decrease due to restabilization after heating and annealing. Put it away. The suitable heating annealing temperature is 150 to 600°C. 150
It is difficult to obtain the effect of heat annealing below 600°C.
If the temperature is too high, the particles will sinter and the shape will deteriorate. The heating annealing time is determined by the temperature, but 0.2 to 24 hours is appropriate. When this time is less than 0.2 hours, the effect of heat annealing is difficult to appear, and on the other hand, when it is more than 24 hours, it is not practical. Although the oxide film of the metal magnetic powder crystallizes by heating and annealing, it becomes active again due to oxygen diffusion, etc., so a third step of restabilizing it is necessary after heating and annealing. This reoxidation is carried out after heating and annealing, and after cooling from room temperature to 120℃,
The process is carried out in the same manner as in the process, and the inlet oxygen concentration is maintained when the temperature peak and/or oxygen is detected in the outlet gas, and when the outlet oxygen concentration becomes equal to the inlet oxygen concentration, the fluidized bed is The temperature is cooled down to room temperature and the stabilization process is completed. This process allows σS to be kept high. Incidentally, even if the oxidation in the first step is insufficient, the object of the present invention can be achieved as long as the third step is performed completely. In this way, by initially stabilizing to a quasi-stable state and then restabilizing after heating and annealing in an inert gas, a metal magnetic powder with a uniform and dense oxide film, high σS, and good corrosion resistance is produced. can be manufactured. Example 1 The fluidized bed used for stabilization was made of Virex glass with an inner diameter of 40 mm, and a glass filter was used for the perforated plate. This fluidized bed is a double pipe, with a jacket installed on the outside, and the temperature inside the fluidized bed is controlled by circulating hot water from a constant temperature water tank. Immediately after reduction, 28 g of granulated metal magnetic powder with a particle size range of 0.25 to 0.5 s<2> was transferred to a fluidized bed used for stabilization without exposure to the atmosphere. The metal magnetic powder used here was a long sleeve 0.15 gm fine particle, surface treated with Si% and reduced at 480°C. The magnetic properties of this metal magnetic powder before stabilization treatment were as follows: Hcl7140e, cr s 14
It was 4 emu/g and the squareness ratio was 0.52. First, in the first step, the temperature in the fluidized bed was maintained at 80°C, and 10 fL
The ferromagnetic metal powder was brought into a good fluid state by blowing nitrogen gas at /win. Next, air was added to this nitrogen gas at a rate of 10+aQ/sin per minute (oxygen concentration increase=11K0.
02%/sin). 2B minutes after the start of stabilization, the temperature in the flowing GH layer reached a peak of 73°C, and the oxygen concentration on the outlet side was detected. At this time, the inlet oxygen concentration is 0.52
%Met. At this point, the introduction of air was stopped, and in the second step, the temperature of the fluidized bed was raised to 400°C and heat annealing was performed for 1 hour. Thereafter, the temperature of the fluidized bed was raised to 80° C. again, and as a third step, restabilization was performed in the same manner as in the first step. Twelve minutes after the start of restabilization, the temperature within the fluidized bed reached a peak of 64°C, and the oxygen concentration on the outlet side was detected. At this time {I
The I acid concentration was 0.24%. At this point, the inlet oxygen concentration was held at 0.24% for 10 minutes, and the outlet oxygen concentration was 0.24%.
When the concentration reached 22%, the fluidized bed was cooled to room temperature (15°C) to complete the stabilization treatment. Example 2 Stabilization treatment was carried out in the same manner as in Example 1 except that the heating annealing temperature was 300°C. Example 3 Stabilization treatment was carried out in the same manner as in Example 1, except that the initial oxidation was stopped 15 minutes after the start of oxidation (oxygen concentration 0.3%). At this time, it took 2 liters to restabilize. Example 4 Stabilization treatment was carried out in the same manner as in Example 1, except that the stabilization start temperature was 24°C. At this time, initial stabilization took 20 minutes and re-stabilization took 17 minutes. Comparative Example 1 Stabilization was performed in the same manner as in the first step of Example 1, and when the temperature peak was reached, the inlet oxygen concentration was kept constant, and after the outlet oxygen concentration became equal to the inlet oxygen concentration, the fluidized bed Stabilization was completed by cooling to room temperature. Table 1 shows the magnetic properties of metal magnetic powders with oxide films obtained by the method of each example and comparative example at a maximum applied magnetic field of 10 kOe using VSM, and at a heating rate of 10°C/win using DTA. ignition point of and 60°C, relative temperature 9
0%, σS after 1 week and 1'lJl. Effects of the Invention The method of the present invention makes it possible to perform stabilization treatment that imparts high σS and high oxidation stability even to finely divided metal magnetic powders.There is no risk of ignition, excellent magnetic properties, and stability over time. Metal magnetic powder with an oxide film with little deterioration was obtained. Furthermore, the method according to the present invention makes it extremely easy to determine the end point of the stabilization treatment, and the treatment can be completed in a short time, making it a practical method even when implemented on an industrial scale.
Claims (1)
金属磁性粉末を安定化することを特徴とする磁気記録用
、微粒子金属磁性粉末の乾式安定化方法。 （イ）常温〜１２０℃の一定温度で金属磁性粉末を不活
性ガスで流動させ、前記不活性ガス中に濃度の増加率が
毎分１０〜２，０００ｐｐｍとなるように酸素ガスを混
合し、流動層内の温度がピークに達した時点および／ま
たは出側ガス中に酸素を検出した時点で酸素の供給を遮
断する第一工程、 （ロ）次いで、不活性ガスによる流動状態で、流動層の
温度を１５０〜６００℃まで加熱し０．２〜２４時間保
持したのち、常温〜１２０℃まで冷却する第二工程、 （ハ）次いで、前記不活性ガス中に濃度の増加率が毎分
１０〜２，０００ｐｐｍとなるよう酸素ガスを混合し、
流動層内の温度がピークに達した時点および／または出
側ガス中に酸素を検出した時点で酸素濃度をその時点の
混合酸素濃度に保持し、出側、入側の酸素濃度が等しく
なった時点および／または層内温度が前記酸素ガス混合
開始時の温度まで低下した時点で流動層の温度を常温ま
で冷却する第三行程。[Scope of Claims] A method for dry stabilizing fine-grained metal magnetic powder for magnetic recording, characterized by stabilizing iron-based fine-grained metal magnetic powder for magnetic recording by the following steps. (a) Fluidizing the metal magnetic powder with an inert gas at a constant temperature of room temperature to 120°C, and mixing oxygen gas in the inert gas so that the concentration increase rate is 10 to 2,000 ppm per minute, The first step is to cut off the supply of oxygen when the temperature in the fluidized bed reaches its peak and/or when oxygen is detected in the outlet gas. (c) a second step of heating the inert gas to a temperature of 150 to 600°C, holding it for 0.2 to 24 hours, and then cooling it to room temperature to 120°C; Mix oxygen gas to ~2,000 ppm,
When the temperature in the fluidized bed reaches its peak and/or when oxygen is detected in the outlet gas, the oxygen concentration is maintained at the mixed oxygen concentration at that point, and the oxygen concentrations on the outlet and inlet sides are equal. A third step in which the temperature of the fluidized bed is cooled to room temperature at the point in time and/or at the point in time when the temperature in the bed has decreased to the temperature at the start of oxygen gas mixing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1307516A JPH03169001A (en) | 1989-11-29 | 1989-11-29 | Dry-process stabilization of metal powder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1307516A JPH03169001A (en) | 1989-11-29 | 1989-11-29 | Dry-process stabilization of metal powder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03169001A true JPH03169001A (en) | 1991-07-22 |
Family
ID=17970023
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1307516A Pending JPH03169001A (en) | 1989-11-29 | 1989-11-29 | Dry-process stabilization of metal powder |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03169001A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5735969A (en) * | 1996-03-07 | 1998-04-07 | Imation Corp. | Method of producing acicular magnetic alloy particles |
| EP1376625A2 (en) * | 2002-05-31 | 2004-01-02 | Fuji Photo Film Co., Ltd. | Magnetic particle and its production method |
| US7384449B2 (en) | 2001-09-05 | 2008-06-10 | Fujifilm Corporation | Ferromagnetic nanoparticles, material coated with dispersion of ferromagnetic nanoparticles, and magnetic recording medium using the material |
| US7473469B2 (en) | 2005-12-23 | 2009-01-06 | Dowa Electronics Materials Co., Ltd. | Ferromagnetic powder for a magnetic recording medium, method of producing the powder, and magnetic recording medium using the powder |
| JP2011047025A (en) * | 2009-08-28 | 2011-03-10 | Toda Kogyo Corp | Method for producing ferromagnetic metal grain powder, ferromagnetic metal grain powder, and magnetic recording medium |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60128202A (en) * | 1983-12-13 | 1985-07-09 | Toyo Soda Mfg Co Ltd | Production of magnetic metallic powder |
| JPS62112702A (en) * | 1985-11-09 | 1987-05-23 | Chisso Corp | Production of ferromagnetic metallic powder having oxide film |
-
1989
- 1989-11-29 JP JP1307516A patent/JPH03169001A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60128202A (en) * | 1983-12-13 | 1985-07-09 | Toyo Soda Mfg Co Ltd | Production of magnetic metallic powder |
| JPS62112702A (en) * | 1985-11-09 | 1987-05-23 | Chisso Corp | Production of ferromagnetic metallic powder having oxide film |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5735969A (en) * | 1996-03-07 | 1998-04-07 | Imation Corp. | Method of producing acicular magnetic alloy particles |
| US7384449B2 (en) | 2001-09-05 | 2008-06-10 | Fujifilm Corporation | Ferromagnetic nanoparticles, material coated with dispersion of ferromagnetic nanoparticles, and magnetic recording medium using the material |
| EP1376625A2 (en) * | 2002-05-31 | 2004-01-02 | Fuji Photo Film Co., Ltd. | Magnetic particle and its production method |
| EP1376625A3 (en) * | 2002-05-31 | 2006-03-15 | Fuji Photo Film Co., Ltd. | Magnetic particle and its production method |
| US7244287B2 (en) | 2002-05-31 | 2007-07-17 | Fujifilm Corporation | Magnetic particle, its production method, magnetic recording medium and its production method |
| EP1850355A1 (en) * | 2002-05-31 | 2007-10-31 | FUJIFILM Corporation | Magnetic particle and its production method |
| US7335393B2 (en) | 2002-05-31 | 2008-02-26 | Fujifilm Corporation | Magnetic particle, its production method, magnetic recording medium and its production method |
| US7473469B2 (en) | 2005-12-23 | 2009-01-06 | Dowa Electronics Materials Co., Ltd. | Ferromagnetic powder for a magnetic recording medium, method of producing the powder, and magnetic recording medium using the powder |
| JP2011047025A (en) * | 2009-08-28 | 2011-03-10 | Toda Kogyo Corp | Method for producing ferromagnetic metal grain powder, ferromagnetic metal grain powder, and magnetic recording medium |
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