CN102737801B

CN102737801B - Method for preparing Sm-Fe-N anisotropic magnetic powder

Info

Publication number: CN102737801B
Application number: CN201210240572.8A
Authority: CN
Inventors: 林国标; 包小倩; 毕文龙; 张茂才
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2012-07-11
Filing date: 2012-07-11
Publication date: 2014-09-17
Anticipated expiration: 2032-07-11
Also published as: CN102737801A

Abstract

The invention discloses a method for preparing Sm-Fe-N anisotropic magnetic powder, which belongs to the field of magnetic materials. The technological process is as follows: preparing an alloy melt; controlling parameters of a rapid solidification process and the thicknesses of casting pieces; obtaining fast-setting casting pieces with nearly-consistent oriented small Sm2Fe17 cylindrical crystals; carrying out crystallization processing on the fast-setting casting pieces; carrying out coarse crushing; nitriding the fast-setting casting pieces; carrying out fine grinding; and obtaining the anisotropic Sm-Fe-N magnetic powder. The method is mainly characterized in that: through controlling the rotating speed of a cooling copper roller, the gas pressure of melt injection, the size of a nozzle, the temperature of the melt and the compositions of the melt, the cooling rate and crystallization process of the melt are controlled, so that fast-setting casting pieces with consistent oriented small Sm2Fe17 cylindrical crystals are obtained, thereby laying a foundation for the preparation of anisotropic magnetic powder and bonded permanent magnets with consistent oriented magneto-crystallines. By using the method for preparing Sm-Fe-N anisotropic magnetic powder, a normally required operation of carrying out long-time high-temperature homogenizing annealing on Sm-Fe alloy ingots is avoided.

Description

A kind of preparation method of Sm-Fe-N anisotropic magnet powder

Technical field

The invention belongs to field of magnetic material, relate to a kind of preparation method of Sm-Fe-N anisotropic magnet powder.

Background technology

Sm2Fe ₁₇n _xthere is excellent intrinsic magnetic properties energy, be described as the later permanent magnetic material of new generation of the Nd-Fe-B that continues.With Nd ₂fe ₁₄b compares, and it has higher Curie temperature (exceeding nearly 160 ° of C), extra high magnetocrystalline anisotropy, H _a=11.2MA/m(140KOe), be only second to SmCo ₅, be Nd ₂fe ₁₄2 times of B, theoretical magnetic energy product is 472KJ/m ³(59.2MGOe), with Nd ₂fe ₁₄b(509KJ/m ³) about the same.Due to Sm ₂fe ₁₇n _xat high temperature can decompose, thus can not sintering, can only make bonded magnet.With regard to intrinsic magnetic characteristic, Sm ₂fe ₁₇n _xsaturated pole intensity a little less than Nd ₂fe ₁₄b, but its Curie temperature and magnetocrystalline anisotropy field are all far above the latter.In addition from practical angle, Sm ₂fe ₁₇n _xthermal stability, non-oxidizability and corrosion resistance be all better than Nd ₂fe ₁₄b.Its another outstanding advantages is to make anisotropy bonded magnetic powder and bonded magnet.

Preparation Sm at present ₂fe ₁₇n _xmethod mainly contain: mechanical alloying method (MA), hydrogen crush method (HDDR), reduction-diffusion process (R/D), quick quenching technique (RQ), powder metallurgic method (PM).The preparation Sm of the whole bag of tricks ₂fe ₁₇powder and Sm thereof ₂fe ₁₇n _xtechnological process, the feature of magnetic are as follows:

Mechanical alloying method (MA): pure constituent element powder mixing → high-energy ball milling → formation laminate granular → diffusion annealing, forms nanocrystal → nitrogenize → Sm ₂fe ₁₇n _xmagnetic.Mechanical alloying method is prepared Sm ₂fe ₁₇need long high-energy ball milling, powder activity is high, particle is thin, the increase that easily brings oxygen content in nitrogenize with in preparing bonded magnet process; Because powder particle is too little, be difficult to prepare highdensity bonded permanent magnet; Although powder particle is very little, not necessarily monocrystalline single domain particle, is mainly suitable for preparing isotropism magnetic.

Reduction-diffusion process (R/D): the Sm of certain proportioning ₂o ₃, the raw material → batch mixing → briquetting → reduction diffusion reaction → product separation → nitrogenize → fine grinding → Sm such as Ca, Fe ₂fe ₁₇n _xmagnetic.The method is mainly suitable for preparing isotropism magnetic, and the difficult point of the method is mainly the anti-oxidation problem powder metallurgic method (PM) of Sm-Fe alloy powder in the separation of product and separation process: alloy raw material → melting → homogenizing processing → coarse crushing → ball milling powder process → nitrogenize → fine grinding → Sm of certain proportioning ₂fe ₁₇n _xmagnetic.

Powder metallurgic method (PM): alloy raw material → melting → homogenizing processing → coarse crushing → ball milling powder process → nitrogenize → fine grinding → Sm of certain proportioning ₂fe ₁₇n _xmagnetic.Powder metallurgic method can produce high-performance anisotropic Sm ₂fe ₁₇n _xmagnetic, because the remanent magnetism of anisotropic magnet powder, magnetic energy product are far above isotropism magnetic, has better application prospect.The method shortcoming need to be carried out long high temperature homogenizing annealing to the alloy of melting, and because the cooling rate of induction melting water cooled copper mould casting process is slower, solidified superalloy is organized thick, and ingot structure component distributing is inhomogeneous; Due to L+Fe → Sm ₂fe ₁₇the feature of peritectic reaction, not exclusively, there is more α-Fe and rich Sm phase in reaction in alloy.For obtaining more Sm ₂fe ₁₇phase constitution, changes incomplete peritectic reaction alloy structure into Sm ₂fe ₁₇phase, must be through the long-time homogenizing processing of high temperature (1020 ° about C), generally reaches and about 20 hours, just can reach good effect.In addition, in pulverizing process, alloy is not necessarily along intercrystalline cracking, and the part Sm-Fe-N powder particle of acquisition may be made up of polycrystalline, and due to grain orientation difference, this part powder particle does not possess anisotropy yet.

Hydrogen crush method (HDDR): the hydrogen treat → nitrogenize → Sm of foundry alloy melting → homogenizing annealing → coarse crushing → HDDR process ₂fe ₁₇n _xmagnetic.HDDR method is through hydrogenation, disproportionation decomposition, dehydrogenation chemical combination process again, with refinement Sm by the foundry alloy through homogenizing processing ₂fe ₁₇crystal grain, via nitride makes the isotropism magnetic of high-coercive force.

Quick quenching technique (RQ): foundry alloy melting → fast quenching becomes strip (amorphous state) → crystallization processing (nanocrystal) → fragmentation, ball milling powdered.Utilize and in Sm-Fe alloy, add a small amount of Co, Zr, B respectively to improve Sm ₂fe ₁₇n _xcurie temperature, refinement Sm ₂fe ₁₇crystal grain and fast quenching thin strap are decrystallized, improve Sm by tiny α-Fe phase exchange-coupling interaction in fast quenching thin strap ₂fe ₁₇n _xthe remanent magnetism of magnetic, has obtained the isotropism magnetic that remanent magnetism, magnetic energy product are all better than other methods such as HDDR method so far.

Powder metallurgic method can be made high-performance anisotropic magnetic, but because ingot casting needs long homogenizing annealing processing, has hindered powder metallurgic method applying in suitability for industrialized production, and the key of restriction the method development is Sm ₂fe ₁₇alloy fabrication portion.Compared with other method, quick quenching technique has been shown good development prospect, and at present report application quick quenching technique has been made isotropism Sm-Fe-N magnetic, if can make anisotropic magnet powder, and will be for further improving remanent magnetism from now on and magnetic energy product creates favorable conditions.

Summary of the invention

The object of the present invention is to provide a kind of method of utilizing fast melt-quenching to prepare Sm-Fe-N anisotropic magnet powder, by controlling copper roller rotating speed, melt jet gas pressure, jet size, melt temperature, bath composition in rapid solidification, to control the cooling rate of melt and the thickness of rapid hardening slab, reach and obtain rapid hardening strip Sm ₂fe ₁₇principal phase is the brilliant target of arranging of fine columnar, column crystal substantially unanimously orientation, perpendicular to rapid hardening slab surface, by further crystallization processing, fragmentation, nitrogenize, fine grinding, obtain anisotropy Sm-Fe-N magnetic and the anisotropic bonded magnet of the consistent orientation of magnetocrystalline direction of easy axis in powder particle again.

The technological process that the present invention prepares Sm-Fe-N magnetic is: raw material are selected and proportioning → vacuum induction melting (alloy melt preparation) → fast quenching (control of rapid solidification parameter, the control of slab thickness) → alloy structure analysis → tiny Sm ₂fe ₁₇the nearly consistent orientation of column crystal rapid hardening slab → coarse crushing → heat treatment (Sm ₂fe ₁₇further crystallization) → fragmentation → nitrogenize → fine grinding → anisotropy Sm-Fe-N magnetic → detection powder magnetic property.The Sm-Fe-N magnetic making has obvious anisotropic character, and with the comparison of isotropism sample, after orientation, remanent magnetism improves more than 20%.

Technical process of the present invention:

(1) by Sm, Fe batching, can add a small amount of Co, V, Zr, B, by Sm ₂(Fe _1-xm _x) ₁₇molecular formula batching, M is one or more in Co, V, Zr, B, and every kind of atomic percent that replaces Fe is not more than 5%, and because Sm easily volatilizees, it is certain excessive to have, and generally adds amount of calculation 18% ~ 35%.Application high temperature induction melting alloy, melted alloy flows on the copper roller of rotation and is rapidly solidificated into strip, by controlling rotating speed (4 ~ 15m/s), jet size (wide 0.2 ~ 0.65mm), melt jet gas pressure gas pressure (0.5 ~ 1.5atm), the melt temperature (1520-1570 ° of C) of copper roller, obtain Sm ₂fe ₁₇be mutually the strip tissue of the brilliant nearly parallel distribution of fine columnar, strip thickness 0.1 ~ 0.4mm.

(2) applying electronic microscope carries out observation analysis to strip cross section and determines whether to have formed columanar structure; Applying X-ray diffraction analysis determines whether rapid hardening strip main phase is organized is Sm ₂fe ₁₇phase.

(3) qualified rapid hardening slab carry out coarse crushing to 1 ~ 5mm, further crystallization and thermal treatment under 700 ~ 800 ° of C high-purity argon gas protective atmospheres, promotes atom diffusion, to make Sm ₂fe ₁₇phase degree of crystallinity is more complete.

(4) fragmentation: under application benzinum media protection or high-purity argon gas protective medium, Sm-Fe alloy powder is crushed to below 320 orders so that in nitridation process N atom to diffusion inside.

(5) nitrogen treatment: Sm-Fe alloyed powder is at High Purity Nitrogen or NH ₃and H ₂mixed atmosphere in carry out nitriding, nitriding gas pressure is at 0.1 ~ 1.0MPa, 400 ~ 500 ° of C of nitriding temperature, nitridation time 3 ~ 5 hours.

(6) fine grinding: taking benzinum as ball-milling medium, ratio of grinding media to material is 4:1 ~ 30:1, ball milling 3 ~ 20 hours.

(7) dry and sample preparation.After ball milling is good, discharging normal-temperature vacuum is dry, obtains anisotropy Sm-Fe-N magnetic.To dust sampling, using AB glue as binding agent, under 2T magnetic field, orientation is solidified preparation measurement sample size application vibrating specimen magnetometer (VSM) is measured powder magnetic property.

The invention has the advantages that: the Sm-Fe alloy rapid hardening slab even tissue of acquisition, does not need long high temperature homogenizing annealing processing; Due to tiny Sm ₂fe ₁₇column crystal, perpendicular to the nearly consistent orientation in rapid hardening slab surface, as raw material, can be prepared anisotropy Sm-Fe-N magnetic.

Brief description of the drawings

Fig. 1. perpendicular to columanar structure's structure (not corroding) of copper roller, the main Sm of light gray form and aspect in figure ₂fe ₁₇column crystal, the white that intergranular distributes is rich Sm phase mutually

Fig. 2. the XRD analysis of rapid hardening slab, from X-diffraction, has mainly formed Sm ₂fe ₁₇phase, also has rich Sm phase---SmFe in addition ₃

Embodiment

Embodiment 1

The pure iron that is 99.9% by purity, rare-earth Sm are raw material, Fe rod are cleaned out, by Sm ₂fe ₁₇batching because Sm easily volatilizees, adds 22% on the basis of amount of calculation., the Sm preparing, Fe raw material are put into the Magnesia crucible of vacuum induction melting furnace, close stove evacuation, when vacuum degree reaches 0.01Pa, start heating, be heated to approximately 700 ° of C, be filled with 0.05MPa high-purity argon gas (purity is 99.999%), along with the rising of temperature, Sm first melts completely, continues to heat Fe after 3 minutes and melts completely, at approximately 1540 ° of C of temperature, insulation refining poured in water cooled copper mould after 3 minutes, coolingly in stove more than 30 minutes took out ingot casting.Then in the quartz ampoule of rapid hardening slab preparation facilities, under vacuum condition, induction heating melts again, under the effect of 0.8 atmospheric pressure expulsion pressure, be poured into roll surface speed on the copper roller of 5m/s High Rotation Speed, form about 0.24mm thickness band, strip interface is sampled in observed under electron microscope and formed column crystal, prove mainly to have formed Sm with XRD analysis ₂fe ₁₇phase.The sheet that the strip of this rapid hardening is broken into 1 ~ 5mm, packs magazine into, puts into quartz ampoule, first with being evacuated to 4 × 10 ^-3pa, is filled with high-purity argon gas (purity is 99.9995%), and quartz ampoule is put into stove, after 1 hour, takes out boiler tube 730 ° of C insulations, takes out alloy sheet after cool to room temperature.Under high-purity argon gas protective medium, cross 500 mesh sieves with the fragmentation of steel alloy mortar; Pack the powder after sieving into magazine, put into quartz ampoule, pumping high vacuum to 4 × 10 ^-3pa, closes extraction valve, is filled with high pure nitrogen, and nitrogen pressure reaches 0.5MPa, puts into stove nitriding, and nitriding temperature is 480 ° of C, is incubated after 5 hours, takes out boiler tube, takes out powder after cool to room temperature; Taking ratio of grinding media to material as 30:1, benzinum is ball-milling medium, charging ball milling, ball milling is discharging precipitation after 9 hours, and unnecessary benzinum is reclaimed, and slip normal-temperature vacuum is dry; By the powder after dried, using AB glue as binding agent, under 2T magnetic field, the curing vibrating specimen magnetometer (VSM) of preparing of orientation is measured sample, is measured and is obtained powder magnetic property by VSM.Orientation characteristic is: H _ci2113Oe, Br0.89T; Magnetic field orientating (same sex sample) performance is not: H _ci2230Oe, Br0.7T.

Embodiment 2

The pure iron that is 99.9% by purity, rare-earth Sm, Co, V are raw material, Fe rod are cleaned out, by Sm ₂(Fe _0.94co _0.02v _0.04) ₁₇batching because Sm easily volatilizees, adds 25% on the basis of amount of calculation.Preparation process is similar to Example 1, first uses vacuum induction melting, water cooled copper mould cooling, obtains alloy cast ingot.Then in the quartz ampoule of rapid hardening slab preparation facilities, under vacuum condition, induction heating melts again, under the effect of 0.8 atmospheric pressure expulsion pressure, be poured into roll surface speed on the copper roller of 7m/s High Rotation Speed, form about 0.16mm thickness band, strip interface is sampled in observed under electron microscope and formed column crystal, prove mainly to have formed Sm with XRD analysis ₂fe ₁₇phase.The strip of this rapid hardening is broken into the sheet of 1 ~ 5mm, the then lower 780 ° of C insulation of high-purity argon gas atmosphere 0.5 hour, with further crystallization treatment S m ₂fe ₁₇phase.Alloy sheet is broken into and below 500 orders, carries out nitrogen treatment with steel alloy mortar under high-purity argon gas protective medium; Nitrogen treatment uses high pure nitrogen pressure 0.2MPa, and nitriding temperature is 490 ° of C, is incubated 5 hours; Ball milling, dry, sample preparation, with embodiment 1, obtain powder magnetic property, and orientation characteristic is: H _ci4980Oe, Br0.83T; Magnetic field orientating performance is not: H _ci5260Oe, Br0.66T.

Embodiment 3

The pure iron that is 99.9% by purity, rare-earth Sm, V are raw material, Fe rod are cleaned out, by Sm ₂(Fe _0.95v _0.05) ₁₇batching because Sm easily volatilizees, adds 23% on the basis of amount of calculation.Preparation process is similar to Example 1, first uses vacuum induction melting, water cooled copper mould cooling, obtains alloy cast ingot.Then in the quartz ampoule of rapid hardening slab preparation facilities, under vacuum condition, induction heating melts again, under the effect of 0.8 atmospheric pressure expulsion pressure, be poured into roll surface speed on the copper roller of 6m/s High Rotation Speed, form about 0.19mm thickness band, strip interface is sampled in observed under electron microscope and formed column crystal, prove mainly to have formed Sm with XRD analysis ₂fe ₁₇phase.The strip of this rapid hardening is broken into the sheet of 1 ~ 5mm, the then lower 780 ° of C insulation of high-purity argon gas atmosphere 0.5 hour, with further crystallization treatment S m ₂fe ₁₇phase.Alloy sheet is broken into and below 320 orders, carries out nitrogen treatment with steel alloy mortar under high-purity argon gas protective medium; Use NH ₃and H ₂the mist of (volume ratio 3:7) carries out nitriding, and gas pressure is 0.12MPa, and nitriding temperature is 450 ° of C, is incubated 3.5 hours; Ball milling, dry, sample preparation, with embodiment 1, obtain powder magnetic property, and orientation characteristic is: H _ci3920Oe, Br0.85T; Magnetic field orientating performance is not: H _ci4130Oe, Br0.68T.

Embodiment 4

The pure iron that is 99.9% by purity, rare-earth Sm, Co, V are raw material, Fe rod are cleaned out, by Sm ₂(Fe _0.94co _0.02v _0.03) ₁₇batching because Sm easily volatilizees, adds 25% on the basis of amount of calculation.Save vacuum induction melting, directly in rapid hardening slab preparation facilities inducing melting alloy spray to roll surface speed on the copper roller of 15m/s High Rotation Speed, pouring nozzle width 0.65mm, spray high-purity argon gas pressure 1atm, form about 0.3mm thickness band, detect microscopic structure and the phase composition of rapid hardening slab, to obtain tiny Sm ₂fe ₁₇the microscopic structure that column crystal is arranged.The strip of this rapid hardening is broken into the sheet of 1 ~ 5mm, the then lower 750 ° of C insulation of high-purity argon gas atmosphere 1 hour, with further crystallization treatment S m ₂fe ₁₇phase.By alloy sheet taking benzinum as medium, ratio of grinding media to material is 8:1, charging ball milling 1 hour, then discharging, precipitation, by slime vacuum air drying, obtain alloy powder; At NH ₃and H ₂in the mist of (volume ratio 3:7), carry out nitrogen treatment, gas pressure is 0.12MPa, and nitriding temperature is 450 ° of C, is incubated 3.5 hours; After nitrogenize, powder ball-milling technology is that ratio of grinding media to material is 8:1, Ball-milling Time 12 hours, and then discharging, precipitation, by slime vacuum air drying, are measured powder magnetic property with embodiment 1 sample preparation, and result is: orientation characteristic is: H _ci4580Oe, Br0.84T; Magnetic field orientating performance is not: H _ci4720Oe, Br0.67T.

Claims

1. a preparation method for Sm-Fe-N anisotropic magnet powder, is characterized in that: technological process is: the control of alloy melt preparation → rapid solidification parameter, the control of slab thickness → tiny Sm ₂fe ₁₇rapid hardening slab → crystallization processing → coarse crushing → nitrogenize → fine grinding → anisotropy Sm-Fe-N magnetic of the nearly consistent orientation of column crystal, concrete preparation process is as follows:

(1) by Sm, Fe batching, application high temperature induction melting alloy, melted alloy flows on the copper roller of rotation and is rapidly solidificated into strip, by controlling the wide 0.2 ~ 0.65mm of rotating speed 4 ~ 15m/s, jet size, melt jet gas pressure 0.5 ~ 1.5atm, the melt temperature 1520-1570 ° C of copper roller, obtain Sm ₂fe ₁₇be mutually the strip tissue of the brilliant nearly parallel distribution of fine columnar, strip thickness 0.1 ~ 0.4mm;

(2) applying electronic microscope carries out observation analysis to strip cross section and determines whether to have formed columanar structure; Applying X-ray diffraction analysis determines whether rapid hardening strip main phase is organized is Sm ₂fe ₁₇phase;

(3) qualified rapid hardening slab carry out coarse crushing to 1 ~ 5mm, further crystallization and thermal treatment under 700 ~ 800 ° of C high-purity argon gas protective atmospheres, promotes atom diffusion, to make Sm ₂fe ₁₇phase degree of crystallinity is more complete;

(4) fragmentation: under application benzinum media protection or high-purity argon gas protective medium, Sm-Fe alloy powder is crushed to below 320 orders so that in nitridation process N atom to diffusion inside;

(5) nitrogen treatment: Sm-Fe alloyed powder is at High Purity Nitrogen or NH ₃and H ₂mixed atmosphere in carry out nitriding, nitriding gas pressure is at 0.1 ~ 1.0Mpa, 400 ~ 500 ° of C of nitriding temperature, nitridation time 3 ~ 5 hours;

(6) fine grinding: taking benzinum as ball-milling medium, ratio of grinding media to material is 4:1 ~ 30:1, ball milling 3 ~ 20 hours;

(7) dry and sample preparation: after ball milling is good, discharging normal-temperature vacuum is dry, obtains anisotropy Sm-Fe-N magnetic.

2. the preparation method of a kind of Sm-Fe-N anisotropic magnet powder according to claim 1, is characterized in that: when batching, Sm is total excessive in 18% ~ 35%.

3. the preparation method of a kind of Sm-Fe-N anisotropic magnet powder according to claim 1, is characterized in that: in the time of preparation rapid hardening strip, cooling copper roll surface speed is at 4 ~ 15m/s.

4. the preparation method of a kind of Sm-Fe-N anisotropic magnet powder according to claim 1, is characterized in that: add a small amount of Co, V, Zr, B, by Sm ₂(Fe _1-xm _x) ₁₇molecular formula batching, M is one or more in Co, V, Zr, B, every kind of atomic percent that replaces Fe is not more than 5%.