CN104508764A - Permanent magnet material - Google Patents

Permanent magnet material Download PDF

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CN104508764A
CN104508764A CN201380007406.6A CN201380007406A CN104508764A CN 104508764 A CN104508764 A CN 104508764A CN 201380007406 A CN201380007406 A CN 201380007406A CN 104508764 A CN104508764 A CN 104508764A
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crystal grain
phase
magnetic
grain
face
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牛尾二郎
山本浩之
北川功
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Hitachi Ltd
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Hitachi Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C2202/00—Physical properties
    • C22C2202/02—Magnetic

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)
  • Powder Metallurgy (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)

Abstract

In rare-earth permanent magnets, it is difficult to achieve both high magnetization and high retentivity. The present invention provides a rare-earth magnet material in which reduction in coercivity is minimized while maintaining high magnetization by varying the thickness of a nonmagnetic phase formed on the surface of each main-phase crystal grain depending on the position of the crystal grain surface, and thereby minimizing the amount of the nonmagnetic phase while minimizing reduction in coercivity.

Description

Permanent magnet material
Technical field
The present invention relates to the material for permanent magnet.
Background technology
The representatively rare-earth permanent magnet of property permanent magnet, the tissue of such as neodium magnet, by accounting for the most principal phase (Nd of ferromagnetic material 2fe 14b) non-magnetic phase (principal component is Nd-Cu alloy, also known as making Grain-Boundary Phase) produced with the crystal boundary of main phase grain is formed.Principal phase is the material of the character reason presented as permanent magnet, and permanent magnet, in commercial Application, has two important class intensity, namely both high magnetization and high-coercive force.In addition, can think, non-magnetic phase (Grain-Boundary Phase), between main phase grain, (crystal boundary) exists, and by coating crystal grain, blocks the interaction between main phase grain, more improves coercive force.
As the background technology of the art, there is JP 2012-234985 publication (patent documentation 1).In this publication, to provide " have high magnetization concurrently and remain the manufacture method with the NdFeB magnet of high-coercive force ", as problem, " manufacture method of this magnet comprises: make containing Nd 2fe 14operation, the operation above-mentioned non-magnetic phase being heated to the above temperature of its fusing point that the magnetic tissue of B phase contacts with non-magnetic phase and make above-mentioned non-magnetic phase in above-mentioned magnetic tissue, carry out the operation of grain boundary decision; Here containing above-mentioned Nd 2fe 14the magnetic tissue of B phase be the nanometer crystalline particle of particle diameter 10 ~ 300nm at least partially ".In addition, also describe that " in the method, during the grain boundary decision of non-magnetic phase between magnetic tissue, do not form the Grain-Boundary Phase of segregation, Grain-Boundary Phase evenly surrounds magnetic tissue, improves coercive force.In addition, due to segregation non-in Grain-Boundary Phase, therefore along with suppressing the amount (volume ratio in magnet) of Grain-Boundary Phase, and then the amount (volume ratio in magnet) of magnetic tissue can be improved, bringing the height of magnet to magnetize ".
Prior art document
Patent documentation
Patent documentation 1: JP 2012-234985 publication
Summary of the invention
The problem that the present invention will solve
In patent documentation 1, the non magnetic Grain-Boundary Phase of all parts, improve the coercive force of magnet and have equivalent effect, it is formed as prerequisite with Grain-Boundary Phase in crystalline particle surface uniform.Therefore, in order to improve coercive force, must increase the amount of the non-magnetic phase in ferromagnetic material, consequently coercive force improves, but has high magnetized principal phase density and reduce, and magnetization reduces.Otherwise when being magnetized to object with height, when improving the density of principal phase, the density of non-magnetic phase reduces, and becomes insufficient by blocking of the intergranular interaction caused by non-magnetic phase, produces the problem that coercive force reduces.
At this, the invention provides rare earth magnet material, by the thickness of the non-magnetic phase in the formation of main phase grain surface, changing, while make coercitive reduction reach Min., while do one's utmost to reduce non magnetic phasor by changing the position of grain surface; Limit keeps high magnetization, and limit is suppressed to Min. coercitive reduction.
For solving the means of problem
In order to solve above-mentioned problem, the invention provides the permanent magnet material with ferromagnetic material structure organization, this ferromagnetic material tissue is by the thickness of the non-magnetic phase on grain surface parallel for the easy axle with magnet crystal grain, thicker than the thickness of the non-magnetic phase on the grain surface vertical with easy axle and formed.
The effect of invention
According to the present invention, provide rare-earth permanent magnet material, it is imported by necessary MIN non-magnetic phase, the height magnetization that principal phase is had with improve effect by the coercive force of non-magnetic phase and reach balance.
Problem other than the above, formation and effect, come clear and definite by the explanation of following embodiment.
Accompanying drawing explanation
Fig. 1 is the example of the tissue of neodymium permanent magnet.
Fig. 2 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 3 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 4 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 5 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 6 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 7 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 8 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Fig. 9 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Figure 10 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Figure 11 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Figure 12 is the example that non-magnetic phase imports during position is inquired into the structure of the simulation model used.
Figure 13 is the example of the flow chart of rare-earth sintered magnet manufacturing process.
Figure 14 is in the sintering process of magnet, non-magnetic phase on the face being parallel to easy axle, than the example of the thick state diagram that vertical face is formed.
Embodiment
Below adopt accompanying drawing that embodiment is described.
Embodiment 1
In the present embodiment, about the neodium magnet material (Nd of rare-earth permanent magnet representative materials 2fe 14b), import non-magnetic phase, when improving coercive force, the discussion example the most effective non-magnetic phase being imported to position and thickness is illustrated.
Fig. 1 is the example as the tissue of the neodium magnet of object in the present embodiment.
Neodium magnet 100 has: principal phase (Nd 2fe 14b) crystal grain 101, non magnetic Grain-Boundary Phase (Nd-Cu alloy) 102.Each crystal grain 101 has easy axle 103, and this easy axle is the stabilising direction of spontaneous magnetization in zero magnetic field.
One of coercive force decisive factor of neodium magnet, can think the generation (generation core) of the magnetization inversion starting point caused by defect contained in ferromagnetic material.If whole magnet is monocrystalline, then the concentration of defect is low, but is polycrystal at the common neodium magnet of sintering circuit manufacture, there is number of drawbacks structure in ferromagnetic material.Wherein, the reason causing large coercive force to reduce, can think the defect that the directional bias of easy axle produces.
1 crystal grain, major part is by Nd 2fe 14b monocrystalline (regular crystal) is formed, and the c-axis of crystallization is easy axle.In the manufacturing process of neodymium sintered magnet, in order to improve the performance as permanent magnet, in the forming process before magnet sintering, applying directional magnetic field, making crystal grain in addition directed, shaping at magnetic direction.Consequently, exceed the easy axle of the number of die of whole 90%, with the deviation of about ± 15 °, align in equidirectional.
But from close to the directional magnetic field direction of 90 °, the crystal grain tilt with easy axle also exists slightly.At intercrystalline, by magnetic exchange interaction, produce the power that easy axle is being alignd in the same way.Therefore, from directional magnetic field direction, there is the crystal grain of the easy axle tilted close to 90 °, produce and make the crystal grain of surrounding magnetize the effect of tilting from directional magnetic field direction.The easy axle in directional magnetic field direction tilts, and from 0 ° to more close to 45 °, more easily produces magnetization inversion.That is, by the effect with the rightabout magnetic field of directional magnetic field, when making magnet generation magnetization inversion, from directional magnetic field direction, having the crystal grain close to 90 ° of easy axles of inclination, is become the initial reason generating magnetization inversion core.
From the viewpoint of easy axle orientation, in order to improve the coercive force of permanent magnet, there are following two methods: (1) makes the easy axle of crystal grain as much as possible align in directional magnetic field direction; (2) between crystal grain, form non magnetic Grain-Boundary Phase, reduce the power (exchange interaction) of aliging with the direction of magnetization in the adjacent crystal grain direction of magnetization.In the present embodiment, about the latter (2), inquired into for the formation of the position on the grain surface of non-magnetic phase raising is coercitive.
When inquiring into, adopt the simulation of finite element LLG (Landau-Lifshitz-Gilbert) method.In LLG method, think that magnet is the aggregate of the small rotation of interaction containing exchange interaction, derotation equation of motion.Only many kinds of parameters presents magnetization inversion with high accuracy, and the magnetic characteristic of the ferromagnetic materials such as coercive force adopts simulation to be resolved.When realistic simulation, apply to rotate to the micro volume (mesh) of partition space, calculate these interaction.In the present embodiment, owing to having made the mesh coincide with magnet shape, therefore easy Finite element method mesh can be adopted, carry out the simulation of LLG method.In addition, actual grain shape, can be assumed to simple cube model.
Fig. 2 is the example of the cube model 200 of crystal grain.It is cubical while supposition is parallel with c-axis.Two squares on the surface perpendicular with cubical c-axis are c face, four squares on the surface parallel with c-axis are ab face.Can think: c face or ab mask have the non-magnetic phase 203 of thickness 3nm, and easy axle does not have non-magnetic phase in 1 crystal grain of directional magnetic field direction orientation, and contact with tilt 2 crystal grain of 90 ° of easy axle and directional magnetic field direction.
The easy direction of principal axis of these 2 crystal grain is identical.Also can think that the direction of easy axle is in addition directed on the contrary, but also can think that these 2 crystal grain are on the impact of surrounding, cancel each other.Easy direction of principal axis due to 2 crystal grain is identical, has the crystal grain of directed easily axle, make the power of its magnetization inversion stronger in directional magnetic field direction.This structure is as the beginning nuclear model of ferromagnetic material magnetization inversion.Evaluate import the grain surface position of non-magnetic phase and the configuration relation of ambient particles to coercitive impact time, can think, adopt this model can obtain sufficient opinion.Adopt this model, only when a part for crystal grain contact-making surface forms non-magnetic phase, can determine, to coercitive raising, there is effective especially forming position.
Fig. 3 illustrates the crystalline particle 1 (301) of the easy axle 302 with directional magnetic field direction, the crystalline particle 2 (303) with the different easy axle 304 and 306 in direction in 90 ° from directional magnetic field and crystalline particle 3 (305), by crystalline particle 1 (301) without the c face of non-magnetic phase and the configuration be connected without the ab face of non-magnetic phase of crystalline particle 1.Crystalline particle 2 is identical with the direction of the easy axle of crystalline particle 3.
Fig. 4 shows the configuration of the ab face importing non-magnetic phase 407 of only crystalline particle 1 in intercrystalline two interfaces of Fig. 3.
Fig. 5 shows the configuration of only c face importing non-magnetic phase 507 in intercrystalline two interfaces of Fig. 3.
Fig. 6 show the easy axle 602 with directional magnetic field direction crystalline particle 1 (601), from the crystalline particle 2 (603) of different easy axles 604 and 606 and the crystalline particle 3 (605) with directional magnetic field direction in 90 °, by the configuration be connected with the ab face adjacent without non-magnetic phase of crystalline particle 1 (601).Crystalline particle 2 is identical with the easy direction of principal axis of crystalline particle 3.
Fig. 7 shows the configuration importing non-magnetic phase 707 at intercrystalline whole interface (ab face) of Fig. 6.
Fig. 8 shows the crystalline particle 1 (801) of the easy axle 802 with directional magnetic field direction, from the crystalline particle 2 (803) of different easy axles 804 and 806 and the crystalline particle 3 (805) with directional magnetic field direction in 90 °, with the configuration of crystalline particle 1 (801) by being connected without the ab face parallel to each other of non-magnetic phase.
Fig. 9 shows the configuration importing non-magnetic phase 907 in the whole interface of the intercrystalline of Fig. 8 (ab face).
Figure 10 shows the crystalline particle 1 (1001) of the easy axle 1002 with directional magnetic field direction, from the crystalline particle 3 (1005) of crystalline particle 2 (1003) of different easy axles 1004 and 1006 with directional magnetic field direction in 90 °, with the configuration of crystalline particle 1 (1001) by being connected without the c face of non-magnetic phase.
Figure 11 shows the configuration importing non-magnetic phase 1107 at intercrystalline whole interface (c face) of Figure 10.
The simulation of finite element LLG method is carried out to above-mentioned each configuration, draws demagnetizing curve, determine coercive force.In this, as roughly standard, determine to import position to raising the most effective coercitive non-magnetic phase.
The parameter used during simulation, cubical 1 edge lengths is 100nm, the thickness of the non-magnetic phase of crystal boundary is 3nm, finite element mesh size is: it is that in 3.125nm, volume, full-size is 3.125nm that cube crest line size is full-size on 1.5625nm, face to the maximum.In addition, as the material behavior of neodium magnet, uniaxial magnetic anisotropy energy is adopted to be 4.5MJ/m 3, saturation magnetization be 1.61T, exchange rigidity constant be 1.25 × 10 -11j/m, damping coefficient are 0.1.Non-magnetic phase, magnetic can be regarded as and equals vacuum (uniaxial magnetic anisotropy energy, saturation magnetization, exchange rigidity constant are all zero).Apply the external magnetic field of 5.5MA/m at the easy direction of principal axis of the central particles of 3 particle agglomeration, make the easy axle of 3 crystal grain directed.
Then, external magnetic field is reduced, calculate demagnetizing curve.External magnetic field, from 5.5MA/m, with the stride of 500kA/m, is reduced to-1MA/m; From-1MA/m, with the stride of 100kA/m, be reduced to-4.5MA/m.To each external magnetic field, the time variations between 0.5ns when calculating magnetization.After applying external magnetic field, the magnetization of 0.5ns, to external magnetic field mapping, draws demagnetizing curve, magnetizes the absolute value of the external magnetic field value (negative value) when reaching zero as coercive force.
The coercive force obtained is summarized in [table 1].
Table 1
Coercive force, is configured to minimum with Fig. 3, and being configured to of Figure 11 is maximum.Permanent magnet, particularly arranges neodium magnet coercitive key element, is commonly considered as the part that coercive force in whole ferromagnetic material is minimum.The magnetization inversion started in little part, because being easily extended to whole magnet, therefore the coercive force of magnet, determined by the coercive force of initial magnetization inversion beginning.
Therefore, in order to improve the coercive force of neodium magnet, the part that coercive force is minimum must be found out, improving the coercive force of this part.That is, in the crystal grain forming ferromagnetic material, by improving the coercive force with larger coercitive crystal grain further, can improve the coercive force with minimum coercitive crystal grain, it improves relevant with the coercive force of whole magnet.
Here, the object importing non-magnetic phase is that the coercive force improving coercitive minimum value, particularly coercive force little Fig. 3 and secondary little Fig. 6 configuration causes concern.When non-magnetic phase only imports at any place in c face or ab face, the coercive force of Fig. 3 configuration, there is the small difference of 0.1MA/m in c face and ab face, but import non-magnetic phase in ab face, then coercive force raising is larger.
In addition, in the arrangement of figure 6, Jingjing interface is only ab face, and by importing non-magnetic phase to interface, then coercive force brings up to 2.7MA/m greatly from 1.3MA/m.From above discussion, in order to improve coercitive minimum, improve the coercive force of whole magnet, being suitable for importing the face of non-magnetic phase is c face and ab face when being compared, and known importing ab face presents best effect.Non-magnetic phase is thicker, and intercrystalline interaction is truncated the more, and coercive force improves the more.But in order to improve coercive force, the non-magnetic phase thickening ab face is effective.
On the other hand, the non-magnetic phase in c face need not have identical thickness with the non-magnetic phase in ab face, even if thinner than the non-magnetic phase in ab face, or does not have completely, little on coercitive impact.In addition, by making the non-magnetic phase in c face thinner than the non-magnetic phase in ab face, the principal phase density organized as high magnetized magnetic can be improved.Consequently, compared with when all forming uniform non-magnetic phase with all faces of abc, magnetization when coercive force improves reduces can suppress most little.
The conclusion of the present embodiment is, even if the situation of the particle of other different sizes and the thickness of different non-magnetic phases, is suitable for too.The conclusion of the present embodiment is, compared with the non-magnetic phase in c face, and the non-magnetic phase in ab face, large on coercitive impact, be conclusion qualitatively.Even if the cubical size that simulation adopts, or the thickness of the non-magnetic phase of crystal boundary is different, but the conclusion qualitatively of finite element LLG method simulation is constant, generally known.The geometry factor of the shape of particle, the easily simulation model such as the orientation of axle, the presence or absence of non-magnetic phase, determine the qualitative results of simulation, the size of particle or the thickness etc. of non-magnetic phase, have impact to coercive force and quantitative result such as magnetization size etc., but on result qualitatively without impact.
The embodiment that neodium magnet shown in the present embodiment relates to, to other rare-earth permanent magnet material (adding the neodium magnet etc. of dysprosium), can carry out same simulation, obtain same conclusion.
Embodiment 2
In the present embodiment, be not the whole crystal boundary faces to inquiring in embodiment 1, but when being only coated to a part and importing non-magnetic phase, the example contributing to coercive force raising is illustrated.
Intercrystalline crystal boundary face (such as, the foursquare face that the particle 1 (301) of Fig. 3 is connected with particle 2 (303)) coercive force when only a part imports non-magnetic phase, adopt the simulation of finite element LLG method, to inquire into equally with above-described embodiment 1.In the present embodiment, as simulation model, consider that 2 cube crystal grain have the structure of foursquare and connection.The part in foursquare crystal boundary face, changes the ratio using non-magnetic phase coating, calculates, compares coercive force.
Figure 12 shows the crystalline particle 1 (1201) of the easy axle 1202 with directional magnetic field direction, has the configuration be connected with the c face of crystalline particle 1 (1201) from the crystalline particle 2 (1203) of the different easy axle 1204 in direction in 90 °, directional magnetic field direction.1 edge lengths of cube crystal grain is 100nm.Crystal boundary (c face) between two crystalline particles 1 and 2 (1201 and 1204) only part imports non-magnetic phase 1205.The shape of this non-magnetic phase is, 1 limit is 100nm, another 1 limit is x × 100nm (0 < x < 1), thickness is the cuboid of 3nm.Ratio (x)=0.0 of non-magnetic phase, 0.1,0.5,0.9,5 class such as 1.0 time simulate.The neodium magnet characteristics such as the finite element mesh size adopted and input power parameter are identical with embodiment 1.
To the demagnetizing curve of each x value, adopt the simulation of finite element LLG method to be calculated, determine coercive force.The results are summarized in [table 2].
Table 2
Coercive force alters a great deal because of the value of x.The coercive force of neodium magnet, it is generally acknowledged the difference of 0.1MA/m, can produce significant difference, when x is more than 0.1, can present significant coercive force to improve, when x is 1.0, slightly exceed two times when coercive force is zero, x is 0.9, with 1.0 time compared with, slightly reduce, without large difference.But non-magnetic phase is coated to the ratio (minimum is 0.0, is 1.0 to the maximum) on crystalline particle surface, preferably more than 0.1, particularly preferably more than 0.9.
The result of the present embodiment, think the particle of different size and different-thickness non-magnetic phase too.Adopt the simulation of finite element LLG method, the geometry structure of simulation model, i.e. only the orientation of form, the easily axle of crystal grain and x (non-magnetic phase is coated to the ratio on its surface), determine coercitive height.According to the size of crystal grain and the thickness of non-magnetic phase, coercitive absolute value changes, and changes coercitive method with by x, does not have large difference.
In the present embodiment, provide the embodiment relating to neodium magnet, but other rare-earth permanent magnet material (adding the neodium magnet etc. of dysprosium), can simulate equally, obtain same conclusion.
Embodiment 3
In the present embodiment, the example ab face of ferromagnetic material crystal grain optionally being imported to the neodium magnet manufacture method of non-magnetic phase is illustrated.
Figure 13 is in the present embodiment as the example of the flow chart of the manufacturing process of the neodymium sintered magnet of object.The raw alloy 1301 of neodymium sintered magnet, adopts common ingot casting or Strip sheet casting method to make.Secondly, at raw alloy pulverizing process 1302, making average grain diameter is the raw material alloy powder of about several μm.This operation comprises: making raw alloy brittle by inhaling hydrogen phenomenon, the average crystal boundaries of about hundreds of μm being carried out to the operation of coarse crushing, and the alloy coarse crushing adopts injecting type grinder device etc., carry out fine powder be broken to average grain diameter number μm about operation.Secondly, directional magnetic field is applied, while carry out pressurize shaping 1303 to raw material alloy powder limit.The formed body made, in the operation of sintering 1304 thereafter, such as, sinters the temperature of 1000 ~ 1100 DEG C.Then, in heat treatment 1305, carry out the heat treatment of about 400 ~ 500 DEG C, the concavo-convex of crystal boundary face of flattening, crystal boundary is flattened cunning, more can improve coercive force.In addition, to the processing that the shape of whole magnet is arranged, and for preventing material oxidation from carrying out the surface treatments such as nickel plating, complete as goods.
In the operation of sintering 1304, first, when being increased to the temperature of about 800 DEG C, raw material alloy powder (crystal grain) starts to grow up, and crystal grain is mainly grown up in c-axis direction, and adjacent crystal grain is formed by connecting by c face mutually.Adopt the temperature of about 800 DEG C, this be due to c-axis direction crystal grain-growth speed than a axle and the axial growth rate of b fast.Keep 1 hour in 800 DEG C, fully increase with the contact area in c face.Then, in 950 ~ 1000 DEG C temperature keep 4 ~ 5 hours, crystallization particle diameter produce certain level wait side's property increase.But, lower than the low temperature of 1000 DEG C, the growth rate in c-axis direction than a axle and b direction of principal axis slightly large, the c face composition of intercrystalline contact area increases more.
Figure 14 is in the sintering process 1304 of Figure 13, is controlled, the example of the state diagram that the non-magnetic phase 1402 that the ab face of neodium magnet crystal grain 1401 is formed is thicker than c face by above-mentioned temperature.The composition (Nd-Cu alloy) of non-magnetic phase, the temperature more than 800 DEG C melts, and becomes liquid phase.By shaping 1303 of Figure 13, in the ferromagnetic material of magnet raw meal formed body, crystal grain 1401 is in addition directed in directional magnetic field direction, the easy axle 1403 of most of crystal grain, reaches almost parallel mutually.When sintering beginning, the non-magnetic phase of liquid phase is coated to all surfaces of crystal grain thickly.Control to sinter by said temperature, the growth rate of crystal grain is fast, and crystal grain is grown up in c-axis direction.Crystal grain and adjacent crystal grain, the space become mainly through infiltrating at the non-magnetic phase of the contact of c face, liquid phase is reduced in c face.In addition, in ab face, space residual large between neighboring die, the non-magnetic phase of liquid phase infiltrates.By cooling in this condition, obtain the neodium magnet that the thick crystal grain of the non-magnetic phase non-magnetic phase that is thin, ab face in c face is formed.
As shown in Figure 1, the crystal grain 101 of actual neodium magnet 100 has complicated shape, air spots, and, to easy axle (c-axis) 103, both not exclusively vertical, also not exclusively parallel.The ab face of obtained magnet crystal grain is measured, investigates the ratio be coated to by non-magnetic phase 102.In order to investigate the grain shape of sintered magnet, limit adopts FIB (Focused Ion Beam: focused ion beam) to cut sample, while observe surface with SEM (Scanning Electron Microscopy: scanning electron microscopy), determine 3 dimension shapes of crystal grain.In addition, in order to determine c face and the ab face of crystal grain, to each crystal grain, observing easy axle, carrying out EBSP (ElectronBackscattering Pattern: electron backscattered pattern) and measuring.Adopt shape and easy axle (c-axis) direction of the crystal grain obtained, determine the ratio that the ab face of each grain surface the ab face composition amassed and the area be coated to non-magnetic phase becomes to divide.The small area of grain surface, is projected to a face, b face and c face, determines ab face composition and c face composition, by suing for peace at all surfaces to it, determines ab face composition and the c face composition of grain surface.Known from its result, the crystal grain obtained in the present embodiment, is equivalent to about 90% of the area in ab face, is coated to by non-magnetic phase.C face only its about 20%, be coated to by non-magnetic phase.The average thickness of the non-magnetic phase in ab face is 2.8nm.
In this manufacturing process, at sintering 1304, change the temperature retention time in 950 ~ 1000 DEG C, make the magnet that the average thickness of the non-magnetic phase in ab face is different.The average thickness making non-magnetic phase is 5 kinds of magnet such as 0nm, 3nm, 10nm, 20nm, 30nm.Measure with VSM (VibratingSample Magnetometer: vibrating sample magnetometer), measure the results are summarized in [table 3] of the demagnetizing curve of each magnet.
Table 3
The value of coercive force during formation non-magnetic phase, be 1.1MA/m when average thickness is 3nm, for minimum, any one of 10nm, 20nm, 30nm is 1.3MA/m.And remanent magnetization, best during average thickness 3nm, when thickness increases to 30nm from 10, there is deterioration.Therefore, even if remanent magnetization slightly reduces, when making high-coercive force magnet, magnet non-magnetic phase average thickness still preferred 10 ~ 20nm.Adopt the thickness of more than 30nm, compared with adopting the thickness of below 20nm, coercive force does not change, but magnetization reduces.In addition, for making remanent magnetization extremely not reduce, when making the high magnet of coercive force, non-magnetic phase average thickness is preferably 3nm.Be less than the thin non-magnetic phase of 3nm, can not make in the present embodiment.
The explanation of symbol
The tissue of 100 neodium magnets
101 main phase grains
102 non magnetic Grain-Boundary Phases
The easy axle of 103 magnetization
The cube model of 200 crystal grain
201 crystal grain
The easy axle of 202 magnetization
The coating c face of 203 cube grain surfaces or the non-magnetic phase in ab face
1300 rare-earth permanent magnet material manufacturing processes
1301 raw alloy manufacturing processes
1302 raw material alloy powder manufacturing processes
1303 raw material alloy powder molding procedure
1304 raw material alloy powder sintering circuits
1305 heat treatment steps

Claims (5)

1. permanent magnet material 100, it is characterized in that, in the rare-earth permanent magnet of the easy axle almost parallel orientation mutually of the easy axle of crystal grain and other crystal grain, the easy axle on the surface of relatively above-mentioned crystal grain is coated to the non magnetic Grain-Boundary Phase of parallel face composition, and the non magnetic Grain-Boundary Phase being coated to vertical face composition than relatively above-mentioned easy axle is thick.
2. according to the permanent magnet material described in right 1, it is characterized in that, the thickness that the easy axle of relatively above-mentioned grain surface is coated to the above-mentioned non magnetic Grain-Boundary Phase of parallel face composition is 1 ~ 30nm, further, to be coated to the above-mentioned thickness of non-magnetic phase Thickness Ratio of vertical face composition thin for the easy axle on the surface of relatively above-mentioned crystal grain.
3. according to the permanent magnet material described in right 2, it is characterized in that, the above-mentioned non magnetic Grain-Boundary Phase thickness that the easy axle on the surface of relatively above-mentioned crystal grain is coated to parallel face composition is 10nm.
4. according to the permanent magnet material described in right 1, it is characterized in that, the easy axle on the surface of relatively above-mentioned crystal grain, in all parallel face composition 10 ~ 100% are coated to by non-magnetic phase, and, the easy axle on the surface of relatively above-mentioned crystal grain, vertical face composition is coated to non-magnetic phase with the ratio fewer than its above-mentioned numerical value.
5. according to the permanent magnet material described in right 1, it is characterized in that, in the sintering circuit 1304 of above-mentioned permanent magnet material manufacturing process, after temperature 800 DEG C keeps 1 hour, keep 4 ~ 5 hours in temperature 950 ~ 1000 DEG C and make.
CN201380007406.6A 2013-07-31 2013-07-31 Permanent magnet material Pending CN104508764A (en)

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