CN104752048A

CN104752048A - Production method for sintered neodymium-iron-boron permanent magnets

Info

Publication number: CN104752048A
Application number: CN201310743639.4A
Authority: CN
Inventors: 何叶青; 惠英林
Original assignee: Beijing Zhong Ke San Huan High Tech Co Ltd
Current assignee: Beijing Zhong Ke San Huan High Tech Co Ltd
Priority date: 2013-12-30
Filing date: 2013-12-30
Publication date: 2015-07-01
Anticipated expiration: 2033-12-30
Also published as: CN104752048B

Abstract

Disclosed is a production method for sintered neodymium-iron-boron permanent magnets. The method is a dual-alloy method using master alloy and auxiliary alloy and is characterized in that the grain size of the auxiliary alloy ranges from 0.01 micrometers to 0.1 micrometers. The method includes that quenching auxiliary neodymium-iron-boron powder with total rare earth content obviously lower than master alloy powder and the grain size far less than particle size is added to sintered master neodymium-iron-boron alloy powder with the total rare earth content ranging from 28wt.% to 35wt.% and the average particle size and grain size ranging from 3.0 micrometers to 5.0 micrometers. Grains of Neodymium-iron-boron compact is prevented from growing rapidly, generation of bulk-shaped rich rare earth phase on the boundary of neodymium-iron-boron main phase is reduced, and the neodymium-iron-boron permanent magnets low in production cost and high in performance are obtained.

Description

A kind of manufacture method of sintered Nd-Fe-B permanent magnet

Technical field

The present invention relates to a kind of manufacture method of sintered Nd-Fe-B permanent magnet, particularly relate to one and can suppress neodymium iron boron pressed compact crystal grain fast growth in sintering process, manufacture the method for low cost, high-performance permanent magnet.

Background technology

Known by those skilled in the art, main in Nd Fe B alloys exist two kinds of phases: one is principal phase, and chemical molecular formula is RE ₂fe ₁₄b, be the crucial phase producing high permanent magnetism performance, its volume fraction accounts for more than 95%; Another kind is Nd-rich phase mutually, is distributed in RE ₂fe ₁₄the border of B main phase grain, plays the magnetostatic coupling between isolated main phase grain and makes magnet have HCJ high as far as possible.Therefore, for obtaining excellent permanent magnetism performance, need the chemical composition of Nd Fe B alloys to do such configuration: the composition of alloy should as far as possible close to RE on the one hand ₂fe ₁₄the stoichiometric composition of B principal phase, namely just divides composition; Also q.s Nd-rich phase must be had on the other hand in alloy.This just means that the total amount of rare earth in the chemical composition of Nd Fe B alloys must be greater than RE ₂fe ₁₄b principal phase just divide composition.In addition, for satisfied difference demagnetization environment is to the demand of permanent magnet applications, needs to carry out Some substitute Nd with heavy rare earth elements such as Dy, Tb, to improve the HCJ of magnet, replace part Fe to improve the anti-demagnetization capability of magnet.So, the chemical molecular formula of the principal phase of Nd Fe B alloys is just often expressed as RE ₂m ₁₄b, wherein, RE represents with Nd to be the rare earth element of main component, and other are as rare earth elements such as Pr, Dy, Tb, Gd, Ho; M represents with Fe to be the transiting group metal elements of main component, and other elements are as Co, Cu, Al, Ga, Nb etc.If be expressed as the form of percentage by weight, then the chemical composition of Nd Fe B alloys is: RE _xm _100-x-yb _y.Wherein, x is exactly the total amount of rare earth of Nd Fe B alloys, for sintered Nd-Fe-B permanent magnetic material, and common total amount of rare earth x=28 ~ 35%wt..If total amount of rare earth is less than 28%wt., very little, the magnet preparing high HCJ is just very difficult for Nd-rich phase; If total amount of rare earth is greater than 35%wt., Nd-rich phase is too many, is just difficult to the sintered Nd-Fe-B permanent magnet of the high remanent magnetism of preparation, high energy product, high corrosion-resistant.

Existing Nd-Fe-B permanent magnet production technology is generally, and after being equipped with by a certain percentage by required various alloying elements, being placed in vacuum medium frequency induction furnace fusing evenly, then pouring into the laminar ingot casting that thickness is 0.1 ~ 0.5mm.The crystallite dimension of laminar neodymium iron boron mother alloy ingot is like this several microns of extremely hundreds of microns.

Then, it is 3.0 ~ 5.0 μm of yardsticks that described neodymium iron boron foundry alloy is crushed to average particle size particle size after hydrogenation, makes all powder particles all become monocrystal.Like this, the average particle size particle size of powder and crystallite dimension are all 3.0 ~ 5.0 μm.

Subsequently, above-mentioned powder is placed on the green briquette being pressed into definite shape in the outer die cavity executing magnetic field.In this operation, under the effect of all powder particle outside magnetic field, its easy magnetizing axis arranges along magnetic direction, applies enough large press power immediately and this aligning of powder particle is fixed up.Then, by the green briquette that suppresses at 1000 ~ 1100 DEG C of sintering, make it densification, become magnet blank; Blank magnet is also needed to carry out one-level or second annealing process, to optimize magnetic property further at 450 ~ 950 DEG C if desired; Then operation carries out machining, cut, is ground to required shape, size by blank magnet, also need if desired to carry out surfacecti proteon process; Finally, carry out magnetizing along direction of easy axis and namely obtain operable permanent magnet product.

According to neodymium iron boron phasor, the fusing point of principal phase about 1155 DEG C in Nd Fe B alloys, the fusing point of Nd-rich phase about 450 ~ 600 DEG C.The effect of Nd-rich phase not only can make neodymium iron boron tool magnet have high HCJ, and, because the fusing point of Nd-rich phase is far below principal phase, make magnet be easy to densification in the sintering process of 1000 ~ 1100 DEG C.

From Principles of Metallography, in the sintering densification process of 1000 ~ 1100 DEG C, the Nd-rich phase of a large amount of melting is enclosed in around main phase grain, causes main phase grain to grow up rapidly, alligatoring.Sintering temperature is higher, sintering time is longer, and main phase grain is thicker, the size of crystal grain is more uneven, and the performance of magnet will be deteriorated; On the contrary, if sintering temperature is too low, the Nd-rich phase ratio of melting is very few, then the densification degree of magnet is low, not only makes magnetic property worsen, and mechanical strength and decay resistance also very poor.Therefore, for obtaining excellent permanent magnetism performance, the density of sintered magnet just should be made high as far as possible, main phase grain is unlikely to too to grow up simultaneously---and the average-size of crystal grain should below 10 μm, and more carefully better.

For making high density, compact grained Sintered NdFeB magnet, existing technology is broadly divided into two classes: one is neodymium iron boron foundry alloy is crushed to after hydrogenation particle size and crystallite dimension is all about 3.0 μm even less than 3.0 μm, then at about 1020 DEG C of sintering densifications, the average-size of final magnet crystal grain is made to refine to 5 ~ 10 μm.Compared with traditional technology being crushed to 3.0 ~ 5.0 μm of yardsticks, because the specific area of powder increases, the oxidation activity of powder particle sharply increases, manufacturing process needs expensive equipment and complicated technological measure to protect in case oxidation, and manufacturing cost is high, powder easily catches fire, handling safety performance is poor.Another kind of technology is by adding the refractory metals such as Nb, Mo, Ti, ZrO or oxide in Nd Fe B alloys, as as described in US Patent No. 6527874B2, main phase grain border in sintering process is made by infusibility metal compound particles pinning, to hinder growing up of main phase grain.The disadvantage of this technology is, the refractory metal added and compound thereof are all non-magnetic phases, significantly can reduce remanent magnetism and the magnetic energy product of magnet.

In addition, be in the neodymium iron boron magnetic body of 28 ~ 35wt.% at the common rare earth total content made by prior art, the many crystallite dimensions of ubiquity are greater than the Nd-rich phase of the large bulk of 1.0 μm.These large bulks, nonmagnetic Nd-rich phase only plays a part to fill magnet interior void, does not contribute the magnetic property of magnet, and the Nd-rich phase only having those to be wrapped in main phase grain border evenly, continuously just has contribution to the coercive force of magnet.On the contrary, because Nd-rich phase is the phase be very easily corroded in Nd Fe B alloys, the existence of the Nd-rich phase of these large bulks reduces the decay resistance of magnet; Secondly, the Nd-rich phase of nonmagnetic, large bulk plays a part to dilute whole magnet magnetic moment, and its existence in magnet actually reduces the magnetic property of the unit volume of permanent magnet; In addition, because rare earth is the constituent element that in Nd Fe B alloys, cost is the highest, in fact these also add the manufacturing cost of Nd-Fe-B permanent magnet to the Nd-rich phase of magnet performance large bulk pernicious.Therefore, reduce these the large bulks in Nd-Fe-B permanent magnet, nonmagnetic Nd-rich phase not only can significantly improve magnetic property and the corrosion resistance characteristic of magnet, effectively can also reduce the cost of raw material simultaneously.But existing Nd-Fe-B permanent magnet manufacturing technology all cannot overcome this difficulty that there is large block Nd-rich phase in magnet.

Such as, CN1468319A proposes the pattern or the distribution that improve large block Nd-rich phase by the method that the Nd Fe B alloys powder of multiple heterogeneity carries out mixing, because the average particle size particle size of the Nd Fe B alloys powder of its multiple heterogeneity used is identical with average grain size, all powder particle is all monocrystal, and there is single direction of easy axis, be very easy between particle mutually annex and grow up in sintering process; Further, this difficulty that there is large block Nd-rich phase also fundamentally cannot be solved in magnet by described method.

Summary of the invention

The object of the invention is by being that 28 ~ 35wt.%, average particle size particle size and crystallite dimension are all in sintered NdFeB mother (master) alloy powder of 3.0 ~ 5.0 μm and add a kind of rare earth total content significantly lower than master alloy powder at common rare earth total content, its crystallite dimension is also much smaller than the method for the chilling Nd Fe B alloys adjuvant powders of its particle size simultaneously, suppress neodymium iron boron pressed compact that the fast growth of crystal grain occurs in sintering process, reduce the generation of large block Nd-rich phase on neodymium iron boron principal phase border, obtain low cost of manufacture, high performance Nd-Fe-B permanent magnet.

The present invention is achieved in that a kind of manufacture method of sintered Nd-Fe-B permanent magnet, and the method is the two alloy approach using foundry alloy and assistant alloy, it is characterized in that: the crystallite dimension of described assistant alloy is 0.01 ~ 0.1 μm.

Preferably, described foundry alloy and assistant alloy are RE-M-B alloy, containing RE ₂m ₁₄b phase, wherein RE is rare earth element, and M is transiting group metal elements.

Preferably, described assistant alloy rare earth elements total content is 16wt.% ~ 28wt.%.

Preferably, the rare earth element in described assistant alloy is not containing heavy rare earth element.

Preferably, described foundry alloy rare earth elements total content is 28 ~ 35wt.%

Preferably, described assistant alloy accounts for the ratio of total alloy is 0.1wt.% ~ 5wt.% percentage by weight.

Preferably, described foundry alloy and assistant alloy are ground into the powder of average particle size particle size 3.0 ~ 5.0 μm.

Preferably, described foundry alloy and assistant alloy can after airflow milling is pulverized mixed powder, or powder mixed after again airflow milling pulverize.

Preferably, described assistant alloy adopts the melting of rapid hardening thin slice technique.

Preferably, the crystallite dimension of described foundry alloy is 3.0 ~ 5.0 μm.

At rare earth total content between 16wt.% ~ 28wt.%, average grain size is 0.1 ~ 0.01 μm, average particle size particle size is in the chilling neodymium iron boron assistant alloy powder of 3.0 ~ 5.0 μm, each powder particle being of a size of 3.0 ~ 5.0 μm is of a size of the tiny crystal grains of the disorientation of 0.1 ~ 0.01 μm containing many.The powder particle of this tiny crystal grains containing disorientation, the master alloy powder Particle Phase ratio with single direction of easy axis of 3.0 ~ 5.0 μm is all with average particle size particle size and crystallite dimension, in the sintering densification process of 1000 ~ 1100 DEG C, be not easy fast growth.Therefore, by being that 28 ~ 35wt.%, average particle size particle size and crystallite dimension are all in the main powder of sintered NdFeB of 3.0 ~ 5.0 μm and add the chilling neodymium iron boron assistant alloy powder that another a small amount of rare earth total content is 16 ~ 28wt.%, average grain size is 0.1 ~ 0.01 μm, average particle size particle size is 3.0 ~ 5.0 μm at common rare earth total content, just can suppress neodymium iron boron pressed compact that the fast growth of crystal grain occurs in sintering process; And, due to the Nd Fe B alloys of added a small amount of described chilling assistant alloy powder inherently low total amount of rare earth, the Nd-rich phase of large bulk pernicious can be absorbed in sintering process, so, not only do not damage the remanent magnetism of final neodymium iron boron magnetic body, significantly improve maximum magnetic energy product and the demagnetization curve rectangularity of magnet on the contrary, thus manufacture low cost, high performance sintered Nd-Fe-B permanent magnet.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the sintered Nd-Fe-B alloy powder particle usually manufactured;

Fig. 2 is the microstructure schematic diagram after Nd-Fe-B permanent magnet internal grain that the sintering process usually manufactured causes is grown up;

The schematic diagram of the chilling neodymium iron boron assistant alloy powder particle that Fig. 3 adds for the present invention;

Fig. 4 is after the chilling neodymium iron boron assistant alloy powder particle that with the addition of of the present invention, the Nd-Fe-B permanent magnet internal grain that sintering process causes grow up after microstructure schematic diagram;

Fig. 5 is the performance of the Nd-Fe-B permanent magnet sintered into add the assistant alloy powder of different content in the powder of foundry alloy D after.

Embodiment

Illustrate below with reference to accompanying drawings according to the specific embodiment of the present invention.

First, make with common method of smelting neodymium iron boron master (mother) alloy that rare earth total content is 28 ~ 35wt.%, then foundry alloy is ground into by airflow milling the master alloy powder that average particle size particle size and crystallite dimension are all 3.0 ~ 5.0 μm after over hydrogenation;

Use rapid hardening thin slice technique again, or chilling method of smelting prepares the chilling neodymium iron boron assistant alloy that rare earth total content is 16wt.% ~ 28wt.%, then this assistant alloy is ground into by airflow milling the assistant alloy powder that average grain size is 0.1 ~ 0.01 μm, average particle size particle size is 3.0 ~ 5.0 μm after over hydrogenation;

After the above-mentioned master alloy powder of certain weight ratio and assistant alloy powder fully being mixed in meal mixer, under magnetic field, orientation is compressing, and the pressed compact be pressed into obtains magnet through second annealing process again after high temperature sintering.

At 20 DEG C, measure the magnetic property of magnet with Hysteresisgraph, comprise remanent magnetism, coercive force, magnetic energy product and flex point coercive force.Measure the density of magnet simultaneously.

For making full use of the magnetocrystalline anisotropy of Nd Fe B alloys, wishing that the easy magnetizing axis of all powder particles arranges in the same direction, making the permanent magnetism performance of magnet the strongest.For reaching this purpose, just needing the smelting technology controlling neodymium iron boron foundry alloy, making the crystallite dimension of prepared neodymium iron boron foundry alloy be greater than the target average-size 3.0 ~ 5.0 μm of powder particle.Like this, each powder particle just can be made to be monocrystal through pulverizing process subsequently, that is, the particle size of powder is identical with crystallite dimension.

And in order to obtain higher coercive force, remanent magnetism, high energy product simultaneously, obtaining the sintered Nd-Fe-B permanent magnet of high corrosion-resistant, the rare earth total content of foundry alloy preferably controls at 28 ~ 35wt.%.

In the melting operation of assistant alloy, by the Nd Fe B alloys of melting cooled and solidified rapidly, just can obtain the Nd Fe B alloys ingot casting that crystal grain is extremely fine, then be used the pulverizing of airflow milling equipment can obtain the chilling Nd Fe B alloys powder that average grain size is 0.1 ~ 0.01 μm, average particle size particle size is 3.0 ~ 5.0 μm.When the total amount of rare earth of assistant alloy is greater than 25wt.%, the quick cooling alloy obtained is formed primarily of neodymium iron boron principal phase and Nd-rich phase, and along with the increase of total amount of rare earth, Nd-rich phase is more and thicker, distributes also more uneven; When the total amount of rare earth of assistant alloy is less than 25wt.%, the quick cooling alloy obtained is mainly by neodymium iron boron principal phase and α-Fe phase composition, and along with the minimizing of total amount of rare earth, α-Fe is also more mutually and thicker, distributes also more uneven.The present invention that Here it is selects the total amount of rare earth of described chilling neodymium iron boron assistant alloy being preferably not less than 16wt.% and being not more than the reason of 28wt.%.

The pulverizing process of Nd Fe B alloys uses airflow milling equipment usually, the powder made thus is made up of the particle of a large amount of different size, that is the particle size of Nd Fe B alloys powder is within the specific limits in a distribution, this area adopts the average particle size particle size of powder to represent the particle size of Nd Fe B alloys powder usually, or claims granularity.In like manner, the crystallite dimension of powder is also that this area adopts the average grain size of powder to represent the crystallite dimension of Nd Fe B alloys powder usually within the specific limits in a distribution, or claims grain size.

It is below specific embodiment.

Table 1 is the weight percent composition formula of master alloying used and assistant alloy in each embodiment and comparative example.Wherein alloy A is neodymium iron boron master (mother) alloy of 32wt.% with the rare earth total content that common method of smelting makes; Alloy B is the making of the present invention's chilling method of smelting, crystallite dimension is 0.1 ~ 0.01 μm and the remarkable assistant alloy lower than alloy A of rare earth total content (26.8wt.%); Alloy C is the making of the present invention's chilling method of smelting, crystallite dimension is 0.1 ~ 0.01 μm and rare earth total content (23.2wt.%) is remarkable in RE ₂fe ₁₄b just divide composition and containing the assistant alloy of part α-Fe phase.

Table 1

	Nd	Pr	Dy	B	Co	Cu	Al	Ga	TRE	Fe
											Alloy A	23.0	6.0	3.0	1.0	1.0	0.1	0.3	0.15	32.0	Surplus
Alloy B	21.5	5.3	0	0.95	0	0.1	0.2	0	26.8	Surplus
											Alloy C	18.2	5.0	0	0.95	0	0.1	0.2	0	23.2	Surplus

embodiment 1

First prepare burden by the alloy A of table 1 middle rare earth total content TRE=32.0wt.%, then foundry alloy is made into common method of smelting, then pulverized by airflow milling after over hydrogenation by foundry alloy and form master alloy powder, the crystallite dimension of powder is 3.0 ~ 5.0 μm; Prepare burden by the alloy B of table 1 middle rare earth total content TRE=26.8wt.%, assistant alloy thin slice is made into chilling method of smelting, obtain assistant alloy powder by pulverizing by airflow milling after direct for assistant alloy thin slice coarse crushing, the crystallite dimension of this assistant alloy powder is 0.1 ~ 0.01 μm again.The powder average particle size of alloy A and alloy B is 3.6 μm.

Be after the powder of alloy A of 98wt.% fully mixes in meal mixer with the powder of the alloy B of 2wt.% by weight fraction, orientation under 1.95T magnetic field, 0.8t/cm ²pressure makes type, sinters through 1050 DEG C the magnet being of a size of 51*51*25mm into, then at 900 DEG C and 480 DEG C of second annealings.Measure magnetic property data to the magnet made, result is as shown in table 2.

comparative example 1

By the powder of alloy A single in embodiment 1 orientation under 1.95T magnetic field, 0.8t/cm ²pressure makes type, sinters through 1050 DEG C the magnet being of a size of 51*51*25mm into, subsequently at 900 DEG C and 480 DEG C of second annealings.Measure magnetic property data to the magnet made, result is as shown in table 2.

Can see from the data of table 2, embodiment 1 add in the main powder of common Nd Fe B alloys account for total amount 2wt.% not containing heavy rare earth and total amount of rare earth lower there is the assistant alloy B powder of fine-grain after, made magnet is when remanent magnetism Br is substantially constant, and coercivity H j, maximum magnetic energy product (BH) m and demagnetization curve rectangularity Hk/Hcj are significantly improved.This is that its internal crystal framework does not have defect, as shown in Figure 1, wherein represents the direction of easy axis of intra-die with thick arrow because common Nd Fe B alloys powder particle is all monocrystal, and 1 represents principal phase, and 2 represent Nd-rich phase.In the process of high temperature sintering, be easy between the powder particle closed on to occur mutually annex and grow up, alligatoring.Growing up to rise and fall by local energy due to the mutual annexation between this crystal grain affects, and just causes the uneven of crystallite dimension in final sintered magnet, as shown in Figure 2.

Theory and practice proves, the crystal grain of neodymium iron boron magnetic body is more tiny, size is more even, and the squareness of its coercivity H j, maximum magnetic energy product (BH) m and demagnetization curve is higher.The powder of the alloy B of adding due to the present invention to be average grain size the be brilliant particle of fine chilling of 0.1 ~ 0.01 μm, as shown in Figure 3, several easy axis small grains at random is contained in each powder particle inside, in the process of high temperature sintering, due to the brilliant granule interior of chilling fine-grain between lattice inconsistent, it is mutually annexed and grows up and become the very large energy of lattice on all four monocrystal needs; In addition, because principal phase RE ₂fe ₁₄the fusing point of B about 1155 DEG C, and the fusing point of Nd-rich phase only has an appointment 450 ~ 600 DEG C, in the sintering process of 1050 DEG C, the brilliant granule interior of the fine chilling in low, that thus Nd-rich phase ratio the is little alloy B adjuvant powders of total amount of rare earth is also not easy to be formed micro-molten bath and fast growth.So, what the present invention added has the neodymium iron boron pressed compact manufactured by alloy B adjuvant powders of fine chilling crystalline substance in the process of identical high temperature sintering, has the effect suppressing other regular grain growth, as shown in Figure 4.In addition, the alloy B adjuvant powders with fine chilling crystalline substance added due to the present invention inherently has RE ₂fe ₁₄the alloy of B crystal structure, and addition is lower than 5wt.%, has an impact hardly to the remanent magnetism of final magnet.

Normally, be all the powder of 0.1 ~ 1 μm of scope in conventional master alloy powder containing a certain proportion of crystallite dimension and particle size, if the crystallite dimension of auxiliary powder is greater than 0.1 μm, then it does not have the effect suppressing other regular grain growth; If the crystallite dimension of auxiliary powder is less than ~ 0.01 μm, namely nanoscale, then manufacturing process complex, cost are high, are difficult to realize in practice.

Compared with comparative example 1, embodiments of the invention 1 are when remanent magnetism Br is substantially constant, coercivity H j, maximum magnetic energy product (BH) m and demagnetization curve rectangularity are all significantly improved, and rare earth weight ratio total in magnet, particularly the ratio of heavy rare earth Dy decreases, and the manufacturing cost of magnet just reduces simultaneously.

If the alloy B adjuvant powders ratio with fine chilling crystalline substance of adding is greater than 5wt.%, because the easy magnetizing axis with the particle of fine chilling crystalline substance after sintering can depart from the easy magnetizing axis of other main phase grain usually, the remanent magnetism of final magnet significantly will be reduced.On the contrary, if the alloy B adjuvant powders ratio with fine chilling crystalline substance of adding is less than 0.1wt.%, then it suppresses the effect of other regular grain growth just not remarkable.Therefore, the present invention preferably adds the assistant alloy powder ratio with fine chilling crystalline substance of described low total amount of rare earth is 0.1wt.% ~ 5wt.%.

embodiment 2

Preparation process, the crystallite dimension of the master alloy powder (alloy A powder) and assistant alloy powder (alloy B powder) that use in embodiment 2 are identical with particle mean size and embodiment 1.Be after the alloy A powder of 98wt.% fully mixes in meal mixer with the alloy B adjuvant powders of 2wt.% by weight fraction, orientation under 1.95T magnetic field, 0.8t/cm ²pressure makes type, sinters through 1070 DEG C the magnet being of a size of 51*51*25mm into, then at 900 DEG C and 480 DEG C of second annealings.Measure magnetic property data to the magnet made, result is as shown in table 2.

comparative example 2

By the powder of alloy A single in embodiment 2 orientation under 1.95T magnetic field, 0.8t/cm ²pressure makes type, sinters through 1070 DEG C the magnet being of a size of 51*51*25mm into, subsequently at 900 DEG C and 480 DEG C of second annealings.Measure magnetic property data to the magnet made, result is as shown in table 2.

Known by the professional of the industry, neodymium iron boron pressed compact is in high-temperature sintering process, and growing up of crystal grain is very responsive to sintering temperature.If sintering temperature is slightly higher, crystal grain will sharply be grown up, and coercivity H j, maximum magnetic energy product (BH) m of final magnet and demagnetization curve rectangularity will worsen.Therefore, in the manufacture process of Sintered NdFeB magnet, there is very high temperature control precision requirement to agglomerating plant.

Can be clear that from the data of table 2, after sintering temperature brings up to 1070 DEG C from 1050 DEG C, compared with comparative example 1, because crystal grain is sharply grown up, coercivity H j, maximum magnetic energy product (BH) m of the final magnet of comparative example 2 and demagnetization curve rectangularity all significantly reduce.On the contrary, the alloy B adjuvant powders with fine chilling crystalline substance added in embodiments of the invention 2 has and suppresses the effect of other regular grain growth, reaches at 20 DEG C 1070 DEG C and still has good coercivity H j, maximum magnetic energy product (BH) m and demagnetization curve rectangularity after same time sintering exceeding nominal sintering temperature.After this illustrates and adopts method of the present invention, require to reduce to the temperature control precision of agglomerating plant, equipment cost and the process management cost of sintering circuit can reduce.

embodiment 3

By weight fraction be the composition of 98wt.% identical with alloy A in table 1, the meal that obtains after break process in hydrogenation after the method for smelting of routine makes foundry alloy, identical with alloy B in table 1 with the composition of 2wt.%, after over-quenching method of smelting is made into and fully mixes in meal mixer without hydrotreated meal after assistant alloy thin slice, described mixture is pulverized through airflow milling again, makes the powder that particle mean size is 3.4 μm in the lump.Orientation under 1.95T magnetic field subsequently, 0.8t/cm ²compressing, sinter through 1050 DEG C the magnet being of a size of 51*51*25mm into, then after 900 DEG C and 480 DEG C of second annealings, with automatically surveying, magnetic device measurement magnetic property data are as shown in table 2.

Can see, compared with comparative example 1, coercivity H j, maximum magnetic energy product (BH) m of the final magnet of embodiments of the invention 3 and demagnetization curve rectangularity are obtained for and increase substantially.

embodiment 4

Be after the alloy A of 98% fully mixes in meal mixer with the assistant alloy C made with quenching method of 2% by weight fraction as shown in table 1, in the lump through hydrogenation treatment, again described mixture is pulverized through airflow milling again, make the powder that particle mean size is 3.4 μm in the lump.Described assistant alloy C be that the method for smelting of the present invention's chilling makes, crystallite dimension is that the rare earth total content of 0.1 ~ 0.01 μm is significantly lower than RE ₂fe ₁₄b just divide composition and containing the alloy of part α-Fe phase.Then orientation under 1.95T magnetic field, 0.8t/cm ²compressing, sinter through 1050 DEG C the magnet being of a size of 51*51*25mm into, subsequently after 900 DEG C and 480 DEG C of second annealings, with automatically surveying, magnetic device measurement magnetic property data are as shown in table 2.

Can see, compared with comparative example 1, the remanent magnetism of the final magnet of embodiments of the invention 4, coercivity H j, maximum magnetic energy product (BH) m and demagnetization curve rectangularity Hk/Hcj are obtained for and increase substantially.

Here pay particular attention to, the total amount of rare earth in described assistant alloy C is 23.2%wt., lower than RE ₂fe ₁₄b just divides composition, also there is part α-Fe in alloy C now except principal phase.Due to alloy C make with quenching method, its crystallite dimension is 0.1 ~ 0.01 μm, very fine, in 1050 DEG C of sintering processes, there is ppolymorphism and be transformed into γ-Fe phase in the α-Fe in fine-grain state, and by with the liquid Nd-rich phase generation peritectic reaction in master alloying, formed RE ₂fe ₁₄b phase.That is, by adding total amount of rare earth lower than RE ₂fe ₁₄the Quench alloy C just dividing composition of B, can be absorb common rare earth total content the Nd-rich phase of magnet performance large bulk pernicious in the Nd Fe B alloys of 28 ~ 35wt.%, and make it to be transformed into normal RE ₂fe ₁₄b principal phase.So, the principal phase ratio be equivalent in total component of magnet significantly improves, therefore the remanent magnetism of magnet also significantly improves; And, because the added Quench alloy C particle in fine-grain state inhibits growing up of alloy A particle in sintering process, increase substantially so the coercivity H j of magnet, maximum magnetic energy product (BH) m and demagnetization curve rectangularity are obtained for.

Table 2

embodiment 5

Prepare burden by the alloy D of table 3 middle rare earth total content TRE=32.0wt.%, then foundry alloy is made into common method of smelting, then pulverized by airflow milling after over hydrogenation by foundry alloy and form master alloy powder, the average grain size of powder is 3.5 μm, and average particle size particle size is also 3.5 μm; Prepare burden by the alloy B of table 1 middle rare earth total content TRE=26.8wt.%, assistant alloy thin slice is made into chilling method of smelting, assistant alloy powder is obtained by pulverizing by airflow milling again after direct for assistant alloy thin slice coarse crushing, the crystallite dimension of this assistant alloy powder is 0.1 ~ 0.01 μm, and average particle size particle size is 3.5 μm.

Add respectively in the powder of described foundry alloy D and account for total amount 0wt.%, the powder of the alloy B of 1.0wt.%, 1.5wt.%, 2.5wt.% and 5.0wt.%, and after fully mixing in meal mixer respectively, orientation under 1.95T magnetic field, 0.8t/cm ²pressure makes type, through 1050 DEG C of sintering one hour, sinters the magnet being of a size of 51*51*25mm into, then 900 DEG C and the tempering one hour of 480 DEG C of difference.Measure magnetic property data to the magnet made, result as shown in Figure 5.

Table 3

	Nd	Pr	Dy	B	Co	Cu	Al	Ga	TRE	Fe
											Alloy D	21.5	6.0	1.5	1.0	1.0	0.1	0.3	0.1	32.0	Surplus

In figure 5, abscissa represents the addition (percentage by weight) of alloy B powder, and the ordinate on Fig. 5 left side represents remanent magnetism Br, coercivity H j and maximum magnetic energy product (BH) m of magnet, and the ordinate on the right represents the flex point coercive force Hk of magnet.

Can be clear that from accompanying drawing 5: along with the increase of the addition of alloy B powder, the remanent magnetism Br of magnet almost remains unchanged, coercivity H j, maximum magnetic energy product (BH) m of magnet then progressively increase, especially, the flex point coercive force Hk characterizing magnet demagnetization curvilinear squares degree index enlarges markedly; Such as, but when the addition of alloy B powder is more than 2.5wt.%, when reaching 5.0wt.%, every magnetic property index of magnet no longer increases with the increase of the addition of alloy B powder.Therefore, the weight fraction that the total amount of rare earth that the present invention preferably adds in master alloy powder is less than 28wt.%, crystallite dimension is the assistant alloy powder of 0.1 ~ 0.01 μm is 0.1 ~ 5.0wt.%.

The worker of this area should be clear, in each embodiment explained above, with adding a small amount of low total amount of rare earth, another neodymium iron boron with fine chilling crystalline substance assists powder, suppress growing up of in sintering process other normal crystal grain, thus manufacture low cost, the principle of sintered Nd-Fe-B permanent magnet product of high-quality is identical.

Describe manufacture low cost disclosed according to the present invention, the principle of sintered Nd-Fe-B permanent magnet product of high-quality and method in detail with reference to accompanying drawing above, principle disclosed according to the present invention and method can be manufactured sintered Nd-Fe-B permanent magnet and be applied to various field by those skilled in the art thus, such as be applied in various computer drive, industry and civilian motor, be applied to the driver part etc. of various loud speaker, transducer, electric motor of automobile and various Medical Instruments and industrial automation equipment, instrument.

Describe multiple embodiment of the present invention in detail with reference to accompanying drawing above, but embodiment is above only unrestricted the present invention to of the present invention schematically illustrating.In addition, although be described each embodiment with form that is independent, that separate above, those skilled in the art it is to be appreciated that above-mentioned multiple embodiment also can be applied in combination.And those skilled in the art can make various modifications and variations in conjunction with the technology of the manufacture permanent magnet of existing routine to the present invention upon reading the above description, and this modifications and variations also drop within protection scope of the present invention.

Claims

1. a manufacture method for sintered Nd-Fe-B permanent magnet, the method is the two alloy approach using foundry alloy and assistant alloy, it is characterized in that: the crystallite dimension of described assistant alloy is 0.01 ~ 0.1 μm.

2. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: described foundry alloy and assistant alloy are RE-M-B alloy, containing RE ₂m ₁₄b phase, wherein RE is rare earth element, and M is transiting group metal elements.

3. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 2, is characterized in that: described assistant alloy rare earth elements total content is 16wt.% ~ 28wt.%.

4. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 3, is characterized in that: the rare earth element in described assistant alloy is not containing heavy rare earth element.

5. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 2, is characterized in that: described foundry alloy rare earth elements total content is 28 ~ 35wt.%.

6. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: the ratio that described assistant alloy accounts for total alloy is 0.1wt.% ~ 5wt.% percentage by weight.

7. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: described foundry alloy and assistant alloy are ground into the powder of average particle size particle size 3.0 ~ 5.0 μm.

8. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: described foundry alloy and assistant alloy can after airflow milling is pulverized mixed powder, or powder mixed after again airflow milling pulverize.

9. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: described assistant alloy adopts the melting of rapid hardening thin slice technique.

10. the manufacture method of sintered Nd-Fe-B permanent magnet as claimed in claim 1, is characterized in that: the crystallite dimension of described foundry alloy is 3.0 ~ 5.0 μm.