CN100545967C - Utilize the method for electric field low temperature Fast Sintering neodymium iron boron magnetic body - Google Patents
Utilize the method for electric field low temperature Fast Sintering neodymium iron boron magnetic body Download PDFInfo
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- CN100545967C CN100545967C CNB2005100207949A CN200510020794A CN100545967C CN 100545967 C CN100545967 C CN 100545967C CN B2005100207949 A CNB2005100207949 A CN B2005100207949A CN 200510020794 A CN200510020794 A CN 200510020794A CN 100545967 C CN100545967 C CN 100545967C
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- iron boron
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Abstract
The method of utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body disclosed by the invention, be to contain Nd 12.4～15.5 in atomic percent, Fe 77.7～81.4, the Nd Fe B alloys of B 6.0～6.8, and broken after the vacuum melting, ball milling is the Nd Fe B alloys fine powder of 3～5 μ m, pack in the mould, behind magnetic field orientating, be pressed into base substrate, then base substrate be positioned in the electric heating equipment, 3～10 volts of output voltages, output current 800～5000 peaces, 10
-3Under the vacuum condition of Pa, utilize electric current directly it to be heated rapidly, make the interior constituent element of base substrate under 500～900 ℃, continue the densification process that sintering can be finished base substrate in 5～8 minutes by base substrate.Sintering temperature of the present invention is low, and sintering time is short, not only makes the manufacturing cycle of magnet short, efficient is high, and energy consumption also reduces greatly, and can also obtain superfine grained structure, is highly advantageous to improve the performance of magnet; Also can control magnet by adjusting programming rate, sintering temperature and size of current easily and reach densified sintering product.
Description
One, technical field
The invention belongs to neodymium iron boron magnetic body sintering technology field, be specifically related to a kind of method of utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body.
Two, background technology
At present, neodymium iron boron (NdFeB) the magnet overwhelming majority adopts the prior powder metallurgy method to make.The technical process of this method is: the fine powder that the NdFeB alloy cast ingot after the melting is broken into 3～5 μ m, in magnetic field, be pressed into relative density and be the green compact of 50～70% desired structure shape, in sintering temperature is vacuum sintering furnace about 1050 ℃～1120 ℃, carry out sintering then.Concrete sintering temperature is relevant with the content of Nd in the NdFeB alloy.Nd content is low more, and sintering temperature also can be high more, and this method with base substrate when normal temperature is heated to sintering temperature, its heating-up time needs 2h approximately, sintering time is 1.5-3h.From these characteristics of being not difficult to find out the prior powder metallurgy method be: need not impressed pressure, also do not have chemical reaction in the sintering process and take place, but utilize long high temperature sintering to make the densification of base substrate nature.As everyone knows, magnet is fine and close more behind the sintering, and crystal grain is tiny more, helps the raising of magnet performance more.But owing to the long-time high temperature sintering characteristics of this method, not only can cause the grain growth of magnet, the performance of appreciable impact magnet also can cause the manufacturing cycle of magnet long, power consumption again consuming time.
Little wild elegant clear (powder and powder metallurgy (day), 2000,47 (6): 667-673) studied that to utilize discharge plasma sintering (Sparking Plasma Sintering, i.e. SPS) technology prepared composition be Nd of Japan
9Fe
76Co
8V
1B
6The technology of Sintered NdFeB magnet.The sintering pressure of this technology is 490Mpa, and programming rate is 20 ℃/min.People such as Yue Ming (the novel NdFeB permanent magnetic material of discharge plasma sintering technical study, functional material and device journal, 2003,9 (3): when 295-299) research prepares the Sintered NdFeB magnet with the SPS technology, its sintering process is: sintering temperature 740-860 ℃, the 30-50MPa that exerts pressure, sintered heat insulating time 0-20min.Its result of study shows, is 780 ℃ in sintering temperature, and pressure is 50Mpa, when temperature retention time is 10min, can obtain fine and close Sintered NdFeB magnet.And be lower than 780 ℃ in sintering temperature, and pressure is less, and temperature retention time all can not obtain fine and close Sintered NdFeB magnet during less than 10min.Because the SPS technology is to utilize pulse energy, discharge pulse pressure and a joule thermogenetic TRANSIENT HIGH TEMPERATURE field to realize sintering process, thereby it is compared with the traditional handicraft of preparation Sintered NdFeB magnet, though shortened heating-up time and sintering time greatly, and reduced sintering temperature, but because the SPS technology is when sintering, heating-up time is subjected to the restriction of the plasma that produces between magnetic, can't shorten significantly again; Simultaneously, when continuing to reduce sintering temperature and shortening sintering time, fine and close Sintered NdFeB magnet will can not be obtained; And, adopt SPS technology sintering, require the density of its green compact lower, be generally below 50%, otherwise too closely knit green compact are unfavorable for producing plasma under the effect of electric current, also just can't produce high temperature.In addition, because the SPS sintering is system's pressure sintering mode, thereby in sintering process, need system to provide powerful external pressure to make the sintered body densification on the one hand, could improve the magnetic property of Sintered NdFeB magnet like this, on the other hand, system reduces the performance of magnet to the inevitable again serious degree of orientation that reduces magnet of the immense pressure that magnet applied greatly.So when adopting SPS technology sintering, exist the contradiction that the magnetic property of the density that improves magnet and magnet reduces all the time, thereby also cause the Sintered NdFeB magnet for preparing with the SPS method at present, the problem that its magnetic property is all lower.
Three, summary of the invention
The objective of the invention is problem, a kind of method of utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body is provided at the prior art existence.
The method of utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body provided by the invention, be based on the pressed compact component outside under the effect of electric field, electronics can be done the directed movement of rule on the one hand with respect to lattice atoms, thereby in material, form electric current, can with lattice atoms collision mutually take place on the other hand again in its process of flowing, and impressed current is big more, electronic motion speed is fast more, thereby the interatomic diffusion of constituent element is accelerated, being easy to realize that the mechanism of the densification between constituent element proposes, specifically is to contain Nd 12.4～15.5 in atomic percent, and Fe 77.7～81.4, the Nd Fe B alloys of B 6.0～6.8, broken after the vacuum melting, ball milling is the Nd Fe B alloys fine powder of 3～5 μ m, in the mould of packing into, is pressed into the base substrate of desired structure shape behind magnetic field orientating, carry out sintering then, it is characterized in that sintering is that base substrate is positioned in the electric heating equipment, 3～10 volts of output voltages, output current 800～5000 peaces, be preferably 800～2500 peaces, 10
-3Under the vacuum condition of Pa, utilize electric current directly base substrate to be heated rapidly, make the interior constituent element of base substrate under 500～900 ℃, continue the densification process that sintering can be finished base substrate in 5～8 minutes.
In order to realize goal of the invention better, the present invention also can adopt the technical measures of control programming rate, and promptly the speed control that direct energising heats up to base substrate is 5～1500 ℃/S, is preferably 5～150 ℃/S.
Compared with the prior art the present invention has the following advantages:
1, because the present invention is directly to the pressed compact heating of switching on, thereby can quicken solid-state diffusion between powder in the pressed compact, and then realized under cryogenic conditions, also can making the pressed compact sintering and reaching densification, obtain the purpose of sintered magnet, for cryogenic conditions realizes that solid-state diffusion provides a kind of new method down.
2, adopt the inventive method Sintered NdFeB magnet, its sintering temperature not only is significantly less than the sintering temperature of prior powder metallurgy method, and sintering time also shortens greatly, thus make the manufacturing cycle of magnet short, efficient is high, energy consumption also reduces greatly, meets the requirement of " green production ".
3, because low with the sintering temperature of the inventive method Sintered NdFeB magnet, sintering time is short, thereby the grain growth of sintered body can be effectively controlled, can obtain the superfine grained structure (grain structure of conventional method sintered magnet is 10～20 μ m) about 4～6 μ m, be highly advantageous to and improve the performance of magnet.
4, adopt method sintered NdFeB provided by the invention, its sintering temperature can not be subjected to about the content of Nd in the alloy as conventional method, even material composition changes in a relative broad range, when adopting same sintering temperature, still can make base substrate obtain good densification; Its initial density that requires pressed compact also can be harsh as the SPS technology, because the inventive method can effectively be adjusted by regulating programming rate, sintering temperature and size of current, controls magnet and reach sintering densification.
5, because with method sintered NdFeB provided by the invention, do not need system that external sintering pressure is provided, just can make the blank sintering densification, thereby can avoid on the one hand the contradiction of raising magnet density that the SPS technology occurs and the magnetic property reduction of magnet when sintering, simplify equipment on the other hand again, reduced cost.
6, the inventive method is simple, and is reliable, is easy to regulate control.
Four, description of drawings
View when Fig. 1 heats in the thermal simulation machine heating system that is adopted for pressed compact of the present invention;
Fig. 2 is magnet observed microscopic appearance figure in ESEM of the embodiment of the invention 13 sintering;
Fig. 3 is magnet observed microscopic appearance figure in ESEM of the embodiment of the invention 3 sintering;
Fig. 4 is for being Nd with the prior powder metallurgy method with composition
15Fe
78.3B
6.7Alloy at 90 minutes magnet of 1100 ℃ of following sintering observed microscopic appearance figure in ESEM.
Five, execution mode
Below by embodiment the present invention is carried out concrete description; be necessary to be pointed out that at this following examples only are used for that the invention will be further described; can not be interpreted as limiting the scope of the invention; some nonessential improvement and adjustment that this art skilled person makes according to the invention described above content still belong to protection scope of the present invention.In addition, what deserves to be explained is that following examples all are to carry out on the Gleeble-1500D thermal simulation machine of U.S. DSI science and technology association development.This equipment is made up of vacuum system, computer control system, heating system.Wherein pressed compact is held the energising heated state as shown in Figure 1 in heating system.The concrete process conditions of each embodiment are input computer systems, are programmed by it and control execution.
Embodiment 1～19
1, composition is counted Nd with atomic percent
15Fe
78.3B
6.7, Nd
13.8Fe
80B
6.2And Nd
12.4Fe
81.6B
6.0The NdFeB alloy under the Ar gas shiled respectively at vacuum melting furnace in, process conditions melting routinely, be the Nd Fe B alloys fine powder of 3～5 μ m with the ingot casting of melting through scream an obscenity fragmentation, ball milling of hydrogen then, pack in the mould, being pressed into diameter by listed relative density in the table behind magnetic field orientating is 13mm, highly is the cylindrical green compact of 6mm (being convenient to comparison);
2, after the pressed compact for preparing by handle shown in Figure 1 fixes with chuck, 10
-3Under the vacuum condition of Pa, the electric current according to the corresponding heat temperature raising speed of determined each embodiment in the table is come regulation and control system utilizes electric current by pressed compact it to be heated rapidly.When reaching a certain lower temperature, pressed compact begins sintering and densification gradually.
3, when the pressed compact temperature reaches in the table the determined maximum temperature of each embodiment, be incubated 5 minutes, outage then, and take off pressed compact from chuck, promptly obtain the NdFeB magnet of sintering.
For the microscopic appearance difference of the magnet of the inventive method and prior powder metallurgy method sintering relatively, the magnet of the embodiment of the invention 13,3 sintering gained magnets and prior powder metallurgy method sintering has been carried out scanography with ESEM to its end face, and its photo is seen Fig. 2,3,4 respectively.As can be seen from the figure, very high with the densification degree of the inventive method sintering gained magnet, and crystal grain is all very tiny, embodiment 13 gained magnets especially, then densification degree is lower with the magnet of prior powder metallurgy method sintering, and crystal grain is also very thick.This explanation the present invention can obtain superfine grained structure and have high performance neodymium iron boron magnetic body
Claims (4)
1, a kind of method of utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body, this method is to contain Nd 12.4～15.5 in atomic percent, Fe 77.7～81.4, the Nd Fe B alloys of B 6.0～6.8, broken after the vacuum melting, ball milling is the Nd Fe B alloys fine powder of 3～5 μ m, pack in the mould, behind magnetic field orientating, be pressed into the base substrate of desired structure shape, carry out sintering then, it is characterized in that sintering is that base substrate is positioned in the electric heating equipment, 3～10 volts of output voltages, output current 800～5000 peaces, 10
-3Under the vacuum condition of Pa, utilize electric current directly base substrate to be heated rapidly, make the interior constituent element of base substrate under 500～900 ℃, continue the densification process that sintering can be finished base substrate in 5～8 minutes.
2, the method for utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body according to claim 1 is characterized in that output current is 800～2500 peaces.
3, the method for utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body according to claim 1 and 2 is characterized in that the speed control that direct energising heats up to base substrate is 5～1500 ℃/S.
4, the method for utilizing electric field low temperature Fast Sintering neodymium iron boron magnetic body according to claim 1 and 2 is characterized in that the speed control that direct energising heats up to base substrate is 5～150 ℃/S.
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| CNB2005100207949A CN100545967C (en) | 2005-04-27 | 2005-04-27 | Utilize the method for electric field low temperature Fast Sintering neodymium iron boron magnetic body |
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| CN100545967C true CN100545967C (en) | 2009-09-30 |
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| CN102976730A (en) * | 2012-11-09 | 2013-03-20 | 四川大学 | Method for preparing MnZn ferrite magnetic core by multi-physical field coupling |
| CN108546801B (en) * | 2018-04-27 | 2019-07-12 | 北京科技大学 | A method of extending hot-forging die service life using magnetic, electric field compound action |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6074492A (en) * | 1997-12-30 | 2000-06-13 | Magnequench International, Inc. | Bonded Nd-Fe-B magnets without volumetric expansion defects |
| CN1358595A (en) * | 2001-11-16 | 2002-07-17 | 清华大学 | Method for making rareearth permanent magnet material by discharge plasma sintering |
| CN1412328A (en) * | 2001-10-18 | 2003-04-23 | 山东中舜科技发展有限公司 | Production method of as-cast neodymium-iron-boron |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6074492A (en) * | 1997-12-30 | 2000-06-13 | Magnequench International, Inc. | Bonded Nd-Fe-B magnets without volumetric expansion defects |
| CN1412328A (en) * | 2001-10-18 | 2003-04-23 | 山东中舜科技发展有限公司 | Production method of as-cast neodymium-iron-boron |
| CN1358595A (en) * | 2001-11-16 | 2002-07-17 | 清华大学 | Method for making rareearth permanent magnet material by discharge plasma sintering |
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