CN101276667B - Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet - Google Patents
Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet Download PDFInfo
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Abstract
A hot-bath demagnetization method for a sintered neodymium iron boron permanent magnet is characterized in that, a dried sintered neodymium iron boron permanent magnet with a clean surface is directly immerged in hot-bath with a temperature 5-20 DEG C higher than a Curie temperature Tc of the sintered neodymium iron boron permanent magnet, then cooled after heat insulation in 2-20 minutes. The invention also provides a corresponding device. The invention has advantages that, hot-bath heating is adopted, thus the heating temperature is reduced, heating efficiency is increased, processing time is shortened, production cost is reduced, product quality is ensured, the varying rate of the maximal magnetic energy product (BH)max of the sintered neodymium iron boron permanent magnet is in -2%, and performance depravation is small. The invention is capable of processing high-grade sintered neodymium iron boron permanent magnets such as N50, N52, N55 series, thereby having wide application.
Description
Technical field
The present invention relates to a kind of processing method and device of magnetic material, particularly sintered Nd-Fe-B permanent magnet is removed the processing method and the device of magnetic.
Background technology
Since sintered Nd-Fe-B permanent magnet was invented from nineteen eighty-three, because volume is little, maximum magnetic energy product is high, cost performance good, the motor of electroacoustics field, acquisition of signal field, medical field, scientific research field, domestic energy-conserving electrical equipment, computer, vibrating motor for mobile phone, magneto wind-driven generator, accurate linear electric motors, CD and VCD light read head, all kinds of elevators and high-speed liquid pump etc. have been widely used in.China's sintered Nd-Fe-B permanent magnet output has accounted for more than 70% of Gross World Product at present, and annual production reaches more than 40000 ton, becomes the largest production state of global sintered Nd-Fe-B permanent magnet.
The sintered Nd-Fe-B permanent magnet manufacture process is the preparation of sintering blank, machining, surface treatment, packing magnetizes.In sintering blank preparation process, be magnetic and detect, detect the back permanent magnet and how much have magnetic.Adopt the grinding machine magnetic chuck to fix the workpiece to be machined sintered Nd-Fe-B permanent magnet in the machining, after the completion of processing, sintered Nd-Fe-B permanent magnet is owing to magnetize under the magnetic field of sucker, and the result has the residual magnetism that has about 5mT.In wire cutting technology, also adopt fixedly sintered Nd-Fe-B permanent magnet workpiece of magnetic in addition, can cause being with magnetic equally.The middle product that these have magnetic if do not eliminate before surface treatment to 2mT, because magnetic is adsorbed the thin impurity of irony in the plating bath, cause surface treatment bad in the plating surface treatment process.
The residual magnetism of removing sintered Nd-Fe-B permanent magnet has following method: electromagnetism method and hot demagnetizing method.Practical electromagnetism method is to adopt the power frequency electricity to insert big coil, craft or guipure are continuously by coil internal magnetic field zone, utilize the magnetic hysteresis loop principle to eliminate residual magnetism, but this kind demagnetizing method can not satisfy in the actual needs of the particularly high trade mark N52 of high trade mark N40, the N55 series trade mark.
Heat demagnetization is according to the Curie temperature of the sintered Nd-Fe-B permanent magnet magnetic phase transition characteristics at 313 ℃～350 ℃, eliminates residual magnetism by the method for heating.Method commonly used has box type furnace demagnetization, vacuum furnace demagnetization.
The box type furnace demagnetization, be meant the space that sintered Nd-Fe-B permanent magnet is placed box type furnace, demagnetize by air heat, its treatment temperature is subjected to the influence of the trade mark equally, be the following series of N40,380 ℃～420 ℃ demagnetizations, high trade mark N52, the N55 series trade mark need be in higher temperature as 420 ℃～460 ℃ demagnetizations down, and temperature retention time is generally half an hour.There is following shortcoming in this method: heating-up temperature is too high; Insulation down about 420 ℃, surface oxide layer appears in permanent magnet, can only be used for blank, promptly can only be used for the middle product of the follow-up machining of needs.And high trade mark permanent magnet needs higher heating-up temperature, because the appearance of oxide skin, its performance can worsen more.
External-heat flue vacuum furnace is adopted in vacuum furnace demagnetization, progressively heats and vacuumizes to eliminate harmful steam of former permanent magnet absorption, is incubated 0.5～1 hour between 400 ℃～460 ℃, proposes flue air cooling or air-cooled.Adopt vacuum sintering furnace, because the permanent magnet heat is difficult for distributing in the flue, cooling rate is slow, makes the HCJ reduction or the demagnetization curve square chart of permanent magnet magnetic performance bad.Though and be the direct-type heating, because under vacuum, the vacuum coefficient of heat conduction is little, main by radiation heating, therefore still need heating time long, thermal gradient is big, whole demagnetization process needs 6～8 hours, taken the equipment that the magnet blank is produced significantly, and energy consumption is big, causes the wasting of resources.
Summary of the invention
Technical problem to be solved by this invention is to overcome the above-mentioned defective of prior art and a kind of stew demagnetizing sintered Nd iron boron permanent magnet method is provided, and makes that its treatment temperature is low, demagnetization speed fast, the performance of the sintered Nd-Fe-B permanent magnet after the demagnetization is constant.
The present invention also provides a kind of demagnetizer of sintered Nd-Fe-B permanent magnet, makes it handle sintered Nd-Fe-B permanent magnet automatically apace according to method of the present invention, and the sintered Nd-Fe-B permanent magnet quality after the processing is good.
The present invention solves the problems of the technologies described above the technical scheme that is adopted:
A kind of stew demagnetizing sintered Nd iron boron permanent magnet method; it is characterized in that: the sintered Nd-Fe-B permanent magnet of surface clean, oven dry directly immerses in temperature is the heating bath of Curie temperature Tc+5～20 ℃; temperature retention time 2～20min, cooling fast under protective atmosphere, air cooling or air-cooled again.
Above-mentioned heating bath can be oil bath, bismuth liquid furnace, salt bath etc. according to the transmitting medium difference, and oil bath is owing to still flowing at normal temperatures, and is more convenient when therefore using.
For preventing the heat-conduction medium oxidation in the heating bath, can fill protective gas, when being oil bath or bismuth bath as heating bath.
For guaranteeing product quality better, adopt cooling system heat of cooling medium, make its sintered Nd-Fe-B permanent magnet after cooling processing faster, shorten permanent magnet and thermal medium in the time of contact that the warm period is arranged more than 150 ℃, exempting from slow the cooling influences magnet and makes H
CJVariation.
Have and comprise time of contact of warm period temperature rise period, holding stage and temperature-fall period.Adopt medium to immerse during demagnetization to the temperature back, after insulation finishes, adopt 2 above coolers in the heat source system, progressively increase the cooler number in the different periods, the control cooling rate, temperature is pressed approximately linear and is descended, and perhaps adopts the chilled water medium of refrigerator to come the cooler of cycling hot origin system to carry out the Rapid Thermal exchange, 15 ℃/min of average cooldown rate control.The heat pump forced circulation is the combined thermal transmission mode of convection current and conduction heat transfer between magnet and the conduction oil, and it is fast that magnet obtains heat, and temperature retention time is extremely short.By above method, be controlled in the 30min time of contact.
Above-mentioned sintered Nd-Fe-B permanent magnet can be the sintered Nd-Fe-B permanent magnet that metals such as plating Ni, Zn, NiCuNi have magnetized, do not plate Ni, do not plate Zn, do not plate the sintered Nd-Fe-B permanent magnet of metal tape magnetic such as NiCuNi, or need follow-up machining to remove the sintered Nd-Fe-B permanent magnet of superficial layer after the magnetic test.
The type of cooling after the above-mentioned sintered Nd-Fe-B permanent magnet heating can be decided according to subsequent scenario, and adopting machining to remove surface condition as needs can air cooling or air-cooled.
The present invention analyses scientifically according to Fourier heat conduction formula.Fourier formula heat conduction formula is " Q=-λ * A * dT/dL ".Wherein Q represents heat, the heat that just heat conduction produced or conducted; λ is the thermal conductivity of medium, the area (or contact area of two articles) that the A representative is conducted heat, the temperature difference that dT represents two ends; DL then is the distance at two ends.The big or small same thermal conductivity of heat transferred, heat transfer area are directly proportional, and same distance is inversely proportional to.Thermal conductivity is high more, transmission area is big more, and the distance of transmission is short more, and so heat conducting energy is just high more, also with regard to the easy more heat of taking away.The thermal conductivity of medium has play a part crucial to heated workpiece actual temperature, when the thermal conductivity of conduction oil is 0.10W/m ℃ 250 ℃, salt thermal conductivity when fusion is more than 0.10W/m ℃, and the thermal conductivity of air is 0.025W/m ℃, the thermal conductivity of bismuth is higher, be 7.87W/m ℃, this shows and adopt oil bath or bismuth bath or salt bath can conduct heat soon, make and be heated workpiece and obtain heating up, satisfy " Q=C * m * Δ T ", C is the specific heat that is heated workpiece, and m is the quality of heated parts, and Δ T is the temperature rise amount.More than explanation aerial heating time of coefficient ratio in oil, salt heating time low 4 times of coefficient, than then lower in the bismuth.
Be the product quality after the assurance demagnetization, reach under the prerequisite of demagnetization effectiveness in assurance, treatment temperature and time are low more good more, therefore in the oil bath heating and temperature control more than Curie temperature Tc in 5～20 ℃ of scopes, temperature retention time is 2～20min, this with air in heating and temperature control in Tc+60～100 ℃, temperature retention time compared and is greatly reduced in 0.5～1 hour, with the vacuum furnace of radiation heating demagnetization temperature is that Tc+80～120 ℃, temperature retention time were compared in 0.5～1 hour, and bigger reduction has then been arranged.
The Curie temperature of sintered Nd-Fe-B permanent magnet is recorded by heat scan DSC method, and its method of testing is standard method.Fig. 1 is a N50 sintered Nd-Fe-B permanent magnet thermal analysis curve.In 271 ℃ of bismuth liquid furnace bismuth fusing points, immerse sintered Nd-Fe-B permanent magnet then, measure two kinds of specification Dimension of permanent magnet sample at demagnetization back permanent magnet residual magnetism Tesla under the different temperatures Temperature, in different time interval T ime, obtain the D-3T curve, Fig. 2 is the N50 sintered Nd-Fe-B permanent magnet D-3T curve that adopts the bismuth liquid furnace to record.As long as determined that with the method the heating bath temperature is higher than 5 ℃～20 ℃ of Curie temperature, keep 20min just can be reduced to the sintered Nd-Fe-B permanent magnet residual magnetism below the 2mT with interior.
Employing heating bath heating, demagnetization temperature and time are significantly less than vacuum furnace or the demagnetization of box type furnace heat, can better transmit heat, shorten heating time, thereby guarantee to handle the quality of back product.
The present invention also provides the stew demagnetizing sintered Nd iron boron permanent magnet device of using said method, comprise circulation thermal source, processing body of heater, cooling system and the controlling organization of being with thermal medium, handle the body of heater lower part and bring outlet into, the gas outlet is brought on top into, and loam cake is opened a lifting rod hole, and lifting rod inserts in the hole, termination one workpiece basket under the lifting rod, the lifting rod upper end links to each other with elevating mechanism, and elevating mechanism is controlled lifting by controlling organization, and oil inlet and outlet is connected with the circulation thermal source; The temperature of the thermal medium of circulation thermal source and circulation be by controlling organization control, and circulation thermal source medium also with the cooling system heat exchange, the opening and closing of cooling system are controlled by controlling organization.
Above-mentioned cycling hot origin system comprises fuel tank, pipeline, hot oil pump, heater, temperature sensor, high-temperature solenoid valve, controller, by pipeline fuel tank, hot oil pump, heater are linked together and to constitute the loop, and temperature sensor and high-temperature solenoid valve are set on pipeline, heater, hot oil pump, temperature sensor and high-temperature solenoid valve link to each other with controller and control.
After device starts, set earlier to handle and need temperature, start the thermal source medium circulation then, enter and handle in the stove to required liquid level, during to design temperature, start elevating mechanism decline lifting rod, the workpiece basket that the sintered Nd-Fe-B permanent magnet workpiece is housed of lifting rod lower end is immersed in the thermal medium, by elevating mechanism the lifting rod pull-up is cooled off again after being dipped to setting-up time.
If the easy oxidation of above-mentioned circulating thermal medium then feeds protective gas by the air inlet/outlet of handling stove top, also can prevent the surface oxidation of permanent magnet.
Above-mentioned circulation thermal source also can constantly heat in circulation and stop circulation when arriving set temperature required.
Sintered Nd-Fe-B permanent magnet has considerable influence with heat transfer medium in the character that contacts sintered Nd-Fe-B permanent magnet more than 150 ℃, and this section period claims to have the time of contact of warm period.Have and comprise time of contact of warm period temperature rise period, holding stage and temperature-fall period.For guaranteeing product quality, must shorten the time of contact that the warm period is arranged, preferably be controlled in the 30min.
Said apparatus adopts transmitting medium to immerse to temperature back sintered Nd-Fe-B permanent magnet again, after insulation finishes, adopt 2 above coolers, progressively increase the cooler number in the different periods, the control cooling rate, temperature is pressed approximately linear and is descended, and perhaps adopts the frozen water medium to come the cooler of cycling hot origin system to carry out the Rapid Thermal exchange, 15 ℃/min of average cooldown rate control.
The heat pump forced circulation is the combined thermal transmission mode of convection current and conduction heat transfer between magnet and the conduction oil, and the magnet heat exchange is fast, and magnet reaches the demagnetization temperature of actual needs or cooling fast at the utmost point in the short time.
Above-mentioned elevating mechanism can be common crane, also can be the lifting tool that other can be controlled.
Above-mentioned controller can adopt the PLC programming to realize, this device needs the lifting of control elevating mechanism, heating, temperature and the circulation of thermal medium, the control of cooling system, and these control modes are comparatively simple, therefore is not described in detail.
Compared with prior art, the invention has the advantages that:
Employing heating bath heating can reduce heating-up temperature, improves the efficiency of heating surface, thereby shortens the processing time, reduces production costs, and guarantees product quality, makes the maximum magnetic energy product (BH) of sintered Nd-Fe-B permanent magnet magnetic property
MaxRate of change is in-2%, and the performance variation is little, sees embodiment for details.
The present invention can handle the sintered Nd-Fe-B permanent magnet of the high trade mark such as N50, N52, N55 series, thereby applicability is wide.
Description of drawings
The N50 sintered Nd-Fe-B permanent magnet thermal analysis curve of Fig. 1 for adopting DSC to record.
The N50 sintered Nd-Fe-B permanent magnet D-3T curve of Fig. 2 for adopting the bismuth liquid furnace to record.
Fig. 3 is the structural representation of the processing body of heater of the hot demagnetizer of sintered Nd-Fe-B permanent magnet oil bath of the present invention.
Fig. 4 is the structural representation of the hot demagnetizer of sintered Nd-Fe-B permanent magnet oil bath of the present invention.
Embodiment
Embodiment describes in further detail the present invention below in conjunction with accompanying drawing.
As shown in Figure 3, Figure 4, the hot demagnetizer of a kind of sintered Nd-Fe-B permanent magnet oil bath comprises the cycling hot origin system, handles body of heater 19 and cooling system.
The cycling hot origin system comprises fuel tank 22, hot oil pump 13, heater 14, temperature sensor 15, pipeline, cooling cylinder 31, high-temperature solenoid valve 11, water solenoid valve 34, controller.
Handle body of heater 19 tops and bring oil-out 1,2 into, gas outlet 3,4 is brought on top into, lifting rod 5 is stretched at flange form loam cake 8 centers, flange form loam cake 8 is fixed on the body of heater, can seal by high-temperature gasket therebetween, fix by bolt (not drawing among the figure), lifting rod 5 upper end band lifting cranes (not drawing among the figure), lower end band workpiece basket 6.
Cooling system is by the medium heat exchange of cooling cylinder 31 with the cycling hot origin system, and cooling cylinder 31 and cooling cylinder 32 are by pipeline and electromagnetically operated valve 33,34 and valve 35,36 formation circulation circuits.
Below the method according to this invention and device are described the present invention and effect of the present invention in detail again.
Comparative example 1:
5 N50 sintered Nd-Fe-B permanent magnet φ 10 * 10 samples are put into external-heat flue vacuum furnace and are heated up with stove after 50 ℃ of following magnetic surveys, and the demagnetization technical process is intensification 0.5hr, and at 420 ℃ of insulation 1hr, flue proposes body of heater, air cooling 1hr, air-cooled flue.After the cooling, take out sample, test 50 ℃ of magnetic energy, the data before the contrast demagnetization see Table 1.As seen HCJ H
CJVariation is big.
Embodiment 1:
4 42SH sintered Nd-Fe-B permanent magnet φ 10 * 11 samples are dried in baking oven 80 ℃ of following magnetic surveys again.Then sample is put into workpiece basket 6, puts high-temperature gasket, flange 8, and lifting rod 5 and workpiece basket fishhook are by the sealing body of heater that tights a bolt.Gas feed 3 feeds inert gas, air in the gas displacement body of heater, and gas vent 4 forms the Buchholz protection loop again.By lifting rod 5 sample is suspended in the body of heater 19, does not contact fluid.Open high-temperature solenoid valve 11, open high-temperature solenoid valve 17, open hand-operated valve 18, start hot oil pump 13, form " injection loop 1. ".When level sensor 12 provides down liquid level signal, close high-temperature solenoid valve 11, start heater 14, temperature sensor 15,20 is to temperature controller control conduction oil temperature.Form " heating circuit 2. " by oil-in 1, oil-out 2, temperature sensor 20, hot oil pump 13, heater 14, temperature sensor 15, pressure sensor 16, high-temperature solenoid valve 17 and hand-operated valve 18.Intensification 15min transfers by lifting rod 5 to 330 ℃ of temperature, makes sample immerse in the body of heater 19 interior conduction oils 7 insulation 5min.Insulation finishes, close heater 14, open electromagnetically operated valve 33, make cooling water enter cooling cylinder 32, cooling water and conduction oil heat exchange in the cooling cylinder, temperature descends, when being cooled to 250 ℃, opening and open electromagnetically operated valve 34, make cooling water also to enter cooling cylinder 31 and quicken cooling.Cool off and carried lifting rod 5 on 150 ℃ in 10 minutes, sample breaks away from conduction oil 7 liquid levels.Be cooled to 60 ℃, open high-temperature solenoid valve 21, close high-temperature solenoid valve 17, form " the oil return loop 3. " by oil-out 2, temperature sensor 20, hot oil pump 13, temperature sensor 15, pressure sensor 16, high-temperature solenoid valve 21 and fuel tank 10.Oil return finishes, and closes hot oil pump 13, closes the inert gas source of the gas, unclamps bolt 10, opens flange 8, takes out sample.Test 80 ℃ of magnetic energy, the data before the contrast demagnetization see Table 2.The magnetic property of sample sequence number 9 (BH)
MaxChange maximum, be-0.96%.
Embodiment 2:
In same block of sintered Nd-Fe-B permanent magnet 48H blank, cut out φ 10 * 11 samples, extract 3 vacuum demagnetizations, 3 with together sampling technology demagnetization of embodiment again, the two is with sampling technology chamfering, electroplated Ni CuNi, test 80 ℃ of magnetic properties, press φ 10 but magnetic survey is unified, the data that record see Table 3, as can be seen, demagnetization technology H of the present invention
CJHigher.
Embodiment 3:
38H specification R2.9 * 10.4 * 5.8 * 1.3 of band magnetic are through plating Zn sintered Nd-Fe-B permanent magnet, and 335 ℃ * 10min oil bath is demagnetized in the device that embodiment one mentions.Respectively before demagnetization and after randomly draw 20pcs and test magnetic flux, the magnetic flux mean variation is less than 1% as a result.
50 ℃ of magnetic property contrasts of table 1 sintered Nd-Fe-B permanent magnet external-heat flue vacuum demagnetization
80 ℃ of magnetic property contrasts of table 2 42SH sintered Nd-Fe-B permanent magnet immersion oil heat demagnetization
The demagnetization of table 3 48H sintered Nd-Fe-B permanent magnet vacuum and 80 ℃ of magnetic property contrasts of oil bath heat demagnetization
Claims (1)
1. stew demagnetizing sintered Nd iron boron permanent magnet device, it is characterized in that: comprise circulation thermal source, processing body of heater, cooling system and the controlling organization of being with thermal medium, handle upper of furnace body and bring oil-out into, the gas outlet is brought on top into, loam cake is opened a lifting rod hole, lifting rod inserts in the hole, termination one workpiece basket under the lifting rod, and the lifting rod upper end links to each other with elevating mechanism; Elevating mechanism is controlled lifting by controlling organization, and oil inlet and outlet is connected with the circulation thermal source; The temperature of the thermal medium of circulation thermal source and circulation be by controlling organization control, and circulation thermal source medium also with the cooling system heat exchange, the opening and closing of cooling system are controlled by controlling organization; The cycling hot origin system comprises fuel tank, pipeline, hot oil pump, heater, temperature sensor, high-temperature solenoid valve, controller, by pipeline fuel tank, hot oil pump, heater are linked together and to constitute the loop, and temperature sensor and high-temperature solenoid valve are set on pipeline, heater, hot oil pump, temperature sensor and high-temperature solenoid valve link to each other with controller and control; The medium of described cooling system is a frozen water, by interchanger and the heat exchange of thermal source medium; After device starts, set earlier to handle and need temperature, start the thermal source medium circulation then, enter and handle in the stove to required liquid level, during to design temperature, start elevating mechanism decline lifting rod, the workpiece basket that the sintered Nd-Fe-B permanent magnet workpiece is housed of lifting rod lower end is immersed in the thermal medium, by elevating mechanism the lifting rod pull-up is cooled off again after being dipped to setting-up time.
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| CN102943279A (en) * | 2012-11-14 | 2013-02-27 | 安徽大地熊新材料股份有限公司 | Method for processing neodymium iron boron magnetic body after being demagnetized |
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| CN102943279A (en) * | 2012-11-14 | 2013-02-27 | 安徽大地熊新材料股份有限公司 | Method for processing neodymium iron boron magnetic body after being demagnetized |
| CN102943279B (en) * | 2012-11-14 | 2014-10-08 | 安徽大地熊新材料股份有限公司 | Method for processing neodymium iron boron magnetic body after being demagnetized |
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Effective date of registration: 20100820 Address after: 315040, Zhejiang Ningbo science and Technology Park, sailing Road No. 1 headquarters of the Ministry of science and technology Applicant after: Ningbo Yunsheng Co., Ltd. Co-applicant after: Ningbo Yusheng High-Tech Magnetics Co., Ltd. Co-applicant after: Baotou Yunsheng Strong Magnetic Material Co., Ltd. Address before: 315040 Zhejiang province Ningbo City Jiangdong District Road No. 348 Min'an Applicant before: Ningbo Yunsheng Co., Ltd. |
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