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Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet

A permanent magnet and neodymium-iron-boron technology, which is applied in the direction of magnetic objects, magnetic materials, inorganic materials, etc., can solve the problems of high heating temperature, difficult heat dissipation of permanent magnets, and large energy consumption, and achieve the effect of wide applicability

Active Publication Date: 2008-10-01
NINGBO YUNSHENG +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method has the following disadvantages: the heating temperature is too high; if the temperature is kept at about 420°C, the surface oxide layer of the permanent magnet will appear, and it can only be used for blanks, that is, intermediate products that require subsequent machining
Using a vacuum sintering furnace, since the heat of the permanent magnet in the furnace is not easy to dissipate and the cooling speed is slow, the intrinsic coercive force of the permanent magnet's magnetic properties is reduced or the square diagram of the demagnetization curve is not good.
And although it is direct heating, due to the small vacuum heat transfer coefficient in vacuum, it mainly relies on radiation heating, so it still needs a long heating time and a large thermal gradient. equipment, and consume a lot of energy, resulting in a waste of resources

Method used

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  • Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet
  • Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet
  • Method and apparatus for stew demagnetizing sintered Nd iron boron permanent magnet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0048] Four 42SH sintered NdFeB permanent magnet φ10×11 samples were magnetically measured at 80°C, and then dried in an oven. Then put the sample into the workpiece basket 6, put the high-temperature gasket, the flange 8, the lifting rod 5 and the hook of the workpiece basket, and seal the furnace body by tightening the bolts. The gas inlet 3 is fed with inert gas, the gas replaces the air in the furnace body, and then the gas outlet 4 forms a gas protection circuit. The sample is suspended in the furnace body 19 through the lifting rod 5 without contacting the oil. Open the high-temperature electromagnetic valve 11, open the high-temperature electromagnetic valve 17, open the manual valve 18, and start the hot oil pump 13 to form an "oil injection circuit ①". When the liquid level detector 12 gives a lower liquid level signal, the high temperature solenoid valve 11 is closed, the heater 14 is started, and the temperature sensors 15 and 20 control the temperature of the heat...

Embodiment 2

[0050] Cut out φ10×11 samples from the same sintered NdFeB permanent magnet 48H blank, take 3 samples for vacuum demagnetization, and then 3 samples for demagnetization with the same process as in Example 1, the same process for chamfering and electroplating NiCuNi for both, and test the magnetic properties at 80 °C can, but the magnetic survey is unified by φ10, and the data recorded are shown in Table 3, as can be seen, the demagnetization process H of the present invention cJ higher.

Embodiment 3

[0052] The magnetized 38H specification R2.9×10.4×5.8×1.3 is sintered with Zn-plated NdFeB permanent magnet, and demagnetized in an oil bath at 335°C×10min in the device mentioned in Example 1. 20pcs were randomly selected before and after demagnetization to test the magnetic flux, and the average change of the magnetic flux was less than 1%.

[0053] Table 1 Comparison of magnetic properties of sintered NdFeB permanent magnets with external heating furnace for vacuum demagnetization at 50°C

[0054]

[0055] Table 2 Comparison of magnetic properties of 42SH sintered NdFeB permanent magnets immersed in oil and thermally demagnetized at 80°C

[0056]

[0057] Table 3 Comparison of magnetic properties of 48H sintered NdFeB permanent magnets under vacuum demagnetization and oil bath thermal demagnetization at 80°C

[0058]

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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 [0001] The invention relates to a processing method and device for magnetic materials, in particular to a processing method and device for demagnetizing sintered NdFeB permanent magnets. Background technique [0002] Since its invention in 1983, sintered NdFeB permanent magnets have been widely used in electroacoustics, signal detection, medical, scientific research, energy-saving household appliances, computers, Vibration motors for mobile phones, permanent magnet wind turbines, precision linear motors, CD and VCD optical read heads, motors for various elevators, and high-speed liquid pumps, etc. At present, the output of sintered NdFeB permanent magnets in my country has accounted for more than 70% of the world's total output, with an annual output of more than 40,000 tons, becoming the largest producer of sintered NdFeB permanent magnets in the world. [0003] The manufacturing process of sintered NdFeB permanent magnets is sintered blank preparation, mac...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01F1/057H01F1/08H01F13/00
Inventor 沈国迪胡依群赵德荣张民周广
Owner NINGBO YUNSHENG
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