CN-114284020-B - Hydrogen crushing method of neodymium-iron-boron alloy and preparation method of neodymium-iron-boron magnet

CN114284020BCN 114284020 BCN114284020 BCN 114284020BCN-114284020-B

Abstract

The invention discloses a hydrogen crushing method of neodymium iron boron alloy. The method comprises the steps of (1) absorbing hydrogen for the first time, then dehydrogenating for the first time, and cooling to obtain pre-hydrogenated crushed NdFeB, wherein the hydrogen content of the pre-hydrogenated crushed NdFeB is more than 1800ppm, and (2) absorbing hydrogen for the second time, then dehydrogenating for the second time, and cooling to obtain NdFeB coarse powder. The method can improve the coercive force of the neodymium-iron-boron magnet and does not influence the remanence. The invention also discloses a preparation method of the neodymium-iron-boron magnet.

Inventors

LI ZHIQIANG
ZHANG XIUQI
DIAO SHULIN
DONG YI
WU SHUJIE
WU ZHIMIN
YUAN YI
CHEN YA
YUAN WENJIE

Assignees

包头天和磁材科技股份有限公司
包头天和磁材科技股份有限公司

Dates

Publication Date: 20260421
Application Date: 20220114
Priority Date: 20220114

Claims (10)

1. The hydrogen crushing method of the neodymium iron boron alloy is characterized by comprising the following steps of: (1) The preparation method comprises the steps of firstly absorbing hydrogen from a neodymium-iron-boron alloy sheet, then dehydrogenating for the first time, and cooling to obtain pre-hydrogenated crushed neodymium-iron-boron, wherein the hydrogen content of the pre-hydrogenated crushed neodymium-iron-boron is more than 2000ppm, the first hydrogen absorption pressure is 0.010-0.200 MPa, the first hydrogen absorption time is 0.3-4 h, the first dehydrogenation temperature is 400-700 ℃, and the first dehydrogenation time is 2-6 h; (2) And carrying out secondary hydrogen absorption on the pre-hydrogenated crushed neodymium iron boron, then carrying out secondary dehydrogenation and cooling to obtain neodymium iron boron coarse powder, wherein the secondary hydrogen absorption time is 0.3-4 h, the secondary hydrogen absorption pressure is 0.010-0.200 MPa, the secondary dehydrogenation temperature is 400-700 ℃, and the secondary dehydrogenation time is 7-12 h.
2. The hydrogen crushing method according to claim 1, wherein the first time of hydrogen absorption is 0.5 to 3 hours and the first time of hydrogen absorption is 0.050 to 0.150mpa.
3. The hydrogen crushing method according to claim 1, wherein the second time of hydrogen absorption is 0.5 to 3 hours and the second pressure of hydrogen absorption is 0.050 to 0.150mpa.
4. The hydrogen crushing method according to claim 1, wherein the first dehydrogenation is performed at 450 to 650 ℃ for 3 to 5 hours.
5. The hydrogen crushing method according to claim 1, wherein the first dehydrogenation time includes a first temperature rise time and a first heat preservation time, the first temperature rise time is 0.5 to 3 hours, and the first heat preservation time is 1 to 4 hours.
6. The hydrogen crushing method according to claim 1, wherein the second dehydrogenation temperature is 450-650 ℃ and the second dehydrogenation time is 8-11 h.
7. The hydrogen crushing method according to claim 1, wherein the second dehydrogenation time includes a second temperature rise time and a second heat preservation time, the second temperature rise time is 0.5 to 3 hours, and the second heat preservation time is 5 to 10 hours.
8. The hydrogen crushing method according to claim 1, wherein the neodymium iron boron alloy sheet contains 50-70wt% of iron, 20-45wt% of praseodymium and neodymium, 0.5-2.5wt% of aluminum, 0.3-2wt% of boron, 0.5-2.5wt% of cobalt, 0.01-0.5wt% of gallium and 0.01-0.5wt% of zirconium.
9. The preparation method of the neodymium-iron-boron magnet is characterized by comprising the following steps of: The method for hydrogen crushing according to any one of claims 1-8 is adopted to obtain neodymium iron boron coarse powder, the neodymium iron boron coarse powder is subjected to air current grinding to obtain neodymium iron boron fine powder, the neodymium iron boron fine powder is pressed and molded to obtain a neodymium iron boron blank, the neodymium iron boron blank is sintered for 3-7 h at 1000-1200 ℃, treated for 1-5 h at 700-950 ℃ and treated for 3-7 h at 380-550 ℃ in sequence, and the neodymium iron boron magnet is obtained.
10. The method for improving the coercive force of the NdFeB magnet is characterized by comprising the following steps of: (1) The preparation method comprises the steps of firstly absorbing hydrogen from a neodymium-iron-boron alloy sheet, then dehydrogenating for the first time, and cooling to obtain pre-hydrogenated crushed neodymium-iron-boron, wherein the hydrogen content of the pre-hydrogenated crushed neodymium-iron-boron is more than 2000ppm, the first hydrogen absorption pressure is 0.010-0.200 MPa, the first hydrogen absorption time is 0.3-4 h, the first dehydrogenation temperature is 400-700 ℃, and the first dehydrogenation time is 2-6 h; (2) The method comprises the steps of carrying out secondary hydrogen absorption on the pre-hydrogenated crushed neodymium iron boron, carrying out secondary dehydrogenation and cooling to obtain neodymium iron boron coarse powder, wherein the secondary hydrogen absorption time is 0.3-4 h, the secondary hydrogen absorption pressure is 0.010-0.200 MPa, the secondary dehydrogenation temperature is 400-700 ℃, and the secondary dehydrogenation time is 7-12 h; (3) Carrying out air current grinding treatment on the neodymium iron boron coarse powder to obtain neodymium iron boron fine powder; (4) Pressing and forming the neodymium iron boron fine powder to obtain a neodymium iron boron blank; (5) And sintering the neodymium iron boron blank for 3-7 hours at 1000-1200 ℃, treating for 1-5 hours at 700-950 ℃ and treating for 3-7 hours at 380-550 ℃ to obtain the neodymium iron boron magnet.

Description

Hydrogen crushing method of neodymium-iron-boron alloy and preparation method of neodymium-iron-boron magnet Technical Field The invention relates to a hydrogen crushing method of a neodymium-iron-boron alloy and also relates to a preparation method of a neodymium-iron-boron magnet. Background The sintered NdFeB magnet has the characteristics of outstanding magnetic performance, high efficiency, energy conservation, light weight, small volume, good control and speed regulation performance and the like, and has been widely applied since the advent of 1983. The coercive force and the remanence are two important indexes for measuring the sintered NdFeB magnet, and are usually improved by adjusting the composition of raw materials and the preparation process. The addition of the heavy rare earth element to the sintered neodymium-iron-boron magnet can improve the coercive force of the sintered neodymium-iron-boron magnet, but the existence of the heavy rare earth element can reduce the residual magnetism of the sintered neodymium-iron-boron magnet. The traditional hydrogen crushing method is one-time hydrogen absorption and mainly comprises the following four stages. The first stage is that the surface of the throwing piece is activated, and no hydrogen absorption reaction occurs in the stage. And in the second stage, the neodymium-rich phase on the surface of the throwing piece absorbs hydrogen, and the neodymium-rich phase Nd and hydrogen are combined into NdH x compounds in the process. Since the neodymium-rich phase accounts for less than 10% of the volume fraction, less heat is emitted. After the hydrogen absorption of the neodymium-rich phase, the crystal boundary of the fling crystal is broken, and the main phase becomes single crystal large particles in the crystal reaction process. And in the third stage, hydrogen gas moves inwards to a main phase along a grain boundary to start a main phase hydrogen absorption process, and a large amount of heat is released in the process to form an Nd 2Fe14BHy compound. After the main phase hydrogen absorption process, the large-grain single crystal main phase becomes small grains. And in the fourth stage, hydrogen breaks the center of the throwing piece, and a plurality of crack turning occurs due to the main phase hydrogen absorption, so that the crack turning from outside to inside becomes smaller and more. With the increase of heat release and temperature, the increase of crack turning, the diffusion of hydrogen to the center of the throwing piece is slow, the hydrogen absorption amount is reduced, partial neodymium-rich phase and main phase grains do not fully absorb hydrogen, and the performance of the neodymium-iron-boron magnet is affected by the partial neodymium-rich phase and main phase grains. CN103537705A discloses a hydrogen crushing process of sintered neodymium iron boron permanent magnet material. Loading neodymium iron boron cast sheets into a hydrogen crushing furnace, heating the neodymium iron boron cast sheets to 60-150 ℃, introducing nitric oxide into the hydrogen crushing furnace for activation treatment, stopping introducing nitric oxide, vacuumizing, introducing argon, replacing the nitric oxide in the furnace, vacuumizing again to ensure that the concentration of the nitric oxide in the furnace in parts by weight is less than 100ppm, introducing hydrogen into the hydrogen crushing furnace, and expanding the neodymium iron boron cast sheets to be crushed into powder. The technology solves the problem of uneven hydrogen absorption of sintered NdFeB cast sheets by carrying out activation treatment on the cast sheets, thereby improving the magnetic performance. CN105405563A discloses a hydrogen crushing method of a neodymium-iron-boron magnet, which comprises the following steps of putting a neodymium-iron-boron semi-finished product into a hydrogen crushing device, vacuumizing, introducing protective gas and hydrogen into the hydrogen crushing device to perform hydrogen absorption reaction, vacuumizing, and then performing heating dehydrogenation reaction to obtain neodymium-iron-boron raw material fine powder. The method uniformly disperses small molecular hydrogen into the furnace chamber by means of the pressure of protective gas, and ensures that neodymium iron boron semi-finished products at each part can react with the hydrogen, thereby ensuring that the neodymium iron boron semi-finished products can be fully crushed. However, the method cannot fully absorb hydrogen in the core of the NdFeB semi-finished product and break the core, so that the improvement range of the magnetic performance of the NdFeB semi-finished product is small. CN111029075A discloses a preparation method of neodymium iron boron magnetic powder. According to the method, according to the difference of hydrogen absorption reaction temperatures of a neodymium-rich phase and a main phase in the neodymium-iron-boron alloy, the neodymium-rich phase and the main phase are r