阅读说明：本技术 一种高耐蚀稀土永磁体及其制备方法 (High-corrosion-resistance rare earth permanent magnet and preparation method thereof ) 是由 毛华云 毛琮尧 孙长山 赖欣 于 2020-11-30 设计创作，主要内容包括：本发明提供了一种高耐蚀稀土永磁体的制备方法,包括：将合金原料配料后进行熔炼,然后甩带,得到铸片；将所述铸片进行氢破碎后再进行气流磨,得到细粉颗粒；将所述细粉颗粒和金属氧化物纳米粉混合,得到混合粉体；将所述混合粉体进行磁场压制后烧结,得到高耐蚀稀土永磁体。本发明通过将制得的粉末添加一定量的纳米级金属氧化物,搅拌均匀后进行取向压型、烧结成高剩磁的磁体,通过烧结后氧化物大部分分布在三角晶界(三个晶粒边界的交合点)上,降低了晶界或三角晶界和主相之间的电位差,晶界相得到了更好的化学稳定性,从而得到耐腐蚀性好的烧结钕铁硼磁体。本发明还提供了一种高耐蚀稀土永磁体。(The invention provides a preparation method of a high-corrosion-resistance rare earth permanent magnet, which comprises the following steps: alloy raw materials are proportioned and then smelted, and then strip casting is carried out to obtain a cast sheet; carrying out hydrogen crushing on the cast piece, and then carrying out jet milling to obtain fine powder particles; mixing the fine powder particles with metal oxide nano powder to obtain mixed powder; and (3) carrying out magnetic field pressing on the mixed powder and then sintering to obtain the high-corrosion-resistance rare earth permanent magnet. According to the invention, a certain amount of nano-scale metal oxide is added into the prepared powder, the powder is uniformly stirred and then subjected to orientation compression and sintering to form a high-remanence magnet, most of the sintered oxide is distributed on a triangular crystal boundary (a junction point of three crystal grain boundaries), so that the potential difference between the crystal boundary or the triangular crystal boundary and a main phase is reduced, the crystal boundary phase obtains better chemical stability, and the sintered neodymium-iron-boron magnet with good corrosion resistance is obtained. The invention also provides a high-corrosion-resistance rare earth permanent magnet.)

1. A preparation method of a highly corrosion-resistant rare earth permanent magnet comprises the following steps:

alloy raw materials are proportioned and then smelted, and then strip casting is carried out to obtain a cast sheet;

carrying out hydrogen crushing on the cast piece, and then carrying out jet milling to obtain fine powder particles;

mixing the fine powder particles with metal oxide nano powder to obtain mixed powder;

performing magnetic field pressing on the mixed powder and then sintering to obtain the high-corrosion-resistance rare earth permanent magnet;

the metal oxide nano powder comprises the following components:

Rx-My-Oz；

wherein R is a rare earth element and comprises one or more of Nd, Pr and Y;

m is at least one element selected from Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd and Mo;

50wt％≤x；0.1wt％≤y≤20wt％；z＞10wt％。

2. the method of claim 1, wherein R is Nd; m is selected from one or more of Cu, Ti and Zr.

3. The method of claim 1, wherein x is 70 wt% to 85 wt%; y is more than or equal to 5 wt% and less than or equal to 15 wt%, and z is more than or equal to 15 wt% and less than or equal to 20 wt%.

4. The method according to claim 1, wherein the metal oxide nanopowder has a particle size of 100 to 300 nm.

5. The method according to claim 1, wherein the alloy feedstock is formulated to have a composition of:

R1_x1Fe_{(100-x1-y1-z1)}M1_y1B_z1，

wherein x1 is more than or equal to 28 weight percent and less than or equal to 33 weight percent; y1 is more than or equal to 0.1 weight percent and less than or equal to 3.0 weight percent; z1 is more than or equal to 0.85 weight percent and less than or equal to 1.0 weight percent;

r1 is selected from rare earth elements including praseodymium and/or neodymium;

m1 is at least one element selected from the group consisting of Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd, and Mo.

6. The method of claim 1, wherein the cast slab has a thickness of 0.3 to 0.5 mm.

7. The method of claim 1, wherein the fine powder particles have a particle size of 2.5 to 4.5 microns.

8. The method according to claim 1, wherein the metal oxide nanopowder is present in the mixed powder in an amount of 0.1 to 1 wt%.

9. The method of claim 1, wherein the sintering temperature is 1020 to 1060 ℃ and the sintering time is 4 to 10 hours.

10. A highly corrosion-resistant rare earth permanent magnet prepared by the method of claim 1.

Technical Field

The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a high-corrosion-resistance rare earth permanent magnet and a preparation method thereof.

Background

As is well known, with Nd₂Fe₁₄Compounds of type BThe R-Fe-B-based rare earth sintered magnet as a main phase is a magnet having the highest performance among all magnetic materials of permanent magnets, and is widely used for a Voice Coil Motor (VCM) for hard disk drive, a servo motor, a variable frequency air conditioner motor, a motor for mounting a hybrid vehicle, and the like. As a porous material prepared by a powder metallurgy process, the neodymium-rich phase, the main phase and the boundary phase of the neodymium iron boron are easy to form intergranular corrosion. The rare earth element neodymium in the neodymium-iron-boron powder alloy has active property, so that the corrosion resistance of the whole neodymium-iron-boron alloy is very poor, and the neodymium-iron-boron powder alloy is very easy to rust and corrode in a damp and hot environment. The sintered neodymium iron boron has the biggest defects that the corrosion resistance of a base body is poor, and a product is easy to oxidize and rust in the production and manufacturing process, so that the yield of the product in the manufacturing process is influenced; meanwhile, the service life of the product is influenced due to poor corrosion resistance in the using process of the product. The corrosion prevention problem of the neodymium iron boron permanent magnet material is always a main problem to be solved.

In the existing traditional method, corrosion-resistant elements such as cobalt, copper and the like are added in the smelting stage of the alloy, firstly, a rare earth metal alloy is prepared by a strip casting (rapid hardening) method, and the strip casting alloy is subjected to hydrogen crushing, airflow grinding to prepare powder, and the prepared powder is uniformly stirred, oriented, pressed and sintered to form a high-corrosion-resistant magnet. The corrosion of sintered Nd-Fe-B mainly starts from grain boundaries, especially triangular grain boundaries, because the grain boundaries and the main phase have larger composition difference and the potential difference is larger. In the traditional method, corrosion resistant elements such as cobalt, copper and the like are added in the smelting stage of the alloy to improve the corrosion resistance of the base material, however, the added corrosion resistant elements such as cobalt, copper and the like have very little potential difference for changing the main phase and the grain boundary in the magnet, and the stability for improving the grain boundary is limited, so the corrosion resistance of the base material is not obvious, and the cost is higher.

Disclosure of Invention

In view of this, the present invention aims to provide a highly corrosion-resistant rare earth permanent magnet and a method for preparing the same.

The invention provides a preparation method of a high-corrosion-resistance rare earth permanent magnet, which comprises the following steps:

alloy raw materials are proportioned and then smelted, and then strip casting is carried out to obtain a cast sheet;

carrying out hydrogen crushing on the cast piece, and then carrying out jet milling to obtain fine powder particles;

mixing the fine powder particles with metal oxide nano powder to obtain mixed powder;

performing magnetic field pressing on the mixed powder and then sintering to obtain the high-corrosion-resistance rare earth permanent magnet;

the metal oxide nano powder comprises the following components:

Rx-My-Oz；

wherein R is a rare earth element and comprises one or more of Nd, Pr and Y;

m is at least one element selected from Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd and Mo;

50wt％≤x；0.1wt％≤y≤20wt％；z＞10wt％。

preferably, R is Nd; m is selected from one or more of Cu, Ti and Zr.

Preferably, x is more than or equal to 70 wt% and less than or equal to 85 wt%; y is more than or equal to 5 wt% and less than or equal to 15 wt%, and z is more than or equal to 15 wt% and less than or equal to 20 wt%.

Preferably, the granularity of the metal oxide nano powder is 100-300 nm.

Preferably, the alloy raw material comprises the following components after proportioning:

R1_x1Fe_{(100-x1-y1-z1)}M1_y1B_z1，

wherein x1 is more than or equal to 28 weight percent and less than or equal to 33 weight percent; y1 is more than or equal to 0.1 weight percent and less than or equal to 3.0 weight percent; z1 is more than or equal to 0.85 weight percent and less than or equal to 1.0 weight percent;

r1 is selected from rare earth elements including praseodymium and/or neodymium;

m1 is at least one element selected from the group consisting of Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd, and Mo.

Preferably, the thickness of the casting sheet is 0.3-0.5 mm.

Preferably, the particle size of the fine powder particles is 2.5-4.5 microns.

Preferably, the mass content of the metal oxide nano powder in the mixed powder is 0.1-1 wt%.

Preferably, the sintering temperature is 1020-1060 ℃, and the sintering time is 4-10 hours.

The invention provides a high-corrosion-resistance rare earth permanent magnet prepared by the method in the technical scheme.

The invention prepares a rare earth metal alloy by a melt-spun (rapid hardening) method, the melt-spun (rapid hardening) alloy is pulverized by hydrogen crushing and airflow milling, a certain amount of nano-scale metal oxide is added into the prepared powder, the powder is uniformly stirred and then is subjected to orientation compression and sintering to form a high-remanence magnet, most of the sintered oxide is distributed on a triangular crystal boundary (the intersection point of three crystal grain boundaries, as shown in figure 1), the potential difference between the crystal boundary or the triangular crystal boundary and a main phase is reduced, the crystal boundary phase obtains better chemical stability, and thus the sintered neodymium iron boron magnet with good corrosion resistance is obtained.

In the sintered Nd-Fe-B crystal boundary, the main phase alloy is not melted basically, the metal oxide nano alloy is mainly distributed in the crystal boundary phase of the magnet, and the high-temperature corrosion resistance of the magnet can be greatly improved only by a small amount of the metal oxide nano alloy. Meanwhile, the metal oxide nano alloy is mainly distributed in a grain boundary phase, so that the magnetic performance of the neodymium iron boron magnet cannot be damaged. Therefore, on the premise that the magnetic performance of the magnet is basically not influenced, only a trace amount of metal is added, and the high-temperature corrosion resistance of the neodymium iron boron magnet is greatly improved.

Drawings

FIG. 1 is a schematic diagram and an enlarged view of the main phase and grain boundary phase of the highly corrosion-resistant rare earth permanent magnet prepared by the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other examples, which may be modified or appreciated by those of ordinary skill in the art based on the examples given herein, are intended to be within the scope of the present invention. It should be understood that the embodiments of the present invention are only for illustrating the technical effects of the present invention, and are not intended to limit the scope of the present invention. In the examples, the methods used were all conventional methods unless otherwise specified.

The invention provides a preparation method of a high-corrosion-resistance rare earth permanent magnet, which comprises the following steps:

alloy raw materials are proportioned and then smelted, and then strip casting is carried out to obtain a cast sheet;

carrying out hydrogen crushing on the cast piece, and then carrying out jet milling to obtain fine powder particles;

mixing the fine powder particles with metal oxide nano powder to obtain mixed powder;

and (3) carrying out magnetic field pressing on the mixed powder and then sintering to obtain the high-corrosion-resistance rare earth permanent magnet.

In the present invention, the alloy raw materials include a rare earth element, a boron element, an iron element, and an M1 metal element; the rare earth elements comprise praseodymium and/or neodymium, and preferably also comprise one or more of dysprosium, terbium, holmium, gadolinium and cerium; the M1 metal element is at least one element selected from Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd and Mo. In the invention, the alloy raw materials comprise the following components after being mixed:

R1_x1Fe_{(100-x1-y1-z1)}M1_y1B_z1，

wherein x1 is more than or equal to 28 weight percent and less than or equal to 33 weight percent; 0.1 wt% or more and 3.0 wt% or less of y1, preferably 0.5 wt% or more and 2.5 wt% or less of y1, more preferably 1.0 wt% or more and 2.0 wt% or less of y 1; z1 is more than or equal to 0.85 weight percent and less than or equal to 1.0 weight percent; x1, y1 and z1 are all in percentage by mass.

R1 is selected from rare earth elements in the alloy raw material in the technical scheme;

m1 is selected from the M1 metal element described in the above technical scheme;

b is boron element.

In the present invention, the alloy material preferably has a composition after compounding (PrNd)_31.3Fe_64.45Dy_0.8Ti_0.15Cu_0.25Co_1.5Al_0.3Ga_0.3B_0.95、Nd_30.5Fe_67.53Ti_0.18Cu_0.17Co_0.5Al_0.1Ga_0.1B_0.92Or Nd₂₈Fe_67.7Tb₂Ti_0.15Cu_0.15Co_0.8Al_0.15Ga_0.15B_0.9。

In the invention, the smelting is preferably vacuum smelting, and the temperature in the smelting process is preferably 1410-1490 ℃, more preferably 1430-1470 ℃, and most preferably 1450 ℃; the smelting is preferably carried out under argon conditions of < 50 KPa.

In the invention, the strip-spinning is a rapid hardening process, and the rotating speed of a copper roller in the strip-spinning process is preferably 1-1.5 m/s, more preferably 1.1-1.3 m/s, and most preferably 1.2 m/s.

In the invention, the thickness of the casting sheet is preferably 0.3-0.5 mm, and more preferably 0.4 mm.

In the present invention, the hydrogen fragmentation preferably comprises: and preserving heat for dehydrogenation after saturated hydrogen absorption.

In the invention, the temperature of the heat preservation dehydrogenation is preferably 560-600 ℃, more preferably 570-590 ℃, and most preferably 580 ℃; the heat preservation dehydrogenation time is preferably 3-7 h, more preferably 4-6 h, and most preferably 5 h.

In the invention, the grinding pressure in the jet milling process is preferably 0.5-0.7 MPa, more preferably 0.55-0.6 MPa, and most preferably 0.58 MPa; the rotating speed of the sorting wheel is preferably 3500-4000 r/min, more preferably 3700-3900 r/min, and most preferably 3800 r/min.

In the invention, the particle size of the fine powder particles is preferably 2.5-4.5 microns, more preferably 3-5 microns, and most preferably 4 microns.

In the invention, the metal oxide nano powder comprises the following components:

Rx-My-Oz；

wherein R is a rare earth element and comprises one or more of Nd, Pr and Y;

m is selected from at least one element of Al, Cu, Zn, Sn, Ga, Ge, Nb, V, W, Ti, Ni, Zr, Ta, Mn, Cd and Mo, preferably selected from one or more of Al, Cu, Zn, Mn and Mo, more preferably selected from one or more of Cu, Ti and Zr;

o is oxygen element;

x is more than or equal to 50 weight percent; y is more than or equal to 0.1 and less than or equal to 20 weight percent; z > 10 wt%; preferably, 70 wt% x 85 wt%, more preferably, 73 wt% x 82 wt%, most preferably, 75 wt% x 80 wt%; preferably, 0.5 wt% or less y 15 wt%, more preferably, 5 wt% or less y 15 wt%, more preferably, 8 wt% or less y 12 wt%, and most preferably, y is 10 wt%; preferably, z is between 15 and 20 wt%; x, y and z are all mass percent.

In the present invention, the component of the metal oxide nano powder is preferably Nd₇₈(CuTi)₉O₁₃、Nd₇₈(TiZr)₉O₁₃Or Nd₇₈(CuZr)₉O₁₃。

In the present invention, the particle size of the metal oxide nanopowder is preferably 100 to 300nm, more preferably 150 to 250nm, and most preferably 200 nm.

The preparation method of the metal oxide nano powder is not particularly limited, and the metal oxide nano powder can be prepared by a preparation method for preparing the metal oxide nano powder, which is well known to those skilled in the art, such as a sol-gel method or a chemical vapor deposition method.

In the present invention, the mass content of the metal oxide nano powder in the mixed powder is preferably 0.1 to 1 wt%, more preferably 0.2 to 0.8 wt%, and most preferably 0.3 to 0.6 wt%.

In the present invention, orientation pressing is preferably performed in a magnetic field, and the method of pressing is preferably isostatic pressing. In the present invention, the magnetic field strength is preferably 1.5T to 1.9T, and more preferably 1.6T to 1.8T. The invention preferably carries out isostatic pressing after compression molding in a magnetic field, and the strength of the isostatic pressing is preferably 190-220 MPa, more preferably 200-210 MPa; higher pressures are more beneficial to material properties, but too high a pressure will tend to increase the safety requirements and also lead to an increase in equipment volume, which in turn leads to increased production costs.

In the invention, the sintering temperature is preferably 1020-1060 ℃, more preferably 1030-1050 ℃, and most preferably 1040 ℃; the sintering time is preferably 4 to 10 hours, more preferably 5 to 8 hours, and most preferably 6 to 7 hours. In the present invention, the sintering is preferably vacuum sintering.

In the present invention, it is preferable that the sintering is completed and then further includes a heat treatment, and the heat treatment preferably includes:

and performing primary aging and secondary aging on the obtained sintered product to obtain the high-corrosion-resistance rare earth permanent magnet.

In the invention, the temperature of the primary aging is preferably 800-920 ℃, more preferably 850-900 ℃, and the heat preservation time is preferably 3-5 h, more preferably 4 h; the temperature of the secondary aging is preferably 480-600 ℃, more preferably 500-550 ℃, and the heat preservation time is preferably 3-5 hours, more preferably 4 hours.

In the present invention, the above aging treatment is optional, and only primary aging may be performed, only secondary aging may be performed, or primary aging may be performed first and then secondary aging may be performed, or no aging treatment may be performed.

The invention also provides the high-corrosion-resistance rare earth permanent magnet prepared by the method in the technical scheme.

In order to improve the high-temperature corrosion resistance of the sintered neodymium-iron-boron magnet, two technical routes can be adopted: firstly, the corrosion resistance of the neodymium iron boron magnet is improved, and secondly, a coating is coated on the surface of the magnet; however, the durability of the corrosion-resistant coating is difficult to meet the actual use requirement, and the invention adopts the technical route of improving the corrosion resistance of the neodymium iron boron magnet. According to the invention, the metal oxide nano powder is added into the sintered neodymium iron boron fine powder particles, and the nano metal oxide is added into the triangular grain boundary phase of the neodymium iron boron magnet, so that the high corrosion resistance of the neodymium iron boron magnet is improved.

A certain amount of nano-scale metal oxide is added into the sintered neodymium iron boron powder, orientation compression and sintering are carried out after uniform stirring to form a high-remanence magnet, most of the sintered oxide is distributed on a triangular crystal boundary, the potential difference between the crystal boundary or the triangular crystal boundary and a main phase is reduced, the nano-oxide particles are very small, the nano-oxide particles can be stably doped in the crystal boundary, and the crystal boundary phase has better chemical stability. The metal oxide has stable chemical performance, strong operability in process and relatively low cost.

Comparative example 1

The alloy components are prepared by a melt spinning (rapid hardening) technology: (PrNd)_31.3Fe_64.45Dy_0.8Ti_0.15Cu_0.25Co_1.5Al_0.3Ga_0.3B_0.95The alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and making the copper roller rotate at 1.2m/s), then adopting hydrogen crushing (580 ℃ after saturated hydrogen absorption for heat preservation and dehydrogenation for 5h) and a gas flow milling process (grinding pressure 0.58MPa, sorting wheel rotation speed 3800r/min) to prepare fine powder with the average grain diameter of 3.2 microns;

orienting the fine powder in a magnetic field of 1.8T, pressing and molding, and isostatic pressing at 200MPa to prepare a green body; and then placing the green body in a sintering furnace, preserving heat for 6 hours at 1040 ℃, and then carrying out two-stage aging treatment, wherein the first-stage aging temperature is 890 ℃, the heat preservation time is 3 hours, the second-stage aging temperature is 550 ℃, and the heat preservation time is 6 hours, so as to obtain the rare earth permanent magnet.

According to the GB/T-3217-2013 magnetic test method for permanent (hard) magnetic materials, the rare earth permanent magnet prepared in comparative example 1 of the invention is subjected to magnetic property detection; the results are shown in Table 1.

The rare earth permanent magnet obtained in comparative example 1 was prepared into two types of magnets of Φ 10mm × 10mm and Φ 15mm × 3mm, 5 in each type, and 20 in total, and subjected to HAST (accelerated aging test) experiments under conditions of 120 ℃, 2atm, and 240 hours; the results are shown in Table 1.

Example 1

The alloy components are prepared by a melt spinning (rapid hardening) technology: (PrNd)_31.3Fe_64.45Dy_0.8Ti_0.15Cu_0.25Co_1.5Al_0.3Ga_0.3B_0.95The alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and making the copper roller rotate at 1.2m/s), then adopting hydrogen crushing (580 ℃ after saturated hydrogen absorption for heat preservation and dehydrogenation for 5h) and air flow milling process (grinding pressure 0.58MPa, sorting wheel rotate speed 3800r/min) to prepare the flat steelFine powder with a mean particle size of 3.2 microns;

the component with the average grain diameter of 100 nm-300 nm is Nd₇₈(CuTi)₉O₁₃Adding oxide nano powder (subscript is mass percentage content) into the fine powder, and uniformly mixing to obtain alloy mixed powder, wherein the mass content of the oxide nano powder in the alloy mixed powder is 0.2%;

orienting the mixed alloy powder in a 1.8T magnetic field, pressing and molding, and isostatic pressing at 200MPa pressure to prepare a green body; and then placing the green body in a sintering furnace, preserving heat for 6 hours at 1040 ℃, and then carrying out two-stage aging treatment, wherein the first-stage aging temperature is 890 ℃, the heat preservation time is 3 hours, the second-stage aging temperature is 550 ℃, and the heat preservation time is 6 hours, so as to obtain the high-corrosion-resistance rare earth permanent magnet.

The highly corrosion-resistant rare earth permanent magnet prepared in example 1 of the present invention was examined for magnetic properties by the method of comparative example 1, and the examination results are shown in Table 1.

The highly corrosion-resistant rare earth permanent magnet prepared in example 1 was prepared into magnets of two specifications of Φ 10mm × 10mm and Φ 15mm × 3mm, 5 magnets per specification, and 20 magnets per specification, and subjected to HAST (accelerated aging test) experiments under conditions of 120 ℃, 2atm, and 240 hours; the test results are shown in Table 1, which shows that the corrosion of the surface of the highly corrosion-resistant rare earth permanent magnet prepared in example 1 of the present invention is greatly improved, and the average weight loss (weight loss calculated as the difference between the mass of the sample before aging and the mass of the sample after aging/the surface area of the sample) is from 0.89mg/cm in the test box test of 2atm, 120 ℃ and 100% relative humidity for 200 hours²Reduced to 0.09mg/cm²。

Table 1 results of performance test of rare earth permanent magnets prepared in inventive example 1 and comparative example 1

Comparative example 2

The alloy components are prepared by a melt spinning (rapid hardening) technology:

Nd_30.5Fe_67.53Ti_0.18Cu_0.17Co_0.5Al_0.1Ga_0.1B_0.92the alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 deg.C under 50kPa argon gas at 1.2m/s speed of copper roller, and hydrogen crushing<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and preparing the molten alloy into fine powder with the average grain diameter of 3.5 microns by a copper roller rotating speed of 1.2m/s and an air flow grinding process (grinding pressure of 0.58MPa and sorting wheel rotating speed of 3800 r/min); and (3) orienting the fine powder in a magnetic field of 1.8T, pressing and molding, isostatic pressing at 200MPa to prepare a green body, then placing the green body in a sintering furnace, preserving heat for 6 hours at 1040 ℃, and then carrying out two-stage aging treatment, wherein the first-stage aging temperature is 900 ℃, the heat preservation time is 3 hours, the second-stage aging temperature is 550 ℃, and the heat preservation time is 6 hours to obtain the rare earth permanent magnet.

The rare earth permanent magnet prepared in comparative example 2 of the present invention was subjected to performance test according to the method of comparative example 1, and the test results are shown in table 2.

Example 2

The alloy components are prepared by a melt spinning (rapid hardening) technology:

Nd_30.5Fe_67.53Ti_0.18Cu_0.17Co_0.5Al_0.1Ga_0.1B_0.92the alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and making the copper roller rotate at 1.2m/s), then adopting hydrogen crushing (580 ℃ after saturated hydrogen absorption for heat preservation and dehydrogenation for 5h) and a gas flow milling process (grinding pressure 0.58MPa, sorting wheel rotation speed 3800r/min) to prepare fine powder with the average grain diameter of 3.5 microns;

the alloy component with the average grain diameter of 100 nm-300 nm is Nd₇₈(TiZr)₉O₁₃Adding oxide nano powder (subscript is mass percentage content) into the fine powder, and uniformly mixing to obtain alloy mixed powder, wherein the mass content of the oxide nano powder in the alloy mixed powder is 0.4%;

the alloy mixed powder is oriented and pressed and formed in a 1.8T magnetic field, a green body is prepared under the pressure isostatic pressing of 200MPa, then the green body is placed in a sintering furnace, the temperature is kept at 1040 ℃ for 6 hours, and then two-stage aging treatment is carried out, wherein the temperature of the first-stage aging treatment is 900 ℃, the temperature is kept for 3 hours, the temperature of the second-stage aging treatment is 550 ℃, and the temperature is kept for 6 hours, so that the high-corrosion-resistance rare earth permanent magnet is obtained.

The performance test of the highly corrosion-resistant rare earth permanent magnet prepared in example 2 of the present invention according to the method of comparative example 1, the test results are shown in table 2, which indicates that the highly corrosion-resistant rare earth permanent magnet prepared in example 2 of the present invention has greatly improved surface corrosion, and the average weight loss is from 1.6mg/cm in the test box test of 2atm, 120 ℃ and 100% relative humidity for 200 hours²Reduced to 0.12mg/cm²。

Table 2 results of performance test of rare earth permanent magnets prepared in inventive example 2 and comparative example 2

Comparative example 3

The alloy components are prepared by a melt spinning (rapid hardening) technology:

Nd₂₈Fe_67.7Tb₂Ti_0.15Cu_0.15Co_0.8Al_0.15Ga_0.15B_0.9the alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and making the copper roller rotate at 1.2m/s), then adopting hydrogen crushing (580 ℃ after saturated hydrogen absorption for heat preservation and dehydrogenation for 5h) and a gas flow milling process (grinding pressure 0.58MPa, sorting wheel rotation speed 3800r/min) to prepare fine powder with the average grain diameter of 3.0 microns;

and (3) orienting the fine powder in a magnetic field of 1.8T, pressing and molding, isostatic pressing at 200MPa to prepare a green body, then placing the green body in a sintering furnace, preserving heat for 6 hours at 1040 ℃, and then carrying out two-stage aging treatment, wherein the first-stage aging temperature is 890 ℃, the heat preservation time is 3 hours, the second-stage aging temperature is 505 ℃, and the heat preservation time is 5.5 hours to obtain the rare earth permanent magnet.

The rare earth permanent magnet prepared in comparative example 3 of the present invention was subjected to property measurement according to the method of comparative example 1, and the measurement results are shown in Table 3.

Example 3

The alloy components are prepared by a melt spinning (rapid hardening) technology:

Nd₂₈Fe_67.7Tb₂Ti_0.15Cu_0.15Co_0.8Al_0.15Ga_0.15B_0.9the alloy raw materials (subscript is mass percentage content) are made into casting sheets (<Smelting at 1450 +/-40 ℃ under the condition of 50kPa argon, and making the copper roller rotate at 1.2m/s), then adopting hydrogen crushing (580 ℃ after saturated hydrogen absorption for heat preservation and dehydrogenation for 5h) and a gas flow milling process (grinding pressure 0.58MPa, sorting wheel rotation speed 3800r/min) to prepare fine powder with the average grain diameter of 3.0 microns;

the alloy component with the average grain diameter of 100 nm-300 nm is Nd₇₈(CuZr)₉O₁₃Adding oxide nano powder (subscript is mass percentage content) into the fine powder, and uniformly mixing to obtain alloy mixed powder, wherein the mass content of the oxide nano powder in the alloy mixed powder is 0.6%;

the alloy mixed powder is oriented and pressed and formed in a 1.8T magnetic field, a green body is prepared under the pressure isostatic pressing of 200MPa, then the green body is placed in a sintering furnace, the temperature is kept at 1040 ℃ for 6 hours, and then two-stage aging treatment is carried out, wherein the first-stage aging temperature is 890 ℃, the temperature is kept for 3 hours, the second-stage aging temperature is 505 ℃, and the temperature is kept for 5.5 hours, so that the high-corrosion-resistance rare earth permanent magnet is obtained.

The performance test of the highly corrosion-resistant rare earth permanent magnet prepared in example 3 of the present invention according to the method of comparative example 1, the test results are shown in table 3, which indicates that the highly corrosion-resistant rare earth permanent magnet prepared in example 3 of the present invention has greatly improved surface corrosion, and the average weight loss is from 1.8mg/cm in the test box test of 2atm, 120 ℃ and 100% relative humidity for 200 hours²Reduced to 0.19mg/cm²。

Table 3 results of performance test of rare earth permanent magnets prepared in inventive example 3 and comparative example 3

From the above embodiments, the invention adds a trace amount of metal oxide nano alloy powder by a unique method, greatly improves the high temperature stability and corrosion resistance of the magnet, and the magnetic performance of the magnet is only slightly reduced; such technical effects have not been achieved in the prior art, and are difficult for one of ordinary skill in the art to easily infer. Based on the foregoing description of the principles and specific embodiments, one skilled in the art can readily modify or design other equivalent embodiments. Those skilled in the art will recognize that such equivalent embodiments are within the scope of the claims herein.

From the above embodiments, it can be known that, a certain amount of nano-scale metal oxide is added to the sintered neodymium iron boron powder, and after being uniformly stirred, the mixture is subjected to orientation compression and sintering to form a high-remanence magnet, most of the sintered oxide is distributed on a triangular grain boundary, so that the potential difference between the grain boundary or the triangular grain boundary and the main phase is reduced, the nano-oxide particles are very small, and can be stably doped in the grain boundary, and the grain boundary phase has better chemical stability. The metal oxide has stable chemical performance, strong operability in process and relatively low cost.

While only the preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.