JP7811287B2 - R-Fe-B based permanent magnet material, manufacturing method and application - Google Patents

Description

Detailed Description of the Invention

This application claims priority from a prior patent application filed by the applicant with the State Intellectual Property Office of the People's Republic of China on May 24, 2022, bearing application number 202210576133.8 and entitled "R-Fe-B-based permanent magnetic material, manufacturing method and application." This prior application is incorporated herein by reference in its entirety.

[Technical Field]
The present invention belongs to the technical field of R-Fe-B based permanent magnetic materials, and in particular to R-Fe-B based permanent magnetic materials, their manufacturing methods, and applications.

[Background technology]
Due to their excellent magnetic properties, sintered R-Fe-B permanent magnets are widely used in power motors, computers, electronic products, etc. As products improve, the requirements for the temperature coefficient of magnets in these fields are increasing. In particular, with the development of related fields such as air conditioners and electric vehicles, there is an increasing demand for NdFeB magnets to be used in a variety of fields, and the requirements for their performance are also becoming increasingly higher.

At the same time, the most obvious drawback of R-Fe-B sintered magnets compared to Sm-Co permanent magnets is their poor corrosion resistance, which limits their application in high-temperature, high-humidity environments. Therefore, research into the corrosion resistance of R-Fe-B sintered magnets is of great significance. In particular, with increasing awareness of environmental protection and energy conservation in countries around the world in recent years, there is an increasing demand for high-performance R-Fe-B sintered magnets with excellent corrosion resistance for permanent magnet motors such as environmentally friendly, energy-saving, and highly efficient wind turbines that are used in humid environments such as seaside areas and grasslands.

However, currently, conventional magnetic material formulations are unable to fully utilize the improved magnetic performance of each element in neodymium-iron-boron magnetic materials, making it impossible to obtain a magnetic material that combines high magnetic performance with relatively good weight loss and mechanical performance.

Summary of the Invention
In order to improve the above-mentioned problems, the present invention provides an R—Fe—B based permanent magnet material,
Br≧13.3 KGs, Hcj≧25.1 Koe,
20 days HAST weight loss ≦3 mg/ ^cm2 ,
The present invention provides an R-Fe-B based permanent magnet material characterized by a bending strength of greater than 440 MPa.

According to an embodiment of the present invention, the permanent magnet material has a 20-day HAST weight loss of ≦1 mg/ ^cm2 .

According to an embodiment of the present invention, the R-Fe-B based permanent magnet material has the following properties: Br is 13.3-15.0 KGs, Hcj is 25-34 Koe, 20-day HAST weight loss is 0.1-0.5 mg/cm ² , and bending strength is 445-470 Mpa.

According to an embodiment of the present invention, the composition of the R-Fe-B-based permanent magnet material contains Ti and Ga, in which the Ti content is ≥ 0.2 wt%, the Ga content is ≥ 0.2 wt%, and the ratio of Ti/Ga is 1 < Ti/Ga < 2.

According to an embodiment of the present invention, the R-Fe-B based permanent magnet material has a composition, in mass percentage 100%, of 26.0 to 32.0% R, 0.3 to 4.0% RH, 0.5 to 3.0% Co, 0.1 to 0.25% Cu, 0.2 to 0.4% Ga, 0.2 to 0.4% Ti, 0 to 0.4% Al, 0.95 to 1.05% B, and the balance being Fe and unavoidable impurities, wherein R is neodymium (Nd) and/or praseodymium (Pr), and RH is dysprosium (Dy) and/or terbium (Tb);
The mass percentage of the above element contents is:
1) 1<Ti/Ga<2,
2) 5≦Co/Cu＜15,
The relationship must be satisfied.

According to an embodiment of the present invention, the R-Fe-B based permanent magnet material includes a grain boundary _phase , and the components of the grain boundary phase include _{RaRHbTicGadCueAlFCOgFeremainder} , where ₃₃ ≦a≦45 _, 0.1≦b≦16, 3≦c≦12 _, 0.4≦d≦2, 0.3≦e≦2.0, 0.01≦f _≦ 0.1 _, 0.4≦g≦16, and a+b+c+d+e+f+g+ _remainder =100;
The mass ratio of _{the remainder} of the R _a RH _b Ti _c Ga _d Cu _e Al _F C _{O g} Fe that occupies the permanent magnet material is 6 to 11 wt %.

According to an embodiment of the present invention, the R is Nd or PrNd, and the R content is preferably 26.5% to 31.0%, preferably 26.5%, 27.0%, 27.5%, 28%, 28.5%, 29.0%, 29.5%, 30.0%, 30.5%, or 31%.

According to an embodiment of the present invention, the RH is at least one of Dy and Tb, and the RH content range is preferably 0.3% to 3.5%, for example, 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, 2.5%, 2.8%, 3.0%, 3.1%, or 3.5%.

According to an embodiment of the present invention, the Co content is 1.0 to 3.0%, and preferably 0.5%, 1%, 1.5%, 2.0%, 2.5%, or 3.0%.

According to an embodiment of the present invention, the Cu content is 0.1 to 0.25%, and preferably 0.1%, 0.12%, 0.15%, 0.17%, 0.18%, 0.2%, 0.23%, or 0.25%.

According to an embodiment of the present invention, the Ga content is 0.2 to 0.4%, and preferably 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

According to an embodiment of the present invention, the Ti content is 0.2 to 0.4%, and preferably 0.2%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, or 0.40%.

According to an embodiment of the present invention, the Al content is 0.05 to 0.35%, and preferably 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or 0.35%.

According to an embodiment of the present invention, the B content is 0.97 to 1.03%, and preferably 0.97%, 0.98%, 0.99%, 1.0%, 1.01%, 1.02%, or 1.03%.

According to an embodiment of the present invention, the unavoidable impurities are, for example, at least one of C, N, O, etc., and preferably, the oxygen content is 300 to 900 ppm, the carbon content is 400 to 800 ppm, and the nitrogen content is 200 to 600 ppm.

The present invention further provides a method for producing a Re-Fe-B based permanent magnetic material, characterized by comprising the steps of smelting and casting, coarsely pulverizing, finely pulverizing, molding, sintering, processing, and diffusing raw materials for the Re-Fe-B based permanent magnetic material to obtain the Re-Fe-B based permanent magnetic material.

According to an embodiment of the present invention, the smelting and casting process is carried out in a medium-frequency vacuum induction rapid solidification melt spinning furnace, with a casting quench roll linear speed of 1 m/s to 2 m/s, a casting temperature of 1380 to 1480°C, and an average flake thickness of 0.20 to 0.30 mm after smelting and casting.

According to an embodiment of the present invention, the coarse grinding process is carried out in a hydrogen grinding furnace through the steps of hydrogen absorption, dehydrogenation, and cooling, with the hydrogen absorption pressure being 90 to 110 KPa, the dehydrogenation temperature being 550 to 620°C, and the dehydrogenation time being 3 to 6 hours.

According to an embodiment of the present invention, the pulverization is performed using an inert gas jet mill, with the inert gas being, for example, nitrogen gas or argon gas. Preferably, the oxygen content during the pulverization process is controlled to ≦50 ppm, and the particle size SMD is 2.3-2.7 μm, preferably 2.5 μm, with X90/X10 ≦4.5 and X100 ≦12.5 μm. In the present invention, when X90/X10 ≦4.5 and X100 ≦12.5 μm are satisfied, higher Br and Hcj are obtained, while the weight loss level and bending strength are also improved.

According to an embodiment of the present invention, an antioxidant can be added during the milling process and mixed for 3 to 6 hours. The mass of the antioxidant is 1 to 2% of the total mass of the permanent magnet material, and the antioxidant is one or more selected from 1,3,5-trichlorotoluene, dibutylhydroxytoluene, and 4-hexylresorcinol. The antioxidant has a lubricating function. The milling process produces fine powder with a uniform particle size distribution, and the use of an inert gas jet mill ensures that the nitrogen content of the powder is relatively low.

According to an embodiment of the present invention, the above molding process is magnetic field-oriented pressing at a pressure of ≥ 1.5 T. During the pressing process, the powder is placed in a completely sealed press and is continuously protected by filling it with nitrogen gas.

According to an embodiment of the present invention, the sintering process involves first subjecting the green compact produced by the compacting process to decarburization and degassing in 2 to 10 temperature zones, followed by vacuum sintering, then sintering in an inert atmosphere, and cooling.

Preferably, the temperatures in the 2 to 10 temperature zones are different from one another, and preferably, the decarburization degassing treatment is performed at an increasing temperature gradient. For example, when the decarburization degassing treatment is performed sequentially in 2 to 10 temperature zones, the decarburization degassing treatment is first performed in the first temperature zone, followed by the next temperature zone, e.g., the second temperature zone, the third temperature zone, or more. For example, the temperature in the first temperature zone may be 200 to 380°C, preferably 280 to 320°C, e.g., 300°C. The temperature in the second temperature zone may be higher than that in the first temperature zone, e.g., 450 to 720°C, preferably 580 to 620°C, e.g., 600°C. The temperature in the third temperature zone may be higher than that in the second temperature zone, e.g., 750 to 1000°C, preferably 880 to 920°C, e.g., 900°C. By adopting the decarburization and degassing process of the present invention, elements such as C, N, and H in the antioxidant can be sequentially desorbed from the permanent magnet material.

Preferably, the vacuum sintering temperature is 1000-1020°C, and the vacuum sintering time is 1-2 hours.

Preferably, the sintering temperature in the inert atmosphere is 1030-1050°C, the sintering time in the inert atmosphere is 2-4 hours, and the pressure when sintering in the inert atmosphere is 10-30 KPa. The inert atmosphere is, for example, nitrogen gas or argon gas.

Preferably, after sintering in an inert atmosphere, a fan at 100 KPa can be used to cool the mixture to below 50°C.

According to an embodiment of the present invention, the sintering process involves placing the green compact produced by the molding process in a sintering furnace under nitrogen gas protection, then passing through a first temperature zone of 200-380°C, a second temperature zone of 450-720°C, and a third temperature zone of 750-1000°C, each undergoing decarburization and gas removal for 1-3 hours, followed by vacuum sintering at 1000-1020°C for 1-2 hours, and then filling with argon gas at 10-30 KPa and performing pressure-holding sintering at 1030-1050°C for 2-4 hours. Argon gas is then filled at approximately 100 KPa, and the blower is started to cool the compact to below 50°C.

By adopting a decarburization/outgassing process, vacuum sintering, and pressure sintering process, the present invention can reduce the content of elements such as C, N, and O in the permanent magnet material to relatively low levels while further increasing the density and bending strength of the permanent magnet material.

According to an embodiment of the present invention, the diffusion treatment is a grain boundary diffusion treatment, and is performed according to a process commonly used in the art, such as Tb or Dy vapor diffusion. The temperature for the diffusion treatment may be 850-950°C, for example 900°C, and the diffusion time may be 10-50 hours, for example 36 hours. After the diffusion treatment, a stress relief aging treatment must be performed, at a temperature of 450-650°C, for example 550°C, for a time of 3-6 hours.

According to an embodiment of the present invention, the Re-Fe-B-based permanent magnet material has an oxygen content of 300 to 900 ppm, a carbon content of 400 to 800 ppm, and a nitrogen content of 200 to 600 ppm.

The present invention further provides for the application of the above-mentioned Re-Fe-B-based permanent magnet material as magnetic steel for motor rotors in motors.

[Beneficial Effects of the Present Invention]
This invention uses precise formulation and process design, and on the premise of strictly controlling elements such as O, C, and N in the permanent magnet material, allows elements such as Ti, Ga, and Cu to be contained in the grain boundary phase of the permanent magnet material, which are beneficial to the Hcj, weight loss performance, and mechanical performance of the permanent magnet material. These elements are uniformly distributed in the grain boundary phase at a certain ratio, which not only refines the crystal grains, increases the wettability and corrosion resistance of the grain boundaries, and prevents abnormal grain growth, but also improves the microstructural structure of the main phase and grain boundary phase of the permanent magnet material by combining optimized jet milling and sintering processes, thereby producing an R-Fe-B system permanent magnet material with excellent comprehensive performance. This Re-Fe-B system permanent magnet material has a 20-day HAST weight loss of ≦3 mg/ ^cm2 , excellent weight loss performance, and bending strength of >440 MPa, with Br≧13.3 kgs and Hcj≧25.1 Koe.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a backscattered scanning electron microscope analysis diagram of the permanent magnet material in Example 1.

[Mode for Carrying Out the Invention]
The technical solutions of the present invention will be described in more detail below with reference to specific examples. It should be understood that the following examples are merely for illustrative purposes and should not be construed as limiting the scope of the claims of the present invention. Any technology realized based on the above content of the present invention is included within the scope of the claims of the present invention.

Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available or may be prepared by known methods.

Examples 1 to 10 and Comparative Examples 1 to 9
The mass percentages of elements in the permanent magnet materials of Examples 1 to 10 and Comparative Examples 1 to 9 are shown in Table 1 below.

The R-Fe-B permanent magnet materials in Examples 1 to 10 and Comparative Examples 1 to 6 were manufactured using the following method.

1) Smelting: The raw materials prepared according to the formulation shown in Table 1 were placed in a crucible and smelted in a medium-frequency vacuum induction rapid solidification melt spinning furnace. The linear speed of the casting and quenching roll was 1.5 m/s, the casting temperature was 1450°C, and the average thickness of the smelted flakes was 0.25 mm.

2) HD processing (coarse crushing)
The material was subjected to hydrogen absorption, dehydrogenation and cooling treatments in a hydrogen pulverization furnace, with the pressure for the hydrogen absorption treatment being 100 KPa, the temperature for the dehydrogenation treatment being 580°C and the dehydrogenation time being 4.5 hours.

3) Jet mill (fine grinding)
By optimizing the jet mill grinding process parameters, the oxygen content during grinding was reduced to 50 ppm or less, and the particle size control SMD was 2.5 μm, with X90/X10 = 4.0 and X100 = 10 μm. To produce the powder, 1.5% of the total mass of the permanent magnet material was added with dibutylhydroxytoluene and mixed for 5 hours.

4) Molding
The 1.8 T magnetic field oriented pressing method is used, and during the pressing process, the powder is in a completely sealed press and is continuously protected by filling it with nitrogen gas.

5) Sintering The green compact was placed in a sintering furnace under nitrogen gas protection, and subjected to decarburization and gas removal treatment at 300°C, 600°C, and 900°C for 2 hours each, followed by vacuum sintering at 1015°C for 1.5 hours. Argon gas was then filled in at 20 KPa, and pressure-hold sintering was performed at 1040°C for 3 hours. Argon gas was then filled in at approximately 100 KPa, and the blower was started to cool the compact to below 50°C.

6) Diffusion The permanent magnet material must be further subjected to grain boundary diffusion treatment, which is carried out according to the Tb vapor diffusion process commonly used in the art, where the diffusion temperature is 900°C and the diffusion time is 30 hours. After the diffusion treatment, stress relief aging treatment can be carried out at a temperature of 550°C for 4 hours to produce the permanent magnet material.

Comparative Example 7
3) Jet mill (fine grinding)
By optimizing the jet milling process parameters, the oxygen content during the milling process was ≦50 ppm, and the particle size control SMD was 2.5 μm, with X90/X10 = 5.0 and X100 = 25 μm. To produce the powder, 1.5% dibutylhydroxytoluene was added and mixed for 5 hours. The remaining blending, smelting, HD, pressing, sintering, and diffusion processes were the same as in Example 1.

Comparative Example 8
5) Sintering First, the green compact was placed in a sintering furnace under nitrogen gas protection, and subjected to decarburization and gas removal treatment at 600°C and 900°C for 2 hours each, followed by vacuum sintering at 1015°C for 1.5 hours. Argon gas was then filled in at 20 KPa, and pressure-hold sintering treatment was performed at 1040°C for 3 hours. Argon gas was then filled in at approximately 100 KPa, and the blower was started to cool the compact to below 50°C.

The remaining processes of compounding, smelting, HD, press molding, sintering, and diffusion are the same as in Example 1.

Comparative Example 9
5) Sintering First, the green compacts were placed in a sintering furnace under nitrogen gas protection, and then decarburized and degassed at 900°C for 2 hours, then vacuum sintered at 1015°C* for 1.5 hours, then filled with argon gas at 20 KPa and sintered at 1040°C for 3 hours. After that, argon gas was filled at approximately 100 KPa, and the blower was started to cool the compacts to below 50°C.

The remaining processes of compounding, smelting, HD, press molding, sintering, and diffusion are the same as in Example 1.

The permanent magnet materials manufactured in Examples 1 to 10 and Comparative Examples 1 to 9 were measured for their magnetic properties, weight loss properties, and bending strength, and the results are shown in Table 2 below.

The remanence (Br), coercive force (Hcj), and magnetic energy product (BH _(max) ) in each of Examples 1 to 10 and Comparative Examples 1 to 9 of the present invention were measured using the NIM-62000 rare earth permanent magnet measurement system from the Institute of Metrology to determine magnetic properties; the weight loss performance was measured using a D10-10 sample column and a German HAST high temperature and humidity tester (130°C, 0.26 atm, 100% RH, 480 h); and the bending strength was measured using a three-point bending device in accordance with the GB/T 14452-93 (three-point bending) standard.

As can be seen from the table above, the present invention precisely designs the formulation to incorporate elements such as Ti, Ga, and Cu into the grain boundary phase of this system's permanent magnet material, which are beneficial to the permanent magnet's Hcj, weight loss, and mechanical properties. These elements are uniformly distributed throughout the grain boundary phase at a certain ratio, reducing grain size, improving grain boundary wettability and corrosion resistance, and preventing abnormal grain growth. Furthermore, the optimized jet milling and sintering processes improve the microstructure of the main phase and grain boundary phase of the permanent magnet material, and rigorously control the O, C, and N contents in the permanent magnet material through strict process design, resulting in an R-Fe-B system permanent magnet material with excellent overall performance. The O, C, and N elements occupy the effective neodymium-rich phase in high-end permanent magnet materials, making the grain boundary phase brittle, which tends to reduce the Hcj and strength of the permanent magnet material. In other words, through precise formulation and process design, the present invention has produced a permanent magnet material with excellent overall performance, including Br≧1.33 T, Hcj≧2000 KA/m, 20-day HAST weight loss≦0.5 mg/cm ² , and bending strength>440 MPa.

Figure 1 shows a backscattered scanning electron microscope analysis of the permanent magnet material in Example 1.

Different regions of the grain boundary phase in Figure 1 were selected and subjected to EDS energy spectrum analysis at 2000x magnification to obtain the content (mass percentage) of each element in the grain boundaries. Based on Figure 1 and the results of the EDS energy spectrum analysis, it was found that the magnet of Example 1 was composed of a _Nd2Fe14B main phase ( _gray region) and a grain boundary phase (silver-white region), with the grain boundary phase being composed _{of Nd33-45Tb0.1-1Ti4-8Ga0.4-1.5Cu0.3-1Al0.01-0.06C00.4-3Fe , the remainder} being _{Fe .} The area of the grain _boundary phase in the different regions was calculated as a percentage of the total area of _the selected microstructure observation region, and the ratio of the area of the grain boundary phase to the total area of the observation region was 6.2-8.9%, indicating that the density of the permanent magnet material was uniform.

In Table 3, the specific detection results for grain boundary phase content are as follows:

The above describes exemplary embodiments of the present invention. However, the scope of the claims of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art that do not deviate from the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

1 is a backscattered scanning electron microscope analysis diagram of the permanent magnet material in Example 1. FIG.

Claims (10)

An R-Fe-B based permanent magnet material, the R-Fe-B based permanent magnet material having a composition, in mass percentage 100%, of 26.0 to 32.0% R, 0.3 to 4.0% RH, 0.5 to 3.0% Co, 0.1 to 0.25% Cu, 0.2 to 0.4% Ga, 0.2 to 0.4% Ti, 0.05 to 0.4% Al, 0.95 to 1.05% B, and the balance being Fe and unavoidable impurities, wherein R is neodymium (Nd) and/or praseodymium (Pr), and RH is dysprosium (Dy) and/or terbium (Tb),
The mass percentage of the content of the elements is:
1) 1<Ti/Ga<2,
2) The relationship 5≦Co/Cu<15 must be satisfied;
Br≧13.3 KGs, Hcj≧25.1 Koe,
20-day HAST weight loss of 0.1-0.5 mg/cm ² ;
It is characterized by having a bending strength of more than 440 MPa.
R-Fe-B permanent magnet material. The R-Fe-B based permanent magnet material is characterized by having the following properties: Br is 13.3 to 15.0 KGs, Hcj is 25 to 34 Koe , and bending strength is 445 to 470 MPa.
The permanent magnet material of claim 1 . The R-Fe-B based permanent magnet material includes a grain boundary phase, and the _composition of the grain boundary phase includes _{RaRHbTicGadCueAlFCOgFeremainder} , where 33≦a≦45, 0.1≦b≦16, 3≦c≦12 _, 0.4≦d≦2 _, 0.3≦e≦2.0, 0.01≦f≦0.1, 0.4≦g≦ ₁₆ , _{and a +} b+c+d+e+f+g+remainder=100 ;
The mass ratio of _{the remainder} of the R _a RH _b Ti _c Ga _d Cu _e Al _F CO _g Fe occupying the permanent magnet material is 6 to 11 wt %.
The permanent magnet material of claim 1 . The inevitable impurities are at least one of C, N, and O, and the oxygen content is 300 to 900 ppm, the carbon content is 400 to 800 ppm, and the nitrogen content is 200 to 600 ppm.
The permanent magnet material of claim 1 . A method for producing a permanent magnet material according to any one of claims 1 to 4, comprising smelting and casting raw materials for a Re-Fe-B based permanent magnet material, coarsely pulverizing, finely pulverizing, molding, sintering, processing, and diffusing the raw materials,
During the fine grinding process, the particle size SMD is 2.3-2.7 μm, X90/X10≦4.5, X100≦12.5 μm;
The sintering process includes the steps of first subjecting a green compact produced by a molding process to decarburization and degassing treatment in 3 to 10 temperature zones, then vacuum sintering, then sintering in an inert atmosphere, and cooling to obtain the Re-Fe-B based permanent magnet material.
Manufacturing method. The coarse pulverization process is carried out in a hydrogen pulverization furnace by the steps of hydrogen absorption, dehydrogenation, and cooling, the pressure of the hydrogen absorption process is 90 to 110 KPa, the temperature of the dehydrogenation process is 550 to 620°C, and the dehydrogenation time is 3 to 6 hours;
The fine pulverization is carried out by an inert gas jet mill, and the inert gas is nitrogen gas or argon gas.
The oxygen content is controlled to ≦50 ppm during the milling process, and the particle size SMD of the particles is 2.5 μm during the milling process.
The method of claim 5. The temperatures of the 3 to 10 temperature zones are different from each other.
The method of claim 6 . When the decarburization and degassing treatment is carried out sequentially in 3 to 10 temperature zones, the decarburization and degassing treatment is first carried out in a first temperature zone, and then the treatment is moved to the next temperature zone in sequence.
The method of claim 7 . The decarburization/degassing treatment is performed in a first temperature zone, followed by a second temperature zone and a third temperature zone, wherein the temperature in the first temperature zone is 200-380°C, the temperature in the second temperature zone is higher than that in the first temperature zone, being 450-720°C, and the temperature in the third temperature zone is higher than that in the second temperature zone, being 750-1000°C.
The method of claim 8. A magnetic material comprising the Re-Fe-B based permanent magnet material according to any one of claims 1 to 4.
Motor rotor magnetic steel.