A high magnetic corrosion-resistant sintered cerium-rich permanent magnet and preparation method thereof

Abstract

The invention provides a high-magnetism corrosion-resistant sintered cerium-rich permanent magnet and a preparation method thereof, belonging to the technical field of permanent magnet materials. Based on the influence of titanium copper (Ti, Cu) on the metallurgical physical properties of a cerium-rich RE-Fe-B system and the size of the main phase of the alloy solidification state and the passivation effect on the rare earth-rich phase, considering the close relationship between the grain boundary phase morphology and the magnet tempering process, temperature and other factors, combined with the synergistic effect of titanium copper and heat treatment and the adsorption characteristics of its ultrafine powder on the magnet surface, a high-magnetism corrosion-resistant sintered cerium-rich permanent magnet and a preparation method thereof are provided. The high-magnetism corrosion-resistant sintered cerium-rich permanent magnet prepared by the invention has clear grain boundaries, and compared with the existing commonly used sintered cerium-rich permanent magnets, the microstructure is more optimized, the coercive force and comprehensive magnetic properties are higher, and the material cost is lower. At the same time, chemically stable titanium copper is used for grain boundary passivation, so that the corrosion resistance of the magnet is improved, and the corrosion-resistant magnet is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of permanent magnetic materials, and in particular relates to a high-magnetism corrosion-resistant sintered cerium-rich permanent magnet and a preparation method thereof. Background Art

[0002] Sintered cerium-rich permanent magnets are rare earth permanent magnet materials with cerium (Ce) content accounting for 10%-50% of the total rare earth (RE) content. They are widely used in electroacoustics, magnetic separators, nuclear magnetic resonance, industrial motors, mobile smart terminals and other fields. Ce in the magnet is a high-abundance rare earth raw material, with a much larger reserve in the earth's crust than rare earth elements such as Nd, Pr, Dy, and Tb, and is inexpensive. Its use greatly reduces the production cost of rare earth permanent magnets, giving it an outstanding cost advantage. Cerium-rich permanent magnets are commonly prepared by sintering methods;

[0003] RE2Fe in sintered cerium-rich permanent magnets 14 B phase and Ce-rich rare earth grain boundary phase coexist; among them, RE2Fe 14 B phase is the main phase, and its anisotropy is the source of the material's hard magnetism; the size of the main phase and the composition, morphology, and distribution of the grain boundary phase affect the magnetic parameters and corrosion resistance; it should be pointed out that Ce2Fe 17 , CeFe2 soft magnetic phase, which is not conducive to the permanent magnetism of the material; the active properties of the rich (RE, Ce) grain boundary phase will lead to the deterioration of the intrinsic corrosion resistance of the magnet; therefore, in order to improve the quality of cerium-rich permanent magnets, it is necessary to reduce or eliminate the appearance of soft magnetic phases in the grain boundary region of the magnet, enhance the stability of the Ce-rich rare earth phase and improve its distribution along the grain; in other words, regulating the microstructure of sintered magnets is an important strategy for preparing high-magnetic and corrosion-resistant sintered cerium-rich permanent magnet materials; the magnet microstructure includes the main phase grain size, grain boundary phase morphology, etc., which are related to the magnet sintering, heat treatment process and parameters, and are affected by the physicochemical properties of the magnet alloy elements and the method of incorporation; for example, Me (Me = Al, Ga, Cu, Sn, Zr, Nb, etc.) elements can optimize the grain boundary phase distribution or hinder the growth of the main phase, thereby improving the coercive force of the magnet, but Me reduces the magnetic energy product of the material due to magnetic dilution. This harmful effect can be alleviated when Me is doped into the grain boundary. It can be seen that it is more desirable to improve the microstructure of the magnet by doping alloy elements at the grain boundary. Studies have shown that the effects of alloy elements and heat treatment on the microstructure of the magnet are interrelated, but it is difficult to eliminate Ce2Fe with commonly used alloy elements. 17 , CeFe2 soft magnetic phase, and their addition amount is too small to improve the intrinsic corrosion resistance of the magnet significantly; this situation is becoming a factor restricting the development of the field of rare earth permanent magnet materials as the society has a strong demand for sintered cerium-rich permanent magnets; therefore, it is of great significance to develop a high magnetic and corrosion-resistant sintered cerium-rich permanent magnet. Summary of the invention

[0004] The present invention aims at the difficulty of eliminating Ce2Fe2O3 alloy elements commonly used in the prior art. 17 , CeFe2 soft magnetic phase, there is also a problem that the doping amount is too small and the intrinsic corrosion resistance of the magnet is not significantly improved. This problem is increasingly becoming an important factor restricting the development of the field of rare earth permanent magnet materials as the society has a strong demand for sintered cerium-rich permanent magnets; a high magnetic and corrosion-resistant sintered cerium-rich permanent magnet and a preparation method thereof, through the influence of titanium copper (Ti, Cu) on the metallurgical physical properties of the cerium-rich RE-Fe-B system and the size of the main phase of the alloy solidification state and the passivation effect on the rare earth-rich phase, taking into account the close relationship between the grain boundary phase morphology and the magnet tempering process, temperature and other factors, and combining the synergistic effect of titanium copper and heat treatment and the adsorption characteristics of its ultrafine powder on the magnet surface.

[0005] In order to achieve the above purpose, the technical solution adopted in this application is:

[0006] A high-magnetic, corrosion-resistant, sintered cerium-rich permanent magnet, the composition of which is: (REx(Ga, Al, Zn, Zr, Co)yFe100-xyz-Bz)100-v(TiuCu100-u)v. Wherein, RE is a rare earth element for magnet, including the required element Ce and one or more of the optional elements Nd, Pr, La, Sm, and Ho, and Ce / RE ≥ 10 %; x, y, and z represent the mass proportions of RE, (Ga, Cu, Zr, Co), and B elements in the REx(Ga, Cu, Zr, Co)yFe100-xy-zBz alloy, respectively, u represents the mass proportion in the TiuCu100-u alloy, and v represents the mass proportion of TiuCu100-u in the entire material composition system; the value ranges of x, y, z, and u in the material composition system are as follows: 28.5 wt.% ≤ x ≤ 33.5 wt.%, 0.5 wt.% ≤ y≤ 4.5 wt.%, 0.85 wt.% ≤ z ≤ 1.05 wt.%, 15.0 wt.% ≤ u ≤ 85.0 wt.%, 0.05 wt.%≤ v ≤ 3.05 wt.%.

[0007] A method for preparing a high-magnetic, corrosion-resistant, sintered cerium-rich permanent magnet, the specific steps are as follows:

[0008] Step 1: Prepare the main alloy RE according to the composition ratio x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z The main alloy is firstly made into a rapid solidification thin strip by melting-rapid solidification strip throwing process, and then hydrogen explosion and rough crushing are carried out; then the rough crushed RE x (Ga,Al,Zn,Zr,Co)y Fe 100-x-y-z -B z The alloy chips are jet-milled to prepare the main alloy powder;

[0009] Step 2: Prepare Ti according to the composition ratio u Cu 100-u Auxiliary alloy for grain boundary doping; the auxiliary alloy is first prepared by vacuum melting to form Ti u Cu 100-u Casting ingots, crushing them with jaws and then ball milling them to obtain auxiliary alloy powder;

[0010] Step 3: Mix the main alloy powder RE in the mixer x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z And auxiliary alloy powder Ti u Cu 100-u Mixed, Ti u Cu 100-u The proportion in the whole alloy system is 0.05 wt.%-3.05 wt.%; gasoline is added during mixing and under the condition of argon protection, a mixture with uniform dispersion of auxiliary alloy powder is obtained;

[0011] Step 4: Orient the mixture obtained in step 3 in a magnetic field of 1.5 T to 2.5 T to obtain a compact; then use a hydraulic press to isostatically press the compact to prepare a compact with uniform stress distribution;

[0012] Step 5: Sintering the magnet compact in a vacuum environment to obtain a sintered NdFeB magnet;

[0013] Step six: perform three-stage tempering heat treatment on the prepared sintered magnet: first, place the sintered magnet in a vacuum heat treatment chamber for primary tempering. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. Then, perform secondary tempering in the vacuum heat treatment chamber. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. Then, perform three-stage tempering in the vacuum heat treatment chamber. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. After three-stage tempering, a high-magnetism, corrosion-resistant, sintered cerium-rich permanent magnet is prepared.

[0014] Preferably, in step one, the average particle size of the main alloy powder is 1.5 μm-4.5 μm; in step two, the average particle size of the auxiliary alloy powder is 0.5 μm-2.5 μm.

[0015] Preferably, in step three, the amount of gasoline added is 0.15 wt.%-0.55 wt.% of the entire alloy system.

[0016] Preferably, in step 4, the magnetic field molding pressure used is in the range of 100 MPa-200 MPa; the hydraulic press pressure used is in the range of 150 MPa-300 MPa.

[0017] Preferably, in step five, the sintering temperature is 1040°C-1090°C, and the sintering time is 2.5 h-4.5 h.

[0018] Preferably, in step six, the primary tempering temperature range is 830°C-900°C, and the primary tempering time is 1.5 h-3.5 h; the secondary tempering temperature range is 600°C-800°C, and the secondary tempering time is 1.5 h-3.5 h; the tertiary tempering temperature range is 450°C-750°C, and the tertiary tempering time is 1.5 h-3.5 h.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are:

[0020] The present invention is based on the influence of titanium copper (Ti, Cu) on the metallurgical physical properties of the cerium-rich RE-Fe-B system and the size of the main phase of the alloy in the solidified state and the passivation effect on the rare earth-rich phase, taking into account the close relationship between the grain boundary phase morphology and the magnet tempering process, temperature and other factors, combined with the synergistic effect of titanium copper and heat treatment and the adsorption characteristics of its ultrafine powder on the magnet surface, a high-magnetic corrosion-resistant sintered cerium-rich permanent magnet and a preparation method thereof are proposed; the high-magnetic corrosion-resistant sintered cerium-rich permanent magnet prepared by the present invention has clear grain boundaries, and compared with the existing commonly used sintered cerium-rich permanent magnets, the microstructure is more optimized, the coercive force and comprehensive magnetic properties are higher, and the material cost is lower; at the same time, chemically stable titanium copper is used for grain boundary passivation, the corrosion resistance of the magnet is improved, and a corrosion-resistant magnet is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 This is a microstructure diagram of the high magnetic corrosion-resistant sintered cerium-rich permanent magnet of Example 1 of the present invention;

[0023] Figure 2 This is the demagnetization curve of the high magnetic and corrosion-resistant sintered cerium-rich permanent magnet of Example 1. DETAILED DESCRIPTION

[0024] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0026] Embodiment 1, as Figure 1 , Figure 2 As shown,

[0027] The present invention discloses a high magnetic corrosion-resistant sintered cerium-rich permanent magnet, wherein the high magnetic corrosion-resistant sintered cerium-rich permanent magnet comprises: (RE x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z ) 100-v (Ti u Cu 100-u ) v Among them, RE is a rare earth element for magnets, including the required element Ce and one or more of the optional elements Nd, Pr, La, Sm, and Ho, and Ce / RE ≥ 10%; x, y, and z represent the RE, (Ga, Cu, Zr, Co), and B elements in RE respectively. x (Ga,Cu,Zr,Co) y Fe 100-x-y-z B z The mass ratio in the alloy, u represents Ti u Cu 100-u The mass ratio in the alloy, v represents Ti u Cu 100-u The mass proportion in the entire material composition system; the value ranges of x, y, z and u in the material composition system are as follows: 28.5 wt.% ≤ x ≤ 33.5 wt.%, 0.5 wt.% ≤ y ≤4.5 wt.%, 0.85 wt.% ≤ z ≤ 1.05 wt.%, 15.0 wt.% ≤ u ≤ 85.0 wt.%, 0.05 wt.% ≤v ≤ 3.05 wt.%.

[0028] The present invention discloses a method for preparing a highly magnetic, corrosion-resistant, sintered cerium-rich permanent magnet, characterized in that the specific steps are as follows:

[0029] Step 1: Prepare the main alloy RE according to the composition ratio x (Ga,Al,Zn,Zr,Co)y Fe 100-x-y-z -B z The main alloy is firstly made into a rapid solidification thin strip by melting-rapid solidification strip throwing process, and then hydrogen explosion and rough crushing are carried out; then the rough crushed RE x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z The alloy chips are jet-milled to prepare the main alloy powder;

[0030] Step 2: Prepare Ti according to the composition ratio u Cu 100-u Auxiliary alloy for grain boundary doping; the auxiliary alloy is first prepared by vacuum melting to form Ti u Cu 100-u Casting ingots, crushing them with jaws and then ball milling them to obtain auxiliary alloy powder;

[0031] The average particle size of the main alloy powder obtained in step 1 is controlled between 1.5 μm and 4.5 μm; the average particle size of the auxiliary alloy powder obtained in step 2 is controlled between 0.5 μm and 2.5 μm;

[0032] Step 3: Mix the main alloy powder RE in the mixer x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z And auxiliary alloy powder Ti 60 Cu 40 Mixed, Ti 60 Cu 40 The proportion of the auxiliary alloy powder in the whole alloy system is 0.3 wt.%; gasoline is added during mixing, and the amount of gasoline added is 0.25 wt.%; and under the condition of argon protection, a mixture with uniform dispersion of auxiliary alloy powder is obtained;

[0033] Step 4: Orient the mixture obtained in step 3 in a magnetic field of 1.5 T-2.5 T, and control the molding pressure range to be 100 MPa-200 MPa to obtain a compact; then, use a hydraulic press to isostatically press the compact, and the hydraulic press pressure is 220 MPa to prepare a compact with uniform stress distribution;

[0034] Step 5: Sintering the magnet compact under vacuum at a sintering temperature of 1060 °C for 3 h to obtain a sintered NdFeB magnet;

[0035] Step six: perform three-stage tempering heat treatment on the prepared sintered magnet: first, place the sintered magnet in a vacuum heat treatment for primary tempering, the primary tempering temperature is 850 ℃, and the primary tempering time is 2 h; after heating, introduce argon into the furnace to quickly cool the magnet to room temperature; then perform secondary tempering in the vacuum heat treatment, the secondary tempering temperature is 750 ℃, and the secondary tempering time is 2 h; after heating, introduce argon into the furnace to quickly cool the magnet to room temperature; then perform three-stage tempering in the vacuum heat treatment, the third-stage tempering temperature is 650 ℃, and the third-stage tempering time is 2 h; after heating, introduce argon into the furnace to quickly cool the magnet to room temperature. After the three-stage tempering, a high magnetic and corrosion-resistant sintered cerium-rich permanent magnet is prepared.

[0036] The prepared corrosion-resistant cerium-rich NdFeB permanent magnet was placed in an open-circuit PFM permanent magnet material measurement system, and the magnetic properties were measured as follows: r =13.8 kG, H cj =15 kOe, (BH) max =45 MGOe.

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet, characterized in that: The composition of the high magnetic corrosion-resistant sintered cerium-rich permanent magnet is: (RE x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z ) 100-v (Ti u Cu 100-u ) v ; RE is a rare earth element for magnets, including the required element Ce and one or more of the optional elements Nd, Pr, La, Sm, and Ho, and Ce / RE ≥ 10%; x, y, and z represent the RE, (Ga, Cu, Zr, Co), and B elements in RE respectively. x (Ga,Cu,Zr,Co) y Fe 100-x-y-z B z The mass ratio in the alloy, u represents Ti u Cu 100-u The mass ratio in the alloy, v represents Ti u Cu 100-u The mass proportion in the entire material composition system; the value ranges of x, y, z and u in the material composition system are as follows: 28.5 wt.%≤ x ≤ 33.5 wt.%, 0.5 wt.% ≤ y ≤ 4.5 wt.%, 0.85 wt.% ≤ z ≤ 1.05 wt.%, 15.0wt.% ≤ u ≤ 85.0 wt.%, 0.05 wt.% ≤ v ≤ 3.05 wt.%; The specific steps of the preparation method are as follows: Step 1: Prepare the main alloy RE according to the composition ratio x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z The main alloy is firstly made into a rapid solidification thin strip by melting-rapid solidification strip throwing process, and then hydrogen explosion and rough crushing are carried out; then the rough crushed RE x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z The alloy chips are jet-milled to prepare the main alloy powder; Step 2: Prepare Ti according to the composition ratio u Cu 100-u Auxiliary alloy for grain boundary doping; the auxiliary alloy is first prepared by vacuum melting to form Ti u Cu 100-u Casting ingots, crushing them with jaws and then ball milling them to obtain auxiliary alloy powder; Step 3: Mix the main alloy powder RE in the mixer x (Ga,Al,Zn,Zr,Co) y Fe 100-x-y-z -B z And auxiliary alloy powder Ti u Cu 100-u Mixed, Ti u Cu 100-u The proportion in the whole alloy system is 0.05 wt.%-3.05 wt.%; gasoline is added during mixing and under the condition of argon protection, a mixture with uniform dispersion of auxiliary alloy powder is obtained; Step 4: Orient the mixture obtained in step 3 in a magnetic field of 1.5 T to 2.5 T to obtain a compact; then use a hydraulic press to isostatically press the compact to prepare a compact with uniform stress distribution; Step 5: Sintering the magnet compact in a vacuum environment to obtain a sintered NdFeB magnet; Among them, the sintering temperature is 1040 ℃-1090 ℃; Step six: perform three-stage tempering heat treatment on the prepared sintered magnet: first, place the sintered magnet in a vacuum heat treatment chamber for primary tempering. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. Then, perform secondary tempering in the vacuum heat treatment chamber. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. Then, perform three-stage tempering in the vacuum heat treatment chamber. After heating, introduce argon into the furnace to quickly cool the magnet to room temperature. After three-stage tempering, a high-magnetism, corrosion-resistant, sintered cerium-rich permanent magnet is prepared.

2. The method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet according to claim 1, characterized in that: In step 1, the average particle size of the main alloy powder is 1.5 μm-4.5 μm; in step 2, the average particle size of the auxiliary alloy powder is 0.5 μm-2.5 μm.

3. The method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet according to claim 1, characterized in that: In step 3, the amount of gasoline added is 0.15 wt.%-0.55 wt.% of the entire alloy system.

4. The method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet according to claim 1, characterized in that: In step 4, the magnetic field molding pressure used ranges from 100 MPa to 200 MPa; the hydraulic press pressure used ranges from 150 MPa to 300 MPa.

5. The method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet according to claim 1, characterized in that: In step five, the sintering time is 2.5 h-4.5 h.

6. The method for preparing a high magnetic corrosion-resistant sintered cerium-rich permanent magnet according to claim 1, characterized in that: In step six, the primary tempering temperature range is 830°C-900°C, and the primary tempering time is 1.5 h-3.5 h; the secondary tempering temperature range is 600°C-800°C, and the secondary tempering time is 1.5 h-3.5 h; the tertiary tempering temperature range is 450°C-750°C, and the tertiary tempering time is 1.5 h-3.5 h.

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