Patent Application
20230386741
The disclosure relates to the technical field of NdFeB rare earth magnet, in particular to a rare earth magnet that can improve its own coercivity and its manufacturing method thereof.
NdFeB sintered permanent magnets are widely used in electronic equipment, medical equipment, electric vehicles, household products, robots, etc. In the past few decades of development, NdFeB permanent magnets have been rapidly developed, especially diffusion technology can significantly reduce the consumption of heavy rare earths and has a large cost advantage. Adding heavy rare earth elements Dy or Tb to the NdFeB base material is often used in a manufacturing process of a sintered NdFeB permanent magnet, which will make the heavy rare earth elements Dy and Tb into the grain in large quantities and consume a large number of heavy rare earth elements. This way leads to reduction of the residual magnetism and magnetic energy product of the magnet. Another method is grain boundary diffusion, which is a technology that the diffusion source is diffused into the magnet along the grain boundary to improve the coercivity of the magnet. This technology uses fewer heavy rare earths compared to other technologies, attaining the same coercivity of magnets. So it has attracted a lot of attention because of its low cost. However, with the current price of heavy rare earth Dy, Tb raw materials skyrocketing, the cost of grain boundary diffusion technology using pure Dy and Tb is still high. It is well known that the diffusion technology of heavy rare earth alloys can effectively reduce the content of heavy rare earth Dy and Tb to get low-cost magnets. Therefore, the development of diffusion technology of heavy rare earth alloys is particularly important for the mass production of NdFeB magnets.
CN101641750B discloses the following: The powders containing Rh are coated on the NdFeB sintered magnet. The powders containing Rh are diffused into the NdFeB sintered magnet through the grain boundary, wherein Rh is Dy and/or Tb. The powders contains 0.5-50% of Al by weight, and the oxygen contained in the NdFeB sintered magnet is 0.4 by weight % or less. The patent is mainly to mix different powders to prepare a diffusion source, which are diffused into the magnet to increase coercivity of the magnet. Due to the different density of the powder, the mixed diffusion source will appear a certain degree of aggregation, which will cause uneven magnet performance after diffusion. Although the mixed diffusion source contains heavy rare earths, but the coercivity increased are not bigger than the pure heavy rare hearth after diffusion, and the purpose of cost saving cannot be achieved.
CN106298219B discloses the following: a) the diffusion source is RLuRHvFe100-u-v-w-zBwMz rare earth alloy, the RL represents at least one element in Pr and Nd, RH represents at least one element in Dy, Tb, Ho, M represents at least one element in Co, Nb, Cu, Al, Ga, Zr, Ti, u, v, w, z is the weight percentage and 0≤u≤10, 35≤v≤70, 0.5≤w≤5, 0≤z≤5. b) Crush RLuRHvFe100-u-v-w-zBwMz rare earth alloy to form alloy powders. c) The alloy powders are loaded into a rotary diffusion device with an R-T-B magnet for thermal diffusion, with temperature range of 750-950° C. and a time range of 4-72 h. d) Aging treatment. The diffusion source alloy is RLuRHvFe100-u-v-w-zBwMz rare earth alloys. The following issues exist in this technology: Firstly, when the B content in the diffusion source is too high, its melting point will be relatively high and it is not easy to diffuse into the magnet. Secondly, according to the diffusion source formula, it can be known that the Fe content in the diffusion is ≥10%. When the iron content is too high in the magnet too many ferromagnetic phases are formed, and the performance of the NdFeB magnet is reduced including the Hcj and Br of the magnet.
CN113593800A discloses the following: the diffusion source is RHxM1Bz, the RH is selected from one or two elements in Dy, Tb, M1 is selected from one, two or three elements of Ti, Zr, Al elements, B is boron element, x, y, z represents the weight percentage of the element, x, y, z satisfies the following relationship: 75%≤x≤90%, 0.1%≤z≤0.5%, y=1-x-z. On the one hand, the method improves the Hcj of the sintered NdFeB magnet by diffusion in the detachable material reaction barrel. The method solves the problem of efficiency improvement in the diffusion process, the problem of appearance adhesion. The coercivity is slightly improved, but the long-term use of the diffusion source will inevitably cause certain oxidation and nitridation, but cause further reduction in the utilization rate of heavy rare earths and increase in cost. On the other hand, when the diffusion source contains Ti or Zr, its melting point will be relatively high, resulting in a low diffusion rate. When consuming the same heavy rare earth content, the residual magnetism drops more, the coercivity of the magnet is not further improved. The three-stage temperature rise and fall heat treatment method used is a conventional production process. Based on the above technical analysis, the diffusion source of heavy rare earth alloy encounters the following two problems: on the one hand, the melting point of the diffusion source is too high, resulting in low diffusion rate and the improvement of coercivity is limited; On the other hand, during the diffusion process, the residual magnetism of the magnet with high heavy rare earth content or high Fe content decreases more, resulting in the inability to greatly improve the performance of the magnet.
Object of the disclosure: In order to overcome the shortcomings in the prior art, the present disclosure provides NdFeB rare earth magnet and manufacturing method thereof.
Technical solution: In order to achieve the above object, the present disclosure provides an NdFeB rare earth magnet, the NdFeB magnet comprises a main phase, a heavy rare earth shells, a grain boundary phase and a rare earth-rich phase, wherein the grain boundary phase comprises a μ phase and a δ phase, the μ phase is R36.5Fe63.5-xMx, 2.5≤x≤5, and the δ phase is R32.5Fe67.5-yMy, 7≤y≤25, wherein R refers to at least two elements selected from Nd, Pr, Ce and La, and M refers to at least two elements selected from Al, Cu and Ga; the proportions are given in atomic percentages.
A method for preparing NdFeB rare earth magnet described comprising the following steps,
Preferably, in step (S1) and step (S3), the method of coating is a spray coating, dip coating or screen printing coating.
Preferably, in step (S1), the aging treatment temperature is 600-800° C.; the hydrogen absorption temperature of the diffusion source is 50-200° C., and the dehydrogenation temperature is 450-550° C.
Preferably, in step (S1), powder particle size of the diffusion source is 3-60 μm.
Preferably, in step (S2), the NdFeB magnet base material is melted and quick-coagulated to obtain the NdFeB sheet.
Preferably, in step (S2), mixing an NdFeB magnet base material sheet and lubricant, then taking a hydrogen treatment and airflow grinding to obtain mixed powder; the above powder is pressed, formed, and sintered to obtain the NdFeB magnet base material.
Preferably, powder particle size of the airflow grinding is 2-5 μm.
Preferably, the temperature of sintering process for preparing the NdFeB magnet base material is 980-1060° C., sintering time is 6-15 h.
Preferably, in step (S3), diffusion temperature is 850-950° C., diffusion time is 6-30 h, and first-stage aging temperature is 700-850° C., first-level aging time is 2-10 h, second-level aging temperature is 450-600° C., and second-level aging time is 3-10 h.
NdFeB rare earth magnet and manufacturing method thereof of the present disclosure has at least the following technical effects:
The principles and features are described in the present disclosure, and the examples given are only used to explain the present disclosure and are not intended to limit the scope of the present disclosure.
General Concept
There is provided a method of preparing NdFeB rare earth magnet, including the following steps:
In order to verify the present scheme, eighteen pairs of examples and comparative examples are designed and the difference between the comparative examples and the examples is as follows: The diffusion source of the comparative examples have no the components of B or Fe. The composition and process conditions of the comparative examples are shown in Table 4. The diffusion source is put into vacuum melting furnace for melting, pouring to form a thin sheet, cooled at 50° C. and discharged, the average thickness of the sheet is 0.25 mm, The content of C or O is ≤200 ppm, the N content 50 ppm.
Based on the above data, the NdFeB earth magnet is obtained by diffusion source alloy RαRHδMβBγFe100-α-β-γ-δ. All examples in which the performance NdFeB by diffusion source containing Dy have ΔHcj of more than 636.8 kA/m and containing Tb have ΔHcj of more than 875.6 kA/m, containing DyTb have ΔHcj of more than 716.4 kA/m. The residual magnetic reduction of the embodiment was significantly lower than the proportion, and the coercivity of the embodiment was higher than the comparative example therefore, the examples and comparative examples are specifically analyzed as follows:
The foregoing is only a better Example of the present disclosure and is not intended to limit the present disclosure, where any modification, equivalent substitution, improvement etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210609436.5 | May 2022 | CN | national |
