Method for predicting room-temperature magnetic performance of neodymium-iron-boron permanent magnet

Abstract

The invention discloses a method for predicting the room-temperature magnetic performance of a neodymium iron boron permanent magnet, which is a prediction method based on practice and theoretical analysis, the prediction method deforms an existing residual magnetism and coercive force theoretical formula, and the form is changed into a form containing phase composition parameters based on actual deformation from a theoretical aesthetic form. According to the prediction method, a residual magnetism and coercive force calculation model is established by calculating the proportion of the main phase (NdFeB) to the non-magnetic phase (Non-magnetic Phase), simple, efficient and accurate prediction of the room-temperature magnetic performance of the neodymium-iron-boron permanent magnet is achieved, the non-magnetic phase composition and components which cannot be quantitatively analyzed can be bypassed, and the prediction accuracy of the room-temperature magnetic performance of the neodymium-iron-boron permanent magnet is improved. The influence of the components of the neodymium-iron-boron permanent magnet on the performance is simply and clearly displayed and calculated from a more macroscopic perspective, and a universal and quantitative rapid solution can be provided for component design and process design of various neodymium-iron-boron permanent magnets.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of NdFeB permanent magnets, and particularly relates to a method for predicting the room-temperature magnetic performance of a NdFeB permanent magnet. BACKGROUND

[0002] The room-temperature magnetic performance, such as the residual magnetization (referred to as remanence) and the intrinsic coercivity (referred to as coercivity), of a NdFeB permanent magnet is highly dependent on its composition design. However, due to the complex processing system and the variety of composition components of a NdFeB permanent magnet, the mapping relationship from the composition design to the actual magnetic performance currently mainly relies on the accumulation of practical experience, and lacks a simple, systematic and highly accurate prediction method.

[0003] In theory, the phase composition of a NdFeB permanent magnet can be calculated based on the composition of the NdFeB permanent magnet. Specifically, the microstructure of a NdFeB permanent magnet is mainly determined by the following two types of phases:

[0004] 1) main phase: the main phase is a NdFeB phase, which is the main source of magnetism of the magnet and affects the remanence level, and the remanence represents the strength of magnetism;

[0005] 2) non-magnetic phase: the non-magnetic phase is a phase other than the main phase, which is composed of a variety of non-magnetic components and affects the coercivity level, and the coercivity represents the anti-demagnetization ability.

[0006] However, the composition of the non-magnetic phase is extremely complex, usually including a series of phases such as the metal Nd phase, various Nd oxide phases, Nd carbide phases, Nd amorphous phases, NdFeGa phases, and NdCu phases. Due to the multiple and complex actual composition of the non-magnetic phase, it is difficult to accurately analyze its composition quantitatively through equilibrium phase diagram analysis / theoretical calculation, which makes it extremely challenging to determine the composition of the non-magnetic phase and the overall magnetic performance of a NdFeB permanent magnet based on the composition of the NdFeB permanent magnet.

[0007] Currently, the composition optimization of a NdFeB permanent magnet still highly depends on experimental trial and error and experience accumulation, and lacks an efficient and reliable theoretical prediction method. Therefore, developing a prediction method that can systematically and accurately correlate the composition design and the magnetic performance is of great significance for improving the design and development efficiency of a NdFeB permanent magnet. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a simple, efficient and accurate prediction method for the room temperature magnetic performance of a neodymium iron boron permanent magnet, which can bypass the non-magnetic phase composition and its components that cannot be quantitatively analyzed, and from a more macroscopic perspective, simply and clearly show and calculate the influence of the components of the neodymium iron boron permanent magnet on the performance, so as to provide a universal and quantitative rapid solution for the component design and process design of various neodymium iron boron permanent magnets.

[0009] The technical scheme adopted by the present application to solve the above technical problem is: a prediction method for the room temperature magnetic performance of a neodymium iron boron permanent magnet, comprising the following steps:

[0010] S1, establishing a residual magnetism calculation model:

[0011] Jr=A×J S [1-ω(Non-magnetic Phase)] (1)

[0012] wherein, Jr represents the residual magnetism of the neodymium iron boron permanent magnet, A represents a process constant in the production process of the neodymium iron boron permanent magnet, J S represents the saturation magnetic polarization intensity of the main phase in the neodymium iron boron permanent magnet determined based on the component calculation, J S , the unit of which is kGs, kGs is a commonly used unit for representing the magnetic polarization intensity or residual magnetism value of the neodymium iron boron permanent magnet in the Gaussian system, and ω(Non-magnetic Phase) represents the mass fraction of the non-magnetic phase in the neodymium iron boron permanent magnet;

[0013] J S The calculation formula of J

[0014]

[0015] wherein, ω(Nd), ω(Pr), ω(Ce), ω(Gd), ω(Tb), ω(Dy), ω(Ho), ω(Fe), ω(Co), and ω(Al) respectively represent the mass fractions of the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho, Fe, Co, and Al in the formula design of the neodymium iron boron permanent magnet;

[0016] S2, establishing a coercive force calculation model:

[0017] Hcj=B×H A -J S ×[C0+C1ω(Non-magnetic Phase)] (2)

[0018] Hcj= A * B * H + C0+ C1* ω(Non-magnetic Phase) (1) wherein, Hcj represents the coercivity of the Nd-Fe-B permanent magnet; B represents the magnetic crystal anisotropy field coefficient determined by the microstructure of the Nd-Fe-B permanent magnet, in the Nd-Fe-B permanent magnet, the coercivity is derived from the resistance of the magnetic crystal anisotropy field in the Nd-Fe-B lattice to the rotation of the atomic magnetic moment from the original magnetization direction, the magnetic crystal anisotropy field in the lattice depends on the rare earth composition design, the actual demagnetization process usually originates from the surface of the micrograin, due to the existence of more defects on the surface, the actual magnetic crystal anisotropy field capacity is lower than 100%, in the model (2), the process is described by the coefficient B, and the micro-disperse magnetic field derived from J S is the main reason why the coercivity of the Nd-Fe-B permanent magnet is lower than the magnetic crystal anisotropy field design; H A represents the magnetic crystal anisotropy field determined by the rare earth element in the Nd-Fe-B permanent magnet, H A is expressed by kOe, kOe is a commonly used unit for expressing the magnetic field strength or coercivity value of the Nd-Fe-B permanent magnet in the Gaussian system; C0 represents the micro-disperse magnetic field coefficient separated from the phase composition of the Nd-Fe-B permanent magnet, which is only related to the production process of the Nd-Fe-B permanent magnet, C1 represents the micro-disperse magnetic field coefficient related to the mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet, and C0+C1ω(Non-magnetic Phase) constitutes the complete micro-disperse magnetic field coefficient;

[0019] The calculation formula of H A is:

[0020]

[0021] S3, based on the statistical analysis of the literature and production practice data, it is determined that A = 0.985, B = 0.65, C0 = 2.4233, C1 = -4.2798;

[0022] The definition parameter T satisfies:

[0023] T = ω(Fe) + ω(Co) - 1.9ω(Ga)

[0024] Wherein, ω(Ga) represents the mass fraction of element Ga in the formula design of the Nd-Fe-B permanent magnet;

[0025] The mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet satisfies:

[0026] ω(Non-magnetic Phase) = 1 - (0.0160 * T - 0.1650)

[0027] The values of A, J S , ω(Non-magnetic Phase) are substituted into the model (1) to obtain the predicted value of the residual magnetization Jr of the Nd-Fe-B permanent magnet; B, H A , J S, C0, C1, ω (Non-magnetic Phase) into the model (2), to obtain the predicted value of the coercivity Hcj of the Nd-Fe-B permanent magnet.

[0028] As preferred, the process of establishing the model (1) is:

[0029] The theoretical formula of the remanence of the Nd-Fe-B permanent magnet is:

[0030]

[0031] Wherein, A0 represents the volume fraction of the positive domain in the Nd-Fe-B permanent magnet, and the actual Nd-Fe-B permanent magnet can be regarded as being composed of a plurality of small magnetic domains, wherein the magnetic domains with the same direction as the magnetization direction are referred to as positive domains, and the magnetic domains with the opposite direction to the magnetization direction are referred to as negative domains, and only the positive domains contribute to the magnetic intensity; β is ω (Non-magnetic Phase) in the model (1) and the model (2), d 磁体 represents the actual density of the Nd-Fe-B permanent magnet, d 理论 represents the theoretical density of the Nd-Fe-B permanent magnet; represents the influence of the compactness of the Nd-Fe-B permanent magnet after sintering on the remanence, The value of 100% represents that the Nd-Fe-B permanent magnet is completely compact inside, and the actual The value of β is slightly lower than 100%; θ represents the grain orientation degree, and the value of θ reflects the angle difference between the actual magnetization direction of the micro-grains inside the Nd-Fe-B permanent magnet and the macroscopic designed magnetization direction, and the values of θ at different positions inside the Nd-Fe-B permanent magnet are slightly different, and the overall comprehensive contribution is determined by the cosine value of the average value of the volume ;

[0032] Since in the actual production of the Nd-Fe-B permanent magnet, the parameters A0, θ depend on the production process and are almost irrelevant to the composition, therefore, A0, and θ are comprehensively formed into the process constant A of the Nd-Fe-B permanent magnet production process, to obtain the model (1).

[0033] As preferred, the process of establishing the model (2) is:

[0034] The theoretical formula of the coercivity of the Nd-Fe-B permanent magnet is:

[0035]

[0036] Wherein, K1 represents the magnetic crystal anisotropy energy, μ0 represents the vacuum permeability, μ0 = 4π × 10 -7 H / m, M S is J S in the model (1) and the model (2), denotes the value of the magnetic crystal anisotropy energy equivalent to the magnetic field strength, H A , ex , H K1 denotes the exchange coupling, the degree of grain orientation, the microstructure coefficient corresponding to the K1 loss caused by surface defects, respectively, eff denotes the demagnetization field factor, N eff The value of depends on the phase structure, grain size, and grain shape.

[0037] In the actual production of neodymium iron boron permanent magnets, the parameter ex , H K1 depends on the production process, therefore, the ex , H K1 is integrated into the microstructure of neodymium iron boron permanent magnet to determine the magnetic crystal anisotropy field coefficient B, and N eff is further split into the microstructure demagnetization field coefficient C0 determined by the production process of neodymium iron boron permanent magnet and C1ω(Non-magnetic Phase) determined by the mass fraction of non-magnetic phase in neodymium iron boron permanent magnet, to obtain the model (2).

[0038] As a preferred, the constants in the calculation formula of J S and H A are derived from the book "Sintered Neodymium Iron Boron Rare Earth Permanent Magnet Materials and Technology" published by Metallurgical Industry Press in September 2011, edited by Zhou Shouzeng, Dong Qingfei, and Gao Xuexu. The specific method for determining the constants is as follows:

[0039] The saturation magnetization intensity 1.61T, 1.56T, 1.17T, 0.85T, 0.70T, 0.71T, 0.81T of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in "Sintered Neodymium Iron Boron Rare Earth Permanent Magnet Materials and Technology" are converted into values expressed in kGs of the Gaussian unit system, where T is the Tesla unit in the International Standard Unit System. The converted values are 16.1, 15.6, 11.7, 8.5, 7.0, 7.1, 8.1, respectively, and these values are taken as the influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J S , which is reflected in the calculation formula of J S ;

[0040] The magnetic crystal anisotropy field 5600kA / m, 5840kA / m, 3600kA / m, 4000kA / m, 17600kA / m, 12000kA / m, 7600kA / m corresponding to elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in Sintered Nd-Fe-B Rare Earth Permanent Magnetic Material and Technology are converted into values in kOe expressed in Gauss unit system, wherein kA / m is the international standard unit system of magnetism unit kiloampere / meter, the converted values are respectively: 70.37, 73.39, 45.24, 50.27, 221.17, 150.80, 95.50, and these values are taken as the influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J A . A The influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J

[0041] Since Al has a certain solid solubility in the main phase of the Nd-Fe-B permanent magnet, and when it exists in the crystal lattice, it will reduce the magnetic moment of adjacent Fe atoms in the crystal lattice, according to Sintered Nd-Fe-B Rare Earth Permanent Magnetic Material and Technology, 1 Al atom substitution will cause the molecular magnetic moment of the Nd-Fe-B permanent magnet to decrease by 5.9μB, and the theoretical density of the Nd-Fe-B permanent magnet is 7.58g / cm 3 , the theoretical saturation magnetic polarization strength is 16.1kGs, the molecular magnetic moment of the Nd-Fe-B permanent magnet is 32.3176μB, the relative atomic mass of Al is 26.981, and the relative atomic mass of Fe is 55.845, based on the above data, the influence of element Al on J S is: (32.3176-5.9*14) / 32.3176*(55.845 / 26.981)=-3.2204, and-3.2204 is taken as the influence of element Al on J S . S The influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J is reflected in the calculation formula of J

[0042] For non-rare earth functional elements, they are usually enriched in non-magnetic phases, and have no obvious influence on J S or H A of the main phase of the Nd-Fe-B permanent magnet, but Al element is a relatively obvious exception, so the method of the present application considers the influence of Al element on J S . In addition to Al element, Co element can also be solid-solubilized in the main phase in large amounts, but in the mainstream component system of the Nd-Fe-B permanent magnet at present, Co has almost no influence on J S .

[0043] Compared with the prior art, the present application has the following advantages: the prediction method of the room temperature magnetic performance of the neodymium-iron-boron permanent magnet is a prediction method based on practice and theoretical analysis, the prediction method is transformed from the existing remanence and coercivity theoretical formula, and the prediction method is transformed into a form containing phase composition parameters based on the theoretical phenomenological form. The prediction method calculates the proportion of the main phase (NdFeB) / non-magnetic phase (Non-magnetic Phase), establishes a calculation model of remanence and coercivity, realizes simple, efficient and accurate prediction of the room temperature magnetic performance of the neodymium-iron-boron permanent magnet, can bypass the non-magnetic phase composition and its composition which cannot be quantitatively analyzed, simply and clearly shows and calculates the influence of the composition of the neodymium-iron-boron permanent magnet on the performance from a more macroscopic perspective, and can provide a universal and quantitative rapid solution for the composition design and process design of various neodymium-iron-boron permanent magnets. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the fitting result of the relationship between the main phase and T;

[0045] Figure 2 is the comparison result of the calculated value and the measured value of the remanence of the neodymium-iron-boron permanent magnet samples with different compositions; DETAILED DESCRIPTION

[0046] The present application will be further described in detail below with reference to the embodiments of the drawings.

[0047] A prediction method of the room temperature magnetic performance of a neodymium-iron-boron permanent magnet, comprising the following steps:

[0048] S1, establishing a remanence calculation model:

[0049] Jr=A×J S [1-ω(Non-magnetic Phase)] (1)

[0050] wherein, Jr represents the remanence of the neodymium-iron-boron permanent magnet, A represents a process constant in the production process of the neodymium-iron-boron permanent magnet, J S represents the saturation magnetic polarization intensity of the main phase in the neodymium-iron-boron permanent magnet determined based on composition calculation, J S The unit of J is kGs, and ω(Non-magenetic Phase) represents the mass fraction of the non-magnetic phase in the neodymium-iron-boron permanent magnet;

[0051] J S The calculation formula of J is:

[0052]

[0053] ω (Nd), ω (Pr), ω (Ce), ω (Gd), ω (Tb), ω (Dy), ω (Ho), ω (Fe), ω (Co), ω (Al) respectively represent the mass fraction of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho, Fe, Co, Al in the formula design of the Nd-Fe-B permanent magnet;

[0054] Specifically, the establishment process of the above model (1) is as follows:

[0055] The residual magnetism theoretical formula of the Nd-Fe-B permanent magnet is as follows:

[0056]

[0057] wherein A0 represents the volume fraction of the positive domain in the Nd-Fe-B permanent magnet, β is ω (Non-magnetic Phase) in the model (1) and the model (2), d 磁体 represents the actual density of the Nd-Fe-B permanent magnet, d 理论 represents the theoretical density of the Nd-Fe-B permanent magnet; represents the influence of the compactness of the sintered Nd-Fe-B permanent magnet on the residual magnetism, the value of 100% indicates that the Nd-Fe-B permanent magnet is completely compact inside, and the actual value of is slightly lower than 100%; θ represents the grain orientation degree, and the value of θ reflects the angle difference between the actual magnetization direction of the micro-grains inside the Nd-Fe-B permanent magnet and the macroscopic designed magnetization direction, and the overall comprehensive contribution of the value of θ at different positions inside the Nd-Fe-B permanent magnet is determined by the cosine value of the average value ;

[0058] Since the parameters A0, θ depend on the production process in the actual production of the Nd-Fe-B permanent magnet, A0, and θ are combined into a process constant A in the production process of the Nd-Fe-B permanent magnet, and the model (1) is obtained;

[0059] S2, a coercivity calculation model is established:

[0060] Hcj=B×H A -J S ×[C0+C1ω (Non-magnetic Phase)] (2)

[0061] wherein Hcj represents the coercivity of the Nd-Fe-B permanent magnet, B represents the magnetic crystal anisotropy field coefficient determined by the microstructure of the Nd-Fe-B permanent magnet, H A represents the magnetic crystal anisotropy field determined by the rare earth elements in the Nd-Fe-B permanent magnet, and H AThe unit is kOe. C0 represents the micro-dispersive magnetic field coefficient that is independent of the phase composition of NdFeB permanent magnets and only related to the production process of NdFeB permanent magnets. C1 represents the micro-dispersive magnetic field coefficient that is related to the mass fraction of non-magnetic phase in NdFeB permanent magnets. C0 + C1ω (Non-magnetic Phase) constitutes the complete micro-dispersive magnetic field coefficient.

[0062] H A The formula for calculation is:

[0063]

[0064] Specifically, the process of establishing the above model (2) is as follows:

[0065] The theoretical formula for the coercivity of neodymium iron boron permanent magnets is:

[0066]

[0067] Where K1 represents the magnetocrystalline anisotropy, μ0 represents the free permeability, and μ0 = 4π × 10⁻⁶ -7 H / m, M S That is, J in the models (1) and (2) S , This represents the numerical value after converting the magnetocrystalline anisotropy into equivalent magnetic field strength. That is, H in the model (2). A α ex , α K1 N represents the microstructure coefficients corresponding to exchange coupling, grain orientation, and K1 loss caused by surface defects, respectively. eff N represents the magnetic field dispersion factor. eff The value depends on the phase structure, grain size, and grain shape;

[0068] Because in the actual production of NdFeB permanent magnets, parameter α ex , α K1 Depending on the manufacturing process, therefore, α ex , α K1 The magnetocrystalline anisotropy field coefficient B is determined by the microstructure of the NdFeB permanent magnet, and N... eff The model (2) is further decomposed into the micro-dispersion field coefficient C0 determined by the production process of NdFeB permanent magnets and C1ω (Non-magnetic Phase) determined by the mass fraction of non-magnetic phase in NdFeB permanent magnets.

[0069] S3, based on the literature and statistical analysis of production practice data, it is determined that: A = 0.985, B = 0.65, C0 = 2.4233, C1 = -4.2798, wherein, the determination method of process constant A is: taking 7.58g / cm 3 As the theoretical density of the Nd-Fe-B permanent magnet, in the actual production of the Nd-Fe-B permanent magnet, the actual density of the Nd-Fe-B permanent magnet after sintering is 99.5-99.9% of the theoretical density, that is The grain orientation degree θ is 0-15°, The value of A is 0.985-0.995, based on the above data, A = 0.985 is determined;

[0070] The definition parameter T satisfies:

[0071] T = ω(Fe) + ω(Co) - 1.9ω(Ga)

[0072] Wherein, ω(Ga) represents the mass fraction of element Ga in the formula design of the Nd-Fe-B permanent magnet;

[0073] The mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet satisfies:

[0074] ω(Non-magnetic Phase) = 1-(0.0160×T-0.1650)

[0075] Statistical fitting is performed on the measured data collected in production practice, and the relationship between the above ω(Non-magnetic Phase) and T is obtained, wherein the mass fraction of the main phase is (0.0160×T-0.1650), and the fitting result of the relationship between the main phase and T is shown in Figure 1 . Figure 1 In the formula, x represents T, and y represents the main phase.

[0076] The values of A, J S , ω(Non-magnetic Phase) are substituted into the model (1) to obtain the predicted value of the residual magnetization Jr of the Nd-Fe-B permanent magnet; the values of B, H A , J S , C0, C1, ω(Non-magnetic Phase) are substituted into the model (2) to obtain the predicted value of the coercive force Hcj of the Nd-Fe-B permanent magnet.

[0077] In the above model (1) and model (2), the calculation formula of J S and H A The constants in the calculation formula come from the book "Sintered Nd-Fe-B Rare Earth Permanent Magnet Materials and Technology" edited by Zhou Shouzeng, Dong Qingfei and Gao Xuexu published by Metallurgical Industry Press in September 2011, and the specific determination method of the constants is:

[0078] The saturation magnetic polarization strength 1.61T, 1.56T, 1.17T, 0.85T, 0.70T, 0.71T, 0.81T corresponding to the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in Sintered Nd-Fe-B Rare Earth Permanent Magnetic Material and Technology are converted into values expressed in kGs of the Gaussian unit system, and the converted values are 16.1, 15.6, 11.7, 8.5, 7.0, 7.1, 8.1 (see Table 1 for the converted summary table), and these values are used as the influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J S is reflected in the calculation formula of J S ;

[0079] The magnetic crystal anisotropy field 5600kA / m, 5840kA / m, 3600kA / m, 4000kA / m, 17600kA / m, 12000kA / m, 7600kA / m corresponding to the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in Sintered Nd-Fe-B Rare Earth Permanent Magnetic Material and Technology are converted into values expressed in kOe, and the converted values are 70.37, 73.39, 45.24, 50.27, 221.17, 150.80, 95.50 (see Table 1 for the converted summary table), and these values are used as the influence of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on H A is reflected in the calculation formula of H A ;

[0080] Table 1

[0081]

[0082] The influence of the composition design of rare earth elements on the remanence and coercivity is confirmed based on Table 1;

[0083] Since Al has a certain solid solubility in the main phase of the Nd-Fe-B permanent magnet, and when it exists in the crystal lattice, it will reduce the magnetic moment of adjacent Fe atoms in the crystal lattice. According to Sintered Nd-Fe-B Rare Earth Permanent Magnetic Material and Technology, the substitution of 1 Al atom will cause the molecular magnetic moment of the Nd-Fe-B permanent magnet to decrease by 5.9μB, and the theoretical density of the Nd-Fe-B permanent magnet is 7.58g / cm 3 , the theoretical saturation magnetic polarization strength is 16.1kGs, the molecular magnetic moment of the Nd-Fe-B permanent magnet is 32.3176μB, the relative atomic mass of Al is 26.981, and the relative atomic mass of Fe is 55.845. Based on the above data, the influence of element Al on J S is: (32.3176-5.9*14) / 32.3176*(55.845 / 26.981)=-3.2204, and -3.2204 is used as the influence of element Al on J SThe influence of J S is reflected in the calculation formula of J

[0084] Taking remanence as an example, for Nd-Fe-B permanent magnet samples with different compositions, the remanence of each sample is calculated according to the above model (1) respectively, and the remanence of each sample is actually detected. The comparison results of the calculated values and the actually measured values of the remanences of the Nd-Fe-B permanent magnet samples with different compositions are shown in the following table. Figure 2 . Figure 2 In the table, the abscissa is the actually measured value of the remanence, and the ordinate is the calculated value of the remanence. It can be seen from the table that the calculated value of the remanence and the actually measured value of the remanence have a high fitting degree, which indicates that the prediction method has high accuracy. Figure 2

[0085] The following gives a specific composition of Nd-Fe-B permanent magnet, and its room temperature magnetic properties are predicted by the method of the present application, and compared with the actually measured values of the room temperature magnetic properties.

[0086] The designed composition of the Nd-Fe-B permanent magnet is (Pr 0.25 Nd 0.75 ) 30.5 Gd 1.0 Ho 0.6 Ga 0.15 Al 0.95 (Co,Fe) 65.4 (Ti,Zr,Nb,B,Cu) 1.4 , and the relevant calculation results based on the designed composition are as follows:

[0087] The saturation magnetic polarization intensity J S = 14.652 kGs;

[0088] The parameter T = 65.4-1.9*0.15 = 65.115%;

[0089] The mass fraction of non-magnetic phase ω (Non-magnetic Phase) = 1-(0.0160*T-0.1650) = 12.32%;

[0090] The remanence Jr = 0.985*14.652*(1-0.1232) = 12.654 kGs;

[0091] The magnetic crystal anisotropy field H A = 72.37 kOe;

[0092] The coercive force Hcj = 0.65*72.37-14.652*[2.4233-4.2798*0.1232] = 19.260 kOe.

[0093] ​The sintered Nd-Fe-B permanent magnet is designed according to the above design components, and a sample is obtained. After detection, the Br of the sample is 12.64-12.67 kGs, and the Hcj is 19.57-19.68 kOe, which is well matched with the calculated value, and also indicates that the prediction method has high accuracy.

Claims

1. A method of predicting the room temperature magnetic properties of a neodymium-iron-boron permanent magnet, characterized in that, Comprising the following steps: S1, establishing a residual magnetism calculation model: Jr = A x J S [1 - ω (Non-magnetic Phase)] (1) wherein Jr represents the residual magnetism of the Nd-Fe-B permanent magnet, A represents a process constant in the production process of the Nd-Fe-B permanent magnet, J S represents the saturation magnetic polarization intensity of the main phase in the Nd-Fe-B permanent magnet determined based on component calculation, J S with the unit of kGs, and ω(Non-magnetic Phase) represents the mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet; J S The calculation formula is: Wherein, ω(Nd), ω(Pr), ω(Ce), ω(Gd), ω(Tb), ω(Dy), ω(Ho), ω(Fe), ω(Co), ω(Al) represent the mass fraction of elements Nd, Pr, Ce, Gd, Tb, Dy, Ho, Fe, Co, Al in the formula design of the Nd-Fe-B permanent magnet respectively; S2, establishing a coercivity calculation model: Hcj = B x H A -J S x [Co + Ci ω (Non-magnetic Phase)] (2) wherein Hcj represents the coercivity of the Nd-Fe-B permanent magnet, B represents the magnetic crystal anisotropy field coefficient determined by the microstructure of the Nd-Fe-B permanent magnet, H A represents the magnetic crystal anisotropy field determined by the rare earth elements in the Nd-Fe-B permanent magnet, H A The unit of H is kOe, C0 represents the micro-dispersion magnetic field coefficient separated from the phase composition of the Nd-Fe-B permanent magnet and only related to the production process of the Nd-Fe-B permanent magnet, C1 represents the micro-dispersion magnetic field coefficient related to the mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet, and C0+C1ω(Non-magnetic Phase) constitutes the complete micro-dispersion magnetic field coefficient. H A The formula for calculation is: S3, based on statistical analysis of literature and production practice data, it is determined that: A=0.985, B=0.65, C0=2.4233, C1=-4.2798; The definition parameter T satisfies: T=ω(Fe)+ω(Co)-1.9ω(Ga) Wherein, ω(Ga) represents the mass fraction of element Ga in the formula design of the Nd-Fe-B permanent magnet; The mass fraction of non-magnetic phase in the Nd-Fe-B permanent magnet satisfies: ω(Non-magneticPhase)=1-(0.0160×T-0.1650) The values of A, JS, ω(Non-magnetic Phase) are substituted into the model (1) to obtain the predicted value of the residual magnetization Jr of the Nd-Fe-B permanent magnet; the values of B, H A , J S , C0, C1, ω(Non-magnetic Phase) are substituted into the model (2) to obtain the predicted value of the coercivity Hcj of the Nd-Fe-B permanent magnet.

2. The method of predicting the room temperature magnetic properties of a Nd-Fe-B permanent magnet according to claim 1, characterized in that The establishment process of the model (1) is: The residual magnetism theoretical formula of the Nd-Fe-B permanent magnet is: wherein A0 represents the volume fraction of the positive domain in the Nd-Fe-B permanent magnet, β is ω (Non-magnetic Phase) in the model (1) and the model (2), d 磁体 represents the actual density of the Nd-Fe-B permanent magnet, d 理论 represents the theoretical density of the Nd-Fe-B permanent magnet; represents the influence of the compactness of the sintered Nd-Fe-B permanent magnet on the residual magnetism, 100% indicates that the Nd-Fe-B permanent magnet is completely compact inside, and the actual value of β is slightly lower than 100%; θ represents the grain orientation degree, and the value of θ reflects the angle difference between the actual magnetization direction of the micro-grains inside the Nd-Fe-B permanent magnet and the macroscopic designed magnetization direction. The values of θ at different positions inside the Nd-Fe-B permanent magnet have slight differences, and the overall comprehensive contribution is determined by the volume average value of the cosine values . Since the parameters θ depend on the production process in the actual production of neodymium-iron-boron permanent magnets, the model (1) is obtained by integrating the process constants A in the production process of neodymium-iron-boron permanent magnets. The model (1) is obtained by integrating the process constants A in the production process of neodymium-iron-boron permanent magnets.

3. The method of predicting the room temperature magnetic properties of a Nd-Fe-B permanent magnet according to claim 1, characterized in that The establishment process of the model (2) is: The coercivity theoretical formula of the Nd-Fe-B permanent magnet is: wherein K1 represents the magnetic crystal anisotropy energy, μ0 represents the vacuum permeability, μ0 = 4π x 10 -7 H / m, M S J1 and J2 are respectively the magnetic field intensity and the magnetic field density in the model (1) and the model (2), S , H1 and H2 are respectively the magnetic field intensity and the magnetic field density in the model (2), H1 and H2 are respectively the magnetic field intensity and the magnetic field density in the model (2), A α1 and α2 represent the microstructure coefficients of the exchange coupling and the grain orientation degree, respectively, ex 、 α1 and α2 represent the microstructure coefficients of the exchange coupling and the grain orientation degree, respectively, K1 N1 and N2 represent the demagnetization field factors, N eff N1 and N2 represent the demagnetization field factors, N eff The values of N1 and N2 depend on the phase structure, the grain size and the grain shape. Since the parameter α ex , α K1 depends on the production process, α ex , α K1 is further decomposed into a microstructure-determined magnetic crystal anisotropy field coefficient B and N eff is further decomposed into a production process-determined microstructure-dispersed magnetic field coefficient C0 and C1ω(Non-magnetic Phase) determined by the mass fraction of the non-magnetic phase in the Nd-Fe-B permanent magnet, obtaining the model (2).

4. The method of claim 1, wherein the method is characterized by: J S and H A The constant in the calculation formula is derived from the book "Sintered Nd-Fe-B Rare Earth Permanent Magnetic Materials and Technology" edited by Zhou Shouzeng, Dong Qingfei and Gao Xuexu, published by Metallurgical Industry Press in September 2011. The specific determination method of the constant is: The saturation magnetic polarization strength 1.61T, 1.56T, 1.17T, 0.85T, 0.70T, 0.71T, 0.81T of the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in Sintered Neodymium-Iron-Boron Rare Earth Permanent Magnetic Material and Technology are converted into values in kGs of the Gaussian unit system, and the converted values are 16.1, 15.6, 11.7, 8.5, 7.0, 7.1, 8.1, respectively, and these values are taken as the influence of the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on J S is embodied in the calculation formula of J S ; The magnetic crystal anisotropy field 5600 kA / m, 5840 kA / m, 3600 kA / m, 4000 kA / m, 17600 kA / m, 12000 kA / m, 7600 kA / m corresponding to the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in "Sintered Neodymium Iron Boron Rare Earth Permanent Magnet Material and Technology" are converted into the value expressed in kOe of the Gaussian unit system, and the converted values are: 70.37, 73.39, 45.24, 50.27, 221.17, 150.80, 95.50, and these values are taken as the influence of the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on H A The magnetic crystal anisotropy field 5600 kA / m, 5840 kA / m, 3600 kA / m, 4000 kA / m, 17600 kA / m, 12000 kA / m, 7600 kA / m corresponding to the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho recorded in "Sintered Neodymium Iron Boron Rare Earth Permanent Magnet Material and Technology" are converted into the value expressed in kOe of the Gaussian unit system, and the converted values are: 70.37, 73.39, 45.24, 50.27, 221.17, 150.80, 95.50, and these values are taken as the influence of the elements Nd, Pr, Ce, Gd, Tb, Dy, Ho on H A The calculated formula of H Since Al has a certain solid solubility in the main phase of Nd-Fe-B permanent magnet, and when it exists in the crystal lattice, it will reduce the magnetic moment of adjacent Fe atoms in the crystal lattice. According to Sintered Nd-Fe-B Rare Earth Permanent Magnet Materials and Technology, 1 Al atom substitution will cause the molecular magnetic moment of Nd-Fe-B permanent magnet to decrease by 5.9μB, and the theoretical density of Nd-Fe-B permanent magnet is 7.58g / cm 3 , the theoretical saturation magnetic polarization strength is 16.1kGs, so the molecular magnetic moment of Nd-Fe-B permanent magnet is 32.3176μB, the relative atomic mass of Al is 26.981, the relative atomic mass of Fe is 55.845, based on the above data, the influence of element Al on J S is: (32.3176-5.9*14) / 32.3176*(55.845 / 26.981)=-3.2204, and-3.2204 is taken as the influence of element Al on J S , which is reflected in the calculation formula of J S .

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