SINTERED NEODYMIUM-IRON-BORON MAGNET AND PREPARATION METHOD THEREOF

Abstract

The present disclosure discloses a sintered neodymium-iron-boron magnet and a preparation method thereof. The sintered neodymium-iron-boron magnet includes the following raw materials in mass percentage: 1%-40% of an iron powder or a steel powder with a magnetic induction intensity of more than 1.2 T, not more than 10% of a praseodymium-neodymium metal hydride powder, and a remainder of a neodymium-iron-boron fine powder, wherein the mass percentages of the above raw materials add up to 100%. The preparation method includes: weighing the raw materials in mass percentage; mixing the weighed raw materials uniformly, and then subjecting to magnetic-field press molding, isostatic pressing, sintering and tempering to obtain the sintered neodymium-iron-boron magnet.

Claims

1. A sintered neodymium-iron-boron magnet, comprising the following raw materials in mass percentage: 1%-40% of an iron powder or a steel powder with a magnetic induction intensity of more than 1.2 T, not more than 10% of a praseodymium-neodymium metal hydride powder, and a remainder of a neodymium-iron-boron fine powder, wherein the mass percentages of the above raw materials add up to 100%.

2. The sintered neodymium-iron-boron magnet according to claim 1, wherein the iron powder is any one of an industrial pure iron powder, a hydroxy iron powder or a carbon-based iron powder or a combination thereof; the steel powder is a low carbon steel powder or a silicon steel powder or a combination of both; and a particle size of the iron powder or the steel powder is in a range of 1-10 microns.

3. The sintered neodymium-iron-boron magnet according to claim 1, wherein the praseodymium-neodymium metal hydride powder is prepared as follows: (1) adding a praseodymium-neodymium metal in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, passing hydrogen gas with a purity of more than 99.99% for decrepitation and hydrogenation to form a praseodymium-neodymium hydride; and (2) milling the praseodymium-neodymium hydride into 1-10 microns by jet milling to obtain the praseodymium-neodymium metal hydride powder.

4. The sintered neodymium-iron-boron magnet according to claim 1, wherein the neodymium-iron-boron fine powder is prepared as follows: (1) weighing the following raw materials in parts by mass: 29-33 parts of a rare earth metal RE, 1-3 parts of an additive metal M, 0.9-1 part of B and 63-69.1 parts of Fe; (2) melting the weighed raw materials in a smelting furnace at 1400-1600° C., then refining for 5 min, and casting and cooling to form a neodymium-iron-boron alloy with a thickness of 1-5 mm; and (3) adding the neodymium-iron-boron alloy in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, passing hydrogen gas with a purity of more than 99.99% for decrepitation to obtain a coarse powder; subsequently, milling the coarse powder into 1-10 microns by jet milling to obtain the neodymium-iron-boron fine powder.

5. The sintered neodymium-iron-boron magnet according to claim 4, wherein the additive metal M is any one of Co, Cu, Al, Ga, Nb or Zr or a combination thereof

6. A method for preparing a sintered neodymium-iron-boron magnet, comprising: step 1: weighing the following raw materials in mass percentage: 1%-40% of an iron powder or a steel powder with a magnetic induction intensity of more than 1.2 T, not more than 10% of a praseodymium-neodymium metal hydride powder, and a remainder of a neodymium-iron-boron fine powder, wherein the mass percentages of the above raw materials add up to 100%; and step 2: mixing the weighed raw materials uniformly, and subjecting to magnetic field-press molding, isostatic pressing, sintering and tempering to obtain the sintered neodymium-iron-boron magnet.

7. The method according to claim 6, wherein the iron powder is any one of an industrial pure iron powder, a hydroxy iron powder or a carbon-based iron powder or a combination thereof; the steel powder is a low carbon steel powder or a silicon steel powder or a combination of both; and a particle size of the iron powder or the steel powder is in a range of 1-10 microns.

8. The method according to claim 6, wherein the praseodymium-neodymium metal hydride powder is prepared as follows: (1) adding a praseodymium-neodymium metal in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, passing hydrogen gas with a purity of more than 99.99% for decrepitation and hydrogenation to form a praseodymium-neodymium hydride; and (2) milling the praseodymium-neodymium hydride into 1-10 microns by jet milling to obtain the praseodymium-neodymium metal hydride powder.

9. The method according to claim 6, wherein the neodymium-iron-boron fine powder is prepared as follows: (1) weighing the following raw materials in parts by mass: 29-33 parts of a rare earth metal RE, 1-3 parts of an additive metal M, 0.9-1 part of B and 63-69.1 parts of Fe; (2) melting the weighed raw materials in a smelting furnace at 1400-1600° C., then refining for 5 min, and casting and cooling to form a neodymium-iron-boron alloy with a thickness of 1-5 mm; and (3) adding the neodymium-iron-boron alloy in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, passing hydrogen gas with a purity of more than 99.99% for decrepitation to obtain a coarse powder; subsequently, milling the coarse powder into 1-10 microns by jet milling to obtain the neodymium-iron-boron fine powder.

10. The method according to claim 9, wherein the additive metal M is any one of Co, Cu, Al, Ga, Nb or Zr or a combination thereof

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a test diagram of the magnetic properties of the sintered neodymium-iron-boron magnet prepared by the preparation method described in the background art.

[0031] FIG. 2 is a test diagram of the magnetic properties of the sintered neodymium-iron-boron magnet prepared in Example 2.

[0032] FIG. 3 is a test diagram of the magnetic properties of the sintered neodymium-iron-boron magnet prepared in Example 4.

[0033] FIG. 4 is a test diagram of the magnetic properties of the sintered neodymium-iron-boron magnet prepared in Example 6.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Example 1 A sintered neodymium-iron-boron magnet was provided, which included the following raw materials in mass percentage: 18.5% of an industrial pure iron powder with a magnetic induction intensity of more than 1.2 T and a particle size in a range of 1-10 microns, 1.5% of a praseodymium-neodymium metal hydride powder, and 80% of a neodymium-iron-boron fine powder, wherein the mass percentages of above raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw materials.

[0035] Among them, the praseodymium-neodymium metal hydride powder was prepared as follows:

[0036] (1) a praseodymium-neodymium metal was added in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation and hydrogenation to form a praseodymium-neodymium hydride;

[0037] (2) the praseodymium-neodymium hydride was milled into 1-10 microns by jet milling to obtain the praseodymium-neodymium metal hydride powder.

[0038] The neodymium-iron-boron fine powder was prepared as follows:

[0039] (1) the following raw materials were weighed in parts by mass: 31 parts of a rare earth metal RE, 2 parts of an additive metal M, 0.9 parts of B and 66.1 parts of Fe; in this example, the rare earth metal RE included 29 parts of a praseodymium-neodymium alloy and 2.0 parts of Dy in parts by mass, and the additive metal M included 1 part of Co, 0.15 parts of Cu, 0.4 parts of Al, 0.2 parts of Ga, 0.1 parts of Zr and 0.15 parts of Nb in parts by mass;

[0040] (2) the weighed raw materials were melted in a smelting furnace at 1400-1600° C., then refined for 5 min, and casted and cooled to form a neodymium-iron-boron alloy with a thickness of 1-5 mm;

[0041] (3) the neodymium-iron-boron alloy was added in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation to obtain a coarse powder;

[0042] then the coarse powder was milled into 1-10 microns by jet milling to obtain the neodymium-iron-boron fine powder.

[0043] Example 2 The preparation method of the sintered neodymium-iron-boron magnet in Example 1 was provided, which included the following steps:

[0044] step 1: the following raw materials were weighed in mass percentage: 18.5% of an industrial pure iron powder with a magnetic induction intensity of more than 1.2 T and a particle size in a range of 1-10 microns, 1.5% of a praseodymium-neodymium metal hydride powder, and 80% of a neodymium-iron-boron fine powder, wherein the mass percentages of above raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw materials;

[0045] step 2: the weighed raw materials were mixed uniformly and subjected to magnetic field-press molding, isostatic pressing, sintering and tempering to obtain the sintered neodymium-iron-boron magnet, wherein the specific preparation process was as follows: the weighed raw materials were mixed uniformly; the mixed raw materials were placed in a molding press with a magnetic field of more than 1.2 T for orientation molding (so that the magnetic field direction of the powder particles was consistent with that of the press), and then compressed at a pressure of 0.1-1 MPa to a density of 3.6-4.5 g/cm.sup.3, followed by compressed at a pressure of 150-250 MPa with an isostatic press to a density of 4.3-4.7 g/cm.sup.3; subsequently, the resultant was placed in a vacuum sintering furnace at 1000-1100° C. for 4 h, and was tempered at 880-950° C. for 3 h and then tempered at 440-640° C. for 4 h to obtain the sintered neodymium-iron-boron magnet.

[0046] Compared with the prior art (i.e. the preparation method described in the background art), the usage amount of rare earth elements in this example is reduced by 13 .66%.

[0047] Example 3 A sintered neodymium-iron-boro magnet was provided, which included the following raw materials in mass percentage: 40% of a carbon-based iron powder with a magnetic induction intensity of more than 1.2 T and a particle size in a range 1-10 microns, 4% of a praseodymium-neodymium metal hydride powder, and 56% of a neodymium-iron-boron fine powder, wherein the mass percentages of raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw material.

[0048] The praseodymium-neodymium metal hydride powder was prepared as follows:

[0049] (1) a praseodymium-neodymium metal was added in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation and hydrogenation to form a praseodymium-neodymium hydride;

[0050] (2) the praseodymium-neodymium hydride was milled into 1-10 microns by jet milling to obtain the powder of praseodymium-neodymium metal hydride powder.

[0051] The neodymium-iron-boron fine powder was prepared as follows:

[0052] (1) the following raw materials were weighed in parts by mass: 32 parts of a rare earth metal RE, 2 parts of an additive metal M, 1 part of B and 65 parts of Fe; in this example, the rare earth metal RE included 30 parts of a praseodymium-neodymium alloy and 2.0 parts of Tb in parts by mass, and the additive metal M included 1 part of Co, 0.15 parts of Cu, 0.4 parts of Al, 0.2 parts of Ga, 0.1 parts of Zr, and 0. 15 parts of Nb in parts by mass.

[0053] (2) the weighed raw materials were melted in a smelting furnace at 1400-1600° C., then refined for 5 min, and casted and cooled to form a neodymium-iron-boron alloy with a thickness of 1-5 mm;

[0054] (3) the neodymium-iron-boron alloy was added into a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation to obtain a coarse powder; then the coarse powder was milled into 1-10 microns by jet milling to obtain the neodymium-iron-boron fine powder.

[0055] Example 4 The preparation method of the sintered neodymium-iron-boron magnet in Example 3 was provided, which included the following steps:

[0056] Step 1, the raw materials were weighed according to the following mass percentage: 40% of carbon-based iron powder with a magnetic induction intensity of more than 1.2 T and a particle size of 1-10 microns, 4% of hydride powder of praseodymium-neodymium, 56% of a neodymium-iron-boron fine powder, wherein the mass percentages of above raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw materials.

[0057] step 2, the weighed raw materials were mixed uniformly and subjected to magnetic field-press molding, isostatic pressing, sintering, and tempering to obtain the sintered neodymium-iron-boron magnet, wherein the specific preparation process was as follows: the weighed raw materials were mixed uniformly, the mixed raw materials were placed in a molding press with a magnetic field of more than 1.2 T for orientation molding (so that the magnetic field direction of the powder particles was consistent with that press), and then compressed at a pressure of 0.1-1 MPa to a density of 3.6-4.5 g/cm.sup.3, followed by compressed at a pressure of 150-250 MPa with an isostatic press to a density of 4.3-4.7 g/cm.sup.3 ; subsequently, the resultant was placed in a vacuum sintering furnace at 1000-1100° C. for 4 h, and was tempered at 880-950° C. for 3 h, and then tempered at 440-640° C. for 4 h to obtain the sintered neodymium-iron-boron magnet.

[0058] Compared with the prior art (i.e. the preparation method described in the background art), the usage amount of rare earth elements in this example is reduced by 31.5%.

[0059] Example 5 A sintered neodymium-iron-boron magnet was provided, which included the following raw materials in mass percentage: 8% of a low carbon steel powder with a magnetic induction intensity of more than 1.2 T and a particle size in a range of 1-10 microns, 1% of a praseodymium-neodymium metal hydride powder, and 91% of a neodymium-iron-boron fine powder, wherein the mass percentages of above raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw material.

[0060] The praseodymium-neodymium metal hydride powder was prepared as follows:

[0061] (1) a praseodymium-neodymium metal was added in a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation and hydrogenation to form a praseodymium-neodymium hydride;

[0062] (2) the praseodymium-neodymium hydride was milled into 1-10 microns by a jet milling to obtain the praseodymium-neodymium metal hydride powder.

[0063] The neodymium-iron-boron fine powder was prepared as follows:

[0064] (1) the following raw materials were weighed in parts by mass: 30 parts of a rare earth metal RE, 1 part of an additive metal M, 0.9 parts of B and 68.1 parts of Fe; in this example, the rare earth metal RE included 27 parts of a praseodymium-neodymium alloy and 3.0 parts of Tb in parts by mass, and the additive metal M included 0.2 parts of Co, 0.15 parts of Cu, 0.45 parts of Al, 0.1 parts of Ga, and 0.1 parts of Zr in parts by mass;

[0065] (2) the weighed raw materials were melted in a smelting furnace at 1400-1600° C., then refined for 5 min, and casted and cooled to form a neodymium-iron-boron alloy with a thickness of 1-5 mm;

[0066] (3) the neodymium-iron-boron alloy was added into a rotary hydrogen decrepitation furnace, and after pumping to a vacuum degree of less than 2 Pa, hydrogen gas with a purity of more than 99.99% was introduced for decrepitation to obtain a coarse powder; then the coarse powder was milled into 1-10 microns by jet milling to obtain the neodymium-iron-boron fine powder.

[0067] Example 6 The preparation method of the sintered neodymium-iron-boron magnet in Example 5 was provided, which included the following steps:

[0068] step 1: the following raw materials were weighed in mass percentage: 8% of a low carbon steel powder with a magnetic induction intensity of more than 1.2 T and a particle size in a range of 1-10 microns, 1% of a praseodymium-neodymium metal hydride powder, and 91% of neodymium-iron-boron fine powder, wherein the mass percentages of above raw materials added up to 100%, and a lubricant was added in an amount of 1‰ of the total mass of the raw materials;

[0069] step 2, the weighed raw materials were mixed uniformly and subjected to magnetic field-press molding, isostatic pressing, sintering, and tempering to obtain the sintered neodymium-iron-boron magnet, wherein the specific preparation process was as follows: the weighed raw materials were mixed uniformly; the mixed raw materials were placed in a molding press with a magnetic field of more than 1.2 T for orientation molding (so that the magnetic field direction of the powder particles was consistent with that of the press), and then compressed at a pressure of 0.1-1 MPa to a density of 3.6-4.5 g/cm.sup.3, followed by compressed at a pressure of 150-250 MPa with an isostatic press to a density to 4.3-4.7 g/cm.sup.3; subsequently, the resultant was placed in a vacuum sintering furnace at 1000-1100° C. for 4 h, and was tempered at 880-950° C. for 3 h, and then tempered at 440-640° C. for 4 h to obtain the sintered neodymium-iron-boron magnet.

[0070] Compared with the prior art (i. e. the preparation method described in the background art), the usage amount of rare earth elements in this example is reduced by 5.55%.

[0071] The comparison of the magnetic properties of the sintered neodymium-iron-boron magnets prepared in Examples 2, 4, 6 and the prior art (i.e. the preparation method described in the background art) is shown in the table below and FIGS. 1-4.

TABLE-US-00001 Remanence Br/kGs Intrinsic coercivity Hcj/koe Prior art 13.03 20.77 Example 2 12.81 17.55 Example 4 12.48 19.65 Example 6 12.98 20.55

[0072] The test method is based on GB/T 13560-2017, “Sintered neodymium iron boron permanent magnets”.

[0073] From the data in the above table, it can be seen that the magnetic properties of the sintered neodymium-iron-boron magnet prepared by the formulation and preparation method of the present disclosure is comparable to that of the sintered neodymium-iron-boron magnet prepared in the prior art, while the amount of the rare earth is greatly reduced, thereby reducing the cost of raw materials, and meanwhile saving a lot of rare earth resources.

[0074] The above are only the preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.