A method for improving the intrinsic coercivity of high Ce NdFeB permanent magnets

Abstract

The present invention discloses a method for improving the intrinsic coercive force of a high-Ce NdFeB permanent magnet, comprising the following steps: configuring metal raw materials according to the components; preparing the metal raw materials into quick-setting sheets; crushing the quick-setting sheets into metal coarse powder by hydrogen breaking method; adding an auxiliary agent to the metal coarse powder and stirring and mixing evenly; grinding and screening the metal fine powder by air flow milling; pressing and molding the metal mixed powder under the condition of an oriented magnetic field to obtain a blank; sintering and tempering the blank to obtain a NdFeB 42H magnet. The present invention saves rare earth resources by replacing the addition of PrNd with a high-abundance light rare earth Ce, so that the formula cost is significantly reduced; the present invention effectively improves the corrosion resistance and mechanical properties of the NdFeB magnet by adding elements such as Ce, Al, and Cu.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic functional materials, and in particular to a method for improving the intrinsic coercive force of a high-Ce NdFeB permanent magnet. Background Art

[0002] Since its appearance in 1983, NdFeB magnets have been widely used in computers, automobiles, medical treatment, wind power generation and other fields due to their excellent high remanence, high coercive force and high magnetic energy product. Especially with the enhancement of environmental awareness, the demand for high comprehensive performance NdFeB permanent magnets that can be used in energy-saving and environmentally friendly fields such as electric vehicles and wind power is also growing.

[0003] In recent years, due to the large fluctuations in the market prices of rare earth raw materials such as praseodymium and neodymium, cerium Ce, which is also a rare earth element, has similar structural characteristics to praseodymium and neodymium PrNd, and its reserves in the earth's crust are extremely abundant. Using it to replace Pr and Nd in NdFeB magnets can not only effectively achieve the balanced utilization of rare earth resources, but also significantly reduce the production cost of sintered NdFeB.

[0004] Adding cerium into NdFeB will generate CeFe2 phase, which will lead to a decrease in the coercive force of the magnet, especially when the Ce content exceeds 2%, the coercive force will drop to a lower level. At present, the industry usually adds 1% to 2% cerium or combines 0.75% dysprosium with 5% cerium to ensure that the coercive force of the H series grades is maintained above 17kOe. In contrast, our company can effectively improve the flow properties of the rare earth-rich phase and eliminate the negative impact of the CeFe2 phase on the intrinsic coercive force after adding Ce by optimizing the tempering process; it can achieve the goal of a coercive force of more than 17kOe using a magnet with a cerium content of 3% to 5% without adding dysprosium.

[0005] There have been some studies on the sintering process of NdFeB magnets, but there is a lack of theoretical and systematic research. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for improving the intrinsic coercive force of high Ce NdFeB permanent magnets, the purpose of which is to provide a method for saving heavy rare earth resources by adding high-abundance rare earth Ce, so that the formulation cost is significantly reduced, and at the same time, by adjusting the heat treatment process, the abnormal growth of NdFeB grains in the grains is suppressed, and an Nd-rich phase uniformly distributed in the gaps between the main phase grains is obtained, and finally a high Ce magnet with a coercive force increased by 6% to 8% is obtained, and the method for improving the intrinsic coercive force of high Ce NdFeB permanent magnets with good comprehensive performance is obtained.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: A method for improving the intrinsic coercivity of a high-Ce NdFeB permanent magnet comprises the following steps: S10: configuring metal raw materials according to the composition; S20: preparing the metal raw material into a quick-setting sheet; S30: crushing the quick-setting sheet into coarse metal powder by hydrogen crushing method; S40: adding an auxiliary agent to the metal coarse powder and stirring to mix uniformly; S50: grinding the metal fine powder by jet mill and screening; S60: pressing the metal mixed powder under an oriented magnetic field to obtain a blank; S70: Sintering and tempering the blank to obtain a NdFeB 42H magnet.

[0008] Furthermore, the metal raw materials in S10 include Pr, Nd, Fe, B, Ce, Al, Cu, Zr, Hf, Mo, and W.

[0009] Furthermore, in step S10, the Pr+Nd element content is 25% to 30%, the Ce element content is 2 to 5%, the Al element content is 0.5 to 1%, the Cu element content is 0.1 to 0.3%, the Zr element content is 0 to 3%, the Hf element content is 0 to 3%, the Mo element content is 0 to 3%, and the W element content is 0 to 3%.

[0010] Furthermore, in the step S50, the metal fine powder is jet milled and screened to finally obtain fine powder with an average particle size of 3 μm.

[0011] The beneficial effects of the present invention are: The present invention uses high-abundance light rare earth Ce to replace the addition of PrNd, thereby saving rare earth resources and significantly reducing the formulation cost; The present invention effectively improves the corrosion resistance and mechanical properties of the NdFeB magnet by adding elements such as Ce, Al, and Cu. The present invention combines the fine powder screening process to obtain fine powder with an average particle size of 3 μm and good compression performance; The present invention suppresses the abnormal growth of NdFeB grains in the grains by adjusting the heat treatment process, and obtains the Nd-rich phase uniformly distributed in the gaps between the main phase grains; The coercive force of the NdFeB magnet of the present invention is increased by 6% to 8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The figure is a schematic diagram comparing the performance of 42H NdFeB prepared in the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0013] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings, wherein the same components are represented by the same reference numerals.

[0014] It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0015] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Embodiment 1

[0016] S10: The metal raw materials are configured according to the proportions of Pr+Nd element content 25%, Ce element content 2%, Al element content 0.5%, Cu element content 0.1%, Zr element content 0%, Hf element content 0%, Mo element content 0%, and W element content 0%.

[0017] S20: The prepared metal raw materials are prepared into quick-setting sheets by conventional processes, such as by a twin-roll casting method, and parameters such as the temperature and rotation speed of the twin rolls are controlled to ensure uniform quality of the quick-setting sheets.

[0018] S30: Using hydrogen crushing method, the quick-setting sheets are crushed into metal coarse powder under the conditions of pressure 0.5MPa and temperature 400℃. The hydrogen crushing time is strictly controlled for 3 hours to ensure the particle size and performance of the coarse powder.

[0019] S40: Add appropriate amount of lubricant zinc stearate (addition amount is 0.3%), antioxidant vitamin E (addition amount is 0.05%) and other auxiliary agents to the metal coarse powder, and stir for 30 minutes using a strong stirring device to make the mixture evenly mixed.

[0020] S50: Put the mixed metal coarse powder into the air flow mill, adjust the air flow speed to 200m / s, the classification wheel speed to 3000rpm and other parameters for grinding, and screen out fine powder with an average particle size of 3μm through a screening device.

[0021] S60: Place the metal powder mixture in an orientation magnetic field with a strength of 1.5T and press it at a pressure of 500MPa to obtain a blank. Ensure that the mold temperature is 50°C and uniform during the pressing process.

[0022] S70: The blank is sintered, the heating rate is set to 5℃ / min in the low temperature section (room temperature-500℃), and the temperature is increased at a conventional rate in the high temperature section (500℃-sintering temperature); during the tempering treatment, the first-level tempering temperature is 850℃, the holding time is 2 hours, the second-level tempering temperature is 600℃, and nitrogen is used as the protective atmosphere, and finally NdFeB 42H magnets are obtained. Embodiment 2

[0023] S10: Pr+Nd element content is 28%, Ce element content is 3.5%, Al element content is 0.8%, Cu element content is 0.2%, Zr element content is 1.5%, Hf element content is 1%, Mo element content is 1%, and W element content is 1%.

[0024] S20: The quick-setting sheet is prepared by vacuum melting and casting, and the casting speed, vacuum degree and other parameters are controlled to ensure good crystallization of the quick-setting sheet.

[0025] S30: The conditions of the hydrogen cracking method are pressure 0.6 MPa, temperature 450° C., and time 4 hours.

[0026] S40: Add 0.4% oleamide as a lubricant and 0.08% ascorbic acid as an antioxidant and stir for 40 minutes.

[0027] S50: The air velocity of the jet mill is 220 m / s, the speed of the classifier wheel is 3200 rpm, and the fine powder with an average particle size of 3 μm is screened out.

[0028] S60: orientation magnetic field intensity 1.8T, pressing pressure 600MPa, mold temperature 60℃.

[0029] S70: The heating rate in the low temperature stage (room temperature - 500°C) of sintering treatment is 6°C / min, and the high temperature stage is heated normally; the first tempering temperature is 880°C, the holding time is 2.5 hours, the second tempering temperature is 620°C, the protective atmosphere is argon, and NdFeB 42H magnets are obtained. Embodiment 3

[0030] S10: Pr+Nd element content 30%, Ce element content 5%, Al element content 1%, Cu element content 0.3%, Zr element content 3%, Hf element content 3%, Mo element content 3%, W element content 3%.

[0031] S20: Use the belt-throwing method to prepare quick-setting sheets, optimize the parameters such as the belt-throwing wheel speed and cooling rate to ensure the quality of the quick-setting sheets.

[0032] S30: Hydrogen cracking pressure 0.7 MPa, temperature 500°C, time 5 hours.

[0033] S40: Add 0.5% sodium dodecylbenzene sulfonate as a lubricant and 0.1% propyl gallate as an antioxidant and stir for 50 minutes.

[0034] S50: The air velocity of the jet mill is 250 m / s, the speed of the classifier wheel is 3500 rpm, and the fine powder with an average particle size of 3 μm is screened out.

[0035] S60: orientation magnetic field intensity 2T, pressing pressure 700MPa, mold temperature 70℃.

[0036] S70: The heating rate in the low temperature stage (room temperature - 500°C) of sintering treatment is 7°C / min, and the high temperature stage is heated normally; the first tempering temperature is 900°C, the holding time is 3 hours, the second tempering temperature is 650°C, and the protective atmosphere is helium to obtain NdFeB 42H magnets. Embodiment 4

[0037] S10: The element content ratio is the same as that in Example 1.

[0038] S20: The method for preparing the quick-setting sheet is the same as that in Example 1.

[0039] S30: Same as the hydrogen rupture conditions in Example 1.

[0040] S40: Adding auxiliary agent and stirring in the same manner as in Example 1.

[0041] S50: Same as the jet milling and screening conditions in Example 1.

[0042] S60: Same as the orientation magnetic field pressing conditions in Example 1.

[0043] S70: Sintering treatment is carried out at a conventional heating rate; the primary tempering temperature is 800°C, the holding time is 1.5 hours, the secondary tempering temperature is 600°C, the protective atmosphere is nitrogen, and NdFeB 42H magnets are obtained. Embodiment 5

[0044] S10: The element content ratio is the same as that of Example 2.

[0045] S20: The method for preparing the quick-setting sheet is the same as that in Example 2.

[0046] S30: Same as the hydrogen rupture conditions in Example 2.

[0047] S40: Adding auxiliary agent and stirring in the same manner as in Example 2.

[0048] S50: Same as the jet milling and screening conditions in Example 2.

[0049] S60: Same as the oriented magnetic field pressing conditions in Example 2.

[0050] S70: Sintering treatment is carried out at a conventional heating rate; the first tempering temperature is 830°C, the holding time is 2 hours, the second tempering temperature is 620°C, the protective atmosphere is argon, and NdFeB 42H magnets are obtained. Embodiment 6

[0051] S10: The element content ratio is the same as that in Example 3.

[0052] S20: The method for preparing the quick-setting sheet is the same as that in Example 3.

[0053] S30: Same as the hydrogen rupture conditions in Example 3.

[0054] S40: Adding auxiliary agent and stirring method are the same as those in Example 3.

[0055] S50: Same as the jet milling and screening conditions in Example 3.

[0056] S60: Same as the oriented magnetic field pressing conditions in Example 3.

[0057] S70: Sintering treatment is carried out at a conventional heating rate; the first tempering temperature is 860°C, the holding time is 2.5 hours, the second tempering temperature is 650°C, the protective atmosphere is helium, and NdFeB 42H magnets are obtained. Embodiment 7

[0058] S10: The element content ratio is the same as that of Example 1.

[0059] S20: The method for preparing the quick-setting sheet is the same as that in Example 1.

[0060] S30: Same as the hydrogen rupture conditions in Example 1.

[0061] S40: The same method as in Example 1 for adding auxiliary agents and absorbing and stirring.

[0062] S50: Same as the jet milling and screening conditions in Example 1.

[0063] S60: Implement the same orientation magnetic field pressing conditions as in step 1.

[0064] S70: Sintering treatment is carried out at a conventional heating rate; the primary tempering temperature is 850°C, the holding time is 2 hours, the secondary tempering temperature is 550°C, the protective atmosphere is hydrogen, and NdFeB 42H magnets are obtained. Embodiment 8

[0065] S10: The element content ratio is the same as that of Example 2.

[0066] S20: The method for preparing the quick-setting sheet is the same as that in Example 2.

[0067] S30: Same as the hydrogen rupture conditions in Example 2.

[0068] S40: Adding auxiliary agent and stirring in the same manner as in Example 2.

[0069] S50: Same as the jet milling and screening conditions in Example 2.

[0070] S60: Same as the oriented magnetic field pressing conditions in Example 2.

[0071] S70: Sintering treatment is carried out at a conventional heating rate; the first tempering temperature is 880°C, the holding time is 2.5 hours, the second tempering temperature is 580°C, the protective atmosphere is helium, and NdFeB 42H magnets are obtained. Embodiment 9

[0072] S10: The element content ratio is the same as that of Example 3.

[0073] S20: The method for preparing the quick-setting sheet is the same as that in Example 3.

[0074] S30: Same as the hydrogen rupture conditions in Example 3.

[0075] S40: Adding auxiliary agent and stirring method are the same as those in Example 3.

[0076] S50: Same as the jet milling and screening conditions in Example 3.

[0077] S60: Same as the oriented magnetic field pressing conditions in Example 3.

[0078] S70: Sintering treatment is carried out at a conventional heating rate; the primary tempering temperature is 900°C, the holding time is 3 hours, the secondary tempering temperature is 600°C, and the protective atmosphere is argon, to obtain a NdFeB 42H magnet.

[0079] Comparative Example 1: S10: Pr+Nd element content 25%, Ce element content 0%, Al element content 0.5%, Cu element content 0.1%, Zr element content 0%, Hf element content 0%, Mo element content 0%, W element content 0%. Other rare earth elements such as La and Y are added to make up the total amount of rare earths to the normal range, ensuring that the content of other elements remains unchanged.

[0080] S20: The method for preparing the quick-setting sheet is the same as that in Example 1.

[0081] S30: Same as the hydrogen rupture conditions in Example 1.

[0082] S40: Adding auxiliary agent and stirring in the same manner as in Example 1.

[0083] S50: Same as the jet milling and screening conditions in Example 1.

[0084] S60: Same as the orientation magnetic field pressing conditions in Example 1.

[0085] S70: Sintering and tempering are performed in the same manner as in Example 1 to obtain a NdFeB 42H magnet.

[0086] Comparative Example 2: S10: Pr+Nd element content is 28%, Ce element content is 0%, Al element content is 0.8%, Cu element content is 0.2%, Zr element content is 1.5%, Hf element content is 1%, Mo element content is 1%, W element content is 1%, and the method of supplementing the total amount of rare earth is the same as that of Comparative Example 1.

[0087] S20: The method for preparing the quick-setting sheet is the same as that in Example 2.

[0088] S30: Same as the hydrogen rupture conditions in Example 2.

[0089] S40: Adding auxiliary agent and stirring in the same manner as in Example 2.

[0090] S50: Same as the jet milling and screening conditions in Example 2.

[0091] S60: Same as the oriented magnetic field pressing conditions in Example 2.

[0092] S70: Sintering and tempering are performed in the same manner as in Example 2 to obtain a NdFeB 42H magnet.

[0093] Comparative Example 3: S10: Pr+Nd element content is 30%, Ce element content is 0%, Al element content is 1%, Cu element content is 0.3%, Zr element content is 3%, Hf element content is 3%, Mo element content is 3%, W element content is 3%, and the method of supplementing the total amount of rare earth is the same as that of Comparative Example 1.

[0094] S20: The method for preparing the quick-setting sheet is the same as that in Example 3.

[0095] S30: Same as the hydrogen rupture conditions in Example 3.

[0096] S40: Adding auxiliary agent and stirring method are the same as those in Example 3.

[0097] S50: Same as the jet milling and screening conditions in Example 3.

[0098] S60: Same as the oriented magnetic field pressing conditions in Example 3.

[0099] S70: Sintering and tempering are performed in the same manner as in Example 3 to obtain a NdFeB 42H magnet.

[0100] Comparative Example 4: S10: Pr+Nd element content is 25%, Ce element content is 0.5%, Al element content is 0.5%, Cu element content is 0.1%, Zr element content is 0%, Hf element content is 0%, Mo element content is 0%, and W element content is 0%.

[0101] S20: The method for preparing the quick-setting sheet is the same as that in Example 1.

[0102] S30: Same as the hydrogen rupture conditions in Example 1.

[0103] S40: Adding auxiliary agent and stirring in the same manner as in Example 1.

[0104] S50: Same as the jet milling and screening conditions in Example 1.

[0105] S60: Comparative Example 1 Oriented Magnetic Field Pressing Conditions.

[0106] S70: Sintering and tempering are performed in the same manner as in Example 1 to obtain a NdFeB 42H magnet.

[0107] Comparative Example 5: S10: Pr+Nd element content 28%, Ce element content 1%, Al element content 0.8%, Cu element S20: The method for preparing the quick-setting sheet is the same as that in Example 2.

[0108] S30: Same as the hydrogen rupture conditions in Example 2.

[0109] S40: Adding auxiliary agent and stirring in the same manner as in Example 2.

[0110] S50: Same as the jet milling and screening conditions in Example 2.

[0111] S60: Same as the oriented magnetic field pressing conditions in Example 2.

[0112] S70: Sintering and tempering are performed in the same manner as in Example 2 to obtain a NdFeB 42H magnet.

[0113] Comparative Example 6: S10: Pr+Nd element content is 30%, Ce element content is 2%, Al element content is 1%, Cu element content is 0.3%, Zr element content is 3%, Hf element content is 3%, Mo element content is 3%, and W element content is 3%.

[0114] S20: The method for preparing the quick-setting sheet is the same as that in Example 3.

[0115] S30: Same as the hydrogen rupture conditions in Example 3.

[0116] S40: Adding auxiliary agent and stirring method are the same as those in Example 3.

[0117] S50: Same as the jet milling and screening conditions in Example 3.

[0118] S60: Same as the oriented magnetic field pressing conditions in Example 3.

[0119] S70: Sintering and tempering are performed in the same manner as in Example 3 to obtain a NdFeB 42H magnet.

[0120] Comparative Example 7: S10: Pr+Nd element content 25%, Ce element content 2.5%, Al element content 0.5%, Cu element content 0.1%, Zr element content 0%, Hf element content S20: The method for preparing the quick-setting sheet is the same as that in Example 1.

[0121] S30: Same as the hydrogen rupture conditions in Example 1.

[0122] S40: Adding auxiliary agent and stirring in the same manner as in Example 1.

[0123] S50: Same as the jet milling and screening conditions in Example 1.

[0124] S60: Same as the orientation magnetic field pressing conditions in Example 1.

[0125] S70: Sintering and tempering are performed in the same manner as in Example 1 to obtain a NdFeB 42H magnet.

[0126] Comparative Example 8: S10: Pr+Nd element content is 28%, Ce element content is 3%, Al element content is 0.8%, Cu element content is 0.2%, Zr element content is 1.5%, Hf element content is 1%, Mo element content is 1%, and W element content is 1%.

[0127] S20: The method for preparing the quick-setting sheet is the same as that in Example 2.

[0128] S30: Same as the hydrogen rupture conditions in Example 2.

[0129] S40: Adding auxiliary agent and stirring in the same manner as in Example 2.

[0130] S50: Same as the jet milling and screening conditions in Example 2.

[0131] S60: Same as the orientation magnetic field pressing conditions in Example 2.

[0132] S70: Sintering and tempering are performed in the same manner as in Example 2 to obtain a NdFeB 42H magnet.

[0133] Comparative Example 9: S10: Pr+Nd element content is 30%, Ce content is 4%, Al element content is 1%, Cu element content is 0.3%, Zr element content is 3%, Hf element content is 3%, Mo element content is 3%, and W element content is 3%.

[0134] S20: The method for preparing the quick-setting sheet is the same as that in Example 3.

[0135] S30: Same as the hydrogen rupture conditions in Example 3.

[0136] S40: Adding auxiliary agent and stirring method are the same as those in Example 3.

[0137] S50: Same as the jet milling and screening conditions in Example 3.

[0138] S60: Same as the oriented magnetic field pressing conditions in Example 3.

[0139] S70: Sintering and tempering are performed in the same manner as in Example 3 to obtain a NdFeB 42H magnet.

[0140] The performance comparison of 42H NdFeB prepared in Examples 1-9 and Comparative Examples 1-9 is shown in Table 1.

[0141] The performance comparison of 42H NdFeB obtained in Examples 1-9 and Comparative Examples 1-9 is shown in Table 1: Table 1 By adding high-abundance rare earth Ce, heavy rare earth resources are saved, making the formula cost significantly reduced. At the same time, by adjusting the heat treatment process, the abnormal growth of NdFeB grains in the grains is suppressed, and an Nd-rich phase evenly distributed in the gaps between the main phase grains is obtained. Finally, a high Ce magnet with a coercive force increased by 6% to 8% is obtained, and it has good comprehensive performance.

[0142] The present invention uses high-abundance light rare earth Ce to replace the addition of PrNd, thereby saving rare earth resources and significantly reducing the formulation cost; The present invention effectively improves the corrosion resistance and mechanical properties of the NdFeB magnet by adding elements such as Ce, Al, and Cu. The present invention combines the fine powder screening process to obtain fine powder with an average particle size of 3 μm and good compression performance; The present invention suppresses the abnormal growth of NdFeB grains in the grains by adjusting the heat treatment process, and obtains the Nd-rich phase uniformly distributed in the gaps between the main phase grains; The coercive force of the NdFeB magnet of the present invention is increased by 6% to 8%.

[0143] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the intrinsic coercivity of high Ce NdFeB permanent magnets, characterized in that: The following steps are involved: S10: configuring metal raw materials according to the composition; S20: preparing the metal raw material into a quick-setting sheet; S30: crushing the quick-setting sheet into coarse metal powder by hydrogen crushing method; S40: adding an auxiliary agent to the metal coarse powder and stirring to mix uniformly; S50: grinding the metal fine powder by jet mill and screening; S60: pressing the metal mixed powder under an oriented magnetic field to obtain a blank; S70: Sintering and tempering the blank to obtain a NdFeB 42H magnet.

2. The method for improving the intrinsic coercivity of high Ce NdFeB permanent magnets according to claim 1, characterized in that: The metal raw materials in S10 include Pr, Nd, Fe, B, Ce, Al, Cu, Zr, Hf, Mo, and W.

3. The method for improving the intrinsic coercivity of high Ce NdFeB permanent magnets according to claim 2, characterized in that: In the step S10, the Pr+Nd element content is 25% to 30%, the Ce element content is 2 to 5%, the Al element content is 0.5 to 1%, the Cu element content is 0.1 to 0.3%, the Zr element content is 0 to 3%, the Hf element content is 0 to 3%, the Mo element content is 0 to 3%, and the W element content is 0 to 3%.

4. The method for improving the intrinsic coercivity of high Ce NdFeB permanent magnets according to claim 1, characterized in that: In the step S50, the metal fine powder is jet milled and screened to finally obtain fine powder with an average particle size of 3 μm.

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