High-cerium grain boundary diffusion matrix with high thermal attenuation resistance and grain boundary diffusion process thereof

Abstract

The invention discloses a high-cerium grain boundary diffusion matrix with high thermal attenuation resistance and a grain boundary diffusion process thereof, and a raw material composition is subjected to smelting, heat treatment, hydrogen demolishing, jet milling, powder screening, powder mixing, pressing and sintering treatment to obtain a neodymium iron boron 38M-15 magnet. The preparation method comprises the following steps: firstly, carrying out multi-line cutting, double-sided grinding and ultrasonic cleaning treatment to obtain a to-be-diffused original sheet (with the thickness of 4mm), adhering 0.9 wt% or more and 1.5 wt% or less of DyF3 on the surface, diffusing for 30-35 hours at the temperature of 900 DEG C, and then tempering for 5-6 hours at the temperature of 600-650 DEG C to obtain a diffused product. According to the invention, the heavy rare earth resource is saved, the formula cost is reduced, the temperature coefficient is reduced, the thermal attenuation resistance is improved, and the comprehensive performance is good.

Description

Technical Field

[0001] The present invention relates to the technical field of neodymium iron boron metal materials, and in particular to a grain boundary diffusion matrix with high cerium content and high thermal attenuation resistance and a grain boundary diffusion process thereof. Background Art

[0002] Sintered NdFeB, as the third generation of rare earth permanent magnet materials, is currently the most widely used and strongest magnetic material. It is widely used in important fields such as national defense, machinery, computers and new energy. With the rapid development of modern science and technology and the information industry, the demand for NdFeB rare earth permanent magnets is also increasing day by day. The increasing consumption of rare earth resources has also become an increasingly serious problem, which has made the prices of various rare earth elements higher and higher. Moreover, rare earth elements are often mined in the form of paragenetic ores. As the elements such as Pr, Nd, Dy, and Tb used in the preparation of sintered NdFeB are consumed in large quantities, the cheap and abundant Ce element is accumulated in large quantities. Therefore, in order to reduce production costs and promote the efficient and balanced utilization of rare earth resources in my country, the use of abundant Ce elements to partially replace Nd in Nd-Fe-B magnets has become a research hotspot in the field of rare earth permanent magnets in recent years. Due to the Ce2Fe 14 Due to the inherently low intrinsic properties of Ce magnets, researchers have developed techniques such as dual-phase alloy preparation, grain boundary addition, and grain boundary diffusion to improve the overall magnetic properties of Ce magnets and expand their applications. Grain boundary diffusion reduces the use of heavy rare earths such as Dy and Tb and increases the utilization of light rare earths, making it a research hotspot in the rare earth permanent magnet field in recent years. Summary of the Invention

[0003] In order to solve the problem of heavy rare earth resources and thermal attenuation resistance of NdFeB magnets, the present invention provides a high-cerium grain boundary diffusion substrate with high thermal attenuation resistance and a grain boundary diffusion process thereof.

[0004] The present invention provides the following technical solutions:

[0005] The grain boundary diffusion matrix with high cerium and high thermal attenuation resistance is composed of NdFeB magnet material.

[0006] In terms of weight percentage, NdFeB magnet materials include the following components:

[0007] R: 31wt%≤R≤34wt%;

[0008] T: 66wt%≤T≤69wt%;

[0009] B: 0.5wt%≤B≤2wt%;

[0010] M: 2wt%≤M≤8wt%,

[0011] R is a rare earth element, and R includes light rare earth elements and heavy rare earth elements;

[0012] The T mainly includes Fe;

[0013] The M is one or more of Cu, Ga, Co, Zr, Gd and Ti.

[0014] Furthermore, the light rare earth element is Ce, and the total content of Ce is 9-11 wt%; the heavy rare earth element is Dy.

[0015] Furthermore, the Zr element content is 0-0.3%, the Co element content is 0-0.5%, the Cu element content is 0-0.3%, the Ga element content is 0-0.3%, the Gd element content is 0-2%, and the Ti element content is 0-0.3%.

[0016] The grain boundary diffusion process of the grain boundary diffusion matrix with high cerium and high thermal attenuation resistance,

[0017] S10: preparing a NdFeB magnet material mixture into a quick-setting sheet by smelting, and heat-treating the quick-setting sheet at a temperature of 500-1150° C. for 4-24 hours and a rapid cooling temperature of -170-10° C.;

[0018] S20: crushing the quick-setting sheet into coarse metal powder by hydrogen crushing method, the hydrogen crushing temperature is 400-600° C., and the time is 4-24 hours;

[0019] S30: adding an additive to the coarse metal powder, stirring, and grinding into fine powder;

[0020] S40: screening the metal fine powder to obtain fine powder with an average particle size of 1-3 μm;

[0021] S50: pressing the metal powder mixture into a shape under an oriented magnetic field to obtain a blank;

[0022] S60: performing a sintering treatment and a two-time tempering treatment on the blank to obtain the NdFeB 38M-15 magnet;

[0023] S70: 38M-15 magnets are cut into 4-7mm thick square pieces by multi-wire cutting. The cut square pieces are double-sided ground and ultrasonically cleaned to remove any surface oxide or oil stains. The double-sided ground square pieces are evenly coated with a layer of dysprosium fluoride powder by spraying.

[0024] S80: The sprayed square pieces are regularly placed in a material box and transferred to a diffusion furnace, followed by high-temperature heat treatment to obtain a product after grain boundary diffusion.

[0025] The pressure of the pressing molding in step S50 is 200-700Kg / cm 2 , orientation field (2-20)X104Oe, oxygen concentration during pressing process is less than 100ppm.

[0026] In step S60, the sintering temperature is 1000°C-1100°C, the sintering time is 5-6 hours, and then rapid cooling is performed; then tempering treatment is performed, the first tempering temperature is 800°C-900°C, the tempering time is 1-6 hours, and the second tempering time is 550°C-650°C, and the second tempering time is 1-6 hours.

[0027] In step S70, a 14*10*4 product was tried and the PC value was 0.778; the double-sided grinding amount was 5 wires, the ultrasonic cleaning temperature was 50-60°C, the cleaning agent was sodium citrate, sodium silicate or sodium phosphate, the cleaning agent concentration in deionized water was 1-2wt%, and hot air at 70-80°C was used for drying; dysprosium fluoride and 95% alcohol were mixed into a slurry and ground for 0-2h, the slurry particle size D50 = 0.9-1.5um, and the product after spraying was 0.9wt%≤DyF3≤1.5wt%.

[0028] In step S80, the diffusion temperature is 900° C., the diffusion time is between 30-35 hours, and then argon gas is filled and air-cooled; then aging is performed, the aging temperature is between 600-650° C., the aging time is between 5-6 hours, and then argon gas is filled and air-cooled.

[0029] The present invention studies the effect of Ce content and diffusion process on the microstructure and magnetic properties of grain boundary diffused Nd-Ce-Fe-B magnets. Ce element replaces Nd in Nd-Fe-B magnets to form Ce2Fe 14 The B main phase grains diffuse the heavy rare earth Dy element from the surface of the magnet into the interior through grain boundary diffusion technology, forming a shell structure with high magnetocrystalline anisotropy field on the outside of the main phase grains, isolating the exchange coupling between the main phase grains, increasing the coercive force of the magnet, and thus improving the high temperature performance of the cerium-containing magnet.

[0030] Compared with the prior art, the present invention has the following beneficial effects: NdFeB magnet material is subjected to smelting, heat treatment, hydrogen crushing, air flow grinding, powder screening, powder mixing, pressing and sintering to obtain NdFeB 38M-15 magnets, and then subjected to multi-wire cutting, double-sided grinding, ultrasonic cleaning, spraying, diffusion and double-sided grinding to obtain the product after grain boundary diffusion.

[0031] (1) The present invention reduces the amount of rare earth PrNd by adding Ce elements, saves heavy rare earth resources, and greatly reduces the formulation cost;

[0032] (2) The present invention reduces the amount of heavy rare earth Dy added through grain boundary diffusion technology, saves heavy rare earth resources, greatly reduces the formulation cost, and improves the thermal attenuation resistance of the NdFeB magnet;

[0033] (3) The present invention combines fine powder screening and heat treatment processes to ensure that the grain size of the sintered NdFeB main phase is 2-6 μm, and the prepared neodymium-rich phase is more evenly distributed and the diffusion channel is smoother. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flowchart of the present invention;

[0035] Figure 2 This is a scanning electron microscope image of the NdFeB 38M-15 magnet of the present invention before grain boundary diffusion;

[0036] Figure 3 This is a scanning electron microscope image of the NdFeB 38M-15 magnet after grain boundary diffusion of the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] The high cerium high thermal attenuation resistance grain boundary diffusion matrix and its grain boundary diffusion process of the present invention, embodiment 1

[0039] Batching of metal raw materials:

[0040] PrNd content is 22.5wt%, Zr content is 0.26wt%, B content is 0.91wt%, Co content is 0.3wt%, Cu content is 0.25wt%, Ga content is 0.25wt%, Gd content is 0.71wt%, Ce content is 9wt%, and Ti content is 0.25wt%;

[0041] Melt in a high-temperature belt-spinning furnace at 600 kg / time, and cast the quick-setting sheet at a roller speed of 3 m per second, ultimately obtaining a quick-setting sheet with a thickness of 0.28 mm.

[0042] The quick-setting sheet was then heat treated at 500°C for 24 h and then rapidly cooled;

[0043] The heat-treated quick-setting sheets were placed in a continuous hydrogen powder crushing furnace for hydrogen crushing at a temperature of 480°C for 18 hours.

[0044] The crushed materials after hydrogen pulverization are fed into a jet mill for fine powder preparation, and polyvinyl alcohol is used as an additive to finally obtain a powder with an extremely narrow distribution and an average particle size of 2.92 μm.

[0045] The powder was passivated for 12 hours and then sent into a magnetic orientation press for compaction at a pressure of 200 kg / cm2 and an orientation field of 2 x 104 Oe. The oxygen concentration during the compaction process was less than 100 ppm.

[0046] Finally, sintering treatment is carried out at 1050℃*6h, rapid cooling, and then tempering treatment is carried out at 900℃*5h and 620℃*5h;

[0047] After the blank is baked, the product is cut into 14*10*4 products, and the PC value is 0.778;

[0048] Use a double-sided grinder to grind off 5 strands of the oriented surface to remove the surface oxide layer, then clean it with deionized water at 55°C with sodium citrate / sodium silicate / sodium phosphate detergent, and dry it with hot air at 70°C.

[0049] The slurry of dysprosium fluoride and alcohol (95%) was ground for 1 hour (slurry particle size D50 = 1.3 μm) and evenly sprayed on the oriented surface of the product, with a weight gain of DyF3 = 0.9 wt%;

[0050] The sprayed square pieces are regularly placed in a material box and transferred to a diffusion furnace, followed by high-temperature heat treatment at 900°C*30h with argon air cooling and 600°C*5h with argon air cooling to obtain the product after grain boundary diffusion.

[0051] Example 2

[0052] Batching of metal raw materials:

[0053] PrNd content is 20wt%, Zr content is 0wt%, B content is 0.91wt%, Co content is 0.5wt%, Cu content is 0.25wt%, Ga content is 0.3wt%, Gd content is 0wt%, Ce content is 11wt%, and Ti content is 0.3wt%;

[0054] Melt in a high-temperature belt-spinning furnace at 600 kg / time, and cast the quick-setting sheet at a roller speed of 4 m / s to obtain a quick-setting sheet with a thickness of 0.2 mm.

[0055] The quick-setting sheet was then heat treated at 800°C for 12 h and then rapidly cooled;

[0056] The heat-treated quick-setting sheets were placed in a continuous hydrogen powder crushing furnace for hydrogen crushing at a temperature of 600°C for 4 hours.

[0057] The crushed materials after hydrogen pulverization are fed into a jet mill to prepare fine powder, with polyvinyl alcohol as an additive, and finally a powder with an extremely narrow distribution and an average particle size of 2.96μm is obtained;

[0058] The powder is passivated for 12-24 hours, and then the powder is sent to a magnetic orientation molding press for compression molding, with a pressure of 500 kg / cm2, an orientation field of 10×10⁴Oe, and an oxygen concentration of less than 100 ppm during the pressing process;

[0059] Finally, it is sintered at 1000℃*6h, quickly cooled, and then tempered at 850℃*6h and 650℃*4h;

[0060] After the blank is baked, the product is cut into 14*10*4 products, and the PC value is 0.778;

[0061] Use a double-sided grinder to grind off 5 strands of the oriented surface to remove the surface oxide layer, then clean it with deionized water at 50°C containing sodium citrate / sodium silicate / sodium phosphate detergent, and dry it with hot air at 80°C.

[0062] Grind the slurry of dysprosium fluoride and alcohol (95%) for 2 hours (slurry particle size D50 = 0.9 μm) and evenly spray it on the oriented surface of the product, with a weight gain of DyF3 = 1.2 wt%;

[0063] The sprayed square pieces are regularly placed in a material box and transferred to a diffusion furnace, followed by high-temperature heat treatment at 900°C*32h with argon gas air cooling and 620°C*6h with argon gas air cooling to obtain the product after grain boundary diffusion.

[0064] Example 3

[0065] Batching of metal raw materials:

[0066] PrNd content is 22.5wt%, Zr content is 0.26wt%, B content is 0.91wt%, Co content is 0.3wt%, Cu content is 0.25wt%, Ga content is 0.25wt%, Gd content is 0.71wt%, Ce content is 9wt%, and Ti content is 0.25wt%;

[0067] Melt in a high-temperature belt-spinning furnace at 600 kg / time, and cast the quick-setting sheet at a roller speed of 0.2 m per second to obtain a quick-setting sheet with a thickness of 0.4 mm.

[0068] The quick-setting sheet was then heat treated at 1150°C for 4 h and then rapidly cooled;

[0069] The heat-treated quick-setting sheets were placed in a continuous hydrogen powder crushing furnace for hydrogen pulverization at a temperature of 600°C for 4 hours.

[0070] The crushed materials after hydrogen pulverization are fed into a jet mill for fine powder preparation, and polyvinyl alcohol is used as an additive to finally obtain a powder with an extremely narrow distribution and an average particle size of 2.90 μm.

[0071] The powder was passivated for 24 hours and then sent into a magnetic orientation press for compaction at a pressure of 700 kg / cm2, an orientation field of 20 × 104 Oe, and an oxygen concentration of less than 100 ppm during the compaction process.

[0072] Finally, the steel is sintered at 1100℃ for 5 hours, cooled quickly, and then tempered at 800℃ for 6 hours and 550℃ for 6 hours.

[0073] After the blank is baked, the product is cut into 14*10*4 products, and the PC value is 0.778;

[0074] Use a double-sided grinder to grind off 5 strands of the oriented surface to remove the surface oxide layer, then clean it with deionized water added with sodium citrate / sodium silicate / sodium phosphate detergent at 60°C and dry it with hot air at 70°C;

[0075] The slurry of dysprosium fluoride and alcohol (95%) was ground for 0 hours (slurry particle size D50 = 1.5 μm) and evenly sprayed on the oriented surface of the product, with a weight gain of DyF3 = 1.5 wt%;

[0076] The sprayed square pieces are regularly placed in a material box and transferred to a diffusion furnace, followed by high-temperature heat treatment at 900°C*35h with argon air cooling and 650°C*6h with argon air cooling to obtain the product after grain boundary diffusion.

[0077] Example Results

[0078]

[0079] Figure 2 This is a scanning electron microscope image of the NdFeB 38M-15 magnet of the present invention before grain boundary diffusion. Figure 2 It can be seen that the NdFeB 38M-15 magnet produced by the present invention has a uniform grain size before grain boundary diffusion, and the Nd-rich phase is evenly distributed outside the main phase.

[0080] Figure 3 This is a scanning electron microscope image of the NdFeB 38M-15 magnet after grain boundary diffusion of the present invention. Figure 3 It can be seen that the NdFeB 38M-15 magnet produced by the present invention has a uniform grain size after grain boundary diffusion without significant growth, and the Nd-rich phase is evenly distributed outside the main phase.

[0081] By adding low-heavy rare earth Tb+Dy, heavy rare earth resources are saved, which significantly reduces the formula cost. At the same time, the addition of Zr, W elements and ultrafine nickel powder significantly improves the heat resistance. Combined with fine powder screening and heat treatment process, the grain size of the sintered NdFeB main phase is guaranteed to be 2-6μm, the neodymium-rich phase is evenly distributed, and it has good comprehensive performance.

[0082] The present invention saves heavy rare earth resources by adding light rare earth Ce, significantly reducing the formulation cost. At the same time, the main phase grain size after sintering is controlled to be 2-6 μm, and the neodymium-rich phase is evenly distributed, thereby achieving good comprehensive performance. The heavy rare earth Dy is added by grain boundary diffusion to significantly improve the thermal attenuation resistance.

[0083] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. High cerium grain boundary diffusion matrix with high thermal attenuation resistance, characterized by: The grain boundary diffusion matrix is ​​composed of NdFeB magnet material. In terms of weight percentage, NdFeB magnet materials include the following components: R: 31wt%≤R≤34wt%; T: 66wt%≤T≤69wt%; B: 0.5wt%≤B≤2wt%; M: 2wt%≤M≤8wt%, R is a rare earth element, and R includes light rare earth elements and heavy rare earth elements; The T mainly includes Fe; The M is one or more of Cu, Ga, Co, Zr, Gd and Ti.

2. The high-cerium grain boundary diffusion matrix with high thermal decay resistance according to claim 1, characterized in that: The light rare earth element is Ce, and the total content of Ce is 9-11 wt%; the heavy rare earth element is Dy.

3. The high-cerium grain boundary diffusion matrix with high thermal decay resistance according to claim 1, characterized in that: The Zr element content is 0-0.3%, the Co element content is 0-0.5%, the Cu element content is 0-0.3%, the Ga element content is 0-0.3%, the Gd element content is 0-2%, and the Ti element content is 0-0.3%.

4. The grain boundary diffusion process of the high cerium and high thermal decay resistance grain boundary diffusion matrix according to claim 1, characterized in that: S10: preparing a NdFeB magnet material mixture into a quick-setting sheet by smelting, and heat-treating the quick-setting sheet at a temperature of 500-1150° C. for 4-24 hours and a rapid cooling temperature of -170-10° C.; S20: crushing the quick-setting sheet into coarse metal powder by hydrogen crushing method, the hydrogen crushing temperature is 400-600° C., and the time is 4-24 hours; S30: adding an additive to the coarse metal powder, stirring, and grinding into fine powder; S40: screening the metal fine powder to obtain fine powder with an average particle size of 1-3 μm; S50: pressing the metal powder mixture into a shape under an oriented magnetic field to obtain a blank; S60: performing a sintering treatment and a two-time tempering treatment on the blank to obtain the NdFeB 38M-15 magnet; S70: 38M-15 magnets are cut into 4-7mm thick square pieces by multi-wire cutting. The cut square pieces are double-sided ground and ultrasonically cleaned to remove any surface oxide or oil stains. The double-sided ground square pieces are evenly coated with a layer of dysprosium fluoride powder by spraying. S80: The sprayed square pieces are regularly placed in a material box and transferred to a diffusion furnace, followed by high-temperature heat treatment to obtain a product after grain boundary diffusion.

5. The grain boundary diffusion process of the high cerium and high thermal decay resistance grain boundary diffusion matrix according to claim 4, characterized in that: The pressure of the pressing molding in step S50 is 200-700Kg / cm 2 , orientation field (2-20)X104Oe, oxygen concentration during pressing process is less than 100ppm.

6. The grain boundary diffusion process of the high cerium and high thermal decay resistance grain boundary diffusion matrix according to claim 4, characterized in that: In step S60, the sintering temperature is 1000°C-1100°C, the sintering time is 5-6 hours, and then rapid cooling is performed; then tempering treatment is performed, the first tempering temperature is 800°C-900°C, the tempering time is 1-6 hours, and the second tempering time is 550°C-650°C, and the second tempering time is 1-6 hours.

7. The grain boundary diffusion process of the high cerium and high thermal decay resistance grain boundary diffusion matrix according to claim 4, characterized in that: In step S70, a 14*10*4 product was tried and the PC value was 0.778; the double-sided grinding amount was 5 wires, the ultrasonic cleaning temperature was 50-60°C, the cleaning agent was sodium citrate, sodium silicate or sodium phosphate, the cleaning agent concentration in deionized water was 1-2wt%, and hot air at 70-80°C was used for drying; dysprosium fluoride and 95% alcohol were mixed into a slurry and ground for 0-2h, the slurry particle size D50 = 0.9-1.5um, and the product after spraying was 0.9wt%≤DyF3≤1.5wt%.

8. The grain boundary diffusion process of the high cerium and high thermal decay resistance grain boundary diffusion matrix according to claim 4, characterized in that: In step S80, the diffusion temperature is 900° C., the diffusion time is between 30-35 hours, and then argon gas is filled and air-cooled; then aging is performed, the aging temperature is between 600-650° C., the aging time is between 5-6 hours, and then argon gas is filled and air-cooled.

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