WO2016058132A1 - 一种稀土永磁体的制备方法 - Google Patents
一种稀土永磁体的制备方法 Download PDFInfo
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- WO2016058132A1 WO2016058132A1 PCT/CN2014/088564 CN2014088564W WO2016058132A1 WO 2016058132 A1 WO2016058132 A1 WO 2016058132A1 CN 2014088564 W CN2014088564 W CN 2014088564W WO 2016058132 A1 WO2016058132 A1 WO 2016058132A1
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- rare earth
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- earth permanent
- permanent magnet
- magnet
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
Definitions
- the invention relates to a method for preparing a rare earth permanent magnet, in particular to a method for improving the internal coercive force H cj of a sintered NdFeB magnet, in particular to a method for improving the coercive force of a sintered NdFeB magnet semi-finished product. .
- the rare earth permanent magnet material is a permanent magnet material in which an intermetallic compound composed of different rare earth elements and transition metal elements (Fe, Co, Ni, etc.) is a main phase. Since its invention in the 1960s, rare earth permanent magnet materials have developed rapidly and have been widely used in many fields. They have become important basic functional materials for modern new technologies, especially in the field of permanent magnet motors. .
- Rare earth permanent magnet motors cover major types such as stepper motors, brushless motors, servo motors and linear motors, and are widely used in computers, printers, household appliances, air conditioner compressors, automotive power steering motors, hybrid or pure electric motors. Important fields such as automotive drive motors/generators, automotive starter motors, ground military motors, and aerospace motors.
- a high-performance sintered NdFeB magnet with iron as its basic component and high coercivity and high magnetic energy product is a rare earth permanent magnet material that has been rapidly developed in the past three decades.
- the NdFeB rare earth permanent magnet material is applied to various motors, which can significantly improve the performance of the motor, reduce the weight of the motor, reduce the size of the motor, and obtain an efficient energy saving effect.
- a 10 kW ordinary permanent magnet generator uses ferrite and the generator weighs 220 kg; while the same power rare earth permanent magnet generator weighs only 92 kg.
- the average power saving rate of rare earth permanent magnet motor is as high as 10%, and the power saving rate of some special motors is even as high as 15%-20%.
- the 1095kW, 230rpm six-pole permanent magnet synchronous motor developed by Siemens in Germany is compatible with the DC motor used in the past.
- the volume is reduced by about 60% and the total loss is reduced by 20%.
- the high performance price ratio of NdFeB also makes it an ideal material for high performance, small size and light weight magnetic functional devices.
- the application of generators, motors and sound systems in automobiles has become increasingly mature, which will greatly promote the development of the NdFeB industry.
- New rare earth permanent magnet motors for various purposes will enter a new stage of development. At present, rare earth permanent magnet motors have become the largest application field of NdFeB magnets, accounting for about 70% of total magnet production.
- Dy 2 Fe 14 B or Td 2 Fe 14 B has a higher magnetocrystalline anisotropy field than Nd 2 Fe 14 B, that is, it is possible to obtain a larger intrinsic coercive force, and Dy or Tb partially replaces the main phase.
- Nd 2 Fe 14 B of Nd (Nd, Dy) 2 Fe 14 B or (Nd, Tb) magnetocrystalline anisotropy field 2 Fe 14 B is larger than the Nd 2 Fe 14 B, and thus a significant improvement in The coercive force of the magnet.
- the adverse effect of this element substitution is to significantly reduce the saturation magnetization of the magnet, so the remanence B r and the maximum magnetic energy product (BH) max of the magnet are significantly reduced because at (Nd, Dy) 2 Fe 14
- the magnetic moments of Nd and Fe in the main phase of B or (Nd,Tb) 2 Fe 14 B are arranged in parallel in the same direction, and the magnetic moments of the two are enhanced superposition; and the magnetic moments of Dy and Tb are arranged in antiparallel with the Fe magnetic moment. , partially canceling the total magnetic moment of the main phase.
- the rare earth ore reserves containing Dy and Tb are scarce and the distribution is very uneven with respect to Nd, and the unit prices of Dy and Tb are much higher than Nd, and this substitution causes an increase in the cost of the magnet.
- some new processes have been used to increase the intrinsic coercivity of sintered NdFeB magnets, as mentioned in the CN101845637A patent, using acidic solvents that soak the magnets in oxides or fluorides of heavy rare earth Dy or Tb. For a certain period of time, heat treatment under Ar gas protection can increase the H cj value.
- a metal powder containing Dy or Tb is used, the metal powder contains Ni or Co, and each powder in the embodiment must contain B, and there must be three steps: first, the surface of the magnet is coated. The layer is further stirred or impacted in the metal powder to adsorb the metal powder, and finally subjected to thermal diffusion treatment, and the H cj is increased by this method.
- the above method can improve H cj to a certain extent, and the surface state of the powder and the magnet can affect the lifting effect of H cj very sensitively, but the above patents do not specify the state of the magnet and the preparation of the powder. It is well known that if the diffusion method is used to diffuse Dy or Tb compounds into the magnet, there is no special requirement for the activity and surface state of the powder. It is very difficult to ensure that the heavy rare earth can diffuse into the magnet, and it is difficult to ensure the diffusion process. Reproducibility and process stability make it difficult to industrially prepare magnets that reliably increase H cj .
- the maximum magnetic energy product of pure Nd 2 Fe 14 B intermetallic compound is 64 MGOe, and in practice, in order to obtain high intrinsic coercive force H cj , on the main phase grain boundary with Nd 2 Fe 14 B crystal structure There must be a presence of a rare earth-rich phase, and the process can also cause various factors that deviate from the ideal state of the magnet, such as porosity, impurities, grain orientation, and the like.
- the maximum magnetic energy product of the sintered Nd-Fe-B magnet is proportional to the square of the remanence B r of the magnet, and the following relationship can express the relationship between B r and various influencing factors:
- I s 4 ⁇ M s is the saturation magnetic polarization of the main phase
- ⁇ is the temperature influence factor of I s
- ⁇ / ⁇ 0 is the relative density
- ⁇ is the volume percentage of the non-magnetic phase
- f is the orientation factor
- the intrinsic coercive force H cj of the NdFeB sintered magnet is expressed as follows:
- H cj CH a -NI s
- H a is the magnetocrystalline anisotropy field of the main phase
- C depends on the interaction between the main phase grains and its interfacial grains
- N is the effective demagnetization factor
- C and N are sensitively dependent on the grain size of the sintered magnet And its distribution, as well as orientation and boundary features between adjacent grains.
- the B r and H cj of the magnet are basically determined.
- the intrinsic coercive force H cj depends on the magnetocrystalline anisotropy field H a of the main phase and also depends on the interaction between the main phase grains and its interfacial grains. And the boundary features between adjacent grains.
- the object of the present invention is to improve the magnetic anisotropy field of the surface layer of the main phase by improving the boundary characteristics of the grain boundary and the interaction with the main phase grains by the grain boundary diffusion method, thereby improving the sintered ferroniobium
- the intrinsic coercive force H cj of the boron magnet has little effect on the remanence B r and the maximum magnetic energy product (BH) max .
- a method for preparing a rare earth permanent magnet according to the present invention is characterized in that the method comprises a blank magnet preparation step, a permeation material coating step and a heat treatment step which do not include a tempering treatment step.
- the preparation process of the green magnet which does not include the tempering treatment step according to the present invention means that the blank magnet is formed through the batch-alloy smelting-pulverizing-pulverizing-forming-sintering process.
- the permeation material coating process of the present invention comprises the steps of preparing a permeable material powder, preparing the osmotic material powder into a coating solution, and coating the green body magnet in the coating solution.
- the preparation process of the osmotic material powder of the present invention comprises:
- the heat treatment process of the present invention is a secondary heat treatment, and the secondary heat treatment includes:
- the invention adopts a rare earth intermetallic compound as a material for grain boundary diffusion, and has the advantages that the phase and composition of the rare earth intermetallic compound are relatively stable and easy to be broken, and it is easy to prepare into a fine powder; the rare earth intermetallic compound has a wide range of phase forming elements.
- the composition of the rare earth intermetallic compound can be adjusted according to the performance of the magnet.
- the grain boundary diffusion infiltration method of the present invention the boundary characteristics of the grain boundary and its interaction with the main phase crystal grains can be improved, and the intrinsic coercive force H cj of the sintered NdFeB magnet can be improved, and the residual magnetism B r and the maximum The magnetic energy product (BH) max is minimally affected and has a small amount of reduction.
- the present invention is a process for significantly increasing the magnet H cj under the premise of substantially maintaining the remanence and maximum magnetic energy product of the magnet and using a very small amount of heavy rare earth Dy and or Tb.
- a sintered NdFeB billet magnet is prepared according to a conventional process but does not include a tempering step, that is, a billet magnet is prepared through a batch-alloy smelting-pulverizing-molding-forming-sintering process, and the magnet is only sintered but not tempered. (Also known as tempering heat treatment).
- the neodymium iron boron green magnet of the present invention is a magnet which has not been subjected to tempering after sintering, and the magnet has an oxygen content of 4000 ppm or less and a thickness of the magnet in the orientation direction of 10 mm or less.
- a permeable material powder, or a coating powder is prepared, and the preparation method of the coating powder of the present invention is as follows:
- the infiltrating material of the present invention is an RT alloy or an intermetallic compound in which R is a rare earth element and T is a transition metal element and other metal elements.
- the RT alloy or the intermetallic compound has one or more crystal structures of MgCu 2 , PuNi 3 , Th 2 Zh 17 or Th 2 Ni 17 .
- the content of the rare earth element R is not less than 50% by weight of the total weight, and the content of Dy+Tb (the sum of the contents of Dy and Tb) is not less than 10% by weight of the total weight;
- the balance T is Fe a transition metal element such as Co, Ni, Ti, V, Cr, Zr, Nb, Mo or W, and one or more metal elements such as Ga, Cu, Zn or Sn, and a content of Fe and Co And not more than 45 wt% of the total weight.
- the prepared material is placed in a vacuum medium frequency induction furnace for melting, and cast into a plate-shaped steel ingot having a thickness of 0.6 to 20 mm, the steel ingot having an oxygen content of not more than 300 ppm; or a strip casting.
- the prepared material is placed in a vacuum medium frequency induction furnace for melting, and the crucible is obtained to obtain a sheet having a thickness of 0.1 to 0.6 mm, and the sheet has an oxygen content of not more than 200 ppm.
- Preparing a coating solution preparing the osmotic material powder and the alcohol in a weight ratio of not less than 0.5:1, and adding a dispersing agent to the liquid, the amount of the dispersing agent being 0 to 1% by volume of the alcohol to be mixed, With sufficient agitation, the alcohol is preferably completely volatile and has no residue at temperatures below 800-1000 °C.
- Blank cleaning The surface of the previously prepared blank magnet is cleaned before being coated, and pickled with nitric acid having a volume concentration of less than 5%, and then rinsed with pure water to remove residual acid.
- the cleaned blank magnet is cleaned with inert gas. Stored under the protection.
- the coating process of the present invention is to soak and stir the green magnet in the coating solution, the immersion time is at least one minute, and the blank magnet after the immersion coating is put into the sealed sealed box.
- the material of the material box is iron such as stainless steel, 45 steel, etc., Ta, W, Mo and other heat-resistant metal materials; or graphite material.
- Heat treatment The permeate material coated on the surface of the blank magnet is infiltrated into the billet magnet by heat treatment to improve the boundary characteristics of the grain boundaries and their interaction with the main phase grains.
- the grain boundary diffusion treatment process of the present invention uses a secondary heat treatment process:
- the cartridge containing the soaked coated magnet is placed in a vacuum sintering furnace and evacuated.
- the degree of vacuum reaches 10 -2 Pa
- the temperature is raised to 820 to 1050 ° C and held for 1 to 8 hours, followed by argon charging.
- the gas is cooled to below 100 ° C;
- the aforementioned blank magnet obtained without the tempering treatment step is subjected to two heat treatment processes directly under a vacuum (with a minimum degree of vacuum of 5*10 -1 Pa) or a gas-protected atmosphere without being subjected to a permeation material coating process:
- the first tempering is to raise the temperature inside the vacuum to 820 ° C ⁇ 1050 ° C, keep warm for 1 ⁇ 8 hours, and then fill with argon gas to lower the temperature inside the sintering furnace to below 100 ° C;
- the second tempering is to raise the temperature inside the vacuum furnace to 450 ° C to 620 ° C, and keep the temperature for 1 to 5 hours, and then fill the sintering furnace with argon gas to lower the temperature in the sintering furnace to below 80 ° C.
- the magnet obtained by the grain boundary diffusion treatment process of the present invention that is, the magnet obtained by the heat treatment of the blank magnet after being coated with the permeable material and the blank magnet are directly subjected to heat treatment (hereinafter referred to as conventional heat treatment) without being coated with the permeable material.
- the obtained magnets have the following characteristics:
- the density of the magnet obtained by the grain boundary diffusion treatment process of the present invention is not more than 0.13% as measured at 20 ° C as compared with the density of the magnet obtained by conventional heat treatment.
- the rate of change is: the absolute value of (density of the invention / density conventional -1). Density measurements are measured using the drainage method.
- the change is: (Curie temperature of the present invention - Curie temperature routine ) absolute value.
- Curie temperature measurement Using a vibrating sample magnetometer, the magnetization as a function of temperature (MT curve) was measured at an applied magnetic field of 300 Oe to determine the Curie temperature T c of the magnet.
- the intrinsic coercive force H cj of the magnet obtained by the grain boundary diffusion treatment process of the present invention is increased by at least 1.0 kOe to 5.0 as measured at 20 ° C compared with the intrinsic coercive force H cj of the magnet obtained by conventional heat treatment. kOe, or increase by at least 1.0 kOe, 3.0 kOe, or 5.0 kOe.
- the remanence B r of the magnet obtained by the grain boundary diffusion treatment process of the present invention is measured at 20 ° C compared with the remanence B r of the magnet obtained by the conventional heat treatment, and is reduced by not more than 0.2 kGs to 0.5 kGs, or decreased by not more than 0.5 kGs, 0.3 kGs or 0.2 kGs.
- the maximum magnetic energy product (BH) max of the magnet obtained by the grain boundary diffusion treatment process of the present invention is measured at 20 ° C, and is reduced by not more than 1.5 MGOe to 3.5 as compared with the maximum magnetic energy product (BH) max of the magnet obtained by conventional heat treatment. MGOe, or reduce no more than 3.5MGOe, 2.0MGOe or 1.5MGOe.
- the intrinsic coercive force H cj , the remanence B r , and the maximum magnetic energy product (BH) max are obtained by measuring the BH demagnetization curve of the magnet.
- the size of the sample was measured to be 10 mm in diameter and 10 mm in height, and the height direction of the sample was perpendicular to the orientation direction, and the BH demagnetization curve of the sample was measured at a temperature of 20 °C.
- the magnet obtained by the grain boundary diffusion treatment process of the present invention has an absolute value of the change of the temperature coefficient of the remanence B r of ⁇ 0.011 between 20 ° C and 120 ° C.
- Absolute value of the variation of the temperature coefficient of the remanence of the present invention ( B r - the absolute value of the temperature coefficient of the remanence B r conventional) is.
- the magnet obtained by the grain boundary diffusion treatment process of the present invention has an absolute value of the change of the temperature coefficient of the intrinsic coercive force H cj ⁇ 0.100 between 20 ° C and 120 ° C. It is the absolute value of said variation :( intrinsic coercive force H cj temperature coefficient of the present invention - the intrinsic coercive force H cj conventional temperature coefficient) of the absolute values.
- Method for measuring the temperature coefficient of remanence and coercivity first measure the BH curve of the magnet at 20 ° C, and obtain the values of B r (T 0 ) and H cj (T 0 ), and then measure the magnet at 120 ° C.
- B r (T) and H cj (T) are calculated using the following formula to obtain the temperature coefficient of remanence and coercivity;
- the absolute value of the weight loss of the cylindrical magnet having a diameter of 10 mm and a height of 10 mm is not more than 2.5 mg. /cm 2 to 3.5 mg/cm 2 , or not more than 3.5 mg/cm 2 or 2.5 mg/cm 2 .
- the weight loss of the cylindrical magnet having a diameter of 10 mm and a height of 10 mm does not include the coating of the permeable material.
- Process for Preparing Process The absolute value of the change in weight loss measured by the magnet prepared under the same conditions described above is not more than 0.2 mg/cm 2 .
- the specific test conditions were as follows: The sample was allowed to stand at 130 ° C, 2.6 atmospheres, 95% relative humidity for 240 hours.
- the main phase of the magnet obtained by the grain boundary diffusion treatment process of the present invention is the same as the main phase of the magnet obtained by the non-permeable material coating process, and is a crystal structure of Nd 2 Fe 14 B; the lattice constant measured at 20 ° C
- the rate of change of a, c is not more than 0.11%.
- the calculation formula of the rate of change (lattice constant of the present invention / lattice constant conventional - 1) absolute value.
- X-ray powder diffraction can be used to determine the main phase crystal structure type, lattice constant value of the magnet and to detect the type and composition of the crystal structure in the coating material (permeate material).
- the sintered NdFeB billet magnet without tempering is processed into a magnetic piece having a size of ⁇ 10*3 mm, and the magnetic piece is subjected to conventional degreasing and pickling in a 5% (volume%) concentration of nitric acid, and is carried out. Ultrasonic cleaning and drying, the magnetic sheet is stored under the protection of an inert gas.
- the raw materials are compounded according to the following weight ratio: Nd: 15wt%, Pr: 12wt%, Dy: 30wt%, Fe: 42wt%, Cu: 1wt%; put the prepared raw materials into the vacuum medium frequency induction
- the furnace is smelted and cast, the thickness of the alloy ingot cast is about 10 mm, and the oxygen content of the alloy ingot is 200 ppm;
- the alloy ingot was subjected to hydrogenation and crushing in a hydrogenation furnace, and only hydrogen absorption was carried out without dehydrogenation treatment, and the hydrogenated crushed alloy was simply mechanically crushed to have an average particle size of 0.5 mm and a hydrogen content of 2453 ppm.
- the hydrogenated crushed powder was made into a fine powder having an average particle size of 5.0 ⁇ m in a jet mill using an inert gas as a working gas, and the obtained fine powder was stored under the protection of an inert gas.
- the above fine powder and alcohol are formulated into a coating solution in a weight ratio of 0.6:1, no dispersing agent is added to the solution, and Stir well.
- the washed blank magnet was completely immersed in the coating solution and immersed, and immersed for 1.5 minutes.
- the immersed magnet was placed in a metal box, which was made of iron, stainless steel and sealed.
- the cartridge containing the coated blank magnet was placed in a vacuum furnace for secondary heat treatment.
- vacuum is applied.
- the vacuum reaches 10 -2 Pa or more, the temperature is raised to 1000 ° C and the holding time is 3 hours.
- the heating is stopped and the argon gas is cooled to below 100 ° C.
- the vacuum is applied to 10 -2 Pa and then heated to 470 ° C.
- the temperature was kept for 3 hours; the heating was stopped, and then Ar gas was charged into the sintering furnace, and the sintering furnace was cooled to below 80 ° C to obtain a final magnet.
- the magnetic sheet of ⁇ 10*3 mm processed by the blank magnet in Example 1 is not subjected to the coating treatment of the infiltrated material, and the secondary heat treatment is directly performed.
- the heat treatment temperature and the holding time are also the first holding time at 1000 ° C for 3 hours, followed by The temperature was maintained at 470 ° C for 3 hours, and the heat treatment was carried out under vacuum.
- the magnet obtained by the grain boundary diffusion treatment process of the present invention which is obtained by the grain boundary diffusion treatment process of the present invention, that is, the magnet obtained by heat-treating the blank magnet after being coated with the permeable material and the blank magnet is directly subjected to heat treatment without being coated with the permeable material. Compare.
- the magnet obtained by the infiltration treatment (treated sample) and the magnet obtained without the infiltration treatment (untreated sample) were measured for demagnetization curve at 20 ° C, and the results were as follows:
- the maximum magnetic energy product (BH) max of the magnet obtained in Example 1 was decreased by 1.1 MGOe as compared with the maximum magnetic energy product (BH) max of the magnet obtained in Comparative Example 1.
- Example 1 H cj magnets obtained as compared with Comparative Example 1 obtained magnet H cj, H cj improved 3.9kOe.
- Example 1 The Curie temperature of Example 1 was 318 ° C, and the comparative example 1 was 315 ° C, and the Curie temperature of the two was 3 ° C.
- the weight loss of the magnet of Example 1 and Comparative Example 1 was -3.1 mg/cm 2 .
- the absolute value of the change between the two is 0.0 mg/cm 2 .
- Example 1 The density of Example 1 was 7.53, the density of Comparative Example 1 was 7.52, and the rate of change of density between the two was 0.13%.
- X-ray powder diffraction results indicate that the intermetallic compound of the infiltrated material mainly has a PuNi 3 and MgCu 2 crystal structure.
- the sintered NdFeB billet magnet after sintering but not tempered is processed into a magnetic piece having a size of ⁇ 10 mm*10 mm, and the magnetic piece is subjected to conventional degreasing and pickling in 4% nitric acid and ultrasonic wave. It is washed and dried, and the magnetic sheet is stored under the protection of an inert gas.
- a powder of osmotic material to be coated which is prepared by the following process, and the raw materials are compounded in the following weight ratios: Dy: 60% by weight, Co: 40% by weight;
- the vacuum medium frequency induction furnace was smelted, and a sheet having an average thickness of 0.3 mm was prepared by a rapid setting sheet process, and the oxygen content was 60 ppm.
- Hydrogenation was carried out in a hydrogenation furnace, and only hydrogen absorption was carried out without dehydrogenation treatment, and the hydrogenation-crushed quick-condensation flakes were simply mechanically crushed to have an average particle size of 1.0 mm and a hydrogen content of 2000 ppm.
- the hydrogenated crushed powder is made into a fine powder having an average particle size of 3 ⁇ m.
- the resulting fine powder is stored under the protection of an inert gas.
- the above fine powder and alcohol were formulated into a coating solution in a weight ratio of 0.5:1, 0.2% of a dispersing agent was added to the solution, and the mixture was thoroughly stirred.
- the cleaned blank magnet is completely immersed in the coating solution and immersed, and immersed for one minute.
- the immersed magnet is placed in a metal box and sealed, and the material of the material is Ta.
- the cartridge containing the coated blank magnet was placed in a vacuum furnace for secondary heat treatment.
- vacuum is applied.
- the vacuum reaches 10 -2 Pa or more, the temperature is raised to 1050 ° C and the holding time is 1 hour.
- the argon gas is cooled to below 100 ° C.
- the vacuum is applied to 10 -2 Pa, heated to 450 ° C, and kept for 5 hours.
- the sintering furnace was charged with Ar gas, and the sintering furnace was cooled to below 80 ° C to obtain a final magnet.
- the ⁇ 10mm*10mm magnetic sheet processed by the blank magnet in Example 2 is subjected to the second heat treatment without the permeation treatment, and the heat treatment temperature and the holding time are also the first holding time at 1050 ° C for 1 hour, followed by 450.
- the temperature was kept at ° C for 5 hours, and the heat treatment was carried out under the protection of an inert gas.
- the magnetic parameter measurements of the magnet obtained by the infiltration treatment (treated sample) and the magnet obtained without the infiltration treatment (untreated sample) are as follows:
- Example 2 obtained in the process remanence B r of the magnet and the remanence B r compared to Comparative Example 2 obtained magnet, reducing 0.1kGs at 20 °C.
- the maximum magnetic energy product (BH) max of the magnet obtained in the process of Example 2 was decreased by 0.8 MGOe as compared with the maximum magnetic energy product (BH) max of the magnet obtained in Comparative Example 2.
- H cj magnets obtained in Example 2 compared to the process of Comparative Example 2 obtained magnet H cj, H cj up 5.3kOe.
- Example 2 the absolute value of the change in the temperature coefficient of remanence B r was 0.010, and the absolute value of the change in the temperature coefficient of the intrinsic coercive force H cj was 0.068.
- Example 2 Example 2 of the magnet and the magnet weightlessness of the present embodiment respectively -2.5mg / cm 2, -2.4mg / cm 2. The absolute value of the change between the two is 0.1 mg/cm 2 .
- the density was measured by the drainage method.
- the density of the present Example 2 was 7.52, and the comparative example 2 was 7.51, and the rate of change was 0.13%.
- the intermetallic compound of the permeation material of Example 2 was mainly a MgCu 2 phase and a small amount of a Th 2 Ni 17 phase.
- the osmotic material of Example 2 mainly has a MgCu 2 crystal structure and a small amount of Th 2 Ni 17 crystal structure.
- Examples 3 to 15 were subjected to the same coating and heat treatment process steps as in Examples 1 and 2, and the obtained magnets were subjected to parameter measurement by the same measurement methods as in Examples 1 and 2.
- the billet magnet was subjected to secondary heat treatment at the same heat treatment temperature and time for each of the examples to obtain a comparative magnet, and the magnet parameters were measured using the same method.
- Table 1 shows the composition parameters of the osmotic material alloy and the coating solution in Examples 1-15.
- Table 2 shows the coating and heat treatment process parameters in Examples 1-15.
- Table 3 shows the performance parameters and comparisons of the magnets prepared in Examples and Comparative Examples 1-15 and the corresponding comparative examples.
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Abstract
一种稀土永磁体的制备方法,其包括:不包括回火处理步骤的毛坯磁体制备工序、渗透材料涂覆工序及热处理工序。不包括回火处理步骤的毛坯磁体制备工序是指经过配料-合金熔炼-粉碎制粉-成型-烧结工序制成毛坯磁体。渗透材料涂覆工序包括渗透材料粉末的制备、将渗透材料粉末制备成涂覆溶液、及在涂覆溶液中对毛坯磁体进行涂覆等工序。本发明采用稀土金属间化合物作为扩散材料,其相和成份比较稳定,且易于破碎;稀土金属间化合物的成相元素范围宽,可以根据磁体性能需要调整形成稀土金属间化合物的成份。发明可以改善晶界的边界特征及其与主相晶粒的相互作用,提高烧结钕铁硼磁体的内禀矫顽力,而剩磁和最大磁能积减小量很少。
Description
本发明涉及一种稀土永磁体的制备方法,特别是一种可以提高烧结钕铁硼磁体内禀矫顽力Hcj的制造方法,尤其指提高烧结钕铁硼磁体半成品内禀矫顽力的方法。
稀土永磁材料是以不同的稀土元素和过渡族金属元素(Fe,Co,Ni等)组成的金属间化合物为主相的永磁材料。自1960年代被发明以来,稀土永磁材料的发展十分迅速,已经在许多领域里得到了广泛的应用,成为当代新技术的重要基础功能材料,特别是在永磁电机领域发挥了不可替代的作用。如今稀土永磁电机已经覆盖了步进电机、无刷电机、伺服电机和直线电机等主要类型,并广泛应用于计算机、打印机、家用电器、空调压缩机、汽车助力转向电机、混合动力或纯电动汽车驱动电机/发电机、汽车启动电机、地面军用电机、航空电机等重要领域。
以铁为基本成分、具有高矫顽力和高磁能积的高性能烧结钕铁硼磁体,是近三十年来得到迅速发展的一种稀土永磁材料。钕铁硼稀土永磁材料应用于各种电机,可以明显提高电机的性能,减轻电机重量,减小电机外型尺寸,且可以获得高效的节能效果。例如,10kW普通永磁发电机采用铁氧体,发电机重量为220kg;而相同功率的稀土永磁发电机重量仅为92kg。稀土永磁电机的平均节电率高达10%,某些专用电机节电率甚至高达15%-20%,如德国西门子研制的1095kW、230rpm六极永磁同步电动机,与过去使用的直流电动机相比,体积减少60%左右,总损耗降低20%。钕铁硼的高性能价格比也使其成为制造效能高、体积小、重量轻的磁性功能器件的理想材料。除了在计算机、打印机、移动电话、家用电器、医疗器械等方面的广泛应用外,汽车中的发电机、电动机和音响系统的应用也已经日趋成熟,这将极大地拉动钕铁硼产业的发展,各种用途的新型稀土永磁电机将进入了一个崭新的发展阶段。目前,稀土永磁电机已经成为钕铁硼磁体最大的应用领域,约占磁体总产量的70%。
目前,烧结钕铁硼最大磁能积的实验室水平已经非常接近理论极限值,约为93%。但其内禀矫顽力则远远低于理论极限值,即使采用非常极端的手段也不过25%左右,而高内禀矫顽力是上述新应用的最基本要求。如何充分发挥钕铁硼主相的内在特性,提高烧结钕铁硼的内禀矫顽力,是当前热点研究的问题。在熔炼过程中加入镝Dy和或铽Tb等重稀土
元素,使其部分置换磁体中的钕Nd以提高烧结NdFeB磁体的矫顽力,是一种众所周知的有效方法。因为Dy2Fe14B或Td2Fe14B具有比Nd2Fe14B更高的磁晶各向异性场,也就是有可能获得更大的内禀矫顽力,Dy或Tb部分取代主相Nd2Fe14B中的Nd后生成的(Nd,Dy)2Fe14B或(Nd,Tb)2Fe14B的磁晶各向异性场比Nd2Fe14B大,因而可以明显提高烧结磁体的矫顽力。但是,这种元素取代带来的不利后果,就是显著降低磁体的饱和磁化强度,因此磁体的剩磁Br和最大磁能积(BH)max都会明显降低,因为在(Nd,Dy)2Fe14B或(Nd,Tb)2Fe14B主相中Nd与Fe的磁矩同向平行排列,两者的磁矩是增强性叠加;而Dy和Tb的磁矩与Fe磁矩反向平行排列,部分抵消主相的总磁矩。另外,相对于Nd而言含Dy和Tb的稀土矿储量稀少且分布很不均匀,Dy和Tb单价远高于Nd,这种取代会造成磁体成本的增加。近期,一些新的工艺被用来提高烧结钕铁硼磁体的内禀矫顽力,如CN101845637A专利中所提到的,采用将磁体浸泡于重稀土Dy或Tb的氧化物或氟化物的酸性溶剂中一定时间,在Ar气保护下进行热处理,可以提高Hcj值。在CN101517670A的专利申请中,用含Dy或Tb的金属粉末,其金属粉末中含有Ni或Co,且实施例中每种粉末必须含有B,而且必须有三个步骤:先将磁体表面涂覆粘接层,再将附有粘接层的磁体在金属粉末中搅拌或冲击以吸附金属粉末,最后进行热扩散处理,依靠此种方法来提高Hcj。
以上方法可以在一定程度上提高Hcj,且其粉末和磁体的表面状态会非常敏感地影响到Hcj的提升效果,但以上专利等都没有对磁体的状态及粉末的制备提出具体要求。众所周知,如果靠扩散法来使Dy或Tb的化合物扩散到磁体中,对粉末的活性及表面状态没有特别要求的话,是非常难保证重稀土可以扩散到磁体中,且也难以保证扩散过程的可重复性及工艺稳定性,难以工业化制备确实稳定提高Hcj的磁体。
发明内容
理论上纯Nd2Fe14B金属间化合物的最大磁能积为64MGOe,而实际情况下为了获得高的内禀矫顽力Hcj,在具有Nd2Fe14B晶体结构的主相晶粒边界上必须有富稀土相的存在,并且工艺过程还会导致磁体与理想状况偏离的各种因素,如孔隙、杂质、晶粒取向度等。通过对烧结磁体工艺广泛研究,认为烧结Nd-Fe-B磁体的最大磁能积正比于磁体剩磁Br的平方,而下列关系式可以表述Br与各影响因素的关系:
Br=(Is·β)·(ρ/ρ0)·(1-α)·f
其中Is=4πMs为主相的饱和磁极化强度,β为Is的温度影响因子,ρ/ρ0为相对密度,α为非磁性相的体积百分比,f为取向度因子。
NdFeB烧结磁体的内禀矫顽力Hcj表示如下:
Hcj=CHa-NIs
其中Ha为主相的磁晶各向异性场,C取决于主相晶粒与其界面晶粒之间的相互作用,N是有效退磁因子,C和N敏感地依赖于烧结磁体的晶粒尺寸及其分布,以及相邻晶粒间的取向特征和边界特征。
按目前的工艺,一般磁体在调整配方和工艺路线后,磁体的Br和Hcj基本就确定了。根据烧结钕铁硼Hcj的以上关系式,内禀矫顽力Hcj除了依赖于主相的磁晶各向异性场Ha,还依赖于主相晶粒与其界面晶粒之间的相互作用,以及相邻晶粒间的边界特征。
本发明的目的就是通过晶界扩散法,通过改善晶界的边界特征及其与主相晶粒的相互作用,同时提高主相晶粒表面层的磁晶各向异性场,进而提高烧结钕铁硼磁体的内禀矫顽力Hcj,而对剩磁Br和最大磁能积(BH)max影响很小。
本发明的一种稀土永磁体的制备方法,其特征在于,所述方法包括:不包括回火处理步骤的毛坯磁体制备工序、渗透材料涂覆工序及热处理工序。
本发明所述的不包括回火处理步骤的毛坯磁体制备工序是指经过配料-合金熔炼-粉碎制粉-成型-烧结工序制成毛坯磁体。
本发明所述的渗透材料涂覆工序包括渗透材料粉末的制备、将渗透材料粉末制备成涂覆溶液、及在涂覆溶液中对毛坯磁体进行涂覆等工序。
本发明所述的渗透材料粉末的制备工序包括:
(1)按比例进行配料;
(2)熔炼合金;
(3)将上述合金进行中破碎;
(4)将上述中破碎后的粉末进行细粉碎。
本发明所述的热处理工序为二次热处理,所述二次热处理包括:
(1)将被浸泡涂覆后的毛坯磁体放入料盒后送入真空烧结炉中抽真空,在真空度达到10-2Pa时升温到820~1050℃并保温1~8小时,然后充氩气冷却到100℃以下;
(2)停止冷却并抽真空到10-2Pa,再开始加热到450℃~620℃,保温1~5小时后停止加热;然后向烧结炉充入Ar气,使烧结炉冷却到80℃以下。
本发明采用稀土金属间化合物作为晶界扩散的材料,其优点在于:稀土金属间化合物的相和成份比较稳定,且易于破碎,容易将其制备成微粉;稀土金属间化合物的成相元素范围宽,可以根据磁体性能需要调整形成稀土金属间化合物的成份。通过本发明的晶界扩
散渗透法,可以改善晶界的边界特征及其与主相晶粒的相互作用,提高烧结钕铁硼磁体的内禀矫顽力Hcj,而剩磁Br和最大磁能积(BH)max所受影响很小,减小量很少。本发明是在基本保持磁体的剩磁和最大磁能积、并使用极少量重稀土Dy和或Tb的前提下,即可显著提高磁体Hcj的一种工艺。
首先按照常规工序但不包括回火处理步骤制备烧结钕铁硼毛坯磁体,即经过配料-合金熔炼-粉碎制粉-成型-烧结工序制备出毛坯磁体,该磁体只经过烧结但未经过回火处理(也可称做回火热处理)。本发明钕铁硼毛坯磁体为烧结后未经过回火处理的磁体,所述磁体的氧含量小于等于4000ppm,磁体取向方向的厚度小于等于10mm。
随后制备渗透材料粉末,或称为涂覆粉末,本发明涂覆粉末的制备方法如下:
(1)按比例进行配料:本发明的渗透材料为R-T合金或金属间化合物,其中R为稀土元素,T为过渡族金属元素和其他金属元素。该R-T合金或金属间化合物具有MgCu2、PuNi3、Th2Zh17或Th2Ni17晶体结构的一种或一种以上。配料成份:稀土元素R的含量不低于总重量的50wt%(重量百分比),且Dy+Tb的含量(Dy与Tb的含量之和)不低于总重量的10wt%;余量T为Fe、Co、Ni、Ti、V、Cr、Zr、Nb、Mo或W等过渡族金属元素以及Ga、Cu、Zn或Sn等金属元素中的一种或一种以上,且Fe与Co的含量之和不大于总重量的45wt%。
(2)随后将配好的料放入真空中频感应炉中进行熔炼,并浇铸得到厚度为0.6~20mm的板状钢锭,所述钢锭氧含量不大于300ppm;或采用速凝薄片(strip casting)工艺,将配好的料放入真空中频感应炉中进行熔炼后,甩带得到厚度为0.1~0.6mm的薄片,所述薄片的氧含量不大于200ppm。
(3)将上述钢锭或薄片采用氢化工艺进行中破碎粉,且氢化过程只进行吸氢破碎后,粉末的平均粒度为0.5mm~1.0mm,氢含量≥在2000ppm;
(4)将上述中破碎后的粉末在采用惰性气体保护的气流磨中破碎成为平均粒度2~6微米的微粉;
(5)将上述微粉在惰性气体保护下进行储存。
制备涂覆溶液:将渗透材料粉末与醇类按不低于0.5:1的重量比配制,可以在液体中添加分散剂,分散剂的量为所配醇类的体积百分比0~1%,,并充分搅拌,所述醇类优选为在温度低于800~1000℃时可以完全挥发且没有残余。
毛坯清洗:将前述制备的毛坯磁体在进行涂覆前进行表面清洗,并使用体积浓度小于5%的硝酸进行酸洗,再用纯水漂洗去除残余酸液,清洗洁净的毛坯磁体要在惰性气体的保护下存放。
涂覆:本发明的涂覆工序为将所述毛坯磁体在涂覆溶液中浸泡并进行搅拌,浸入时间至少大于一分钟,将浸泡涂覆完成后的毛坯磁体放入加盖的密闭料盒中。料盒的材质为铁质如不锈钢,45号钢等,Ta,W,Mo等耐热金属材质;或者为石墨材质。
热处理:通过热处理将涂覆在毛坯磁体表面的渗透材料渗透进毛坯磁体中,以改善晶界的边界特征及其与主相晶粒的相互作用。本发明晶界扩散处理工艺采用二次热处理工艺:
(1)将装有被浸泡涂覆的毛坯磁体的料盒放入真空烧结炉中抽真空,在真空度达到10-2Pa时升温到820~1050℃并保温1~8小时,然后充氩气冷却到100℃以下;
(2)停止冷却并抽真空到10-2Pa,再开始加热到450℃~620℃,保温1~5小时后停止加热;随即向烧结炉充入Ar气,使烧结炉冷却到80℃以下。
作为参照对比,将前述未经过回火处理步骤获得的毛坯磁体不经过渗透材料涂覆工序处理直接在真空(真空度最低5*10-1Pa)或气体保护气氛下进行两次热处理工艺:
(1)第一次回火为将真空烧内温度升至820℃~1050℃,保温1~8小时,随后充入氩气使烧结炉内温度下降到100℃以下;
(2)第二次回火为将真空烧内温度升至450℃~620℃,保温1~5小时,然后向烧结炉内充入氩气,使烧结炉内温度下降到80℃以下。
通过比较采用本发明的晶界扩散处理工艺所获得磁体,即毛坯磁体经渗透材料涂覆后再进行热处理所获得的磁体与毛坯磁体未经渗透材料涂覆而直接进行热处理(以下称常规热处理)所获得的磁体相比较具有如下特点:
采用本发明的晶界扩散处理工艺所获得磁体的密度与常规热处理所获磁体的密度相比,在20℃下测量,密度的变化率不大于0.13%。所述变化率为:(密度本发明/密度常规-1)的绝对值。密度测量采用排水法测量。
采用本发明的晶界扩散处理工艺所获得磁体的居里温度Tc与常规热处理所获磁体的居里温度Tc相比,在20℃下测量,居里温度的变化不大于3℃至4℃,或不大于3℃或4℃。所述变化为:(居里温度本发明-居里温度常规)的绝对值。居里温度测量采用振动样品磁强计,在300奥斯特(Oe)的外加磁场下测量磁化强度随温度的变化曲线(M-T曲线),以确定所述磁体的居里温度Tc。
采用本发明的晶界扩散处理工艺所获得磁体的内禀矫顽力Hcj与常规热处理所获磁体的内禀矫顽力Hcj相比,在20℃下测量,增大至少1.0kOe~5.0kOe,或增大至少1.0kOe、3.0kOe、或5.0kOe。
采用本发明的晶界扩散处理工艺所获得磁体的剩磁Br与常规热处理所获磁体的剩磁Br相比,在20℃下测量,降低不大于0.2kGs至0.5kGs,或降低不大于0.5kGs、0.3kGs或0.2kGs。
采用本发明的晶界扩散处理工艺所获得磁体的最大磁能积(BH)max与常规热处理所获磁体的最大磁能积(BH)max相比,在20℃下测量,降低不大于1.5MGOe至3.5MGOe,或降低不大于3.5MGOe、2.0MGOe或1.5MGOe。
内禀矫顽力Hcj、剩磁Br、最大磁能积(BH)max通过测量磁体的B-H退磁曲线获得。测量样品的尺寸为直径10mm高10mm,样品的高度方向垂直于取向方向,在温度20℃下测量样品的B-H退磁曲线。
采用本发明的晶界扩散处理工艺所获得磁体与常规热处理所获磁体相比,在20℃~120℃温度之间,其剩磁Br的温度系数变化的绝对值≤0.011。所述变化的绝对值为:(剩磁Br的温度系数本发明-剩磁Br的温度系数常规)的绝对值。
采用本发明的晶界扩散处理工艺所获得磁体与常规热处理所获磁体相比,在20℃~120℃温度之间,其内禀矫顽力Hcj的温度系数变化的绝对值≤0.100,所述变化的绝对值为:(内禀矫顽力Hcj的温度系数本发明-内禀矫顽力Hcj的温度系数常规)的绝对值。
剩磁及矫顽力的温度系数的测量方法:首先在20℃下测量磁体的B-H曲线,得到Br(T0)及Hcj(T0)的值,然后再测出120℃下磁体的Br(T)及Hcj(T),使用如下公式进行计算,得到剩磁及矫顽力的温度系数;
采用本发明的晶界扩散处理工艺所获得磁体在130℃环境温度,95%相对湿度,2.6大气压下放置240小时后,直径10mm高10mm的所述圆柱形磁体的失重的绝对值不大于2.5mg/cm2至3.5mg/cm2,或不大于3.5mg/cm2或2.5mg/cm2。
采用本发明的晶界扩散处理工艺所获得磁体在130℃环境温度,95%相对湿度,2.6大
气压下放置240小时后,直径10mm高10mm的所述圆柱形磁体的失重与不包括渗透材料涂覆工序的制备方法所制备磁体在上述相同条件下测量的失重变化的绝对值不大于0.2mg/cm2。
失重的测定公式为:失重(mg/cm2)=(A1-A0)/S0;其中:A0为样品测试前的重量,S0为样品测试前的表面积,A1为样品经测试后冷却至室温后的重量。具体测试条件为:将样品在130℃,2.6个大气压,95%相对湿度条件下放置240小时。
采用本发明的晶界扩散处理工艺所获得磁体的主相与未经渗透材料涂覆工序所获磁体的主相相同,为Nd2Fe14B晶体结构;在20℃下测量,其晶格常数a,c的变化率不大于0.11%。其变化率的计算公式=(晶格常数本发明/晶格常数常规-1)的绝对值。
可采用X射线粉末衍射法来确定磁体的主相晶体结构类型、晶格常数数值并检测涂覆材料(渗透材料)中晶体结构的种类和组成。
上述表述中采用本发明工艺获得的磁体的各种数据值,如“晶格常数本发明”在下面各实施例中等同于“晶格常数实施例”,在常规热处理工艺下获得磁体的各种数据值,如“晶格常数常规”在下面各实施例中等同于“晶格常数对比例”。此说明适用于所有测量得到的数据。
下面结合本发明的具体实施例详细说明。
实施例1:
首先将没有经过回火处理的烧结钕铁硼毛坯磁体加工成尺寸为Φ10*3mm的磁片,将磁片经过常规除油及在5%(体积百分比)浓度的硝酸中进行酸洗,并进行超声波清洗并吹干,此磁片在惰性气体的保护下进行贮存。
准备将要进行涂覆的渗透材料粉末,该粉末按照下面的工序进行准备:
按下列重量比将原材料进行配料,配料的成份范围为:Nd:15wt%、Pr:12wt%、Dy:30wt%、Fe:42wt%、Cu:1wt%;将配好的原料放入真空中频感应炉进行熔炼和浇铸,其浇铸的合金锭的厚度在10mm左右,合金锭氧含量为200ppm;
在氢化炉中将合金锭进行氢化破碎,只吸氢不进行脱氢处理,氢化破碎的合金经简单的机械破碎,使粉末平均粒度为0.5mm,氢含量为2453ppm。
在以惰性气体为工作气体的气流磨中,将氢化破碎粉制成平均粒度为5.0微米的微粉,所得微粉在惰性气体的保护下进行储存。
将上述微粉与酒精按0.6:1的重量比配制成涂覆溶液,在溶液中没有添加分散剂,并
充分搅拌。
将经过清洗的毛坯磁体完全浸入涂覆溶液中浸泡并进行搅拌,浸入时间1.5分钟,将浸入完成后的磁体放入金属料盒,金属料盒为铁质,为不锈钢并加盖密封。
将装有涂覆处理后毛坯磁体的料盒放入真空炉中进行二次热处理。首先抽真空,在真空度达到10-2Pa以上时升温到1000℃并保温时间3小时,停止加热并充氩气冷却到100℃以下;然后抽真空到10-2Pa,再加热到470℃保温3小时;停止加热,随后向烧结炉充入Ar气,使烧结炉冷却到80℃以下,获得最终磁体。
对比例1:
作为对比,将实施例1中毛坯磁体加工后的Φ10*3mm的磁片未经渗透材料涂覆处理,直接进行二次热处理,热处理温度和保温时间同样为首先在1000℃保温时间3小时,其次470℃保温3小时,热处理在真空情况下进行。
将实施例1采用本发明晶界扩散处理工艺所获得的磁体,即毛坯磁体经渗透材料涂覆后再进行热处理所获得的磁体与毛坯磁体未经渗透材料涂覆而直接进行热处理所获得的磁体进行比较。
经过渗透处理获得的磁体(处理样品)与未进行渗透处理获得的磁体(未处理样品)在20℃下测量退磁曲线,结果如下:
样品 | Br(kGs) | Hcj(kOe) | (BH)max(MGOe) |
实施例1(处理样品) | 12.9 | 19.5 | 40.3 |
对比例1(未处理样品) | 13.1 | 15.6 | 41.4 |
由上表可知,实施例1所获得磁体的剩磁Br与对比例1所获磁体的剩磁Br相比,降低0.2kGs。
实施例1所获得磁体的最大磁能积(BH)max与对比例1所获磁体的最大磁能积(BH)max相比,下降1.1MGOe。
实施例1所获得磁体的Hcj与对比例1所获磁体的Hcj相比,Hcj提高了3.9kOe。
实施例1和对比例1样品的其他测量结果如下:
实施例1的居里温度为318℃,对比例1为315℃,两者居里温度相差为3℃。
在20℃下测量对比例1磁体样品的B-H曲线,得到Br(T0)=13.1kGs及Hcj(T0)=15.6kOe的值,然后再测出对比例1磁体样品120℃下磁体的Br(T)=11.5kGs及Hcj(T)=4.0kOe,使
用如下公式进行计算得到对比例1剩磁及矫顽力的温度系数:αBr=-0.122%/℃,βHcj=-0.744%/℃
实施例1温度系数的测定采用同样的方法,其结果为:αBr=-0.113%/℃,βHcj=-0.653%/℃。
实施例1与对比例1剩磁Br的温度系数变化的绝对值为0.009,内禀矫顽力Hcj的温度系数变化的绝对值为0.091。
实施例1磁体与对比例1磁体的失重均为-3.1mg/cm2。两者变化的绝对值为0.0mg/cm2。
本实施例1的密度为7.53,对比例1的密度为7.52,两者密度的变化率为0.13%。
X射线粉末衍射结果表明,实施例1所获得磁体的主相与未经渗透材料涂覆工序的对比例1所获磁体的主相相同,均为Nd2Fe14B晶体结构;对比例1晶格常数a=0.8788nm,c=1.2165nm;实施例1晶格常数a=0.8785nm,c=1.2163nm。根据公式,二者晶格常数a的变化率为0.03%,c的变化率为0.02%。
X射线粉末衍射结果表明,渗透材料的金属间化合物主要具有PuNi3和MgCu2晶体结构。
上述未经说明的数据均在20℃下测量得到。此说明适用于所有实施例。
实施例2:
首先将烧结后但没有经过回火处理的烧结钕铁硼毛坯磁体加工成尺寸为Φ10mm*10mm的磁片,将磁片经过常规的除油及在4%浓度的硝酸中进行酸洗并进行超声波清洗并吹干,此磁片在惰性气体的保护下进行贮存。
准备将要进行涂覆的渗透材料粉末,该粉末由下面的工艺进行准备,按下列重量比将原材料进行配料,配料的成份范围为:Dy:60wt%、、Co:40wt%;将配合的料放入真空中频感应炉进熔炼,并采用速凝薄片工艺制备出平均厚度为0.3mm的薄片,其氧含量为60ppm。
在氢化炉中进行氢化破碎,只吸氢不进行脱氢处理,氢化破碎的速凝薄片经简单的机械破碎,使粉末平均粒度为1.0mm,氢含量为2000ppm。
在以惰性气体作为工作气体的气流磨中,将氢化破碎粉制成平均粒度为3微米的微粉,
所得微粉在惰性气体的保护下进行储存。
将上述微粉与酒精按0.5:1的重量比配制成涂覆溶液,在溶液体中添加分散剂0.2%,并充分搅拌。
经过清洗处理的毛坯磁体完全浸入涂覆溶液中浸泡并进行搅拌,浸入时间一分钟,将浸入完成后的磁体放入金属料盒中并加盖密闭,料盒材质为Ta。
将装有涂覆处理后毛坯磁体的料盒放入真空炉中进行二次热处理。首先抽真空,在真空度达到10-2Pa以上时升温到1050℃并保温时间1小时后充氩气冷却到100℃以下;然后抽真空到10-2Pa,加热到450℃,保温5小时;然后向烧结炉充入Ar气,使烧结炉冷却到80℃以下,获得最终磁体。
作为对比,将实施例2中毛坯磁体加工成的Φ10mm*10mm磁片未经渗透材料涂覆处理,直接进行二次热处理,热处理温度和保温时间同样为首先在1050℃保温时间1小时,其次450℃保温5小时,热处理在惰性气体保护下进行。
经过渗透处理获得的磁体(处理样品)与未进行渗透处理获得的磁体(未处理样品)的磁性参数测量结果如下:
样品 | Br(kGs) | Hcj(kOe) | (BH)max(MGOe) |
实施例2(处理样品) | 13.5 | 17.6 | 43.9 |
对比例2(未处理样品) | 13.6 | 12.3 | 44.7 |
实施例2工艺所获得磁体的剩磁Br与对比例2所获磁体的剩磁Br相比,在温度20℃下降低0.1kGs。
实施例2工艺所获得磁体的最大磁能积(BH)max与对比例2所获磁体的最大磁能积(BH)max相比,下降0.8MGOe。
实施例2工艺所获得磁体的Hcj与对比例2所获磁体的Hcj相比,Hcj上涨了5.3kOe。
居里温度测量采用振动样品磁强计,在300奥斯特(Oe)的外加磁场下测量磁化强度随温度的变化曲线(M-T曲线),以确定所述磁体的居里温度Tc。测量结果,对比例2的居里温度为312℃,实施例2为316℃。两者相差值为4℃
剩磁及矫顽力的温度系数的测量方法:首先在20℃下测量对比例2磁体的B-H曲线,得到Br(T0)=13.6kGs及Hcj(T0)=12.3kOe的值,然后再测出对比例120℃下磁体的Br(T)=11.9kGs及Hcj(T)=2.7kOe,使用如下公式进行计算,得到对比例2剩磁及矫顽力的温度系数;
依据上述公式,在温度20℃至120℃范围内,对比例2磁体的剩磁及矫顽力的温度系数为:αBr=-0.125%/℃,βHcj=-0.780%/℃
实施例2的温度系数测定采用同样的方法。其结果为:αBr=-0.115%/℃,βHcj=-0.712%/℃。
实施例2与对比例2剩磁Br的温度系数变化的绝对值为0.010,内禀矫顽力Hcj的温度系数变化的绝对值为0.068。
本实施例2磁体与对比例2磁体的失重分别为-2.5mg/cm2,-2.4mg/cm2。两者变化的绝对值为0.1mg/cm2。
密度测量采用排水法,本实施例2的密度为:7.52,对比例2为7.51,其变化率为0.13%。
采用X射线粉末衍射,实施例2所获得磁体的主相与未经渗透材料涂覆工序的对比例2所获磁体的主相相同,为Nd2Fe14B晶体结构;对比例2晶格常数a=0.8783nm,c=1.2128nm;实施例2晶格常数a=0.8777nm,c=1.2125nm。根据公式,二者晶格常数的变化率a为0.07%,c为0.02%。
X射线粉末衍射结果表明,实施例2渗透材料的金属间化合物主要为MgCu2相和少量的Th2Ni17相。或者说实施例2渗透材料主要具有MgCu2晶体结构,以及少量Th2Ni17晶体结构。
实施例3到15采用与实施例1和2相同的涂覆和热处理工艺步骤,并采用与实施例1和2相同的测量方法对所获得的磁体进行参数测定。同时对每个实施例在相同的热处理温度和时间下对毛坯磁体进行二次热处理获得对比例磁体,并使用相同的方法测定磁体参数。
表1为实施例1-15中渗透材料合金成分及涂覆溶液配制参数。
表2为实施例1-15中涂覆及热处理工艺参数。
表3为实施例及对比例1-15所制备的磁体及相应对比例磁体的性能参数及比较。
表1
表1(续)
表2
表2(续)
表3
表3(续)
Claims (50)
- 一种稀土永磁体的制备方法,其特征在于,所述方法包括:不包括回火处理步骤的毛坯磁体制备工序、渗透材料涂覆工序及热处理工序。
- 如权利要求1所述的稀土永磁体的制备方法,其特征在于:所述不包括回火处理步骤的毛坯磁体制备工序是指毛坯磁体经过配料-合金熔炼-粉碎制粉-成型-烧结工序制成。
- 如权利要求1所述的稀土永磁体的制备方法,其特征在于:所述渗透材料涂覆工序包括渗透材料粉末的制备、将渗透材料粉末制备成涂覆溶液、及在涂覆溶液中对毛坯磁体进行涂覆等工序。
- 如权利要求3所述的稀土永磁体的制备方法,其特征在于:所述渗透材料粉末的制备工序包括:(1)按比例进行配料;(2)熔炼合金;(3)将上述合金进行中破碎;(4)将上述中破碎后的粉末进行细粉碎。
- 如权利要求4所述的稀土永磁体的制备方法,其特征在于:所述熔炼合金为将配好的料放入真空中频感应炉中进行熔炼和浇铸,或采用速凝薄片工艺进行熔炼和甩片。
- 如权利要求4所述的稀土永磁体的制备方法,其特征在于:所述中破碎为将熔炼好的合金采用氢破碎工艺进行中破碎。
- 如权利要求4所述的稀土永磁体的制备方法,其特征在于:所述细粉碎为将中破碎后的粉末在采用惰性气体保护的气流磨中破碎成平均粒度2~6微米的微粉。
- 如权利要求4所述的稀土永磁体的制备方法,其特征在于:所述细粉碎后的微粉在惰性气体保护下进行储存。
- 如权利要求5所述的稀土永磁体的制备方法,其特征在于:所述浇铸熔炼得到的板状钢锭厚度为0.6~20mm。
- 如权利要求5所述的稀土永磁体的制备方法,其特征在于:所述浇铸熔炼得到的板状钢锭的氧含量≤300ppm。
- 如权利要求5所述的稀土永磁体的制备方法,其特征在于:所述采用速凝薄片工艺得到的薄片厚度为0.1~0.6mm。
- 如权利要求5所述的稀土永磁体的制备方法,其特征在于:所述采用速凝薄片工 艺得到的薄片的氧含量≤200ppm。
- 如权利要求6所述的稀土永磁体的制备方法,其特征在于:所述中破碎采用的氢化工艺只进行吸氢破碎过程。
- 如权利要求6所述的稀土永磁体的制备方法,其特征在于:所述中破碎后的粉末的平均粒度为0.5mm~1.0mm,氢含量≥2000ppm。
- 如权利要求3所述的稀土永磁体的制备方法,其特征在于:所述涂覆溶液的制备工序为将渗透材料粉末与醇类按不小于0.5:1的重量比配制。
- 如权利要求15所述的稀土永磁体的制备方法,其特征在于:所述醇类中可以添加分散剂,分散剂添加量为所用醇类的0~1%重量百分比。
- 如权利要求15所述的稀土永磁体的制备方法,其特征在于:所述醇类在低于800~1000℃时可以完全挥发,并不留残余。
- 如权利要求3所述的稀土永磁体的制备方法,其特征在于:所述涂覆工序为将毛坯磁体制备工序制备的毛坯磁体在涂覆溶液中浸泡并进行搅拌,浸入时间至少大于一分钟。
- 如权利要求18所述的稀土永磁体的制备方法,其特征在于:所述毛坯磁体在进行涂覆前要进行表面清洗,使用体积浓度小于5%硝酸进行酸洗,再用纯水漂洗去处残余酸液。
- 如权利要求1所述的稀土永磁体的制备方法,其特征在于:所述热处理工序为二次热处理。
- 如权利要求20所述的稀土永磁体的制备方法,其特征在于:所述二次热处理包括:(1)将经浸泡涂覆后的毛坯磁体放入料盒内送入真空烧结炉中热处理,在真空度达到10-2Pa时升温到820~1050℃并保温1~8小时,然后充氩气冷却到100℃以下;(2)停止冷却并抽真空到10-2Pa,再开始加热到450℃~620℃,保温1~5小时后停止加热,然后向烧结炉充入Ar气,使烧结炉冷却到80℃以下。
- 如权利要求20所述的稀土永磁体的制备方法,其特征在于:所述装有浸泡涂覆后毛坯磁体的料盒为加盖的密闭料盒。
- 如权利要求20所述的稀土永磁体的制备方法,其特征在于:所述料盒的材质为铁质材料,如不锈钢,45号钢等。
- 如权利要求20所述的稀土永磁体的制备方法,其特征在于:所述料盒的材质为 耐热材质,如Ta,W,Mo等耐热金属材质,或石墨材质。
- 如权利要求1所述的稀土永磁体的制备方法,其特征在于:所述渗透材料涂覆工序中使用的渗透材料为R-T合金或金属间化合物,其中R为稀土元素,T为过渡族金属元素和其它金属元素。
- 如权利要求25所述的稀土永磁体的制备方法,其特征在于:所述R-T合金或金属间化合物具有MgCu2、PuNi3、Th2Zh17或Th2Ni17晶体结构中的一种或一种以上。
- 如权利要求25或26所述的稀土永磁体的制备方法,其特征在于:所述R-T合金或金属间化合物中稀土元素R的含量不低于R-T总重量的50wt%,且其中元素Dy与Tb的含量之和不低于总重量的10wt%。
- 如权利要求25或26所述的稀土永磁体的制备方法,其特征在于:所述T为Fe、Co、Ni、Ti、V、Cr、Zr、Nb、Mo或W等过渡族金属元素及Ga、Cu、Zn或Sn金属元素中的一种或一种以上,其中元素Fe与Co的含量之和不高于R-T总重量的45wt%。
- 如权利要求1或2所述的稀土永磁体的制备方法,其特征在于:所述毛坯磁体的主相具有Nd2Fe14B四方晶体结构,其成份由R-T-B构成,其中R为稀土元素Nd、Pr、La、Ce、Dy、Tb、Ho、Gd、Lu或Y中的至少一种,T为过渡族金属Fe和Co、Cu、Ti、Cr、Zn、Ni中的至少一种。
- 如权利要求1或2所述的稀土永磁体的制备方法,其特征在于:所述毛坯磁体的氧含量≤4000ppm。
- 如权利要求1或2所述的稀土永磁体的制备方法,其特征在于:所述毛坯磁体取向方向的厚度≤10mm。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的密度与不包括渗透材料涂覆工序的制备方法所制备磁体的密度相比,变化率不大于0.13%。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的主相与不包括渗透材料涂覆工序的制备方法所制备磁体的主相相同,均具有Nd2Fe14B晶体结构,两者晶格常数的变化率不大于0.11%。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的居里温度Tc与不包括渗透材料涂覆工序的制备方法所制备磁体的居里温度Tc相比,变化不大于4℃。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于: 其所制备磁体的居里温度Tc与不包括渗透材料涂覆工序的制备方法所制备磁体的居里温度Tc相比,变化不大于3℃。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的内禀矫顽力Hcj与不包括渗透材料涂覆工序的制备方法所制备磁体的内禀矫顽力Hcj相比,增大至少1.0kOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的内禀矫顽力Hcj与不包括渗透材料涂覆工序的制备方法所制备磁体的内禀矫顽力Hcj相比,增大至少3.0kOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的内禀矫顽力Hcj与不包括渗透材料涂覆工序的制备方法所制备磁体的内禀矫顽力Hcj相比,增大至少5.0kOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的剩磁Br与不包括渗透材料涂覆工序的制备方法所制备磁体的剩磁Br相比,降低不大于0.5kGs。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的剩磁Br与不包括渗透材料涂覆工序的制备方法所制备磁体的剩磁Br相比,降低不大于0.3kGs。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的剩磁Br与不包括渗透材料涂覆工序的制备方法所制备磁体的剩磁Br相比,降低不大于0.2kGs。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的最大磁能积(BH)max与不包括渗透材料涂覆工序的制备方法所制备磁体的最大磁能积(BH)max相比,降低不大于3.5MGOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的最大磁能积(BH)max与不包括渗透材料涂覆工序的制备方法所制备磁体的最大磁能积(BH)max相比,降低不大于2.0MGOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的最大磁能积(BH)max与不包括渗透材料涂覆工序的制备方法所制备磁体的最大磁能积(BH)max相比,降低不大于1.5MGOe。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于: 其所制备的磁体在20℃~120℃温度之间的剩磁Br温度系数与不包括渗透材料涂覆工序的制备方法所制备磁体在相同温度范围内的剩磁Br温度系数相比,剩磁Br温度系数变化的绝对值≤0.011。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备的磁体在20℃~120℃温度之间的内禀矫顽力Hcj温度系数与不包括渗透材料涂覆工序的制备方法所制备磁体在相同温度范围内的内禀矫顽力Hcj温度系数相比,内禀矫顽力Hcj温度系数变化的绝对值≤0.100。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的直径10mm高10mm的样品在130℃环境温度,95%相对湿度,2.6大气压下放置240小时后,失重的绝对值不大于3.5mg/cm2。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的直径10mm高10mm的样品在130℃环境温度,95%相对湿度,2.6大气压下放置240小时后,失重的绝对值不大于2.5mg/cm2。
- 如权利要求1至31任一权利要求所述的稀土永磁体的制备方法,其特征在于:其所制备磁体的直径10mm高10mm的样品在130℃环境温度,95%相对湿度,2.6大气压下放置240小时后,失重与不包括渗透材料涂覆工序的制备方法所制备磁体的失重变化的绝对值不大于0.2mg/cm2。
- 如权利要求19所述的稀土永磁体的制备方法,其特征在于:所述清洗洁净的毛坯磁体要在惰性气体的保护下存放。
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