Dry-pressed permanent magnet ferrite, preparation method thereof, magnetic device and application thereof

Abstract

The application provides a dry-pressing permanent magnet ferrite, a preparation method thereof, a magnetic device and an application thereof, and raw materials of the dry-pressing permanent magnet ferrite include: ferrite pre-burning material, growth inhibitor, heat-conducting medium and crystal lattice stabilizer. The raw materials of the dry-pressing permanent magnet ferrite provided by the application include the growth inhibitor, the growth inhibitor can inhibit abnormal growth during the preparation process of the dry-pressing permanent magnet ferrite, so that the dry-pressing permanent magnet ferrite has a uniform structure; in addition, the raw materials of the dry-pressing permanent magnet ferrite further include the heat-conducting medium, the heat-conducting medium can increase internal stress of the dry-pressing permanent magnet ferrite due to uneven internal and external cold and heat under cold and heat impact; the raw materials of the dry-pressing permanent magnet ferrite further include the crystal lattice stabilizer, the crystal lattice stabilizer can reduce the risk of internal crystal structure damage caused by expansion or shrinkage of the dry-pressing permanent magnet ferrite, so as to affect the magnetic property. The dry-pressing permanent magnet ferrite not only has excellent magnetic property, but also has strong cold and heat impact resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and relates to a dry-pressed permanent magnet ferrite, in particular to a dry-pressed permanent magnet ferrite, a preparation method thereof, a magnetic device and application thereof. BACKGROUND

[0002] Since being applied as a magnetic material, ferrite has developed rapidly due to its rich raw materials and excellent chemical stability. Among them, the permanent magnet ferrite has high permeability and stable magnetic properties, and is widely used in the fields of automobiles, home appliances and aerospace. A mainstream process for preparing the permanent magnet ferrite is a dry process. The magnets prepared by the dry process are widely used in magnetic devices such as magnetic columns of micro-motors, multi-pole magnetic rings and magnetic tiles due to low raw material cost, simple equipment and stable performance. The performance of the magnetic device is mainly affected by the orientation of the powder, but the orientation of the powder in the permanent magnet ferrite prepared by the dry process in the prior art is difficult to control, thereby resulting in poor magnetic properties of the dry-pressed permanent magnet ferrite prepared.

[0003] Moreover, with the progress of technology and changes in application scenarios, the permanent magnet ferrite not only needs to have high magnetic properties, but also should have use performance in specific scenarios. The permanent magnet ferrite is mainly applied to components such as drive motors, converters and charging piles in new energy vehicles. The demand for the permanent magnet ferrite material gradually increases, and the requirements gradually become more stringent. In particular, the requirement for cold and hot impact is particularly important. While meeting the high saturation magnetization and high frequency operation of the permanent magnet ferrite, it is also necessary to ensure that the magnetic part will not crack due to expansion and contraction under repeated cold and hot alternation at high and low temperatures. Therefore, improving the cold and hot impact of the magnetic material plays a crucial role in protecting the components, but the cold and hot impact resistance of the permanent magnet ferrite in the prior art is insufficient to meet the actual application requirements.

[0004] CN106336212A discloses a Ni-Zn soft magnetic ferrite material for a transformer U-shaped part, raw materials of which include main materials and auxiliary materials; the main materials include, in terms of molar parts, 25-35 parts of iron oxide, 15-28 parts of manganese oxide, 10-20 parts of zinc oxide and 8-16 parts of nickel monoxide; based on the total mass of the raw materials, the auxiliary materials include 200-500 ppm of silicon dioxide, 100-300 ppm of lanthanum oxide, 100-180 ppm of lead dioxide, 200-300 ppm of niobium carbide, 100-150 ppm of tungsten trioxide, 150-250 ppm of vanadium pentoxide, 150-250 ppm of tantalum oxide, 100-180 ppm of zirconium oxide, 120-200 ppm of bismuth trioxide, 50-200 ppm of calcium carbonate, 120-250 ppm of lithium carbonate and 140-250 ppm of barium carbonate. The Ni-Zn soft magnetic ferrite material disclosed in the patent has small grain size, high resistivity, high initial permeability and low magnetic core loss.

[0005] CN112707723A discloses a wide-temperature ultra-low-power manganese-zinc ferrite material and a preparation method thereof, the main components of the material include 53-54.2mol% iron oxide, 8.5-9.8mol% zinc oxide and the balance manganese oxide, the first auxiliary component includes 0.3-0.5wt% tricobalt tetroxide and 0.05-0.1wt% titanium dioxide, the second auxiliary component includes calcium carbonate, silicon dioxide, niobium pentoxide, zirconium oxide, hafnium oxide, vanadium pentoxide, tantalum pentoxide, nickel oxide, lithium carbonate and aluminum oxide, by controlling the addition range of the main component and the first auxiliary component, the manganese-zinc ferrite basically realizes the performance of wide-temperature low-power consumption, the second auxiliary component is added to modify the loss, so that there is a lower power loss at each temperature; the cost of the additive is low, so as to reduce the production cost and save environmental resources to a certain extent on the premise of ensuring wide application in various extreme occasions.

[0006] The currently disclosed dry-pressed permanent magnet ferrite has certain defects, and has problems of poor magnetic performance and insufficient cold and hot impact resistance to meet the needs of actual application. Therefore, it is crucial to develop and design a new type of dry-pressed permanent magnet ferrite and a preparation method thereof, and a magnetic device. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a dry-pressed permanent magnet ferrite and a preparation method thereof, a magnetic device and its application. The raw material of the dry-pressed permanent magnet ferrite provided by the present application includes a growth inhibitor. The growth inhibitor can inhibit abnormal growth during the preparation process of the dry-pressed permanent magnet ferrite, so that the dry-pressed permanent magnet ferrite has a uniform structure, thereby having excellent magnetic performance. In addition, the raw material of the dry-pressed permanent magnet ferrite also includes a heat-conducting medium. The heat-conducting medium can increase the heat conduction path of the dry-pressed permanent magnet ferrite and improve the transmission speed of thermal energy, thereby coping with the internal stress caused by uneven internal and external cold and heat under cold and hot impact. The raw material of the dry-pressed permanent magnet ferrite also includes a lattice stabilizer. When coping with cold and hot impact, the lattice stabilizer can reduce the risk of internal crystal structure damage caused by expansion or shrinkage of the dry-pressed permanent magnet ferrite, thereby affecting the magnetic performance. Therefore, the dry-pressed permanent magnet ferrite not only has excellent magnetic performance, but also has strong cold and hot impact resistance.

[0008] To achieve this purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a dry-pressed permanent magnet ferrite, the raw material of the dry-pressed permanent magnet ferrite includes: ferrite pre-burning material, growth inhibitor, heat-conducting medium and lattice stabilizer.

[0010] The ferrite pre-burning material in the present application includes Sr 0.89La 0.11 Fe 11.89 Co 0.11 O 19 .

[0011] The raw material of the dry-pressed permanent magnet ferrite provided by the application comprises a growth inhibitor, which can inhibit abnormal growth during the preparation of the dry-pressed permanent magnet ferrite, so that the dry-pressed permanent magnet ferrite has a uniform structure and thus excellent magnetic properties. In addition, the raw material of the dry-pressed permanent magnet ferrite further comprises a heat-conducting medium, which can increase the heat conduction path of the dry-pressed permanent magnet ferrite and improve the heat transfer speed, so as to cope with the internal stress caused by uneven internal and external cold and heat under cold and heat shock. The raw material of the dry-pressed permanent magnet ferrite further comprises a crystal lattice stabilizer, which can reduce the risk of damage to the internal crystal structure caused by the expansion or shrinkage of the dry-pressed permanent magnet ferrite and thus affect the magnetic properties when the dry-pressed permanent magnet ferrite copes with cold and heat shock. Therefore, the dry-pressed permanent magnet ferrite not only has excellent magnetic properties, but also has strong cold and heat shock resistance.

[0012] Preferably, the raw material of the dry-pressed permanent magnet ferrite further comprises a fluxing agent.

[0013] Preferably, the fluxing agent comprises any one or a combination of at least two of V2O5, B2O3, SiO2, CaO or MgO, and typical but non-limiting combinations include a combination of V2O5 and B2O3, a combination of B2O3 and SiO2, a combination of SiO2 and CaO, a combination of CaO and MgO, or a combination of V2O5, B2O3 and SiO2, preferably V2O5.

[0014] The melting point of V2O5 in the application is relatively low, which can promote the growth of crystal grains during the preparation of the dry-pressed permanent magnet ferrite.

[0015] Preferably, the mass ratio of ferrite pre-calcined material to flux in the raw material is (500~3000):(2~8), for example, it can be 500:2, 500:3, 500:4, 500:5, 500:6, 500:7, 500:8, 900:2, 900:3, 900:4, 900:5, 900:6, 900:7, 900:8, 1300:2, 1300:4, 1300:5, 1300:6, 1300:7, 1300:8, 2100:2, 210 0:3, 2100:4, 2100:5, 2100:6, 2100:8, 2700:2, 2700:3, 2700:4, 2700:5, 2700:6, 2700:7, 2700:8, 3000:2, 3000:3, 3000:4, 3000:5, 3000:6, 3000:7 or 3000:8, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, with (1500~2500):(3~6) being the preferred value.

[0016] Preferably, the growth inhibitor comprises any one or a combination of at least two of La2O3, Al2O3, ZrO2 or CeO2, with typical but non-limiting combinations including a combination of La2O3 and Al2O3 or a combination of ZrO2 and CeO2, and preferably La2O3 and / or Al2O3.

[0017] In the preparation of dry-pressed permanent magnet ferrite in this invention, if the grain growth is too fast, it will lead to an abnormal increase in grain size, destroy the uniformity of the product, and reduce the magnetic properties. The growth inhibitor included in the raw materials of the dry-pressed permanent magnet ferrite provided by this invention can inhibit the abnormal growth of ferrite grains and promote uniform grain growth, thereby obtaining a dry-pressed permanent magnet ferrite with a uniform structure. In addition, when La2O3 is used as a growth inhibitor, La2O3 can not only inhibit the abnormal growth of ferrite grains, but also enhance the magnetic anisotropy in the dry-pressed permanent magnet ferrite, thereby enhancing the saturation magnetic field of the dry-pressed permanent magnet ferrite, increasing the maximum magnetic flux density of the dry-pressed permanent magnet ferrite, and increasing the grain boundary strength of the dry-pressed permanent magnet ferrite, thereby improving the tensile strength of the dry-pressed permanent magnet ferrite.

[0018] Preferably, the mass ratio of ferrite pre-calcined material to growth inhibitor in the raw material is (500~3000):(35~75), for example, it can be 500:35, 500:41, 500:47, 500:53, 500:57, 500:63, 500:67, 500:71, 500:75, 1300:35, 1300:41, 1300:47, 1300:53, 1300:57, 1300:63, 1300:67, 1300:71, 1300:75, or 2300:35. The values ​​are 2300:41, 2300:47, 2300:53, 2300:57, 2300:63, 2300:67, 2300:71, 2300:75, 3000:35, 3000:41, 3000:47, 3000:53, 3000:57, 3000:63, 3000:67, 3000:71 or 3000:75, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable, with (1500~2500):(43~68) being the preferred value.

[0019] Preferably, the thermally conductive medium includes any one or a combination of at least two of Si3N4, BN, or SiC. Typical but non-limiting combinations include a combination of Si3N4 and BN, a combination of BN and SiC, or a combination of Si3N4, BN, and SiC, with Si3N4 being the most preferred.

[0020] The raw material of the dry-pressed permanent magnet ferrite in this invention contains silicon nitride with high thermal conductivity and low expansion coefficient. This not only improves the thermal conductivity of the dry-pressed permanent magnet ferrite, thereby improving its heat dissipation performance, but also reduces its expansion coefficient, thereby improving its stability.

[0021] Preferably, the mass ratio of ferrite pre-calcined material to heat-conducting medium in the raw material is (500~3000):(1~12), for example, it can be 500:1, 500:3, 500:7, 500:11, 500:12, 1100:1, 1100:3, 1100:7, 1100:11, 1100:12, 1700:1, 1700:3, 1700:7 The ratios are 1700:11, 1700:12, 2300:1, 2300:3, 2300:7, 2300:11, 2300:12, 3000:1, 3000:7, 3000:11 or 3000:12, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable, with (1500~2500):(5~9) being the preferred ratio.

[0022] Preferably, the lattice stabilizer comprises MgO and / or CaCO3.

[0023] The raw materials of the dry-pressed permanent magnet ferrite in this invention include the lattice stabilizer CaCO3. CaCO3 can not only stabilize the lattice of the dry-pressed permanent magnet ferrite, but also change the sintering method of alumina in the growth inhibitor, thereby reducing the porosity and the thermal expansion coefficient of the dry-pressed permanent magnet ferrite, thus reducing the risk of expansion and contraction of the dry-pressed permanent magnet ferrite when subjected to thermal shock.

[0024] Preferably, the mass ratio of ferrite pre-calcined material to lattice stabilizer in the raw material is (500~3000):(20~65), for example, it can be 500:20, 500:27, 500:37, 500:47, 500:57, 500:65, 1100:20, 1100:27, 1100:37, 1100:47, 1100:57, 1100:65, 1900:20, 1900:27, 1900:37, 1900: 47, 1900:57, 1900:65, 2300:20, 2300:27, 2300:37, 2300:47, 2300:57, 2300:65, 3000:20, 3000:27, 3000:37, 3000:47, 3000:57, 3000:65, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, with (1500~2500):(29~53) being the preferred value.

[0025] In a second aspect, the present invention provides a method for preparing the dry-pressed permanent magnet ferrite described in the first aspect, the method comprising:

[0026] (1) A mixture is obtained by mixing ferrite pre-sintered material, flux, growth inhibitor, thermally conductive medium and lattice stabilizer;

[0027] (2) The mixture obtained in step (1) is preformed in a magnetic field and then crushed to obtain magnetic powder with orientation.

[0028] (3) After mixing the additives with the oriented magnetic powder obtained in step (2), dry pressing and sintering are carried out to obtain dry pressing permanent magnet ferrite.

[0029] Preferably, the mixing method in step (1) includes ball milling.

[0030] Preferably, a solvent is added during the ball milling process.

[0031] Preferably, the solvent includes water.

[0032] Preferably, the rotational speed of the ball mill is 200~600 r / min, for example, it can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min or 600 r / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 250~450 r / min.

[0033] Preferably, the ball milling time is 12 to 20 hours, for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, step (1) further includes solid-liquid separation after mixing.

[0035] Preferably, the solid-liquid separation method includes filtration.

[0036] Preferably, the magnetic field strength of the magnetic field in step (2) is 6000~10000Oe, for example, it can be 6000Oe, 6500Oe, 7000Oe, 7500Oe, 8000Oe, 8500Oe, 9000Oe, 9500Oe or 10000Oe, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the embryo preparation in step (2) is carried out under a pressure of 15 to 25 MPa, for example, it can be 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa or 25 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, step (2) further includes sieving after crushing.

[0039] Preferably, a sieve with a mesh size of 10 to 100 is used in the sieving process. For example, it can be 10 mesh, 20 mesh, 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh, 90 mesh or 100 mesh, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, a sieve with a mesh size of 20 to 50 is used.

[0040] Preferably, step (2) further includes drying after sieving.

[0041] Preferably, the drying temperature is 50~70℃, for example, it can be 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃ or 70℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the drying time is 3 to 25 hours, for example, 3 hours, 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, 24 hours or 25 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 6 to 24 hours.

[0043] Preferably, the moisture content of the oriented magnetic powder obtained after drying is 1.2% to 3.5%, for example, it can be 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, or 3.5%. However, it is not limited to the listed values, and other unlisted values ​​within this range are also applicable, preferably 1.8% to 2.6%.

[0044] Preferably, the additives in step (3) include lubricants and / or binders.

[0045] Preferably, the mixing in step (3) includes initially mixing the lubricant and the oriented magnetic powder obtained in step (2) to obtain a preliminary mixture, and then further mixing the obtained preliminary mixture with the binder.

[0046] Preferably, the mass ratio of the lubricant to the oriented magnetic powder obtained in step (2) is (2~30): (500~3000), for example, it can be 2:500, 2:1000, 2:1500, 2:2000, 2:2500, 2:3000, 9:500, 9:1000, 9:1500, 9:2000, 9:2500, 9:3000, 16:500, 16:1000, 16:1500, 16:2000, 16:2500, 16:3000, 2 3:500, 23:1000, 23:1500, 23:2000, 23:2500, 23:3000, 30:500, 30:1000, 30:1500, 30:2000, 30:2500 or 30:3000, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, with (10~15): (1500~2500) being the preferred value.

[0047] Preferably, the lubricant comprises any one or a combination of at least two of zinc stearate, magnesium stearate, or calcium stearate. Typical but non-limiting combinations include combinations of zinc stearate and magnesium stearate, combinations of magnesium stearate and calcium stearate, or combinations of zinc stearate, magnesium stearate, and calcium stearate.

[0048] Preferably, the mass ratio of the adhesive to the oriented magnetic powder obtained in step (2) is (1~25):(500~3000), for example, it can be 1:500, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, 7:500, 7:1000, 7:1500, 7:2000, 7:2500, 7:3000, 13:500, 13:1000, 13:1500, 13:2000, 13:2500, 13: 3000, 19:500, 19:1000, 19:1500, 19:2000, 19:2500, 19:3000, 25:500, 25:1000, 25:1500, 25:2000, 25:2500 or 25:3000, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably (8~16): (1500~2500).

[0049] Preferably, the adhesive comprises any one or a combination of at least two of camphor, epoxy resin, or polyvinyl alcohol. Typical but non-limiting combinations include a combination of camphor and epoxy resin, a combination of epoxy resin and polyvinyl alcohol, or a combination of camphor, epoxy resin, and polyvinyl alcohol.

[0050] Preferably, the initial mixing and remixing methods each independently include stirring.

[0051] Preferably, the dry pressing sintering in step (3) includes: pressing and forming in a magnetic field followed by heat treatment.

[0052] Preferably, the magnetic field strength during the pressing process is 10000~14000 Oe, for example, it can be 10000 Oe, 10500 Oe, 11000 Oe, 11500 Oe, 12000 Oe, 12500 Oe, 13000 Oe, 13500 Oe or 14000 Oe, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, the pressure used during the pressing process is 30~70MPa, for example, it can be 30MPa, 35MPa, 40MPa, 45MPa, 50MPa, 55MPa, 60MPa, 65MPa or 70MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the heat treatment includes sequentially performing a first heating, a first holding, a second heating, a second holding, a third heating, a third holding, a fourth heating, a fourth holding, and furnace cooling.

[0055] Preferably, the first heating rate is 3~10℃ / min, for example, it can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 5~8℃ / min.

[0056] Preferably, the endpoint temperature of the first heating is 300~500℃, for example, it can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃ or 500℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] Preferably, the first heat preservation time is 0.1 to 5 hours, for example, it can be 0.1 hours, 0.2 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1 to 3 hours.

[0058] Preferably, the second heating rate is 3~8℃ / min, for example, it can be 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min or 8℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 4~6℃ / min.

[0059] Preferably, the endpoint temperature of the second heating is 600~800℃, for example, it can be 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃ or 800℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0060] Preferably, the second heat preservation time is 0.1 to 8 hours, for example, it can be 0.1 hours, 0.2 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1 to 6 hours.

[0061] Preferably, the third heating rate is 2~7℃ / min, for example, it can be 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min or 7℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 3~6℃ / min.

[0062] Preferably, the endpoint temperature of the third heating is 900~1100℃, for example, it can be 900℃, 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1040℃, 1060℃, 1080℃ or 1100℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0063] Preferably, the third heat preservation time is 0.1 to 5 hours, for example, it can be 0.1 hours, 0.2 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1 to 4 hours.

[0064] Preferably, the fourth heating rate is 0.1~5℃ / min, for example, it can be 0.1℃ / min, 0.2℃ / min, 0.5℃ / min, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1~4℃ / min.

[0065] Preferably, the final temperature of the fourth heating is 1200~1300℃, for example, it can be 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, 1260℃, 1270℃, 1280℃, 1290℃ or 1300℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0066] Preferably, the fourth heat preservation time is 0.1 to 12 hours, for example, it can be 0.1 hours, 0.2 hours, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 3 to 10 hours.

[0067] Preferably, the preparation method further includes grinding and cleaning performed sequentially after furnace cooling.

[0068] As a preferred embodiment of the preparation method of the present invention, the preparation method includes:

[0069] (1) The ferrite pre-calcined material, flux, growth inhibitor, heat transfer medium and lattice stabilizer are mixed by ball milling at a speed of 200~600r / min for 12~20h. Solvent is added during the ball milling process, and the mixture is obtained after solid-liquid separation.

[0070] (2) The mixture obtained in step (1) is subjected to a magnetic field with a magnetic field strength of 6000~10000Oe and a pressure of 15~25MPa to form a preform, then crushed, and then sieved through a 10~100 mesh sieve and dried to obtain magnetic powder with an orientation with a moisture content of 1.2~3.5%.

[0071] (3) After the initial mixture of lubricant and oriented magnetic powder obtained in step (2) is obtained, the initial mixture is then mixed with binder. The mass ratio of lubricant to oriented magnetic powder is (2~30):(500~3000), and the mass ratio of binder to oriented magnetic powder is (1~25):(500~3000).

[0072] After being pressed and formed in a magnetic field with a strength of 10000~14000Oe and a pressure of 30~70MPa, the temperature is raised to 300~500℃ at a rate of 3~10℃ / min and held for 0.1~5h. Then, the temperature is raised to 600~800℃ at a rate of 3~8℃ / min and held for 0.1~8h. Then, the temperature is raised to 900~1100℃ at a rate of 2~7℃ / min and held for 0.1~5h. Then, the temperature is raised to 1200~1300℃ at a rate of 0.1~5℃ / min and held for 0.1~12h. Finally, the mixture is cooled in the furnace to obtain dry-pressed permanent magnet ferrite.

[0073] Thirdly, the present invention provides a magnetic device, the magnetic device comprising the dry-pressed permanent magnet ferrite described in the first aspect.

[0074] Fourthly, the present invention provides an application of the magnetic device described in the third aspect, wherein the magnetic device is used in automobiles, home appliances and aerospace.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] The raw materials for the dry-pressed permanent magnet ferrite provided by this invention include growth inhibitors, which can suppress abnormal growth during the preparation process of the dry-pressed permanent magnet ferrite, resulting in a uniform structure and thus excellent magnetic properties. Additionally, the raw materials also include a thermally conductive medium, which increases the heat conduction path and improves the heat transfer rate, thereby mitigating internal stress caused by uneven internal and external heating under thermal shock. Furthermore, the raw materials also include a lattice stabilizer, which reduces the risk of internal crystal structure damage due to expansion or contraction of the dry-pressed permanent magnet ferrite, thus affecting its magnetic properties. Therefore, the dry-pressed permanent magnet ferrite not only possesses excellent magnetic properties but also exhibits strong resistance to thermal shock. Detailed Implementation

[0077] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0078] Example 1

[0079] This embodiment provides a dry-pressed permanent magnet ferrite, the raw materials of which include: ferrite pre-sintered material, V2O5, La2O3, Al2O3, Si3N4, MgO and CaCO3;

[0080] The raw materials have the following mass ratios: ferrite pre-calcined material to V2O5: 2000:5, ferrite pre-calcined material to La2O3: 2000:40, ferrite pre-calcined material to Al2O3: 2000:10, ferrite pre-calcined material to Si3N4: 2000:8, ferrite pre-calcined material to MgO: 2000:5, and ferrite pre-calcined material to CaCO3: 2000:30.

[0081] The method for preparing the dry-pressed permanent magnet ferrite includes:

[0082] (1) Ferrite pre-calcined material, V2O5, La2O3, Al2O3, Si3N4, MgO and CaCO3 were mixed by ball milling at a speed of 300 r / min for 16 h. Water was added during the ball milling process, and the mixture was obtained after solid-liquid separation.

[0083] (2) The mixture obtained in step (1) is crushed after being formed in a magnetic field with a magnetic field strength of 8000 Oe and a pressure of 20 MPa. After being sieved through a 30-mesh sieve and dried, magnetic powder with orientation with a moisture content of 2% is obtained.

[0084] (3) After the initial mixture of zinc stearate and the magnetic powder with orientation obtained in step (2) is obtained, the initial mixture is then mixed with camphor. The mass ratio of zinc stearate to magnetic powder with orientation is 15:1500, and the mass ratio of camphor to magnetic powder with orientation is 10:1500.

[0085] After being pressed and formed in a magnetic field with a strength of 12000 Oe and a pressure of 50 MPa, the temperature is increased to 400℃ at a rate of 6℃ / min and held for 2 hours, then increased to 700℃ at a rate of 5℃ / min and held for 4 hours, then increased to 1000℃ at a rate of 4℃ / min and held for 3 hours, then increased to 1260℃ at a rate of 3℃ / min and held for 6 hours, and then cooled in the furnace to obtain dry-pressed permanent magnet ferrite.

[0086] Example 2

[0087] This embodiment provides a dry-pressed permanent magnet ferrite, the raw materials of which include: ferrite pre-sintered material, SiO2, ZrO2, SiC and CaCO3.

[0088] The mass ratio of ferrite pre-calcined material to SiO2 in the raw materials is 500:8, the mass ratio of ferrite pre-calcined material to ZrO2 is 500:75, the mass ratio of ferrite pre-calcined material to SiC is 3000:1, and the mass ratio of ferrite pre-calcined material to CaCO3 is 500:65.

[0089] The method for preparing the dry-pressed permanent magnet ferrite includes:

[0090] (1) Ferrite pre-calcined material, SiO2, ZrO2, SiC and CaCO3 were mixed by ball milling at a speed of 600 r / min for 12 h. Water was added during the ball milling process, and the mixture was obtained after solid-liquid separation.

[0091] (2) The mixture obtained in step (1) is subjected to a magnetic field with a magnetic field strength of 10000 Oe and a pressure of 15 MPa for preforming and crushing. Then it is sieved through a 100-mesh sieve and dried to obtain magnetic powder with an orientation of 3.5% moisture content.

[0092] (3) After the initial mixture of calcium stearate and the oriented magnetic powder obtained in step (2) is obtained, the initial mixture is then mixed with polyvinyl alcohol. The mass ratio of calcium stearate to oriented magnetic powder is 2:3000, and the mass ratio of polyvinyl alcohol to oriented magnetic powder is 25:500.

[0093] After being pressed and formed in a magnetic field with a strength of 10000 Oe and a pressure of 70 MPa, the temperature is increased to 500℃ at a rate of 10℃ / min and held for 0.1 h. Then, the temperature is increased to 600℃ at a rate of 3℃ / min and held for 8 h. Then, the temperature is increased to 1100℃ at a rate of 7℃ / min and held for 0.1 h. Then, the temperature is increased to 1300℃ at a rate of 0.1℃ / min and held for 0.1 h. Finally, the mixture is cooled in the furnace to obtain dry-pressed permanent magnet ferrite.

[0094] Example 3

[0095] This embodiment provides a dry-pressed permanent magnet ferrite, except that the V2O5 in the raw materials is omitted, that is, the mixing of V2O5 in step (1) of the preparation method of the dry-pressed permanent magnet ferrite is omitted, and the rest is the same as in Example 1.

[0096] Example 4

[0097] This embodiment provides a dry-pressed permanent magnet ferrite. Except that the total mass ratio of ferrite pre-calcined material to La2O3 and Al2O3 in the raw materials of the dry-pressed permanent magnet ferrite is 300:75, and the mass ratio of La2O3 to Al2O3 remains unchanged, all other aspects are the same as in Example 1.

[0098] Example 5

[0099] This embodiment provides a dry-pressed permanent magnet ferrite. Except that the total mass ratio of ferrite pre-calcined material to La2O3 and Al2O3 in the raw materials of the dry-pressed permanent magnet ferrite is 3500:30, and the mass ratio of La2O3 to Al2O3 remains unchanged, all other aspects are the same as in Example 1.

[0100] Example 6

[0101] This embodiment provides a dry-pressed permanent magnet ferrite, except that the mass ratio of ferrite pre-calcined material to Si3N4 in the raw materials of the dry-pressed permanent magnet ferrite is 300:12, and all other aspects are the same as in Embodiment 1.

[0102] Example 7

[0103] This embodiment provides a dry-pressed permanent magnet ferrite, except that the mass ratio of ferrite pre-calcined material to Si3N4 in the raw materials of the dry-pressed permanent magnet ferrite is 3500:1, and all other aspects are the same as in Embodiment 1.

[0104] Example 8

[0105] This embodiment provides a dry-pressed permanent magnet ferrite. Except that the total mass ratio of ferrite pre-calcined material to MgO and CaCO3 in the raw materials of the dry-pressed permanent magnet ferrite is 300:65, and the mass ratio of MgO to CaCO3 remains unchanged, all other aspects are the same as in Example 1.

[0106] Example 9

[0107] This embodiment provides a dry-pressed permanent magnet ferrite. Except that the total mass ratio of ferrite pre-calcined material to MgO and CaCO3 in the raw materials of the dry-pressed permanent magnet ferrite is 3500:20, and the mass ratio of MgO to CaCO3 remains unchanged, all other aspects are the same as in Example 1.

[0108] Example 10

[0109] This embodiment provides a dry-pressed permanent magnet ferrite. Except for step (2) of the preparation method of the dry-pressed permanent magnet ferrite, in which an 8-mesh sieve is used for sieving, the rest is the same as in embodiment 1.

[0110] Example 11

[0111] This embodiment provides a dry-pressed permanent magnet ferrite. Except for step (2) of the preparation method of the dry-pressed permanent magnet ferrite, in which a 120-mesh sieve is used for sieving, the rest is the same as in embodiment 1.

[0112] Example 12

[0113] This embodiment provides a dry-pressed permanent magnet ferrite, except that in step (2) of the preparation method of the dry-pressed permanent magnet ferrite, after drying, the magnetic powder with an orientation content of 1% is obtained, and the rest is the same as in embodiment 1.

[0114] Example 13

[0115] This embodiment provides a dry-pressed permanent magnet ferrite. Except for step (2) of the dry-pressed permanent magnet ferrite preparation method, in which the magnetic powder with a water content of 4% is obtained after drying, the rest is the same as in the embodiment.

[0116] Example 14

[0117] This embodiment provides a dry-pressed permanent magnet ferrite, except that the La2O3 in the raw material is replaced with an equal mass of Al2O3, that is, the growth inhibitor in the raw material of the dry-pressed permanent magnet ferrite only includes Al2O3, and the rest is the same as in Example 1.

[0118] Example 15

[0119] This embodiment provides a dry-pressed permanent magnet ferrite, except that the CaCO3 in the raw material is replaced with an equal mass of MgO, that is, the lattice stabilizer in the raw material of the dry-pressed permanent magnet ferrite only includes MgO, and the rest is the same as in Example 1.

[0120] Comparative Example 1

[0121] This comparative example provides a dry-pressed permanent magnet ferrite, except that the mixing of La2O3 and Al2O3 in the raw materials is omitted, that is, the mixing of La2O3 and Al2O3 in step (1) of the preparation method of the dry-pressed permanent magnet ferrite is omitted, and the rest is the same as in Example 1.

[0122] Comparative Example 2

[0123] This comparative example provides a dry-pressed permanent magnet ferrite, except that Si3N4 in the raw materials is omitted, that is, the mixing of Si3N4 in step (1) of the preparation method of the dry-pressed permanent magnet ferrite is omitted, and the rest is the same as in Example 1.

[0124] Comparative Example 3

[0125] This comparative example provides a dry-pressed permanent magnet ferrite, except that the mixing of MgO and CaCO3 in step (1) of the preparation method of the dry-pressed permanent magnet ferrite is omitted, and the rest is the same as in Example 1.

[0126] The dry-pressed permanent magnet ferrites provided in Examples 1-15 and Comparative Examples 1-3 were subjected to magnetic performance tests and thermal shock tests.

[0127] The method for testing the magnetic properties is as follows: The remanence (Brema) of the magnetic material is measured using a BH performance tester. r Magnetic coercivity H cb Innate coercivity H cj and maximum energy product (BH) max As shown in Table 1;

[0128] The method for thermal shock testing is as follows: Take 50 dry-pressed permanent magnet ferrite samples provided in Examples 1-15 and Comparative Examples 1-3 respectively, treat them at -40℃ for 3 minutes and then place them at 125℃ for 3 minutes, which is recorded as one cycle. After 500 cycles, the number of dry-pressed permanent magnet ferrite samples that cracked was observed using an electron microscope, as shown in Table 1.

[0129] Table 1

[0130]

[0131] From Table 1, we can obtain:

[0132] (1) The dry-pressed permanent magnet ferrite provided in Examples 1-2 has high remanence, high magnetic coercivity, high intrinsic coercivity and high maximum magnetic energy product, and the number of samples that cracked after thermal shock test is small. Therefore, the dry-pressed permanent magnet ferrite not only has excellent magnetic properties, but also has strong resistance to thermal shock.

[0133] (2) By comparing Example 1 and Example 3, it can be seen that the flux in the raw materials of the dry-pressed permanent magnet ferrite in this invention will affect the performance of the dry-pressed permanent magnet ferrite. When the flux is omitted, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the flux has a lower melting point and will melt first to form a liquid phase, thereby promoting the uniform growth of the grains. The lack of flux will lead to a decrease in the uniformity of the grains, thereby reducing the magnetic properties.

[0134] (3) By comparing Example 1 with Examples 4 and 5, it can be seen that the mass ratio of ferrite pre-sintered material to growth inhibitor in the raw materials of the dry-pressed permanent magnet ferrite described in this invention will affect the performance of the dry-pressed permanent magnet ferrite. When the mass ratio of ferrite pre-sintered material to growth inhibitor is too low, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because excessive growth inhibitor will increase the grain boundary strength of ferrite, hinder the formation and movement of magnetic domains, and thus reduce the magnetic performance. When the mass ratio of ferrite pre-sintered material to growth inhibitor is too high, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the growth inhibitor has a high melting point, which can inhibit the excessive growth of grains and make the grains uniform. If the content of growth inhibitor is too low, it will lead to disordered growth of grains, affecting the compactness of ferrite and reducing the magnetic performance.

[0135] (4) By comparing Example 1 with Examples 6 and 7, it can be seen that the mass ratio of ferrite pre-sintered material to heat-conducting medium in the raw materials of the dry-pressed permanent magnet ferrite in this invention will affect the performance of the dry-pressed permanent magnet ferrite. When the mass ratio of ferrite pre-sintered material to heat-conducting medium is low, the remanence of the dry-pressed permanent magnet ferrite will be low, the magnetic coercivity will be low, the intrinsic coercivity will be low, and the maximum magnetic energy product will be low. This is because the heat-conducting medium has a high melting point, which is not conducive to the movement of magnetic domains and the uniformity of grains, thus reducing the magnetic performance. When the mass ratio of ferrite pre-sintered material to heat-conducting medium is high, the remanence of the dry-pressed permanent magnet ferrite will be low, the magnetic coercivity will be low, the intrinsic coercivity will be low, and the maximum magnetic energy product will be low. This is because when the content of heat-conducting medium is low, the poor thermal conductivity leads to greater internal stress, thereby reducing the magnetic performance.

[0136] (5) By comparing Example 1 with Examples 8 and 9, it can be seen that the mass ratio of ferrite pre-sintered material to lattice stabilizer in the raw materials of the dry-pressed permanent magnet ferrite described in this invention will affect the performance of the dry-pressed permanent magnet ferrite. When the mass ratio of ferrite pre-sintered material to lattice stabilizer is too low, the remanence of the dry-pressed permanent magnet ferrite will decrease, the magnetic coercivity will decrease, the intrinsic coercivity will decrease, and the maximum magnetic energy product will decrease. This is because the lattice stabilizer is a high-melting-point non-magnetic additive, and a high content will reduce the content of magnetic materials, resulting in a decrease in magnetic properties. When the mass ratio of ferrite pre-sintered material to lattice stabilizer is too high, the remanence of the dry-pressed permanent magnet ferrite will decrease, the magnetic coercivity will decrease, the intrinsic coercivity will decrease, and the maximum magnetic energy product will decrease. This is because the lattice stabilizer content is too low, the ferrite grains grow abnormally, resulting in a decrease in magnetic properties.

[0137] (6) By comparing Example 1 with Examples 10 and 11, it can be seen that the mesh size of the sieve used in step (2) of the dry-pressed permanent magnet ferrite preparation method of the present invention will affect the performance of the dry-pressed permanent magnet ferrite. When the mesh size of the sieve is too small, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the particle size is too large, resulting in larger gaps in the pressed ferrite and lower density, thereby reducing the magnetic performance. When the mesh size of the sieve is too large, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the frictional resistance between powder particles is greater, the flowability is worse, and the loose density is smaller.

[0138] (7) By comparing Example 1 with Examples 12 and 13, it can be seen that the moisture content of the oriented magnetic powder obtained after drying in step (2) of the preparation method of dry-pressed permanent magnet ferrite of the present invention affects the performance of dry-pressed permanent magnet ferrite. When the moisture content is too low, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the low moisture content leads to an increase in magnetic domain resistance, which reduces the orientation of the ferrite and thus the magnetic performance will decrease. When the moisture content is too high, the remanence of the dry-pressed permanent magnet ferrite will be lower, the magnetic coercivity will be lower, the intrinsic coercivity will be lower, and the maximum magnetic energy product will be lower. This is because the high moisture content causes evaporation during sintering, which increases the porosity of the ferrite and reduces the density of the ferrite, thus reducing the magnetic performance.

[0139] (8) By comparing Example 1 and Example 14, it can be seen that when La2O3 is used as a growth inhibitor in this invention, La2O3 can not only inhibit the abnormal growth of ferrite grains, but also enhance the magnetic anisotropy in dry-pressed permanent magnet ferrite, thereby enhancing the saturation magnetic field of dry-pressed permanent magnet ferrite, and also increasing the maximum magnetic flux density of dry-pressed permanent magnet ferrite, while also increasing the grain boundary strength of dry-pressed permanent magnet ferrite, thereby increasing the tensile strength of dry-pressed permanent magnet ferrite;

[0140] (8) By comparing Example 1 and Example 15, it can be seen that CaCO3 is used as a lattice stabilizer in this invention. CaCO3 can not only stabilize the lattice of dry-pressed permanent magnet ferrite, but also change the sintering method of alumina in the growth inhibitor, thereby reducing the porosity and the thermal expansion coefficient of dry-pressed permanent magnet ferrite, thereby further reducing the risk of expansion and contraction of dry-pressed permanent magnet ferrite when subjected to thermal shock.

[0141] (9) By comparing Example 1 and Comparative Example 1, it can be seen that the growth inhibitor in the raw material of the dry-pressed permanent magnet ferrite in this invention will affect the performance of the dry-pressed permanent magnet ferrite. This is because if the grain growth is too fast during the preparation of the dry-pressed permanent magnet ferrite, it will lead to an abnormal increase in grain size, which will destroy the uniformity of the product and reduce the magnetic properties. The growth inhibitor included in the raw material of the dry-pressed permanent magnet ferrite provided by this invention can inhibit the abnormal growth of ferrite grains and promote uniform grain growth, thereby obtaining a dry-pressed permanent magnet ferrite with a uniform structure.

[0142] (10) By comparing Example 1 and Comparative Example 2, it can be seen that the raw materials of the dry-pressed permanent magnet ferrite in this invention also include a heat-conducting medium. The heat-conducting medium can increase the heat conduction path of the dry-pressed permanent magnet ferrite and improve the heat transfer speed, thereby coping with the internal stress caused by the uneven internal and external heating and cooling under thermal shock.

[0143] (11) By comparing Example 1 and Comparative Example 3, it can be seen that the raw materials of the dry-pressed permanent magnet ferrite in this invention also include a lattice stabilizer. When dry-pressed permanent magnet ferrite is subjected to thermal shock, the lattice stabilizer can reduce the risk of damage to the internal crystal structure caused by the expansion or contraction of the dry-pressed permanent magnet ferrite, thereby affecting the magnetic properties.

[0144] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A dry-pressed permanent magnet ferrite, characterized in that, The raw materials for the dry-pressed permanent magnet ferrite include: ferrite pre-sintered material, growth inhibitor, thermally conductive medium and lattice stabilizer; The thermally conductive medium is any one of Si3N4, BN, or SiC. The ferrite pre-sintered material includes Sr 0.89 La 0.11 Fe 11.89 Co 0.11 O 19 ; The mass ratio of ferrite pre-calcined material to heat-conducting medium in the raw materials is (500~3000):(1~12).

2. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The raw materials for the dry-pressed permanent magnet ferrite also include flux.

3. The dry-pressed permanent magnet ferrite according to claim 2, characterized in that, The flux includes any one or a combination of at least two of V2O5, B2O3, SiO2, CaO, or MgO.

4. The dry-pressed permanent magnet ferrite according to claim 2, characterized in that, The flux is V2O5.

5. The dry-pressed permanent magnet ferrite according to claim 2, characterized in that, The mass ratio of ferrite pre-calcined material to flux in the raw materials is (500~3000):(2~8).

6. The dry-pressed permanent magnet ferrite according to claim 2, characterized in that, The mass ratio of ferrite pre-calcined material to flux in the raw materials is (1500~2500):(3~6).

7. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The growth inhibitors include any one or a combination of at least two of La2O3, Al2O3, ZrO2, or CeO2.

8. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The growth inhibitor is La2O3 and / or Al2O3.

9. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The mass ratio of ferrite pre-calcined material to growth inhibitor in the raw materials is (500~3000):(35~75).

10. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The mass ratio of ferrite pre-calcined material to growth inhibitor in the raw materials is (1500~2500):(43~68).

11. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The lattice stabilizer includes MgO and / or CaCO3.

12. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The mass ratio of ferrite pre-calcined material to lattice stabilizer in the raw materials is (500~3000):(20~65).

13. The dry-pressed permanent magnet ferrite according to claim 1, characterized in that, The mass ratio of ferrite pre-calcined material to lattice stabilizer in the raw materials is (1500~2500):(29~53).

14. A method for preparing dry-pressed permanent magnet ferrite according to any one of claims 1 to 13, characterized in that, The preparation method includes: (1) A mixture is obtained by mixing ferrite pre-sintered material, flux, growth inhibitor, thermally conductive medium and lattice stabilizer; (2) The mixture obtained in step (1) is preformed in a magnetic field and then crushed to obtain magnetic powder with orientation. (3) After mixing the additives with the oriented magnetic powder obtained in step (2), dry pressing and sintering are carried out to obtain dry pressing permanent magnet ferrite.

15. The preparation method according to claim 14, characterized in that, The mixing method described in step (1) includes ball milling.

16. The preparation method according to claim 15, characterized in that, Solvent is added during the ball milling process.

17. The preparation method according to claim 15, characterized in that, The ball mill rotates at a speed of 200~600 r / min.

18. The preparation method according to claim 15, characterized in that, The ball mill rotates at a speed of 250~450 r / min.

19. The preparation method according to claim 15, characterized in that, The ball milling time is 12-20 hours.

20. The preparation method according to claim 14, characterized in that, Step (1) also includes solid-liquid separation after mixing.

21. The preparation method according to claim 14, characterized in that, The magnetic field strength of the magnetic field in step (2) is 6000~10000 Oe.

22. The preparation method according to claim 14, characterized in that, The embryo preparation in step (2) is carried out under a pressure of 15~25MPa.

23. The preparation method according to claim 14, characterized in that, Step (2) also includes sieving after crushing.

24. The preparation method according to claim 23, characterized in that, A 10-100 mesh sieve is used in the sieving process.

25. The preparation method according to claim 23, characterized in that, A 20-50 mesh sieve is used in the sieving process.

26. The preparation method according to claim 23, characterized in that, Step (2) also includes drying after sieving.

27. The preparation method according to claim 26, characterized in that, The drying time is 3 to 25 hours.

28. The preparation method according to claim 26, characterized in that, The drying time is 6 to 24 hours.

29. The preparation method according to claim 26, characterized in that, The drying temperature is 50~70℃.

30. The preparation method according to claim 26, characterized in that, The moisture content of the oriented magnetic powder obtained after drying is 1.2~3.5%.

31. The preparation method according to claim 26, characterized in that, The moisture content of the oriented magnetic powder obtained after drying is 1.8~2.6%.

32. The preparation method according to claim 14, characterized in that, The additives in step (3) include lubricants and / or binders.

33. The preparation method according to claim 32, characterized in that, The mixing in step (3) includes initially mixing the lubricant and the oriented magnetic powder obtained in step (2) to obtain a preliminary mixture, and then further mixing the obtained preliminary mixture with the binder.

34. The preparation method according to claim 33, characterized in that, The mass ratio of the lubricant to the oriented magnetic powder obtained in step (2) is (2~30):(500~3000).

35. The preparation method according to claim 33, characterized in that, The mass ratio of the lubricant to the oriented magnetic powder obtained in step (2) is (10~15): (1500~2500).

36. The preparation method according to claim 32, characterized in that, The lubricant includes any one or a combination of at least two of zinc stearate, magnesium stearate, and calcium stearate.

37. The preparation method according to claim 33, characterized in that, The mass ratio of the binder to the oriented magnetic powder obtained in step (2) is (1~25):(500~3000).

38. The preparation method according to claim 33, characterized in that, The mass ratio of the binder to the oriented magnetic powder obtained in step (2) is (8~16): (1500~2500).

39. The preparation method according to claim 32, characterized in that, The adhesive includes any one or a combination of at least two of camphor, epoxy resin, or polyvinyl alcohol.

40. The preparation method according to claim 14, characterized in that, The dry pressing sintering in step (3) includes: pressing and shaping in a magnetic field followed by heat treatment.

41. The preparation method according to claim 40, characterized in that, The magnetic field strength during the pressing process is 10000~14000 Oe.

42. The preparation method according to claim 40, characterized in that, The pressure used during the compression molding process is 30~70MPa.

43. The preparation method according to claim 40, characterized in that, The heat treatment includes sequentially performing a first heating, a first holding, a second heating, a second holding, a third heating, a third holding, a fourth heating, a fourth holding, and furnace cooling.

44. The preparation method according to claim 43, characterized in that, The first heating rate is 3~10℃ / min.

45. The preparation method according to claim 43, characterized in that, The first heating rate is 5~8℃ / min.

46. ​​The preparation method according to claim 43, characterized in that, The final temperature of the first heating is 300~500℃.

47. The preparation method according to claim 43, characterized in that, The first heat preservation time is 0.1~5h.

48. The preparation method according to claim 43, characterized in that, The first heat preservation time is 1~3 hours.

49. The preparation method according to claim 43, characterized in that, The second heating rate is 3~8℃ / min.

50. The preparation method according to claim 43, characterized in that, The second heating rate is 4~6℃ / min.

51. The preparation method according to claim 43, characterized in that, The final temperature of the second heating is 600~800℃.

52. The preparation method according to claim 43, characterized in that, The second heat preservation time is 0.1~8h.

53. The preparation method according to claim 43, characterized in that, The second heat preservation time is 1 to 6 hours.

54. The preparation method according to claim 43, characterized in that, The third heating rate is 2~7℃ / min.

55. The preparation method according to claim 43, characterized in that, The third heating rate is 3~6℃ / min.

56. The preparation method according to claim 43, characterized in that, The final temperature of the third heating step is 900~1100℃.

57. The preparation method according to claim 43, characterized in that, The third insulation time is 0.1~5h.

58. The preparation method according to claim 43, characterized in that, The third insulation time is 1 to 4 hours.

59. The preparation method according to claim 43, characterized in that, The fourth heating rate is 0.1~5℃ / min.

60. The preparation method according to claim 43, characterized in that, The fourth heating rate is 1~4℃ / min.

61. The preparation method according to claim 43, characterized in that, The final temperature of the fourth heating step is 1200~1300℃.

62. The preparation method according to claim 43, characterized in that, The fourth heat preservation time is 0.1~12h.

63. The preparation method according to claim 43, characterized in that, The fourth insulation time is 3~10 hours.

64. The preparation method according to claim 14, characterized in that, The preparation method includes: (1) The ferrite pre-calcined material, flux, growth inhibitor, heat transfer medium and lattice stabilizer are mixed by ball milling at a speed of 200~600r / min for 12~20h. Solvent is added during the ball milling process, and the mixture is obtained after solid-liquid separation. (2) The mixture obtained in step (1) is subjected to a magnetic field with a magnetic field strength of 6000~10000Oe and a pressure of 15~25MPa to form a preform, then crushed, and then sieved through a 10~100 mesh sieve and dried to obtain magnetic powder with an orientation with a moisture content of 1.2~3.5%. (3) After the initial mixture of lubricant and oriented magnetic powder obtained in step (2) is obtained, the initial mixture is then mixed with binder. The mass ratio of lubricant to oriented magnetic powder is (2~30):(500~3000), and the mass ratio of binder to oriented magnetic powder is (1~25):(500~3000). After being pressed and formed in a magnetic field with a strength of 10000~14000Oe and a pressure of 30~70MPa, the temperature is raised to 300~500℃ at a rate of 3~10℃ / min and held for 0.1~5h. Then, the temperature is raised to 600~800℃ at a rate of 3~8℃ / min and held for 0.1~8h. Then, the temperature is raised to 900~1100℃ at a rate of 2~7℃ / min and held for 0.1~5h. Then, the temperature is raised to 1200~1300℃ at a rate of 0.1~5℃ / min and held for 0.1~12h. Finally, the mixture is cooled in the furnace to obtain dry-pressed permanent magnet ferrite.

65. A magnetic device, characterized in that, The magnetic device includes the dry-pressed permanent magnet ferrite as described in any one of claims 1 to 13.

66. An application of the magnetic device according to claim 65, characterized in that, The magnetic devices are used in automobiles, home appliances, and aerospace.

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