Ferrite magnetic tile and preparation method therefor

Abstract

Provided in the present invention are a ferrite magnetic tile and a preparation method therefor. The preparation method comprises: subjecting a mixed material of a ferrite magnetic powder and a binder to injection molding, and then sintering the resulting product to obtain a ferrite magnetic tile, wherein the sintering temperature is 1150-1240ºC. The ultra-thin magnetic tile having a large radian obtained by means of the preparation method of the present application shows good magnetic performance: the central surface magnetic field intensity is 630-700 Gs, and the magnetic energy product can reach 4.5-5.2 MGOe, and same has a density of 4.8-5.2 g / cm3 and a compressive strength of 480-680 N, which are significantly higher than those of an existing injection-molded permanent magnet ferrite magnet. The ultra-thin magnetic tile having a large radian obtained by means of the preparation method of the present application has less internal dark cracks and basically does not need later grinding machining, thereby reducing the risk of stress damage generated during the machining process and also improving the finished product yield and utilization rate of the material: the finished product yield is not lower than 95%, and the material utilization rate is not lower than 90%, such that the production cost is reduced, and batch production requirements are satisfied.

Description

Ferrite magnetic tile and preparation method thereof Technical Field

[0001] The present application relates to the technical field of permanent magnets, for example, a method for preparing a ferrite magnetic tile, and in particular, to a ferrite magnetic tile and a method for preparing the same. Background Art

[0002] Permanent magnetic materials, also known as hard magnetic materials, maintain constant magnetic properties once magnetized. Commonly used permanent magnetic materials include Alnico, ferrite, rare earth, and various composite permanent magnetic materials. Permanent ferrite is one of the fundamental functional materials for permanent magnet DC motors. It can meet the requirements of motors in various environments, exhibiting high sensitivity and stability. It is widely used in high-power, high-speed, and high-torque motors, such as high-end automotive motors (ABS motors, starter motors, etc.), motorcycle starter motors, household appliances, and power tool motors. To facilitate the formation of motor stators or rotors, permanent ferrites used in motors are mostly manufactured in the form of tiles, also known as tiles. The main dimensional parameters for permanent ferrite tiles include chord length, width, inner and outer arc radii, thickness, and the arc corresponding to the chord length.

[0003] Traditional permanent ferrite tiles are primarily produced using a wet-molding magnetic field forming process. This involves wet-milling ferrite coarse powder to an average particle size below 1.0 μm. This process is then concentrated and dehydrated to produce a fluid ferrite slurry with a solids content of approximately 65 wt%. This slurry is then assembled into a tile-shaped mold using a hydraulic press under magnetic field conditions to form a ferrite blank. The blank is then sintered at high temperature in a sintering furnace to produce a semi-finished tile. This tile is then ground using a grinder to achieve the desired dimensions, including internal and external arcs, chord length, width, and chamfers, to meet the drawing specifications. The wet-molding process is currently the most popular method for producing permanent ferrite tiles, offering advantages such as high production efficiency, stable and reliable performance, and controllable dimensional accuracy. However, tiles produced using this process require numerous grinding cycles, resulting in a high grinding volume and relatively low material utilization. Furthermore, the repeated grinding process can easily generate internal stresses within the tile, resulting in low mechanical strength. Especially for large-radius ultra-thin magnetic tiles (radius greater than 150°, thickness less than 2.0mm), the disadvantages of traditional production processes will be more obvious, the grinding volume will account for a larger proportion, the material utilization rate will be lower, and defects such as corner chipping and cracking during the grinding process of the magnetic tiles will result in a lower yield rate, and the mechanical strength of the product will be so low that it cannot be used at all.

[0004] Ferrite tiles can also be produced using injection molding. The main process includes: mixing and granulating a certain particle size of magnetic powder and resin powder; then injecting the granulated granules into an injection molding machine and heating and melting them to give them good fluidity. In this state, the granules are injected into a tile-shaped metal mold with an oriented magnetic field in a molten state. After cooling, the required tile-shaped injection-molded ferrite device is formed. Traditional injection-molded tile-shaped ferrite has the advantages of net size molding, no need for grinding, high material utilization, and good mechanical strength. It is particularly suitable for processing large-radius ultra-thin tiles. However, the magnetic properties of this process are relatively low, and the maximum magnetic energy product does not exceed 2.5MGOe, which is difficult to meet the needs of related application scenarios.

[0005] CN102136332A discloses a flexible permanent magnetic ferrite material for injection molding and a manufacturing method thereof, belonging to the field of permanent magnetic ferrite materials. The granular material is compounded by mass percentage of 80-92% permanent magnetic ferrite, 3-6% rubber, 2.5-10% plasticizer and 0.1-3% additive; wherein the permanent magnetic ferrite is strontium ferrite Sr 0.6 Fe2O3; rubber includes main rubber and auxiliary rubber, and the main rubber content accounts for 55-95% of the total rubber mass. 0.6 Fe2O3, a permanent ferrite, is compounded with rubber, plasticizers, and additives to form a flexible permanent ferrite material. This material can be made into flexible injection pellets, which can then be injection molded into position sensors. This flexible position sensor, unlike traditional rigid position sensors made from nylon injection pellets, is more durable, convenient, and low-cost.

[0006] CN102351525A discloses a method for manufacturing permanent magnet ferrite powder for injection molding, comprising the following steps: first, uniformly mixing raw materials consisting of iron oxide, A carbonate, a densifier, and a sintering aid, wherein A is one or a mixture of two of Sr, Ba, Pb, and Ca; second, dry-firing the mixed raw materials; then, grinding the fired material; and finally, heat treating. This method for manufacturing permanent magnet ferrite powder for injection molding, due to the addition of a densifier, does not require a molding process, but rather directly fires the mixed dry powder. Furthermore, after dry-firing, the powder can be directly washed and ground into a fine powder without undergoing crushing and / or coarse grinding. This simple process allows for the production of permanent magnet ferrite powder with ideal grain morphology, good filling properties, and high and uniform magnetic properties.

[0007] The currently available ferrite magnetic tiles and their preparation methods have certain defects, and there is a problem that it is difficult to effectively prepare high-performance, large-radian, ultra-thin magnetic tiles. Therefore, it is extremely important to develop and design a new type of ferrite magnetic tile and its preparation method.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The present application provides a ferrite magnetic tile and a preparation method thereof. The ultra-thin magnetic tile with a large curvature obtained by the preparation method described in the present application exhibits excellent magnetic properties, with a central surface magnetism of 630-700 Gs, a magnetic energy product of 4.5-5.2 MGOe, and a density of 4.8-5.2 g / cm 3 The compressive strength is 480~680N, which is significantly higher than that of existing injection-molded permanent ferrite magnets. The ultra-thin magnetic tiles with large curvature obtained by the preparation method described in this application have fewer internal dark cracks and basically do not require subsequent grinding processing, which not only reduces the risk of stress damage during processing, but also improves the yield and utilization rate of materials. The yield is not less than 95%, and the material utilization rate is not less than 90%, thereby reducing production costs and meeting the requirements of mass production.

[0011] In a first aspect, the present application provides a method for preparing a ferrite magnetic tile, the method comprising:

[0012] The mixture of ferrite magnetic powder and binder is injection molded and then sintered to obtain ferrite magnetic tiles;

[0013] The sintering temperature is 1150-1240°C.

[0014] The ultra-thin magnetic tile with a large curvature obtained by the preparation method described in this application exhibits excellent magnetic properties, with a central surface magnetism of 630-700 Gs, a magnetic energy product of 4.5-5.2 MGOe, and a density of 4.8-5.2 g / cm 3 The compressive strength is 480~680N, which is significantly higher than that of existing injection-molded permanent ferrite magnets. The ultra-thin magnetic tiles with large curvature obtained by the preparation method described in this application have fewer internal dark cracks and basically do not require subsequent grinding processing, which not only reduces the risk of stress damage during processing, but also improves the yield and utilization rate of materials. The yield is not less than 95%, and the material utilization rate is not less than 90%, thereby reducing production costs and meeting the requirements of mass production.

[0015] The sintering temperature described in this application is 1150-1240°C, for example, it can be 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C or 1240°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0016] In one embodiment, the mixture further comprises a surface modifier, a coupling agent and a flow aid.

[0017] The surface modifier in this application is used to quickly remove fine magnetic powder and spheroidize the sharp corners of magnetic powder, thereby improving the fluidity of the magnetic powder.

[0018] In one embodiment, based on the mass of the mixed material, the mass fraction of the ferrite powder is 88.3-94.3wt%, the mass fraction of the surface modifier is 0.1-0.9wt%, the mass fraction of the coupling agent is 0.3-1.0wt%, the mass fraction of the binder is 5-9wt%, and the mass fraction of the flow aid is 0.3-0.8wt%.

[0019] In this application, the mass fraction of the ferrite magnetic powder is 88.3-94.3wt%, based on the mass of the mixed material. For example, it can be 88.3wt%, 88.5wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt% or 94.3wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0020] In this application, the mass fraction of the surface modifier is 0.1-0.9wt% based on the mass of the mixed material. For example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt% or 0.9wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0021] In this application, the mass fraction of the coupling agent is 0.3-1.0wt% based on the mass of the mixed material. For example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0022] In this application, the mass fraction of the mixed material is calculated as 100%, and the mass fraction of the binder is 5 to 9wt%, for example, it can be 5wt%, 6wt%, 7wt%, 8wt% or 9wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0023] In this application, the mass fraction of the flow aid is 0.3-0.8wt% based on the mass of the mixed material. For example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt% or 0.9wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0024] In one embodiment, the surface modifier includes any one of phosphoric acid, oxalic acid, acetic acid, and citric acid, or a combination of at least two of them. Typical but non-limiting combinations include a combination of phosphoric acid and oxalic acid, a combination of oxalic acid and acetic acid, a combination of acetic acid and citric acid, or a combination of phosphoric acid, oxalic acid, and acetic acid.

[0025] In one embodiment, the concentration of the surface modifier is 10 to 20 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In one embodiment, the coupling agent includes stearic acid and / or an ester derivative of stearic acid.

[0027] In one embodiment, the ester derivatives of stearic acid include butyl stearate and / or octyl stearate.

[0028] In one embodiment, the flow aid comprises polyamide wax.

[0029] In one embodiment, the binder includes: paraffin wax and / or microcrystalline wax, stearic acid wax, high-density polyethylene and low-density polyethylene. The binder is used to ensure that the embryo obtained by subsequent injection molding maintains a certain strength, thereby preventing the blank from deforming during sintering.

[0030] The paraffin wax described in this application is a solid crystalline product extracted from petroleum, which is composed of a variety of hydrocarbons, mainly normal alkanes, and also contains isoalkanes, cycloalkanes and a small amount of aromatic hydrocarbons; the paraffin wax described in this application includes but is not limited to 60# paraffin wax, and other paraffin waxes not listed are also applicable.

[0031] The paraffin wax in the binder described in this application has two functions: first, it acts as an organic binder to achieve bonding of the ferrite powder, and second, it is used to increase the fluidity of the ferrite powder. When the paraffin wax content in the binder is too low, the fluidity of the mixture of ferrite powder and the binder is poor, making it impossible to perform injection molding normally. When the paraffin wax content in the binder is too high, the porosity of the product after the paraffin wax is removed is too large, resulting in poor strength, and the volume change during sintering is too large, resulting in cracks.

[0032] In this application, microcrystalline wax can be used instead of paraffin wax to obtain better product performance. The microcrystalline wax is also called ozokerite. The main components of microcrystalline wax are cycloalkanes and aromatic hydrocarbons with larger molecular weight and longer carbon chains. Under a microscope, it can be clearly seen that its crystals are much smaller than those of paraffin wax.

[0033] In one embodiment, based on the mass of the binder as 100%, the mass fraction of paraffin wax and / or microcrystalline wax is 50-70wt%, the mass fraction of stearic acid wax is 10-20wt%, the mass fraction of high-density polyethylene is 10-15wt%, and the mass fraction of low-density polyethylene is 10-15wt%.

[0034] In this application, the mass fraction of the binder is calculated as 100%, and the mass fraction of paraffin wax and / or microcrystalline wax is 50-70wt%, for example, it can be 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, 62wt%, 64wt%, 66wt%, 68wt% or 70wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In this application, the mass fraction of the binder is calculated as 10% by mass, and the mass fraction of the stearic acid wax is 10 to 20 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] In this application, the mass fraction of the binder is calculated as 10% by weight, and the mass fraction of high-density polyethylene is 10 to 15% by weight, for example, it can be 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight or 15% by weight, but it is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0037] In this application, the mass fraction of the low-density polyethylene is 10 to 15 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0038] In one embodiment, the method for preparing the mixed material includes: finely grinding ferrite magnetic powder, a surface modifier, a coupling agent and a binder to obtain a mixed material.

[0039] In one embodiment, the mixing includes: heating and mixing the ferrite powder and the surface modifier for the first time to obtain a first mixed powder, then adding a coupling agent and heating and mixing for the second time to obtain a second mixed powder, and further adding a flow aid and a binder and heating and mixing for the third time to obtain a mixed material.

[0040] In one embodiment, the first heating and mixing comprises: taking ferrite magnetic powder, heating it to 80-120° C. while stirring, then adding a surface modifier, and continuing to stir for 5-15 minutes to obtain a first mixed powder;

[0041] The final temperature of the first heating and mixing described in the present application is 80-120°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0042] The stirring time in the first heating mixing described in the present application is 5 to 15 minutes, for example, it can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In one embodiment, the second heating and mixing comprises: heating the first mixed powder to 90-130° C. while stirring, then adding a coupling agent, and continuing stirring for 20-40 minutes to obtain a second mixed powder;

[0044] The terminal temperature of the second heating and mixing described in the present application is 90-130°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0045] The stirring time in the second heating mixing described in the present application is 20 to 40 minutes, for example, it can be 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In one embodiment, the third heating and mixing method includes: adjusting the temperature of the second mixed powder to 80-100° C., then adding a flow aid and a binder, and continuing mixing for 20-40 minutes to obtain a final mixed material;

[0047] The third heating and mixing adjustment temperature in the present application is 80-100°C, for example, it can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] The time for the third heating and mixing in the present application is 20 to 40 minutes, for example, it can be 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In one embodiment, the moisture content of the first mixing powder is not higher than 600 ppm, for example, it can be 600 ppm, 550 ppm, 500 ppm, 450 ppm, 400 ppm, 350 ppm, 300 ppm, 250 ppm, 200 ppm, 150 ppm or 100 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In one embodiment, the moisture content of the second mixing powder is not higher than 900 ppm, for example, it can be 900 ppm, 800 ppm, 700 ppm, 600 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm or 100 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In one embodiment, the method for preparing the ferrite magnetic powder includes: mixing additives into permanent magnet ferrite coarse powder, performing wet ball milling, and obtaining ferrite finely ground magnetic powder with an average particle size of 0.8 to 1.2 μm after drying.

[0052] In one embodiment, the chemical formula of the permanent ferrite coarse powder includes A1-x-y Ca x La y Fe 2n-z Co z O 19 , wherein A includes Sr or any one or a combination of at least two of Sr and Ba, 0.25≤x≤0.45, 0.35≤y≤0.55, 0.25≤z≤0.40, 0.6≤z / y≤0.9 and 5.1≤n≤5.6.

[0053] In the present application, 0.25≤x≤0.45, where x can be, for example, 0.25, 0.27, 0.3, 0.32, 0.35, 0.37, 0.4, 0.42 or 0.45, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In the present application, 0.35≤y≤0.55, where y can be, for example, 0.35, 0.37, 0.4, 0.42, 0.45, 0.47, 0.5, 0.52 or 0.35, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] In the present application, 0.25≤z≤0.40, where z can be, for example, 0.25, 0.27, 0.3, 0.32, 0.35, 0.37 or 0.4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In the present application, 0.6≤z / y≤0.9, z / y can be, for example, 0.6, 0.65, 0.7, 0.75, 0.8, 0.86 or 0.9, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In the present application, 5.1≤n≤5.6, where n can be, for example, 5.1, 5.2, 5.3, 5.4, 5.5 or 5.6, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] In one embodiment, the additive includes SiO2, CaCO3 and H3BO3.

[0059] In one embodiment, the additive further comprises Al2O3, Cr2O3, ZnO and SrCO3.

[0060] In one embodiment, the average particle size of the additive is not higher than 5 μm, for example, it can be 5 μm, 4.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm or 1 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In one embodiment, based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.05-2.0wt%, the mass fraction of CaCO3 is 0.4-2.0wt%, the mass fraction of Al2O3 is 0.1-2.0wt%, the mass fraction of Cr2O3 is 0.1-1.5wt%, the mass fraction of ZnO is 0.1-0.6wt%, the mass fraction of SrCO3 is 0.1-1.0wt%, and the mass fraction of H3BO3 is 0.1-0.8wt%.

[0062] In this application, the total mass of the permanent magnet ferrite coarse powder and the additives is taken as 100%, and the mass fraction of SiO2 is 0.05-2.0wt%, for example, it can be 0.05wt%, 0.07wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt% or 2wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] In this application, the total mass of the permanent magnet ferrite coarse powder and the additive is taken as 100%, and the mass fraction of CaCO3 is 0.4 to 2.0 wt%, for example, it can be 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt% or 2 wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0064] In this application, the total mass of the permanent magnet ferrite coarse powder and the additives is taken as 100%, and the mass fraction of Al2O3 is 0.1 to 2.0 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt% or 2 wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0065] In this application, the total mass of the permanent magnet ferrite coarse powder and the additive is taken as 100%, and the mass fraction of Cr2O3 is 0.1 to 1.5 wt%, for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt% or 1.5 wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0066] In the present application, the total mass of the permanent magnet ferrite coarse powder and the additives is taken as 100%, and the mass fraction of ZnO is 0.1-0.6wt%, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0067] In this application, the total mass of the permanent magnet ferrite coarse powder and the additives is taken as 100%, and the mass fraction of SrCO3 is 0.1 to 1.0 wt%, for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt% or 1 wt%, but it is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0068] In this application, the total mass of the permanent magnet ferrite coarse powder and the additive is taken as 100%, and the mass fraction of H3BO3 is 0.1-0.8wt%, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt% or 0.8wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0069] In one embodiment, the preparation method further comprises mixing and granulation performed sequentially before the injection molding.

[0070] In one embodiment, the mixing temperature is 100-150° C., and the mixing time is 1-3 hours.

[0071] The mixing temperature described in this application is 100-150°C, for example, it can be 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0072] The mixing time described in this application is 1 to 3 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0073] In one embodiment, the average particle size of the mixed material obtained after granulation is 6 to 8 mm, for example, it can be 6 mm, 6.2 mm, 6.4 mm, 6.6 mm, 6.8 mm, 7 mm, 7.2 mm, 7.4 mm, 7.6 mm, 7.8 mm or 8 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] In one embodiment, the injection molding temperature is 100-150°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0075] In one embodiment, the injection molding pressure is 75 to 200 bar, for example, 75 bar, 80 bar, 90 bar, 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar, 160 bar, 170 bar, 180 bar, 190 bar or 200 bar, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0076] In one embodiment, the injection molding is performed in a shoe-shaped molding cavity with a magnetic field.

[0077] In one embodiment, natural cooling is further included between the injection molding and the sintering.

[0078] In one embodiment, the preparation method further includes debinding between the injection molding and the sintering.

[0079] In one embodiment, the degreasing comprises solvent degreasing and thermal degreasing performed sequentially.

[0080] In one embodiment, the solvent degreasing comprises: soaking the embryo body obtained by injection molding in kerosene.

[0081] In this application, most of the paraffin is first removed by long-term immersion in kerosene, which avoids the volatilization of paraffin during sintering and causes excessive and uneven pores, thereby improving the strength of the product. The resulting product has uniform pores and high density, and the density of the defatted embryo is high.

[0082] In the thermal degreasing step of the present application, a process of slowly heating up from a low temperature is adopted to allow the organic binders other than the paraffin to slowly melt and gradually seep out of the surface of the blank obtained by injection molding, thereby avoiding the gasification of these organic substances during the subsequent sintering process and producing a large number of irregular pores, thereby improving the strength of the finished product, ensuring the density of the product, and ultimately obtaining high-density ferrite tiles.

[0083] In one embodiment, the soaking temperature is 40-60° C. and the soaking time is 5-8 hours.

[0084] The soaking temperature described in this application is 40-60°C, for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0085] The soaking time described in this application is 5 to 8 hours, for example, it can be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0086] In one embodiment, the thermal degreasing comprises sequentially heating and keeping the temperature;

[0087] In one embodiment, the heating rate is 10-15°C / min, and the end temperature is 400-800°C.

[0088] The heating rate described in this application is 10 to 15°C / min, for example, it can be 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min or 15°C / min, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0089] The end temperature of the heating described in this application is 400-800°C, for example, it can be 400°C, 500°C, 600°C, 700°C or 800°C, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0090] In one embodiment, the insulation time is 4 to 6 hours, for example, it can be 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours or 6 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0091] In one embodiment, the sintering time is 2 to 6 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0092] The sintering is performed in an air atmosphere.

[0093] As an optional technical solution of the preparation method described in this application, the preparation method includes:

[0094] (1) Adding an additive having an average particle size of not more than 5 μm to a coarse permanent ferrite powder having an average particle size of 4 to 6 μm and then wet-milling the mixture to obtain ferrite powder having an average particle size of 0.8 to 1.2 μm after drying;

[0095] The chemical formula of the permanent ferrite coarse powder includes A 1-x-y Ca x La y Fe 2n-z Co z O 19 , wherein A includes Sr or any one or a combination of at least two of Sr and Ba, 0.25≤x≤0.45, 0.35≤y≤0.55, 0.25≤z≤0.40, 0.6≤z / y≤0.9 and 5.1≤n≤5.6;

[0096] Based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.05-2.0wt%, the mass fraction of CaCO3 is 0.4-2.0wt%, the mass fraction of Al2O3 is 0-2.0wt%, the mass fraction of Cr2O3 is 0-1.5wt%, the mass fraction of ZnO is 0-0.6wt%, the mass fraction of SrCO3 is 0.1-1.0wt%, and the mass fraction of H3BO3 is 0-0.8wt%;

[0097] (2) taking the ferrite powder obtained in step (1), heating it to 80-120° C. while stirring, then adding a surface modifier, and continuing to stir for 5-15 minutes to obtain a first mixed powder; heating the first mixed powder to 90-130° C. while stirring, then adding a coupling agent, and continuing to stir for 20-40 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 80-100° C., then adding a flow aid and a binder, and continuing to mix for 20-40 minutes to obtain a final mixed material;

[0098] Based on the mass of the mixed material, the mass fraction of the ferrite powder is 88.3-94.3 wt %, the mass fraction of the surface modifier is 0.1-0.9 wt %, the mass fraction of the coupling agent is 0.3-1.0 wt %, the mass fraction of the binder is 5-9 wt %, and the mass fraction of the flow aid is 0.3-0.8 wt %;

[0099] Based on the mass of the binder, the mass fraction of paraffin wax and / or microcrystalline wax is 50-70wt%, the mass fraction of stearic acid wax is 10-20wt%, the mass fraction of high-density polyethylene is 10-15wt%, and the mass fraction of low-density polyethylene is 10-15wt%;

[0100] (3) kneading the mixture obtained in step (2) at 100-150° C. for 1-3 hours, and granulating to obtain permanent magnet ferrite particles with an average particle size of 6-8 mm;

[0101] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 100 to 150° C. and a pressure of 75 to 200 bar, and then naturally cooling to obtain an embryonic body;

[0102] (5) Soaking the embryo body obtained in step (4) in kerosene at a temperature of 40 to 60° C. for 5 to 8 hours for solvent degreasing, then heating to 400 to 800° C. at a rate of 10 to 15° C. / min and keeping the temperature for 4 to 6 hours for thermal degreasing to obtain a degreased embryo body;

[0103] (6) Sintering the degreased embryo obtained in step (5) at 1150-1240° C. for 2-6 hours in an air atmosphere to obtain a ferrite magnetic tile.

[0104] In a second aspect, the present application provides a ferrite magnetic tile, which is obtained by the preparation method described in the first aspect.

[0105] In one embodiment, the ferrite magnetic tile has an arc greater than 150° and a thickness no greater than 2.0 mm.

[0106] The curvature of the ferrite magnetic tile described in this application is greater than 150°, for example, it can be 151°, 155°, 156°, 157°, 158°, 159°, 160°, 161°, 162°, 163°, 164°, 165°, 167°, 168°, 170°, 172° or 175°, but it is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0107] The thickness of the ferrite magnetic tile described in this application is not higher than 2.0 mm, for example, it can be 2.0 mm, 1.9 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm or 1.0 mm, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0108] In one embodiment, the magnetic energy product of the ferrite magnetic tile is 4.5 to 5.2 MGOe, for example, 4.5 MGOe, 4.6 MGOe, 4.7 MGOe, 4.8 MGOe, 4.9 MGOe, 5 MGOe, 5.1 MGOe, or 5.2 MGOe, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0109] Compared with the related art, this application has the following beneficial effects:

[0110] The ultra-thin magnetic tile with a large curvature obtained by the preparation method described in this application exhibits excellent magnetic properties, with a central surface magnetism of 630-700 Gs, a magnetic energy product of 4.5-5.2 MGOe, and a density of 4.8-5.2 g / cm 3 The compressive strength is 480~680N, which is significantly higher than that of existing injection-molded permanent ferrite magnets. The ultra-thin magnetic tiles with large curvature obtained by the preparation method described in this application have fewer internal dark cracks and basically do not require subsequent grinding processing, which not only reduces the risk of stress damage during processing, but also improves the yield and utilization rate of materials. The yield is not less than 95%, and the material utilization rate is not less than 90%, thereby reducing production costs and meeting the requirements of mass production.

[0111] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0112] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0113] FIG1 is a schematic structural diagram of the ferrite magnetic tile prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0114] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0115] Example 1

[0116] The present application provides a method for preparing a ferrite magnetic tile as shown in FIG1 , the method comprising:

[0117] (1) Additives with an average particle size of 3 μm were mixed into coarse permanent ferrite powder with an average particle size of 5 μm, and the mixture was wet-milled. After drying, ferrite powder with an average particle size of 0.9 μm was obtained.

[0118] The chemical formula of the permanent ferrite coarse powder includes Sr 0.25 Ca 0.3 La 0.45 Fe 11.3 Co 0.32 O 19 , the additives are SiO2, CaCO3 and H3BO3, based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.5wt%, the mass fraction of CaCO3 is 1.5wt%, and the mass fraction of H3BO3 is 0.4wt%;

[0119] (2) taking the ferrite powder obtained in step (1), heating it to 85°C while stirring, then adding 15% phosphoric acid, and continuing to stir for 10 minutes to obtain a first mixed powder; heating the first mixed powder to 100°C while stirring, then adding stearic acid, and continuing to stir for 30 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 90°C, then adding polyamide wax and a binder, and continuing to mix for 20 minutes to obtain a final mixed material;

[0120] Based on the mass of the mixed material, the mass fraction of the ferrite magnetic powder is 93wt%, the mass fraction of 15% concentration phosphoric acid is 0.5wt%, the mass fraction of stearic acid is 0.5wt%, the mass fraction of the binder is 5.6wt%, and the mass fraction of the polyamide wax is 0.4wt%;

[0121] Based on the mass of the binder as 100%, the mass fraction of paraffin in the binder is 60wt%, the mass fraction of stearic acid wax is 10wt%, the mass fraction of high-density polyethylene is 15wt%, and the mass fraction of low-density polyethylene is 15wt%;

[0122] (3) kneading the mixture obtained in step (2) at 120° C. for 2 h, and granulating to obtain permanent magnet ferrite particles with an average particle size of 7 mm;

[0123] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 140° C. and a pressure of 180 bar, and then naturally cooling to obtain an embryonic body;

[0124] (5) Soaking the embryo obtained in step (4) in kerosene at a temperature of 50° C. for 8 h for solvent degreasing, then heating to 700° C. at a rate of 12° C. / min and keeping the temperature for 6 h for thermal degreasing to obtain a degreased embryo;

[0125] (6) The degreased embryo obtained in step (5) is sintered at 1240° C. for 5 h in an air atmosphere to obtain a ferrite magnetic tile.

[0126] Example 2

[0127] The present application provides a method for preparing a ferrite magnetic tile, the method comprising:

[0128] (1) A permanent magnet ferrite powder having an average particle size of 4 μm is mixed with an additive having an average particle size of 2 μm, and then wet-milled. After drying, ferrite powder having an average particle size of 0.8 μm is obtained;

[0129] The chemical formula of the permanent ferrite coarse powder includes Sr 0.20 Ca 0.28 La 0.52 Fe11.4 Co 0.30 O 19 The additives are SiO2, CaCO3, H3BO3, ZnO and Al2O3. Based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.6wt%, the mass fraction of CaCO3 is 1.3wt%, the mass fraction of H3BO3 is 0.3wt%, the mass fraction of ZnO is 0.2wt% and the mass fraction of Al2O3 is 0.4wt%;

[0130] (2) taking the ferrite powder obtained in step (1), heating it to 85° C. while stirring, then adding 15% citric acid, and continuing to stir for 10 minutes to obtain a first mixed powder; heating the first mixed powder to 100° C. while stirring, then adding butyl stearate, and continuing to stir for 30 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 90° C., then adding polyamide wax and a binder, and continuing to mix for 20 minutes to obtain a final mixed material;

[0131] Based on the mass of the mixed material, the mass fraction of the ferrite magnetic powder is 91wt%, the mass fraction of 15% concentration of citric acid is 0.8wt%, the mass fraction of butyl stearate is 0.4wt%, the mass fraction of the binder is 7.3wt%, and the mass fraction of the polyamide wax is 0.5wt%;

[0132] Based on the mass of the binder as 100%, the mass fraction of paraffin in the binder is 60wt%, the mass fraction of stearic acid wax is 15wt%, the mass fraction of high-density polyethylene is 10wt%, and the mass fraction of low-density polyethylene is 10wt%;

[0133] (3) kneading the mixture obtained in step (2) at 120° C. for 2 h, and granulating to obtain permanent magnet ferrite particles with an average particle size of 7 mm;

[0134] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 140° C. and a pressure of 180 bar, and then naturally cooling to obtain an embryonic body;

[0135] (5) Soaking the embryo obtained in step (4) in kerosene at a temperature of 50°C for 8 hours for solvent degreasing, then heating to 800°C at a rate of 12°C / min and keeping the temperature for 6 hours for thermal degreasing to obtain a degreased embryo;

[0136] (6) The degreased embryo obtained in step (5) is sintered at 1240° C. for 6 h in an air atmosphere to obtain a ferrite magnetic tile.

[0137] Example 3

[0138] The present application provides a method for preparing a ferrite magnetic tile, the method comprising:

[0139] (1) A permanent magnet ferrite powder having an average particle size of 6 μm is mixed with an additive having an average particle size of 5 μm, and then wet-milled. After drying, ferrite powder having an average particle size of 1.2 μm is obtained;

[0140] The chemical formula of the permanent ferrite coarse powder includes Sr 0.15 Ca 0.35 La 0.50 Fe 11.4 Co 0.26 O 19 The additives are SiO2, CaCO3, H3BO3 and Cr2O3. Based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.4wt%, the mass fraction of CaCO3 is 1.8wt%, the mass fraction of H3BO3 is 0.2wt% and the mass fraction of Cr2O3 is 0.1wt%;

[0141] (2) The ferrite powder obtained in step (1) was heated to 85° C. while stirring, and then 15% acetic acid was added and stirred for 10 minutes to obtain a first mixed powder; the first mixed powder was heated to 100° C. while stirring, and then octyl stearate was added and stirred for 30 minutes to obtain a second mixed powder; the temperature of the second mixed powder was adjusted to 90° C., and then polyamide wax and a binder were added and mixed for 20 minutes to obtain a final mixed material;

[0142] Based on the mass of the mixed material, the mass fraction of the ferrite magnetic powder is 94wt%, the mass fraction of 15% acetic acid is 0.4wt%, the mass fraction of octyl stearate is 0.3wt%, the mass fraction of the binder is 5wt%, and the mass fraction of the polyamide wax is 0.3wt%;

[0143] Based on the mass of the binder as 100%, the mass fraction of paraffin in the binder is 55wt%, the mass fraction of stearic acid wax is 15wt%, the mass fraction of high-density polyethylene is 15wt%, and the mass fraction of low-density polyethylene is 15wt%;

[0144] (3) kneading the mixture obtained in step (2) at 120° C. for 2 h, and granulating to obtain permanent magnet ferrite particles with an average particle size of 7 mm;

[0145] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 140° C. and a pressure of 180 bar, and then naturally cooling to obtain an embryonic body;

[0146] (5) Soaking the embryo obtained in step (4) in kerosene at a temperature of 50°C for 8 hours for solvent degreasing, then heating to 800°C at a rate of 12°C / min and keeping the temperature for 6 hours for thermal degreasing to obtain a degreased embryo;

[0147] (6) The degreased embryo obtained in step (5) is sintered at 1240° C. for 6 h in an air atmosphere to obtain a ferrite magnetic tile.

[0148] Example 4

[0149] The present application provides a method for preparing a ferrite magnetic tile, the method comprising:

[0150] (1) A permanent magnet ferrite powder having an average particle size of 5 μm is mixed with an additive having an average particle size of 1 μm, and then wet-milled. After drying, ferrite powder having an average particle size of 0.9 μm is obtained;

[0151] The chemical formula of the permanent ferrite coarse powder includes Sr 0.25 Ca 0.3 La 0.45 Fe 11.3 Co 0.32 O 19 , the additives are SiO2, CaCO3 and H3BO3, based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.5wt%, the mass fraction of CaCO3 is 1.5wt%, and the mass fraction of H3BO3 is 0.4wt%;

[0152] (2) taking the ferrite powder obtained in step (1), heating it to 80°C while stirring, then adding 15% phosphoric acid, and continuing to stir for 15 minutes to obtain a first mixed powder; heating the first mixed powder to 90°C while stirring, then adding stearic acid, and continuing to stir for 40 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 80°C, then adding polyamide wax and a binder, and continuing to mix for 40 minutes to obtain a final mixed material;

[0153] Based on the mass of the mixed material, the mass fraction of the ferrite magnetic powder is 93wt%, the mass fraction of 15% concentration phosphoric acid is 0.5wt%, the mass fraction of stearic acid is 0.5wt%, the mass fraction of the binder is 5.6wt%, and the mass fraction of the polyamide wax is 0.4wt%;

[0154] Based on the mass of the binder as 100%, the mass fraction of paraffin in the binder is 60wt%, the mass fraction of stearic acid wax is 10wt%, the mass fraction of high-density polyethylene is 15wt%, and the mass fraction of low-density polyethylene is 15wt%;

[0155] (3) kneading the mixture obtained in step (2) at 100° C. for 3 h, and granulating to obtain permanent magnet ferrite particles with an average particle size of 8 mm;

[0156] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 100° C. and a pressure of 200 bar, and then naturally cooling to obtain an embryonic body;

[0157] (5) Soaking the embryo obtained in step (4) in kerosene at a temperature of 40°C for 7 hours for solvent degreasing, then heating to 400°C at a rate of 10°C / min and keeping the temperature for 6 hours for thermal degreasing to obtain a degreased embryo;

[0158] (6) The degreased embryo obtained in step (5) is sintered at 1150° C. for 6 h in an air atmosphere to obtain a ferrite magnetic tile.

[0159] Example 5

[0160] The present application provides a method for preparing a ferrite magnetic tile, the method comprising:

[0161] (1) Additives with an average particle size of 2 μm are mixed into coarse permanent ferrite powder with an average particle size of 5 μm, followed by wet ball milling, and drying to obtain ferrite powder with an average particle size of 1 μm;

[0162] The chemical formula of the permanent ferrite coarse powder includes Sr 0.20 Ca 0.28 La 0.52 Fe 11.4 Co 0.30 O 19 , the additives are SiO2, CaCO3, H3BO3, ZnO and Al2O3, based on the total mass of the permanent magnet ferrite coarse powder and the additives, the mass fraction of SiO2 is 0.6wt%, the mass fraction of CaCO3 is 1.3wt%, the mass fraction of H3BO3 is 0.3wt%, the mass fraction of ZnO is 0.2wt% and the mass fraction of Al2O3 is 0.4wt%;

[0163] (2) taking the ferrite powder obtained in step (1), heating it to 120° C. while stirring, then adding 15% citric acid, and continuing to stir for 5 minutes to obtain a first mixed powder; heating the first mixed powder to 130° C. while stirring, then adding butyl stearate, and continuing to stir for 20 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 100° C., then adding polyamide wax and a binder, and continuing to mix for 20 minutes to obtain a final mixed material;

[0164] Based on the mass of the mixed material, the mass fraction of the ferrite magnetic powder is 91wt%, the mass fraction of 15% concentration of citric acid is 0.8wt%, the mass fraction of butyl stearate is 0.4wt%, the mass fraction of the binder is 7.3wt%, and the mass fraction of the polyamide wax is 0.5wt%;

[0165] Based on the mass of the binder as 100%, the mass fraction of paraffin in the binder is 60wt%, the mass fraction of stearic acid wax is 15wt%, the mass fraction of high-density polyethylene is 10wt%, and the mass fraction of low-density polyethylene is 10wt%;

[0166] (3) kneading the mixture obtained in step (2) at 150° C. for 1 hour, and granulating to obtain permanent magnet ferrite particles with an average particle size of 6 mm;

[0167] (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped mold cavity at a temperature of 150° C. and a pressure of 75 bar, and then naturally cooling to obtain an embryonic body;

[0168] (5) Soaking the embryo obtained in step (4) in kerosene at a temperature of 60° C. for 5 h for solvent degreasing, then heating to 800° C. at a rate of 15° C. / min and keeping the temperature for 4 h for thermal degreasing to obtain a degreased embryo;

[0169] (6) The degreased embryo obtained in step (5) is sintered at 1200° C. for 4 h in an air atmosphere to obtain a ferrite magnetic tile.

[0170] Example 6

[0171] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that the injection molding temperature in step (4) is 80°C.

[0172] Example 7

[0173] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that the injection molding temperature in step (4) is 180°C.

[0174] Example 8

[0175] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that step (5) of immersing the embryo obtained in step (4) in kerosene at a temperature of 50° C. for 8 hours for solvent degreasing is omitted.

[0176] Example 9

[0177] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that the step (5) of heating to 700°C at a rate of 12°C / min. and then keeping warm for 6 hours for thermal degreasing is replaced by directly keeping warm at 400-800°C for 4-6 hours for thermal degreasing without performing a heating process.

[0178] Comparative Example 1

[0179] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that the sintering temperature in step (6) is 1050°C.

[0180] Comparative Example 2

[0181] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that the sintering temperature in step (6) is 1300°C.

[0182] Comparative Example 3

[0183] The present application provides a method for preparing ferrite magnetic tiles, which is the same as Example 1 except that steps (5) and (6) are omitted.

[0184] Comparative Example 4

[0185] The present application provides a method for preparing a ferrite magnetic tile, the preparation method comprising: mixing a mixture of coarse permanent ferrite powder having an average particle size of 0.8 to 1.2 μm and a ball milling additive, and then forming, sintering, and grinding the mixture in a magnetic field to obtain a ferrite magnetic tile having the same size and specifications as Example 1;

[0186] The permanent magnet ferrite coarse powder is Sr 0.15 Ca 0.35 La 0.50 Fe 11.4 Co 0.26 O 19 The ball milling additive is a mixture of SiO2, CaCO3, H3BO3 and Cr2O3, wherein the mass fraction of SiO2 in the mixture is 0.4wt%, the mass fraction of CaCO3 is 1.8wt%, the mass fraction of H3BO3 is 0.5wt%, and the mass fraction of Cr2O3 is 0.4wt%.

[0187] The central surface magnetism, magnetic energy product, density, compressive strength, yield rate and material utilization rate of the ferrite magnetic tiles in Examples 1 to 9 and Comparative Examples 1 to 4 were tested, and the results are shown in Table 1.

[0188] The center surface magnetism test method is as follows: the center surface magnetism of the magnetic tile refers to the surface magnetic flux intensity at the center position of the inner arc of the finished magnetic tile tested by a general gauss meter;

[0189] The magnetic energy product is tested by grinding a square sample from the middle of the magnetic tile and measuring the demagnetization curve of the magnet using a BH comprehensive tester to obtain the magnetic energy product of the material.

[0190] The density test method is as follows: the density of the magnetic tile is measured by using a kerosene densitometer and a water displacement method to test the density of the magnet;

[0191] The compressive strength test method is as follows: the compressive strength of the magnetic tile is tested by using a universal testing machine to test the compressive strength of the finished magnetic tile;

[0192] The test method of the yield rate is as follows: the yield rate of magnetic tile products refers to the number of qualified products in a batch of products divided by the total number of products in the batch and then multiplied by 100%;

[0193] The testing method of the material utilization rate is as follows: the material utilization rate of the magnetic tile product refers to the mass of the finished magnetic tile divided by the mass of the corresponding magnetic powder in the formed blank magnetic tile multiplied by 100%.

[0194] Table 1

[0195] From Table 1, we can get:

[0196] (1) The ferrite magnetic tiles prepared in Examples 1 to 5 exhibit excellent magnetic properties, with a central surface magnetism of 630 to 700 Gs, a magnetic energy product of 4.5 to 5.2 MGOe, and a density of 4.8 to 5.2 g / cm 3 , compressive strength is 480~680N;

[0197] (2) By comparing Example 1 with Examples 6 and 7, it can be seen that the temperature of injection molding in step (4) of the present application will affect the performance and strength of the ferrite magnetic tile; when the temperature of injection molding is low, it will lead to poor fluidity of the magnetic powder, poor orientation during injection molding, insufficient molding of the prepared ferrite magnetic tile, poor surface quality, resulting in poor performance of the prepared ferrite magnetic tile and decreased compressive strength; when the temperature of injection molding is high, it will cause thermal decomposition of the binder part, and it is also easy to cause thermal damage and burning, thereby affecting the performance and compressive strength of the ferrite magnetic tile obtained by injection molding;

[0198] (3) By comparing Example 1 with Example 8, it can be seen that the solvent degreasing in the present application affects the performance of the ferrite magnetic tile. This is because in the present application, most of the paraffin is removed by long-term immersion in kerosene, which avoids the volatilization of paraffin during sintering and causes excessive and uneven pores, thereby improving the strength of the product. The obtained product has uniform pores and high density, and the density of the embryo after degreasing is high, thereby improving the overall material utilization rate and yield rate.

[0199] (4) By comparing Example 1 with Example 9, it can be seen that the heating process in the thermal degreasing step of the present application will affect the performance of the ferrite magnetic tile; when the heating process in the thermal degreasing step is omitted and the heat preservation treatment is directly performed, the performance of the ferrite magnetic tile will be reduced. This is because in the thermal degreasing step of the present application, by adopting a process of slowly heating from a low temperature, the organic binder other than the paraffin is slowly melted and gradually seeps out of the surface of the embryo obtained by injection molding, thereby avoiding the gasification of these organic substances in the subsequent sintering process and generating a large number of irregular pores, thereby improving the strength of the finished product and ensuring the density of the product, thereby ultimately obtaining a high-density ferrite magnetic tile;

[0200] (5) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the sintering temperature in step (6) of the present application will affect the performance of the ferrite magnetic tile; when the sintering temperature is too low, the performance of the ferrite magnetic tile will be reduced. This is because when the sintering temperature is too low, the structure of the prepared ferrite magnetic tile is not firm, the size is unstable and the surface quality is poor; when the sintering temperature is too high, the performance of the ferrite magnetic tile will be reduced. This is because when the sintering temperature is too high, the prepared ferrite magnetic tile will be thermally deformed, and it is difficult to obtain a ferrite magnetic tile that meets the size requirements. It will also cause the surface to melt or burn, resulting in surface quality problems such as bubbles, holes or burn marks;

[0201] (6) By comparing Example 1 with Comparative Example 3, it can be seen that step (5) and step (6) in the preparation method described in the present application will affect the performance of the ferrite magnetic tile; in the present application, most of the paraffin is first removed by long-term immersion in kerosene, thereby avoiding the volatilization of paraffin during sintering to cause excessive and uneven pores, thereby improving the strength of the product, and the pores of the obtained product are uniform, the density is high, and the density of the embryo after degreasing is high; then, in the hot degreasing step, by adopting a process of slowly heating from a low temperature, the organic binder other than the paraffin is slowly melted and gradually seeps out of the surface of the embryo obtained by injection molding, thereby avoiding the gasification of these organic substances during the subsequent sintering process to produce a large number of irregular pores, thereby improving the strength of the manufactured product, ensuring the density of the product, and finally obtaining a high-density ferrite magnetic tile;

[0202] (7) By comparing Example 1 with Comparative Example 4, it can be seen that the performance of the ferrite magnetic tile obtained by the preparation method described in this application is significantly higher than that of the existing injection-molded permanent ferrite magnet.

[0203] In summary, the ultra-thin magnetic tile with a large curvature obtained by the preparation method described in this application exhibits excellent magnetic properties, with a central surface magnetism of 630-700 Gs, a magnetic energy product of 4.5-5.2 MGOe, and a density of 4.8-5.2 g / cm 3The compressive strength is 480~680N, which is significantly higher than that of existing injection-molded permanent ferrite magnets. The ultra-thin magnetic tiles with large curvature obtained by the preparation method described in this application have fewer internal dark cracks and basically do not require subsequent grinding processing, which not only reduces the risk of stress damage during processing, but also improves the yield and utilization rate of materials. The yield is not less than 95%, and the material utilization rate is not less than 90%, thereby reducing production costs and meeting the requirements of mass production.

[0204] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a ferrite magnetic tile, comprising: The mixture of ferrite magnetic powder and binder is injection molded and then sintered to obtain ferrite magnetic tiles; The sintering temperature is 1150-1240°C.

2. The preparation method according to claim 1, wherein The mixed material also includes a surface modifier, a coupling agent and a flow aid.

3. The preparation method according to claim 2, wherein Based on the mass of the mixed material, the mass fraction of the ferrite powder is 88.3-94.3wt%, the mass fraction of the surface modifier is 0.1-0.9wt%, the mass fraction of the coupling agent is 0.3-1.0wt%, the mass fraction of the binder is 5-9wt%, and the mass fraction of the flow aid is 0.3-0.8wt%.

4. The preparation method according to claim 2 or 3, wherein The surface modifier includes any one of phosphoric acid, oxalic acid, acetic acid, and citric acid, or a combination of at least two thereof; Optionally, the concentration of the surface modifier is 10-20 wt %.

5. The preparation method according to any one of claims 2 to 4, wherein: The coupling agent includes stearic acid and / or ester derivatives of stearic acid; Optionally, the ester derivatives of stearic acid include butyl stearate and / or octyl stearate.

6. The preparation method according to any one of claims 2 to 5, wherein: The flow aid comprises polyamide wax; Optionally, the binder includes: paraffin wax and / or microcrystalline wax, stearic acid wax, high-density polyethylene and low-density polyethylene; Optionally, based on the mass of the binder, the mass fraction of paraffin and / or microcrystalline wax is 50-70wt%, the mass fraction of stearic acid wax is 10-20wt%, the mass fraction of high-density polyethylene is 10-15wt%, and the mass fraction of low-density polyethylene is 10-15wt%.

7. The preparation method according to any one of claims 2 to 6, wherein: The method for preparing the mixed material comprises: mixing ferrite magnetic powder, a surface modifier, a coupling agent and a binder to obtain a mixed material; Optionally, the mixing includes: heating and mixing the ferrite powder and the surface modifier for the first time to obtain a first mixed powder, then adding a coupling agent and heating and mixing for the second time to obtain a second mixed powder, and further adding a flow aid and a binder and heating and mixing for the third time to obtain a mixed material; Optionally, the first heating and mixing comprises: taking ferrite magnetic powder, heating it to 80-120° C. while stirring, then adding a surface modifier, and continuing to stir for 5-15 minutes to obtain a first mixed powder; Optionally, the second temperature-raising mixing comprises: heating the first mixed powder to 90-130° C. while stirring, then adding a coupling agent, and continuing stirring for 20-40 minutes to obtain a second mixed powder; Optionally, the third heating and mixing method includes: adjusting the temperature of the second mixed powder to 80-100° C., then adding a flow aid and a binder, and continuing to mix for 20-40 minutes to obtain a final mixed material; Optionally, the moisture content of the first mixed powder is not higher than 600 ppm; Optionally, the moisture content of the second mixed powder is not higher than 900 ppm.

8. The preparation method according to any one of claims 1 to 7, wherein The method for preparing the ferrite magnetic powder comprises: mixing an additive into a permanent ferrite coarse powder with an average particle size of 4 to 6 μm, and then wet ball milling the mixture, and drying the mixture to obtain a ferrite magnetic powder with an average particle size of 0.8 to 1.2 μm; Optionally, the chemical formula of the permanent ferrite coarse powder includes A 1-x-y Ca x La y Fe 2n-z Co z O 19 , wherein A includes Sr or any one or a combination of at least two of Sr and Ba, 0.25≤x≤0.45, 0.35≤y≤0.55, 0.25≤z≤0.40, 0.6≤z / y≤0.9 and 5.1≤n≤5.6; Optionally, the additive includes SiO2, CaCO3 and H3BO3; Optionally, the additive further comprises Al2O3, Cr2O3, ZnO and SrCO3; Optionally, the average particle size of the additive is not greater than 5 μm; Optionally, based on the total mass of the permanent magnet ferrite coarse powder and the additive, the mass of SiO2 is The mass fraction is 0.05~2.0wt%, the mass fraction of CaCO3 is 0.4~2.0wt%, the mass fraction of Al2O3 is 0~2.0wt%, the mass fraction of Cr2O3 is 0~1.5wt%, the mass fraction of ZnO is 0.1~0.6wt%, the mass fraction of SrCO3 is 0.1~1.0wt%, and the mass fraction of H3BO3 is 0.1~0.8wt%.

9. The preparation method according to any one of claims 1 to 3, wherein: The preparation method further comprises mixing and granulation performed in sequence before the injection molding; Optionally, the mixing temperature is 100-150° C. and the mixing time is 1-3 hours; Optionally, the average particle size of the mixed material obtained after the granulation is 6 to 8 mm.

10. The preparation method according to any one of claims 1 to 9, wherein: The injection molding temperature is 100-150°C; Optionally, the injection molding pressure is 75 to 200 bar; Optionally, the injection molding is performed in a tile-shaped molding cavity with a magnetic field; Optionally, natural cooling is further included between the injection molding and the sintering.

11. The preparation method according to any one of claims 1 to 10, wherein: The preparation method further comprises degreasing between the injection molding and the sintering; Optionally, the degreasing includes solvent degreasing and thermal degreasing performed sequentially; Optionally, the solvent degreasing comprises: soaking the embryo body obtained by injection molding in kerosene; Optionally, the soaking temperature is 40-60°C and the soaking time is 5-8h; Optionally, the thermal degreasing includes sequentially heating and keeping warm; Optionally, the heating rate is 10-15°C / min, and the end temperature is 400-800°C; Optionally, the insulation time is 4 to 6 hours.

12. The preparation method according to any one of claims 1 to 11, wherein: The sintering time is 2 to 6 hours; The sintering is performed in an air atmosphere.

13. The preparation method according to any one of claims 1 to 12, comprising: (1) Additives having an average particle size of no more than 5 μm are mixed into coarse permanent ferrite powder having an average particle size of 4 to 6 μm, and then wet-milled to obtain ferrite powder having an average particle size of 0.8 to 1.2 μm after drying; The chemical formula of the permanent ferrite coarse powder includes A 1-x-y Ca x La y Fe 2n-z Co z O 19 , wherein A includes Sr or any one or a combination of at least two of Sr and Ba, 0.25≤x≤0.45, 0.35≤y≤0.55, 0.25≤z≤0.40, 0.6≤z / y≤0.9 and 5.1≤n≤5.6; Taking the total mass of the permanent magnet ferrite coarse powder and the additive as 100%, the mass fraction of SiO2 is 0.05-2.0wt%, the mass fraction of CaCO3 is 0.4-2.0wt%, the mass fraction of Al2O3 is 0-2.0wt%, the mass fraction of Cr2O3 is 0-1.5wt%, the mass fraction of ZnO is 0-0.6wt%, the mass fraction of SrCO3 is 0.1-1.0wt%, and the mass fraction of H3BO3 is 0-0.8wt%; (2) taking the ferrite powder obtained in step (1), heating it to 80-120° C. while stirring, then adding a surface modifier, and continuing to stir for 5-15 minutes to obtain a first mixed powder; heating the first mixed powder to 90-130° C. while stirring, then adding a coupling agent, and continuing to stir for 20-40 minutes to obtain a second mixed powder; adjusting the temperature of the second mixed powder to 80-100° C., then adding a flow aid and a binder, and continuing to mix for 20-40 minutes to obtain a final mixed material; Based on the mass of the mixed material, the mass fraction of the ferrite powder is 88.3-94.3wt%, the mass fraction of the surface modifier is 0.1-0.9wt%, the mass fraction of the coupling agent is 0.3-1.0wt%, the mass fraction of the binder is 5-9wt%, and the mass fraction of the flow aid is 0.3-0.8wt%; Based on the mass of the binder, the mass fraction of paraffin wax and / or microcrystalline wax is 50-70wt%, the mass fraction of stearic acid wax is 10-20wt%, the mass fraction of high-density polyethylene is 10-15wt%, and the mass fraction of low-density polyethylene is 10-15wt%; (3) kneading the mixture obtained in step (2) at 100-150° C. for 1-3 hours, and granulating to obtain permanent magnet ferrite particles with an average particle size of 6-8 mm; (4) injecting the permanent magnet ferrite particles obtained in step (3) into a tile-shaped molding cavity at a temperature of 100 to 150° C. and a pressure of 75 to 200 bar, and obtaining an embryo after natural cooling; (5) soaking the embryo obtained in step (4) in kerosene at a temperature of 40 to 60° C. for 5 to 8 hours for solvent degreasing, then heating to 400 to 800° C. at a rate of 10 to 15° C. / min and keeping the temperature for 4 to 6 hours for thermal degreasing to obtain a degreased embryo; (6) Sintering the degreased embryo obtained in step (5) at 1150-1240° C. for 2-6 hours in an air atmosphere to obtain a ferrite tile.

14. A ferrite magnetic tile, wherein: The ferrite magnetic tile is obtained by the preparation method described in any one of claims 1 to 13.

15. The ferrite magnetic tile according to claim 14, wherein: The ferrite magnetic tile has an arc greater than 150° and a thickness not greater than 2.0 mm; Optionally, the magnetic energy product of the ferrite magnetic tile is 4.5-5.2 MGOe.

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