Soft magnetic ferrite core powder mixing system capable of uniformly mixing materials

Abstract

The invention discloses a soft magnetic ferrite core powder mixing system capable of uniformly mixing materials, and mainly relates to the technical field of soft magnetic ferrite core processes. Comprising a first-order unit, the first-order unit comprises a first-order tank, an additive and part of ZnO are mixed on the basis of the first-order tank, the adding amount of ZnO accounts for 30%-60% of the total amount of components, the additive at least comprises SiO2, SiO2 is preferentially added, and a ZnO premix is obtained; the second-order unit comprises a second-order tank, and the ZnO premix, the rest ZnO, the rest auxiliary materials and Fe2O3 are mixed on the basis of the second-order tank, so that the premix is obtained. The method has the beneficial effects that the uniform distribution of the raw materials with large component difference on the microscopic scale can be effectively improved, the segregation phenomenon caused by the density or granularity difference of the raw materials is avoided, the agglomeration problem is solved, the mixing efficiency is improved, the time consumption of the ball milling process is reduced, and the premise is provided for improving the sintering quality.

Description

Technical Field

[0001] The invention relates to the field of soft ferrite core technology, in particular to a uniformly mixed soft ferrite core powder material mixing system. Background Art

[0002] Soft ferrite cores are mainly composed of metal oxides. Based on different types of soft ferrite core materials, the raw material components are different. For example, manganese zinc ferrite (Mn-Zn Ferrite) and nickel zinc ferrite (Ni-Zn Ferrite) are based on iron oxide (Fe2O3, 50%-70%) as the main component, and are matched with manganese zinc oxide (MnO, 20%-30%) (ZnO, 10%-20%) or nickel zinc oxide (NiO, 20%-30%) (ZnO, 15%-25%) powder. In addition, a small amount of additives is required, including copper oxide (CuO), cobalt oxide (CoO), silicon oxide (SiO2), and calcium oxide (CaO). Usually, the amount of each additive added does not exceed 1%-2%. Therefore, the difference in the raw material components is large, and mixing is a process problem.

[0003] In the production process of soft ferrite cores, the mixing of Fe2O3 powder and other raw materials (such as Mn3O4, ZnO, etc.) is a key step. The performance of ferrite products mainly depends on two aspects: internal factors, such as the purity and composition of raw materials, which affect the progress of the reaction, crystal growth and uniformity of the microstructure; external factors, specifically the various parameters of the preparation process, which affect the performance of the final product. Among them, for the internal factors, that is, the factors of the raw materials themselves, excluding the quality management of the raw materials themselves, the mixing effect of the raw materials has an important influence on the performance of the final product.

[0004] In the existing process, ball mills (mainstream) and sand mills are mainly used to mix and grind raw materials. However, due to the huge difference in the components (except calcium oxide, which is added after the ball mill, other raw material components and additives are added before the ball mill), there are many problems after the powder directly enters the ball mill, including:

[0005] First, soft ferrite cores have very high requirements for material uniformity. If various powders are directly put into the ball mill, uneven mixing may occur during the ball milling process due to the different physical properties of different powders such as density and particle size. For example, the particle sizes of iron oxide powder and zinc oxide, nickel oxide, etc. are inconsistent, which may cause local composition deviation during ball milling.

[0006] Second, some powder raw materials tend to agglomerate, and these agglomerates may be difficult to completely break up during the ball milling process, which ultimately affects the performance of the product.

[0007] Third, after the raw materials are weighed, they are fed into the ball mill for mixed grinding. In the initial stage of ball milling, the powder piles of different components are only ground separately, rather than efficiently mixing the powders of different components. This will prolong the time required for the ball mill to reach a uniform mixing state, resulting in prolonged ball milling time and poor consistency in the magnetic properties of the final product.

[0008] In some more advanced production processes, a pre-mixing process has been added before ball milling. For example, TDK, FDK, and Ferroxcube (Philips's magnetic material brand) have added a dry mixing step before ball milling. Most of the equipment used is a V-type mixer or a double cone mixer for dry mixing. These devices achieve uniform mixing of powders through tumbling and gravity convection mixing. For raw materials with large density differences, the mixing efficiency is low. Therefore, the time for this process is usually between 1 hour and 2 hours, and the minimum is not less than 1 hour. It is time-consuming, and based on the differences in density, particle size or fluidity of raw materials such as iron oxide and manganese oxide, problems such as component segregation and agglomeration may occur during the mixing process, resulting in unsatisfactory uniformity of the final mixed powder. Summary of the invention

[0009] The purpose of the present invention is to provide a soft ferrite core powder mixing system with uniform mixing, which can effectively improve the uniform distribution of raw materials with large component differences on a microscopic scale, avoid segregation caused by differences in raw material density or particle size, overcome agglomeration problems, improve mixing efficiency, reduce the time consumption of ball milling process, and provide a prerequisite for improving sintering quality.

[0010] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0011] A uniformly mixed soft ferrite core powder mixing system, comprising:

[0012] A first-order unit, comprising a first-order tank, wherein the additive and part of ZnO are mixed based on the first-order tank, wherein the amount of ZnO added is 30%-60% of the total amount of the components, and the additive comprises at least SiO2, and SiO2 is added preferentially to obtain a ZnO premix;

[0013] A second-order unit includes a second-order tank, and the ZnO premix, the remaining ZnO, the remaining auxiliary materials and Fe2O3 are mixed based on the second-order tank to obtain a premix;

[0014] The first-stage tank and the second-stage tank both include a tank body, an upper turntable, a lower turntable, a chassis, and a feeding pipe; the upper turntable and the lower turntable are centrally arranged in the tank body from top to bottom and have a rotation speed of 50-300rpm, the chassis is arranged at the bottom of the tank body and has a rotation speed of 0.5-2rpm, a conical portion protruding upward is arranged in the center of the chassis, and the feeding pipe is a negative pressure power pipeline that returns the material at the bottom of the tank body to the upper turntable.

[0015] The first-stage tank is also provided with an additive pipe for feeding materials to the center of the second-layer turntable, and the second-stage tank is also provided with an auxiliary material pipe for feeding materials to the center of the second-layer turntable. The feeding pipe of the first-stage tank is connected to the material in the auxiliary material pipe through a connecting pipe with a valve.

[0016] The process of the first-order unit is completed in a first-order tank, and the steps include:

[0017] Feeding: feed ZnO to the upper turntable of the first-stage tank, the feeding amount of ZnO is 40%-55% of its components, feed the additive through the additive pipe to the center of the lower turntable, the feeding of ZnO and the feeding of additive are started synchronously, and the feeding of additive is first fed with SiO2;

[0018] Return material mixing: After the ZnO feeding is completed, keep the bottom plate rotating, and start the feeding pipe to return the material at the bottom of the first-stage tank to the upper turntable. The rotation mixing time is 3-12 minutes;

[0019] Discharging: The feeding pipe is connected to the connecting pipe to send the ZnO premix in the first-stage tank into the second-stage tank;

[0020] The process of the second-stage unit is completed in a second-stage tank, and the steps include:

[0021] Feeding: Fe2O3 is fed into the middle of the upper turntable through the feeding pipe; ZnO premix, remaining ZnO and other auxiliary materials are fed into the middle of the lower turntable in sequence through the auxiliary material pipe; the remaining auxiliary materials include MnO or NiO;

[0022] Return material mixing: After the Fe2O3 feeding is completed, keep the bottom plate rotating, and start the feeding pipe to return the material at the bottom of the second-stage tank to the upper turntable. The rotation mixing time is 5-20 minutes.

[0023] The diameter of the upper turntable of the first-stage tank is smaller than that of the lower turntable. A baffle is provided on the inner wall of the tank body of the first-stage tank corresponding to the height of the upper turntable. The baffles are multiple and are arranged equidistantly relative to the annular array of the first-stage tank. The circumferential range covered by all the baffles does not exceed 1 / 4 of a circle. The upper side of the baffle is inclined toward the center of the tank body.

[0024] and / or

[0025] The lower turntable and the upper turntable of the second-stage tank are of equal size, or the lower turntable of the second-stage tank is slightly larger than the upper turntable.

[0026] A central rotating shaft is provided through the bottom of the tank body and is rotatably connected to the tank body. The central rotating shaft is driven to rotate by a motor and is fixedly installed relative to the lower turntable and the upper turntable. A through hole is provided in the center of the top of the conical portion for the central rotating shaft to pass through. A lower gear is provided at the bottom of the central rotating shaft coaxially fixed thereto. A mounting cylinder coaxially fixed thereto is provided in the center below the conical portion. An inner gear ring is fixed on the inner wall of the bottom end of the mounting cylinder. A reduction gear set is provided between the lower gear and the inner gear ring to achieve reduction transmission between the two.

[0027] The top of the feeding pipe is provided with a drop-out port located above the upper turntable. For the first-stage tank, the bottom of the additive tube is centrally sleeved on the drop-out port, and after the bottom of the additive tube passes through the upper turntable of the first-stage tank, its tube mouth is located in the central position above the lower turntable. A conical guide fin is fixed on the side wall of the additive tube, and the guide fin is arranged above the upper turntable, with the tip of the guide fin on top and the top not higher than the drop-out port.

[0028] For the first-stage tank, the top end of the central rotating shaft is fixedly connected to the lower turntable, and 2-3 vertical poles are provided between the upper turntable and the lower turntable, and the vertical poles are arranged in a circumferential array relative to the upper turntable.

[0029] For the second-stage tank, the auxiliary material pipe passes through the side wall of the tank body and is provided with an inclined elbow at the inner end. The bottom end of the elbow is provided with a pipe opening corresponding to the central setting of the lower turntable. The central rotating shaft is coaxially fixed with the lower turntable and the upper turntable from bottom to top.

[0030] The feeding pipe includes a power section, a feeding section, and a return section which are connected in sequence from bottom to top. The power section is connected to the bottom end of the feeding section by a right-angle bend, and the end of the power section is connected to a wind source. The bottom end of the feeding section is provided with a suction pipe connected to the tank body, and the bottom side of the suction pipe is arranged close to the chassis. The top end of the return section is connected to the top of the feeding section, and the return section runs through the irrigation and has a drop port centered above the upper turntable at the bottom end.

[0031] The feeding pipe of the first-stage tank is connected to the ZnO conveying line and the connecting pipe through pipelines and valves, the material removal end of the connecting pipe is connected to the auxiliary material pipe through a valve, and the feeding pipe of the second-stage tank is also connected to the Fe2O3 conveying line through pipelines and valves;

[0032] The additive pipe of the first-stage tank is connected to an additive delivery line, and the additive delivery line includes a CuO delivery line, a CoO delivery line, and a SiO2 delivery line; the auxiliary material pipe of the second-stage tank is connected to an auxiliary material delivery line through a pipeline and a valve, and the auxiliary material delivery line includes a ZnO delivery line, a MnO delivery line and / or a NiO delivery line.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This system is used to produce soft ferrite products. After improvement, it can effectively improve the uniform distribution of Fe2O3 and other raw materials on a microscopic scale, avoid segregation caused by differences in raw material density or particle size, overcome agglomeration problems, and reduce local component deviations. Therefore, it can improve the quality of the sintering process, which is crucial for obtaining a high-density, low-porosity magnetic core structure, and can significantly improve the magnetic permeability of the magnetic core and reduce losses. At the same time, it can reduce ball milling time and improve ball milling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the system flow of the present invention.

[0036] Figure 2 It is a schematic diagram of the first-stage tank of the present invention.

[0037] Figure 3 It is a schematic diagram of the internal structure of the first-stage tank of the present invention.

[0038] Figure 4 It is a schematic diagram of the internal structure of the second-stage tank of the present invention.

[0039] Numbers shown in the accompanying drawings:

[0040] 1. First-stage tank; 2. Second-stage tank; 3. Feeding pipe; 4. Connecting pipe; 5. Additive pipe; 6. Auxiliary material pipe; 7. Tank cover; 8. Chassis; 9. Conical part; 10. Central rotating shaft; 11. Shaft seat; 12. Support seat; 13. Driven pulley; 14. Mounting cylinder; 15. Inner gear ring; 16. Lower gear; 17. Reduction gear set; 18. Upper turntable; 19. Lower turntable; 20. Vertical pole; 21. Guide fin; 22. Baffle; 23. Suction pipe; 24. Feeding section; 25. Return section; 26. Dropping port. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the application equally.

[0042] The instruments, reagents, materials, etc. involved in the following embodiments, unless otherwise specified, are all conventional instruments, reagents, materials, etc. in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following embodiments, unless otherwise specified, are all conventional experimental methods, detection methods, etc. in the prior art.

[0043] Example:

[0044] In the mixing process, even if the pre-mixing process is added, the mixing effect cannot be effectively solved, mainly because it is difficult to avoid the existence of poor mixing, segregation, agglomeration and other phenomena, which have a direct impact on the subsequent growth of the well body and the clarity of the grain boundary. Therefore, in essence, the key improvement point of the soft ferrite core lies in mixing and sintering.

[0045] The existing equipment and processes are to directly mix the powder raw materials without considering the characteristics of the raw materials. We have improved this link. The specific process is as follows:

[0046] SiO2 acts as a flux to promote grain growth during sintering. As a trace additive, it has an important influence on the performance of soft ferrites. However, silicon oxide has poor fluidity and a density (2.65 g / cm 3 ) is significantly lower than all other raw materials and additives, and is prone to stratification or segregation due to density differences during mixing. The particle size is extremely fine and easy to agglomerate, and the addition amount is extremely low (1%-2%). Poor dispersion has a direct impact on subsequent sintering and crystal formation.

[0047] 1 Premixing stage - SiO2 and other additives mixed with ZnO

[0048] 1.1 Key points of the process: SiO2 and other additives are mixed with part of the ZnO powder raw materials, and the mixing process is carried out in a first-stage tank.

[0049] Weighing: Weigh SiO2 and ZnO based on the process ratio (or use metering feeding);

[0050] Feeding: Feeding is done by pipeline pneumatic conveying;

[0051] Mixing time: 9min

[0052] 1.2 Process equipment: first stage tank

[0053] 1.2.1 Equipment structure: first-stage tank

[0054] Since this system and process are both innovative designs, the first-stage tank 1 is specifically introduced as follows:

[0055] The first-stage tank 1 comprises a tank body, the top of which is provided with a tank cover 7 which is sealed and closed with a flange, so that the tank body is a closed containing structure based on the tank cover 7.

[0056] An annular mounting step is provided on the inner wall of the tank body near the bottom, and an annular chassis 8 is provided above the mounting step and is rotatably connected thereto via a large bearing. The circumferential side of the chassis 8 is adapted to the inner wall of the tank body, and the chassis 8 is used to receive materials. An upwardly protruding conical portion 9 is provided on the inner ring of the chassis 8 for guiding the materials to the surroundings, so that the powder is piled on the chassis 8 in a ring shape. A through hole is provided in the center of the conical portion 9, and a central rotating shaft 10 passes through the through hole of the conical portion 9. The chassis 8 divides the internal space of the tank body so that the tank body space above the chassis 8 is used for mixing and distributing materials, and the space below the chassis 8 is used for installing transmission equipment to obtain an equipment warehouse.

[0057] The bottom of the tank body is centrally installed with an axle seat 11, the bottom of the central shaft 10 passes through the axle seat 11, the inside of the axle seat 11 is rotatably connected with the central shaft 10 through a bearing, and the axle seat 11 is used to obtain a stable installation of the central shaft 10 when it rotates at high speed. The bottom end of the central shaft 10 is provided with a driven pulley 13 that is coaxial with it and circumferentially fixed. The driven pulley 13 is located below the tank body, and the bottom of the tank body is fixed on a support seat 12. A motor is installed on one side of the support seat 12. A driving pulley is provided on the output shaft of the motor. The driving pulley and the driven pulley 13 are connected through a belt drive to drive the central shaft 10. This design realizes closed protection of the rotating components, and facilitates installation and maintenance of the motor and belt drive structure.

[0058] Not limited to this example, the motor can also be directly installed in the equipment compartment, and the output shaft of the motor can be directly connected to the central shaft 10 through a reduction gearbox to drive the central shaft 10. More concise.

[0059] A mounting cylinder 14 coaxially fixed thereto is provided at the center below the conical portion 9. The mounting cylinder 14 is a pillar-type cylindrical structure. An inner gear ring 15 is fixed to the inner wall of the bottom end of the mounting cylinder 14. A lower gear 16 located above the shaft seat 11 is fixed to the bottom of the central rotating shaft 10. A reduction gear set 17 is provided between the lower gear 16 and the inner gear ring 15 to realize transmission between the two. The reduction gear set 17 is a gear reducer structure. The reduction gear set 17 includes a gear box, which is fixed to the tank body by a support (such as a long bolt). The bottom of the gear box is provided with an output shaft on the upper part, and an output gear is installed on the output shaft. The bottom of the gear box is provided with an input shaft, and an input gear is installed on the input shaft. A plurality of transmission gears are installed in the gear box, and the plurality of transmission gears are meshed in sequence from the input shaft to the output shaft to realize the reduction transmission of the input shaft to the output shaft. The input gear is meshed with the lower gear 16 of the central rotating shaft 10, and the output gear is meshed with the inner gear ring 15 at the bottom end of the mounting cylinder 14, so that when the central rotating shaft 10 rotates at a high speed, the chassis 8 rotates at a low speed.

[0060] The rotation speed of the central rotating shaft 10 is 50-300 rpm, and the rotation speed of the chassis 8 is reduced to 0.5-2 rpm by deceleration. The optimal rotation speed of the chassis 8 is controlled to 0.8-1 rpm.

[0061] An upper turntable 18 and a lower turntable 19 located in the tank body are provided above the turntable and the conical portion 9, and 2-3 vertical poles 20 are provided between the upper turntable 18 and the lower turntable 19. The top ends of the vertical poles 20 are fixed to the upper turntable 18, and the bottom ends of the vertical poles 20 are fixed to the lower turntable 19. The vertical poles 20 are arranged in a circumferential array relative to the upper turntable 18, and the top end of the central rotating shaft 10 is fixedly mounted on the bottom surface of the lower turntable 19 to realize the rotational drive of the upper turntable 18 and the lower turntable 19.

[0062] The tank body is also provided with a feeding pipe 3, an additive pipe 5,

[0063] The feeding pipe 3 includes a power section, a feeding section 24, and a return section 25 which are connected in sequence from bottom to top. The power section is connected to the bottom end of the feeding section 24 by a right-angle bend, and the bend is located below the chassis 8 and is arranged close to the chassis 8. The end of the power section is connected to a wind source for supplying air inward to obtain feeding power. The bottom end of the feeding section 24 is provided with a suction pipe 23 connected to the tank body, and the bottom side of the suction pipe 23 is arranged close to the chassis 8 to suck out and return the material falling on the chassis 8. The top end of the return section 25 is connected to the top of the feeding section 24, and the return section 25 runs through the irrigation and has a drop port 26 centered above the upper turntable 18 at the bottom.

[0064] The feeding pipe 3 is connected with a zinc oxide ZnO conveying line and a connecting pipe 4 through pipelines and valves. The connecting pipe 4 is used to deliver the mixed powder to the next process link.

[0065] Based on the above structure, the material on the turntable is transported to the middle of the loading tray through the loading pipe 3.

[0066] The additive pipe 5 is centrally arranged in the material return section 25, and the additive pipe 5 is sealed and connected to the through position of the material return section 25, so as not to affect the material transportation. The outer end of the additive pipe 5 is connected to the additive delivery line, including the CuO delivery line, the CoO delivery line, and the SiO2 delivery line. The feed pipe of the additive delivery line is connected to the additive pipe 5 through a valve, so that when a certain additive reaches the addition amount, the other additives can be switched one by one.

[0067] A circular hole for the lower part of the additive tube 5 to pass through is provided in the center of the upper turntable 18, and the bottom end of the additive tube 5 is provided at the central position between the lower turntable 19 and the upper turntable 18. A conical guide fin 21 is fixed on the side wall of the additive tube 5, and the guide fin 21 is provided above the upper turntable 18. The tip of the guide fin 21 is at the top and the top end is located at the drop opening 26 at the bottom end of the return section 25, which will not cause the size of the tube cavity of the return section 25 to change, and will not block and squeeze the material. The falling powder is initially guided outward by the guide fin 21 to fall into the peripheral area of ​​the circular hole.

[0068] Through the above structure, the additive tube 5 can penetrate the return section 25 of the feeding tube 3, so that a small amount of additive can be sent to the central position of the lower turntable 19 by using a thinner additive tube 5. When the amount of additive is very small, it is ensured that a small amount of powder can be dispersed in the center and the centrifugal dispersion is uniform. It is particularly suitable for the rapid and uniform dispersion of a very small amount of material.

[0069] An inclined baffle 22 is fixed on the inner wall of the tank body, and the top side of the baffle 22 is inclined toward the center of the tank body. The baffle 22 is arranged on the outer side of the Shangcen turntable, and the bottom side of the baffle 22 is fixedly welded or bolted to the inner wall of the tank body. The baffle 22 is multi-piece and evenly distributed relative to the circumference of the tank body. The circumferential range covered by all baffles 22 does not exceed 1 / 4, and can rebound about 20% of the powder falling from the upper turntable 18 to the middle position of the lower turntable 19, thereby mixing with the additives that are being emitted outward from the lower turntable 19, and then falling onto the bottom plate 8 together with the remaining powder from the upper turntable 18.

[0070] In the first-stage tank 1, the upper turntable 18 is smaller than the lower turntable 19. On the one hand, it is conducive to adapting to the low density of silica. On the other hand, combined with the effect of the baffle 22, the small amount of powder on the upper turntable 18 can be more easily collided to the inner position of the lower turntable 19, thereby promoting preliminary mixing.

[0071] 1.2.2 Parameter settings

[0072] Tank inner diameter: 1.5m,

[0073] Diameter of upper turntable: 0.3m,

[0074] The diameter of the lower turntable: 0.4m,

[0075] Central shaft speed: 150rpm;

[0076] Chassis speed: 0.8rpm;

[0077] 1.3 Process steps (the following processes are all based on the first-stage tank)

[0078] 1.3.1 Feeding: Start the rotation of the central shaft and the chassis, and feed ZnO, CuO, CoO, and SiO2 quantitatively based on the process ratio.

[0079] Feeding method: The feeding amount of ZnO is 50% of its components, and is directly fed into the middle of the upper rotating disk through the feeding pipe; the additives are directly fed into the center of the lower rotating disk through the additive pipe;

[0080] Feeding time: ZnO feeding and additive feeding start and stop synchronously;

[0081] Feeding order: SiO2 is added to the additive pipeline first, and the other additives (CuO, CoO) are added later.

[0082] Feeding time: 2 min for SiO2; 1.5 min for CuO and CoO respectively; 5 min for ZnO;

[0083] 1.3.2 Return material mixing: After the feeding of ZnO and additives is completed, the passage from the feeding section to the return material section of the first-stage tank feeding pipe is started to return the material on the turntable to the upper turntable. The mixing is achieved by repeated throwing of the upper turntable. The rotation speed of the chassis is 0.8rpm and the rotation mixing time is 4min.

[0084] 1.3.3 Discharging: The materials on the turntable are sent into the connecting pipe through the bottom of the feeding pipe and enter the second-stage tank for second-stage premixing.

[0085] 1.4 Principle Explanation

[0086] (1) Solving the agglomeration and segregation of silicon oxide has a great improvement effect on the crystal production in the sintering process.

[0087] When ZnO is directly fed into the middle of the upper turntable through the feeding pipe, it is thrown out of the upper turntable due to centrifugal force due to the high-speed rotation of the upper turntable. Combined with the small size of the upper turntable and the inclined baffles arranged at equal intervals around it, about 20% of the ZnO powder is collided into the middle area of ​​the lower turntable.

[0088] At the same time, additives are added through the additive tube at the center of the lower turntable. Silicon dioxide is added first. Since silicon dioxide has fine particles and poor fluidity, it is easy to agglomerate during friction. Therefore, zinc oxide with good fluidity is used. When silicon dioxide falls on the second turntable, it immediately participates in the mixing of silicon dioxide. The design of the annular array of baffles and collision drop materials allows the ZnO powder to scatter evenly on the second turntable in the circumferential direction, and quickly come into full contact with the silicon dioxide particles that have just started the throwing stroke, thereby promoting convection mixing of materials in the turntable, reducing the surface energy of silicon oxide particles, and significantly reducing electrostatic adsorption and agglomeration.

[0089] (2) For the initial mixing of multiple components with large differences in component proportions, the time is short and the premixing effect is good.

[0090] This process uses the centrifugal force generated by high-speed rotation to throw particles outward, forming an annular dispersion of upper and lower double layers of materials. The centrifugal process is very helpful in breaking up agglomerations, and through centrifugation and throwing, the particles are fully dispersed, falling during the dispersion (the falling areas overlap), achieving full and efficient mixing of the double layers of materials.

[0091] (3) Based on the centrifugal force, the particles collide with the inner wall of the container, and then rebound and fall onto the conical part and the bottom plate. The centrifugal bulk material is combined with the irregular and complex impact path to avoid the segregation defect of the centrifugal bulk material, so that the powder falling on the bottom plate is mixed evenly. The fallen powder is pushed to the periphery of the bottom plate through the conical part, and finally falls on the bottom plate to form a ring-shaped material. As the bottom plate rotates, it is cyclically sucked to the top of the tank and thrown again on the upper turntable. This mixing method realizes repeated mixing of the powder in multiple dimensions, and the particles are evenly dispersed.

[0092] (4) The structure is simple, without complicated stirring elements, and compared with three-dimensional mixing equipment (V-type, double cone, etc.) in which the entire tank is flipped, it is more energy-efficient, reduces component wear, and has lower operating costs.

[0093] 2Premix two-stage

[0094] 2.1 Key points of the process: The first-stage discharge is mixed with other raw materials, and the mixing process is completed in the second-stage tank.

[0095] Mixing time: 23min

[0096] 1.2 Process equipment: Second stage tank

[0097] The overall structure of the second-stage tank 2 is roughly the same as that of the first-stage tank 1, but the differences are as follows:

[0098] The upper turntable 18 and the lower turntable 19 are of equal size;

[0099] No baffle 22 is provided in the tank body;

[0100] There are differences in the pipeline settings: the "additive pipe 5" is removed and an auxiliary material pipe 6 is added, the auxiliary material pipe 6 passes through the side wall of the tank body and is provided with an inclined elbow at the inner end, and a discharge pipe opening is provided at the bottom end of the elbow, and the pipe opening of the elbow corresponds to the central setting of the lower turntable 19, which is used to guide the material to this position.

[0101] The outer end of the auxiliary material pipe 6 of the second-stage tank 2 is connected to the connecting pipe 4 and the auxiliary material conveying line material through a valve respectively. Since the upstream of the connecting pipe 4 is connected to the feeding pipe 3 of the first-stage tank 1, the material in the first-stage tank 1 can be fed from the auxiliary material pipe 6 onto the lower turntable 19, completing the material connection between the two stages.

[0102] The auxiliary material conveying line includes a ZnO conveying line, a MnO conveying line and / or a NiO conveying line;

[0103] The feeding pipe 3 of the second-stage tank 2 is also connected to the Fe2O3 conveying line through pipelines and valves for feeding the main material.

[0104] Since the auxiliary material tube 6 does not occupy the central space, the upper turntable 18 and the lower turntable 19 are directly fixed to the central rotating shaft 10. The top of the central rotating shaft 10 passes through and coaxially fixes the upper turntable 18 and the lower turntable 19 in sequence to realize the rotation drive of the upper turntable 18 and the lower turntable 19.

[0105] The upper surfaces of the upper rotating disk 18 and the lower rotating disk 19 are provided with convex ribs for retaining a small amount of material to prevent the powder from directly impacting the rotating disk surface.

[0106] In addition to the above differences, the transmission structure of the tank body, tank cover 7 and bottom of the second-stage tank 2 to the central rotating shaft 10 and the chassis 8 is consistent with that of the first-stage tank 1.

[0107] 2.2.2 Parameter settings

[0108] Tank inner diameter: 3.0m,

[0109] Diameter of upper turntable: 1.5m,

[0110] Diameter of lower turntable: 1.5m,

[0111] Central shaft speed: 80rpm;

[0112] Chassis speed: 1.0rpm;

[0113] 2.3 Process steps (the following processes are all based on the second-stage tank)

[0114] 2.3.1 Feeding: Start the rotation of the central shaft and the chassis, put the powder in the first-stage tank into the second-stage tank, and feed the main material and auxiliary material based on the process ratio.

[0115] Feeding method: the powder in the first-stage tank is connected to the auxiliary material pipe through the feeding pipe of the first-stage tank; the material is directly fed into the middle of the upper turntable; the remaining 50% of ZnO and other auxiliary materials are fed through the auxiliary material pipe and fed into the middle of the lower turntable on one side.

[0116] Feeding start: The feeding of powder and Fe2O3 in the first-stage tank is started synchronously;

[0117] Feeding order:

[0118] During the feeding stage, the feeding pipe of the second-stage tank always keeps feeding Fe2O3;

[0119] The materials in the first-stage tank are fed to the lower turntable in the second-stage tank through the auxiliary material pipe. After all the premixed materials in the first stage are transferred to the second-stage tank, the ZnO conveying line is connected to feed the remaining 50% of ZnO; finally, the remaining auxiliary materials (MnO or NiO) are fed;

[0120] Feeding time: 5 minutes for material transfer in the first-stage tank, 5 minutes for the remaining 50% ZnO, and 5 minutes for MnO or NiO; Fe2O3 is fed according to the dosage, and the feeding time is not less than 15 minutes;

[0121] 2.3.2 Return material mixing: After the Fe2O3 feeding is completed, the feeding pipe of the second-stage tank is started from the feeding section to the return material section, and the material on the turntable is returned to the upper turntable. The mixing is achieved by repeated throwing of the upper turntable. The rotation speed of the chassis is 1.0rpm, and the rotation mixing time is 8min.

[0122] 2.4 Principle Explanation

[0123] (1) The material (ZnO with additives) in the first-stage tank is transferred to the lower turntable of the second-stage tank through the auxiliary material pipe, and the Fe2O3 on the upper turntable is started to be quickly dispersed and mixed, taking advantage of the good dispersibility of ZnO to promote the dispersion of the additive and the powder raw material as a whole.

[0124] (2) Through two-stage premixing, the huge gap between the content of the main material, auxiliary material and additive of Fe2O3 is balanced, and staged premixing is achieved to optimize the mixing order. The characteristics of the raw materials are utilized and coordinated with each other to effectively solve the problems of large component differences, difficulty in mixing small-proportion components, and obvious segregation.

[0125] (3) Based on centrifugal force, the particles hit the inner wall of the container, and then rebound and fall onto the conical part and the bottom plate, obtaining a complex impact rebound path to avoid segregation caused by differences in raw material density or particle size. The falling powder is guided by the conical part and falls on the bottom plate to form a ring-shaped pile, and is cyclically sucked to the top of the tank as the bottom plate rotates, and is thrown again on the upper turntable. This mixing method achieves repeated mixing of the powder in multiple dimensions, and the particles are evenly dispersed.

[0126] (4) The structure is simple, without complicated stirring elements, and compared with three-dimensional mixing equipment (V-type, double cone, etc.) in which the entire tank is flipped, it is more energy-efficient, reduces component wear, and has lower operating costs.

[0127] Summary: In summary, after the process is improved, it can effectively improve the uniform distribution of Fe2O3 and other raw materials on a microscopic scale, avoid segregation caused by differences in raw material density or particle size, and overcome the agglomeration problem. This uniformity is crucial for the subsequent ball milling and sintering process, reducing local composition deviations. This is crucial for obtaining a high-density, low-porosity magnetic core structure, which can significantly improve the magnetic permeability of the magnetic core and reduce losses. At the same time, the ball milling time can be reduced and the ball milling efficiency can be improved. If the raw materials have been preliminarily mixed before ball milling, the ball mill only needs to focus on refining the particles and further homogenizing them without having to undertake the task of initial mixing. This not only saves energy, but also reduces impurities introduced during the ball milling process.

[0128] In addition, the dispersion effect of the additive SiO2 is greatly improved. Reasonable use of the characteristics between the raw materials and reasonable optimization of the mixing order. Usually, most types of soft ferrite cores require zinc oxide as an auxiliary material, so ZnO is generally indispensable. In this stage, zinc oxide is used to premix with additives with very little content, and the auxiliary material ZnO is only half of its total amount. On the one hand, the gap with the additive component is reduced, the dispersion efficiency is improved, the particles can be mixed quickly, and the time consumption of the first stage is reduced. On the other hand, as the auxiliary material with the best fluidity, it plays a role of supporting, connecting and combining. In the dispersion of additives, the problem of silicon oxide agglomeration is alleviated. At the same time, in the preliminary mixing stage with Fe2O3 in the second-stage tank, the dispersion effect of additives in particles is promoted. Through the mixing of two stages, the common problems of uneven dispersion, agglomeration and segregation of small-proportion raw materials of SiO2 are solved, ensuring that silicon oxide is evenly dispersed in the soft ferrite raw materials, providing a high-quality raw material basis for subsequent processes.

[0129] This equipment takes less time in the premixing stage, which can be completed in about half an hour, and can reduce the ball milling time by about 20%-35%, greatly shortening the process time and improving efficiency.

[0130] Moreover, the system is based on pneumatic conveying, circulating centrifugal bulk material and mixing, with a simple structure, easy maintenance, low operating energy consumption, and economical and practical.

Claims

1. A uniformly mixed soft ferrite core powder mixing system, characterized in that: include: A first-order unit, comprising a first-order tank, wherein the additive and part of ZnO are mixed based on the first-order tank, wherein the amount of ZnO added is 30%-60% of the total amount of the components, and the additive comprises at least SiO2, and SiO2 is added preferentially to obtain a ZnO premix; A second-order unit includes a second-order tank, and the ZnO premix, the remaining ZnO, the remaining auxiliary materials and Fe2O3 are mixed based on the second-order tank to obtain a premix; The first-stage tank and the second-stage tank both include a tank body, an upper turntable, a lower turntable, a chassis, and a feeding pipe; the upper turntable and the lower turntable are centrally arranged in the tank body from top to bottom and have a rotation speed of 50-300rpm, the chassis is arranged at the bottom of the tank body and has a rotation speed of 0.5-2rpm, and an upwardly protruding conical portion is provided in the center of the chassis, the feeding pipe is a negative pressure power pipeline for returning the material at the bottom of the tank body to the upper turntable, the first-stage tank is also provided with an additive pipe for feeding material to the center of the second-stage turntable, and the second-stage tank is also provided with an auxiliary material pipe for feeding material to the center of the second-stage turntable, and the feeding pipe of the first-stage tank is connected to the auxiliary material pipe material through a connecting pipe with a valve.

2. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: The process of the first-order unit is completed in a first-order tank, and the steps include: Feeding: feed ZnO to the upper turntable of the first-stage tank, the feeding amount of ZnO is 40%-55% of its components, feed the additive through the additive pipe to the center of the lower turntable, the feeding of ZnO and the feeding of additive are started synchronously, and the feeding of additive is first fed with SiO2; Return material mixing: After the ZnO feeding is completed, keep the bottom plate rotating, and start the feeding pipe to return the material at the bottom of the first-stage tank to the upper turntable. The rotation mixing time is 3-12 minutes; Discharging: The feeding pipe is connected to the connecting pipe to send the ZnO premix in the first-stage tank into the second-stage tank; The process of the second-stage unit is completed in a second-stage tank, and the steps include: Feeding: Fe2O3 is fed into the middle of the upper turntable through the feeding pipe; ZnO premix, remaining ZnO and other auxiliary materials are fed into the middle of the lower turntable in sequence through the auxiliary material pipe; the remaining auxiliary materials include MnO or NiO; Return material mixing: After the Fe2O3 feeding is completed, keep the bottom plate rotating, and start the feeding pipe to return the material at the bottom of the second-stage tank to the upper turntable. The rotation mixing time is 5-20 minutes.

3. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: The diameter of the upper turntable of the first-stage tank is smaller than that of the lower turntable. A baffle is provided on the inner wall of the tank body of the first-stage tank corresponding to the height of the upper turntable. The baffles are multiple and are arranged equidistantly relative to the annular array of the first-stage tank. The circumferential range covered by all the baffles does not exceed 1 / 4 of a circle. The upper side of the baffle is inclined toward the center of the tank body. and / or The lower turntable and the upper turntable of the second-stage tank are of equal size, or the lower turntable of the second-stage tank is slightly larger than the upper turntable.

4. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: A central rotating shaft is provided through the bottom of the tank body and is rotatably connected to the tank body. The central rotating shaft is driven to rotate by a motor and is fixedly installed relative to the lower turntable and the upper turntable. A through hole is provided in the center of the top of the conical portion for the central rotating shaft to pass through. A lower gear is provided at the bottom of the central rotating shaft coaxially fixed thereto. A mounting cylinder coaxially fixed thereto is provided in the center below the conical portion. An inner gear ring is fixed on the inner wall of the bottom end of the mounting cylinder. A reduction gear set is provided between the lower gear and the inner gear ring to achieve reduction transmission between the two.

5. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: The top of the feeding pipe is provided with a drop-out port located above the upper turntable. For the first-stage tank, the bottom of the additive tube is centrally sleeved on the drop-out port, and after the bottom of the additive tube passes through the upper turntable of the first-stage tank, its tube mouth is located in the central position above the lower turntable. A conical guide fin is fixed on the side wall of the additive tube, and the guide fin is arranged above the upper turntable, with the tip of the guide fin on top and the top not higher than the drop-out port.

6. The uniformly mixed soft ferrite core powder mixing system according to claim 5, characterized in that: For the first-stage tank, the top end of the central rotating shaft is fixedly connected to the lower turntable, and 2-3 vertical poles are provided between the upper turntable and the lower turntable, and the vertical poles are arranged in a circumferential array relative to the upper turntable.

7. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: For the second-stage tank, the auxiliary material pipe passes through the side wall of the tank body and is provided with an inclined elbow at the inner end. The bottom end of the elbow is provided with a pipe opening corresponding to the central setting of the lower turntable. The central rotating shaft is coaxially fixed with the lower turntable and the upper turntable from bottom to top.

8. The uniformly mixed soft ferrite core powder mixing system according to claim 1, characterized in that: The feeding pipe includes a power section, a feeding section, and a return section which are connected in sequence from bottom to top. The power section is connected to the bottom end of the feeding section by a right-angle bend, and the end of the power section is connected to a wind source. The bottom end of the feeding section is provided with a suction pipe connected to the tank body, and the bottom side of the suction pipe is arranged close to the chassis. The top end of the return section is connected to the top of the feeding section, and the return section runs through the irrigation and has a drop port centered above the upper turntable at the bottom end.

9. The uniformly mixed soft ferrite core powder mixing system according to claim 2, characterized in that: The feeding pipe of the first-stage tank is connected to the ZnO conveying line and the connecting pipe through pipelines and valves, the material removal end of the connecting pipe is connected to the auxiliary material pipe through a valve, and the feeding pipe of the second-stage tank is also connected to the Fe2O3 conveying line through pipelines and valves; The additive pipe of the first-stage tank is connected to an additive delivery line, and the additive delivery line includes a CuO delivery line, a CoO delivery line, and a SiO2 delivery line; the auxiliary material pipe of the second-stage tank is connected to an auxiliary material delivery line through a pipeline and a valve, and the auxiliary material delivery line includes a ZnO delivery line, a MnO delivery line and / or a NiO delivery line.

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