A method for producing a permanent magnet ferrite

Abstract

The application discloses a preparation method of permanent magnet ferrite, and belongs to the technical field of magnetic materials. High-chlorine iron red is mixed with solvent water in proportion to obtain a slurry, a pH value regulator is added under stirring to perform polycondensation reaction, and the slurry is obtained through maturation polymerization; an alkaline solvent is added under stirring, and then precipitation and drainage are performed to obtain the slurry; raw materials are proportioned according to a molecular formula, the actual required weight of the iron red slurry is calculated, the required weight of the slurry is weighed by a weighing tank, mixed with other materials, and a dispersing agent is added; the obtained slurry is crushed by a crushing device, and then concentrated; the concentrated slurry is pre-burned by a rotary kiln to obtain ferrite pre-burning granular materials; the obtained pre-burning granular materials are crushed by dry ball milling, water and an additive are added for secondary ball milling, and the slurry with a granularity of 250 meshes is obtained through continuous ball milling; the obtained slurry is concentrated and then formed by pressing under a magnetic field; the formed body is sintered in air after dehydration and glue removal at 350 DEG C for 3-4 hours, and the permanent magnet ferrite is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and particularly relates to a preparation method of permanent ferrite. BACKGROUND

[0002] As a raw material used by most permanent ferrite manufacturers at present, red iron oxide is mostly produced by steel mills using acid regeneration process. The acid regeneration process mainly includes hydrochloric acid regeneration, sulfuric acid regeneration and mixed acid regeneration process. Sulfuric acid regeneration is basically eliminated due to low efficiency, and mixed acid is mainly used for stainless steel pickling. The red iron oxide containing high chromium produced in the regeneration process is not suitable for the production of magnetic materials. Therefore, the raw material red iron oxide of ferrite is mainly produced by hydrochloric acid regeneration process.

[0003] The quality of red iron oxide prepared by hydrochloric acid regeneration process is limited by the process advancement and quality control ability of the acid regeneration line, resulting in uneven quality of red iron oxide. High-chlorine red iron oxide is difficult to be used as a raw material for producing high-end ferrite in the prior art due to the presence of excessive Cl ions. However, the market stock of high-chlorine red iron oxide is large and the price is low. If it can be applied to the production of medium and high performance ferrite, it can generate greater economic benefits.

[0004] For example, the publication number CN113943152A discloses a method for preparing permanent ferrite from high-chlorine red iron oxide and a permanent ferrite process. The method uses a spray drying method to process high-chlorine red iron oxide. Although the method involves Cl elements, it can only process red iron oxide containing less than 0.3% of chlorine. The performance of the prepared ferrite fluctuates greatly and cannot achieve the performance of 9 series with residual magnetism≧4250Gs and intrinsic coercive force≧4400Oe.

[0005] For example, the publication number CN201210074240.7 discloses a new method for removing chlorine from pickled red iron. The method uses a multi-stage drying kiln at about 400-500℃ to make the chlorides in the pickled red iron react with water vapor to generate hydrogen chloride for separation. Although this scheme can reduce the chlorine content to some extent, it has high technical difficulty and high cost. SUMMARY

[0006] The application aims to solve the problem that high-chlorine red iron oxide is difficult to be used as a raw material for producing medium and high performance ferrite in the prior art. A method for preparing permanent ferrite is proposed, which uses high-chlorine red iron oxide as a raw material to achieve the performance of permanent ferrite with residual magnetism≧4250Gs and intrinsic coercive force≧4400Oe. This method widens the selection range of raw materials for permanent ferrite, reduces the cost of raw materials, and can generate greater economic benefits.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0008] A method for preparing a permanent magnet ferrite, comprising the following steps:

[0009] 1) Iron red polycondensation reaction: high-chlorine iron red and solvent are mixed in a 1:1-3 ratio by mass in a 1# stirring container to obtain a slurry with a pH value less than 2, a pH value regulator is added under stirring for polycondensation reaction, and a slurry with a solution pH value of 4.0-4.5 is obtained after polymerization and aging;

[0010] 2) Neutralization: a portion of the slurry obtained in step 1) is injected into a 2# stirring container, the injection amount being less than 1 / 4 of the volume of the 2# stirring container, an alkaline solvent is added under stirring to make the solution pH value reach 6-7, and then precipitation and drainage are performed to obtain a slurry with a final pH value of 6-7 and a concentration of 40%-50%;

[0011] 3) Storage: the slurry obtained in step 2) is completely injected into a 3# stirring container for standby, and the neutralization and concentration according to step 2) are repeatedly performed and then injected into the 3# stirring container until the slurry in the 1# stirring container is completely processed;

[0012] 4) Weighing and proportioning: the raw materials are proportioned according to the formula Ca (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 , wherein the iron red is the slurry obtained in step 3), the actual required weight of the iron red slurry is calculated according to the concentration of the slurry in the 3# stirring container and the proportioning amount of the iron red material, the required weight of the slurry is weighed by a weighing tank, and then mixed with other materials and a dispersing agent, wherein A is one or more of elements Ba, La and Bi;

[0013] 5) Crushing: the slurry obtained in step 4) is crushed by a crushing device to obtain a slurry with 1.5% or less of 250 mesh standard sieve oversize;

[0014] 6) Concentration: the slurry in step 5) is concentrated into a thick slurry with a concentration of 65-70%;

[0015] 7) Pre-burning: the thick slurry in step 6) is pre-burned by a rotary kiln, the material stays at a temperature of 200-600℃ for 4-5 hours, the pre-burning temperature is 1150-1300℃, and the material is kept for 1-3 hours to obtain ferrite pre-burning granular material;

[0016] SrCO3(high temperature) = SrO + CO2↑

[0017] SrO + Fe2O3 = SrO(Fe2O3)6

[0018] 8) Pulverization ball mill: the granular material obtained in step 7) is pulverized into 2-3um powder by dry ball mill, then mixed with water in proportion of 1:2.5-4, and added with additives for secondary ball mill, and continuously ball milled to obtain a slurry completely passing through 250 mesh standard sieve;

[0019] The additives play a role of controlling grain growth, ion substitution, replacing strontium and iron respectively by calcium and cobalt, and improving the performance of permanent magnet ferrite.

[0020] 9) Molding: the slurry obtained in step 8) is concentrated to 70% concentration, and then molded by pressing under a magnetic field of 8000-8800 Oe;

[0021] 10) Sintering: the molded body of step 9) is sintered in air after dehydration and glue removal at 300-400℃ for 3-4 hours, and the sintering temperature is 1160-1230℃, and the holding time is 1-3 hours, to obtain a permanent magnet ferrite.

[0022] The high-chlorine iron red in step 1) refers to iron red with chlorine content of 0.5-5%, the solvent is water, and the pH value regulator is calcium aluminate (3CaO·Al2O3) powder;

[0023] The alkaline solvent in step 2) is dilute ammonia water solution with pH value of 8-9;

[0024] The 1, 2, and 3# stirring containers are containers with epoxy resin anticorrosion on the inner wall, and the stirring shafts are made of stainless steel anticorrosion material, wherein 1 and 3# have the same volume of 30-50m 3 , and 2# has a volume of 10-20m 3 ;

[0025] The dispersing agent in step 4) is oleic acid;

[0026] The phase molecular formula is Ca (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 , wherein x is 0.2-0.4, y is 0.4-0.5, z is 0.01-0.04, and 2n-z is 11-12, and 1-x-y≥0.2;

[0027] The additives in step 8) are calcium silicate, white carbon black, cobalt oxide, and sorbitol, and the total amount of the pre-sintered material is 0.4-0.7%, 0.1-0.3%, 1.0-1.6%, and 0.1-0.3%, respectively;

[0028] The glue removal of the molded body at 350℃ in step 10) refers to the decomposition and removal of sorbitol at this temperature, to avoid the generation of surface cracks of the molded body.

[0029] The beneficial effects of the present application are:

[0030] 1. The ferrite manufacturing method uses iron red raw materials containing 0.5-5% chlorine, which widens the selection range of permanent magnet ferrite raw materials, reduces the cost of raw materials, and can produce greater economic benefits.

[0031] 2. The ferrite manufacturing method first uses calcium aluminate to carry out polycondensation reaction with the free acid of high-chlorine iron red slurry to generate polyaluminum chloride, thereby increasing the pH value, improving the phenomenon that the slurry is difficult to separate and turbid when the pH value of the high-chlorine iron red slurry is low, and avoiding the saturation phenomenon of the generated ammonium chloride solution caused by directly adding dilute ammonia solution for neutralization reaction when the pH value is low.

[0032] The reaction of adding pH value regulator calcium aluminate (3CaO·Al2O3) powder:

[0033] Al2O3+6HCl=2AlCl3+3H2O

[0034] CaO+2HCl=CaCl2+H2O

[0035] 3. The polyaluminum chloride generated in the ferrite manufacturing method is pre-fired in a rotary kiln to generate alumina (reaction equation 2AlCl3+3H2O=Al2O3+6HCl), which promotes the generation of ferrite pre-fired body and controls the size of the pre-fired body, which is beneficial to the solid phase reaction of the material and improves the magnetic performance.

[0036] 4. In the ferrite manufacturing method, dilute ammonia solution is added to neutralize chlorine (Cl - +NH 4+ =NH4Cl), which takes advantage of the characteristics that ammonium chloride starts to decompose at 100°C and then re-forms ammonium chloride fine particles after cooling, which is insoluble in water, so that the generated ammonium chloride is decomposed at the low temperature section of the rotary kiln, and then synthesized after being cooled by the exhaust fan and treated by bag dust collection, effectively solving the environmental protection treatment of chlorine in the application process of high-chlorine iron red.

[0037] 5. The ferrite manufacturing method uses wet batching according to the weight of the slurry concentration, which is different from the dry batching commonly used in the magnetic industry, and does not need to dry the slurry before batching, thereby simplifying the manufacturing process and saving energy.

[0038] 6. The ferrite manufacturing method adds lanthanum and zinc elements to the pre-fired material first, and then adds cobalt element during secondary grinding. The addition of these elements serves the purpose of ion substitution, which improves the performance of permanent magnet ferrite. Since cobalt is of high value, the risk of production and manufacturing can be greatly avoided.

[0039] 7. The ferrite manufacturing method adds dispersant oleic acid when preparing the pre-fired material, which emulsifies the slurry, reduces the intermolecular friction, and improves the degree of fragmentation of the slurry.

[0040] 8、The iron oxide preparation method controls the passing rate of 250 mesh standard sieve, increases the specific surface area of particles, enhances the activity, improves the particle freedom degree, and is beneficial to the performance improvement.

[0041] 9、The iron oxide preparation method uses high-chlorine iron red as raw material to prepare the phase Ca (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 The pre-sintering material realizes the performance of permanent magnet ferrite residual magnetism >=4250Gs and intrinsic coercive force >=4400Oe. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0043] EMBODIMENT

[0044] The embodiment provides a preparation method of permanent magnet ferrite, and specifically includes the following steps:

[0045] 1) Iron red polycondensation reaction:

[0046] High-chlorine iron red and water are mixed in a 1# stirring container in a proportion of 1:2 by mass, to obtain a slurry with a pH value less than 2, and then calcium aluminate is added for polycondensation reaction under stirring, to obtain a slurry with a solution pH value of 4.3 after maturation and polymerization;

[0047] 2) Neutralization:

[0048] A part of the slurry obtained in step 1) is injected into a 2# stirring container, and the injection amount is 1 / 5 of the volume of the 2# stirring container. After the pH value reaches 6 by adding a dilute ammonia solution with a pH value of 9 under stirring, precipitation and drainage are performed, to obtain a slurry with a final pH value of 6 and a concentration of 45%;

[0049] 3) Storage:

[0050] The slurry obtained in step 2) is completely injected into a 3# stirring container for standby, and the neutralization and concentration according to step 2) are repeatedly performed and then injected into the 3# stirring container until the slurry in the 1# stirring container is completely processed;

[0051] 4) Weighing and proportioning:

[0052] The raw materials are weighed and proportioned according to the molecular formula Ca (1-x-y) Srx A y Fe (2n-z) Zn z O 19 The proportions are made, wherein the iron red is the slurry obtained in step 3). Based on the slurry concentration in mixing container #3 and the proportion of iron red material, the actual weight of iron red slurry required is calculated. The required weight of slurry is weighed in a weighing tank and then mixed with other materials, and a dispersant is added, wherein A is element La.

[0053] 5) Disintegrate:

[0054] The slurry obtained in step 4) is crushed by ball mill to obtain a slurry with 1.5% of the material passing through a 250-mesh standard sieve;

[0055] 6) Concentration:

[0056] The slurry from step 5) was concentrated to 70% using a centrifugal dewatering machine;

[0057] 7) Preheating:

[0058] The slurry from step 6) is pre-fired in a rotary kiln. The material is held at 500°C for 4 hours, and the pre-fired temperature is 1250°C for 2 hours to obtain ferrite pre-fired granules.

[0059] 8) Grinding ball mill:

[0060] The granules obtained in step 7) were pulverized into 2μm powder by dry ball milling, mixed with water at a ratio of 1:2.7, and 0.4% calcium silicate, 0.3% silica, 1.6% cobalt oxide and 0.1% sorbitol additive were added for secondary ball milling. Continuous ball milling was then carried out to obtain a slurry that completely passed through a 250-mesh standard sieve.

[0061] 9) Molding:

[0062] The slurry obtained in step 8) is concentrated to 70% concentration and then pressed into shape under an 8000 Oe magnetic field.

[0063] 10) Sintering:

[0064] After the molded body from step 9) is kept at 350°C for 4 hours to remove water and glue, it is sintered in air at 1210°C for 2 hours to obtain permanent magnet ferrite.

[0065] The corresponding molecular formulas for this experiment are shown in Table 1:

[0066] Table 1

[0067]

[0068]

[0069] The density instrument, the magnetic performance tester and the chlorine content tester are used to test the performance of the permanent magnet ferrite, and the corresponding magnetic properties of the experiment are shown in table 2:

[0070] Table 2

[0071]

[0072] The technical key point of the application is to provide a method for preparing permanent magnet ferrite, which uses high-chlorine iron red as raw material, adopts phase molecular formula Ca (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 , and realizes the performance of permanent magnet ferrite remanence >=4250Gs and intrinsic coercive force >=4400Oe through iron red polycondensation reaction, neutralization and crushing.

[0073] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0074] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing permanent magnet ferrite, characterized in that, Includes the following steps: 1) Iron oxide red condensation reaction: High-chlorinated iron oxide red and solvent are thoroughly mixed in proportion, and a pH adjuster is added under stirring to carry out the condensation reaction. After aging polymerization, a slurry with pH 4.0-4.5 is obtained; the pH adjuster is calcium aluminate powder. 2) Neutralization and concentration: Extract the slurry obtained in step 1), add an alkaline solvent while stirring to bring the pH of the solution to 6-7, then allow it to settle and drain to obtain a slurry with a concentration of 40%-50%; the alkaline solvent is a dilute ammonia solution with a pH of 8-9. 3) Weighing and proportioning: Mix the raw materials according to the molecular formula Ca... (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 Prepare the slurry by calculating the actual required weight of iron red slurry based on the slurry concentration and iron red material ratio obtained in step 2). Weigh the required slurry weight in a weighing tank and mix it with other materials, and add a dispersant; where A is one or more of the elements Ba, La, and Bi. 4) Crushing, concentrating, and pre-calcining: The slurry obtained in step 3) is crushed by crushing equipment, then concentrated, and the concentrated slurry is pre-calcined in a rotary kiln to obtain ferrite pre-calcined granules. Crushing, ball milling, and molding: The pre-burnt granules obtained in step 4) are crushed by dry ball milling, and water and additives are added for secondary ball milling. The continuous ball milling yields a slurry of 250 mesh. The slurry is then concentrated and pressed into shape under a magnetic field. 6) Sintering: After the molded body from step 5) is kept at 300-400℃ for 3-4 hours to remove water and glue, it is sintered in air to obtain permanent magnet ferrite.

2. The method for preparing permanent magnet ferrite according to claim 1, characterized in that, The high-chlorinated iron red mentioned in step 1) refers to iron red with a chlorine content of 0.5-5%, and the solvent is water, with a mass ratio of high-chlorinated iron red to water solvent of 1:1-3.

3. The method for preparing permanent magnet ferrite according to claim 1, characterized in that, The dispersant mentioned in step 3) is oleic acid, and the molecular formula of the phase is Ca. (1-x-y) Sr x A y Fe (2n-z) Zn z O 19 In the equation, x is 0.2-0.4, y is 0.4-0.5, z is 0.01-0.04, 2n-z is 11-12, and 1-xy≥0.

2.

4. The method for preparing permanent magnet ferrite according to claim 1, characterized in that, In step 4), the material obtained by crushing is ≤1.5% of the material on a 250-mesh standard sieve. The crushed slurry is then concentrated into a 65-70% thick slurry. Pre-firing refers to holding the slurry at 200-600℃ for 4-5 hours, and then holding it at 1150-1300℃ for 1-3 hours.

5. The method for preparing permanent magnet ferrite according to claim 1, characterized in that, The additives mentioned in step 5) are 0.4-0.7% calcium silicate, 0.1-0.3% silica, 1.0-1.6% cobalt oxide, and 0.1-0.3% sorbitol added to the total amount of pre-calcined material; ball milled and pulverized into 2-3 μm powder; the pre-calcined granules are mixed with water at a ratio of 1:2.5-4, concentrated to 70% concentration, and pressed into shape under a magnetic field of 8000-8800 Oe.

6. The method for preparing permanent magnet ferrite according to claim 1, characterized in that, The step 6) mentioned above, where the molded body is decomposed at 300-400℃, refers to the addition of sorbitol being decomposed and discharged at this temperature to avoid the generation of cracks on the surface of the molded body; the sintering temperature is 1160-1230℃, and the holding time is 1-3 hours.

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