Environment-friendly rolling magnetic powder and manufacturing method thereof

Abstract

The invention relates to the technical field of environment-friendly rolled magnetic powder manufacturing, in particular to an environment-friendly rolled magnetic powder manufacturing method which comprises the following steps that S1, industrial iron oxide red and strontium carbonate serve as raw materials, proportioning is conducted according to the molecular formula of SrO.nFe2O3, and the molar ratio n = 6.0-6.2; s2, uniformly mixing the raw materials, and adding 3.5 wt%-5.0 wt% of strontium chloride and 1.0 wt%-3.0 wt% of calcium carbonate to obtain a mixture; s3, after the mixture is granulated, pre-sintering is conducted at the temperature of 1050-1150 DEG C, and a pre-sintered material is obtained. The invention provides rolled ferrite magnetic powder which is characterized in that the molar ratio n is larger than or equal to 6, calcium carbonate is added before pre-sintering, so that no residual SrO exists in the magnetic powder, the valence state of chromium is inhibited from being converted from trivalent to hexavalent in the annealing process, meanwhile, by adding CaCO3, the pre-sintering temperature can be effectively reduced, crystal grains are controlled to grow in a flaky mode, and the rolled ferrite magnetic powder which is environmentally friendly and high in yield is obtained. The invention relates to rolled magnetic powder with high magnetic performance and a manufacturing method thereof.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally friendly rolled magnetic powder manufacturing, and more particularly to environmentally friendly rolled magnetic powder and a manufacturing method thereof. Background Art

[0002] M-type permanent ferrites can be divided into strontium ferrite and barium ferrite according to their chemical composition, and into sintered permanent ferrite and bonded permanent ferrite according to their application. Bonded permanent ferrites are made by combining permanent ferrite powder with a binder. They feature high dimensional accuracy, excellent mechanical properties, uniform performance across all magnet components, and ease of radial and multi-pole magnetization.

[0003] Bonded ferrites can be divided into extrusion-molded magnets, injection-molded magnets, and rolled-molded magnets (also known as calendared magnets) according to the different molding methods. The manufacturing process of rolled-molded magnets is as follows: magnetic powder is evenly mixed with organic substances such as CPE (chlorinated polyethylene) or NBR (nitrile butadiene rubber), and the magnetic powder is oriented by mechanical force on a calender to obtain an anisotropic magnet. This magnet has both excellent magnetic properties and excellent flexible processing performance, and is widely used in home appliances, toys, automobiles and other fields, such as refrigerator motor magnetic strips, advertising magnetic stickers, box door seals, automobile damping panels, etc.

[0004] With the continuous advancement of technology, the requirements for magnetic strips are becoming increasingly stringent. On the one hand, the magnetic performance requirements are becoming increasingly higher, especially for magnetic strips used in motors. As motor power continues to increase and energy efficiency continues to improve, the performance requirements for magnets are becoming increasingly stringent, requiring both high remanence to increase power and high coercivity to increase torque. On the other hand, the requirements for hexavalent chromium in magnetic powders are becoming increasingly stringent, requiring the hexavalent chromium content in magnetic powders to not exceed 10ppm. The hexavalent chromium reduction process currently used by suppliers of rolled magnetic powders mainly involves pickling after tempering, reducing the hexavalent chromium to trivalent chromium through a reduction method (adding Fe2+) to achieve the purpose of hexavalent chromium reduction. However, due to the need for pickling, this method consumes a large amount of water, and the solution after pickling needs to be treated, which is environmentally unfriendly and costly.

[0005] Therefore, we propose an environmentally friendly rolled magnetic powder and a manufacturing method thereof to solve the above problems. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide an environmentally friendly rolled magnetic powder and a method for manufacturing the same, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: an environmentally friendly method for producing rolled magnetic powder, comprising the following steps:

[0008] Step S1: using industrial grade iron oxide and strontium carbonate as raw materials, the ingredients are prepared according to the molecular formula SrO·nFe2O3, wherein the molar ratio n is 6.0-6.2;

[0009] Step S2: uniformly mixing the raw materials, adding 3.5 wt% to 5.0 wt% of strontium chloride and 1.0 wt% to 3.0 wt% of calcium carbonate to obtain a mixture;

[0010] Step S3: granulating the mixture and pre-calcining it at 1050° C. to 1150° C. to obtain a pre-calcined material;

[0011] Step S4: crushing the calcined material into coarse powder, wherein the average particle size (APD) of the coarse powder is 3 μm to 5 μm;

[0012] Step S5: finely grinding the coarse powder to an average particle size (APD) of 1.0 μm to 1.1 μm to obtain a slurry;

[0013] Step S6: Mix the slurry with water in a mass ratio of 1:3, let it stand for 30 minutes, filter press, and repeat water washing twice;

[0014] Step S7: drying and dispersing the washed slurry to obtain dry powder;

[0015] Step S8: annealing the dried powder at 920° C. to obtain tempered powder;

[0016] Step S9: dispersing and sieving the tempered powder to obtain rolled magnetic powder with a hexavalent chromium content of ≤10 ppm, a remanence of ≥270 mT, and a coercive force of ≥270 kA / m.

[0017] In a preferred embodiment, the purity of iron oxide in step S1 is ≥99%, and the purity of strontium carbonate is ≥98%.

[0018] In a preferred embodiment, the pre-firing temperature in step S3 is 1100° C. to 1150° C., and the pre-firing time is 2 hours to 4 hours.

[0019] In a preferred embodiment, the fine grinding in step S5 is performed using a ball mill, and the APD of the slurry is 1.0 μm to 1.1 μm.

[0020] In a preferred embodiment, the standing time after each water washing in step S6 is 30 minutes, and the number of water washings is 2 times.

[0021] In a preferred embodiment, the annealing time in step S8 is 1.5 hours to 2.5 hours, and the annealing environment is protected by an inert gas.

[0022] In a preferred embodiment, the grains of the rolled magnetic powder grow in a lamellar manner, and the average grain size is 0.8 μm to 1.2 μm.

[0023] In a preferred embodiment, the amount of calcium carbonate added in step S2 is 1.5 wt% to 2.5 wt%.

[0024] In a preferred embodiment, when rolled magnetic powder is used to prepare a magnet, the steps include: mixing the magnetic powder with chlorinated polyethylene, soybean oil and stearic acid in proportion, and obtaining a magnet after mixing, calendering and lamination. The magnet has a remanence of 270 mT and a coercive force of 298 kA / m.

[0025] In a preferred embodiment, the hexavalent chromium content of the rolled magnetic powder is ≤10 ppm, and the magnetic properties meet the requirements of a remanence of 278 mT and a coercive force of 270 kA / m.

[0026] The technical effects and advantages of the present invention are as follows:

[0027] 1. The present invention provides a rolled magnetic powder and a method for manufacturing the same, which are both environmentally friendly and have high magnetic properties. The hexavalent chromium content of the magnetic powder is less than 10 ppm, and the remanence (Br) of the magnet manufactured using the magnetic powder is greater than or equal to 270 mT and the coercive force (Hcj) is greater than 270 kA / m, meeting the requirements for high performance of motors.

[0028] 2. The present invention limits the molar ratio to between 6.0 and 6.2, so that Fe2O3 is slightly surplus, which can maximize the saturation magnetization (Ms) of the magnetic powder. At the same time, the present invention adds calcium carbonate as a sintering aid to effectively reduce the pre-firing temperature and achieve grain refinement. The addition of SrCl2 controls the growth of grains in the lamellar direction, thereby achieving the purpose of improving performance. At the same time, due to the use of an iron-rich formula (molar ratio n≥6) in the present invention, there is no residual SrO in the magnetic powder, which avoids the reaction with Cr2O3 to produce hexavalent chromium during the annealing stage, thereby achieving the purpose of suppressing the production of hexavalent chromium. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of magnetic properties and hexavalent chromium test results of magnetic powder in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0030] Figure 2 Schematic diagram of magnetic property testing of a rolled magnet in Example 2 of the present invention;

[0031] Figure 3 Schematic diagram of magnetic property detection of the rolled magnet in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Reference Figure 1-3 , an environmentally friendly rolled magnetic powder and a method for manufacturing the same, comprising the following steps:

[0034] Step S1: using industrial-grade iron oxide and strontium carbonate as raw materials, the ingredients are prepared according to the molecular formula SrO·nFe2O3, wherein the molar ratio n is 6.0-6.2; in step S1, the purity of the iron oxide is ≥99%, and the purity of the strontium carbonate is ≥98%;

[0035] Step S2: uniformly mixing the raw materials, adding 3.5 wt% to 5.0 wt% of strontium chloride and 1.0 wt% to 3.0 wt% of calcium carbonate to obtain a mixture;

[0036] Step S3: After granulating the mixture, pre-calcining at 1050° C. to 1150° C. to obtain a pre-calcined material; the pre-calcining temperature in step S3 is 1100° C. to 1150° C., and the pre-calcining time is 2 hours to 4 hours;

[0037] Step S4: crushing the calcined material into coarse powder with an average particle size of 3 μm to 5 μm;

[0038] Step S5: finely grinding the coarse powder to an average particle size of 1.0 μm to 1.1 μm to obtain a slurry; the fine grinding in step S5 is performed using a ball mill;

[0039] Step S6: The slurry was mixed with water in a mass ratio of 1:3, allowed to stand for 30 minutes, and then filtered, and washed twice; the standing time after each washing in step S6 was 30 minutes, and the number of washings was 2;

[0040] Step S7: drying and dispersing the washed slurry to obtain dry powder;

[0041] Step S8: annealing the dried powder at 920° C. to obtain tempered powder; the annealing time in step S8 is 1.5 hours to 2.5 hours, and the annealing environment is inert gas protection;

[0042] Step S9: dispersing and sieving the tempered powder to obtain rolled magnetic powder with a hexavalent chromium content of ≤10 ppm, a remanence of ≥270 mT, and a coercive force of ≥270 kA / m.

[0043] The grains of the rolled magnetic powder grow in a lamellar manner, and the average grain size is 0.8 μm to 1.2 μm;

[0044] When the rolled magnetic powder is used to prepare a magnet, the method comprises the following steps: mixing the magnetic powder with chlorinated polyethylene, soybean oil and stearic acid in proportion, kneading, calendering and laminating to obtain a magnet having a remanence of ≥270 mT and a coercive force of ≥270 kA / m;

[0045] Disclosed is an environmentally friendly rolled magnetic powder, wherein the hexavalent chromium content of the rolled magnetic powder is ≤10 ppm, and the magnetic properties satisfy the requirements of remanence ≥270 mT and coercive force ≥270 kA / m.

[0046] Example 1

[0047] Step 1: Use industrial-grade iron oxide and strontium carbonate as raw materials and prepare the ingredients according to the molecular formula SrO·nFe2O3, wherein the purity of iron oxide is 99%, the purity of strontium carbonate is 98%, and n=6.05;

[0048] Step 2: uniformly mixing the raw materials, adding 3.5 wt% of strontium chloride and 1.5 wt% of calcium carbonate during the mixing process to obtain a mixture;

[0049] Step 3: granulating the mixture, and then pre-calcining it at 1120° C. to obtain a pre-calcined material;

[0050] Step 4: coarsely crushing the pre-sintered material to obtain coarse powder with an average particle size of 3.5 μm;

[0051] Step 5: Grind the coarse powder using a ball mill to obtain a slurry with an average particle size of 1.05 μm;

[0052] Step 6: Stir the slurry evenly in a ratio of material to water = 1:3, and let it stand for 30 minutes;

[0053] Step 7: Filter the slurry to remove water, then add an equal amount of water, stir evenly, and let it stand for 30 minutes; repeat this process twice;

[0054] Step 8: drying the washed slurry and dispersing it with a high-speed grinder to obtain dry powder;

[0055] Step nine: annealing the dried powder at 920° C. to obtain tempered powder;

[0056] Step 10: Disperse the tempered powder using a high-speed grinder and sieve to obtain rolled magnetic powder.

[0057] Step 11: Magnetic property testing of rolled magnets:

[0058] ① Weigh 440g magnetic powder, 32g chlorinated polyethylene (CPE), 10g soybean oil and 3g stearic acid;

[0059] ② Use a double-roll mill for mixing at a mixing temperature of (80±2)℃;

[0060] ③Cold rolling: Roll the film on the calender for 3 times, the roller gap is required to be 2.0mm; the roller temperature is required to be (41±3)℃;

[0061] ④Lamination: Cool the film and place it at (22±2)℃ for 60 minutes, then punch it with a small manual punching machine.

[0062] Out a cylindrical film; stack 5 pieces of cylindrical film to form a cylindrical magnetic block with a height of about 10mm;

[0063] ⑤ Use BH tester to test magnetic properties, see the instructions attached Figure 1 ;

[0064] Step 12: The test results of hexavalent chromium of rolled magnetic powder are shown in the attached manual. Figure 1 .

[0065] Comparative Example 1

[0066] Step 1: Use industrial-grade iron oxide and strontium carbonate as raw materials and prepare the ingredients according to the molecular formula SrO·nFe2O3, wherein the purity of iron oxide is 99%, the purity of strontium carbonate is 98%, and n=6.05;

[0067] Step 2: uniformly mixing the raw materials, and adding 3.5 wt% of strontium chloride during the mixing process to obtain a mixture;

[0068] Step 3: granulating the mixture, and then pre-calcining it at 1120° C. to obtain a pre-calcined material;

[0069] Step 4: coarsely crushing the pre-sintered material to obtain coarse powder with an average particle size of 3.5 μm;

[0070] Step 5: Grind the coarse powder using a ball mill to obtain a slurry with an average particle size of 1.05 μm;

[0071] Step 6: Stir the slurry evenly in a ratio of material to water = 1:3, and let it stand for 30 minutes;

[0072] Step 7: Filter the slurry to remove water, then add an equal amount of water, stir evenly, and let it stand for 30 minutes; repeat this process twice;

[0073] Step 8: drying the washed slurry and dispersing it with a high-speed grinder to obtain dry powder;

[0074] Step nine: annealing the dried powder at 920° C. to obtain tempered powder;

[0075] Step 10: Disperse the tempered powder using a high-speed grinder and sieve to obtain rolled magnetic powder.

[0076] Step 11: Magnetic property testing of rolled magnets:

[0077] ① Weigh 440g magnetic powder, 32g chlorinated polyethylene (CPE), 10g soybean oil and 3g stearic acid;

[0078] ② Use a double-roll mill for mixing at a mixing temperature of (80±2)℃;

[0079] ③Cold rolling: Roll the film on the calender for 3 times, the roller gap is required to be 2.0mm; the roller temperature is required to be (41±3)℃;

[0080] ④Lamination: Cool the film and place it at (22±2)℃ for 60 minutes, then punch it with a small manual punching machine.

[0081] Out a cylindrical film; stack 5 pieces of cylindrical film to form a cylindrical magnetic block with a height of about 10mm;

[0082] ⑤ Use BH tester to test magnetic properties, see the instructions attached Figure 1 ;

[0083] Step 12: The test results of hexavalent chromium of rolled magnetic powder are shown in the attached manual. Figure 1 .

[0084] Comparative Example 2

[0085] Step 1: Use industrial-grade iron oxide and strontium carbonate as raw materials and prepare the ingredients according to the molecular formula SrO·nFe2O3, wherein the purity of iron oxide is 99%, the purity of strontium carbonate is 98%, and n=5.7;

[0086] Step 2: uniformly mixing the raw materials, and adding 3.5 wt% of strontium chloride during the mixing process to obtain a mixture;

[0087] Step 3: granulating the mixture, and then pre-calcining it at 1120° C. to obtain a pre-calcined material;

[0088] Step 4: coarsely crushing the pre-sintered material to obtain coarse powder with a particle size of 3.5 μm;

[0089] Step 5: Grind the coarse powder using a ball mill to obtain a slurry, wherein the particle size after grinding is 1.05 μm;

[0090] Step 6: Stir the slurry evenly in a ratio of material to water = 1:3, and let it stand for 30 minutes;

[0091] Step 7: Filter the slurry to remove water, then add an equal amount of water, stir evenly, and let it stand for 30 minutes; repeat this process twice;

[0092] Step 8: drying the washed slurry and dispersing it with a high-speed grinder to obtain dry powder;

[0093] Step nine: annealing the dried powder at 920° C. to obtain tempered powder;

[0094] Step 10: Disperse the tempered powder using a high-speed grinder and sieve to obtain rolled magnetic powder.

[0095] Step 11: Magnetic property testing of rolled magnets:

[0096] ① Weigh 440g magnetic powder, 32g chlorinated polyethylene (CPE), 10g soybean oil and 3g stearic acid;

[0097] ② Use a double-roll mill for mixing at a mixing temperature of (80±2)℃;

[0098] ③Cold rolling: Roll the film on the calender for 3 times, the roller gap is required to be 2.0mm; the roller temperature is required to be (41±3)℃;

[0099] ④Lamination: Cool the film and place it at (22±2)℃ for 60 minutes, then punch it with a small manual punching machine.

[0100] Out a cylindrical film; stack 5 pieces of cylindrical film to form a cylindrical magnetic block with a height of about 10mm;

[0101] ⑤ Use BH tester to test magnetic properties, see the instructions attached Figure 1 ;

[0102] Step 12: The test results of hexavalent chromium of rolled magnetic powder are shown in the attached manual. Figure 1 .

[0103] Example 2

[0104] Step 1: Use industrial-grade iron oxide red and strontium carbonate as raw materials and prepare the ingredients according to the molecular formula SrO·nFe2O3, wherein the purity of iron oxide red is 99%, the purity of strontium carbonate is 98%, and n=5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3;

[0105] Step 2: uniformly mixing the raw materials, adding 3.5 wt% of strontium chloride and 1.5 wt% of calcium carbonate during the mixing process to obtain a mixture;

[0106] Step 3: granulating the mixture, and then pre-calcining it at 1120° C. to obtain a pre-calcined material;

[0107] Step 4: coarsely crushing the pre-sintered material to obtain coarse powder, the coarse powder having an average particle size of 3.5 μm;

[0108] Step 5: Grind the coarse powder using a ball mill to obtain a slurry with a particle size of 1.05 μm;

[0109] Step 6: Stir the slurry evenly in a ratio of material to water = 1:3, and let it stand for 30 minutes;

[0110] Step 7: Filter the slurry to remove water, then add an equal amount of water, stir evenly, and let it stand for 30 minutes; repeat this process twice;

[0111] Step 8: drying the washed slurry and dispersing it with a high-speed grinder to obtain dry powder;

[0112] Step nine: annealing the dried powder at 920° C. to obtain tempered powder;

[0113] Step 10: Disperse the tempered powder using a high-speed grinder and sieve to obtain rolled magnetic powder.

[0114] Step 11: Magnetic properties test of rolled magnets, see the attached manual Figure 2 .

[0115] Example 3

[0116] Step 1: Use industrial-grade iron oxide and strontium carbonate as raw materials and prepare the ingredients according to the molecular formula SrO·nFe2O3, wherein the purity of iron oxide is 99%, the purity of strontium carbonate is 98%, and n=6.1;

[0117] Step 2: uniformly mixing the raw materials, adding 3.5 wt% of strontium chloride during the mixing process, and adding 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, and 3.5 wt% of calcium carbonate respectively to obtain a mixture;

[0118] Step 3: granulating the mixture, and then pre-calcining it at 1120° C. to obtain a pre-calcined material;

[0119] Step 4: coarsely crushing the pre-sintered material to obtain coarse powder with an average particle size of 3.5 μm;

[0120] Step 5: Grind the coarse powder using a ball mill to obtain a slurry with a particle size of 1.05 μm;

[0121] Step 6: Stir the slurry evenly in a ratio of material to water = 1:3, and let it stand for 30 minutes;

[0122] Step 7: Filter the slurry to remove water, then add an equal amount of water, stir evenly, and let it stand for 30 minutes; repeat this process twice;

[0123] Step 8: drying the washed slurry and dispersing it with a high-speed grinder to obtain dry powder;

[0124] Step nine: annealing the dried powder at 920° C. to obtain tempered powder;

[0125] Step 10: Disperse the tempered powder using a high-speed grinder and sieve to obtain rolled magnetic powder.

[0126] Step 11: Magnetic properties test of rolled magnets, see the attached manual Figure 3 .

[0127] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for producing environmentally friendly rolled magnetic powder, characterized in that; The following steps are involved: Step S1: using industrial grade iron oxide and strontium carbonate as raw materials, the ingredients are prepared according to the molecular formula SrO·nFe2O3, wherein the molar ratio n is 6.0-6.2; Step S2: uniformly mixing the raw materials, adding 3.5 wt% to 5.0 wt% of strontium chloride and 1.0 wt% to 3.0 wt% of calcium carbonate to obtain a mixture; Step S3: granulating the mixture and pre-calcining it at 1050° C. to 1150° C. to obtain a pre-calcined material; Step S4: crushing the calcined material into coarse powder, wherein the average particle size (APD) of the coarse powder is 3 μm to 5 μm; Step S5: finely grinding the coarse powder to an average particle size (APD) of 1.0 μm to 1.1 μm to obtain a slurry; Step S6: Mix the slurry with water in a mass ratio of 1:3, let it stand for 30 minutes, filter press, and repeat water washing twice; Step S7: drying and dispersing the washed slurry to obtain dry powder; Step S8: annealing the dried powder at 920° C. to obtain tempered powder; Step S9: dispersing and sieving the tempered powder to obtain rolled magnetic powder with a hexavalent chromium content of ≤10 ppm, a remanence of ≥270 mT, and a coercive force of ≥270 kA / m.

2. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: In step S1, the purity of iron oxide is ≥99%, and the purity of strontium carbonate is ≥98%.

3. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: In step S3, the pre-firing temperature is 1100° C. to 1150° C., and the pre-firing time is 2 hours to 4 hours.

4. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: In step S5, a ball mill is used for fine grinding, and the APD of the slurry is 1.0 μm to 1.1 μm.

5. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: In step S6, the standing time after each water washing is 30 minutes, and the number of water washings is 2 times.

6. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: The annealing time in step S8 is 1.5 hours to 2.5 hours, and the annealing environment is protected by an inert gas.

7. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: The grains of the rolled magnetic powder grow in a lamellar manner, and the average grain size is 0.8 μm to 1.2 μm.

8. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: The amount of calcium carbonate added in step S2 is 1.5 wt% to 2.5 wt%.

9. The environmentally friendly rolled magnetic powder and the method for producing the same according to claim 1, characterized in that: When rolled magnetic powder is used to prepare magnets, the process includes the following steps: mixing the magnetic powder with chlorinated polyethylene, soybean oil and stearic acid in proportion, and obtaining a magnet after kneading, calendering and lamination. The magnet has a remanence of 270 mT and a coercive force of 298 kA / m.

10. The environmentally friendly rolled magnetic powder according to any one of claims 1 to 9, characterized in that: The hexavalent chromium content of the rolled magnetic powder is ≤10ppm, and the magnetic properties meet the requirements of remanence of 278mT and coercive force of 270kA / m.

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