A permanent magnet ferrite material, a preparation method and application thereof

Abstract

The application relates to a permanent magnet ferrite material and a preparation method and application thereof, and the preparation method of the permanent magnet ferrite material comprises the following steps: (1) wet ball milling of iron concentrate powder, strontium carbonate and calcium carbonate to obtain a mixed slurry; (2) the mixed slurry obtained in the step (1) is sequentially subjected to drying, oxidation, mineralization treatment and first sintering to obtain permanent magnet ferrite pre-sintered material; (3) the permanent magnet ferrite pre-sintered material obtained in the step (2) is subjected to fine grinding treatment with an additive after water washing to obtain a fine slurry; and (4) the fine slurry obtained in the step (3) is sequentially subjected to wet pressing and second sintering to obtain the permanent magnet ferrite material. The permanent magnet ferrite pre-sintered material with a hexagonal structure is directly prepared by high-temperature solid-phase reaction of the inexpensive iron concentrate powder, strontium carbonate and calcium carbonate, and the further-prepared permanent magnet ferrite material has the characteristics of good rectangular ratio and compactness and excellent magnetic performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet ferrite material, in particular to a kind of permanent magnet ferrite material and its preparation method and application. BACKGROUND

[0002] The preparation of the permanent magnet ferrite pre-fired material usually includes the steps of raw material mixing, granulation, molding, pre-firing and cooling. Through the above steps, permanent magnet ferrite pre-fired material with certain density and mechanical strength can be prepared. These pre-fired materials will be further sintered and magnetized to form the finished permanent magnet ferrite material, which is used to manufacture various permanent magnet devices and products.

[0003] The traditional permanent magnet ferrite pre-fired material is basically made of red iron oxide as raw material. For example, CN 112174654A discloses a preparation method of high-performance permanent magnet ferrite magnetic powder, which includes the following steps: (1) ball milling: mix and ball mill the main materials and additives to obtain a mixture slurry, wherein the main materials include 75-85% red iron oxide and 15-25% barium carbonate by mass fraction; the additives include calcium carbonate, silicon dioxide and clinker pre-fired powder; (2) drying: dry the mixture slurry to obtain permanent magnet ferrite raw material; (3) pre-firing: pre-fire the permanent magnet ferrite raw material to obtain pre-fired material; (4) crushing: dry crushing the pre-fired material to obtain the high-performance permanent magnet ferrite magnetic powder. However, using red iron oxide as the main material increases the production cost.

[0004] CN 112071615A discloses a preparation method for improving the magnetic properties of strontium ferrite pre-fired material, which includes the following steps: (1) mixing and uniformizing the ingredients; (2) balling; (3) roasting; (4) powdering. The high-performance strontium ferrite pre-fired material of the invention uses ultra-pure magnetite powder as raw material, and also adds a small amount of rare earth element holmium (Ho) and conventional additives strontium carbonate, calcium carbonate and silicon dioxide. After mixing them thoroughly, green balls are prepared. The green balls are first pre-oxidized at a relatively low temperature to oxidize Fe3O4 in the raw material to Fe2O3. After pre-oxidation is completed, roasting is performed to finally obtain the ferrite pre-fired material. However, the purity of the ultra-pure magnetite powder in this method is relatively high, and the content of Si and Al elements is low. The remanence of the strontium ferrite prepared by this method is also relatively low.

[0005] Therefore, in view of the deficiencies of the prior art, it is necessary to provide a permanent magnet ferrite material with low raw material cost, good rectangular ratio and density. SUMMARY

[0006] The present application aims to provide a permanent magnet ferrite material and its preparation method and application, which uses inexpensive iron powder as raw material, generates hexagonal structure permanent magnet ferrite pre-fired material through high-temperature solid-phase reaction, and further sintered with additives to obtain permanent magnet ferrite material with excellent rectangular ratio, density and magnetic properties.

[0007] To achieve the object of the present application, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a preparation method of a permanent ferrite material, which comprises the following steps:

[0009] (1) wet ball milling iron concentrate powder, strontium carbonate and calcium carbonate to obtain a mixed slurry;

[0010] (2) the mixed slurry obtained in step (1) is sequentially subjected to drying, oxidation, mineralization treatment and first sintering to obtain a permanent ferrite pre-sintered material;

[0011] (3) the permanent ferrite pre-sintered material obtained in step (2) is subjected to fine grinding treatment with an additive after water washing to obtain a fine slurry;

[0012] (4) the fine slurry obtained in step (3) is sequentially subjected to wet pressing and second sintering to obtain the permanent ferrite material.

[0013] The preparation method of the permanent ferrite material provided by the present application directly generates a permanent ferrite pre-sintered material with a hexagonal structure from inexpensive iron concentrate powder, strontium carbonate and calcium carbonate through high-temperature solid-phase reaction. First, ferrous oxide in the iron concentrate powder is oxidized, and then impurities such as silicon and calcium carbonate are subjected to mineralization reaction at high temperature, thereby avoiding the reaction of impurities such as silicon, silicon dioxide and silicate with elemental iron to generate ferrous oxide, which further deteriorates the performance of the permanent ferrite. The obtained permanent ferrite pre-sintered material is subjected to water washing to remove soluble silicon salt, and then an additive is introduced to improve the rectangular ratio and density of the permanent ferrite material.

[0014] Preferably, in the composition of the iron concentrate powder in step (1), TFe≥69%, FeO≥30%, and SiO2≥0.4%.

[0015] The content of TFe in the composition of the iron concentrate powder is ≥69%, for example, it can be 69%, 70% or 71%, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0016] The content of FeO in the composition of the iron concentrate powder is ≥30%, for example, it can be 30%, 31% or 32%, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0017] The content of SiO2 in the composition of the iron concentrate powder is ≥0.4%, for example, it can be 0.4%, 0.5% or 0.6%, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0018] Preferably, the molar ratio of the iron concentrate powder to strontium carbonate in step (1) is (6-6.2):1, for example, it can be 6:1, 6.1:1 or 6.2:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0019] Preferably, the molar ratio of the iron concentrate powder to calcium carbonate in step (1) is (110-118):1, for example, it can be 110:1, 112:1, 115:1, 116:1 or 118:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] Preferably, the time of the wet ball milling in step (1) is 3.5-5h, for example, it can be 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0021] Preferably, the average particle size of the powder in the mixed slurry in step (1) is 1-1.2µm, for example, it can be 1µm, 1.05µm, 1.1µm, 1.15µm or 1.2µm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0022] Preferably, the temperature of the drying in step (2) is 90-110℃, for example, it can be 90℃, 95℃, 100℃, 105℃ or 110℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] Preferably, the temperature of the oxidation in step (2) is 650-700℃, for example, it can be 650℃, 660℃, 680℃, 690℃ or 700℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] Preferably, the holding time of the oxidation in step (2) is 1.8-2.2h, for example, it can be 1.8h, 1.9h, 2h, 2.1h or 2.2h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0025] Preferably, the temperature of the mineralization treatment in step (2) is 990-1010℃, for example, it can be 990℃, 995℃, 1000℃, 1005℃ or 1010℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0026] Preferably, the holding time of the mineralization treatment in step (2) is 0.9-1.1h, for example, it can be 0.9h, 0.95h, 1h, 1.05h or 1.1h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] Preferably, the temperature of the first sintering in step (2) is 1280-1320℃, for example, it can be 1280℃, 1290℃, 1300℃, 1310℃ or 1320℃, but not limited to the listed values, other values not listed in the value range are also applicable.

[0028] Preferably, the holding time of the first sintering in step (2) is 1.8-2.2h, for example, it can be 1.8h, 1.9h, 2h, 2.1h or 2.2h, but not limited to the listed values, other values not listed in the value range are also applicable.

[0029] Preferably, the water washing in step (3) further comprises a step of vibrating and grinding the permanent magnet ferrite pre-sintered material.

[0030] Preferably, the average particle size of the vibrating and grinding treatment to the permanent magnet ferrite pre-sintered material is 4-5µm, for example, it can be 4µm, 4.5µm or 5µm, but not limited to the listed values, other values not listed in the value range are also applicable.

[0031] Preferably, the additive in step (3) comprises red iron oxide.

[0032] Preferably, the average particle size of the red iron oxide is 1.9-2.1µm, and the Fe2O3 in the red iron oxide is ≥99.2%.

[0033] The average particle size of the red iron oxide is 1.9-2.1µm, for example, it can be 1.9µm, 1.95µm, 2µm, 2.05µm or 2.1µm, but not limited to the listed values, other values not listed in the value range are also applicable.

[0034] The Fe2O3 in the red iron oxide is ≥99.2%, for example, it can be 99.2%, 99.3% or 99.4%, but not limited to the listed values, other values not listed in the value range are also applicable.

[0035] In the present application, due to the low purity of the iron powder, although the content of iron oxide increases after oxidation, compared with the pre-sintered material prepared by red iron oxide, the purity of SrO·6Fe2O3 obtained by pre-sintering is still low, therefore, high-purity red iron oxide is added during preparation to increase the content of iron oxide, and the particle size of the red iron oxide is finer than that of the vibrating and grinding treated permanent magnet ferrite pre-sintered material, which is beneficial to achieve the maximum uniformity of the powder.

[0036] Preferably, the mass fraction of the red iron oxide is 0.3-0.6% of the mass fraction of the water-washed permanent magnet ferrite pre-fired material, for example, it can be 0.3%, 0.4%, 0.5% or 0.6%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] Preferably, the additive in step (3) further comprises calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid.

[0038] Preferably, the total mass fraction of the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid is 1.3-3.1% of the mass fraction of the water-washed permanent magnet ferrite pre-fired material, for example, it can be 1.3%, 1.95%, 2.2%, 2.5% or 3.1%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0039] Among the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid, the calcium carbonate is 0.6-1.3%, the silicon dioxide is 0.2-0.6%, the strontium carbonate is 0.2-0.6%, the calcium gluconate is 0.2-0.4%, and the boric acid is 0.1-0.2%.

[0040] The calcium carbonate is 0.6-1.3%, for example, it can be 0.6%, 1%, 1.2% or 1.3%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0041] The silicon dioxide is 0.2-0.6%, for example, it can be 0.2%, 0.4%, 0.5% or 0.6%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0042] The strontium carbonate is 0.2-0.6%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5% or 0.6%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0043] The calcium gluconate is 0.2-0.4%, for example, it can be 0.2%, 0.3% or 0.4%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0044] The boric acid is 0.1-0.2%, for example, it can be 0.1%, 0.15% or 0.2%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0045] Preferably, the fine grinding treatment in step (3) has an average particle size of 0.85-0.95 µm in the obtained fine material slurry, which may be 0.85 µm, 0.88 µm, 0.9 µm, 0.92 µm or 0.95 µm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0046] Preferably, the wet pressing forming in step (4) is performed in a press with a forming magnetic field of 6000 Gs.

[0047] Preferably, the second sintering in step (4) has a temperature of 1240-1260 ℃, which may be 1240 ℃, 1245 ℃, 1250 ℃, 1255 ℃ or 1260 ℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0048] Preferably, the second sintering in step (4) has a time of 1-2 h, which may be 1 h, 1.2 h, 1.5 h, 1.8 h or 2 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0049] Preferably, as a preferred technical solution of the preparation method of the application, the preparation method comprises the following steps:

[0050] (1) wet ball milling iron concentrate powder, strontium carbonate and calcium carbonate for 3.5-5 h to obtain a mixed material slurry with an average particle size of 1-1.2 µm; the composition of the iron concentrate powder contains TFe≥69%, FeO≥30% and SiO2≥0.4%; the molar ratio of the iron concentrate powder to strontium carbonate is (6-6.2):1; and the molar ratio of the iron concentrate powder to calcium carbonate is (110-118):1;

[0051] (2) the mixed material slurry obtained in step (1) is sequentially subjected to drying at 90-110 ℃, oxidation at 650-700 ℃ for 1.8-2.2 h, mineralization treatment at 990-1010 ℃ for 0.9-1.1 h, and first sintering at 1280-1320 ℃ for 1.8-2.2 h to obtain permanent magnet ferrite pre-sintered material;

[0052] (3) the permanent magnet ferrite pre-sintered material obtained in step (2) is subjected to vibration grinding treatment to have an average particle size of 4-5 µm, and after water washing, fine grinding treatment is performed with an additive to obtain a fine material slurry with an average particle size of 0.85-0.95 µm of the powder;

[0053] The additive comprises iron oxide red; the average particle size of the iron oxide red is 1.9-2.1 μm, Fe2O3 in the iron oxide red is ≥99.2%, the mass fraction of the iron oxide red is 0.3-0.6% of the mass fraction of the water-washed permanent magnet ferrite pre-fired material; the additive further comprises calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid; the total mass fraction of the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid is 1.3-3.1% of the mass fraction of the water-washed permanent magnet ferrite pre-fired material.

[0054] (4) the fine material slurry obtained in step (3) is subjected to wet compression molding in a compression machine with a molding magnetic field of 6000 Gs, and is subjected to second sintering at 1240-1260 ℃ for 1-2 h to obtain the permanent magnet ferrite material.

[0055] In a second aspect, the present application provides a permanent magnet ferrite material prepared by the preparation method of the first aspect.

[0056] The permanent magnet ferrite material provided by the present application has low raw material cost, good magnet rectangular ratio and compactness, and excellent magnetic performance, and can meet the requirements of high-performance permanent magnet ferrite material.

[0057] In a third aspect, the present application provides an application of the permanent magnet ferrite material of the second aspect, and the permanent magnet ferrite material is used in motor equipment.

[0058] Compared with the prior art, the present application has the following beneficial effects:

[0059] (1) The preparation method of the permanent magnet ferrite material provided by the present application directly uses inexpensive iron powder to generate permanent magnet ferrite pre-fired material with a hexagonal structure through high-temperature solid-phase reaction with strontium carbonate and calcium carbonate, wherein the ferrous oxide in the iron powder is first oxidized, and then the impurity silicon and calcium carbonate are subjected to mineralization reaction at high temperature, so as to avoid the reaction of the impurity silicon, silicon dioxide and silicate with elemental iron to generate ferrous oxide and further deteriorate the performance of the permanent magnet ferrite; the obtained permanent magnet ferrite pre-fired material is subjected to water washing to remove soluble silicon salt, and then the addition of additives improves the rectangular ratio and compactness of the permanent magnet ferrite material.

[0060] (2) The permanent magnet ferrite material provided by the present application has low raw material cost, good magnet rectangular ratio and compactness, and excellent magnetic performance, and can be used in motor equipment. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0062] Example 1

[0063] The present example provides a permanent ferrite material, and a preparation method of the permanent ferrite material comprises the following steps:

[0064] (1) wet ball milling iron concentrate powder, strontium carbonate and calcium carbonate for 4.5 h to obtain a mixed slurry with an average particle size of 1.1 µm; the content of TFe in the composition of the iron concentrate powder is 69%, the content of FeO is 30%, and the content of SiO2 is 0.5%; the molar ratio of the iron concentrate powder to strontium carbonate is 6.1:1; and the molar ratio of the iron concentrate powder to calcium carbonate is 115:1;

[0065] (2) the mixed slurry obtained in step (1) is sequentially subjected to 100 ℃ drying, 680 ℃ oxidation for 2 h, 1000 ℃ mineralization treatment for 1 h, and 1300 ℃ first sintering for 2 h to obtain a permanent ferrite pre-sintered material;

[0066] (3) the permanent ferrite pre-sintered material obtained in step (2) is subjected to vibration milling treatment to an average particle size of 4.5 µm, and after water washing, fine grinding treatment is performed with red iron oxide, calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid to obtain a fine slurry with an average particle size of 0.9 µm;

[0067] the average particle size of the red iron oxide is 2 µm, and the content of Fe2O3 in the red iron oxide is 99.5%; the mass fraction of the red iron oxide is 0.4% of the mass fraction of the permanent ferrite pre-sintered material after water washing; the total mass fraction of the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid is 2.2% of the mass fraction of the permanent ferrite pre-sintered material after water washing; and in terms of the total mass percentage content of 100 wt%, the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid are 1 wt% of calcium carbonate, 0.5 wt% of silicon dioxide, 0.3 wt% of strontium carbonate, 0.2 wt% of calcium gluconate and 0.2 wt% of boric acid;

[0068] (4) the fine slurry obtained in step (3) is subjected to wet compression molding in a press with a molding magnetic field of 6000 Gs, and second sintering at 1250 ℃ for 1.5 h to obtain the permanent ferrite material.

[0069] Example 2

[0070] The present example provides a permanent ferrite material, and a preparation method of the permanent ferrite material comprises the following steps:

[0071] (1) wet ball milling iron concentrate powder, strontium carbonate and calcium carbonate for 3.5 h to obtain a mixed slurry with an average particle size of 1.2 µm; the content of TFe in the composition of the iron concentrate powder is 69%, the content of FeO is 30%, and the content of SiO2 is 0.5%; the molar ratio of the iron concentrate powder to strontium carbonate is 6.2:1; the molar ratio of the iron concentrate powder to calcium carbonate is 118:1;

[0072] (2) the mixed slurry obtained in step (1) is sequentially subjected to 90℃ drying, 650℃ oxidation for 2.2 h, 990℃ mineralization treatment for 1.1 h, and 1280℃ first sintering for 2.2 h to obtain a permanent magnet ferrite pre-sintered material;

[0073] (3) the permanent magnet ferrite pre-sintered material obtained in step (2) is subjected to vibration milling treatment to an average particle size of 5 µm, and after water washing, fine grinding treatment is performed with red iron oxide, calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid to obtain a fine slurry with an average particle size of 0.95 µm;

[0074] the average particle size of the red iron oxide is 2.1 µm, and the content of Fe2O3 in the red iron oxide is 99.2%; the mass fraction of the red iron oxide is 0.3% of the mass fraction of the permanent magnet ferrite pre-sintered material after water washing; the total mass fraction of the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid is 2.5% of the mass fraction of the permanent magnet ferrite pre-sintered material after water washing; based on a total mass percentage content of 100 wt%, among the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid, the calcium carbonate is 1.2 wt%, the silicon dioxide is 0.4 wt%, the strontium carbonate is 0.4 wt%, the calcium gluconate is 0.4 wt%, and the boric acid is 0.1 wt%;

[0075] (4) the fine slurry obtained in step (3) is subjected to wet compression molding in a press with a molding magnetic field of 6000 Gs, and second sintering at 1240℃ for 2 h to obtain the permanent magnet ferrite material.

[0076] Example 3

[0077] The present embodiment provides a kind of permanent magnet ferrite material, the preparation method of the permanent magnet ferrite material includes the following steps:

[0078] (1) wet ball milling iron concentrate powder, strontium carbonate and calcium carbonate for 5 h to obtain a mixed slurry with an average particle size of 1 µm; the content of TFe in the composition of the iron concentrate powder is 69%, the content of FeO is 30%, and the content of SiO2 is 0.5%; the molar ratio of the iron concentrate powder to strontium carbonate is 6:1; the molar ratio of the iron concentrate powder to calcium carbonate is 110:1;

[0079] (2) The mixed slurry obtained in step (1) is sequentially subjected to drying at 110°C, oxidation at 700°C for 1.8h, mineralization treatment at 1010°C for 0.9h, and first sintering at 1320°C for 1.8h to obtain a permanent magnet ferrite pre-sintered material;

[0080] (3) The permanent magnet ferrite pre-sintered material obtained in step (2) is subjected to vibration milling treatment until the average particle size is 4µm, and then subjected to fine grinding treatment with red iron oxide, calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate, and boric acid after water washing to obtain a fine slurry with an average particle size of 0.85µm;

[0081] The average particle size of the red iron oxide is 1.9µm, and the content of Fe2O3 in the red iron oxide is 99.3%; the mass fraction of the red iron oxide is 0.6% of the mass fraction of the permanent magnet ferrite pre-sintered material after water washing; the total mass fraction of the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate, and boric acid is 1.95% of the mass fraction of the permanent magnet ferrite pre-sintered material after water washing; in terms of total mass percentage, among the calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate, and boric acid, the mass percentage of calcium carbonate is 0.6%, the mass percentage of silicon dioxide is 0.4%, the mass percentage of strontium carbonate is 0.5%, the mass percentage of calcium gluconate is 0.3%, and the mass percentage of boric acid is 0.15%;

[0082] (4) The fine slurry obtained in step (3) is subjected to wet compression molding in a press with a molding magnetic field of 6000Gs, and then subjected to second sintering at 1260°C for 1h to obtain the permanent magnet ferrite material.

[0083] Example 4

[0084] This example provides a permanent magnet ferrite material, which is different from example 1 in that the molar ratio of the iron powder to calcium carbonate in step (1) is adjusted to 120:1, and the rest is the same as example 1.

[0085] Example 5

[0086] This example provides a permanent magnet ferrite material, which is different from example 1 in that the molar ratio of the iron powder to calcium carbonate in step (1) is adjusted to 108:1, and the rest is the same as example 1.

[0087] Example 6

[0088] This example provides a permanent magnet ferrite material, which is different from example 1 in that the oxidation temperature in step (2) is adjusted to 600°C, and the rest is the same as example 1.

[0089] Example 7

[0090] The present example provides a permanent magnet ferrite material, which is different from example 1 in that the temperature of the oxidation in step (2) is adjusted to 750°C, and the rest is the same as example 1.

[0091] Example 8

[0092] The present example provides a permanent magnet ferrite material, which is different from example 1 in that the temperature of the mineralization in step (2) is adjusted to 950°C, and the rest is the same as example 1.

[0093] Example 9

[0094] The present example provides a permanent magnet ferrite material, which is different from example 1 in that the temperature of the mineralization in step (2) is adjusted to 1050°C, and the rest is the same as example 1.

[0095] Comparative Example 1

[0096] The present comparative example provides a permanent magnet ferrite material, which is different from example 1 in that calcium carbonate is not introduced in step (1), and the rest is the same as example 1.

[0097] Comparative Example 2

[0098] The present comparative example provides a permanent magnet ferrite material, which is different from example 1 in that there is no oxidation step in step (2), and the rest is the same as example 1.

[0099] Comparative Example 3

[0100] The present comparative example provides a permanent magnet ferrite material, which is different from example 1 in that no additive is introduced in step (3), and the rest is the same as example 1.

[0101] The permanent magnet ferrite materials provided in examples 1-9 and comparative examples 1-3 are tested for magnet performance according to a TYU-2000H magnetic material automatic measuring device, and the results are shown in Table 1.

[0102] Table 1

[0103]

[0104] As can be seen from Table 1, the permanent magnet ferrite material prepared by the preparation method provided by the present application has excellent magnet performance and good rectangularity, and can meet the requirements of high-performance permanent magnet ferrite;

[0105] From the comparison of Example 1 with Example 4, 5, it can be seen that when the molar ratio of iron concentrate and calcium carbonate exceeds the limited range, calcium ions cannot replace strontium ions sufficiently, resulting in coarse grains of the magnet, abnormal grains, and decreased coercivity; from the comparison of Example 1 with Example 6, 7, it can be seen that when the oxidation temperature is too low, the oxidation of ferrous iron cannot be completely achieved, the performance of the prepared permanent magnet ferrite material is reduced, and when the temperature is too high, the oxidation is insufficient, resulting in ferrous phase, decreased Ms, and low magnetic performance; from the comparison of Example 1 with Example 8, 9, it can be seen that when the mineralization temperature is too low, the impurity silicon in the iron concentrate cannot react with calcium carbonate completely, and when the mineralization temperature is too high, non-magnetic phase is generated, reducing the remanence.

[0106] From the comparison of Example 1 with Comparative Example 1, it can be seen that without adding calcium carbonate, the impurity silicon in the iron concentrate cannot be removed, resulting in the reaction of impurity silicon and elemental iron to generate ferrous iron, which deteriorates the performance of the permanent magnet ferrite material; from the comparison of Example 1 with Comparative Example 2, it can be seen that without oxidation treatment, the oxidation of ferrous iron cannot be completely achieved, and the performance of the prepared permanent magnet ferrite material is significantly reduced; from the comparison of Example 1 with Comparative Example 3, it can be seen that without introducing additives, the purity of the pre-fired SrO·6Fe2O3 is low, and the magnetic performance of the permanent magnet ferrite material is reduced.

[0107] In summary, the preparation method of the permanent magnet ferrite material provided by the application directly generates permanent magnet ferrite pre-fired material with a hexagonal structure from inexpensive iron concentrate, strontium carbonate and calcium carbonate through high-temperature solid-phase reaction, wherein the ferrous iron in the iron concentrate is first oxidized, and then the impurity silicon and calcium carbonate are subjected to mineralization reaction at high temperature, thereby avoiding the reaction of impurity silicon, silicon dioxide and silicate with elemental iron to generate ferrous iron, which deteriorates the performance of the permanent magnet ferrite material; the obtained permanent magnet ferrite pre-fired material is washed with water to remove soluble silicon salt, and then additives are introduced to improve the squareness ratio, density and magnetic performance of the permanent magnet ferrite material.

[0108] The permanent magnet ferrite material provided by the application has low raw material cost, good squareness ratio and density, and excellent magnetic performance, and the squareness ratio can reach 0.983, which can be used in motor equipment.

[0109] The above description is merely a specific implementation of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the application.

Claims

1. A method for preparing a permanent magnet ferrite material, characterized in that, The preparation method includes the following steps: (1) Wet ball milling of iron concentrate, strontium carbonate and calcium carbonate to obtain a mixed slurry; (2) The mixed slurry obtained in step (1) is successively dried, oxidized, mineralized and sintered to obtain permanent magnet ferrite pre-sintered material; (3) The pre-sintered permanent magnet ferrite material obtained in step (2) is washed with water and then finely ground with additives to obtain a fine slurry; (4) The fine slurry obtained in step (3) is successively subjected to wet pressing and second sintering to obtain the permanent magnet ferrite material; In step (1), the iron concentrate contains TFe ≥ 69%, FeO ≥ 30%, and SiO2 ≥ 0.4%. The molar ratio of iron concentrate to calcium carbonate is (110-118):1; The temperature of the mineralization treatment in step (2) is 990-1010℃.

2. The preparation method according to claim 1, characterized in that, The molar ratio of iron concentrate to strontium carbonate in step (1) is (6-6.2):

1.

3. The preparation method according to claim 1, characterized in that, The wet ball milling time in step (1) is 3.5-5 hours.

4. The preparation method according to claim 1, characterized in that, The average particle size of the powder in the mixture slurry in step (1) is 1-1.2µm.

5. The preparation method according to claim 1, characterized in that, The drying temperature in step (2) is 90-110℃.

6. The preparation method according to claim 1, characterized in that, The oxidation temperature in step (2) is 650-700℃.

7. The preparation method according to claim 1, characterized in that, The oxidation process in step (2) involves a heat treatment time of 1.8-2.2 hours.

8. The preparation method according to claim 1, characterized in that, The holding time for the mineralization treatment in step (2) is 0.9-1.1h.

9. The preparation method according to claim 1, characterized in that, Step (2) The temperature of the first sintering is 1280-1320℃.

10. The preparation method according to claim 1, characterized in that, Step (2) The holding time for the first sintering is 1.8-2.2h.

11. The preparation method according to claim 1, characterized in that, Before the water washing in step (3), the process also includes a step of vibratory milling of the pre-sintered permanent magnet ferrite material.

12. The preparation method according to claim 11, characterized in that, The average particle size of the pre-sintered permanent magnet ferrite material after the vibration milling process is 4-5µm.

13. The preparation method according to claim 1, characterized in that, The additives mentioned in step (3) include iron oxide red.

14. The preparation method according to claim 13, characterized in that, The average particle size of the iron oxide red is 1.9-2.1 μm, and the Fe2O3 content in the iron oxide red is ≥99.2%.

15. The preparation method according to claim 13, characterized in that, The mass fraction of the iron oxide red is 0.3-0.6% of the mass fraction of the pre-sintered permanent magnet ferrite material after water washing.

16. The preparation method according to claim 1, characterized in that, The additives mentioned in step (3) also include calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate and boric acid.

17. The preparation method according to claim 1, characterized in that, The fine grinding process in step (3) results in an average particle size of 0.85-0.95µm in the fine slurry.

18. The preparation method according to claim 1, characterized in that, The wet pressing in step (4) is carried out in a press with a forming magnetic field of 6000Gs.

19. The preparation method according to claim 1, characterized in that, In step (4), the second sintering temperature is 1240-1260℃.

20. The preparation method according to claim 1, characterized in that, Step (4) The second sintering time is 1-2 hours.

21. The preparation method according to any one of claims 1-20, characterized in that, The preparation method includes the following steps: (1) Wet ball milling of iron concentrate, strontium carbonate and calcium carbonate for 3.5-5 h to obtain a mixed slurry with an average particle size of 1-1.2 µm; the composition of the iron concentrate is TFe≥69%, FeO≥30%, SiO2≥0.4%; the molar ratio of the iron concentrate to strontium carbonate is (6-6.2):1; the molar ratio of the iron concentrate to calcium carbonate is (110-118):1; (2) The mixed slurry obtained in step (1) is successively dried at 90-110℃, oxidized at 650-700℃ for 1.8-2.2h, mineralized at 990-1010℃ for 0.9-1.1h, and sintered at 1280-1320℃ for 1.8-2.2h to obtain permanent magnet ferrite pre-sintered material; (3) The pre-sintered permanent magnet ferrite material obtained in step (2) is subjected to vibration milling to an average particle size of 4-5µm, washed with water and then finely ground with additives to obtain a fine slurry with an average particle size of 0.85-0.95µm. The additives include iron oxide red; the average particle size of the iron oxide red is 1.9-2.1 μm, and the Fe2O3 content in the iron oxide red is ≥99.2%; the mass fraction of the iron oxide red is 0.3-0.6% of the mass fraction of the pre-calcined permanent magnet ferrite material after water washing; the additives also include calcium carbonate, silicon dioxide, strontium carbonate, calcium gluconate, and boric acid; (4) The fine slurry obtained in step (3) is wet-pressed in a press with a molding magnetic field of 6000Gs and then sintered at 1240-1260℃ for 1-2 hours to obtain the permanent magnet ferrite material.

22. A permanent magnet ferrite material, characterized in that, The permanent magnet ferrite material is prepared by the preparation method according to any one of claims 1-21.

23. An application of the permanent magnet ferrite material as described in claim 22, characterized in that, The permanent magnet ferrite material is used in motor equipment.

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