Sintered ferrite preparation process and sintered ferrite magnet

Abstract

The present invention discloses a preparation process of sintered ferrite and a sintered ferrite magnet. The preparation process includes the following steps: Raw material ratio: Select high-purity iron powder, iron oxide powder, and lanthanum powder as raw materials. According to the chemical formula, with a molar ratio of 5.6 < n < 6.1, the ferrite powder, iron oxide powder, and lanthanum are proportioned, and an appropriate amount of additive is added; Mixing: Put the materials proportioned in S1 into a wet ball milling device, and then adopt the wet ball milling process to crush and mix the materials. In the present invention, by introducing the pulsed electromagnetic field technology during the pressing and forming process, the arrangement density and orientation of the powdery materials can be improved, thereby effectively improving the forming efficiency of the ferrite green body and the performance of the magnet. By introducing nitrogen-containing gas to optimize the sintering environment during the sintering process, the ferrite green body forms a microporous structure to achieve the optimization of the material structure, thereby further improving the performance of the magnet.

Description

Technical Field

[0001] The invention relates to the technical field of ferrite magnet preparation, in particular to a sintered ferrite preparation process and a sintered ferrite magnet. Background Art

[0002] The main raw materials of sintered ferrite include BaFe 12 O 19 and SrFe 12 O 19 , according to the orientation of magnetic crystals, they are divided into isotropic and anisotropic magnets. The anisotropic magnets are oriented along the manufacturing direction and must be magnetized along the direction taken, while the isotropic magnets are not oriented and can be magnetized in any direction, although slightly stronger magnetic induction will be found on the side that is often the smallest on the pressure surface. The magnetic energy product ranges from 1.1MGOe to 4.0MGOe. Sintered ferrite is made by ceramic technology, and its texture is relatively hard. It is also a brittle material. Due to its good temperature resistance and low price, sintered ferrite magnets are widely used in motors, speakers, toys, handicrafts and other fields. It is currently the most widely used permanent magnet material. Ferrite permanent magnet material is also called hard ferrite. This material has a high coercive force and is not easy to demagnetize after magnetization. The raw materials for the preparation of permanent ferrite are mainly strontium oxide or barium oxide and ferric oxide (other chemical components, such as cobalt (Co) and lanthanum (La), are added to some specific high grades to improve its magnetic properties). Permanent ferrites are generally of magnetoplumbite structure and are mainly used in speakers, headphones, motors and various instruments;

[0003] The traditional sintered ferrite magnet preparation process includes the steps of raw material ratio, ball milling, pressing, sintering and magnetic treatment. However, the traditional sintered ferrite preparation method has the problems of complex process and high cost, and it is often difficult to obtain products with stability and high magnetic properties. Therefore, it is urgent to design a sintered ferrite preparation process and a sintered ferrite magnet to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a sintered ferrite preparation process and a sintered ferrite magnet to solve the above-mentioned deficiencies in the prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A sintered ferrite preparation process, the preparation process comprising the following steps;

[0007] S1. Raw material ratio: Select high-purity iron powder, iron oxide powder and lanthanum powder as raw materials, and , with a molar ratio of 5.6 < n < 6.1, proportion the ferrite powder, iron oxide powder and lanthanum, and add an appropriate amount of additives, where the additives are one or more of calcium carbonate, iron(III) oxide and barium oxide;

[0008] S2. Mixing: Put the proportioned materials in S1 into a wet ball milling device, and then use the wet ball milling process to crush and mix the materials. At the same time, add a specific proportion of organic solvent and surfactant to reduce the particle size and improve the uniformity of the powder;

[0009] S3. Granulation: Put the mixed materials in S2 into a granulation device, and through the granulation process, granulate the mixed materials to improve the fluidity and compactibility of the materials, which is conducive to the subsequent forming process. Then, perform pre-sintering treatment on the granulated materials;

[0010] S4. Crushing: Perform coarse crushing and fine crushing treatments on the materials that have been granulated and pre-sintered in S3 respectively;

[0011] S5. Compression molding: Fill the powdered materials crushed in S4 into a mold, and apply an appropriate pressure through a pressing device to form a green body of the desired shape. At the same time, during the compression molding process, introduce the pulsed electromagnetic field technology, and through the high-intensity electromagnetic field treatment in a short time, improve the packing density and orientation of the powder materials;

[0012] S6. Sintering: Place the green body formed by compression molding in S5 in a sintering furnace for sintering treatment. At the same time, during the sintering process, adopt the atmosphere control technology and introduce nitrogen-containing gas at a specific stage to form a microporous structure

[0013] S7. Magnetic regulation: Use the magnetic field regulation technology to further regulate the magnetic properties of the ferrite green body after sintering treatment in S6 to obtain the desired magnetic properties

[0014] S8. Magnetic treatment: Perform double-frequency pulsed magnetic field treatment on the sintered ferrite green body after magnetic regulation in S7. By adjusting the pulse frequency and intensity, further improve the coercivity and residual magnetic induction intensity of the magnet;

[0015] S9. Post-treatment: Perform magnetic annealing and surface treatment on the sintered ferrite after magnetic treatment in S8 to further improve its magnetic properties and stability.

[0016] Preferably, the particle size of the ferrite powder in S1 should be controlled within the range of 5 - 50 microns.

[0017] Preferably, when performing pre-sintering treatment on the granulated materials in S3, the temperature of the pre-sintering equipment is 400 - 700 °C.

[0018] Preferably, when the powdered material is pressed into shape in S5, the pressure of the pressing equipment is controlled within the range of 100-200 MPa.

[0019] Preferably, in S6, when the pressed green body is sintered, the sintering furnace temperature is 1000-1300° C. and maintained for 2-4 hours.

[0020] Preferably, when the temperature in the sintering furnace is 1000-1100° C., nitrogen-containing gas is charged into the sintering furnace, wherein the volume percentage of oxygen is 4-10%.

[0021] Preferably, when the ferrite body is subjected to magnetic treatment in S8, the frequency of the dual-frequency pulse is 80 kHz to 100 kHz, and the intensity of the dual-frequency pulse is 500 Oe to 1500 Oe.

[0022] Preferably, when the crushed powdered material is pressed and formed in S5, the frequency of the pulse electromagnetic field is 50 kHz to 80 kHz, and the intensity of the pulse electromagnetic field is 300 Oe to 700 Oe.

[0023] Preferably, the amount of ferrite powder added in S1 is 71-77%, the amount of iron oxide powder added is 15-20%, the particle size is 1-5 microns, the amount of lanthanum added is 5-15%, the particle size is 1-5 microns, and the amount of the additive added is 0.05-0.1%, and the particle size is 2-3 microns.

[0024] Also provided is a sintered ferrite magnet, which is prepared by using the sintered ferrite preparation process.

[0025] In the above technical scheme, the sintered ferrite preparation process and sintered ferrite magnet provided by the present invention have the following beneficial effects:

[0026] (1) By introducing pulsed electromagnetic field technology during the pressing process, the arrangement density and orientation of the powdered material can be improved, thereby effectively improving the forming efficiency of the ferrite body and the performance of the magnet.

[0027] (2) During the sintering process, nitrogen-containing gas is introduced to optimize the sintering environment, so that the ferrite body forms a microporous structure to optimize the material structure, thereby further improving the performance of the magnet.

[0028] (3) By treating ferrite with dual-frequency pulses, low-frequency pulses can improve the coercive force of ferrite, while high-frequency pulses can help increase the residual magnetic induction intensity, and higher pulse intensity helps improve the magnetic properties of ferrite. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of the preparation process provided for the sintered ferrite preparation process and the sintered ferrite magnet embodiments of the present invention.

[0031] Figure 2 It is a schematic structural diagram of the detailed preparation process provided for the sintered ferrite preparation process and the sintered ferrite magnet embodiments of the present invention.

[0032] Figure 3 It is a schematic structural diagram of the overall structure of the ferrite magnet provided for the sintered ferrite preparation process and the sintered ferrite magnet embodiments of the present invention. Detailed implementation manners

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further introduce the present invention in detail in conjunction with the accompanying drawings.

[0034] As Figure 1-3 shown, the sintered ferrite preparation process and the sintered ferrite magnet provided by the embodiments of the present invention, the preparation process includes the following steps;

[0035] S1. Raw material ratio: Select high-purity iron powder, iron oxide powder and lanthanum powder as raw materials, and according to the chemical formula , with a molar ratio of 5.6 < n < 6.1, proportion the ferrite powder, iron oxide powder and lanthanum, and add an appropriate amount of additives. The additives are one or more of calcium carbonate, iron oxide and barium oxide;

[0036] S2. Mixing: Put the proportioned materials in S1 into a wet ball milling device, and then use the wet ball milling process to crush and mix the materials. At the same time, add a specific proportion of organic solvent and surfactant to reduce the particle size and improve the uniformity of the powder;

[0037] S3. Granulation: Put the mixed materials in S2 into a granulation device, and through the granulation process, granulate the mixed materials to improve the fluidity and compressibility of the materials, which is beneficial to the subsequent forming process. Then, pre-burn the granulated materials;

[0038] S4. Crushing: Coarsely crush and finely crush the materials that have been granulated and pre-burned in S3 respectively;

[0039] S5, pressing and molding: the powdered material crushed in S4 is filled into a mold, and appropriate pressure is applied through a pressing device to form it into a blank of a desired shape. At the same time, during the pressing and molding process, pulsed electromagnetic field technology is introduced to improve the arrangement density and orientation of the powdered material through high-intensity electromagnetic field treatment in a short time;

[0040] S6, sintering: The green body pressed and formed in S5 is placed in a sintering furnace for sintering. At the same time, during the sintering process, atmosphere control technology is used to introduce nitrogen-containing gas at a specific stage to form a microporous structure.

[0041] S7, magnetic control: the ferrite body after sintering in S6 is further magnetically controlled by magnetic field control technology to obtain the required magnetic properties;

[0042] S8, magnetic treatment: the sintered ferrite green body after magnetic regulation in S7 is treated with a dual-frequency pulse magnetic field, and the coercive force and residual magnetic induction intensity of the magnet are further improved by adjusting the pulse frequency and intensity;

[0043] S9, post-processing: subjecting the sintered ferrite after magnetic treatment in S8 to magnetic field annealing and surface treatment to further improve its magnetic properties and stability.

[0044] The particle size of the ferrite powder in S1 should be controlled within the range of 5 to 50 microns. The additive in S1 is one or more of calcium carbonate, ferric oxide and barium oxide. In S3, when the granulated material is pre-sintered, the temperature of the pre-sintering equipment is 400 to 700°C. In S5, when the powdered material is pressed and formed, the pressure of the pressing equipment is controlled within the range of 100 to 200 MPa. In S6, when the pressed green body is sintered, the temperature of the sintering furnace is 1000 to 1300°C and maintained for 2 to 4 hours. When the temperature in the sintering furnace is 1000 to 1100°C, a nitrogen-containing gas is filled into the sintering furnace, wherein the volume percentage of oxygen is 4 ~10%, in S8, when the ferrite blank is subjected to magnetic treatment, the frequency of the dual-frequency pulse is 80kHz to 100kHz, and the intensity of the dual-frequency pulse is 500Oe to 1500Oe, in S5, when the crushed powdered material is pressed and formed, the frequency of the pulsed electromagnetic field is 50kHz to 80kHz, and the intensity of the pulsed electromagnetic field is 300Oe to 700Oe, the ferrite powder addition amount in S1 is 71~77%, the iron oxide powder addition amount is 15~20%, the particle size is 1~5 microns, the lanthanum addition amount is 5~15%, the particle size is 1~5 microns, the additive addition amount is 0.05~0.1%, and the particle size is 2~3 microns.

[0045] Specifically, in this embodiment, by introducing pulsed electromagnetic field technology, the arrangement density and orientation of powdered materials can be improved, and by introducing nitrogen-containing gas to optimize the sintering environment, the performance of the magnet can be significantly improved and the production cost can be reduced. By adopting dual-frequency pulsed magnetic field treatment, the coercive force and residual magnetic induction intensity of the magnet can be improved. The sintered ferrite magnet preparation process of the present invention can significantly improve the performance of the magnet, including the coercive force and residual magnetic induction intensity, while reducing production costs and energy consumption, and has important practical application value.

[0046] Embodiment 1:

[0047] The preparation process comprises the following steps:

[0048] S1, mixing ferrite powder, iron oxide powder and lanthanum with appropriate amount of additives;

[0049] Among them, ferrite powder is 71%, iron oxide powder is added in an amount of 16%, lanthanum is 12.95%, and additives are 0.05%;

[0050] S2, putting the materials after proportioning in S1 into a wet ball milling device, and then using a wet ball milling process to crush and mix the materials;

[0051] S3, placing the mixed materials in S2 into a granulation device, and granulating the mixed materials through a granulation process;

[0052] S4, coarsely crushing and finely crushing the materials that have been granulated and pre-burned in S3 respectively;

[0053] S5, filling the powdered material crushed in S4 into a mold, and applying appropriate pressure through a pressing device to form it into a green body of a desired shape. At the same time, during the pressing process, pulsed electromagnetic field technology is introduced to improve the arrangement density and orientation of the powdered material through high-intensity electromagnetic field treatment in a short period of time;

[0054] The pressing equipment pressure is 120MPa, the pulse electromagnetic field frequency is 55kHz, and the pulse electromagnetic field intensity is 350Oe;

[0055] S6, placing the green body pressed and formed in S5 in a sintering furnace for sintering treatment, and at the same time, during the sintering process, using atmosphere control technology, introducing nitrogen-containing gas at a specific stage to form a microporous structure;

[0056] When the temperature in the sintering furnace is 1000°C, nitrogen-containing gas is charged into the sintering furnace, wherein the volume percentage of oxygen is 5%;

[0057] S7, further controlling the magnetic properties of the ferrite blank after sintering in S6 by magnetic field control technology to obtain the desired magnetic properties;

[0058] S8, treating the sintered ferrite green body after magnetic regulation in S7 with a dual-frequency pulse magnetic field, and further improving the coercive force and residual magnetic induction intensity of the magnet by adjusting the pulse frequency and intensity;

[0059] The frequency of the dual-frequency pulse is 85kHz, and the intensity of the dual-frequency pulse is 600Oe;

[0060] S9, subjecting the sintered ferrite after the magnetic treatment in S8 to magnetic field annealing and surface treatment to further improve its magnetic properties and stability.

[0061] Embodiment 2:

[0062] The preparation process comprises the following steps:

[0063] S1, mixing ferrite powder, iron oxide powder and lanthanum with appropriate amount of additives;

[0064] Among them, ferrite powder is 73%, iron oxide powder is added in an amount of 16.95%, lanthanum is 10%, and additives are 0.05%;

[0065] S2, putting the materials after proportioning in S1 into a wet ball milling device, and then using a wet ball milling process to crush and mix the materials;

[0066] S3, placing the mixed materials in S2 into a granulation device, and granulating the mixed materials through a granulation process;

[0067] S4, coarsely crushing and finely crushing the materials that have been granulated and pre-burned in S3 respectively;

[0068] S5, filling the powdered material crushed in S4 into a mold, and applying appropriate pressure through a pressing device to form it into a green body of a desired shape. At the same time, during the pressing process, pulsed electromagnetic field technology is introduced to improve the arrangement density and orientation of the powdered material through high-intensity electromagnetic field treatment in a short period of time;

[0069] The pressing equipment pressure is 150MPa, the pulse electromagnetic field frequency is 70kHz, and the pulse electromagnetic field intensity is 500Oe;

[0070] S6, placing the green body pressed and formed in S5 in a sintering furnace for sintering treatment, and at the same time, during the sintering process, using atmosphere control technology, introducing nitrogen-containing gas at a specific stage to form a microporous structure;

[0071] When the temperature in the sintering furnace is 1100° C., nitrogen-containing gas is charged into the sintering furnace, wherein the volume percentage of oxygen is 7%;

[0072] S7, further controlling the magnetic properties of the ferrite blank after sintering in S6 by magnetic field control technology to obtain the desired magnetic properties;

[0073] S8, treating the sintered ferrite green body after magnetic regulation in S7 with a dual-frequency pulse magnetic field, and further improving the coercive force and residual magnetic induction intensity of the magnet by adjusting the pulse frequency and intensity;

[0074] The frequency of the dual-frequency pulse is 90kHz, and the intensity of the dual-frequency pulse is 800Oe;

[0075] S9, subjecting the sintered ferrite after the magnetic treatment in S8 to magnetic field annealing and surface treatment to further improve its magnetic properties and stability.

[0076] Embodiment 3:

[0077] The preparation process comprises the following steps:

[0078] S1, mixing ferrite powder, iron oxide powder and lanthanum with appropriate amount of additives;

[0079] Among them, ferrite powder is 76%, iron oxide powder is added in an amount of 16%, lanthanum is 7.9%, and additives are 0.1%;

[0080] S2, putting the materials after proportioning in S1 into a wet ball milling device, and then using a wet ball milling process to crush and mix the materials;

[0081] S3, placing the mixed materials in S2 into a granulation device, and granulating the mixed materials through a granulation process;

[0082] S4, coarsely crushing and finely crushing the materials that have been granulated and pre-burned in S3 respectively;

[0083] S5, filling the powdered material crushed in S4 into a mold, and applying appropriate pressure through a pressing device to form it into a green body of a desired shape. At the same time, during the pressing process, pulsed electromagnetic field technology is introduced to improve the arrangement density and orientation of the powdered material through high-intensity electromagnetic field treatment in a short period of time;

[0084] The pressing equipment pressure is 190MPa, the pulse electromagnetic field frequency is 75kHz, and the pulse electromagnetic field intensity is 650Oe;

[0085] S6, placing the green body pressed and formed in S5 in a sintering furnace for sintering treatment, and at the same time, during the sintering process, using atmosphere control technology, introducing nitrogen-containing gas at a specific stage to form a microporous structure;

[0086] When the temperature in the sintering furnace is 1100° C., nitrogen-containing gas is charged into the sintering furnace, wherein the volume percentage of oxygen is 9%;

[0087] S7, further controlling the magnetic properties of the ferrite blank after sintering in S6 by magnetic field control technology to obtain the desired magnetic properties;

[0088] S8, treating the sintered ferrite green body after magnetic regulation in S7 with a dual-frequency pulse magnetic field, and further improving the coercive force and residual magnetic induction intensity of the magnet by adjusting the pulse frequency and intensity;

[0089] The frequency of the dual-frequency pulse is 95 kHz, and the intensity of the dual-frequency pulse is 1300Oe;

[0090] S9, subjecting the sintered ferrite after the magnetic treatment in S8 to magnetic field annealing and surface treatment to further improve its magnetic properties and stability.

[0091] After testing the results of the ferrites prepared in Example 1, Example 2 and Example 3, it was found that the ferrite prepared in Example 2 had the best effect and could effectively and significantly improve the performance of the ferrite magnet, including the coercive force and residual magnetic induction intensity.

[0092] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A process for preparing sintered ferrite, characterized in that: The preparation process comprises the following steps: S1. Raw material ratio: Select high-purity iron powder, iron oxide powder, and lanthanum powder as raw materials. According to the chemical formula , with a molar ratio of 5.6 < n < 6.1, proportion the ferrite powder, iron oxide powder, and lanthanum, and add an appropriate amount of additives. The additives are one or more of calcium carbonate, iron(III) oxide, and barium oxide; S2, mixing: putting the materials after proportioning in S1 into a wet ball milling device, and then using a wet ball milling process to crush and mix the materials, while adding a specific proportion of organic solvent and surfactant to reduce the particle size and improve the uniformity of the powder; S3, granulation: the mixed materials in S2 are placed in a granulation device, and the mixed materials are granulated through a granulation process to improve the fluidity and compactness of the materials, which is beneficial to the subsequent molding process, and then the granulated materials are pre-burned; S4, crushing: the materials that have been granulated and pre-burned in S3 are subjected to coarse crushing and fine crushing respectively; S5, pressing and molding: the powdered material crushed in S4 is filled into a mold, and appropriate pressure is applied through a pressing device to form it into a blank of a desired shape. At the same time, during the pressing and molding process, pulsed electromagnetic field technology is introduced to improve the arrangement density and orientation of the powdered material through high-intensity electromagnetic field treatment in a short time; When the crushed powdered material is pressed and formed, the frequency of the pulse electromagnetic field is 50kHz to 80kHz, and the intensity of the pulse electromagnetic field is 300Oe to 700Oe; S6, sintering: placing the green body pressed and formed in S5 in a sintering furnace for sintering. Meanwhile, during the sintering process, atmosphere control technology is used to introduce nitrogen-containing gas at a specific stage to form a microporous structure; When the pressed green body is sintered, the temperature of the sintering furnace is 1000-1300°C and maintained for 2-4 hours; when the temperature in the sintering furnace is 1000-1100°C, nitrogen-containing gas is filled into the sintering furnace, wherein the volume percentage of oxygen is 4-10%; S7, magnetic control: the ferrite body after sintering in S6 is further magnetically controlled by magnetic field control technology to obtain the required magnetic properties; S8, magnetic treatment: the sintered ferrite green body after magnetic regulation in S7 is treated with a dual-frequency pulse magnetic field, and the coercive force and residual magnetic induction intensity of the magnet are further improved by adjusting the pulse frequency and intensity; When the ferrite body is subjected to magnetic treatment, the frequency of the dual-frequency pulse is 80 kHz to 100 kHz, and the intensity of the dual-frequency pulse is 500 Oe to 1500 Oe; S9, post-processing: subjecting the sintered ferrite after magnetic treatment in S8 to magnetic field annealing and surface treatment to further improve its magnetic properties and stability.

2. The process for preparing sintered ferrite according to claim 1, characterized in that: The particle size of the ferrite powder in S1 should be controlled within the range of 5 to 50 microns.

3. The process for preparing sintered ferrite according to claim 1, characterized in that: In the above S3, when the granulated material is pre-burned, the temperature of the pre-burning equipment is 400-700°C.

4. The process for preparing sintered ferrite according to claim 1, characterized in that: In S5, when the powdered material is pressed and formed, the pressure of the pressing equipment is controlled within the range of 100-200 MPa.

5. The process for preparing sintered ferrite according to claim 2, characterized in that: The amount of ferrite powder added in S1 is 71-77%, the amount of iron oxide powder added is 15-20%, the particle size is 1-5 microns, the amount of lanthanum added is 5-15%, the particle size is 1-5 microns, and the amount of additives added is 0.05-0.1%, and the particle size is 2-3 microns.

6. Sintered ferrite magnet, characterized in that The sintered ferrite is prepared by the sintered ferrite preparation process according to any one of claims 1 to 5.

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