Manufacturing method for reducing defects of magnetic shoe

Abstract

The invention relates to the technical field of magnetic shoe processing, in particular to a manufacturing method for reducing defects of a magnetic shoe, which comprises the following steps of: S1, putting permanent magnetic ferrite magnetic powder and a sintering aid into a ball mill with the length-diameter ratio of 1: 1, carrying out micro-crushing by taking water as a medium, and controlling the particle size distribution of slurry to be as follows: D6: 0.35-0.4 mu m, D10: 0.45-0.5 mu m, D50: 1.1-1.4 mu m and D90: 2.0-3.0 mu m; s2, the slurry obtained in the step 1 is filtered through a 200-mesh screen, and coarse particles with the particle size larger than 200 meshes are removed; s3, the water content of the filtered slurry is adjusted to 30 + / -2 wt%, the slurry is placed in a magnetic field to be subjected to compression molding, and a magnetic shoe pressed blank is obtained; s4, sintering the magnetic tile pressed blank to obtain a sintered magnetic tile cooked blank; and S5, obtaining a permanent magnetic ferrite magnetic shoe finished product. According to the method, by reducing the proportion of the ultrafine powder in the ball-milled slurry, the dehydration efficiency and the forming qualification rate are improved, and the defects of blank pressing defects caused by forming difficulty and the defects of cracking, corner breaking, edge falling and the like generated after sintering are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic tile processing, and more particularly, to a manufacturing method for reducing magnetic tile defects. Background Art

[0002] Permanent ferrite magnets are the core material for manufacturing high-efficiency, energy-saving permanent magnet motors. They enable efficient energy conversion and are crucial for improving motor efficiency and achieving energy conservation and emission reduction. They are widely used in new energy vehicles, white goods, smart manufacturing, and other fields. Due to the design requirements of rotating motors, permanent ferrite magnets, whether used as stators or rotors, are often designed in the form of tiles, or simply magnets. A permanent magnet DC motor requires at least two, and as many as dozens, of these tiles.

[0003] The current wet-pressed magnetic tile manufacturing process is mainly as follows: the permanent magnet ferrite material is put into a ball mill for fine grinding, and a sintering aid is added to control crystal growth and increase density. The wet fine grinding is carried out using water as the medium to the required particle size to obtain a slurry. The obtained slurry is oriented and pressed into a green body in a magnetic field; the green body is placed in a roller kiln for sintering to obtain a sintered magnet; the sintered magnet is ground to obtain a finished magnetic tile.

[0004] During the manufacturing process of magnetic tiles, product defects often occur due to various reasons, which greatly reduces production efficiency and qualification rate and increases production costs. In particular, defects caused during the ball milling stage account for more than 80%, which are specifically reflected in: Due to the excessive proportion of ultrafine powder in the ball milling stage, molding is difficult, the qualified rate of green compacts is low, and the green compacts have many defects. After sintering, cracks, chipping and edge drop are likely to occur. Since the ball mill slurry inevitably contains hard particles, the product will have defects such as sand holes and pinholes after sintering, as shown in the attached figure of the manual. Figure 1 shown.

[0005] Therefore, we proposed a manufacturing method to reduce magnetic tile defects to solve the above problems. Summary of the Invention

[0006] In order to overcome the above-mentioned defects in the prior art, an embodiment of the present invention provides a manufacturing method for reducing defects in magnetic tiles, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A manufacturing method for reducing magnetic tile defects, comprising the following method: Step S1: placing permanent ferrite magnetic powder and sintering aid into a ball mill with an aspect ratio of 1:1, and finely grinding them using water as a medium, controlling the particle size distribution of the slurry to be: D6: 0.35~0.4μm, D10: 0.45~0.5μm, D50: 1.1~1.4μm, D90: 2.0~3.0μm; Step S2: Filter the slurry obtained in step 1 through a 200-mesh sieve to remove coarse particles with a particle size greater than 200 mesh; Step S3: Adjust the moisture content of the filtered slurry to 30±2wt%, place it in a magnetic field and press it into shape to obtain a magnetic tile green compact; Step S4: Sinter the magnetic tile green compact to obtain a sintered magnetic tile green compact; Step S5: Grind the sintered magnetic tile green compact to obtain a finished permanent magnet ferrite magnetic tile.

[0008] In a preferred embodiment, the aspect ratio of the ball mill in step S1 is 1:1, and the D50 particle size of the slurry after micro-grinding is 1.1-1.4 μm.

[0009] In a preferred embodiment, the conditions for magnetic field pressing in step S3 are: The magnetic field strength is 8000 to 10000 Oe, the molding pressure is 5 to 10 MPa, and the molding time is 30 to 60 seconds.

[0010] In a preferred embodiment, the sintering conditions in step S4 are: The heating rate is 5-8°C / min, the sintering temperature is 1200-1220°C, and the holding time is 1.5-2.5 hours.

[0011] In a preferred embodiment, the grinding process in step S5 adopts a multi-station grinder, and the surface of the finished magnetic tile is free of pinholes and sand holes.

[0012] In a preferred embodiment, the sintering aid is a silicate sintering aid, and the added amount is 0.3-1.0% of the total mass of the permanent magnet ferrite powder.

[0013] In a preferred embodiment, the mesh size of the sieve in step S2 is 200 meshes, and there are no particles with a size greater than 75 μm in the filtered slurry.

[0014] Technical effects and advantages of the present invention: 1. By reducing the proportion of ultrafine powder in the ball mill slurry, the dehydration efficiency and the molding qualification rate are improved, and the defects of compacts caused by molding difficulties and defects such as cracking, chipping and edge drop caused by sintering are reduced; 2. At the same time, the coarse particles with a mesh size of more than 200 in the ball mill slurry are filtered out to reduce defects such as sand holes and pinholes in the product after sintering, thereby reducing production costs and improving product qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the surface state of the existing product in the present invention; Figure 2Table 1 is a schematic diagram of the qualified rate of magnetic tile green sheets of Example 1 and Comparative Examples 1-3 in the present invention; Figure 3 Schematic diagram of the qualified rate of magnetic tile grinding in Example 1 and Comparative Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0016] 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.

[0017] Reference Figure 1-3 A manufacturing method for reducing magnetic tile defects, comprising the following method: Step S1: putting permanent ferrite magnetic powder and sintering aid into a ball mill with an aspect ratio of 1:1, and finely grinding them with water as the medium, and controlling the particle size distribution of the slurry to be: D6: 0.35-0.4 μm, D10: 0.45-0.5 μm, D50: 1.1-1.4 μm, D90: 2.0-3.0 μm; the aspect ratio of the ball mill in step S1 is 1:1, and the D50 particle size of the slurry after fine grinding is 1.1-1.4 μm; step S2: filtering the slurry obtained in step 1 through a 200-mesh sieve to remove coarse particles with a particle size greater than 200 mesh; the mesh number of the sieve in step S2 is 200 mesh, and there are no particles with a particle size greater than 75 μm in the filtered slurry; step S3: adjusting the moisture content of the filtered slurry to 30±2 wt%, placing it in a magnetic field for compression molding to obtain a magnetic tile green sheet; the conditions for magnetic field compression molding in step S3 are: The magnetic field strength is 8000-10000 Oe, the forming pressure is 5-10 MPa, and the forming time is 30-60 seconds; Step S4: sintering the magnetic tile green compact to obtain a sintered magnetic tile green compact; the sintering conditions in Step S4 are: The heating rate is 5-8°C / min, the sintering temperature is 1200-1220°C, and the holding time is 1.5-2.5 hours; Step S5: Grinding the sintered magnetic tile blank to obtain a finished permanent magnet ferrite magnetic tile; The grinding process in Step S5 adopts a multi-station grinder, and the surface of the finished magnetic tile is free of pinholes and sand holes.

[0018] The sintering aid is a silicate sintering aid, and the added amount is 0.3-1.0% of the total mass of the permanent magnet ferrite powder.

[0019] Example 1 Step 1: Put the permanent magnet ferrite powder together with the sintering aid into a ball mill with an aspect ratio of 1:1, and grind it into powder with water as the medium. The particle size is controlled at 0.73μm, and the slurry particle size distribution is: D6:0.35~0.4μm, D10:0.45~0.5μm, D50:1.1~1.4μm, D90:2.0~3.0μm; Step 2: Pass the ball mill slurry through a 200-mesh sieve to filter out coarse particles larger than the 200-mesh sieve; Step 3: The moisture content of the finely pulverized slurry is controlled at 30±2wt%, and the slurry is placed in a magnetic field for molding. The magnetic field is applied and pressed. The magnetic field intensity is 8000Oe, the molding pressure is 8MPa, and the molding time is 40s to obtain a magnetic tile green compact. The qualified rate of 100 pieces of compacts is shown in the appendix of the manual. Figure 2 .

[0020] Step 4: Place the magnetic tile green sheet in a sintering furnace and sinter it at a heating rate of 6°C / min and a sintering temperature of 1210°C. Keep it warm for 2 hours and cool it naturally to room temperature to obtain a hot-melt magnetic tile green sheet.

[0021] Step 5: Grind the sintered magnetic tile blank using a multi-station grinder to obtain a permanent magnet ferrite magnetic tile product; the pass rate of 100 magnetic tile blanks to finished products is shown in the attached manual. Figure 3 ; Comparative Example 1 Step 1: Put the pre-sintered magnetic powder together with the sintering aid into a ball mill with an aspect ratio of 1.25:1 and grind it into powder with water as the medium. The particle size is controlled at 0.71μm. The particle size distribution of the slurry is: D6: 0.25~0.3μm, D10: 0.35~0.4μm, D50: 1.2~1.5μm, D90: 2.5~3.5μm; Step 2: Pass the ball mill slurry through a 200-mesh sieve to filter out coarse particles larger than the 200-mesh sieve; Step 3: Control the moisture content of the finely pulverized slurry at 30±2wt%, place it in a magnetic field for molding, apply a magnetic field, and press mold it with a magnetic field strength of 8000Oe, a molding pressure of 8MPa, and a molding time of 40S to obtain a magnetic tile compact; and calculate the qualified rate of 100 compacts.

[0022] Step 4: Place the magnetic tile green sheet in a sintering furnace and sinter it at a heating rate of 6°C / min and a sintering temperature of 1210°C. Keep it warm for 2 hours and cool it naturally to room temperature to obtain a hot-melt magnetic tile green sheet.

[0023] Step 5: Grind the sintered magnetic tile blanks using a multi-station grinder to obtain permanent magnet ferrite magnetic tile products; calculate the pass rate of 100 magnetic tile blanks to finished products.

[0024] The test results are as shown in the attached manual. Figure 2 and instructions attached Figure 3 shown.

[0025] Comparative Example 2 Step 1: Put the permanent magnet ferrite powder together with the sintering aid into a ball mill with an aspect ratio of 1:1, and grind it into powder with water as the medium. The particle size is controlled at 0.73μm, and the slurry particle size distribution is: D6:0.35~0.4μm, D10:0.45~0.5μm, D50:1.1~1.4μm, D90:2.0~3.0μm; Step 2: The moisture content of the finely pulverized slurry is controlled at 30±2wt%, and the slurry is placed in a magnetic field for molding. The magnetic field is applied and pressed. The magnetic field intensity is 8000Oe, the molding pressure is 8MPa, and the molding time is 40s to obtain a magnetic tile green compact. Step 3: Place the magnetic tile green sheet in a sintering furnace and sinter it at a heating rate of 6°C / min and a sintering temperature of 1210°C. Keep the temperature for 2 hours and cool it naturally to room temperature to obtain a hot-melt magnetic tile green sheet. Step 4: Grind the sintered magnetic tile blank using a multi-station grinder to obtain a finished permanent magnet ferrite magnetic tile; The test results are as shown in the attached Figure 2 and instructions attached Figure 3 shown.

[0026] Comparative Example 3 Step 1: Put the permanent magnet ferrite powder together with the sintering aid into a 1.25:1 ball mill and grind it into powder with water as the medium. The particle size is controlled at 0.73μm. The slurry particle size distribution is: D6:0.25~0.3μm, D10:0.35~0.4μm, D50:1.2~1.5μm, D90:2.5~3.5μm; Step 2: The moisture content of the finely pulverized slurry is controlled at 30±2wt%, and the slurry is placed in a magnetic field for molding. The magnetic field is applied and pressed. The magnetic field intensity is 8000Oe, the molding pressure is 8MPa, and the molding time is 40s to obtain a magnetic tile green compact. Step 3: Place the magnetic tile green sheet in a sintering furnace and sinter it at a heating rate of 6°C / min and a sintering temperature of 1210°C. Keep the temperature for 2 hours and cool it naturally to room temperature to obtain a hot-melt magnetic tile green sheet. Step 4: Grind the sintered magnetic tile blank using a multi-station grinder to obtain a finished permanent magnet ferrite magnetic tile.

[0027] Test results are as shown in the attached document. Figure 2 and instructions attached Figure 3 shown.

[0028] 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 manufacturing method for reducing magnetic tile defects, characterized in that; The method comprises the following steps: Step S1: putting permanent ferrite magnetic powder and sintering aid into a ball mill with an aspect ratio of 1:1, and pulverizing them with water as a medium, and controlling the particle size distribution of the slurry to be: D6: 0.35~0.4μm, D10: 0.45~0.5μm, D50: 1.1~1.4μm, D90: 2.0~3.0μm; Step S2: Filter the slurry obtained in step 1 through a 200-mesh sieve to remove coarse particles with a particle size larger than 200 mesh; Step S3: Adjust the moisture content of the filtered slurry to 30±2wt%, place it in a magnetic field and press it into shape to obtain a magnetic tile green compact; Step S4: Sinter the magnetic tile green compact to obtain a sintered magnetic tile green compact; Step S5: Grind the sintered magnetic tile green compact to obtain a finished permanent magnet ferrite magnetic tile.

2. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: The aspect ratio of the ball mill in step S1 is 1:1, and the D50 particle size of the slurry after fine grinding is 1.1-1.4 μm.

3. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: The conditions for magnetic field pressing in step S3 are: The magnetic field strength is 8000 to 10000 Oe, the molding pressure is 5 to 10 MPa, and the molding time is 30 to 60 seconds.

4. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: The sintering conditions in step S4 are: The heating rate is 5-8°C / min, the sintering temperature is 1200-1220°C, and the holding time is 1.5-2.5 hours.

5. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: In step S5, the grinding process adopts a multi-station grinder, and the surface of the finished magnetic tile is free of pinholes and sand holes.

6. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: The sintering aid is a silicate sintering aid, and the added amount is 0.3-1.0% of the total mass of the permanent magnet ferrite powder.

7. The manufacturing method for reducing magnetic tile defects according to claim 1, characterized in that: The mesh size of the sieve in step S2 is 200 meshes, and there are no particles with a particle size greater than 75 μm in the filtered slurry.

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