Injection sintered ferrite magnet and manufacturing method thereof

Abstract

The invention relates to the technical field of ferrite magnet processing, in particular to an injection sintered ferrite magnet which comprises calcium lanthanum cobalt ferrite magnetic powder and a binder. The atomic general formula of the calcium lanthanum cobalt ferrite magnetic powder is Ca < 1-x-y > Sr < y > La < x > Fe < 2-n-z > Co < z >, the binder comprises paraffin, peanut oil, stearic acid and high-density polyethylene, x, y, z and n representing the molar ratio in the atomic general formula of the calcium-lanthanum-cobalt ferrite magnetic powder are limited to be larger than or equal to 0.45 and smaller than or equal to 0.65, larger than or equal to 0.05 and smaller than or equal to 0.2, larger than or equal to 0.25 and smaller than or equal to 0.4 and larger than or equal to 4.9 and smaller than or equal to 5.5, and the volume fraction of the binder is 52%-58%; the proportion of the paraffin is 50%-60%, the proportion of the peanut oil is 5%-15%, the proportion of the stearic acid is 5%-15%, and the proportion of the high density polyethylene is 20%-30%. By adopting the injection sintering process suitable for the ferrite powder, the thin high-performance ferrite magnet which is difficult to produce by the traditional process and has the wall thickness of less than 3mm is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of ferrite magnet processing, and more particularly to an injection sintered ferrite magnet and a manufacturing method thereof. Background Art

[0002] Permanent magnet motors are more energy-efficient than excitation motors and are widely used in automobiles, home appliances, medical and other fields. In recent years, with the rapid development of energy-saving and environmentally friendly economy, the requirements for high performance and lightweight of permanent magnet motors have been continuously improved, which has put forward higher requirements for permanent magnets. In recent years, in order to meet the performance requirements of high-performance motors for magnets, technical personnel in the industry have developed 12 materials known as the strongest permanent magnet ferrite materials, that is, ferrites made by replacing part of Ca with rare earth elements such as La and Sr, and part of Fe with Co (hereinafter referred to as "CaLaCo ferrites"). Because the magnetic properties of the magnets obtained are significantly higher than those of traditional Sr ferrites and Ba ferrites, the application field of ferrites has been rapidly expanded and they are widely used for various purposes. However, it is still expected to further improve the magnetic properties, especially the requirements for small and lightweight DC motors for automotive electrical equipment and motors are getting stronger and stronger, and the magnets must be thinned, that is, thin high-performance ferrite magnets with a wall thickness of less than 3mm.

[0003] The use of traditional production technology (wet pressing-sintering-grinding) to produce magnetic tiles results in the brittleness of permanent magnets. During the grinding process, it is easy to produce various defects such as cracking and breaking, and the grinding amount is large, which is extremely uneconomical. Therefore, it is difficult to produce thin high-performance ferrite magnets with a wall thickness of less than 3mm using traditional processes. We hope to find a new manufacturing method to meet market demand.

[0004] Therefore, we propose an injection sintered ferrite magnet and a manufacturing method thereof to solve the above problems. Summary of the invention

[0005] In order to overcome the above defects of the prior art, an embodiment of the present invention provides an injection sintered ferrite magnet and a method for manufacturing the same to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: an injection sintered ferrite magnet, comprising calcium lanthanum cobalt ferrite magnetic powder and a binder; The atomic formula of the calcium lanthanum cobalt ferrite magnetic powder is Ca1-x-ySryLaxFe2n-zCoz; The binder includes: paraffin, peanut oil, stearic acid and high-density polyethylene.

[0007] In a preferred embodiment, x, y, z and n representing the molar ratio in the general formula of the calcium lanthanum cobalt ferrite magnetic powder atoms are limited to 0.45≤x≤0.65, 0.05≤y≤0.2, 0.25≤z≤0.4 and 4.9≤n≤5.5.

[0008] In a preferred embodiment, the volume fraction of the binder is 52%-58%.

[0009] In a preferred embodiment, in the binder, paraffin accounts for 50%-60%, peanut oil accounts for 5%-15%, stearic acid accounts for 5%-15%, and high-density polyethylene accounts for 20%-30%.

[0010] In a preferred embodiment, a method for manufacturing an injection sintered ferrite magnet comprises the following production steps: Step 1: Mixing; Calcium lanthanum cobalt ferrite powder and composite binder were mixed on a mixer for 2 hours at a mixing temperature of 145°C; Step 2: feed preparation; The mixed material is granulated on an extruder to make the components more uniform and obtain feed for injection molding; Step 3: injection molding; Directional molding is completed on the injection molding machine, and the injected magnetic tile blank has a smooth surface and no internal defects.

[0011] Step 4: Degreasing; The ceramic tile blank is placed in a solvent composed of n-heptane and trichloroethylene for solvent degreasing to remove the soluble components peanut oil and paraffin. The degreasing temperature is 30℃-36℃ and the degreasing time is 16h. Then, thermal degreasing is performed under vacuum environment to mainly remove the remaining components of high-density polyethylene and stearic acid in the binder. The thermal degreasing temperature is 480°C and the thermal degreasing time is 2 hours. Step 5: sintering; The degreased magnetic tile blank is placed in a muffle furnace for sintering at a heating rate of 6°C / min and a sintering temperature of 1230°C. The temperature is kept for 2 hours and the blank is naturally cooled to room temperature to obtain a sintered ferrite magnet.

[0012] In a preferred embodiment, in step one, paraffin accounts for 55%, peanut oil accounts for 10%, stearic acid accounts for 12%, and high-density polyethylene accounts for 23%.

[0013] In a preferred embodiment, in step 1, paraffin wax, polyethylene glycol, low-density polyethylene and stearic acid are used to form a composite binder.

[0014] In a preferred embodiment, in step three, the processing environment of the injection molding machine is: magnetic field strength is 8000 Oe, injection temperature is 175° C., and pressure is 80 MPa.

[0015] In a preferred embodiment, in step five, the wall thickness of the obtained sintered ferrite magnet is less than 3 mm, and grinding is no longer required.

[0016] Technical effects and advantages of the present invention: Calcium lanthanum cobalt ferrite powder is mixed with a binder to form a uniform injection molding feed, which is then injection molded on an injection molding machine. The obtained molded blank is degreased and sintered in air to manufacture a thin, high-performance ferrite magnet with a wall thickness of less than 3 mm, which is difficult to produce using traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a graph showing the results of measuring magnetic properties in the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0019] In recent years, a powder injection molding (PIM) technology has emerged. It consists of metal powder injection molding (MIM) and ceramic powder injection molding (CIM). It is a new metal and ceramic parts preparation technology. It is a new parts processing technology formed by introducing plastic injection molding technology into the field of powder metallurgy. It is an emerging near-net forming technology developed on the basis of traditional powder metallurgy technology and creatively combined with the injection molding technology of the plastics industry. It is called "the hottest parts forming technology today."

[0020] Powder injection molding (PIM) has many special technical and process advantages: first, it can be mass-produced quickly and automatically, and its process can be precisely controlled; second, due to the flow filling, the green density is uniform; third, due to high-pressure injection, the powder content in the mixture is greatly increased, the shrinkage of the sintered product is reduced, and the product size is precisely controllable, with a tolerance of ±0.1%-0.2% and excellent performance; fourth, no mechanical processing or only a small amount of processing is required, reducing the preparation cost; fifth, it can form complex shapes, with transverse holes, inclined holes, concave and convex surfaces, threads, thin walls, and ceramic special-shaped parts that are difficult to cut, and has broad application prospects.

[0021] The object of the present invention is to provide a thin high-performance ferrite magnet with a wall thickness of less than 3 mm and a method for manufacturing the same.

[0022] Reference Figure 1 ; The present invention is characterized in that calcium lanthanum cobalt ferrite magnetic powder is mixed with a binder to form a uniform injection molding feed, the feed is injection molded on an injection molding machine, the obtained molded blank is degreased, and sintered in air at 1210-1230°C to obtain the final product without grinding.

[0023] The invention is characterized in that: calcium lanthanum cobalt ferrite magnetic powder is used; Its atomic formula is Ca1-x-ySryLaxFe2n-zCoz, wherein x, y, z and n representing the molar ratio are limited to 0.45≤x≤0.65, 0.05≤y≤0.2, 0.25≤z≤0.4, and 4.9≤n≤5.5.

[0024] The invention is characterized in that the volume fraction of the used binder is 52%-58%, and the binder comprises paraffin wax (PW), peanut oil (EO), stearic acid (SA) and high-density polyethylene (HDPE).

[0025] The invention is characterized in that the paraffin wax (PW) accounts for 50%-60% of the binder, the peanut oil (EO) accounts for 5%-15%, the stearic acid (SA) accounts for 5%-15%, and the high-density polyethylene (HDPE) accounts for 20%-30%.

[0026] A method for manufacturing an injection sintered ferrite magnet comprises the following production steps: Step 1: Mixing. Paraffin wax (PW), polyethylene glycol (PEG20000), low-density polyethylene (LDPE) and stearic acid (SA) are used to form a composite binder, in which paraffin wax (PW) accounts for 55%, peanut oil (EO) accounts for 10%, stearic acid (SA) accounts for 12%, and high-density polyethylene (HDPE) accounts for 23%. Calcium lanthanum cobalt ferrite powder (whose composition is Ca0.38Sr0.1La0.52Fe10.05Co0.35) and the composite binder are first mixed on an XSK-160 mixer for 2 hours at a mixing temperature of 145°C.

[0027] Step 2: Feed material preparation: The mixed materials are granulated on a PSJ32 extruder to make the components more uniform and obtain feed material for injection molding.

[0028] Step 3: Injection molding. The directional molding is completed on a CJ-ZZ injection molding machine with a magnetic field strength of 8000Oe, an injection temperature of 175°C, and a pressure of 80MPa. The surface of the injected magnetic tile is smooth and there are no defects inside.

[0029] Step 4: Degreasing. The tile blank is placed in a solvent composed of n-heptane and trichloroethylene (volvol=3:7) for solvent degreasing to remove the soluble components peanut oil (EO) and paraffin (PW). The degreasing temperature is 30~36℃ and the degreasing time is 16h. Then, thermal degreasing is performed under vacuum environment to mainly remove the remaining components high-density polyethylene (HDPE) and stearic acid (SA) in the binder. The thermal degreasing temperature is 480℃ and the thermal degreasing time is 2h.

[0030] Step 5: Sintering. The degreased magnetic tile blank is placed in a muffle furnace for sintering at a heating rate of 6°C / min and a sintering temperature of 1230°C. The temperature is kept for 2 hours and the ceramic tile is naturally cooled to room temperature. The wall thickness of the sintered ferrite magnet is less than 3mm and no grinding is required.

[0031] The results of measuring magnetic properties are as follows Figure 1 shown.

[0032] 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 protection scope of the present invention.

Claims

1. An injection sintered ferrite magnet, characterized in that; It includes calcium lanthanum cobalt ferrite magnetic powder and a binder; The atomic formula of the calcium lanthanum cobalt ferrite magnetic powder is Ca1-x-ySryLaxFe2n-zCoz; The binder includes: paraffin, peanut oil, stearic acid and high-density polyethylene.

2. The injection sintered ferrite magnet according to claim 1, characterized in that: In the general atomic formula of the calcium lanthanum cobalt ferrite magnetic powder, x, y, z and n representing the molar ratio are limited to 0.45≤x≤0.65, 0.05≤y≤0.2, 0.25≤z≤0.4 and 4.9≤n≤5.

5.

3. The injection sintered ferrite magnet according to claim 1, characterized in that: The volume fraction of the binder is 52%-58%.

4. The injection sintered ferrite magnet according to claim 1, characterized in that: Among the binders, paraffin accounts for 50%-60%, peanut oil accounts for 5%-15%, stearic acid accounts for 5%-15%, and high-density polyethylene accounts for 20%-30%.

5. A method for manufacturing an injection sintered ferrite magnet according to any one of claims 1 to 4, characterized in that: The production process includes the following steps: Step 1: Mixing; Calcium lanthanum cobalt ferrite powder and composite binder were mixed on a mixer for 2 hours at a mixing temperature of 145°C; Step 2: feed preparation; The mixed material is granulated on an extruder to make the components more uniform and obtain feed for injection molding; Step 3: injection molding; Directional molding is completed on the injection molding machine, and the injected magnetic tile blank has a smooth surface and no internal defects.

6. Step 4: Degreasing; The tile blank is placed in a solvent composed of n-heptane and trichloroethylene for solvent degreasing to remove the soluble components peanut oil and paraffin. The degreasing temperature is 30°C-36°C and the degreasing time is 16h. Then, thermal degreasing is performed under vacuum environment to mainly remove the remaining components of high-density polyethylene and stearic acid in the binder. The thermal degreasing temperature is 480°C and the thermal degreasing time is 2 hours. Step 5: sintering; The degreased magnetic tile blank is placed in a muffle furnace for sintering at a heating rate of 6°C / min and a sintering temperature of 1230°C. The temperature is kept for 2 hours and the ceramic tile is naturally cooled to room temperature to obtain a sintered ferrite magnet.

7. The method for manufacturing an injection sintered ferrite magnet according to claim 5, characterized in that: In step one, paraffin accounts for 55%, peanut oil accounts for 10%, stearic acid accounts for 12%, and high-density polyethylene accounts for 23%.

8. The method for manufacturing an injection sintered ferrite magnet according to claim 6, characterized in that: In step 1, paraffin wax, polyethylene glycol, low-density polyethylene and stearic acid are used to form a composite binder.

9. The method for manufacturing an injection sintered ferrite magnet according to claim 5, characterized in that: In step three, the processing environment of the injection molding machine is: magnetic field strength is 8000Oe, injection temperature is 175°C, and pressure is 80MPa.

10. The method for manufacturing an injection sintered ferrite magnet according to claim 5, characterized in that: In step 5, the wall thickness of the obtained sintered ferrite magnet is less than 3 mm and no grinding is required.

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