Method for testing magnetism of permanent magnetic ferrite pre-sintered material

Abstract

The invention relates to the technical field of permanent magnetic ferrite pre-sintered materials, and discloses a permanent magnetic ferrite pre-sintered material magnetism test method, which comprises the following steps: placing a pre-sintered material in a glass container, winding a lead on the glass container to prepare a sample to be tested, winding for 28-32 circles, and detecting the inductance value of the sample to be tested by using an inductance value test device, the state of the pre-sintering materials is tested according to the inductance value, the inductance value of the pre-sintering material with the normal pre-sintering temperature is 20-24 [mu] H, the inductance value of the pre-sintering material with the too high pre-sintering temperature is larger than 24 [mu] H, and the inductance value of the pre-sintering material with the too low pre-sintering temperature is smaller than 20 [mu] H; according to the method, the state of the pre-sintered material can be tested by testing the inductance value of the to-be-tested sample, the pre-sintering temperature can be quickly adjusted, and the qualification rate of the pre-sintered material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet ferrite pre-sintered materials, and particularly to a method for testing the magnetism of permanent magnet ferrite pre-sintered materials. Background Art

[0002] Pre-sintering is an important process in the production of permanent magnet ferrites. It is a process in which various raw materials are transformed into hexagonal ferrite through solid-phase reaction under high temperature conditions. The integrity of crystal growth has an important impact on the performance of permanent magnet ferrites. Therefore, it is necessary to pre-test the pre-sintered materials. In the prior art, the method for pre-testing permanent magnet ferrite pre-sintered materials mainly refers to the content disclosed in "Comparative Study on Microwave and Traditional Pre-sintering Processes of Sr-Ca-La-Co Type Hexagonal Ferrite", Li Jindao et al., "Journal of Magnetic Materials and Devices", Vol. 46, No. 2, 2015 for testing. When using this method for testing, it is necessary to perform steps such as dry crushing of pre-sintered particles, wet grinding into slurry, high-temperature sintering, and magnetic detection. The shortest detection time of this method requires 3 days, with a long detection time and low efficiency.

[0003] In view of the above problems, CN112525982B in the prior art discloses a detection method for permanent magnet ferrite pre-sintered materials. In this method, the pre-sintered material particles are loaded into a non-magnetic sample box, and then the sample box is placed in a magnetic measurement device to test the coercivity and intrinsic coercivity of the pre-sintered materials. The pre-sintering state of the pre-sintered materials is judged by the magnitudes of the coercivity and intrinsic coercivity. The detection time of this technical solution is within 15 minutes, which is much lower than the traditional detection method, significantly reducing the detection time and significantly improving the detection efficiency.

[0004] In addition, currently, permanent magnet ferrites are usually made from iron oxide red as raw materials, and the cost of iron oxide red is relatively high. Therefore, in order to reduce the cost of permanent magnet ferrites, the present invention directly performs high-temperature solid-phase reaction on iron ore concentrate powder, strontium carbonate, and additives to generate hexagonal ferrite. However, when pre-testing the above-mentioned pre-sintered materials in this application, it is found that there are extremely significant errors between the results obtained when testing the coercivity and intrinsic coercivity of the pre-sintered materials made from iron ore concentrate powder and the magnetic properties of the finally made permanent magnet ferrites, and the pre-sintering conditions cannot be accurately tested. Summary of the Invention

[0005] In view of the problem of large errors when testing the coercivity and intrinsic coercivity of permanent magnet ferrite pre-sintered materials made from fine iron powder in the prior art, the present invention provides a method for testing the magnetism of permanent magnet ferrite pre-sintered materials. In this method, the pre-sintered material is placed in a glass container, and then a wire is wound around the outside of the glass container to make a sample to be tested. By testing the inductance value of the sample to be tested, the state of the pre-sintered material can be tested, the pre-sintering temperature can be quickly adjusted, and the qualified rate of the pre-sintered material can be improved.

[0006] The specific technical solution of the present invention is as follows: A method for testing the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: placing the pre-sintered material in a glass container, and then winding a wire around the glass container to form a sample to be tested, with the number of winding turns being 28 - 32 turns; using an inductance value testing device to detect the inductance value of the sample to be tested, and testing the state of the pre-sintered material according to the magnitude of the inductance value. The inductance value of the pre-sintered material with normal pre-sintering temperature is 20 - 24 μH, the inductance value of the pre-sintered material with too high pre-sintering temperature is greater than 24 μH, and the inductance value of the pre-sintered material with too low pre-sintering temperature is less than 20 μH.

[0007] The present invention provides a testing method for a permanent magnet ferrite pre-sintered material, which can accurately and quickly test the pre-sintering state of the permanent magnet ferrite pre-sintered material made of fine iron powder, strontium carbonate and additives, can quickly adjust the pre-sintering temperature, and improve the qualification rate of the pre-sintered material.

[0008] The present invention discovers that there is a problem of large error when testing the permanent magnet ferrite pre-sintered material made of fine iron powder, strontium carbonate and additives by using the method disclosed in the prior art CN112525982B. After analysis, it is found that the raw material used in the prior art CN112525982B is iron oxide red, which has no magnetism and its coercivity can be considered close to zero. Therefore, when directly testing the pre-sintered material made of iron oxide red by using a magnetic testing device, the more the iron oxide red is converted into permanent magnet ferrite, the greater the coercivity of the pre-sintered material. Thus, the state of the generated permanent magnet ferrite under different pre-sintering conditions can be directly characterized by the coercivity of the pre-sintered material. However, for the fine iron powder used in the present invention, compared with iron oxide red, it has certain magnetism itself, so its coercivity cannot be considered zero. In addition, the fine iron powder contains impurities such as silicon dioxide, aluminum oxide, sulfur, phosphorus, arsenic, zinc, carbon, manganese, etc., resulting in the inability to accurately determine the coercivity of the fine iron powder, and it is necessary to separately test the coercivity of the fine iron powder, which increases the testing steps and testing time. After many experiments, the present invention discovers that testing the inductance value of the permanent magnet ferrite pre-sintered material made of fine iron powder can characterize the magnetism of the permanent magnet ferrite pre-sintered material, and it has high precision and simple operation.

[0009] Preferably, the particle diameter of the pre-sintered material is 5 - 8 mm.

[0010] Preferably, the pre-sintered material comprises fine iron powder and strontium carbonate.

[0011] Preferably, the pre-sintered material further comprises an additive.

[0012] Preferably, the additive is one or more of calcium carbonate, silicon dioxide, calcium gluconate and boric acid.

[0013] Preferably, the material of the wire is copper.

[0014] Preferably, the diameter of the wire is 1 - 2 mm.

[0015] Preferably, the distance between the outer circle of the wire winding and the end of the glass container is greater than 10 mm.

[0016] Preferably, the diameter of the glass container is 22 - 28 mm.

[0017] Preferably, the length of the glass tube is greater than 70 mm.

[0018] Compared with the prior art, the present application has the following technical effects: This method can test the permanent magnet ferrite presintered material made of fine iron powder. This method places the presintered material in a glass container, and then winds a wire around the outside of the glass container to make a sample to be tested. By testing the inductance value of the sample to be tested, the state of the presintered material can be tested, the presintering temperature can be quickly adjusted, and the qualification rate of the presintered material can be improved. Specific Embodiments

[0019] The present invention will be further described below in conjunction with embodiments.

[0020] Embodiment 1: A method for testing the magnetism of a permanent magnet ferrite presintered material, comprising the following steps: (1) Load 200 g of presintered material with a presintering temperature of 1180 °C (the particle diameter of the presintered material is 5 - 8 μm, and the raw materials of the presintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 circles outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the copper wire winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibratory mill (model ZDM-50ML) to make the permanent magnet ferrite presintered material after measuring the inductance value into presintered material coarse powder. Take 500 g of presintered material coarse powder, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate, and 1 g of boric acid for wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to form a blank, and then place the blank in a muffle furnace at a temperature of 1220 °C for rapid sintering to make a permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence, coercivity, intrinsic coercivity, and maximum magnetic energy product of the permanent magnet ferrite.

[0021] Embodiment 2: A method for testing the magnetism of a permanent magnet ferrite presintered material, comprising the following steps: (1) Load 200 g of pre-sintered material with a pre-sintering temperature of 1190 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of refined iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the pre-sintered material of the permanent magnet ferrite after measuring the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid for wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press and form the fine slurry into a blank under a press with a forming magnetic field of 6000 Gs, and then quickly sinter the blank in a muffle furnace at a temperature of 1220 °C to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0022] Example 3: A method for testing the magnetism of a pre-sintered material of permanent magnet ferrite, comprising the following steps: (1) Load 200 g of pre-sintered material with a pre-sintering temperature of 1200 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of refined iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0023] Example 4: A testing method for the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: (1) Load 200 g of the pre-sintered material with a pre-sintering temperature of 1210 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of refined iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire and both ends of the glass tube after winding is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0024] Example 5: A testing method for the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: (1) Put 200 g of pre-sintered material with a pre-sintering temperature of 1220 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns around the outside of the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibratory mill (model ZDM-50ML) to make the pre-sintered material of the permanent ferrite after measuring the inductance value into a coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid for wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry into a green body under a press with a forming magnetic field of 6000 Gs, and then quickly sinter the green body in a muffle furnace at a temperature of 1220 °C to make a permanent ferrite. Use a vibrating sample magnetometer to test the remanence, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent ferrite.

[0025] Example 6: A method for testing the magnetism of a pre-sintered material of permanent ferrite, comprising the following steps: (1) Put 200 g of pre-sintered material with a pre-sintering temperature of 1230 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns around the outside of the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the pre-sintered material of permanent magnet ferrite after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press and form the fine slurry into a blank under a press with a forming magnetic field of 6000 Gs, and then place the blank in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0026] Example 7: A testing method for the magnetism of a pre-sintered material of permanent magnet ferrite, comprising the following steps: (1) Load 200 g of the pre-sintered material with a pre-sintering temperature of 1240 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of refined iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the pre-sintered material of permanent magnet ferrite after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press and form the fine slurry into a blank under a press with a forming magnetic field of 6000 Gs, and then place the blank in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0027] Example 8: A testing method for the magnetism of a pre-sintered material of permanent magnet ferrite, comprising the following steps: (1) Load 200 g of pre-sintered material with a pre-sintering temperature of 1250 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder:strontium carbonate:additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns around the outside of the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibratory mill (model ZDM-50ML) to make the pre-sintered material of the permanent ferrite after measuring the inductance value into a coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid for wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then quickly sinter the green body in a muffle furnace at a temperature of 1220 °C to make a permanent ferrite. Use a vibrating sample magnetometer to test the remanence, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent ferrite.

[0028] Example 9: A method for testing the magnetism of a pre-sintered material of permanent ferrite, comprising the following steps: (1) Load 200 g of pre-sintered material with a pre-sintering temperature of 1260 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder:strontium carbonate:additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns around the outside of the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into pre-sintered material coarse powder. Take 500 g of pre-sintered material coarse powder, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press and form the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0029] Example 10: A method for testing the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: (1) Load 200 g of pre-sintered material with a pre-sintering temperature of 1270 °C (the particle diameter of the pre-sintered material is 5-8 μm, and the raw materials of the pre-sintered material are in a mass ratio of refined iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the copper wire and both ends of the glass tube after winding is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into pre-sintered material coarse powder. Take 500 g of pre-sintered material coarse powder, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press and form the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0030] Example 11: A method for testing the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: (1) Put 200 g of pre-sintered material with a pre-sintering temperature of 1280 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the pre-sintered material of the permanent magnet ferrite after measuring the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate and 1 g of boric acid for wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then quickly sinter the green body in a muffle furnace at a temperature of 1220 °C to make a permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence, coercivity, intrinsic coercivity and maximum magnetic energy product of the permanent magnet ferrite.

[0031] Example 12: A method for testing the magnetism of a pre-sintered material of permanent magnet ferrite, comprising the following steps: (1) Put 200 g of pre-sintered material with a pre-sintering temperature of 1290 °C (the particle diameter of the pre-sintered material is 5 - 8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate, and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make a permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity, and maximum magnetic energy product of the permanent magnet ferrite.

[0032] Example 13: A method for testing the magnetism of a permanent magnet ferrite pre-sintered material, comprising the following steps: (1) Load 200 g of the pre-sintered material with a pre-sintering temperature of 1300 °C (the particle diameter of the pre-sintered material is 5-8 μm, and the raw materials of the pre-sintered material are in a mass ratio of fine iron powder: strontium carbonate: additive = 87:12:1) into a glass tube (with a diameter of 25 mm and a length of 60 mm), and then use a wire to wind 30 turns outside the glass tube to make a sample to be tested. The wire is a copper wire with a diameter of 1.5 mm, the length of the copper wire is 2.2 m, and the distance between the outer circle of the copper wire after winding and both ends of the glass tube is greater than 10 mm; (2) Use an LCR tester (model: Agilent 4284A LCR) to test the sample to be tested and measure the inductance value of the sample to be tested; (3) Use a vibration mill (model ZDM-50ML) to make the permanent magnet ferrite pre-sintered material after testing the inductance value into coarse powder of the pre-sintered material. Take 500 g of the coarse powder of the pre-sintered material, 6 g of calcium carbonate, 1.25 g of silicon dioxide, 0.9 g of calcium gluconate, and 1 g of boric acid, and carry out wet ball milling for 14 h to make a fine slurry with a particle size of 1 μm. Wet press the fine slurry under a press with a forming magnetic field of 6000 Gs to make a green body, and then place the green body in a muffle furnace at a temperature of 1220 °C for rapid sintering to make a permanent magnet ferrite. Use a vibrating sample magnetometer to test the remanence performance, coercivity, intrinsic coercivity, and maximum magnetic energy product of the permanent magnet ferrite.

[0033] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the method disclosed in CN112525982B is used for testing.

[0034] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the method disclosed in CN112525982B is used for testing.

[0035] Comparative Example 3: The difference between Comparative Example 3 and Example 3 lies in that the method disclosed in CN112525982B is adopted for testing.

[0036] Comparative Example 4: The difference between Comparative Example 4 and Example 4 lies in that the method disclosed in CN112525982B is adopted for testing.

[0037] Comparative Example 5: The difference between Comparative Example 5 and Example 5 lies in that the method disclosed in CN112525982B is adopted for testing.

[0038] Comparative Example 6: The difference between Comparative Example 6 and Example 6 lies in that the method disclosed in CN112525982B is adopted for testing.

[0039] Comparative Example 7: The difference between Comparative Example 7 and Example 7 lies in that the method disclosed in CN112525982B is adopted for testing.

[0040] Comparative Example 8: The difference between Comparative Example 8 and Example 8 lies in that the method disclosed in CN112525982B is adopted for testing.

[0041] Comparative Example 9: The difference between Comparative Example 9 and Example 9 lies in that the method disclosed in CN112525982B is adopted for testing.

[0042] Comparative Example 10: The difference between Comparative Example 10 and Example 10 lies in that the method disclosed in CN112525982B is adopted for testing.

[0043] Comparative Example 11: The difference between Comparative Example 11 and Example 11 lies in that the method disclosed in CN112525982B is adopted for testing.

[0044] Comparative Example 12: The difference between Comparative Example 12 and Example 12 lies in that the method disclosed in CN112525982B is adopted for testing.

[0045] Comparative Example 13: The difference between Comparative Example 13 and Example 13 lies in that the method disclosed in CN112525982B is adopted for testing.

[0046] The magnetic properties of the magnets made of the presintered materials of Examples 1 to 13 and Comparative Examples 1 to 13 are tested. The test items are remanence (Br), coercivity (HcB), intrinsic coercivity (HcJ), and maximum magnetic energy product (BHmax). The test results are shown in Tables 1 and 2.

[0047] Table 1 Test results of Examples 1 to 13 Table 2 Test results of Comparative Examples 1 to 13 As shown in Table 1, in Examples 1 to 13, the inductance values of the pre-sintered materials at the pre-sintering temperatures from 1180°C to 1300°C and the magnetic properties of the magnets made from the pre-sintered materials were tested respectively. It can be seen from the results that when the pre-sintering temperature is 1210 - 1230°C, the magnetic properties of the magnets made from the pre-sintered materials are all qualified, while when the temperature is lower than 1210°C and higher than 1230°C, the magnetic properties of the magnets made from the pre-sintered materials are all unqualified. And from the results of the inductance values of the pre-sintered materials, it can be seen that there is a corresponding relationship between the inductance value of the pre-sintered material and the qualified rate of the magnetic properties of the magnet made from the pre-sintered material, that is, when the inductance value of the pre-sintered material is 20 - 24, the magnetic properties of the magnets made from the pre-sintered materials are all qualified, while when the inductance value is lower than 20 μH or higher than 24 μH, the magnetic properties of the magnets made from the pre-sintered materials are all unqualified.

[0048] As shown in Table 2, in Comparative Examples 1 to 13, the coercivity and intrinsic coercivity of the pre-sintered materials of Examples 1 to 13 were tested by the method disclosed in CN112525982B. The results of Comparative Examples 1 to 13 found that when the pre-sintering temperature is too low, the difference between the relatively low pre-sintering temperature and the normal pre-sintering temperature can still be distinguished, but when the pre-sintering temperature is too high, the difference from the normal pre-sintering temperature cannot be distinguished. Therefore, when using the method disclosed in CN112525982B to test the pre-sintered materials made of fine iron powder, there is a situation where the relatively high pre-sintering temperature cannot be distinguished, resulting in an increase in the unqualified rate of the products.

[0049] The present invention further explored the conditions for testing the inductance value of the pre-sintered material. After analysis, it was found that the number of winding turns has a significant impact on the accuracy of the inductance value. The difference in the inductance value is very significant when the number of winding turns is between 28 and 32 turns, while the numerical difference in the inductance value is not significant when the number of differential winding turns is less than 28, and the difference is the most significant when the number of winding turns is 30.

[0050] In addition, the present invention also found that the magnitude of the inductance value can also judge the magnetic properties of the magnet made from the pre-sintered material. Among them, when the inductance value is 22 μH, the magnet has the optimal magnetic properties. Therefore, the pre-sintered material that can make a magnet with the optimal magnetic properties can be determined by the inductance value.

[0051] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for testing the magnetism of permanent ferrite pre-sintered materials, characterized in that, Including the following steps: Place the presintered material in a glass container, then wind a wire around the glass container to make a sample to be tested. The number of winding turns is 28 - 32 turns. Use an inductance value testing device to detect the inductance value of the sample to be tested, and test the state of the presintered material according to the size of the inductance value. The inductance value of the presintered material with normal presintering temperature is 20 - 24 μH, the inductance value of the presintered material with too high presintering temperature is greater than 24 μH, and the inductance value of the presintered material with too low presintering temperature is less than 20 μH.

2. The method according to claim 1, characterized in that, The particle diameter of the presintered material is 5 - 8 mm.

3. The method according to claim 1, characterized in that, The raw materials of the presintered material include fine iron powder and strontium carbonate.

4. The method according to claim 3, characterized in that, The raw materials of the presintered material also include additives.

5. The method according to claim 4, characterized in that, The additive is one or more of calcium carbonate, silicon dioxide, calcium gluconate, and boric acid.

6. The method according to claim 1, wherein The material of the wire is copper.

7. The method according to claim 1 or 6, characterized in that, The diameter of the wire is 1 - 2 mm.

8. The method according to claim 1, wherein The distance between the outer circle of the wire winding and the end of the glass container is greater than 10 mm.

9. The method according to claim 1, characterized in that, The diameter of the glass container is 22 - 28 mm.

10. The method according to claim 1, characterized in that, The length of the glass tube is greater than 70 mm.

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