阅读说明：本技术 一种提高永磁铁氧体磁瓦器件抗折极限的工艺方法 (Process method for improving fracture resistance limit of permanent magnetic ferrite magnetic shoe device ) 是由 马宝 高原 尹春龙 杨冲 赵麟城 舒云峰 蒋伟丽 芦运 吴林熹 彭正佺 张伟 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种提高永磁铁氧体磁瓦器件抗折极限的工艺方法,属于永磁铁氧体技术领域。它包括原料的球磨、压制、烧结和磨削；控制球磨后的原料粒径分布为D0.10：0.4～0.6μm、D0.50：0.8～1.0μm、D0.90：1.9～2.0μm；所述压制采用模具进行压制,模具的单腔注浆流速为15-40mm/s；所述磨削过程中,采用的砂轮目数为150-400目。本发明能在不破坏铁氧体磁性能的同时,提高了抗折强度。(The invention discloses a process method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device, and belongs to the technical field of permanent magnetic ferrites. The method comprises the steps of ball milling, pressing, sintering and grinding of raw materials; controlling the particle size distribution of the ball-milled raw materials to be D0.10: 0.4 to 0.6 μm, D0.50: 0.8 to 1.0 μm, D0.90: 1.9-2.0 μm; the pressing is carried out by adopting a mould, and the single-cavity grouting flow rate of the mould is 15-40 mm/s; in the grinding process, the adopted grinding wheel is 150 meshes and 400 meshes. The invention can improve the rupture strength without destroying the magnetic performance of the ferrite.)

1. A technological method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device comprises the steps of ball milling, pressing, sintering and grinding of raw materials, and is characterized in that: controlling the particle size distribution of the ball-milled raw materials to be D0.10: 0.4 to 0.6 μm, D0.50: 0.8 to 1.0 μm, D0.90: 1.9 to 2.0 μm.

2. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 1, characterized in that: controlling the particle size distribution of the ball-milled raw materials to be D0.10: 0.485 μm, D0.50: 0.949 μm, D0.90: 1.971 μm.

3. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 1, characterized in that: the ball milling time is 9-15 h.

4. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 1, characterized in that: in the ball milling process, the material: ball: the weight ratio of water to water is as follows: (1.2-1.6): (6-8): (1.2-2.0).

5. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 1, characterized in that: the pressing is carried out by adopting a mould, and the single-cavity grouting flow rate of the mould is 15-40 mm/s.

6. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 5, is characterized in that: the single cavity grouting flow rate of the mold is 28.5 mm/s.

7. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 6, is characterized in that: in the pressing process, the grouting pressure of the mould is 6-12 MPa.

8. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 7 is characterized in that: the grouting time of the mould is 7-15 s.

9. The process method for improving the bending limit of the permanent magnetic ferrite magnetic shoe device according to any one of claims 1 to 8, characterized in that: in the grinding process, the adopted grinding wheel is 150 meshes and 400 meshes.

10. The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device according to claim 9, is characterized in that: the mesh number of the grinding wheel is 180 meshes.

Technical Field

The invention belongs to the technical field of permanent magnetic ferrite, and particularly relates to a process method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device.

Background

The magnetic material is a basic functional material in the electronic industry. The permanent magnetic material is an important component of the magnetic material, and plays an important role in the industries such as the electronic industry, the information industry, motorcycles, electric tools industry, automobile industry and the like. The permanent ferrite material is a functional material for generating a magnetic field. The permanent magnetic ferrite belongs to an inorganic non-metal sintering material and has the mechanical properties of high hardness and low toughness, but on one hand, devices produced by the permanent magnetic ferrite often have certain crushing risks and cause quality loss for production enterprises and client motor enterprises, and on the other hand, the production process of the permanent magnetic ferrite magnetic shoe device is divided into a plurality of main stages of slurry (powder) ball milling, pressing, sintering and grinding, and the risk of crushing also exists in the production process.

In the prior art, in order to reduce the risk of damage of a permanent magnetic ferrite magnetic shoe device, a series of improvements are made on the components of the permanent magnetic ferrite to improve the fracture resistance of the permanent magnetic ferrite.

Through retrieval, a patent application document with the Chinese patent application number of 200910098605.8 and the application publication date of 2009, 5 and 18 discloses a permanent magnetic ferrite material with high flexural strength. The patent permanent magnetic ferrite material is prepared from the following raw materials in parts by weight: fe₂O₃85 to 88 parts of SrCO₃12-15 parts of additive, 0.4-0.6 part of SiO₂0.5 to 0.6 part, and 0.1 to 0.3 part of aluminum silicate fiber. Preferably, the addition isThe additive is CaCO₃. The invention has the advantages that: 1. the problem of among the current material rupture strength relatively poor, its magnet damages under vibration, impact, pressure, the big condition of difference in temperature easily is solved, a material of high rupture strength is provided. 2. The permanent magnetic ferrite tile-shaped magnet is used for manufacturing a permanent magnetic ferrite tile-shaped magnet for an automobile motor, and the flexural strength and the compressive strength of the permanent magnetic ferrite tile-shaped magnet are both greater than those of a conventional magnet. 3. The flexural strength of the steel reaches 0.8 to 1.2 x 10⁸N/M²(8～12kgf/mm²). However, the patent has higher equipment requirements and energy consumption requirements for the preparation of the permanent magnetic ferrite pre-sintering material powder, and permanent magnetic ferrite device enterprises with certain scales usually obtain continuous and stable pre-sintering material powder supply through batch procurement instead of self-production.

For another example, a chinese patent application No. 201610754859.0, published as 2017, 1 month, 18 days, discloses a high flexural strength nickel-zinc soft magnetic ferrite material. The raw materials of the patent comprise main materials and auxiliary materials, wherein the weight part ratio of the main materials to the auxiliary materials is 100: 0.06-0.12; the main materials comprise the following components in parts by mole: 30-60 parts of iron oxide, 30-50 parts of zinc oxide, 2-6 parts of nickel oxide, 15-25 parts of nickel protoxide and 4-10 parts of copper oxide; the auxiliary materials comprise the following components in parts by weight: 20-30 parts of vanadium pentoxide, 25-45 parts of bismuth trioxide, 8-12 parts of lanthanum oxide, 14-20 parts of tantalum pentoxide, 3-9 parts of lead dioxide, 12-20 parts of molybdenum trioxide, 8-16 parts of magnesium oxide, 14-22 parts of niobium carbide and 20-35 parts of silicon dioxide. The invention ensures high-frequency performance, and has excellent flexural strength performance and stable performance. However, vanadium pentoxide is a highly toxic substance and has some carcinogenicity, and lead dioxide also has toxicity.

The prior art mostly improves the flexural strength of the permanent magnetic ferrite by improving the material composition, but the flexural strength of the permanent magnetic ferrite is further optimized by controlling the process conditions rarely.

For example, chinese patent application No. 201310748259.X, published as 2014, 5/7, discloses a permanent magnetic ferrite, a method for manufacturing the same, and an ultra-thin permanent magnetic ferrite magnetic shoe. The patent permanent magnetic ferrite comprises the following components in percentage by weight: fe₂O₃: 81-88 parts; SrCO₃: 12-19 parts; la₂O₃: 1.2-5.5 parts; co₂O₃: 0.6-0.8 part; CaCo₃: 1.5-4 parts; SiO 2₂: 0.3 to 1.0 portion. The manufacturing method comprises the steps of material proportioning, wet mixing, precipitation, press forming, presintering, primary crushing, secondary ball milling, forming, sintering and grinding, thus obtaining the permanent magnetic ferrite magnetic shoe. However, the secondary ball milling particle size value provided by the patent is only a measured equivalent average value, the value cannot completely and truly reflect the particle size state of the wet ball milling powder, and the patent does not improve the influence level of the particle size distribution on the secondary sintering reaction mechanism.

Therefore, it is an urgent problem to improve the raw material composition of the permanent magnetic ferrite magnetic shoe device and how to optimize the process for preparing the permanent magnetic ferrite magnetic shoe device to further improve the fracture resistance limit.

Disclosure of Invention

1. Problems to be solved

The invention provides a process method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device, and aims to reduce the growth speed and the growth probability of cracks in the processing process of the permanent magnetic ferrite magnetic shoe device.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a process method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device comprises the steps of ball milling, pressing, sintering and grinding of raw materials, wherein the particle size distribution of the raw materials after ball milling is controlled to be D0.10: 0.4 to 0.6 μm, D0.50: 0.8 to 1.0 μm, D0.90: 1.9-2.0 μm; wherein:

"D0.10: 0.4 to 0.6 μm' represents that the particle diameter is 0.4 to 0.6 μm when the cumulative particle size distribution percentage of the raw material reaches 10%,

"D0.50: 0.8 to 1.0 μm' represents that the particle diameter is 0.8 to 1.0 μm when the cumulative particle size distribution percentage of the raw material reaches 50%,

"D0.90: 1.9 to 2.0 μm' represents that the particle diameter is 1.9 to 2.0 μm when the cumulative particle size distribution percentage of the raw material reaches 90%.

Further, the formula of the raw materials is as follows: 600-800 kg of permanent magnet strontium ferrite pre-sintering material powder, 500-700 kg of waste magnetic steel powder, 100-300 kg of grinding material powder, 12-16 kg of calcium carbonate, 1.5-4.5 kg of silicon oxide and 1.5-4.5 kg of boric acid.

Further, the particle size distribution of the raw materials after ball milling is controlled to be D0.10: 0.485 μm, D0.50: 0.949 μm, D0.90: 1.971 μm, wherein "D0.10: 0.485 μm "indicates that the cumulative percentage of the particle size distribution of the starting material to 10% corresponds to a particle size of 0.485. mu.m,

"D0.50: 0.949 μm "indicates that the cumulative percentage of particle size distribution of the starting materials to 50% corresponds to a particle size of 0.949. mu.m,

"D0.90: 0.98 μm "indicates that the cumulative percent particle size distribution of the starting material to 90% corresponds to a particle size of 1.971 μm.

Further, when the average particle size of the raw materials is 3-8 micrometers, the ball milling time is 9-15 hours.

Further, in the ball milling process, the material: ball: the water ratio (weight ratio) is as follows: 1.2-1.6: 6-8: 1.2 to 2.0.

Further, a Nantong combined strong 150-ton hydraulic press is adopted for pressing, and green pressing pressure is controlled as follows: 350 to 550kgf/cm²。

Further, the pressing is carried out by adopting a mould, and the single-cavity grouting flow rate of the mould is 15-40 mm/s.

Further, the single cavity grouting flow rate of the mold was 28.5 mm/s.

Further, in the pressing process, the grouting pressure of the die is 6-12 MPa.

Further, the grouting time of the mould is 7-15 s.

Further, 48m roller kilns of Hubei China kiln are adopted for sintering, and the sintering temperature is 1200 +/-10 ℃.

Further, a multi-station grinding machine of Nanjing Sharita is adopted for grinding.

Furthermore, in the grinding process, the mesh number of the adopted grinding wheel is 150-400 meshes.

Further, the number of grinding wheels is preferably 180 in view of the production cost.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) in the process method, the ball milling time is controlled to achieve the particle size distribution after ball milling of D0.10: 0.4 to 0.6 μm, D0.50: 0.8 to 1.0 μm, D0.90: 1.9-2.0 μm, because the fracture resistance of the inorganic non-metallic material mainly comprising crystals is originated from the crack growth of surface defects, and the crack growth has two conditions: transgranular fracture and epitaxial fracture. The larger the crystal grain is, the larger the probability of the internal lattice defect is, and the more easy the transgranular fracture occurs; meanwhile, the larger the crystal grain is, the shorter the crystal grain fracture path is; wherein the content of the first and second substances,

transgranular fracture: the permanent magnetic ferrite sintering process goes through several main stages of drainage, degumming, fluxing additive liquefaction, microparticle migration, recrystallization and cooling solidification, and in the microparticle migration-recrystallization stage, microparticles rapidly migrate in a molten cosolvent and are recombined into larger crystals, so that the higher the proportion of the microparticles is, the larger the size of the finally formed crystal grains is; the concrete explanation is as follows: the slurry has an oriented magnetic field in the injection pressing process, the aim is to make the particles form an oriented arrangement, in the post-sintering process, as a cosolvent is added, the cosolvent is firstly liquefied, the specific surface area of relatively small grains (below 0.5 mu m) is large, the relatively small grains firstly migrate and melt, and then are attached to the larger grains for recrystallization, the recrystallized grains are relatively large and have a plurality of defects, once the slurry has the defect grains with the larger grains, the slurry is easy to have crystal-crossing fracture in the microscopic process in the preparation of the magnetic tile or the secondary processing process of the magnetic tile, and the macro expression is as follows: in the process of external stress, the surface has more crystal through fractures, the probability of crack growth is higher, and finally the magnetic shoe product is fractured;

crystal extension and fracture: when the size of the crystal grains is larger, the channel between the grain boundaries is easy to grow because the path between the large crystal grains is short and simple, the path between the small particles is long and twisted, the longer the path between the crystal grains is, the longer the time for the growth of the microcracks is, namely the microcracks are difficult to grow, the probability of the expansion of the surface cracks can be further reduced, and the breaking strength is mainly expressed in the growth speed and the growth probability of the crystal grain defects or the microcracks; the ferrite material is different from the alumina ceramic material, the alumina ceramic material is ground to be finer, the crystal grains of the alumina ceramic material are smaller, and the ferrite material is ground to be finer, the grain grains of the alumina ceramic material are larger, so that the ball milling time of the ferrite material is shorter, the overall average particle of the raw material is increased, the crystal grains are smaller, and the growth speed and the growth probability of the crystal grain defects or microcracks are smaller; therefore, the invention controls the particle size distribution of slurry, reduces the proportion of micro-size particles, improves the uniformity of particle size, reduces the abnormal growth probability of crystal grains in the sintering process, reduces the probability of lattice defects on the one hand, reduces the size of the crystal grains on the other hand, avoids crystal breakage when bearing bending load finally, greatly lengthens the crack path of crystal breakage and improves the fracture resistance limit; therefore, the temperature of the molten metal is controlled,

(2) according to the invention, the density consistency in the injection process is increased by controlling the grouting flow rate, so that the shrinkage rates of all points of the blank body tend to be consistent in the sintering process, the surface tension force is reduced, and the expansion of microcracks caused by the surface tension force is avoided; the mechanism is as follows: the permanent magnetic ferrite pressing process is subjected to two main stages of grouting and compression, wherein the grouting is a process of replacing air with a solid-liquid mixture, if the air cannot be completely discharged, the green body in the compression stage has inconsistent density, so that the shrinkage in the sintering process is inconsistent, the part with small surface shrinkage and large internal shrinkage is mainly expressed as surface compressive stress, and the part with large surface shrinkage and small internal shrinkage is mainly expressed as surface tensile stress; another major factor affecting the fracture resistance of the material is surface stress, which to some extent prevents the further growth of micro-defect cracks when there is a large compressive stress on the surface of the material; when the surface has tensile stress, the tensile stress can accelerate the growth of micro-defect cracks; in the actual pressing process, the shape of the cavity space of the die is similar to that of the product, namely the shape of the cavity space is a curved arc, but a feeding port is single-cavity injection, namely the cavity space is expanded downwards from the middle to two sides, if the injection time is not enough, two sides are relatively less, even air exists, the air exhaust and drainage of the die are arranged on an upper die, if the air exhaust and drainage are not enough, the inconsistency of slurry at two ends of the cavity space cannot be completely eliminated, the density can be different, and because the slurry has a magnetic field, the magnetic field has a tip concentration effect, the surface shrinkage of the magnetic tile is larger, but the inside shrinkage is smaller, and the surface tensile stress accelerates the growth of micro-defect cracks;

(3) the invention improves the mesh number of the fine grinding wheel through a large-amplitude grinding process, reduces the microcrack defect caused by large-grain carborundum of the grinding wheel, and simultaneously repairs the defect caused by oxidation and coarse grinding on the surface of the sintered green body; the mechanism is as follows: if the product has no defects completely, the defects are difficult to generate, but the defects can be intensively extended from the position with larger defects, and during the grinding process, the larger the mesh number of the grinding wheel is, the smaller the diamond particles are, the smaller the probability of damage is, and as the ferrite is a brittle material, the brittle material is damaged, and the deeper the cracks caused by the brittle material are; based on the above, due to the characteristics of the surface mechanical property of the permanent magnetic ferrite, a diamond grinding wheel with higher hardness must be used in the grinding process, and the grinding microscopic mechanism of diamond particles on the surface of the permanent magnetic ferrite is mainly brittle fracture and rarely ductile cutting, so that the defect of microcracks is inevitably generated;

(4) under the combined action of the three modes, the bending resistance limit of the permanent magnetic ferrite magnetic shoe device is improved while the magnetic property of the ferrite is not damaged.

Drawings

FIG. 1 is a schematic illustration of a slurry particle size distribution.

Detailed Description

The invention is further described with reference to specific examples.

The invention improves the fracture resistance limit of the permanent magnetic ferrite device from macro and micro level by three modes aiming at the stages of slurry (powder) ball milling, pressing and grinding respectively.

Example 1

Controlling slurry particle size

The formula of the raw materials adopted for preparing the permanent magnetic ferrite magnetic shoe device in the embodiment is as follows: 600-800 kg of permanent magnet strontium ferrite pre-sintering material powder, 500-700 kg of waste magnetic steel powder, 100-300 kg of grinding material powder, 12-16 kg of calcium carbonate, 1.5-4.5 kg of silicon oxide and 1.5-4.5 kg of boric acid, wherein the average particle size of the raw materials is 3-8 microns.

The permanent magnetic ferrite magnetic shoe device of the embodiment is prepared by mixing the raw materials uniformly and then sequentially carrying out ball milling, pressing, sintering and grinding. In this example, the particle size distribution after ball milling is achieved by only improving the ball milling time to satisfy D0.10: 0.4 to 0.6 μm, D0.50: 0.8 to 1.0 μm, D0.90: 1.9 to 2.0 μm.

Specifically, a process method for improving the fracture resistance limit of a permanent magnetic ferrite magnetic shoe device comprises the following steps:

(1) ball milling: the required slurry particle size is achieved by controlling the ball milling time, wherein the ball milling process is as follows:

the control method comprises the following steps: time of ball milling

The detection method comprises the following steps: WLP-206 average particle size tester, Malvern laser particle size tester, electronic universal tester (same below)

Test products: 775 magnetic shoe of tool motor (same below)

The ball milling time range is as follows: (comparative example 1) 16-18h before modification, (example) 9-15h after modification, see table 1.

(2) Pressing: and (2) injecting the slurry subjected to ball milling in the step (1) into a mould, controlling the grouting pressure to be 2MPa and the grouting time to be 3.1s, controlling the grouting flow rate of the single green compact to be 72.7mm/s, and performing compression molding to obtain a tile-shaped green compact.

(3) And (3) sintering: and (3) sintering and sintering the pressed blank obtained in the step (2) in a roller kiln at the sintering temperature of 1200 +/-10 ℃ for 70-120 min, and cooling the pressed blank to room temperature along with the kiln to obtain a sintered blank.

(4) Grinding: and (4) carrying out surface polishing and grinding on the surface of the sintered blank obtained in the step (3) to obtain the permanent magnetic ferrite magnetic shoe device, wherein the adopted grinding wheel is 120 meshes.

As shown in Table 1, 25 magnetic shoe products of comparative example 1, examples 1-1 and examples 1-2 were each tested for breaking strength.

TABLE 1 fracture resistance limit of finished magnetic shoe of comparative example 1, examples 1-1 and examples 1-2 after ball milling time control

As can be calculated from Table 1, the breaking strength of the finished product of example 1-1 is improved by 32.46% compared with that of comparative example 1, the breaking strength of the finished product of example 1-2 is improved by 38.39% compared with that of comparative example 1, and the breaking strength of the finished product of example 1-3 is improved by 16.33% compared with that of comparative example 1; it should be noted that the average particle size in table 1 is measured by the WLP-206 average particle size tester, and the index thereof reflects the equivalent average value of the particle size, and in the process of implementation, the average particle size has only a very small variation, and the particle size distribution has changed significantly, which means that the parameter of the average particle size cannot completely reflect the particle condition, nor can be used as the only key parameter for measuring the particle size control, and the analysis in conjunction with fig. 1 shows that the particle size distribution rule can be changed by controlling the ball milling time, so that the distribution center shifts to a large size, and finally approaches to a positive distribution, and the folding resistance limit of the finished product is significantly improved.

Example 2

Improving green density uniformity

The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device is basically the same as that of the embodiment 1-1, and is different in that: in the pressing process, the single-cavity grouting flow rate, the grouting pressure and the grouting time are improved, so that the consistency of the green body density is improved.

Specifically, the pressing control process is as follows:

the control method comprises the following steps: grouting pressure, grouting time and grouting flow rate

Grouting pressure range: 2-4MPa before modification (comparative example 2) and 6-12MPa after modification (example)

Grouting time range: 1-4s before modification (comparative example 2) and 7-15s after modification (example)

Single-cavity grouting flow velocity range: 50-80mm/s before modification (comparative example 2) and 15-40mm/s after modification (example)

As shown in Table 2, 25 magnetic shoe products of comparative example 2, example 2-1, example 2-2 and example 2-3 were each tested for their bending resistance limit.

TABLE 2 fracture resistance Limit of finished magnetic tiles in comparative example 2, example 2-1, example 2-2, and example 2-3

As can be seen from Table 2, the breaking strength of the finished product of example 2-1 was improved by 22.08% as compared with comparative example 2, the breaking strength of the finished product of example 2-2 was improved by 18.32% as compared with comparative example 1, and the breaking strength of the finished product of example 2-3 was improved by 26.34% as compared with comparative example 2.

Example 3

Surface polishing

The process method for improving the fracture resistance limit of the permanent magnetic ferrite magnetic shoe device is basically the same as that of the embodiment 2-1, and is different in that: this embodiment increases the mesh size of the grinding wheel during grinding.

Specifically, the grinding wheel of the present embodiment is as follows:

the control method comprises the following steps: number of meshes of fine grinding wheel

The mesh range of the grinding wheel is as follows: 80-120 meshes before improvement (comparative example 3), and 150-400 meshes after improvement (the embodiment)

As shown in Table 3, 25 magnetic shoe products of comparative example 3, example 3-1, example 3-2 and example 3-3 were each tested for their bending resistance limit.

TABLE 3 fracture resistance Limit of finished magnetic tiles in comparative example 3, example 3-1, example 3-2, and example 3-3

As can be seen from Table 3, the breaking strength of the finished product of example 3-1 was improved by 16.87% as compared with comparative example 3, the breaking strength of the finished product of example 3-2 was improved by 10.76% as compared with comparative example 3, and the breaking strength of the finished product of example 3-3 was improved by 22.80% as compared with comparative example 3.

Under the combined action of the three improvements of the embodiments 1 to 3, the cumulative fracture resistance of the embodiment 3-1 is improved by about 85.81% compared with that of the comparative example 1, and the improvement effect is obvious.

The present invention is not limited to the embodiment of the present invention, and the structure and the implementation of the present invention are described by applying specific examples, and the above description of the embodiment is only used to help understand the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.