CN110323051B

CN110323051B - Soft magnetic metal powder passivation method without toxicity and pollutant discharge

Info

Publication number: CN110323051B
Application number: CN201810264991.2A
Authority: CN
Inventors: 郭峰; 黄裕茂; 汪贤
Original assignee: Kunshan Citong New Material Technology Co ltd
Current assignee: Kunshan Citong New Material Technology Co ltd
Priority date: 2018-03-28
Filing date: 2018-03-28
Publication date: 2021-04-16
Anticipated expiration: 2038-03-28
Also published as: CN110323051A

Abstract

The invention provides a method for passivating metal soft magnetic powder without toxicity and pollutant emission. Wherein the surface of the metal soft magnetic powder with the oxide layer is prepared by an atomization method or a mechanical ball milling method, and the oxygen content on the surface is between 500-5000 ppm; in addition, the passivator adopts natural hard water, is pollution-free and non-toxic, has no pollutants and toxic and harmful substances from input to output, really realizes green and environment-friendly production, and has the hardness of the hard water between 3.5 and 12 GPG; the passivation process is divided into two steps of drying and heat treatment, the drying process enables redundant water to be removed and forms a passivation layer on the surface of the powder, the passivation layer is tightly combined with the original oxide layer and can fill recesses on the surface of the original powder, and the heat treatment enables redundant crystal water on the surface of the passivated powder to be partially removed so as to prevent the moisture absorption phenomenon in the powder storage process. The passivation powder prepared by the method has effectively improved insulating property and corrosion resistance and does not reduce magnetic property.

Description

Soft magnetic metal powder passivation method without toxicity and pollutant discharge

Technical Field

The invention relates to the field of magnetic materials, in particular to a method for passivating soft magnetic metal powder without toxicity and pollutant emission.

Background

With the development of modern integrated circuits, chips, various electronic component technologies, wireless internet and application thereof, the informatization has become the mainstream trend of the fourth industrial revolution at present; various dc loads are widely applied to various electronic devices, such as smart phones, automotive electronics, smart televisions, tablet computers, notebook computers, LED televisions, various communication terminals and servers, smart appliances, and the like, due to their high energy conversion efficiency, small size, high stability, and the like.

The advent of various intelligent devices has driven the technological progress of related electronic components. Among them, magnetic components are widely used as buck-boost, filter inductors, and power factor correction inductors of various intelligent electronic devices, such as metal magnetic powder cores, molded inductors, multilayer inductors, and electronic transformers.

The metal magnetic powder core is a soft magnetic material with the characteristic of distributed air gaps, and the material consists of soft magnetic metal powder, a powder surface insulating agent and a binder; the particles are insulated from each other by the surface insulating agent, the powder is kept with certain strength by the adhesive, and the air gaps between the particles become the main energy storage positions. The magnetic powder core comprises an iron powder core, an iron silicon aluminum powder core, a permalloy powder core, an amorphous magnetic powder core and the like, and the manufacturing method of the magnetic powder core comprises the working procedures of powder surface passivation treatment, passivation powder coating and granulation, powder press forming, powder core annealing, powder core surface spraying and the like, wherein the surface passivation treatment is generally phosphorization treatment, and the problem is caused by the adoption of dangerous chemicals and the emission of toxic and harmful substances.

The manufacturing method of the die-pressing inductor is to place the excited copper coil in the magnetic iron-based metal powder and form the excited copper coil and the magnetic iron-based metal powder on a forming machine at the same time, so that the complicated winding process is omitted, good EMI (electromagnetic interference) characteristics are obtained, and meanwhile, the automatic mounting on an integrated circuit is facilitated. In summary, the molded inductor is a modern electronic component with short flow, high performance and high automation degree, and is an indispensable important electronic component of modern direct current load equipment (especially intelligent electronic equipment). Typically, the material of the molded inductor is composed of metallic soft magnetic powder and copper coils. The metal soft magnetic powder is generally an iron-based metal powder including carbonyl iron powder, FeCrSi alloy powder, FeSi alloy powder, atomized iron powder, etc., which has superior soft magnetic characteristics. But the corrosion or thermal aging phenomenon inevitably occurs in the long-term use process, especially in the fields of automobile electronics, servers and the like; therefore, chromium is usually added into the composition in the industry to improve the corrosion resistance; however, the addition of chromium inevitably lowers the saturation induction and permeability of the alloy, and for this reason, the amount of chromium added is generally limited by this condition, and in order to solve this problem, it can be improved by two methods: (1) and covering a layer of anti-corrosion coating on the outer part of the product. The trouble caused by the method is that the process becomes complicated, the coating thickness is thick, the cost is increased, and the environment is polluted; (2) the powder surface is treated, for example chemically, to form a strong passivation layer.

In recent years, with the environmental pollution caused by the development of the power electronic industry, all countries around the world standardize the industry development in a legislative form, such as the requirement on the content of halogen elements, the requirement on the content of heavy metals, the requirement on the recycling of electronic products, and the like, so that the requirement on environmental protection of various electronic components becomes a precondition for the industry development; in addition, with social progress, countries and common people pay more and more attention to production safety, and the trend of improving labor environment and reducing industrial accidents also becomes the future industrial development trend. The above problems can be combined to conclude that: the development of nontoxic and harmless production and pollutant-free emission production is a new trend of industrial development in China and the world.

In summary, the passivation of the metal powder surface of the magnetic powder core or the molded inductor is free from the addition of toxic and harmful substances or the generation of pollutant emissions. Therefore, there is a need for a method of passivating a metallic soft magnetic powder that overcomes the above-mentioned problems.

Disclosure of Invention

The invention aims to provide a method for passivating soft magnetic metal powder without toxicity and pollutant emission, so that toxic and harmful substances are not added in the production process, pollutant emission is not generated, and the whole passivation production process cannot cause harm to people and nature. The principle is as follows:

1. hard water which is a natural raw material and does not need to be reprocessed is used as a passivating agent;

2. oxidation-reduction reaction does not occur in the passivation process;

3. only purified water is discharged as an effluent after the passivation is finished.

The invention provides a metal soft magnetic powder passivation method without toxicity and pollutant emission, which comprises the following specific implementation steps:

firstly, weighing a certain amount of hard water and metal soft magnetic powder, and then mixing and stirring. The metal soft magnetic powder is generally prepared by an atomization method or a mechanical ball milling method, the surface of the metal soft magnetic powder is required to be provided with a layer of oxide film, the film is generally formed by an inevitable oxidation process in the powder preparation process, the bonding force between the film and the surface of the metal powder is chemical bonding, the oxygen content on the surface of the powder is generally between 500 and 5000ppm, and the oxide can be a composite oxide composed of ferric oxide, silicon oxide, chromium oxide, aluminum oxide, molybdenum oxide and the like according to alloy components. The mixing ratio of the hard water to the soft magnetic metal powder is 1:100-100:100, and the specific requirement is determined according to the subsequent drying method, and the stirring device can be a common stirrer or an emulsifying machine; hardness > =3.5GPG, the harder the hardness, the thicker the passivation film, the better the insulation, but generally not more than 12, otherwise, too much permanent hardness component in hard water will form loose porous film, which causes the magnetic performance to decrease.

Secondly, feeding the mixed material of hard water and the metal soft magnetic powder into a heating device and completely drying the water. The heating device can be a drying box, can also be a heating barrel with stirring, can also be an atomization drying tower, a flash evaporation dryer and the like which can instantly dry water, the drying temperature of any drying method is 80-200 ℃, the temperature refers to the self temperature of the soft magnetic metal powder during drying, but not to a set temperature, the drying efficiency is low due to too low temperature, the energy consumption is increased due to too high drying temperature, and a passivation film is easy to crack. The first and second steps can be repeated for 2-3 times as required, and the insulation property of the soft magnetic metal powder is higher as the times are more.

Thirdly, the dried powder is subjected to heat treatment, and the heat treatment temperature is between 100 ℃ and 300 ℃. Since the dried metal powder may absorb moisture, the dried powder is subjected to heat treatment as needed, and the purpose of the heat treatment is to reduce or completely remove crystal water in the molecular structure of the passivation film material, thereby reducing the moisture absorption rate in the atmosphere, wherein the crystal water is less at higher temperatures, but is less likely to exceed the melting point of the passivation film material. The heat treatment apparatus may be a drying oven, or a heat treatment apparatus such as a muffle furnace or a tunnel furnace.

From the preparation process, no toxic and harmful substance is added in the process, and no pollutant is discharged after the passivation film is formed.

The following detailed description of the embodiments of the present invention is provided in connection with the accompanying drawings for the purpose of facilitating understanding and understanding of the technical solutions of the present invention.

Drawings

FIG. 1 is a flow chart of examples 1 to 3 of the present invention.

Detailed Description

Example 1

In this example, FeSi was prepared by atomizing 10kg of water to obtain a soft metal powder_4.5200 meshes of powder, wherein the hardness of hard water is 6, the surface oxygen content of the initial powder is 3550ppm, the weight ratio of the hard water to the powder is 6:100, the mixture is dehydrated and dried in a heating barrel of a stirring machine, the drying temperature is 80 ℃, the drying time is 60 minutes, and the powder is free of agglomeration after being dried; then, putting the dried powder into a muffle furnace, putting the powder into a stainless steel tray, and keeping the temperature for 60 minutes at the heat treatment temperature of 200 ℃, wherein the powder after heat treatment has no agglomeration and color change; the oxygen content is directly tested by adopting powder, and the testing equipment is an oxygen-nitrogen analyzer; the insulation resistance was obtained by compressing the powder to a density of 4.5g/cm³The test is carried out after the circular ring, and the test equipment is an insulation impedance instrument; the hardness of the discharged water is tested by adopting water condensed in a pipeline in the drying process; the test results were as follows:

example 2

In this example, FeSi was prepared by atomizing 10kg of water to obtain a soft metal powder_4.5Powder of 200 meshes, wherein the hardness of hard water is 10, the surface oxygen content of the initial powder is 3550ppm, the weight ratio of the hard water to the powder is 6:100, the mixture is dehydrated and dried in a heating barrel of a stirrer, the drying temperature is 80 ℃, the drying time is 60 minutes, and the powder is free of agglomeration after being dried; then, putting the dried powder into a muffle furnace, putting the powder into a stainless steel tray, and keeping the temperature for 60 minutes at the heat treatment temperature of 200 ℃, wherein the powder after heat treatment has no agglomeration and color change; the oxygen content is directly tested by adopting powder, and the testing equipment is an oxygen-nitrogen analyzer; the insulation resistance was obtained by compressing the powder to a density of 4.5g/cm³The test is carried out after the circular ring, and the test equipment is an insulation impedance instrument; hardness of discharged waterTesting the water condensed in the pipeline in the drying process; the test results were as follows:

example 3

FeCr prepared by atomizing the metallic Soft magnetic powder of this example with 10kg of water_4.5Si_3.5400-mesh powder, wherein the hardness of hard water is 6, the surface oxygen content of the initial powder is 2200ppm, the weight ratio of the hard water to the powder is 6:100, the mixture is dehydrated and dried in a heating barrel of a stirrer, the drying temperature is 80 ℃, the drying time is 60 minutes, and the powder is free of agglomeration after being dried; then, putting the dried powder into a muffle furnace, placing the powder in a stainless steel tray, and carrying out heat treatment at 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃ and 350 ℃ for 60 minutes, wherein the powder after heat treatment is free from caking, the powder after 350 ℃ treatment is slightly yellow, and the powder after other temperature treatment is free from color change; testing the powder, and directly testing the oxygen content by adopting the powder; the test equipment was an oxygen-nitrogen analyzer and the dielectric impedance was measured by compressing the powder to a density of 4.5g/cm³Testing the circular ring; the testing equipment is an insulation impedance instrument, and the hardness of the discharged water is tested by adopting water condensed in a pipeline in a drying process; the test results were as follows:

Claims

1. a passivation method of soft magnetic metal powder without toxicity and pollutant emission is characterized in that: mixing soft magnetic metal powder with an oxide layer on the surface with hard water, drying and passivating at the temperature of 80-200 ℃, wherein the temperature is the self temperature of the soft magnetic metal powder when drying but not the set temperature, and then carrying out heat treatment on the soft magnetic metal powder at the temperature of 100-500 ℃; the oxide layer is generated in the production process of the oxide layer due to an inevitable oxidation process, and the surface oxygen content of the soft magnetic metal powder is 500-5000 ppm; the hard water is natural hard water, the hardness is 3.5-12GPG, and the weight ratio of the hard water to the soft magnetic metal powder is 1:100-100: 100; only pure water is discharged during passivation, the hardness of the discharge is less than 0.2GPG, no toxic and harmful substance is added during the passivation process, no toxic and harmful substance is discharged, and no oxidation-reduction reaction occurs during the passivation process.

2. A non-toxic non-pollutant discharge soft magnetic metal powder passivation method according to claim 1, characterized in that: the soft magnetic metal powder is prepared by an atomization method or a mechanical ball milling method, wherein the atomization method is water atomization and gas atomization, and the particle size of the powder is 1-100 um.

3. A non-toxic non-pollutant discharge soft magnetic metal powder passivation method according to claim 1, characterized in that: the heat treatment temperature is 100-300 ℃, the drying temperature is lower than the heat treatment temperature, and the temperature difference is more than or equal to 20 ℃.