An additive for a metal soft magnetic powder core and a method of preparation

Abstract

The application relates to an additive for a metal soft magnetic powder core and a preparation method, and belongs to the technical field of preparation of magnetic materials. The additive is made of hydrated calcium silicate, nano attapulgite, nano mica sheet and volatile lubricating oil, wherein the hydrated calcium silicate adsorbs more than 2.0 mL / g of volatile lubricating oil; the volatile lubricating oil does not affect the fluidity of the additive itself and metal powder, is pressed out from the hydrated calcium silicate after being pressed, and plays a lubricating role; in the subsequent annealing process, the volatile lubricating oil is completely volatilized below 300 DEG C, and there is no carbon residue in the metal soft magnetic powder core. The heat-resistant temperature of the additive prepared by the application is more than 800 DEG C, and there is no agglomeration phenomenon. The additive has good bonding performance, the prepared magnetic powder core has excellent magnetic and mechanical properties, and sufficient lubrication can be provided when the powder core is pressed into a shape, so that the yield of products is ensured and the die damage of a mold is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation of magnetic materials, and particularly relates to an additive for metal soft magnetic powder core. BACKGROUND

[0002] Iron-silicon and iron-silicon-aluminum metal soft magnetic powder cores are widely used in electronic devices due to their excellent magnetic properties and low loss. However, traditional insulation formulations and processes often cannot provide ideal insulation performance, which increases the loss of metal soft magnetic powder cores, and also has the disadvantage of low mechanical strength. During the pressing process, more lubricants and release agents such as zinc stearate and calcium stearate are used. Such lubricants will volatilize during the subsequent stress relief annealing process, adhere to the exhaust duct when cold, and drop on the product, which will affect the appearance of the product, and adhere to the dust removal bag when cold, which will block the bag. SUMMARY

[0003] In order to solve the lubrication and demolding problems in the pressing process of metal soft magnetic powder core, and improve the insulation and strength of metal soft magnetic powder core, the present application provides an additive for metal soft magnetic powder core, and simultaneously provides a preparation method of the additive for metal soft magnetic powder core.

[0004] An additive for metal soft magnetic powder core is prepared from calcium silicate hydrate with a mass percentage of 48-70%, nano attapulgite with a mass percentage of 20-40%, and nano mica sheet with a mass percentage of 5-15wt%; wherein the calcium silicate hydrate adsorbs volatile lubricating oil of more than 2.0mL / g;

[0005] The average particle size of the nano attapulgite and nano mica sheet is less than 1 micron;

[0006] The additive is in powder form, and the heat resistance temperature of the additive is more than 800℃, without agglomeration phenomenon.

[0007] When used for preparing metal soft magnetic powder core, the additive is used in an amount of 0.5-2.5% of the mass of the metal soft magnetic powder after passivation treatment.

[0008] The preparation operation steps of the additive for metal soft magnetic powder core are as follows:

[0009] (1) The calcium silicate hydrate, attapulgite and nano mica sheet are dried respectively to obtain dried calcium silicate hydrate, dried nano attapulgite and dried nano mica sheet;

[0010] (2) The dried calcium silicate hydrate is immersed in volatile lubricating oil, stirred with a stirring paddle, and then left to stand. After stirring again, it is left to stand again, and each standing time is half of each stirring time. This cycle is repeated for 2-5 times. When the oil absorption of the calcium silicate hydrate is greater than 2.0mL / g, the oil is controlled, and the oil-immersed calcium silicate hydrate is obtained.

[0011] (3) In a spiral agitator, 48-70wt% of the oil-immersed calcium silicate hydrate, 20-40wt% of the dried nanometer attapulgite and 5-15wt% of the dried nanometer mica flake are mixed uniformly at room temperature to obtain a powder additive for the metal soft magnetic powder core.

[0012] Further technical solutions are as follows:

[0013] In step (1), the drying temperature is 100-110℃, and the drying time is 30-40min.

[0014] In step (1), the drying degree is that the mass loss of the sample before and after drying is less than 0.3% by sampling every 20min.

[0015] In step (2), the stirring paddle is stirred for 20min, and then the sample is left for 10min, and then stirred for 20min, and then left for 10min, and the cycle is repeated for 2-5 times.

[0016] The beneficial technical effects of the present application are embodied in the following aspects:

[0017] 1. The additive of the present application is an inorganic additive, which utilizes the structural and performance advantages of the three inorganic substances, i.e., the calcium silicate hydrate, the nanometer attapulgite and the nanometer mica flake, to improve the strength, insulation and lubricity of the metal soft magnetic powder core. The calcium silicate hydrate is a new type of functional powder material, which has the characteristics of rich porous structure, high porosity, large specific surface area, high oil absorption rate (oil absorption capacity is more than 2.0mL / g) and no magnetic impurities. The attapulgite is a natural, long-chain structure, water-containing magnesium-aluminum silicate clay mineral, which has strong adhesion and high temperature stability, and can improve the strength of the metal soft magnetic powder core. The nanometer mica flake is a silicate mineral with a layered structure, which has high mechanical strength and rigidity, good high-temperature resistance and insulation performance. The three inorganic substances are used to prepare the metal soft magnetic powder core, and the strength of the metal soft magnetic powder core is mainly provided by the fibrous nanometer attapulgite, the insulation is mainly provided by the mica and the calcium silicate hydrate, and the lubricity is mainly provided by the volatile lubricating oil adsorbed in the calcium silicate hydrate.

[0018] 2. The heat-resistant temperature of the additive of the present application is more than 800℃, which significantly improves the strength of the metal soft magnetic powder core, and the prepared metal soft magnetic powder core has excellent comprehensive magnetic and mechanical properties, the product strength is increased by at least 20% or more, the magnetic permeability μ and the quality factor Q value are increased by at least 2.5% or more in each frequency band, and no die drawing phenomenon occurs during the development process, and the lubricity is good.

[0019] 3. The additive has excellent oil immersion capacity, the volatile lubricating oil is contained in the hydrated calcium silicate, which does not affect the flowability of the additive itself and the metal powder, after being pressed, the hydrated calcium silicate inside is pressed out to play a lubricating role; in the subsequent annealing process, it can be completely volatilized below 300°C, and there will be no carbon residue (affecting permeability) in the metal soft magnetic powder core, and it will not affect the product yield and dust removal system like the existing zinc stearate lubricant. DETAILED DESCRIPTION

[0020] The application will be further described below in combination with examples.

[0021] All raw materials in the following examples are commercially available.

[0022] Example 1

[0023] The preparation operation steps of the additive for metal soft magnetic powder core are as follows:

[0024] (1) First, 5Kg hydrated calcium silicate, 4Kg nano attapulgite and 1Kg nano mica flake are dried in an oven, the drying temperature is 110°C, and the drying time is 40min; the dried hydrated calcium silicate, the dried nano attapulgite and the dried nano mica flake are obtained. The degree of drying: take samples every 20min, the mass loss of the sample before and after drying is less than 0.3%.

[0025] The average particle size of the nano attapulgite and the nano mica flake is less than 1 micron.

[0026] (2) The dried hydrated calcium silicate is put into the volatile lubricating oil, which is aluminum foil stamping oil (AF-3R), stirred with a stirring paddle for 20min, and then left for 10min, and then stirred again for 20min, and then left for 10min, and so on for 4 times. When the oil absorption of the hydrated calcium silicate exceeds 2.0mL / g, the oil is controlled and the oil-impregnated hydrated calcium silicate is obtained.

[0027] (4) In a spiral stirrer, the oil-impregnated hydrated calcium silicate, the dried nano attapulgite and the dried nano mica flake are stirred and mixed uniformly at room temperature to obtain a powder-shaped additive for metal soft magnetic powder core. The heat-resistant temperature of the additive prepared in this example 1 is more than 800°C, and there is no agglomeration phenomenon.

[0028] The additive prepared in example 1 is mixed with iron-silicon-aluminum (FeSiAl) powder which has been pretreated by passivation, the amount of the additive is 0.5% of the mass of the passivated iron-silicon-aluminum (FeSiAl) powder, and then it is pressed into a shape, and then it is annealed in a nitrogen atmosphere to remove stress and cooled to obtain a metal soft magnetic powder core.

[0029] Three parallel samples of the final iron-silicon-aluminum magnetic powder core of Example 1 were tested, and the performance is shown in Table 1. At the same time, a comparative test was conducted on a soft magnetic powder of the same type, and the performance of Comparative Example 1 is also shown in Table 1.

[0030] Comparative Example 1 was added with 0.3% of nano-silicon dioxide and 0.2% of zinc stearate by mass of the iron-silicon-aluminum (FeSiAl) powder.

[0031] Table 1: Performance comparison of the present Example 1 and Comparative Example 1 (FeSiAl)

[0032]

[0033] In Table 1, μ refers to the permeability of the soft magnetic powder core, and Q refers to the quality factor of the soft magnetic powder core, and the same applies hereinafter.

[0034] Example 2

[0035] The preparation operation steps of the additive for metal soft magnetic powder core are as follows:

[0036] (1) First, 8 Kg of hydrated calcium silicate, 5 Kg of nano attapulgite, and 2 Kg of nano mica sheet were dried in an oven, with a drying temperature of 100°C and a drying time of 50 min. The dried hydrated calcium silicate, dried nano attapulgite, and dried nano mica sheet were obtained. The degree of drying: sample was taken every 20 min, and the mass loss of the sample before and after drying was less than 0.3%.

[0037] The average particle size of the nano attapulgite and the nano mica sheet was less than 1 micron.

[0038] (2) The dried hydrated calcium silicate was put into the volatile lubricating oil, which was copper pipe bending oil with a brand of AF-2R. The hydrated calcium silicate was stirred for 20 min with a stirring paddle, and then was left to stand for 10 min. The above steps were repeated twice. When the oil absorption of the hydrated calcium silicate exceeded 2.5 mL / g, the oil was controlled, and the oil-impregnated hydrated calcium silicate was obtained.

[0039] (3) The oil-impregnated hydrated calcium silicate, the dried nano attapulgite, and the dried nano mica sheet were mixed uniformly at room temperature in a spiral stirrer to obtain a powder-shaped additive for metal soft magnetic powder core. The heat-resistant temperature of the additive prepared in this Example 2 was more than 800°C, and there was no agglomeration phenomenon.

[0040] The additive prepared in this Example 2 was mixed with the iron-silicon (FeSi) powder which had been subjected to passivation pretreatment, and the amount of the additive was 1.5% by mass of the passivation pretreated iron-silicon (FeSi) powder. The mixture was pressed into a shape, and then was subjected to stress relief annealing treatment in a nitrogen atmosphere, and was cooled to obtain a metal soft magnetic powder core.

[0041] Comparative Example 2 adds 1% of nano-silica and 0.5% of zinc stearate by mass of iron-silicon (FeSi) powder.

[0042] Table 2: Performance comparison of inventive example 2 and comparative example 2 (FeSi)

[0043]

[0044] Three samples of the iron-silicon magnetic powder core prepared in Example 2 were tested, and the performance is shown in Table 2. At the same time, comparative tests were conducted on soft magnetic powder of the same type, and the performance of Comparative Example 2 is also listed in Table 2.

[0045] Example 3

[0046] The preparation steps of the additive for metal soft magnetic powder core are as follows:

[0047] (1) First, 7Kg of hydrated calcium silicate, 4Kg of nano attapulgite and 1Kg of nano mica flake were dried in an oven, the drying temperature was 120℃, and the drying time was 50min; the dried hydrated calcium silicate, the dried nano attapulgite and the dried nano mica flake were obtained. The degree of drying: take samples every 20min, the mass loss of the sample before and after drying is less than 0.3%.

[0048] The average particle size of the nano attapulgite and the nano mica flake is less than 1 micron.

[0049] (2) The dried hydrated calcium silicate was put into the volatile lubricating oil, which was the oil for copper pipe expansion head, grade K-2, stirred with a stirring paddle for 20min, stood for 10min, stirred again for 20min, stood for 10min, and the cycle was repeated twice. When the oil absorption of the hydrated calcium silicate exceeded 2.1mL / g, the oil was controlled and the oil-impregnated hydrated calcium silicate was obtained.

[0050] (3) In a spiral stirrer, the above oil-impregnated hydrated calcium silicate, the dried nano attapulgite and the dried nano mica flake were mixed uniformly at room temperature to obtain a powder-shaped additive for metal soft magnetic powder core. The heat-resistant temperature of the additive prepared in this Example 3 exceeds 800℃, and there is no agglomeration phenomenon.

[0051] The additive prepared in this Example 3 was mixed with iron-nickel (FeNi) powder which had been pretreated for passivation, and the amount of the additive was 2.5% by mass of the passivated iron-nickel powder. The mixture was pressed and formed, and then stress relief annealing was carried out in a nitrogen atmosphere, and the metal soft magnetic powder core was obtained after cooling.

[0052] Comparative Example 3 adds 1.5% of nano-silica and 1.0% of zinc stearate by mass of iron-nickel (FeNi) powder.

[0053] Table 3: Performance comparison of inventive examples and comparative examples (FeNi)

[0054]

[0055] Three samples of the Fe-Ni magnetic powder core prepared in this example 3 were tested in triplicate, and the results are shown in Table 3. At the same time, comparative tests were performed on soft magnetic powder test materials of the same type, and the performance of Comparative Example 3 is also shown in Table 3.

Claims

1. An additive for metal soft magnetic powder core, characterized in that: The additive is prepared from 48-70% by weight of hydrated calcium silicate, 20-40% by weight of nano-attapulgite, and 5-15% by weight of nano-mica flakes. The hydrated calcium silicate adsorbs more than 2.0 mL / g of volatile lubricating oil; The average particle size of the nano-attapulgite and nano-mica flakes is less than 1 micron; The additive is in powder form, has a heat-resistant temperature exceeding 800° C., and has no agglomeration phenomenon.

2. The additive for metal soft magnetic powder core according to claim 1, characterized in that: When used for preparing a metal soft magnetic powder core, the additive is used in an amount of 0.5 to 2.5% of the mass of the metal soft magnetic powder after passivation treatment.

3. The method for preparing an additive for a metal soft magnetic powder core according to claim 1, characterized in that: The steps are as follows: (1) drying the hydrated calcium silicate, attapulgite and nano-mica flakes respectively to obtain dried hydrated calcium silicate, dried nano-attapulgite and dried nano-mica flakes; (2) immersing the dried hydrated calcium silicate in volatile lubricating oil, stirring with a stirring paddle, and allowing to stand; stirring again, and allowing to stand again, with each standing time being half of each stirring time, and repeating this cycle 2-5 times. When the oil absorption of the hydrated calcium silicate is greater than 2.0 mL / g, remove the hydrated calcium silicate and control the oil to obtain oil-absorbing hydrated calcium silicate; (3) In a spiral stirrer, 48-70% by weight of oil-absorbing hydrated calcium silicate, 20-40% by weight of dried nano-attapulgite, and 5-15% by weight of dried nano-mica flakes are stirred and mixed uniformly at room temperature to obtain a powdered additive for metal soft magnetic powder cores.

4. The preparation method according to claim 3, wherein: In step (1), the drying temperature is 100-110° C., and the drying time is 30-40 min.

5. The preparation method according to claim 3, wherein: In step (1), the degree of drying is as follows: sampling is performed at intervals of 20 minutes, and the mass loss of the sample before and after drying is less than 0.3%.

6. The preparation method according to claim 3, wherein: In step (2), stir with a stirring paddle for 20 minutes, let it stand for 10 minutes, stir for another 20 minutes, let it stand for another 10 minutes, and repeat this cycle 2-5 times.

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