JPH04219902A - Dust core material and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a dust core material which can be formed to a complicated shape, does not distort even when the material is subjected to press forming, and has an excellent magnetic property by solidifying and forming ferromagnetic powder which can be restored by annealing at a specific temperature after a specific amount of SiO2 is added to the powder as a binder. CONSTITUTION:Ferromagnetic powder, such as high-purity iron powder, 300NH iron powder, or 'permalloy(R)', which can be restored at <=600 deg.C is solidified and formed after SiO2 is added to the powder by <=3.9wt.% as a binder. It is preferable to use ethyl silicate produced by hydrolysis produced by adding water and alcohol as the binder and to perform annealing at <=600 deg.C after the surface of the mixture is dried at <=200 deg.C and the dried mixture is press- formed. While electrolytic iron powder has a low annealing temperature, this kind of iron powder cannot be used for this purpose unless the iron powder is reduction-annealed, since the iron powder contains 0.2-0.3wt.% O2 and the work becomes complicated when the iron powder is used.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a powder magnetic core material and a method for manufacturing the same, and more particularly to a powder magnetic core material with low iron loss used for electromagnetic parts such as noise filters and choke coils, and a method for manufacturing the same. It is something.

0002

2. Description of the Related Art Generally, magnetic core materials produce hysteresis loss and eddy current loss, and the sum of these two results in iron loss.

This hysteresis loss is the energy consumed to cancel residual magnetism, and the lower the coercive force (Hc), the smaller it becomes. Eddy current loss is caused by current induced in an alternating magnetic field, so when electrical resistance is high. That's how small it is.

[0004] Therefore, the magnetic core material needs to have a low core loss, and a laminated structure of thin iron plates treated with an insulating coating is usually used, but it has been difficult to manufacture parts with complex shapes.

On the other hand, powder magnetic cores made by covering soft magnetic powder with epoxy resin and solidifying it can be made into parts with complex shapes by using ordinary powder molding methods, but it is difficult to make parts with complex shapes during powder molding. There is a problem that strain is introduced into the magnetic powder due to pressurization, and the magnetic performance as a magnetic core material deteriorates.

[0006]

[Problems to be Solved by the Invention] In view of the various problems in the production of conventional magnetic core materials explained above, the present inventor has conducted extensive research, and as a result, the present invention has been developed to form a magnetic core material into a complicated shape. We have developed a powder magnetic core material with excellent magnetic performance that can eliminate distortion through press forming, and a method for manufacturing the same.

[0007]

[Means for Solving the Problems] A powder magnetic core material and a method for producing the same according to the present invention include SiO2 as a binder in a ferromagnetic powder that can be recovered by annealing at a temperature of 600°C or lower.
The first invention is a powder magnetic core material characterized by containing 3.9 wt% or less of ferromagnetic powder and solidified and molded, and mixed with ethyl silicate obtained by adding water and alcohol to ferromagnetic powder to cause a hydrolysis reaction. A second method for producing a powder magnetic core material with excellent magnetic performance, which is characterized in that the surface of the mixture is dried at a temperature of 200°C or lower, and after press forming, annealing is performed at a temperature of 600°C or lower. This invention consists of two inventions.

The powder magnetic core material and the method for producing the same according to the present invention will be explained in detail below.

It is desirable that the magnetic powder for the magnetic core material has a small coercive force (Hc) and a large maximum magnetic permeability (μm).
For this reason, it is best to use a material with a low annealing recovery temperature, for example,
Electrolytic iron powder is an iron powder with a low annealing recovery temperature, but since it contains 0.2 to 0.3 wt% of O2, it cannot be used without reduction annealing. The work up to this point is complicated, and the iron powder itself is expensive.

[0010] In addition, water atomized iron powder with high productivity is
Although it is produced in large quantities as iron powder for annealing, it contains more impurities than electrolytic iron powder. However, by strictly selecting raw materials for melting, it is possible to obtain products with performance equivalent to reduction annealed electrolytic iron powder. Therefore, in the powder magnetic core material and the manufacturing method thereof according to the present invention, for example, high-purity iron powder, 300NH iron powder, permalloy, etc. are shown as the ferromagnetic powder, but in addition, nickel, amorphous amorphous for soft magnetism, etc. Excellent effects can also be obtained.

[0011] In addition, as an insulating film material, ethyl silicate, which has heat resistance, is easy to handle, and can be easily mass-produced, is used as a material for forming an inorganic SiO2 film. Use as raw material.

This ethyl silicate is commercially available as ethyl silicate 20, 40, 50 etc. made by concentrating SiO2.
Use one that has been hydrolyzed by adding water.

[0013] The coating treatment of the ferromagnetic powder is carried out by adding an appropriate amount of hydrolyzed ethyl silicate to the ferromagnetic powder, mixing it uniformly, and then fluidizing the powder in a hot air oven at a temperature of 100 to 250°C. Allow the surface to dry.

[0014] The unhydrolyzed ethyl silicate is 20
Although a drying temperature of 0 to 250°C is required, ethyl silicate that has been sufficiently hydrolyzed can be dried at a temperature of 100°C or lower.

[0015] The higher the drying temperature, the worse the compressibility of the ferromagnetic powder becomes, and it may not be possible to compress it at a temperature of 250°C. Therefore, it is better to keep the drying temperature as low as possible. 200 from the explanation of
It is preferable to set the drying temperature to below ℃.

[0016] Furthermore, it is preferable to fluidize the ferromagnetic powder during drying, because fluidizing the powder can prevent agglomeration and also allows the powder to be easily crushed after drying. This dried powder is passed through a #60 sieve to improve moldability.

[0017] Next, molding is performed using a powder press at 4.5 to 9
．． Compression was performed using a surface pressure of 5 tons/cm2. The compact then recovers the magnetic properties of the powder and removes the Si on the surface coating of the powder.
Annealing is performed to promote O2 conversion and to create stronger bonds between powders.

Normal iron powder requires an annealing temperature of 600°C or higher to recover its magnetic properties, but high-purity ferromagnetic powder can recover even at a temperature of 600°C or lower, for example, 500°C.

Therefore, in consideration of thermal deterioration of the surface film (reduction in electrical resistance), it is advantageous to use high-purity iron powder (iron powder). This thermal deterioration is 0.0005 Ω·cm at a temperature of 650°C in the case of ethyl silicate, whereas it is as small as 0.02 to 0.03 Ω·cm at a temperature of 500°C.

[0020] The heating rate for annealing the magnetic powder is, for example, 3°C, because if it is too fast, it may expand or crack.
/min or less.

[0021] The density of the compact after annealing is 2 to 3% higher than that of ordinary atomized iron powder. This is because high-purity ferromagnetic powder is softer, and as a result, The maximum permeable flux density (Bm) of pure iron powder becomes high.

[0022]

[Example] An example of the powder magnetic core material and the manufacturing method thereof according to the present invention will be described.

[0023]

[Example] Table 1 shows the type of powder, the amount used, the SiO2 equivalent amount of ethyl silicate, the drying temperature of the powder, and Table 2 shows the forming surface pressure, annealing temperature, density after annealing, magnetic properties, and specific resistance. be.

[0026]No. 1.No. 2.No. No. 3 is a case where the powder was compacted by changing the drying temperature, and it was possible to release the powder from the mold at a drying temperature of 200°C, but when the drying temperature was 250°C, the shape collapsed.

[0027]No. 3.No. 4.No. 5, No. 6
This is a case where the amount of SiO2 after drying was increased by changing the amount of ethyl silicate, and molding was possible without losing the shape up to the amount of SiO2 up to 3.9 wt%, but when the amount of SiO2 was 5.
At wt%, the shape was lost.

[0028]No. 6, No. 7.No. 8, No. 9
is the case where the annealing temperature after forming is changed; for Hc, an annealing temperature of 250°C is insufficient, and an annealing temperature of 500°C,
It recovered at 550°C. Further, the higher the annealing temperature, the higher μm becomes.

[0029]No. 7.No. No. 10 shows the case where the surface pressure was changed, and the higher the surface pressure, the higher the density of the molded body and the larger Bm.

[0030]No. 6, No. 7.No. 8, No. 9
, No. 10 and no. 11, No. 12, No. 13,
No. 14 is the case where the type of powder was changed, and the Hc of high-purity iron powder recovered at an annealing temperature of 500°C, but normal iron powder (300 μ) requires an annealing temperature of 600°C or higher. I understand. Furthermore, since the compacted density of high-purity iron powder is about 5% higher, Bm is also higher.

On the other hand, looking at the specific resistance of high-purity iron powder and ordinary iron powder, it is 0.01 Ωcm at an annealing temperature of 600°C, which is 1600 times higher than that of ordinary bulk material. When the temperature reaches 650℃, the specific resistance becomes 0.0005Ω・cm
becomes extremely small. Therefore, the maximum annealing temperature is 600℃
That's it.

[0032]No. 15 super alloy is the same as high purity iron powder.

From Tables 1 and 2, it is clear that high-purity iron powder is used, the SiO2 content is 3.9 wt% or less, and the surface drying temperature of the mixture of hydrolyzed ethyl silicate in the ferromagnetic powder is 200°C. Hereinafter, by setting the annealing temperature after forming to 600° C. or lower, an excellent powder magnetic core material can be obtained. Therefore, No. 1 that deviates from this condition. 2.No
．． 5, No. 14 is ineligible.

[0034]

[Effects of the Invention] As explained above, since the powder magnetic core material and the method for manufacturing the same according to the present invention have the above-mentioned structure and have excellent magnetic properties, they can be used in noise filters and choke coils. This has the effect that powder magnetic core material suitable for use as electromagnetic components such as active filters can be obtained.

Claims (2)

[Claims] 1. A ferromagnetic powder that can be recovered by annealing at a temperature of 600° C. or less is mixed with SiO2 as a binder.
A powder magnetic core material containing 9 wt% or less and solidified and molded. 2. Ethyl silicate obtained by adding water and alcohol to ferromagnetic powder to cause a hydrolysis reaction is mixed, the surface of the mixture is dried at a temperature of 200°C or lower, and after press molding, the mixture is heated to a temperature of 600°C or lower. A method for producing a powder magnetic core material with excellent magnetic performance, the method comprising annealing at a temperature of .