KR101375986B1 - Method for manufacturing fe??si magnetic core by metal injection molding - Google Patents

Abstract

The present invention is a method for manufacturing a Fe-Si based magnetic core by metal powder injection molding comprising the steps of: manufacturing a donut shaped specimen by injection molding after mixing Fe-Si based powder and a chemical bonding agent; and high temperature sintering after chemical debinding and thermal debinding to remove the chemical bonding agent from the donut shaped specimen. According to the method of the present invention, when manufacturing the Fe-Si based magnetic core, the loss of magnetic hysteresis is reduced by high temperature, thereby improving the soft magnetism property by magnetization-demagnetization.

Description

Method for manufacturing Fe­Si-based magnetic core by metal powder injection molding {Method for manufacturing Fe­Si magnetic core by metal injection molding}

The present invention relates to a method for producing a Fe­Si-based magnetic core having excellent soft magnetic properties using metal powder injection molding.

In general, FeSi-based alloys are widely used as a component material for motors and generators where energy efficiency is important in automobile, electronics, battery, and telecommunication industries as typical soft magnetic materials. Various studies have been conducted on mechanical or magnetic properties.

Korean Patent Publication No. 10-0262488 discloses a method of manufacturing a sintered iron-silicon soft magnetic alloy using a powder metallurgy as an example of a method of manufacturing such Fe­Si-based alloy.

Considering microstructural aspects on magnetic properties, the effect of porosity and grain size after sintering is important. It was suggested that the saturation coercivity value decreased with increasing grain size.

However, in the case of using the conventional powder metallurgy, distinct grain growth has occurred as the sintering temperature is increased, and in particular, the porosity is increased to 10% or more, so that the saturation coercivity value decreases rapidly.

The present invention is to provide a sintering temperature conditions for producing a magnetic core exhibiting the most efficient and excellent magnetic properties through the sintering process after the metal powder injection molding of Fe­Si powder alloy.

The present invention comprises the steps of mixing the Fe­Si powder and the chemical binder, followed by injection molding to prepare a donut shaped specimen; And a high temperature sintering step after performing chemical degreasing and thermal degreasing to remove the chemical binder from the donut-shaped specimen, thereby providing a Fe­Si-based magnetic core manufacturing method through a metal powder injection molding method.

In addition, the content of Si in the Fe­Si powder may be 5 to 8 parts by weight based on 100 parts by weight of the Fe­Si powder, and the chemical binder may be a multi-component and polymer-based mixture.

In addition, the chemical degreasing, thermal degreasing and high temperature sintering may be performed in an inert gas atmosphere, and the sintering time may be 1 to 3 hours in the high temperature sintering step, and the sintering temperature may be 1275 in the high temperature sintering step. It may be to 1325 ℃.

According to the manufacturing method of the present invention, the magnetic hysteresis loss value is reduced through the high temperature sintering when the Fe­Si-based magnetic core is manufactured, thereby improving soft magnetic properties due to magnetization-demagnetization.

1 is a process chart for the FeSi-based magnetic core manufacturing method through the metal powder injection molding method of the present invention.
Figure 2 is an SEM image showing the shape and size of the metal powder used in the present invention.
Figure 3 is a graph showing the time and temperature in the thermal degreasing and high temperature sintering step of the present invention.
4 is an optical image showing the microstructure of the FeSi-based magnetic core through the metal powder injection molding method according to the sintering temperature,
(a) is an optical image showing the microstructure of a FeSi-based magnetic core through a metal powder injection molding method sintered at 1100 ℃
(b) is an optical image showing the microstructure of the FeSi-based magnetic core by metal powder injection molding sintered at 1200 ℃
(c) is an optical image showing the microstructure of the FeSi-based magnetic core through the metal powder injection molding method sintered at 1300 ℃.
5 is a magnetic history graph of the FeSi-based magnetic core through the metal powder injection molding method according to the sintering temperature,
(a) is a graph measuring magnetic permeability and saturation coercivity with sintering temperature,
(b) is a graph which measured the magnetic permeability and saturation coercivity with respect to the sintering temperature which expanded near the origin of (a).
6 is a graph showing the magnetic history loss according to the sintering temperature at the measurement frequency between 1 ~ 20 kHz.

The present invention comprises the steps of mixing the Fe­Si powder and the chemical binder, followed by injection molding to prepare a donut shaped specimen; And it provides a Fe­Si-based magnetic core manufacturing method through a metal powder injection molding method comprising the step of performing high temperature sintering after performing chemical degreasing and thermal degreasing to remove the chemical binder in the donut-shaped specimen.

In an embodiment of the present invention, the content of Si in the FeSi powder is 5 to 8 parts by weight based on 100 parts by weight of FeSi powder, 5 to 7 parts by weight based on 100 parts by weight of FeSi powder or 5 to 6.5 by weight of 100 parts by weight of Fe-Si powder. It may be part by weight, but is not limited thereto.

In an embodiment of the invention, the chemical binder may be a multicomponent and polymeric mixture. The multicomponent system is a wax and may preferably be a paraffin wax. The polymer system may be selected from the group consisting of polypropylene, acrylic resin, and stearic acid, but is not limited thereto.

In an embodiment of the present invention, the sintering time in the high temperature sintering step may be 1 to 3 hours, 1 to 2 hours or 2 to 3 hours, but is not limited thereto.

In an embodiment of the present invention, the sintering temperature in the hot sintering step may be 1275 to 1325 ℃, 1285 to 1315 ℃, 1295 to 1315 ℃, but is not limited thereto.

In an embodiment of the invention, the injection molding may be carried out at a temperature of 100 to 150 ℃ at a pressure of 800 to 1300 bar.

According to the Fe­Si-based magnetic core manufacturing method through the metal powder injection molding method according to the present invention, after the metal powder injection molding, it is possible to obtain a Fe­Si-based magnetic core to reduce the magnetic loss through a high temperature sintering process.

1 is a schematic view showing a method of manufacturing a Fe­Si-based magnetic core through the metal powder injection molding method of the present invention.

Referring to Figure 1, the Fe­Si-based magnetic core manufacturing method through the metal powder injection molding method, after mixing the Fe­Si powder 10 and the chemical binder 20, and injection molding to prepare a donut-shaped specimen (11).

In the donut-shaped specimen 11, the chemical binder 20 is removed through chemical and thermal degreasing, followed by high temperature sintering to manufacture the Fe-Si-based magnetic core 12.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the contents of the present invention, but the scope of the present invention is not limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

<Experimental Example>

The following experimental examples are intended to provide experimental examples that are commonly applied to each embodiment according to the present invention.

The present invention used Fe­6.5% Si powder manufactured by ATMIX of Japan.

Table 1 and Figure 2 shows the composition, shape and size of the powder used in the present invention. The average size of the spherical powder is about 10 μm and the density is 7.51 g / cm 3. Paraffin wax, polypropylene, acrylic resin, and stearic acid are used as the chemical binder, and 50 g of the paraffin wax, 30 g of the polypropylene, 10 g of the acrylic resin, and 10 g of the stearic acid are mixed. This injection molding machine (NEX 50, Nissei) was used to inject into the donut-shaped specimen. To remove the wax binder from the injected specimens, 100% N-hexane was used to completely submerge the injection molded donut-shaped specimens for 20 hours, followed by thermal degreasing and sintering to remove the remaining binder. Was performed at a time. As shown in FIG. 3, the temperature was raised at a rate of 2 ° C. per minute and maintained at 600 ° C. for 2 hours to perform thermal debinding. Then, the temperature was raised to 2 ° C. per minute and the temperature was increased to 1100, 1200, and 1300 ° C. Hot sintering was carried out for 2 hours at. Degreasing and sintering processes were all performed in a high purity nitrogen atmosphere which is an inert gas.

Si C Mn Cr Ni Cu Mo Fe 6.53wt% 0.014wt% 0.04wt% 0.04wt% 0.02 wt% 0.02 wt% 0.01 wt% Honey.

Example 1 Examination of Microstructure Change

In order to observe the microstructure after sintering, the size of the crystal grains and the porosity present in the specimen were measured by an image analyzer (Image pro +) through corrosion of the Nital solution and optical microscope observation.

Figure 4 is an optical image showing the microstructure of the Fe­6.5% Si material according to three different sintering temperature.

Referring to Figure 4, the microstructure consists of a ferrite single phase and a number of micropores were observed. Table 2 shows the micro histological results analyzed by the image analyzer.

Temperature Volume ratio (%) Average size (㎛) Aspect ratio ferrite Micropores ferrite Micropores ferrite Micropores 1100 ℃ 88 12 20 12 0.16 0.51 1200 ℃ 93 7 36 10 0.13 0.31 1300 ℃ 95 5 ≥1500 8 0.07 0.19

In general, in the case of powder metallurgy, grain growth is known to occur as the sintering temperature increases. When comparing the results of 1100 and 1200 ℃ the grain size was about 2 times the difference (Fig. 4 (a) and (b)). When sintering was carried out at 1300 ℃ as shown in Figure 4 (c), the grains were grown significantly compared to the two conditions.

In relation to the formation of micropores after sintering, the porosity was about 5% at the sintering condition of 1300 ° C. and showed the highest sintered density value in this experimental condition (FIG. 4 (c)).

Table 2 shows the results of aspect ratio of grains and pores. The closer to 0 the pore aspect ratio was, the more spherical it was, which was 0.51 at 1100 ° C and 0.19 at 1300 ° C, more than twice the aspect ratio. Therefore, when the high temperature sintering was carried out at 1300 ℃, the ferrite grain size was the largest, mainly spherical pores developed, and the porosity was the lowest.

Example 2 Investigation of Magnetic Properties

Magnetic properties are characterized by a hysteresis curve and magnetic hysteresis loss using a hysteresis curve (AE TECHRON BH curve tracer) and an IWATSU BH analyzer on a donut-shaped FeSi material. ) Values were measured respectively.

FIG. 5 shows magnetic hysteresis curves according to three sintering temperatures of the metal powder injection molded Fe6.5% Si alloy, and FIG. 5 (b) shows magnetic permeability and saturation coercivity. It is a photograph which enlarged the vicinity of the origin of FIG. 5 (a). Representative magnetic properties such as magnetic permeability, saturation magnetization, and coercivity can be evaluated from the hysteresis curve. The measured values are shown in Table 3.

Sintering temperature 1100 ℃ 1200 ℃ 1300 ℃ Self-permeability 149 269 361 Saturation magnetization (tesla) 1.02 1.07 1.22 Saturation Coercivity (kA / m) 2.99 2.44 1.84

In general, soft magnetic materials have to be easily magnetized and demagnetized with a relatively low external magnetic field. This requires high magnetic permeability, saturation magnetization, and low saturation coercivity. Under these conditions, the magnetic hysteresis loss is low and the soft magnetic properties are improved.

From Table 3, when the material was sintered at 1300 ℃, the magnetic permeability and saturation magnetization value were relatively higher than those of the other two conditions, while the saturation coercivity value was the lowest as about 1.84 kA / m.

In addition, when sintered at 1300 ℃ conditions as shown in Figure 4 because the ferrite grain size is the largest, the saturation coercivity value was the lowest.

On the other hand, the factor to be considered in the saturation coercivity is the presence of pores. Micropores inevitably present after metal powder injection molding also increase the saturation coercivity because they restrict the movement of the magnetic domain wall like grain boundaries. In the present invention, since the porosity gradually decreases (or increases in density) as the sintering temperature is increased, the saturation coercivity value is the lowest when performing high temperature sintering at 1300 ° C. Due to the high grain size and densification, when sintered at 1300 ° C., the saturation magnetization values and the low saturation coercivity values were relatively high when compared with other sintering conditions. In addition, as the sintering temperature increases, the area of the magnetic hysteresis curve decreases, so the magnetic hysteresis loss is small.

FeSi-based magnetic core and FeSi-based magnetic core prepared through the normal solidification of the fine structure and magnetic properties of the FeSi-based magnetic core prepared by the metal powder injection molding method according to the present invention In comparison, it is shown in Table 4.

ingredient Fe­6.5% Si Fe­6.5% Si­0.06% B Fe­6.5% Si Manufacturing method Metal Injection Molding (MIM) (1300 ℃) Powder Metallurgy (PM) (1350 ℃) Directional solidification Porosity (%) 5 4.7 - Grain size (μm) ≥1500 110 100 ~ 200 (width) Saturation magnetization (tesla) 1.22 1.53 ~ 1.14 Saturation Coercivity (kA / m) 1.84 - ~ 0.12

6 is a graph showing the magnetic history loss according to the sintering temperature at the measurement frequency between 1 ~ 20 kHz. Frequency intensity and magnetic hysteresis loss generally have a linear proportionality, and the results show the same tendency. In the tendency of the hysteresis loss value according to each frequency, the difference in the hysteresis loss value is insignificant at low frequency regardless of the sintering temperature, but the difference in value is remarkable as the sintering temperature increases as the frequency intensity increases. The magnetic hysteresis loss (~ 770 mW / cm 3) of the material sintered at 1300 ° C. at 20 kHz was about 70% lower than that at 1100 ° C. (~ 1140 mW / cm 3).

In summary, as the sintering temperature increased, the saturation magnetization value increased while the coercive force value decreased, and the saturation magnetization value was 1.22 tesla, the highest at 1300 ℃. The coercive force was decreased by grain growth (or grain boundary reduction) and porosity reduction (or densification) with increasing sintering temperature and the lowest 1.84 kA / m at 1300 ℃. In addition, as the sintering temperature was increased in the metal powder injection-molded Fe6.5% Si alloy, the magnetic hysteresis loss decreased, and the soft magnetic properties due to magnetization demagnetization were improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that such detail is solved by the person skilled in the art without departing from the scope of the invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

10: FeSi powder
11: Donut Shaped Specimen
12: FeSi magnetic core
20: chemical binder

Claims (6)

Mixing the FeSi powder and the chemical binder, followed by injection molding to prepare a donut shaped specimen; And
A method of manufacturing a FeSi-based magnetic core through a metal powder injection molding method comprising: performing a chemical degreasing and thermal degreasing to remove a chemical binder from the donut-shaped specimen, followed by high temperature sintering at 1275 to 1325 ° C. The method of claim 1,
The Si content of the FeSi powder is 5 to 8 parts by weight based on 100 parts by weight of FeSi powder, FeSi-based magnetic core manufacturing method through a metal powder injection molding method. The method of claim 1,
The chemical binder is a multi-component and polymer-based mixture, FeSi magnetic core manufacturing method through a metal powder injection molding method. The method of claim 1,
Wherein the chemical degreasing, thermal degreasing and hot sintering step is performed in an inert gas atmosphere, FeSi-based magnetic core manufacturing method through a metal powder injection molding method. The method of claim 1,
The sintering time in the step of high temperature sintering is 1 to 3 hours, FeSi-based magnetic core manufacturing method through a metal powder injection molding method. delete

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