KR100332898B1 - Method for manufacturing soft magnetic core including steelmaking dust - Google Patents

Abstract

PURPOSE: A method for manufacturing a soft magnetic core by adding pure iron powder with steelmaking dust through powder metallurgy process, thus it is possible to manufacture soft magnetic core with excellent magnetic properties similar to those of pure iron core. CONSTITUTION: The method includes the steps of sorting steelmaking dust to separate steelmaking dust with a particle size of less than 250 micrometers, wherein the iron oxides in the steelmaking dust occupies greater than 12 wt.% in case that only metal components excluding oxygen is calculated in weight ratio, and wherein the steelmaking dust has a melting point of less than 1200 deg.C; mixing sorted steelmaking dust and pure iron powder with a particle size of 44 to 150 micrometers; adding 0.5 to 2 wt.% of binder with above mixture powder; dissolving admixture of the mixture of binder and the mixture powder with solvent, followed by drying; molding the dried powder at a pressure of 8 to 10 ton/cm¬2; and sintering the compact under reduced atmospheric condition of 10¬-5 torr at 1200 to 1350°C for 0.5 to 3 hrs.

Description

Manufacturing method of soft magnetic sintered core containing dust in steel mill

The present invention relates to a method for producing soft magnetic sintered core, and more particularly, by adding steel mill dust to pure iron powder to produce sintered core by powder metallurgy, which has magnetic properties equivalent to or higher than that of pure iron sintered core. It relates to a method for producing a soft magnetic sintered core containing dust in steelworks.

Along with the recent mechatronics of OA, computer-related fields, and even the mechanical industry, cores of electronic, electrical and mechanical parts, detection systems such as ARS (Anti-Lock Brake System), which are not materials for high-frequency application parts, DC Materials such as motor stators, solenoid plungers, and printer heads are rapidly increasing in demand for cores with small and high performance characteristics and complex end parts. . In order to satisfy such demands, magnetic cores with excellent soft magnetic properties, such as Fe-based and Fe-Ni-based materials, are manufactured in powder metallurgy to the shape of the final part or the shape close to it, minimizing material loss and having excellent production efficiency. Research has been underway to produce.

However, in general, it is well known that sintered material is difficult to increase the density due to the nature of the raw material is a powder, and in particular, exhibits significantly poor magnetic properties compared to the solvent material. Therefore, efforts to express higher sintered densities and thus good magnetic properties (Japanese Patent Laid-Open No. 52-32809, Japanese Laid-Open No. 62-103343, and 2-57615) have been raced.

On the other hand, in integrated steelworks with steelmaking and steelmaking facilities, a huge amount of dust of different physicochemical properties is generated depending on the generation process.

The utilization and / or disposal of these dusts will require additional equipment and costs.

In addition, in such a process there is a problem in terms of environmental protection because there is a waste of heavy metal components harmful to the human body in any form.

As already mentioned, in general, the soft magnetic sintered material produced by the powder metallurgy method is inferior in magnetic properties compared to the material produced by melting due to the pores (pore) inherent therein. In addition, the coercive force and permeability, which are the soft magnetic properties, are not only severely changed in physical properties due to structure sensitivity, but also change in physical properties, particle size, purity of sintered products, It is greatly influenced by internal stress distribution and porosity (sinter density) during molding.

Therefore, the present inventors have conducted metallurgical studies and experiments to prevent the phenomenon of deterioration of magnetic properties due to the addition of impurities even when steelmaking dust is added to pure iron to produce sintered cores. At the same time, a method for producing a sintered core containing dust in steelworks having a magnetic level equivalent to that of a pure iron sintered core has been proposed.

That is, an object of the present invention is to provide a method for producing iron-containing dust containing sintered cores having soft magnetic properties equal to or higher than that of pure iron-sintered cores by controlling the manufacturing method by adding iron-generating dusts to pure iron at an appropriate amount and proper particle size. To have

1 is a microstructure photograph of the sintered core prepared by the method of the present invention

Figure 2 is a graph showing the change of alternating magnetic properties and sintered density according to the sintering temperature and the amount of dust added in the stainless steel dust dust sintered core manufactured by the method of the present invention

Figure 3 is a graph showing the alteration of alternating magnetic properties and sintered density according to the sintering temperature and the amount of dust added in the ladle process dust containing sinter core during the steelmaking process produced by the method of the present invention

The present invention for achieving the above object in the method for producing a soft magnetic sintered core,

Classifying steel mill dust having a melting point of 1200 ° C. or less and oxygen in an oxide form containing 12 wt% or more of iron (Fe) in a weight ratio of only 250 μm or less;

Mixing pure iron (Fe) powder having a particle size of 44-150 μm with the classified dust;

Adding a binder in the range of 0.5-2% by weight to the mixed powder, dissolving it in a solvent, and mixing and drying the mixture;

Molding the dried powder to a pressure range of 8-10 ton / cm 2; And

And sintering the molded body in a vacuum atmosphere of 10 ⁻⁵ torr or less for 0.5-3 hours in a range of 1200-1350 ° C., to a method for manufacturing a steelworks dust-containing soft magnetic sintered core.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, steel mill dust suitable for the present invention may be a steel mill dust having a melting point of 1200 ° C. or less and present in an oxide form containing iron (Fe) by 12% by weight or more when only a metal component excluding oxygen is included in a weight ratio. The reason is that, as shown in Figure 1, the oxide-type dust added to the pure iron powder must be lower than the melting point of the iron and the sintering temperature (1200-1350 ℃) to be melted in the sintering process to partially fill the pores inside the pure iron sintered body This is because it may solidify without reacting with pure iron and exist in a mixed state with pure iron. That is, during sintering, dust having a low melting point should melt first, and only the dust is coalesced by the surface tension of the liquid, so that material movement with pure iron should not be performed. Therefore, since it is simply mixed with iron without generating new compounds or inclusions, the influence of impurities in the sintered core can be minimized and magnetic properties such as magnetic flux density, permeability, iron loss, and coercivity can be maintained.

In addition, the reason that the iron (Fe) should be contained more than 12% by weight, if the density of the oxide dust is too small, that is, if the iron content is less than 12% by weight, the dust is much lower than the pure iron in the dust much amount of core This is because the magnetic properties deteriorate, such as the density of the sintered body is significantly reduced by increasing the volume. In order to suppress this as much as possible, it is preferable that the weight of the dust contains 12 wt% or more of iron (Fe) when converting only the metal component excluding oxygen.

Representative types of steel mill dust suitable for the present invention are Fe: 40-45% by weight, Cr: 13-17% by weight, Ca: 9-12% by weight in terms of weight ratio of metallic part excluding oxygen, and the rest And dust generated in the stainless steel making process including Cl, Zn, Mn, Cu, Si, Ni, and K.

As another representative type of steel dust suitable for the present invention, Mg: 25-30% by weight, Ca: 22-26% by weight, Fe: 12-26% by weight when only the metal components excluding oxygen are converted in weight ratio, Dust generated in the ladle furnace process of the steelmaking process including the remaining Mn, K, Si, Al, P, S, and Ti.

Such dusts are usually collected by a dust collector after the vaporized metal reacts with oxygen in the furnace to form a composite oxide, the size of which is a fine powder having an average particle diameter of 1 μm or less, and in some cases, is a fraction More than 1000 micrometers is also found. This is because such a dust may reduce the magnetic flux density in the magnetic properties of the sintered core by reducing the density of the sintered compact by using a sieve of 250 µm or less.

The classified dust as described above is mixed with pure iron (Fe) powder, the addition amount of the dust generated in the stainless steel process to the amount of pure iron powder is added in 3-10% by weight, and in the ladle process during the steelmaking process The amount of dust generated is preferably added at 3-5% by weight. The reason is that when it is added below 3% by weight, relatively good magnetic properties are obtained in comparison with pure iron sintered core, but the amount of dust available in terms of recycling of dust is not significant. When more than 10% by weight or 5% by weight of dust is added, it means that the core contains much larger dust in the form of composite oxide in the form of composite oxide, which means that the magnetic flux density decreases significantly as the volume increases. This is because it severely affects the magnetic properties.

At this time, the pure iron powder has a particle size of 44-150㎛, because the magnetic density after the sintering is higher than the magnetic flux density value is high, but the contamination on the surface due to the increase of the surface area of the powder and the small grain size The grain boundary increased due to condensation adversely affects the soft magnetic properties such as coercive force and permeability, and it is because high magnetic flux density cannot be obtained because high sintered density cannot be obtained during sintering due to the reduction of contact area between powders. At this time, more preferably in the range of 74-150㎛ for the best soft magnetic properties.

The mixed powder mixed as described above adds a binder in the range of 0.5-2% by weight to increase the strength during molding. The reason for this is that when 0.5 wt% or less is added, the binder strength is significantly reduced when the binder is removed from the vacuum oven before sintering. The core form collapses or becomes very difficult to handle, and when 2.0 wt% or more is added, the sintering time for the same sintering density is increased at the same sintering temperature, which adversely affects productivity problems and soft magnetic properties of the residual binder. This is because the possibility increases. More preferably, 1.0 weight% of binder is added. In this case, a representative type of the binder may be paraffin.

As described above, the binder added to the mixed powder is dissolved in a solvent, mixed and dried. The solvent may be dissolved in paraffin, and may be dissolved by adding one of hexane and toluene.

In order to increase the sintered density of the dried powder as described above, it is good to increase the density of the molded body as much as possible. In this case, the molding pressure is preferably in the range of 8-10 ton / cm 2 and molded into a mold coated with lubricant.

The reason for this is that high molding density cannot be obtained below 8ton / cm2, and mold breakage is feared above 10ton / cm2, and the stress inside the powder may adversely affect the magnetic properties due to the strong friction between the mold and the powder. This is because the pressure is more preferably 10 ton / cm 2.

The molded article molded as described above is preferably sintered for 0.5-3 hours in the range of 1200-1350 ° C. in a vacuum atmosphere of 10 ⁻⁵ torr or less.

This is because a small amount of oxygen or nitrogen remaining in the reaction chamber when the vacuum condition is out of the conditions may adversely affect the soft magnetic properties sensitive to the structure by generating oxygen and nitrogen compounds in the microstructure of the sintered body.

In addition, the sintering temperature and time are preferably 1100-1350 ° C and 1-3 hours, respectively, because the low sintering temperature and the short sintering time decrease the sintering density and the change in the core shape when the sintering temperature is high and the time is longer than necessary. And sticking of magnetic domains may lead to rather undesirable effects on core properties. More preferably, 1 hour is good at 1350 degreeC.

As described above, molding and sintering the mixed powder containing pure iron powder and dust according to the conditions of the present invention enables the production of sintered core to which steel mill dust having excellent soft magnetic properties is added.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Composite oxide type dust is the main component of Fe: 40-45% by weight, Cr: 13-17% by weight, Ca: 9-12% by weight in terms of weight ratio of only metal components excluding oxygen. The remaining Cl, Zn, Mn Dust generated in the stainless steel making process including Cu, Si, Ni, and K is classified to a particle size of 250 μm or less, and weighed to be 1-20% by weight based on the weight of the core to be manufactured, and then 150 μm. 5 wt%, 10 wt%, and 20 wt% of pure iron (Fe) powder were mixed.

1% by weight of paraffin of the core weight to be prepared in each of the mixed powder was dissolved in hexane, mixed well with powder and dried, and then applied to a mold having zinc stearate coated with a lubricant and an outer diameter of ø10 mm and 15 ø mm, respectively. After charging, a molded article having a thickness of about 2 mm was produced at a pressure of 10 tons / cm 2 of vertical pressure. After the paraffin was removed in a vacuum oven at 150 ° C. for 1 hour, sintering was performed at a sintering temperature of 1100-1350 ° C. in a vacuum sintering furnace having a vacuum degree of 10 ⁻⁵ torr or less.

The effects of the sintering temperature and the amount of dust added on the alternating magnetic properties and the sintered density of the cores produced by the above method were measured at room temperature, and the results are shown in FIG. 2 in comparison with the magnetic properties of pure iron cores. In FIG. 2, the magnetic flux density B ₁₅ and the coercive force Hc are measured values in an alternating magnetic field of 60 Hz and 150e.

As shown in FIG. 2, the density having a large influence on the magnetic properties shows a tendency of a slight increase with increasing temperature, and it was found that almost all of the sintering reaction was completed at about 1100 ° C. In particular, pure iron powder exhibited a very high sintered density of about 7.4 g / cm 2, reaching 95% of the theoretical density of iron. On the other hand, the sintered density according to the amount of dust added was systematically decreased as the amount added, the value of 90% of the iron powder core at 6.64g / ㎠ when added 20% by weight. This is considered to be a natural result of the addition of dust in the form of a low density composite oxide.

As magnetic properties, magnetic flux density (B ₁₅ ) and coercive force (Hc) also showed the same tendency to increase as the sintering temperature increased. Since the magnetic flux density (B ₁₅ ) is the number of magnetic fluxes per unit area, it is natural to increase as the sintering density increases, and it is in good agreement with the sintering density change with respect to the sintering temperature and the amount of dust added.

Particularly, the magnetic flux density (B ₁₅ ) of pure iron powder core shows 1.29 Tesla (T) when sintered at 1350 ° C, and the magnetic flux density (B ₁₅ ) characteristics are somewhat poor when 5 wt% and 10 wt% dust is added. Although a considerable amount of fine dust was added in the volume, very good characteristics were shown as 1.14 Teslo (T), 88% of pure iron powder, and 0.98 Teslo (T), 77%, respectively. This means that the magnetization process can be easily carried out in spite of the addition of fine dust in the magnetic field of 150e magnetically.

On the other hand, the coercive force (Hc) exhibits almost the same behavior as that of the change in magnetic flux density (B ₁₅ ) with respect to the sintering temperature and the amount of dust added. That is, the lower the sintering temperature, the larger the amount of dust added, the smaller the coercive force (Hc) is.The value measured in the 150e applied magnetic field only shows that the magnetic flux density (B ₁₅ ) is smaller but the smaller coercive force (Hc) is increased when the dust content is increased. ) Soft magnetic properties.

Table 1 below shows the DC magnetic properties of the inventive examples and the comparative examples sintered at 1350 ° C. showing the best magnetic properties in the present invention.

As shown in Table 1, Inventive Example (1-4) and Comparative Example (1) are difficult to compare quantitatively and precisely because they are not obtained from completely identical process variables such as molding pressure and sintering conditions including sintering atmosphere. When the addition of stainless steel process dust up to 10% by weight of the core weight, the relatively poor category of the magnetic properties of the pure iron powder sintered core of Comparative Example (1) (B _max = 10kG, Hc = 2.50e, μ _max = 1800, p = 6.8g / cm <3>) showed favorable enough magnetic characteristics.

In addition, it was confirmed that the magnetic properties of the pure iron powder (measured at 150e applied magnetic field) defined in ASTM A811-87 as shown in Table 2 were within the limits.

The cause of this characteristic can be clearly seen through the microstructure photograph of the invention example (4). That is, as shown in Fig. 1, in the sintered structure of 1350 ° C, dust having a low melting point is melted first to form a phase (B) in which dust is coalesced, and the phase (B) in which the dust is coalesced is a known phase (the sintered structure of iron) It was observed in A). In addition, as a result of the component analysis of the phase (B) in which the matrix (A) and the dust are combined, it was confirmed that there was no movement of the substance (component) during the sintering process. That is, the components of the phase (B) in which dust was coalesced in the known phase (A) were not detected, which means that the matrix (A) and the phase (B) in which the dust was coalesced were present in the mixed state in the sintered structure. . It is considered that the characteristics of the sintered structure can maintain magnetic properties such as magnetic flux density (B15), magnetic permeability (Hc) permeability, and iron loss of the sintered core compared to the pure iron sintered core.

Example 2

Composite oxide type dust is Mg: 25-30% by weight, Ca: 22-26% by weight, Fe: 12-26% by weight in terms of weight ratio of only metal components excluding oxygen, and the remaining Mn, K, Si The core produced by mixing, forming and sintering the dust generated in the process of steelmaking process ladle comprising Al, P, S, and Ti in the same manner as in Example 1 was mixed, molded and sintered in a certain weight ratio. Next, the effects of sintering temperature and dust addition amount on the alternating magnetic properties and sintered density of the cores were measured at room temperature. The results are shown in FIG. 3 in comparison with the magnetic properties of pure iron cores. In Fig. 3, the magnetic flux density B ₁₅ and the coercive force Hc are values measured in an alternating magnetic field of 60 Hz and 150 e.

As shown in FIG. 3, since the change in magnetic properties is qualitatively consistent with the change in FIG. 2, the result can be considered with the same contents. However, the sintered density which has the greatest influence on the magnetic flux density (B ₁₅ ) is 7.81g / cm3 to 6.81g when 5% by weight, 10% by weight, and 20% by weight are added, respectively, compared to the dust generated in the stainless steelmaking process. / Cm 3, from 6.94 g / cm 3 to 6.72 g / cm 3 and from 6.64 g / cm 3 to 6.02 g / cm 3, thus the magnetic flux density (B ₁₅ ) is also reduced from 11.4 tesla (T) to 0.91 tesla (T), respectively. And significantly lowered from 0.98 Tesla (T) to 0.72 Tesla (T) and 0.72 Tesla (T) to 0.42 Tesla (T).

This result may be due to the fact that the ladle process dust was smaller than the stainless steel production dust in the iron content and was free of Cr, Ni and components, but contained a large amount of light metals such as Mg and Al.

Table 3 below shows the direct current magnetic properties of the inventive example and the comparative example (1) sintered at 1350 ° C. showing the best magnetic properties in the present invention.

As shown in Table 3, when the process dust is added to the ladle during the general steelmaking process up to 5% by weight of the core weight as in Example 1, the magnetic properties of the pure iron powder sintered core of Comparative Example (1) The bad category (B _max = 10 kG, Hc = 2.50e, μ _max = 1800, p = 6.8 g / cm 3) showed good magnetic properties.

In addition, it was confirmed that the magnetic properties of the pure iron powder (measured at 150e applied magnetic field) defined in ASTM A811-87 as shown in Table 2 were within the limits.

As described above, in the present invention, by adding the appropriate amount of steel dust at an appropriate particle size and controlling the manufacturing method, pure iron sintered core does not move material with pure iron and does not generate new compound or inclusions and is simply mixed with iron. Compared with the above, there is an effect that can provide a method for producing a sintered core containing steel mill dust having soft magnetic properties equal to or higher than that.

In addition, the present invention has a useful effect that can be added to the core of the parts that require high value added to the steel mill dust to be discarded or require additional equipment for reproduction, and is required for small size and high performance.

Claims (9)

In the method for producing a soft magnetic sintered core, Classifying the steel mill dust having a melting point of 1200 ° C. or less and oxygen in an oxide form containing 12 wt% or more of iron (Fe) in a weight ratio of only 250 μm or less; Mixing pure iron (Fe) powder having a particle size of 44-150 μm with the classified dust; Adding a binder in the range of 0.5-2% by weight to the mixed powder, dissolving it in a solvent, and mixing and drying the mixture; Molding the dried powder to a pressure range of 8-10 ton / cm 2; And Sintering the molded body in a vacuum atmosphere of 10 ⁻⁵ torr or less for 0.5-3 hours in a range of 1200-1350 ° C .; Steel mill dust-containing soft magnetic sintered core manufacturing method characterized in that it comprises a. The method of claim 1, wherein the steel mill dust is a dust produced in the stainless steel manufacturing process. The method of claim 2, wherein the dust generated in the stainless steel manufacturing process is based on the weight ratio of only metal components excluding oxygen, Fe: 40-45% by weight, Cr: 13-17% by weight, Ca: 9-12% by weight Is a main component, and the remaining Cl, Zn, Mn, Cu, Si, Ni, K comprising a method for producing a steel mill dust-containing soft magnetic sinter core. 4. The method of claim 2 or 3, wherein the dust generated in the stainless steel process is added by 3-10% by weight. The method of claim 1, wherein the ironworks dust is a dust generated in the ladle process during the steelmaking process. The dust generated in the ladle process during the steelmaking process is Mg: 25-30% by weight, Ca: 22-26% by weight, Fe: 12-26 A method for producing a steel mill dust-containing soft magnetic sintered core, characterized in that the weight% is a main component and comprises the remaining Mn, K, Si, Al, P, S, and Ti. The method of manufacturing a steel mill dust-containing soft magnetic sintered core according to claim 5 or 6, wherein the dust generated in the ladle process during the steelmaking process is added by 3-5 wt%. The method of claim 1, wherein the binder is paraffin. 2. The method of claim 1, wherein the solvent is one selected from hexane and toluene.

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