RU2326461C2 - Composition of powder, method for manufacture of soft magnetic components and soft magnetic constituent - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, in particular, to the production of soft magnetic composition parts. It may be used for the manufacture of stator and rotary cores of electric machines. The powder composition contains iron-based soft magnetic powder, the particles of which are covered with an electrically insulating layer, and 0.05-2 % weight of lubricating material from the group including primary amides of saturated or unsaturated linear fatty acids with 12-24 carbon atoms. To prepare the composition, the iron-based powder and the lubrication are mixed, pressed, and heat treated if required. The resulting part has a density of ≥7.5g/cm³, a maximum relative permeability μ_max≥600, a coercitive force Hc < 250A/m, a specific resistance ρ≥ 20mcOhm·m.

EFFECT: preparation of material for manufacture of soft magnetic composition parts with high specifications.

21 cl, 1 dwg, 20 tbl, 9 ex

Description

FIELD OF THE INVENTION

The present invention relates to iron-based powder compositions. More specifically, the invention relates to powder formulations for the production of soft magnetic constituents by means of a metallurgical process for producing powder. The compositions facilitate the production of a soft magnetic composite component having a high density, as well as valuable magnetic and mechanical properties.

BACKGROUND OF THE INVENTION

Soft magnetic materials are used in applications such as core materials in inductors, stators and rotors for electric machines, solenoids, sensors and transformer cores. Traditionally, soft magnetic cores, such as rotors and stators in electric machines, are made from multilayer steel laminate materials. The materials of the soft magnetic composite, SMC, are based on soft magnetic particles, usually based on iron, with an electrically insulating coating on each of them. By extruding isolated particles optionally together with lubricants and / or binders, traditionally using a powder metallurgy process, SMC parts are obtained. Using the powder metallurgy technique, it is possible to produce materials that give a higher degree of freedom in the development of the SMC component compared to using steel laminate materials, since the material of the SMC component can conduct three-dimensional magnetic flux, and three-dimensional shapes can be obtained by pressing.

Two key characteristics of an iron core component are permeability and core loss. The magnetic permeability of a material is an indicator of its ability to magnetize or its ability to conduct magnetic flux. Permeability is defined as the ratio of induced magnetic flux to magnetic field strength or field strength. When a magnetic material is exposed to a magnetic field, energy losses, core losses occur due to hysteresis losses and eddy current losses. Hysteresis losses are created by the necessary energy expenditures to overcome the residual magnetic forces in the iron core component and are proportional to the square of the frequency of the alternating field. Losses due to eddy currents are generated by the formation of electric currents in the iron core component due to a change in flow caused by alternating current (AC) and are proportional to the square of the frequency of the alternating field. As a result, it is desirable to have a high electrical resistivity in order to minimize eddy currents, and it is especially important when operating at high frequencies. In order to reduce hysteresis losses and increase the magnetic permeability of the core component for AC applications, it is generally desirable to heat-treat the extruded part.

Research in the metallurgical production of powder of magnetic core components related to the use of coated iron-based powders was aimed at developing compositions of iron powders that improve some physical and magnetic properties without adversely affecting other properties of the final component. The required component properties include, for example, high permeability over a wide frequency range, low core loss, high saturation induction (high density) and high strength. Typically, increased component density improves all of these properties.

The required properties of the powders include suitability for injection molding methods, which means that the powder can be easily molded into a high-density component that can be easily removed from the molding equipment, and that the components have good surface finish.

The present invention relates to a new powder composition having the desired powder properties, as well as the use of the powder composition for the preparation of soft magnetic composite components. The new composition can be pressed (and subjected to heat treatment) to components having the desired properties.

The present invention also relates to a method for manufacturing iron-based soft magnetic components having excellent properties, as well as a soft magnetic component per se.

SUMMARY OF THE INVENTION

Briefly, the composition of the powder according to the invention is formed by electrically isolated particles of soft magnetic material and lubricants from fatty acid amides. Additionally, the composition contains a thermoplastic binder. The method according to the present invention includes mixing, pressing and further heat treating the obtained component, resulting in a soft magnetic component based on iron having excellent properties.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The powder is preferably a substantially pure water-sprayed iron powder or porous iron powder having irregularly shaped particles. In this context, the term “substantially pure” means that the powder should be substantially free of inclusions, and that the amounts of impurities O, C and N should be kept to a minimum. The average particle sizes are generally below 300 microns and above 10 microns. Examples of such powders are ABC 100.30; ASC 100.29; AT 40.29; ASC 200; ASC 300; NC 100.24; SC 100.26; MH 300; MH 40.28; MH 40.24, available from Hoganas AB, Sweden.

According to one embodiment of the invention, the powders used have coarser particles than those that are normal in conventional compression molding. In practice, this means that the powders essentially do not have fine particles. The term "substantially free of fine particles" should be understood to be approximately less than 10%, preferably less than 5% of the powder particles have a size of less than 45 μm, measured by the method described in SS-EN 24 497. The average particle diameter is usually between 106 and 425 μm . The number of particles larger than 212 microns is usually above 20%. The maximum particle size can be about 2 mm.

The particle size of iron-based particles commonly used in the powder metallurgy industry, PM, is subject to the normal distribution law with an average particle diameter in the range of 30 to 100 μm, and about 10-30% of the particles have a diameter of less than 45 μm. Thus, the powders used according to the present invention may have a particle size distribution deviating from that commonly used. These coarse powders can be obtained by removing finer particles of the powder or by making a powder having a desired particle size distribution. However, the invention is not limited to coarse powders, but all powders having particle sizes commonly used for compression molding in the PM industry are also included in the present invention.

The electrical insulation of the powder particles can be formed from inorganic material. Particularly suitable is the type of insulation disclosed in US Pat. No. 6,348,265 (which is incorporated herein by reference), which relates to shale powder particles consisting of almost pure iron having an oxygen and phosphorus-containing insulating layer. As for the coating, it should be especially noted that the thickness of the coating can affect the properties of the composite component. Powders having isolated particles are available under the name Somaloy ™ 500 and 550 from Hoganas AB, Sweden.

The lubricant according to the invention is selected from the group consisting of fatty acid amides. Particularly suitable amides are primary amides of a saturated and unsaturated fatty acid having 12-24, preferably 14-22 carbon atoms, and most preferably 18-22 carbon atoms. Lubricants can be used in amounts of less than 2% and preferably less than 1.5 wt.% Of the composition. Particularly preferred quantities of lubricant are 0.05-1%, preferably 0.05-0.8%, more preferably 0.1-0.8% and most preferably 0.1-0.5 wt.%, Particularly preferred lubricants the materials are stearic acid amide, oleic acid amide, behenic acid amide, erucic acid amide, palmitic acid amide, with stearic acid amide being most preferred. In US Pat. No. 6,537,389, stearic acid amide, apparently in combination with rapeseed oil methyl ester, is referred to as a lubricant in combination with a thermoplastic resin, polyphthalamide, as a binder for compressing soft magnetic powders.

Solid lubricants generally have a density of about 1-2 g / cm ³ , which is very low compared to a density of iron-based powder, which is about 7.8 g / cm ³ . As a result, the inclusion of these less dense lubricants in the compositions will be lower than the theoretical density of the pressed component. Therefore, in order to produce high density components, it is important to keep the amount of lubricant at low levels. However, low amounts of lubricants tend to create ejection problems. It has been unexpectedly discovered that the type of the aforementioned lubricants can be used at low amounts without ejection problems.

By replacing internal lubricants, that is, lubricants added to an iron-based powder mixture, with mold wall lubrication, DWL, in combination with high pressing pressures, high densities of freshly pressed components can be achieved. However, the disadvantage of the known known method when pressing an insulated iron-based powder is that its insulation is easily damaged, leading to high core losses at higher frequencies. Moreover, the use of DWL further complicates the process and can increase cycle times and reduce production reliability.

According to the present invention, a fatty acid amide can only be used as an additive to an isolated iron powder or iron-based powder. Although for some applications it is advantageous to add minor amounts of thermoplastic resin, especially polyphenylene sulfide (PPS). The term "minor amounts" in this context should be understood as less than 2, preferably less than 0.8, more preferably less than 0.6 and most preferably less than 0.5 wt.% From the composition. At amounts below 0.05, no effects are observed. In particular, the amount of PPS may vary between 0.1 and 0.5, and preferably between 0.2 and 0.5 or 0.4 wt.%. PPS is especially interesting when good frequency stability is required.

The combination of PPS and stearic acid is well known from patent specification WO 01/22448. Examples of this description disclose that soft magnetic material can be obtained by mixing an electrically insulated iron-based powder with PPS and stearic acid. The mixture is pressed at elevated temperature, and the obtained pressed part is subjected to heat treatment at a temperature of 260 ° C in a nitrogen atmosphere, followed by a second heat treatment at a temperature of from 285 to 300 ° C. Surprisingly, it has been found that by using a new powder composition that includes a fatty acid amide instead of the corresponding fatty acid, several advantages can be obtained. Thus, it was found that the new powder has unexpectedly improved lubricating properties, which leads to the fact that lower energy is required to push the pressed part out of the mold, which allows to obtain higher densities and better tensile strength at transverse rupture. Moreover, the pressing step may be performed at ambient temperature. Heat treatment can also be facilitated since the first heat treatment step, which is required according to the WO publication, can be skipped.

Iron-based magnetic powders having isolated particles and combining with thermoplastic resins are described in US Pat. No. 2,002 / 0084440. In contrast to the particles of the present invention, similarly known particles also include a rare earth element. In addition, thermoplastic resin is used in relatively large quantities, namely at least 5 wt.%. Additionally, the particle size of the iron-based powder is small enough (3 μm is mentioned as an example). A lubricant selected from a wide variety of chemical compounds may also be included. It is believed that these powder compositions are preferably useful for injection molding, extrusion, injection compression molding and injection molding for the preparation of coupled permanent electromagnets that are resistant to atmospheric influences.

In order to prepare the constituent components of the present invention, the composition of the powder is first coaxially pressed into a mold, which usually should not be lubricated, although the composition of the powder can also be used in lubricated molds. Then the pressed component is pushed out of the mold and further subjected to heat treatment.

Pressing can be performed at ambient temperatures and pressures up to 1500 MPa.

According to a preferred embodiment of the present invention, the pressing is carried out in a moderately heated tool, since in this way not only the density of the freshly pressed components and the ejection behavior are improved, but also the maximum relative permeability. When comparing the properties of components pressed at an elevated temperature and at a lower pressing pressure with the properties of components pressed to the same density of freshly pressed components at ambient temperature and at a higher pressing pressure, the component pressed at an elevated temperature will have a higher permeability . For larger components, as well as to achieve improvements according to the invention, it may be necessary to increase the temperature of the powder.

Heat treatment can be performed in one or several stages. The recommended one heat treatment step is carried out from 30 minutes to 4 hours in an oxygen-containing atmosphere (air) at a temperature between 250 and 550 ° C.

Alternatively, heat treatment can be performed at a temperature of 250-350 ° C for a period of 30 minutes to 3 hours in air or an inert gas, followed by heat treatment from 15 minutes to 2 hours in an oxygen-containing atmosphere (air) at a temperature of 350-550 ° C.

Somewhat excellent heat treatment is recommended when PPS is included. Thus, in this case, the heat treatment can be performed at a temperature of 250-350 ° C from 30 minutes to 4 hours in an oxygen-containing atmosphere (air). Another alternative is to perform heat treatment at a temperature of 250-350 ° C from 30 minutes to 3 hours in air or an inert gas, followed by heat treatment at a temperature of 300-500 ° C from 15 minutes to 2 hours in an oxygen-containing atmosphere (air )

The possibility of performing heat treatment in various atmospheres, at different periods of time and at different temperatures, in order to obtain a final component having the required properties, makes the new powder composition particularly attractive.

By compressing a composition containing an insulated iron-based powder having coarse particles and a lubricant as described above at high pressures, for example above 800 MPa, followed by heat treatment of the pressed component, soft magnetic composite components having a density of ≥ 7.5 can be obtained g / cm ³ , maximum relative permeability μ _max ≥600, coercive force Hc≤250 A / m and specific resistance ρ≥20 μOhm · m. Such components may be of interest for applications required, for example, in stator or rotor components in electrical machines.

The invention is further illustrated by examples.

EXAMPLE 1

Used the following materials.

An iron-based water-dispersible powder with particles having an inorganic coating (Somaloy ™ 500, available from Hoganas AB, Sweden) was used as starting material.

PPS Powder

Stearic Acid Powder, Lubricant A.

Stearic Acid Amide Powder, Lubricant B.

3 kg of Somaloy ™ 500 base powder was mixed with PPS and stearic acid amide or stearic acid, according to table 1.

Table 1
Powdered mixtures: lubricants and PPS (wt.%) Sample Number PPS - Polyphenylene Sulfide Lubricant A1 0.60% 0.2% A A2 0.50% 0.3% A A3 0.50% 0.3% B A4 0.30% 0.3% B A5 0.30% 0.4% B A6 0.30% 0.5% B A7 0.1% 0.3% B A8 0.2% 0.3% B A9 - 0.4% B

The powder mixtures were pressed into ring-shaped samples with an inner diameter of 45 mm, an outer diameter of 55 mm, and a height of 5 mm at a pressure of 800 MPa at ambient temperature (room temperature). Ring-shaped samples 10 mm high were also pressed, and the buoyancy was measured on these samples. The buoyancy energy is shown in Table 2. The results show that significantly lower buoyancy energy is obtained using fatty acid amides.

table 2
The ejection energy measured on ring-shaped samples with a height of h = 10 mm Sample Number PPS Lubricant Ejection Energy (J / cm ² ) A1 0.60% 0.2% A 52 A2 0.50% 0.3% A 46 A3 0.50% 0.3% B 38 A4 0.30% 0.3% B 37 A5 0.30% 0.4% B 33 A6 0.30% 0.5% B thirty A7 0.10% 0.3% B 41 A8 0.20% 0.3% B 39 A9 - 0.4% B 35

After pressing, the parts were heat-treated at a temperature of 290 ° C for 120 minutes in air. 25 turns were wound on the obtained heat-treated rings. Relative induction permeability on alternating current was measured with an LCR meter (inductive-resistive-capacitive) type HP4284A according to standard IEC (IEC) 60404-6, 2nd edition 2003-06.

The fall in the initial permeability (frequency stability) is shown in Tables 3 and 4. The fall in the initial permeability is expressed as the difference between the initial permeability at 10 and 100 kHz divided by the initial permeability at 10 kHz. Table 3 shows that by increasing the amount of fatty acid amide from 0.3 to 0.5%, better frequency stability can be obtained. Table 4 shows that by using a fatty acid amide instead of the corresponding fatty acid, better frequency stability can be obtained. Moreover, Table 4 discloses that without PPS, a greater drop in frequency stability is obtained. However, it turned out that the initial 1 kHz permeability for A9 is 95 compared to 75 for A3. For some applications, high initial permeability at low frequencies is beneficial.

Table 3
Drop in initial permeability Dμ 10-100 kHz (%) A4 7.4 A5 5.2 A6 4.2

Table 4
Drop in initial permeability Dμ 10-100 kHz (%) A2 6.4 A3 3.9 A9 20.9

The resistivity was measured at four points, the results are shown in table 5. From this table it can be concluded that by using a fatty acid amide instead of the corresponding fatty acid, a significantly higher electrical resistivity can be obtained.

Table 5
Resistivity for ring-shaped samples Sample Number PPS Lubricant Electrical resistivity μOhm * m A2 0.50% 0.3% A 316 A3 0.50% 0.3% B 400

Samples were also tested for transverse tensile strength, TRS, after heat treatment at 290 ° C for 120 minutes in air. The TRS parameter was tested according to MOS 3995. The TRS limit was also tested in parts at a temperature of 200 ° C. The TRS limit is also shown in Table 6. A sample with 0.5% PPS and 0.3% fatty acid amide (A3) showed a significantly higher TRS limit both at room temperature (RT) and at 200 ° C compared to both samples, a sample with 0.5% PPS and 0.3% stearic acid (A2) and a sample with 0.2% PPS + 0.6% stearic acid (A1). The density is higher for a mixture with a low total organic content, which will lead to higher induction and permeability (μmax).

Table 6
Density and TRS at room temperature and at 200 ° C Sample Number PPS Lubricant Density after heat treatment, g / cm ³ TRS at room temperature, MPa TRS at 200 ° C, MPa A1 0.60% 0.2% A 7.18 68 51 A2 0.50% 0.3% A 7.18 46 thirty A3 0.50% 0.3% B 7.19 81 67 A4 0.30% 0.3% B 7.27 88 73 A5 0.30% 0.4% B 7.22 87 73 A6 0.30% 0.5% B 7.17 51 68 A7 0.10% 0.3% B 7.35 85 74 A8 0.20% 0.3% B 7.31 84 71 A9 - 0.4% B 7.33 87 78

EXAMPLE 2

Used the following materials.

An iron-based water-dispersible powder with particles having a thin phosphorus-containing inorganic coating (Somaloy ™ 500, available from Hoganas AB, Sweden) was used as starting material.

PPS Powder

Stearic Acid Powder, Lubricant A.

Stearic Acid Amide Powder, Lubricant B.

Behenic Acid Amide Powder, Lubricant C.

Oleic acid amide powder, D Kenolube ™ lubricant.

Somaloy ™ 500 Base Powder was mixed with PPS and lubricants according to the following table 7.

Table 7
Powdered mixtures: lubricants and PPS (wt.%) Sample Number PPS Lubricant IN 1 0.50% 0.3% A IN 2 0.50% 0.3% B IN 3 0.50% 0.3% C AT 4 0.50% 0.3% D AT 5 0.30% 0.3% B AT 6 - 0.4% B AT 7 - 0.3% B AT 8 0.1% 0.3% B AT 9 0.2% 0.3% B AT 10 - 0.4% Kenolube ™

Powdered mixtures were pressed into test rods according to MOS 3995 standard at a pressure of 800 MPa at ambient temperature. After pressing, the parts were heat treated in a two-stage heat treatment process. The first stage was carried out at a temperature of 290 ° C for 105 minutes in an inert nitrogen atmosphere. After this step, a second heat treatment step was followed at a temperature of 350 ° C. for 60 minutes in air. Samples were tested for transverse tensile strength, TRS, according to MOS 3995.

The transverse tensile strength test results are shown in Table 8. As can be seen from Table 8, samples prepared with a mixture comprising a fatty acid amide give sufficient TRS values. A higher density is achieved after heat treatment, which is beneficial in terms of induction and permeability. If the PPS content decreases to 0.3% or less, then the TRS increases to values above 80 MPa. Samples without PPS and with stearic acid amide lubricant even have TRS values above 100 MPa. The use of Kenolube ™, a mineral lubricant, does not result in the required tensile strength at transverse rupture.

Table 8
Density and TRS at room temperature Sample numbers PPS Lubricant Density after heat treatment, g / cm ³ TRS at room temperature, MPa IN 1 0.50% 0.3% A 7.18 73 IN 2 0.50% 0.3% B 7.22 68 IN 3 0.50% 0.3% C 7.23 73 AT 4 0.50% 0.3% D 7.24 74 AT 5 0.30% 0.3% B 7.32 83 AT 6 - 0.4% B 7.37 108 AT 7 - 0.3% B 7.41 113 AT 8 0.1% 0.3% B 7.35 88 AT 9 0.2% 0.3% B 7.32 79 AT 10 - 0.4% Kenolube ™ 7.42 32

EXAMPLE 3

This example shows that, compared with traditional lubricants based on zinc stearate and stearic acid amide and stearic acid ethylene bisamide, low ejection forces are obtained during extrusion of pressed components and an excellent surface finish of the ejected component when fatty acid amide based lubricants according to The invention is used in low amounts in combination with coarse powders and at high pressing pressures.

Two kilograms of iron-based coarse soft magnetic powder in which the particles are surrounded by inorganic insulation according to US Pat. and F are comparative examples containing known lubricants.

Table 9 Mixture Lubricant A Behenic Acid Amide B Erucic acid amide C Stearic acid amide D Oleic acid amide E Zinc stearate F Stearic Acid Ethylene Bisamide

Table 10 Particle size (μm) Weight, % > 425 0.1 425-212 64,2 212-150 34.0 150-106 1,1 106-75 0.3 45-75 0.2 <45 0

The resulting mixtures were transferred to a mold and pressed into cylindrical prototypes (50 grams) with a diameter of 25 mm, with a coaxial movement of the press at a pressing pressure of 1100 MPa. The mold material used was ordinary tool steel. During the ejection of the pressed samples, the ejection force was recorded. The total ejection energy / coverage area required to eject the samples was calculated. The following table 11 shows the ejection energy, the density of freshly pressed samples and the quality of the surface treatment.

Table 11 Mixture Ejection energy
(J / cm ² ) Density of Freshly Pressed Samples
(g / cm ³ ) Surface finish A 90 7.64 Perfect B 83 7.65 Perfect C 93 7.63 Perfect D 70 7.67 Acceptable E 117 7.66 Unacceptable F 113 7.64 Perfect

EXAMPLE 4

The following example illustrates the effect of the particle size distribution of an iron-based soft magnetic powder on the ejection pattern and on the density of freshly pressed samples. The coarse powder was used according to Example 3. The particle size distribution of the fine powder is given in Table 12. The mixtures were prepared using 0.2 wt.% Stearic acid amide according to the procedure of Example 3. The fine powder mixture is labeled as sample H , which was compared with sample C.

Table 12 Particle size (μm) Weight, % > 425 0 425-212 0 212-150 11,2 150-106 25.0 106-75 22.8 45-75 26.7 <45 14.3

The mixture was pressed into cylindrical samples according to the procedure used in example 3. The following table 13 shows the density of the freshly pressed samples and the quality of the surface treatment.

Table 13 Mixture The density of freshly pressed samples (g / cm ³ ) Surface finish C 7.63 Perfect H 7.53 Acceptable

As can be seen from table 13, the composition containing the fine powder leads to a lower density of the freshly pressed samples and to a deteriorated surface finish.

EXAMPLE 5

This example compares a known lubricant, stearic acid ethylene bisamide and an example of stearic acid amide lubricant, respectively, according to Table 14. Samples were prepared according to the procedure in Example 3.

Table 14 Mixture EBS wt.% Amide of stearic acid wt.% one 0.20 - 2 0.30 - 3 0.40 - four 0.50 - 5 - 0.10 6 - 0.20 7 - 0.30

The powder mixtures were pressed into rings with an inner diameter of 45 mm, an outer diameter of 55 mm, and a height of 10 mm at a pressure of 1100 MPa. During the ejection of the pressed samples, the total ejection energy / coverage area required to eject the samples from the mold was calculated. The following table 15 shows the calculated expulsion energy / coverage area, density of freshly pressed samples and surface finish.

Table 15
Ejection energy, density of freshly pressed samples, surface finish Mixture Ejection energy
(J / cm ² ) Density of Freshly Pressed Samples
(g / cm ³ ) Surface finish one 54 7.65 Unacceptable 2 40 7.61 Acceptable 3 33 7.56 Perfect four 28 7.51 Perfect 5 73 7.67 Acceptable 6 38 7.64 Perfect 7 37 7.59 Perfect

As can be seen from table 15, it is enough to add a new lubricant in an amount of only 0.2% and still get the perfect surface finish, whereas for a comparative lubricant, EBS, the smallest additive needed to get the perfect surface finish, is 0.4%.

EXAMPLE 6

This example compares the magnetic properties of components made with a minimum amount of stearic acid amide and EBS lubricant components, respectively, to achieve the same ejection energy values. Components made from mixture 2 and mixture 6 according to example 5 were compared with respect to magnetic properties after heat treatment.

Pressed ring-shaped samples according to example 5, except that the height was 5 mm Freshly pressed samples were heat treated at 300 ° C for 60 minutes in air, followed by a second heat treatment step at 530 ° C for 30 minutes in air. The obtained heat-treated rings were wrapped with 100 signal and 100 exciting turns and tested in a Brockhaus hysteresis device. The following table 16 shows the induction level of 10 kA / m, the maximum relative permeability, coercive force Hc and core loss upon induction of 1 T (Tesla) at a frequency of 400 Hz.

Table 16
Soft magnetic properties Sample 2 Sample 6 Maximum permeability 480 750 B at 10000 A / m (turns) 1,58 1,66 Hc (A / m) 218 213 Core loss at 1T at 400 Hz, (watts / kg) 78,4 42.1

As can be seen from table 16, soft magnetic properties are excellent for the components of the present invention.

EXAMPLE 7

The following example illustrates the effect of temperature on the ejection properties and density of freshly pressed samples. In this example, the primary amide, stearic acid amide, was selected as the amide-based lubricant according to the invention. 0.2% stearic acid amide was added to 2 kg of a coarse soft magnetic electrically isolated iron-based powder according to the procedure of Example 3.

The powder mixtures were pressed into rings having an inner diameter of 45 mm, an outer diameter of 55 mm and a height of 10 mm at a pressure of 1100 MPa. During the ejection of the pressed samples, the ejection forces were recorded. The parameter was calculated — the total ejection energy / coverage area necessary to eject the samples from the mold. The following table 17 shows the ejection energy, the density of the freshly pressed samples and the quality of the surface treatment of the samples, compared at different temperatures of the mold.

Table 17
Ejection energy, density of freshly pressed samples, surface finish at various mold temperatures Temperature
(° C) Ejection energy
(J / cm ² ) Density of Freshly Pressed Samples
(g / cm ³ ) Surface finish 25 38,4 7.64 Perfect fifty 31.5 7.66 Perfect 60 30.6 7.67 Perfect 70 29.3 7.67 Perfect 80 27.5 7.69 Perfect

As can be seen from table 17, the push-out energy and the density of freshly pressed samples are positively affected by an increase in mold temperature.

EXAMPLE 8

This example compares the properties of components made according to the present invention with the properties of components pressed using DWL. As in the example of the invention and in the comparative example, a “coarse” powder was used according to example 3. As a lubricant in the example of the invention, 0.2 wt.% Stearic acid amide was used, and the obtained powder composition was pressed at a controlled temperature of the mold 80 ° C in ring-shaped samples having a density of freshly pressed samples of 7.6 g / cm ³ . In the comparative example, no internal lubricant was used at all; instead, it was applied to DWL. Ring-shaped samples were pressed to a density of 7.6 g / cm ³ at ambient temperature.

The ring-shaped samples had an outer diameter of 55 mm, an inner diameter of 45 mm, and a height of 5 mm.

After pressing, heat treatment was performed according to table 18. The resistivity was measured at four points. Before magnetic measurements in a hysteresisograph, ring-shaped samples were wrapped with 100 exciting and 100 signal turns. DC properties, DC, were collected from the circuit at 10 kA / m. Losses in the core were measured by induction of 1 T (Tesla) at various frequencies. Figure 1 presents a graph of core losses per cycle versus frequency.

Table 18
Magnetic properties Sample Heat treatment B _{10kA / m} H _c
(A / m) ρ
(μOhm * m) Core loss at 1 T at 400 Hz (watts / kg) The present invention 530 ° C, 30 min
air 1.65 192 103 41 DWL Method no 1,66 305 60 60 DWL Method 530 ° C, 30 min
air 1,66 189 3 109

From table 18 and figure 1 it can be concluded that the present invention provides significantly lower core losses in alternating fields due to lower H _c value and higher resistivity compared to the DWL method.

EXAMPLE 9

This example shows that by means of the present invention, it is possible to obtain iron powder cores with excellent magnetic properties. The positive effect of elevated mold temperature on maximum relative permeability is also shown.

The "coarse" powder according to example 3 was mixed with lubricants of various contents and types. Both ring-shaped samples (outer diameter = 55, inner diameter = 45, height = 5 mm), and rods (30 × 12 × 6 mm) were made with the process conditions given in table 19.

Density was determined by measuring the mass and size of the ring-shaped samples. The resistivity was measured at four points on the ring-shaped samples. Prior to magnetic measurements in a Brockhaus hysteresis, ring-shaped samples were wrapped with 100 exciting and 100 signal turns. DC properties, DC, such as μmax and H _c were collected from the circuit at 10 kA / m, while core losses were measured at different frequencies with an induction of 1 T at 400 Hz. The tensile strength at transverse rupture (TRS) of the parts subjected to heat treatment was determined on experimental rods by the method of bending at three points.

Table 19
Process conditions for ring-shaped samples Sample Type of lubricant The amount of lubricant (wt.%) Compression Pressure (MPa) Mold Temperature (° C) Heat treatment one Stearic acid amide 0.2 1100 25 300 ° С 45 min, air + 520 ° С *, air 2 Stearic acid amide 0.2 1100 80 300 ° С 45 min, air + 520 ° С *, air 3 Stearic acid amide 0.2 800 80 530 ° C, 30 min, air four Stearic acid amide 0.2 1100 25 530 ° C, 30 min, air 5 Stearic acid amide 0.2 1100 80 530 ° C, 30 min, air 6 Stearic acid amide 0.1 1100 85 530 ° C, 30 min, air 7 Stearic acid amide 0.3 800 25 300 ° С, 1 h, air + 530 ° С, 30 min, air 8 Stearic acid amide 0.3 800 80 300 ° С, 1 h, air + 530 ° С, 30 min, air 9 Stearic acid amide 0.3 1100 25 300 ° С, 1 h, air + 530 ° С, 30 min, air 10 Stearic acid amide 0.3 1100 80 300 ° С, 1 h, air + 530 ° С, 30 min, air eleven Erucic acid amide 0.2 1100 25 330 ° С, 2 h, air + 530 ° С, 30 min, air 12 Erucic acid amide 0.2 1100 25 340 ° C, 2 h, N ₂ + 530 ° C, 30 min, air * - temperature increase at a rate of approximately 4 ° C / min in the component up to 520 ° C

Table 20
Component Property Measurements Sample Density (g / cm ³ ) μmax H _c (A / m) Specific Resistance (μOhm * m) Induction core loss
1 T at 400 Hz (watts / kg) TRS (MPa) one 7.62 754 209 473 42 93 2 7.63 852 204 230 40 97 3 7.60 718 208 103 43 but. four 7.62 602 198 591 39 59 5 7.65 861 178 98 37 68 6 7.71 918 177 66 38 78 7 7.49 669 228 574 46 70 8 7.53 880 202 33 48 81 9 7.56 672 224 515 44 67 10 7.62 860 203 64 43 76 eleven 7.62 633 192 414 38 54 12 7.68 738 205 614 39 67

Claims (21)

1. A powder composition containing a soft magnetic iron powder or iron-based powder, the particles of which are coated with an electrically insulating layer, and 0.05-2 wt.% A lubricant selected from the group consisting of primary amides of saturated or unsaturated linear fatty acids having 12-24 carbon atoms. 2. The composition according to claim 1, characterized in that the fatty acid has 14-22 carbon atoms. 3. The composition according to claim 1, characterized in that the fatty acid amide is selected from the group consisting of stearic acid amide, oleic acid amide, behenic acid amide, erucic acid amide and palmitic amide. 4. The composition according to claim 1, characterized in that it further comprises polyphenylene sulfide. 5. The composition according to claim 4, characterized in that it contains 0.05-2.0 wt.% Polyphenylene sulfide. 6. The composition according to claim 3, characterized in that it contains 0.05-1 wt.% Fatty acid amide. 7. The composition according to claim 1, characterized in that the insulating layer is made of inorganic material. 8. The composition according to claim 1, characterized in that the iron-based powder essentially consists of pure iron. 9. The composition according to claim 1, characterized in that less than 10 wt.% Particles of soft magnetic powder have a size of less than 45 microns. 10. The composition according to claim 9, characterized in that less than 5 wt.% Particles of soft magnetic powder have a size of less than 45 microns. 11. The composition of claim 10, characterized in that at least 20 wt.% Particles of soft magnetic powder have a size above 212 microns. 12. A method of manufacturing soft magnetic parts, comprising preparing a powder composition by mixing a soft magnetic iron powder or iron-based powder, the particles of which are surrounded by an electrically insulating layer, and 0.05-2 wt.% Of a lubricant selected from the group consisting of primary amides of saturated or unsaturated strong fatty acids having 12-24 carbon atoms; pressing the resulting composition and, if necessary, heat treating the resulting part. 13. The method according to item 12, in which the pressing is performed at elevated temperature. 14. The method according to item 12, in which the pressing is performed at a pressing pressure above 800 MPa. 15. The method according to item 12, in which the heat treatment is performed at a temperature between 250 and 550 ° C. 16. The method according to item 12, in which the heat treatment is performed in two stages, and in the first stage at temperatures up to 350 ° C, and in the second at temperatures up to 550 ° C. 17. The method according to item 12, in which the heat treatment is performed in a stream of air or in an inert environment. 18. The soft magnetic composite part obtained by pressing the powder composition according to claim 1 and subsequent heat treatment, which has a density of ≥7.5 g / cm, maximum relative permeability μ _max ≥600, coercive force Hs≤250 A / m, specific resistance ρ≥20 μOhm · m. 19. The item according to p. 18, characterized in that it has a density of ≥7.6 g / cm ³ . 20. The item according to p. 18, characterized in that it has a resistivity of ρ≥100 μΩ · m 21. A component according to claim 18, characterized in that it has a maximum relative permeability μ _max ≥700.