JPH0534814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic articles made as cores and pole pieces, and methods of making them from vitreous metal powders.

Amorphous metal alloys and articles made therefrom are shown by Chien and Polk in U.S. Pat. No. 3,856,513, issued December 24, 1974. That specification teaches new alloy compositions that are obtained in an amorphous state and are superior to previously known crystalline alloys based on the same metal. The compositions shown therein readily become amorphous upon quenching and have desirable physical properties.
The specification further indicates that amorphous metal powders with a powder size in the range of 10 to 250 μm can be produced by milling or air milling of cast ribbons.

It is known to produce magnetic articles by consolidation of permalloy and other crystalline alloy powders. New applications requiring improved magnetic properties have necessitated efforts to develop alloys and compaction methods in which the strength and magnetic response of magnetic articles are simultaneously enhanced.

According to the present invention, an amorphous metal alloy is provided which is particularly suitable for compression into objects exhibiting excellent magnetic response. Further, the present invention provides a method of making a magnetic article using thermo-mechanical methods to compress vitreous metal powder.

Articles made by the method of the invention have low remanence and magnetic permeability, which are constant over a wide range of frequencies. Generally, compressed magnetic glassy metal alloy bodies of this type have a relative magnetic permeability of at least 15.
As used herein, the term "relative permeability" refers to the ratio of the magnetic induction produced in a medium by a particular magnetic field to the magnetic induction produced by the same magnetic field in vacuum.

More specifically, according to the present invention, ferromagnetic vitreous metal powder is compressed by static pressure at a pressing temperature of 69 to 690 MPa, which is around the glass transition temperature and below the crystallization temperature of the alloy. In this way, a molded article of magnetic metal alloy is manufactured. This makes the compressed magnetic vitreous metal alloy object particularly suitable for post-forming annealing in the presence of a magnetic field of 0-800 A/m for 1-4 hours at temperatures in the range 380-450°C. is formed. This annealed article has improved impedance permeability and is particularly suitable for use in signal and high frequency power transformers and the like.

The invention will be better understood, and other advantages will become apparent, from the detailed description of the preferred embodiments of the invention and the accompanying drawings.

FIG. 1 is a schematic diagram of an apparatus used for casting amorphous metal powder directly from a melt, the apparatus having a knurled casting indicator.

FIG. 2 is a graph showing the change in density of a compressed object as a function of compression time and compression temperature.

FIG. 3 is a graph showing the change in impedance permeability as a function of annealing time after forming.

FIG. 4 is a graph showing the change in impedance permeability as a function of frequency for uninsulated and insulated powders.

FIG. 5 is a graph showing the change in impedance permeability as a function of frequency for cores made from different particle sizes.

FIG. 6 is a graph showing the change in core loss as a function of annealing time after forming.

The magnetic compact bodies of the present invention having a magnetic permeability greater than 15 are generally manufactured from powdered vitreous metal alloys. Common methods for producing glassy metal powders from alloys include a quenching process and atomization.
It involves a process. The alloy is cast directly into ribbon and milled, ball milled or air milled into powder or flakes in the desired particle size range. To assist in the powdering process, the ribbon samples are subjected to an embrittlement heat treatment below the crystallization temperature of the alloy.

Alternatively, powders or flakes (here defined as particles having a small diameter on the order of magnitude larger than their thickness) can be deposited as desired using a casting support with indentations of the type shown in Figure 1. It can be cast directly into a final shape with a range of dimensions. The size of the particles or flakes produced thereby will vary depending on the depth of the incisions and their spacing. In general, a notch contains a number of regularly spaced peaks and valleys, with the distance between adjacent peaks ranging from 0.01 to 0.1 cm, and the distance from the peak of the peak to the bottom of the valley being 0.005 cm.
In the range of ~0.05cm. The shape of such a casting support generally results in powder particles or flakes having dimensions in the range 0.01 to 0.1 cm.

As shown in FIG. 1, the apparatus 10 includes a movable cooling surface 12, a sump 14 for holding molten metal 16, and an opening connected to the sump 14 at the top and adjacent the cooling surface 12 at the bottom. Motsu nozzle 18
have. The cooling surface 12 has regularly spaced peaks 22
and valleys. Adjacent peaks have a distance d between 0.01 and 0.1 cm. The distance y (not shown) from the top of the mountain to the bottom of the valley is 0.005-0.05 cm. The powder is produced directly by dropping the molten alloy onto a scored support (cooling surface 12). The support may be a rotating cooling roll, an endless belt (not shown), etc. set to move longitudinally at a speed of 100 to 2000 m/min. The dimensions of the powder particles thus obtained vary directly with the magnitude of the distances d and y.

In the illustrated embodiment, the nozzle means has a slot oriented generally perpendicular to the direction of movement of the cooling surface. The slot is defined by a pair of parallel lips, a first lip and a second lip numbered in the direction of motion of the cooling surface. Nozzle 18
The slot is 0.2~ measured in the direction of movement of the cooling surface.
It has a width of 1mm. The first lip has a width at least equal to the slot width and the second lip has a width from 1.5 to 3 times the slot width. The gap between the lip and the cooling surface is 0.1 to 1 times the width of the slot. The production of glassy alloys is covered by U.S. Patent No. 3,856,513 (granted to Chien et al.)
This can be done by following the basic teachings provided in the specification. The resulting sheets, ribbons, tapes and wires are useful precursors for the materials described herein.

Compression of powder is the first step in manufacturing an object. Powders for compression include fine powder (with a particle size smaller than 105 μm) and coarse powder (105 μm or smaller).
(with a particle size of 300 μm) and flakes (with a particle size greater than 300 μm). Compaction can be obtained by pressing the glassy metal powder at a temperature near the glass transition temperature and below the crystallization temperature.

If a low magnetic permeability (ie, 25 or less) is desired, a particle size of 105 μm or less is used. For high magnetic permeability (above 100), a relatively large particle size of 300 μm or more is used.

For compaction, the powder is placed in an evacuated can and then formed into strips or isostatically pressed into discs, rings or other desired shapes.
For example, it can be made into transformer and inducer cores, motor stator and rotor parts. Furthermore, the powder can be hot pressed at a temperature below the crystallization temperature and in the glass transition temperature range to form any desired shape, such as a transformer/inducer core or rotor/stator segment of a motor. Compaction is believed to occur through mechanical entanglement and short-range diffusion bonding between powder or flake particles that occur near the glass transition temperature.

Until now, it has been difficult to achieve interparticle bonding with amorphous alloys because they are very hard and do not easily deform under shear or compressive forces. As a result of research, the present inventors have discovered that interparticle bonding can be achieved by appropriately selecting the temperature and pressure for compression treatment, and have completed the present invention.

Since the particles are relatively hard at temperatures well below the glass transition temperature (Tg), they are not easily deformed by the shear and compression forces applied during the compaction process. On the other hand, at temperatures much higher than Tg, there is a high risk of initial crystallization of amorphous particles during compression. On the other hand, it has been found that good interparticle bonding can be achieved if compression is performed at a pressing temperature within a range of approximately 50°C from Tg. Furthermore, the compression pressure is 69 ~
Must be within the range of 690MPa. Outside this range, good interparticle bonding cannot be obtained even if compression treatment is performed within the above temperature range.
In the present invention, it is essential that the two conditions of temperature and pressure are both satisfied.

The powder can also be mixed with a suitable organic binder such as paraffin, polysulfone, polyimide, phenol formaldehyde resin and then cold pressed into the appropriate shape. The amount of binder is 30
% by weight, preferably up to 10% by weight for cores with high magnetic permeability, and more preferably from 0.5 to 3% by weight. The alloy thus formed has a density of at least 60% by weight of the theoretical maximum. The pressed object can be cured at a relatively low temperature below the curing temperature of the binder to provide greater strength and then ground to its final shape. Preferred products of this method include those having a shape suitable as a magnetic component. The curing process can be carried out by simultaneously applying a magnetic field.

Metallic glass is a molten alloy that has been cooled to a rigid state without crystallizing. Metallic glasses of this type generally have at least some of the following properties: High degree of hardness and scratch resistance, great smoothness of the glassy surface, dimensional and shape stability, mechanical stiffness, strength, ductility, high electrical resistance compared to related metals and alloys, and diffusion X-ray diffraction pattern.

The term "alloy" is used here in its ordinary sense as referring to a solid mixture of two or more metals (Condensed Chemical Dictionary, 9th edition, Juan Norstrand Reinhold). , New York, 1977).
These alloys further contain a mixture of at least one non-metallic element. “glassy metal”
metal) alloys”, “metallic gases”,
The terms "amorphous metal alloy" and "vitreous metal alloy" are all used interchangeably herein.

Alloys suitable for the method described in this invention include compositions [Fe, Ni, Co] _65-88 [Mo, Nb, Ta, Cr, V] _0-10
[B, C, S] _5-25 are included.

Preferred ferromagnetic alloys according to the invention are based on a member of the group consisting of iron, cobalt and nickel. Alloys based on iron have a general composition
Fe _40-88 (Co, Ni) _0-40 (Mo, Nb, Ta, V, Cr)
(B _0-10 C, Si) _5-25 , cobalt-based alloys have the general composition Co _40-88 (Fe, Ni) _0-40 (Mo, Nb,
Ta, V, Mn, Cr) _0-10 (B, C, Si) _5-25 ,
The alloys based on nickel have the general composition Ni _40-80 (Co,
Fe) _4-40 (Mo, Nb, Ta, V, Mn, Cr) _0-10 (B,
C, Si) with _5-25 .

A particularly preferred alloy has a composition of 79 atomic percent iron, 16 atomic percent boron, and 5 atomic percent silicon.

Amorphous metal powder can be compressed into molded parts suitable for various uses such as electromagnetic cores and pole pieces. Vitreous metal compacts have high or low magnetic permeability. The obtained core can be used as a transformer core, a motor stator or rotor, and other alternating current applications. Preferred amorphous alloys for this type of application include Fe ₇₈ B ₁₃ Si ₄ ,
Contains Fe ₇₉ B ₁₆ Si ₅ and Fe ₈₁ B _13.5 Si _3.5 C ₂ .

The following examples are presented in order that the invention may be more fully understood. Certain techniques presented to illustrate the principles and practice of the invention;
The conditions, materials, proportions, and data reported are exemplary and should not be construed as limiting the scope of the invention.

Example 1 An amorphous metal powder with a particle size of less than 300 μm and a composition of Fe ₇₉ B ₁₆ Si ₅ (values written below are in atomic percent) was prepared as detailed in U.S. Pat. No. 4,142,571. Ribbons casted directly from the melt according to the method were produced by air milling. The casted ribbons were placed under an inert nitrogen atmosphere before ball milling for 16 hours.
An embrittlement treatment was also performed at 400°C for 1 to 2 hours. This operation yielded fine amorphous particles in the range of 300 to 10 μm. The resulting fine powder particles were divided into various particle size ranges, i.e. “-325 mesh” (40 μm mesh).
m), "-150 mesh" (150 μm) and "-
It was sieved to a size of 48 mm (300 μm).
The powder is reduced to 1-3% by weight by mixing the particles with a slurry containing SiO ₂ and methanol.
Coated with SiO ₂ or 1% by weight MgO using a slurry containing MgO and methanol. -150 mesh and -325 coated
410-510 mesh size powder in graphite mold
Pressing was carried out for 5 minutes, 15 minutes and 30 minutes at temperatures in the range of .degree. The pressure used was 69 MPa.
Since it was not possible to accurately measure the glass transition temperature for the Fe ₇₉ B ₁₃ Si ₉ alloy, the crystallization temperature
The heating press was performed over a wide temperature range of 410 to 510°C, which is lower than T _X (=530°C). The variation in core density as a function of pressing conditions is shown in FIG.
The ideal density of approximately 80-85% was obtained at 460°C for 1/2 hour. However, at higher temperatures the pressing time can be reduced to obtain the same density. Various molds can also be fabricated for direct hot pressing into desired shapes needed for specific applications: rods, toroids, EI shapes, etc.

Example 2 Amorphous metal particles having an alloy particle size of 105 μm or less and a composition of Fe ₇₉ B ₁₆ Si ₅ were milled by air milling as shown in Example 1, and as-cast ribbons were
It was made brittle by heat treatment at 400°C for 1 hour, and then pulverized in a ball mill. The air milled powder particles were coated with 1% by weight MgO.
A toroid core (inner diameter = 25 mm, outer diameter = 38 mm, and thickness = 12 mm) was molded and pressed at 430°C for 1/2 hour. To evaluate the effect of post-processing annealing, press-formed cores made from both insulated and non-insulated powders were
C. for 1 to 4 hours, and the corresponding impedance permeability was measured and plotted in FIG.

Post-forming annealing has been found to substantially improve permeability, with optimal annealing being 1 to 2 hours at 435°C for the particular composition and compression method employed in this example. .

Example 3 Amorphous metal powder particles having an alloy particle size of 105 μm or less and a composition of Fe ₇₉ B ₁₆ Si ₅ were produced by air milling as described in Example 1.

To evaluate the insulation effect, 1 to 3 wt% SiO ₂ or
A toroid core (inner diameter = 25 mm, outer diameter = 38 mm, and thickness = 12 mm) was created using MgO. The formed core was then annealed at 435°C for 1 hour.
The impedance permeability was measured as a function of frequency (1-100 KHz with .1 terrace induction).
The results are shown in Figure 4. The impedance permeability for an insulated powder core does not vary with frequency. In contrast, the magnetic permeability for an uninsulated core decreases with frequency due to eddy current shielding. This constant magnetic permeability is a very important magnetic property desired in signal and high frequency power transformers.

Example 4 Different particle size ranges: “-48 mesh size” (300 μm) and “-150 mesh size”
(150 μm) was prepared by air milling according to the method described in Example 1. The powder particles were coated with 1 wt % MgO and compacted into toroidal specimens (inner diameter = 25 mm, outer diameter = 38 mm and thickness = 12 mm) and annealed after shaping at 435° C. for 1-2 hours. The impedance permeability of this core was plotted as a function of frequency. As shown in FIG. 5, higher magnetic permeability was obtained as the particle size increased.

Example 5 In order to use it as a core of a power transformer, in addition to impedance permeability, core loss characteristics are also important. The same alloy as described in Example 1
Using Fe ₇₉ B ₁₆ Si ₅ and the same forming process, insulation (1%
MgO) powder to toroid core (inner diameter = 25 mm,
An outer diameter of 38 mm and a thickness of 12 mm were manufactured. The formed cores were annealed at 435°C for 1 to 3 hours. 50K
Hz/. Figure 5 shows the core loss value at 1 Tesla. The optimal heat treatment appears to be 2 hours or more at 435°C. High frequency core loss values were substantially reduced with decreasing grain size and with 1-3 wt% insulation. The powder and insulation properties required for optimal low frequency (60-400 Hz) core loss are substantially different from those required for high frequencies. At low frequencies, eddy currents are not dominant, so for use in 60-400Hz transformers and motors, relatively large particles (e.g. 300 μm or more) without insulation are required.
is desirable. In addition, for use in this type of low-frequency transformers and motors, the molding process must be performed at relatively low temperatures (e.g., in the range of 380 to 420°C) to avoid partial crystallization of the amorphous matrix. Annealing should be performed. For high frequency applications, the particle system is relatively small (e.g. 105 μm or less), and the particles are coated with an insulator (e.g. MgO, _SiO2, etc.).
The annealing temperature is in the range of 420-450℃.

Although the present invention has been described in more detail above, it is not necessary to adhere to these detailed descriptions, and it is obvious that various changes and modifications can be made to those skilled in the art, all of which are within the scope of the claims. It will be understood that it is within the scope of the invention as defined by.

[Brief explanation of the drawing]

FIG. 1 is a schematic representation of an apparatus used for casting amorphous metal powder directly from a melt, the apparatus having a knurled casting support. FIG. 2 is a graph showing the change in density of a compressed object as a function of compression time and compression temperature. FIG. 3 is a graph showing the change in impedance permeability as a function of annealing time after forming. FIG. 4 is a graph showing the change in impedance permeability as a function of frequency for uninsulated and insulated powders. FIG. 5 is a graph showing the change in impedance permeability as a function of frequency for cores made from different particle sizes. FIG. 6 is a graph showing the change in core loss as a function of annealing time after forming. The symbols in Figure 1 indicate the following. 12... Cooling surface, 14... Reservoir, 16... Molten metal, 18... Nozzle, 20... Nozzle opening,
22...Notched Mountain, 24...Notched Valley.

Claims (1)

[Claims] 1. Ferromagnetic glassy metal powder is compressed by static pressure at a pressure of 69 to 690 MPa at a pressing temperature within a range of approximately 50°C from the glass transition temperature and below the crystallization temperature of the alloy. , a method for producing a molded article of a magnetic metal alloy, including the step of forming a compressed magnetic glassy metal alloy body. 2. The method according to claim 1, wherein the compression step is carried out for 1 to 60 minutes. 3. The method according to claim 2, wherein the powder consists of particles having a particle diameter of 105 μm or less. 4. The method of claim 1, wherein the powder consists of particles with a particle diameter of at least 300 μm. 5. The method of claim 3, comprising the step of coating the particles with an insulator before the compression step. 6 Particles are compressed in a graphite mold during the compression process at 410~
6. A method according to claim 5, characterized in that pressing is carried out for 5 to 30 minutes at a temperature in the range of 510<0>C. 7 Compressed alloy objects at temperatures ranging from 380 to 450°C
3. The method of claim 2, comprising the step of annealing for ~4 hours. 8. The method according to claim 7, wherein the annealing step is performed in the presence of a magnetic field of 0 to 800 A/m.