JPH0689438B2 - Iron-rich metallic glass with high saturation magnetic induction and excellent soft ferromagnetism at high magnetization rates - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to iron-rich metals with high saturation magnetic induction, which exhibit particularly outstanding soft ferromagnetic properties under high magnetization rates. It relates to a glassy alloy.

2. Description of Prior Art Metallic glass-like alloys (metallic glasses) are metastable materials without long-range order. They are conveniently produced by rapid quenching from the melt by processing methods customary in the art. Examples of this type of metallic glass and their method of manufacture are given in US Pat. Nos. 3,856,513, 4,067,732 and 4,142,571. The advantageous soft magnetism of the metallic glasses presented in these specifications has been utilized extensively in their wide use as materials for various magnetic cores in distribution transformers, switch mode power supplies, tape recording heads and the like.

The particular applications of current interest in soft magnetic cores are collectively referred to as pulsed power. In these applications, low average inputs with long acquisition times are converted to outputs with high peak power delivered with short transit times. When producing such high power pulsed electrical energy, a very rapid reversal of magnetization occurs up to 100 T / μs (or 100 MT / s) in the core material. Examples of pulsed power applications include saturable reactors for magnetic pulse compression and circuit element protection during turn-on, and pulse transformers in linear induction particle accelerators.

Metallic glasses are highly suitable for pulsed power because of their high resistivity and thin ribbon shape, which results in low loss under rapid magnetization reversal. (See, for example: (i) "Metallic glass in high energy pulsed power systems", CHSmith, G
lass ... Current Issues , Light and Dupai (AFW
right, J.Dupuy), edited by (NATO ASI Series E, No.92, Martinus Nizhoff Publisher, Netherlands, Dordrecht, 1
985) p.188-199. ) Furthermore, metallic glasses do not have magnetocrystalline anisotropy due to their amorphous nature, and therefore have extremely large values under rapid magnetization rates, close to the theoretical maximum of twice the saturation magnetic induction of the material. It can be annealed to give it a flux swing. The advantageous aspects of these metallic glass materials allow them to be used as magnetic core materials in various pulsed power applications: high power pulsed power supplies for linear induction particle accelerators, energy from pulsed power supplies to the beams of these accelerators. As an induction module for rings, as a magnetic switch in generators, in the study of inertial confinement fusion, and as a magnetic modulator for driving excimer lasers.

In typical pulsed power applications, the core material is first "parked" or biased to a particular magnetic state by the application of an appropriate external magnetic field. For example, the magnetic core material is brought into a negative saturated state by applying a large negative DC electric field. (The direction in which the magnetic core material is saturated during this application is called the positive direction.) Then, when this electric field is removed, the magnetic core material is placed under a negative remanence. While the former process can provide a maximum flux swing of twice the saturation magnetic induction of the magnetic core material, the latter process known as pulse reset is most commonly employed for convenience. In that case, the maximum magnetic flux fluctuation is the sum of remanence and saturation magnetic induction. Hereinafter, unless otherwise specified, the term “maximum magnetic flux fluctuation” means a value determined by the sum of residual magnetism and saturated magnetic induction. Metallic glass can be easily annealed to obtain a saturation magnetic induction, B _s , a Br _r value, remanent magnetic induction that is very close to B _s . The input to be compressed or transformed in the application is then applied to the core material.

Most pulsed power applications require high saturation magnetic induction in the core material, which results in large flux swings in the core. The core material should also preferably have a low induced magnetic anisotropy energy. A low induced magnetic anisotropy energy reduces core loss by establishing an optimal ferromagnetic domain structure and thus allows the core to operate with higher efficiency. Methograss (METGLAS®) 2605CO (nominal composition: Fe ₆₆ Co ₁₈ B, obtained from Allied Signal)
₁₅ Si ₁ ) is a high magnetic induction metallic glassy alloy currently used in many of the above mentioned pulsed power applications. This metallic glass is taught in U.S. Pat. No. 4,321,090, which shows metallic glass with high saturation magnetic induction. The saturated magnetic induction of this glassy alloy in the annealed state is about 1.75T. However, the high cobalt content of this alloy gives rise to high values for the magnetic anisotropy energy and thus high core loss. A value of about 900 J / m ³ for the magnetic anisotropy energy of this alloy is among the highest obtained in metallic glasses. Despite its high magnetic induction, only about 3.2T from this alloy
The maximum magnetic flux fluctuation of is obtained. In addition, the high Co of this alloy
The raw material cost increases depending on the content. Considering that the magnetic core used for this pulsed power application contains up to 100 kg of magnetic core material per magnetic core, and considering that Co is classified as a strategic substance, a substantially lowered level of Co
A more economical alloy containing is highly desirable.

The cobalt-free metallic glassy alloy is Methograss® 2605SC (nominal composition: Fe ₈₁ B _13.5 Si _3.5 C ₂ ) obtained from Allied Signal. This alloy is shown in U.S. Pat. No. 4,219,355. The low magnetic anisotropy energy of this alloy (about 100 J / m ³ ) has been used for certain pulsed power applications. However, the low saturation magnetic induction (~ 1.57T) and correspondingly low maximum flux swing (~ 2.9T) available from this alloy prevents its widespread use in pulsed power applications.

Metallic glassy alloys that provide a combination of high magnetic induction (large flux swing) and low magnetic anisotropy energy would be highly desirable for pulsed power applications.
Further advantages would be gained if such an alloy provided economics in manufacturing costs.

SUMMARY OF THE INVENTION The present invention provides an iron-rich magnetic alloy that is at least 80% glassy and features a combination of high saturation magnetic induction and low magnetic anisotropy energy. Generally, the metallic glassy alloys of the present invention have a composition described by the formula Fe _a Co _b B _c Si _d C _e . In the formula, ae is atomic% and a is
72-84, b is 2-8, c is 11-16,
d is 1-4 and e is 0.5-4. The other metallic glassy alloys of the present invention also have the structure described by the formula Fe _a Co _b Mn _f B _c Si _d C _e . A-f in the formula is atomic%, and a-f
e is the same as above, and f is 1 or less. When properly annealed, the above metallic glasses show a large value in terms of DC fluctuation from negative remanence to positive saturation. As a result, the saturation magnetic induction in the alloy of the present invention was 1.55-1.75T.
And the magnetic anisotropy energy is 300-400 J / m ³ , and the above DC fluctuation is generally 2.9-3.2T.

The metallic glasses of the present invention are particularly suitable for use in large cores for pulsed power applications requiring high magnetization rates. Typical examples of this type of application are high power pulsed power supplies for linear induction particle accelerators, induction modules for coupling energy from pulsed power supplies to the beams of these accelerators, magnetic switches of generators in the study of inertial confinement fusion, And a magnetic modulator for driving an excimer laser. Other applications include airborne transformers (airb
orne transformer), current transformer, earth leakage circuit breaker, switch mode power supply, etc.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and other advantages will become apparent by reference to the following detailed description of the preferred embodiments of the invention and the accompanying drawings.

FIG. 1 is a schematic diagram of a dynamic magnetization curve obtained when an extremely high magnetization speed is applied to a ferromagnetic material, where H _a is the applied magnetic field and ΔB is the total magnetic induction. FIG. 2 is a plot of core loss for a preferred metallic glass of the invention on a log-log scale as a function of magnetization rate, (dB / dt), obtained by coating a ribbon surface. FIG. 3 shows in a similar plot, the loss obtained with the preferred metallic glasses of the present invention, in a similar plot, due to the two prior art metallic glasses currently used commercially in magnetic cores for pulsed power applications. All data in this figure were obtained from coated and annealed ribbons, compared to the loss obtained; FIG. 4 shows the average magnetic field for the same alloy as FIG. 3 in a similar plot. , H (ave.), The magnetization rate, the figures for are those shown as (dB / dt), function, H (a
ve.) is defined as the core loss per unit of magnetically induced change, ΔB; FIG. 5 shows the core loss obtained with various preferred metallic glasses of the invention as a function of the magnetization rate, (dB / dt). Is plotted on a log-log scale as; and FIG. 6 shows the dependence of H (ave.) On (dB / dt) for the same alloy as FIG. 5 in a similar plot. .

DESCRIPTION OF PREFERRED EMBODIMENTS According to the present invention there is provided an iron-rich magnetic metallic glass alloy that is at least 80% glassy and features a combination of high saturation magnetic induction and low magnetic anisotropy energy. Generally, the metallic glassy alloys of the present invention have the formula Fe _a C
It has the composition described by o _b B _c Si _d C _e . Ae in the formula
Is atomic%, a is 72-84, b is 2-8, c is 11-16, d is 1-4, and e is 0.5-.
It is 4. Another metallic glassy alloy of the present invention has the formula Fe _a C
having the composition described by _{o b Mn f B c Si d} C e. A- in the formula
f is atomic%, ae is the same as above, and f is 1
It is the following. When appropriately annealed, the above metallic glass exhibits a large value in terms of DC fluctuation from negative remanence to positive saturation. As a result, the saturation magnetic induction in the alloy of the present invention is 1.55-1.75 T, the magnetic anisotropy energy is 300-400 J / m ³ , and the above DC fluctuation is generally
It is 2.9-3.2T.

The presence of a small amount of crystalline portion in the glassy alloy tends to impair the optimum soft magnetic performance of the alloy, so the alloy of the present invention is preferably 90% glassy as measured by X-ray diffraction. Yes, and very preferably 100% is glassy. Furthermore, the glassy alloys of the present invention exhibiting a saturation magnetic induction of at least 1.6 T are particularly preferred from the viewpoint of pulse power applications.

Examples of metallic glasses of the present invention include: Fe
₇₅ Co ₆ B ₁₄ Si ₃ C ₂ , Fe ₇₇ Co ₆ B ₁₂ Si ₃ C ₂ , Fe ₇₈ Co ₆ B ₁₂ Si ₃ C ₁ , Fe ₇₉
Co ₂ B ₁₄ Si ₃ C ₂ , Fe ₇₆ Co ₆ B ₁₅ Si ₁ C ₂ , Fe ₇₈ Co ₆ B ₁₂ Si ₁ C ₃ , Fe ₇₇ Co
₇ B ₁₂ Si ₂ C ₂ , Fe ₈₀ Co ₆ B ₁₁ Si ₁ C ₂ , Fe ₇₈ Co ₆ B ₁₂ Si ₂ C ₂ , Fe ₇₆ Co ₆ B
₁₄ Si ₃ Mn ₁ , Fe ₇₈ Co ₈ B ₁₁ Si ₃ , Fe ₈₁ Co ₂ B ₁₄ Si ₃ , Fe ₈₄ Co ₂ B ₁₃ Si ₁
And Fe ₇₉ Co ₆ B ₁₂ Si ₃ .

The importance of high saturation magnetic induction in alloys intended for use in pulsed power applications, such as magnetic switches, is understood as follows: The unit of saturation magnetic induction is Volts-second per square meter (Vs / m ² ) [ 1 (Vs / m ² ) = 1T], a core of constant cross-sectional area will “hold off” a known amount of Vs from the output. Therefore, at a particular input voltage level, this hold-off time will be greater if the core material has a higher saturation magnetic induction.

The presence of Co in the alloy of the present invention increases the saturation magnetic induction level. Cobalt contents below about 2 at.% Only slightly increase the saturation magnetic induction level over alloys containing no cobalt. Higher levels of Co are undesirable due to the substantial cost of the element, as the rate of saturation magnetic induction rise due to the presence of Co is substantially reduced for Co above about 8 at.%.

Carbon containing alloys of the present invention are preferred alloys of the present invention for a variety of reasons: First, it has been found that introducing C into the alloy further increases the saturation magnetic induction level of the alloy. This increase is especially noticeable in alloys containing 11-14 at.% Boron. Therefore, the B content is about 11-14 at.
% Of the alloy of the present invention is more preferred.

It has also been found that the addition of C to a level of only about 2 at.% Results in an increase in the saturation magnetic induction level, above which the saturation magnetic induction level of the alloy begins to decrease. For this reason, alloys of the present invention containing a combination of 11-14 at.% B and 0.5-2 at.% C are particularly preferred. The data in Table I are for showing the effect of C on the saturation magnetic induction of the alloys of the invention.

The second reason why the presence of C is required in the alloy of the present invention is
The introduction of C into the melt improves the handleability of the iron-rich alloy melt. From the perspective of large-scale production of rapidly solidifying ribbons of metallic glass, improving the handleability of alloy melts is an important advantage. A maximum amount of about 4 at.% C in the alloys of the present invention provides an acceptable compromise between loss of saturation magnetic induction level and improved melt handleability. From Table I it will be seen that the saturation magnetic induction of alloys containing 4 at.% C is approximately equal to that of alloys containing no carbon.

Furthermore, the presence of C in the alloys of the present invention is believed to help reduce the magnetic anisotropy energy of the alloys. The magnetic anisotropy energy of a ferromagnetic material is a measure of the energy required to rotate the magnetic moment of the material away from the established preferred alignment direction. The magnitude of this energy governs the ease with which a particular magnetic domain structure can be established in the material.

The importance of low magnetic anisotropy energy, and thus core loss reduction, in alloys intended for use in pulsed power applications is shown in FIG. This figure is a schematic diagram of the dynamic magnetization curve obtained from ferromagnetic material imparted with high magnetization rates ( "B-H loops"); H _a is the magnetic field applied to the magnetic core material, △ B is the magnetic core It is the magnetic flux fluctuation obtained from the material. As shown in this figure, this magnetization curve is divided into five regions (or portions) of the magnetic response from the core material.

In region I, H _a rises rapidly, then reaches a maximum, usually limited by stray inductance, and then in fact often falls. This peak is associated with the establishment of rod-shaped ferromagnetic domains that span the thickness of the ribbon in Region II, with the lowest value of H corresponding to achieving an effective domain wall spacing. Magnetization proceeds due to the movement of these rod-shaped domain walls at very low H _a consumption in region III. Towards the weekend in Region III, the higher mobility of the magnetic domain near the ribbon surface immediately resulted in a single domain wall surrounding the interior of the ribbon, commonly referred to as a "sandwich" domain. Although not understood in detail, it is generally believed in the art that the magnetization behavior in region IV is related to the progress of this sandwich domain before saturation is achieved in region V.

The area included by the dynamic magnetization curve and the vertical axis in FIG.
It represents the core loss of the magnetic core material. This core loss is actually a "half-cycle" loss in which the material travels only half the normal hysteresis loop. Hereinafter, all references to core loss of material with respect to the description of the present invention, whether or not of the present invention, refer to these half cycle losses.

From FIG. 1 it is clear that improved efficiency of rod-shaped domain establishment, ie shortening of the "knee" of region II, can reduce core loss. Since this efficiency is directly related to the ferromagnetic anisotropy energy, alloys intended for use in pulsed power applications should preferably have a low magnetic anisotropy energy.

It is well understood in the art that the magnetic anisotropy energy of Fe-B-Si based metallic glass can be lowered by adding an appropriate amount of the fourth element. As mentioned above, carbon is one such element. Other examples of this kind of element are
Includes Mo, Nb, V and Cr.

However, it was surprisingly found that in Fe-Co-B-Si based metallic glasses, C is the only additive element that enhances the saturation magnetic induction level of the "matrix" alloy. All other additive elements tried reduce the saturation magnetic induction by a substantial amount. First
Table II shows these findings. For these reasons, various additive elements other than carbon listed in Table II are excluded from applications requiring high saturation magnetic induction in magnetic core materials, for example, metallic glassy alloys intended for use in magnetic cores for pulsed power applications. Should.

The effect of Si in the alloys of the invention is to improve the temperature stability of the glassy state of the alloys by reducing their saturation magnetic induction but raising their crystallization temperature. The highest level of Si in the alloys of the invention of about 4 at.% Defines an acceptable balance between these two effects of Si.

It is well known in the art that core loss of a magnetic core can be reduced by using an insulating coating on the surface of the magnetic core material.
This is also true for magnetic cores made from the alloys of the invention. Depending on the materials and methods used, these coatings minimize or eliminate inter-layer shorts in the core and reduce or eliminate contribution to total core loss from inter-layer eddy currents. FIG. 2 shows, in a plot of loss vs. magnetization rate (dB / dt), the extent of core loss reduction obtained for the preferred alloys of the present invention.

The data in this figure were obtained from identically shaped toroidal cores made from coated or uncoated 50 mm wide alloy ribbons of approximately equal mass and given equal anneal. The range of magnetization rates investigated is represented by the data points shown in the figure for the coated ribbon. In this and other figures adopted in connection with the description of the invention, for clarity, only lines which are linear regression corresponding points to the data are shown for all other cases. The coated ribbon was obtained by immersing the as-cast ribbon in a dilute solution of colloidal silica. The host solution was isopropanol in a commercially available colloid and methanol was used for dilution. Examined about 6: 1-about 1
It was observed that in the 0: 1 dilution range, the losses obtained from the coated ribbons were approximately equal. Other dilutions may result in a greater reduction. A combination of other coating methods, such as spray coating or sputter coating, with other coating materials, such as magnesium or organic films, such as polyimide, to achieve a core loss reduction of the invention material that is similar or greater than this. It will be well known to those skilled in the art that Similarly, it is self-evident that the ribbon can be annealed before coating, depending on the coating material.

FIG. 3 shows the loss obtained from the same alloy as in FIG. 2 as a function of the loss obtained from two prior art metallic glasses currently in commercial use in magnetic cores for pulsed power applications. It is a comparison. A 50 mm wide ribbon of all three alloys shown in this figure was coated as detailed above and annealed to each of them under optimal conditions. This figure illustrates the level of loss reduction achieved in the alloys of the invention over a wide range of magnetization rates.

Each of the three alloys represented in FIG. 3 exhibits different maximum flux swings. Therefore, a more direct measure of alloy performance in pulsed power applications is the average magnetic field, H (ave.), Defined as the core loss for maximum flux swing 1T. This magnetic field is determined by dividing the measured core loss by the measured maximum flux swing. Figure 4 is the third
In the same plot of H (ave.) Vs. (dB / dt) as in the figure,
This performance measure is employed to describe the outstanding performance characteristics typical of the alloys of the present invention as compared to commercially available prior art metallic glasses.

The following examples are presented so that the invention might be more fully understood. The detailed procedures, conditions and reported data provided to illustrate the principles and practice of the present invention are illustrative and should not be construed as limiting the scope of the invention.
The alloy compositions described in the examples are nominal compositions.

EXAMPLE A method of teaching a glassy metal alloy designated Sample No. 1-47 in Table III by Narasimhan in U.S. Pat. No. 4,142,571, which is incorporated herein by reference. Quenching from the melt according to. All castings were produced in a vacuum chamber with 0.025-0.100 kg of melt consisting of high purity constituent elements. Ribbon obtained generally thicknesses 25-30μm and a width of about 6mm is by X-ray diffractometry and differential scanning calorimetry using a Cu-K _a line, is determined to have no crystallinity. Some alloys have a width of 50
It was also cast as a mm ribbon. At least 80 for each alloy
% Were glassy, most of them were 90% or more glassy, and often alloys were 100% glassy. The ribbons of these glassy metal alloys were tough, shiny, hard and ductile.

A commercially available vibrating sample magnetometer was used to measure the saturation magnetic moment of these alloys. As-cast ribbons from a given alloy are cut into a few small squares (about 2m x 2mm) with their faces parallel to the maximum applied magnetic field of about 755kA / m and almost normal to those faces. Were randomly oriented. The saturated magnetic induction, B _s , was then calculated using the measured mass density. The densities of many of these alloys were measured by standard methods according to Archimedes' principle.

Core loss was measured on a closed magnetic path type annular sample. An annular sample was prepared by winding a continuous ribbon of glassy metal alloy around a ceramic bobbin (outer diameter of about 40 mm) with an average magnetic path length of about 0.13 m. Each annular sample is about 0.002-0.01kg
Included a ribbon. All toruses were annealed prior to loss measurement. The annealing temperature is about 573-623K,
Annealing time is about 900-3600s, about 400-1600A / m
An external magnetic field of this strength was applied to the torus during the annealing cycle.

The torus was driven by discharging it into a low inductance capacitor bank with a set of insulated primary windings for about 3 to about 10 turns. The current in the primary winding was measured using a commercially available current probe. One secondary winding has a magnetization rate (dB
/ dt) was applied a voltage proportional to. The voltage and current waveforms were digitized and recorded on a digital oscilloscope at 20 ns per point. Core loss, applied magnetic field and maximum flux fluctuations were then calculated by processing these accumulated waveforms. A separate set of about 5-10 turns was used to apply the pulse resetting field before magnetizing the torus, producing maximum flux swing from negative remanence to positive saturation.

To illustrate these magnetisms measured for the alloys of the present invention, the values of core loss and average magnetic field are each given as a function of the magnetization rate obtained with the six alloys of Table III.
And shown in FIG.

A potential source of error for the above measurements is due to the pickup of (dB / dt) in air, which is also engulfed by the secondary winding. In order to minimize this effect, some annular magnetic cores including one secondary winding in which only the magnetic core material was wound were manufactured. The data in Figures 2-4 were obtained using this structure.

Although the present invention has been described in considerable detail above, it is obvious to those skilled in the art that it is not necessary to stick to these details and further changes and modifications can be made, and these are all defined by the claims. It will be understood that it is included in the range of.

Claims (9)

[Claims] 1. At least 80% is glassy and has the formula Fe _a C
o _b B _c Si _d C _e (where ae is atomic% and a is 72-84)
, B is 2-8, c is 11-16, and d is 1
-4 and e is 0.5-2), with a saturation magnetic induction of 1.55-1.75 T, magnetic anisotropy energy of 300-400 J / m ³ , and a negative remanence to a positive value. Annealed magnetic metallic glassy alloy with DC swing to saturation 2.9-3.2T. 2. The magnetic alloy according to claim 1, wherein d is 1-2. 3. The magnetic alloy according to claim 1, wherein c is 11-14. 4. A composition formula Fe ₇₅ Co ₆ B ₁₄ Si ₃ C ₂ , Fe ₇₇ Co ₆ B ₁₂ Si ₃ C ₂ ,
Fe ₇₈ Co ₆ B ₁₂ Si ₃ C ₁ , Fe ₇₉ Co ₂ B ₁₄ Si ₃ C ₂ , Fe ₇₆ Co ₆ B ₁₅ Si ₁ C ₂ , Fe
₇₈ Co ₆ B ₁₂ Si ₁ C ₃ , Fe ₇₇ Co ₇ B ₁₂ Si ₂ C ₂ , Fe ₈₀ Co ₆ B ₁₁ Si ₁ C ₂ , Fe ₇₈
Co ₆ B ₁₂ Si ₂ C ₂ , Fe ₇₈ Co ₈ B ₁₁ Si ₃ , Fe ₇₉ Co ₆ B ₁₂ Si ₂ C ₁ and Fe
The magnetic alloy according to any one of claims 1 to _3, which has ₇₉ Co ₆ B ₁₂ Si ₃ . 5. Fe _a Co _b at least 80% glassy
_{Mn f B c Si d C e} (a-e in the formula are atomic%, a is 72-84
, B is 2-8, c is 11-16, and d is 1
-4, e is 0.5-2, and f is 1 or less)
Saturated magnetic induction 1.55-1.75 having a composition described by
T, magnetic anisotropy energy 300-400 J / m ³ , and DC reversal 2.9-3.2T from negative remanence to positive saturation,
Annealed magnetic metallic glassy alloy. 6. The magnetic alloy according to claim 5, wherein d is 1-2. 7. The magnetic alloy according to claim 5, wherein c is 11-14. 8. A magnetic core suitable for use at a magnetization speed of 1 MT / s or more, wherein the magnetic core is at least 80 as a magnetic core material.
% Is glassy, and the formula Fe _a Co _b B _c Si _d C _e (a-e in the formula
Is atomic%, a is 72-84, b is 2-8, c is 11-16, d is 1-4, and e is 0.5-.
2) and a saturated magnetic induction
1.55-1.75T, DC shaking 2.9-3.2T of magnetic anisotropy energy 300-400J / m ^3, and from the negative remanence to positive saturation
A magnetic core having an annealed magnetic metallic glassy alloy with. 9. A magnetic core suitable for use at a magnetization speed of 1 MT / s or more, wherein the magnetic core is at least 80 as a magnetic core material.
% Is glassy, and Fe _a Co _b Mn _f B _c Si _d C _e (a-e in the formula
Is atomic%, a is 72-84, b is 2-8, c is 11-16, d is 1-4, and e is 0.5-.
2 and f is less than or equal to 1), saturated magnetic induction 1.55-1.75 T, magnetic anisotropy energy 300-400 J / m ³ , and negative remanence to positive saturation. A magnetic core comprising an annealed magnetic metallic glassy alloy having a DC swing of 2.9-3.2T.