DE2709626C3 - Process for reducing the magnetic reversal losses in thin strips made of soft magnetic amorphous metal alloys - Google Patents

Description

with the proviso that the annealing temperature is 280-350 ⁰ C, and takes place in a controlled cooling to a temperature of 200 "C

5. Application of a method according to claim 4 with the proviso that the controlled cooling with a cooling rate of about 100 up to 250 "C per hour

The invention relates to a method for reducing the magnetic reversal losses in thin strips made of soft magnetic amorphous metal alloys, whereby a tape or a wound from a tape Magnetic core initially annealed at a temperature above the Curie temperature and below the crystallization temperature for mechanical relaxation then allowed to cool in a controlled manner to a temperature below the Curie temperature.

As is known, amorphous metal alloys can be produced by using a corresponding The melt cools so quickly that it solidifies without crystallization. The alloys can thereby are obtained in the form of thin ribbons as soon as they are formed, some of which are thick, for example hundredth! mm and the width of which can be a few mm (see. For example DE-OS 25 00 846 and DE-OS 26C6 581).

The amorphous alloys can be identified from crystalline alloys by X-ray diffraction measurements differentiate. In contrast to crystalline materials, which have characteristic, sharp diffraction lines paste, changes in amorphous metal alloys the intensity in the X-ray diffraction image only slowly with (Sem diffraction angle, similar to this also with Liquids or ordinary glass is the case. Depending on the manufacturing conditions, the amorphous alloys can be completely amorphous or a comprise two-phase mixture of the amorphous and the crystalline state. Generally one understands under an "amorphous metal alloy" an alloy, which is at least 50%, preferably at least 80%, amorphous

s For every amorphous metal alloy there is a characteristic temperature, the so-called crystallization temperature. The amorphous alloy is heated at or above this temperature, it changes into the crystalline state. During heat treatments ο below the crystallization temperature, on the other hand, the amorphous state is retained.

The previously known soft magnetic amorphous metal alloys have the composition MjXi-j, where M is at least one of the metals iron, Cobalt and nickel, and X at least one of the so-called glass-forming elements boron, carbon. Silicon and phosphorus mean and y is between about 0.60 and 035 In addition to the metals M, the amorphous alloys can also be used further? Metals, in particular titanium, zirconium, vanadium, niobium, tantalum, Chromium, molybdenum, tungsten, manganese, palladium, platinum, Contain copper, silver or gold, while in addition to the glass-forming elements X or optionally also instead of these the elements aluminum,

Gallium, indium, germanium, tin, arsenic, antimony, Bismuth or beryllium may be present (cf. DE-OS 2546 676, DE-OS 25 53003, PE-OS 2605615

and DE-OS 26 28 3C2).

For a technical application are amorphous

soft magnetic alloys with corresponding magnetic properties of great interest, since as already mentioned, they can be produced directly in the form of thin ribbons. In the case of the Technique usual crystalline soft magnetic Me Talal alloys, on the other hand, are thinner for production Strips require a large number of rolling steps with numerous intermediate anneals.

It is known that the magnetic properties of soft magnetic amorphous metal alloys influence by heat treatment> at a temperature below the crystallization temperature permit. In the case of a number of cobalt-containing soft magnetic amorphous alloys, for example, a corresponding heat treatment under helium results in one A magnetic field running parallel to the longitudinal direction of the treated strip, a so-called longitudinal field, which is sufficient to technically correct the alloy saturate, to an increased remanence and to a reduced coercive field strength. A corresponding

so heat treatment in a perpendicular to the longitudinal direction of the treated strip parallel to the strip plane running magnetic field, a so-called transverse field, leads to a body whose magnetization is approximately linear in the vicinity of the field strength value zero changes with the field strength (DE-OS 25 46 676).

With more detailed investigations on ribbons and toroidal cores from the amorphous soft magnetic alloy

it was found that an annealing treatment at a temperature between the Curie temperature and the Crystallization temperature leads to a mechanical relaxation of the alloy and that the magnetic Properties of the alloy treated accordingly depend to a considerable extent on the conditions under which the alloy in connection with the Annealing treatment to a temperature below that

Curie temperature is cooled. The annealing treatments were known in these examinations carried out under nitrogen and under vacuum Globes and subsequent controlled cooling in a longitudinal magnetic field became the remanence and the remanence ratio, as with crystalline ones soft magnetic materials common, compared to the unannealed cores increased by annealing and Subsequent cooling in a magnetic transverse field was, however, similar to that of crystalline soft magnetic cores - the remanence and the remanence ratio compared to the unannealed cores are reduced, so that the corresponding inductivity-field strength curves are flatter than that of the unannealed nuclei and, due to their flat course, show what is known as an F-characteristic. at The annealing treatment under nitrogen also increased the coercivity and the magnetic reversal losses compared to the unannealed cores while the corresponding effects were somewhat less pronounced when annealing under vacuum {vgL IEEE Transactions on Magnetics, VoL Mag - !!, No. 6, 1975, pp. 1644-1649, and Coherence on Rapidly Quenched Metals, Vol 1, Boston 1975, pages 467 ff.).

By annealing in nitrogen in these known investigations, with one exception, the magnetic reversal losses could only be reduced to values that are about twice as high as the magnetic reversal losses in strips made of comparable soft magnetic alloy rings. For example, in an alternating magnetic field with a maximum induction of 0.1 T and a frequency of 10 kHz, in the best case loss values of 18 mW / cm ³ (-2.4 W / kg) were achieved, while the corresponding losses were achieved with bands made of low-loss bands commercial crystalline soft magnetic alloys are only about 1 W / kg. Only in the one mentioned case was a loss value of about 133 W / kg achieved in the mentioned alternating magnetic field no more flat F-loop results For a number of technical applications that were previously reserved for crystalline soft magnetic alloys, a hysteresis curve in the form of an F-loop with at the same time the lowest possible magnetic reversal losses is desired

The invention is based on the object, with a method of the type mentioned at the beginning, the magnetic reversal losses of soft magnetic amorphous To reduce metal alloys even further and, at the same time, to achieve the flatest possible F-characteristic of the To achieve hysteresis curve.

According to the invention, this is achieved by annealing and cooling in air or other oxidizing media.

The annealing and controlled cooling in air leads to surprisingly low magnetic reversal losses and also surprisingly low remanences and remanence ratios. The effects of heat treatment in air to which this effect can be attributed has not yet been fully clarified will. However, it appears that there is a tension in the amorphous alloy of the Bancicj a role due to its thin oxide layer on the belt surface. A corresponding effect can also can be achieved by other oxidizing media.

As particularly advantageous in view of the cheap

achievable values for remanence, remanence ratio and magnetization losses turned out to be a

Tape or one wound from a tape Magnetic core made from an alloy of the composition Feo, 4oNio. "Pai"

to glow for at least about 0.5 to 2 hours at a temperature between about 280 and 350 ⁰ C and then allowed to cool in a controlled manner to a temperature of 200 ⁰ C or less.

At temperatures between 280 and 350 ^° C., complete mechanical relaxation of the strips can be achieved with the specified minimum annealing times of about 0.5 to 2 hours. The longer minimum glow times are with the lower ones, the shorter with to use the higher temperatures. The temperatures are also sufficiently übf ler Cunetemperatur the alloy of about 230 ° C ιΐπ-Ί below the crystallization temperature of 360 ⁰ C for the controlled cooling has at said alloy also a cooling rate of about 100 to 250 ° C oro hour as particularly advantageous in terms of of the magnetic characteristics achieved.

In the case of annealing and cooling in air, it is also of considerable influence whether the cooling takes place without a magnet field or in a magnetic field Will occur without Magnetic field annealed and cooled so you get a very small remanence ratio and very low one Losses. This can result in a further reduction in losses with a somewhat increased remanence ratio be achieved that the tape made of the amorphous alloy or a core wound from the: tape during the controlled cooling in a magnetic field running in the longitudinal direction of the strip is magnetized approximately to saturation.

The cooling in a longitudinal field is therefore particularly favorable if the lowest possible loss values are to be achieved. By magnetizing one Band or corresponding core during cooling almost to saturation in one magnetic transverse field, one can achieve magnetic characteristics that are between the values when cooling down in the Longitudinal field and the widths achieved when cooling without a field. In contrast, the magnetic reversal losses are slightly higher than with the other magnetization ration types.

The magnetization almost to saturation must in any case during the controlled cooling from a temperature above the Curie temperature to a temperature below the Curie temperature take place. For purely practical reasons, however, the corresponding magnetic field is usually already used Apply during the glow for mechanical relaxation. Under magnetization almost up to Saturation should have a magnetization of more than 60% of saturation. Preferably will approach saturation as close as possible with the magnetization.

With the aid of a figure, the induction-strength curves of toroidal tape cores treated according to the invention shows, and based on examples, the Invention still closer; · to be explained.

From an approximately 2 mm wide and 0.05 mm thick strip made of a soft magnetic amorphous alloy

tion of the composition

Feo.4oNio, 4oPo, uBo.o6

Several toroidal tape cores with an outer diameter of 20 mm and an inner diameter of 10 mm were produced. The individual tape windings were insulated from one another by means of magnesium oxide powder. The wound cores, each consisting of 70 to 80 turns, were placed in suitable protective troughs made of aluminum. The cores were then subjected to the protection troughs eirer relief annealing for 30 minutes at a temperature of about 325 ° C, which is between the Curie temperature of the alloy from about 230 ° C and the Kristaliisationstemperatur of about 36O ⁰ C. Following the annealing, the nuclei at a cooling rate of about 200 ° C per .Stunde to a temperature below the Curie temperature, were allowed to cool, controlled in this case to about 100 ⁰ C. The further cooling to ambient temperature took place in an uncontrolled manner.

The annealing and the subsequent controlled cooling took place in air under different conditions Conditions. A part of the cores was in one in the circumferential direction of the individual core, so in one A magnetic field running parallel to the longitudinal direction of the wound tape, a so-called longitudinal field, annealed and cooled, which was generated by means of a winding applied to the core and with a field strength of 16 A / cm magnetized the amorphous alloy close to 2U of its saturation value. A other part of the cores was in a perpendicular to the longitudinal direction of the tape, parallel to the winding axis of the Kernes directed magnetic field, a so-called

> o Cross-field, annealed and cooled. For this purpose, the cores were placed in the field of a 10 cm long bar magnet made of AlNiCo 26/6 with a cross-sectional area of 4x4 cm ² . Another part of the cores was annealed and cooled without a magnetic field.

For the purposes of comparison, other cores were subjected to a corresponding treatment, but in which the annealing and the subsequent controlled cooling took place under hydrogen.

On the cores treated in this way, induction field strength curves were then measured at 50 Hz with a vector meter. From these curves, the relative Wechselfeldpermeabilitäten // "were, the permeability that is at a magnetic field strength of 4 mA / cm, and u _{m. x} , i.e. the maximum permeability, is determined. In addition, the coercive field strength Hc and the remanence B _{r were} determined statically. From the latter and the saturation induction B "which was in the alloy used as 0.PT, the ratio of the remanence was B _r to the saturation induction _Β Λ the so-called remanence ratio B / B, determines that a good measure of the slope of the hysteresis curve and thus for In addition, the magnetic reversal losses Pj> in an alternating magnetic field with a maximum induction of 0.1 T and a frequency of 10 kHz and in an alternating magnetic field with a maximum induction of 0.2 T and a frequency of 20 kHz measured.

The wet results are the same as those on an unannealed Toroidal tape core made of the same amorphous alloy values measured in Table 1 compiled.

Tabel

Annealing conditions 13 100 μ max H ₁ B / B, Br /W0.1 T; AV / 0.2 T; 1 600 10 kHz) 2OkHz) 3 650 mA / cm T W / kg W / kg Air, longitudinal field 42 500 25 300 17.9 0.10 0.080 0.95 10.7 Air without a field 5,500 2,300 60.0 0.013 0.010 1.1 13.2 Air, cross-country 5000 5,400 29.0 0.034 0.027 2.0 16.0 Hi, longitudinal field 281,000 6.9 0.92 0.736 3.7 34.0 H ₂ , without field 56,000 22.0 0.470 0.376 3.5 31.0 Hi, cross-country 24 500 14.0 0.144 0.115 2.4 22.5

Not annealed

150

25 900

65.0

0.419 0.355

14.5

91.0

In the figure, measured at 50 Hz induction field strength curves are annealed in air and cooled toroidal cores shown on the abscissa is a logarithmic scale, the effective magnetic field strength has in A / cm, on the ordinate also in logarithmic scale the respective maximum amplitude B of the induction plotted in T, eo Curve a was measured on a core annealed and cooled in a longitudinal field, curve b on a core annealed and cooled without a magnetic field, and curve c on a core annealed and cooled in a transverse field. The curves show an approximately linear increase in induction with field strength. They run very flat and thus show a pronounced F-characteristic.

When comparing the values compiled in Table 1, it is particularly noticeable that in the case of the values in air annealed and cooled cores the remanence and the remanence ratio compared to the unannealed cores The core and the cores annealed and cooled under hydrogen are extremely small. The reduction in both values is particularly noteworthy in the case of the core subjected to the annealing treatment under Loft in the longitudinal field compared to the widths of the unannealed core. Usually, an annealing with controlled cooling in the Longitudinal field increases the remanence and the remanence ratio, as z. B. also with the under hydrogen im Longitudinal field annealed and cooled core is the case

Furthermore, Table 1 shows that by the annealing

and the subsequent controlled cooling in air the magnetic reversal losses compared to those of the unannealed core can be reduced to an extent that is far greater than that obtained during the annealing treatment Hydrogen induced reduction goes beyond. Particularly The losses are low for those annealed and cooled in air in the longitudinal field and without field Cores. For cores made of 0.05 mm thick strips made from commercially available crystalline r'ermalloy alloys (about 70.5% by weight nickel, 4.5% by weight copper. 3 to 3.5% by weight molybdenum, remainder iron) are at 0.2 T and 20 kHz core loss values of 10 to 12 W / kg are achieved. The in air in the longitudinal field or without Cores made of the amorphous alloy that have been annealed and cooled by a magnetic field are therefore the commercially available ones Permalloy alloys are completely equivalent in terms of loss values.

The permeability u « is considerably increased by the annealing and cooling at Lir't compared to the unannealed core, although less strongly ac- cording to the annealing under hydrogen. In contrast, the maximum permeability μ _η ,,, compared to the unannealed core, decreases slightly in the longitudinal field during annealing and cooling in air and by a factor of 5 to 10 during annealing and cooling in air without a field or in the transverse field. The reduction in the coercive field strength is less pronounced during annealing and cooling in air than during annealing and cooling under hydrogen. The magnetic reversal losses at 0.1 T and 10 kHz of the cores annealed and cooled in air are at the same time very low remanence and low remanence ratio also considerably below those of the already mentioned, known cores annealed and cooled under nitrogen.

Corresponding reductions in magnetic reversal losses with a flat F characteristic at the same time The hysteresis curve can also be used for other soft magnetic ones with the aid of the method according to the invention amorphous alloys. Particularly beneficial effects are to be expected with alloys, whose magnetostriction is not zero

To investigate the influence of the cooling rate two toroidal cores of the type already explained after a JUminütigen fcntspannungsglühung at about 325 ° C in a longitudinal magnetic field at a cooling rate of 1200 ⁰ C per hour, which, however, only difficult to achieve for industrial use have been or control lets or allowed to cool at a cooling rate of! 0 ° C per hour. Compared to the cooling in the longitudinal field with a cooling rate of 200 ° C per hour

. The remanence and the remanence ratio were reduced even further to around 30 and 45% respectively and thus an even flatter hysteresis curve was achieved, but the relative permeabilities μ * and μ-ηα decreased at the cooling rate of

ι 12 (KTC per hour to about 50 or 30%, and at the cooling rate of 1O ⁰ C per hour to about 6 or 7% of the achieved during the cooling of 200 ° C per hour values from. The core losses increased upon cooling around 1200 ⁰ C per hour by about 30% and b <'i cooling with i0 ° C per hour, even more compared to the losses during the cooling to 200 ⁰ C per hour. the range of the average cooling rate of about 100 to 25O ⁰ C per hour is therefore nipririupn because of the relatively high permeability that can be achieved

Magnetization reversal losses with, at the same time, a very flat course of the hysteresis curves for cooling particularly favorable in the longitudinal field in air.

Measurement results on toroidal tape cores from seven different other soft magnetic amorphous ones Alloys are listed in Table 2 below.

In column 1, the alloy as well as the associated Curie temperature 7 ~ _c and crystallization temperature Tk are given. Column 7 contains the saturation induction β, in Tesla. The remaining columns correspond to the correspondingly labeled columns in Table 1, only in the case of the first two alloys in Table 2 are values for μ * and μ, ™, not dynamically, but statically measured values given. The production of the toroidal tape cores and the measurements were carried out analogously to the examples given in Table 1. The annealing temperature was in each case about 400 ° C. The first three alloys listed in Table 2 were each annealed for about 1 hour, the remaining four for about 4 hours each. The cooling rate was about 200 ° C per hour.

A comparison of the annealing in air with the also indicated annealing under hydrogen shows that the air annealing significantly reduces the magnetic reversal losses Pfc and also results in reduced B / B _r values, i.e. flatter hysteresis loops.

Table 2

alloy Annealing conditions 3300 I * max raA / era B / B _s B ₅
T / V / 0.2 T;
2OkIIz)
W / kg r _r = 375 C, 7i = 485 C Air without a field
H ₂ , longitudinal field 9000 420,000 68
14th 0.35
0.9 1.2
1.2 14th
45 Fe _{0, 0} 65Nio.i5Mo O ₂ B _0-18
r _r «400 C, 7; = 450 C Air without a field
H ₂ , longitudinal field 370,000 141
20th 0.11
0.9 1.3
1.3 11
28 Feo.8iSio.035Bo.135Co.02
T _c = 370 C, T _k = 480 C Air without a field
H ₂ , longitudinal field 15,000
20,000
60,000 140,000 172
40 0.10
0.85 1.6
1.6 7th
25th 7: = 315 C, Γ * = 420 C Air, longitudinal field
Air without a field
H ₂ , longitudinal field 100,000
60,000
250,000 13.5
12th
6th 0.4
0.3
0.8 0.84
0.84
0.84 8.5
> 25

9 Oil conditions 27 09 626 H ₁
mA / cm 10 T S. / ',, (0.2 T:
20 kHz)
W / kg , 1 ,, air, no field
Hi, longitudinal field 1.2
5.5 0.80
0.80 9
> 25 0.14 air, longitudinal field
Air without a field
! In Liingsfeld I'm ,, χ 10.7
12th
5.5 / MB. 0.80
0.80
0.80 10.5
9.5
> 25 0.12 air, longitudinal field
Air without a field
H ₂ , longitudinal field 80,000 280,000 11
'3
6.5 0.45
0.75 0.80 9.5
0.80 8.5 1
0.80> 25 I. 15,000
13000
80,000 120,000
80,000
280,000 0.5
0.4
0.75 20,000
50,000 64,000
250,000 0.35
0.20
0.80 continuation alloy r _r = 300 C, r _t = 445 C 7; = 290 C, Γ * = 460 C 7 ^ = 270 C.7; = 465 C
The after Hem BrfinHi

Applied tapes or tape cores are particularly suitable For transformers with so-called medium-frequency power supplies for a frequency of, for example, 20 kHz. In addition to the low magnetic reversal losses, which are a prerequisite for such an application occur in a number of Switching principles for such power supplies also essentially rely on a flat F-characteristic of the hysteresis curve the transformer cores. Compared to power supplies with a frequency of 50 Hz Medium-frequency power supplies have the advantage that they can be trained, and often at 50 Hz there is no annoying hum. Medium-frequency power supplies are, for example, often used in data processing systems, Office computers, cash registers and teleprinters are used. Also are suitable strips or strip cores made of amorphous soft magnetic alloys treated according to the invention, too for applications with unipolar modulation, where the hysteresis curve is also flat arrives.

1 sheet of drawings

Claims (4)

Patent claims: 1. Method for reducing the magnetic reversal losses in thin strips made of soft magnetic amorphous metal alloys, wherein a strip or a magnetic core wound from a tape initially at a temperature above Curie temperature and below the crystallization temperature of the alloy for mechanical relaxation annealed and then controlled for a Temperature is allowed to cool below the Curie temperature, characterized in that annealing and cooling in air or other oxidizing media. 2. The method according to claim 1, characterized in that the tape or the magnetic core is magnetized almost to saturation during cooling. 3. The method according to claim 2, characterized in that the tape or the magnetic core in iiß a magnetic field extending in the longitudinal direction of the tape is magnetized. 4. Application of a method according to one of claims 1 to 3 on an amorphous alloy with the composition