DE1758152B1 - USE OF A NICKEL IRON BASE ALLOY FOR AGAINST STATES WITH HIGH INITIAL PERMEABILITY AT TEMPERATURES BELOW 180 DEGREES C. - Google Patents

Description

The invention relates to the use of a soft magnetic alloy based on nickel-iron for objects which must have a high initial permeability at temperatures below -180 ° C.

Suitable alloys with favorable magnetic properties at low temperatures are required today in numerous areas of low temperature physics and technology. For example, they are in great demand for deep-frozen magnetic shields as well as for precision current transformers and transformers that work at the temperature of liquid nitrogen or helium. For such applications, the soft magnetic material must in particular have the highest possible initial permeability in the temperature range below -180 ° C. In the case of magnetic shields, a high initial permeability results in a high shielding effect against the mostly weak magnetic stray fields, and with current transformers the measurement error decreases with increasing permeability of the converter material, while with low-current transformers a high inductance can be achieved with a low number of turns if the Transmitter material has a high permeability even at low field strengths.

The invention has now surprisingly shown that a known ductile nickel-iron-based alloy can be used to produce objects which must have an initial permeability of more than 40,000 at temperatures below -180 ° C Composition lies within a range in the multicomponent system nickel- (iron + copper + manganese) -molybdenum, which - as shown in FIG. 1 - is limited by the polygon

A (73.3% Ni; 26.7% (Fe + Cu + Mn); 0% Mo) -

B (80.5% Ni; 16.9% (Fe + Cu + Mn); 2.6% Mo) -

C (80.5% Ni; 14.9% (Fe + Cu + Mn); 4.6% Mo) -

D (72.2% Ni; 26.3% (Fe + Cu + Mn); 1.5% Mo) -

E (72.2% Ni; 27.8% (Fe + Cu + Mn); 0% Mo) - A,

especially from the polygon

F (75.4% Ni; 23.2% (Fe + Cu + Mn); 1.4% Mo) -

G (78.0% Ni; 19.7% (Fe + Cu + Mn); 2.3% Mo) -

H (78.0% Ni; 18.5% (Fe + Cu + Mn); 3.5% Mo) -

J (75.4% Ni; 22.1% (Fe + Cu + Mn); 2.5% Mo) - F,

with the proviso that the manganese content is 0.2 to 1.0% and the copper content assigned to the nickel content lies within the range which - as shown in FIG. 2 - is limited by the polygon

K (72.2% Ni; 19.4% (Fe + Mn + Mo); 8.4% Cu) -

L (77.5% Ni; 22.5% (Fe + Mn + Mo); 0% Cu) -

M (80.5% Ni; 19.5% (Fe + Mn + Mo); 0% Cu) -

N (80.5% Ni; 18.1% (Fe + Mn + Mo); 1.4% Cu) -

O (73.0% Ni; 14.5% (Fe + Mn + Mo); 12.5% Cu) -

P (72.2% Ni; 15.3% (Fe + Mn + Mo); 12.5% Cu) - K,

especially from the polygon

Q (75.4% Ni; 21.3% (Fe + Mn + Mo); 3.3% Cu) -

R (78.0% Ni; 18.7% (Fe + Mn + Mo); 3.3% Cu) -

S (78.0% Ni; 17.0% (Fe + Mn + Mo); 5.0% Cu) -

T (75.4% Ni; 19.6% (Fe + Mn + Mo); 5.0% Cu) - Q,

To achieve the desired high values of the initial permeability at temperatures below -180 ° C, this alloy is annealed in a known manner for several hours, in particular 2 to 8 hours, at 1050 to 1250 ° C in a non-oxidizing annealing atmosphere and then a subjected to several hours, in particular a 1- to 5-hour final heat treatment at a temperature between the Curie temperature and 550 ° C.

The invention is explained in more detail below on the basis of exemplary embodiments.

In a vacuum furnace, 20 alloys based on nickel-iron were produced, the chemical composition of which is given in percent by weight in Table 1 and is entered with the same numbering in the nickel (iron + copper + manganese) -molybdenum alloy diagram (FIG. 3) .

Table 1

Magnetic alloys based on nickel-iron

Composition in percent by weight

continuation

Table 2

Thermal termination and permeability of the magnet alloys listed in Table 1

After forging, the fused blocks were hot-rolled to a thickness of 2.5 mm, then pickled, annealed at 1050 ° C. and cold-rolled to the final thickness of 0.1 mm with the addition of a further intermediate anneal. From the 0.1 mm thick and 10 mm wide tape produced in this way, toroidal cores with an inner diameter of 25 mm and an outer diameter of 35 mm were produced. These cores were first annealed for 5 hours at 1200 ° C in pure hydrogen, then cooled as required, then - as can be seen from Table 2 - subjected to a 2-hour heat treatment at 440 to 550 ° C in hydrogen and then quickly brought to room temperature.

The permeability (µ [deep] 0.5) of the toroidal cores was determined using a Maxwell bridge at a field strength of 0.5 mOe and a frequency of 70 Hz: it corresponds practically to the initial permeability. To measure the temperature dependence of the permeability in the range between -268.9 ° C and + 20 ° C, the cores were placed in suitable protective troughs made of copper, in a cryostat at the temperature of liquid helium (-268.9 ° C) or des liquid nitrogen (-195.8 ° C) cooled and then heated. The temperature was measured below -200 ° C by means of a gold iron chromel thermocouple and above -200 ° C by means of a thermocopper thermoconstantan thermocouple, which was inserted into the protective trough.

The test results shown in Table 2 and the permeability values shown in FIGS. 4 to 7 as a function of temperature show that the nickel-iron-based magnet alloys to be used according to the invention have a permeability several times higher in the range of low temperatures (µ [ deep] 0.5) have previously known soft magnetic materials whose maximum permeability is in the range of room temperature, as the dashed curve in FIG. 4 shows.

The measured values according to Table 2 and the permeability-temperature curves in FIGS. 4 to 9 also show how the position and shape of the maximum permeability depend on the alloy composition and the heat treatment. As a working rule for the selection of alloys to be used according to the invention with easy magnetizability at low temperatures, it has been found that the permeability maximum is generally shifted to lower temperatures due to a lower heat treatment temperature and also due to longer annealing times. In order to avoid the perminvar effect, however, it is forbidden to carry out the heat treatment below the Curie temperature.

Depending on the alloy composition, it was found, in particular, that with increasing molybdenum content for a given nickel content, the heat treatment temperature should be selected lower, and that for alloys located along the line FG with increasing nickel content, a higher heat treatment temperature is required in order to achieve that from these alloys manufactured objects have a high initial permeability at low temperatures.

The maximum permeability of the alloys located outside the delimited area A-B-C-D-E-A (Nos. 9, 11, 16 and 17) cannot be shifted into the temperature range of liquid nitrogen and liquid helium, even by heat treatment at low temperature.

The advantage achieved with the invention is, in particular, that a ductile alloy can be used which has an initial permeability of more than 40,000. The rules that have been found also allow the alloy to be used and its thermal treatment to be selected in such a way that an initial permeability of a predetermined size results within a certain range.

The use according to the invention of a nickel-iron-based alloy with high permeability at temperatures below -180 ° C. is particularly necessary for deep-frozen magnetic shields, current transformers and transformers and for relays, magnetic switches, memories and amplifiers.

Claims (1)

Use of an alloy based on nickel-iron, the composition of which lies within a range in the multi-component system nickel- (iron + copper + manganese) -molybdenum, which is limited by the polygon A (73.3% Ni; 26.7% (Fe + Cu + Mn); 0% Mo) - B (80.5% Ni; 16.9% (Fe + Cu + Mn); 2.6% Mo) - C (80.5% Ni; 14.9% (Fe + Cu + Mn); 4.6% Mo) - D (72.2% Ni; 26.3% (Fe + Cu + Mn); 1.5% Mo) - E (72.2% Ni; 27.8% (Fe + Cu + Mn); 0% Mo) - A, especially from the polygon F (75.4% Ni; 23.2% (Fe + Cu + Mn); 1.4% Mo) - G (78.0% Ni; 19.7% (Fe + Cu + Mn); 2.3% Mo) - H (78.0% Ni; 18.5% (Fe + Cu + Mn); 3.5% Mo) - J (75.4% Ni; 22.1% (Fe + Cu + Mn); 2.5% Mo) - F, wherein the manganese content is 0.2 to 1.0% and the copper content assigned to the nickel content lies within the range which is limited by the polygon K (72.2% Ni; 19.4% (Fe + Mn + Mo); 8.4% Cu) - L (77.5% Ni; 22.5% (Fe + Mn + Mo); 0% Cu) - M (80.5% Ni; 19.5% (Fe + Mn + Mo); 0% Cu) - N (80.5% Ni; 18.1% (Fe + Mn + Mo); 1.4% Cu) - O (73.0% Ni; 14.5% (Fe + Mn + Mo); 12.5% Cu) - P (72.2% Ni; 15.3% (Fe + Mn + Mo); 12.5% Cu) - K, especially from the polygon Q (75.4% Ni; 21.3% (Fe + Mn + Mo); 3.3% Cu) - R (78.0% Ni; 18.7% (Fe + Mn + Mo); 3.3% Cu) - S (78.0% Ni; 17.0% (Fe + Mn + Mo); 5.0% Cu) - T (75.4% Ni; 19.6% (Fe + Mn + Mo); 5.0% Cu) - Q, which are initially annealed in a known manner for several hours, in particular 2 to 8 hours at 1050 to 1250 ° C in a non-oxidizing annealing atmosphere and then a multi-hour, in particular 1 to 5-hour heat treatment at a temperature between the Curie temperature and 550 ° C has been subjected to located temperature, as a material for objects that must have an initial permeability of more than 40,000 at temperatures below -180 ° C.