US3657025A

US3657025A - Nickel-iron base magnetic material with high initial permeability at low temperatures

Info

Publication number: US3657025A
Application number: US807652A
Authority: US
Inventors: Friedrich Pfeifer
Original assignee: Vacuumschmelze GmbH and Co KG
Current assignee: Vacuumschmelze GmbH and Co KG
Priority date: 1968-04-11
Filing date: 1969-03-17
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18
Also published as: SE364526B; NL6905540A; AT287328B; GB1209437A; DE1758152B1; FR1600120A

Abstract

A nickel-iron base alloy is described to which controlled amounts of copper, manganese and molybdenum may be added. By proper selection of composition and heat treatment high initial permeabilities are obtained at cryogenic temperatures.

Description

nited States Patent 7 1151 3,07,02

Pieifer [4 1 Apr. 1, 1972 1541 NICKEL-IRON BASE MAGNETIC MATERIAL WITH HIGH INITIAL 1 Ref r nces Cited LOW UNITED STATES PATENTS 3,546,031 12/1970 Pfeifer et a1. ..l48/121 [72] Inventor: Friedrich Pfeifer, Oberissigheim, Kreis, 3,556,876 1/1971 Pfeifer et all ..148/ 121 Hanau, Germany 1,552,769 911925 Smith et a1 .75/170 1,768,443 6 1930 Elmen ..75/170 [731 Asslgnee= Vacuumschme' Hana, Germany 3,269,834 8/1966 Lykensetal ..75/170 22 Filed: Mar. 17, 1969 3,472,708 10/1969 56161161616161. .75/170 [2 App 8071652 Primary Examiner-Richard 0. Dean Attorney-F. Shapoe and R. T. Randig Foreign Application Priority Data 57] ABSTRACT 1968 Germany 58 152'l A nickel-iron base alloy is described to which controlled amounts of copper, manganese and molybdenum may be 52 us. (:1 ..148/31.55, /170, 148/120, added By proper Selection ofcomposition and heat treatment I t Cl high initial permeabilities are obtained at cryogenic temperan tu [58] Field 618661611 ..75/l70;l48/31.55,3l.57,100,- res 148/104, 120, 121 6 Claims, 9 Drawing Figures 10 COMMERCIAL 9 Ni-Fe-Mo ALLOY I I '5 520C E5 Lu 2 1: 11.1 o.

I i ALLOY 3 Z -20o 0 TEMPERATURE (C) PATENTED PR 18 m2 SHEET 10F 2 PATENTEDAPR 18 m2 SHEET 2 BF 2 O U. o.

ALLOY 9 ALLOY a -2bo -|c' o c' TEMPERATURE (c) FIG. 5.

NICKEL-IRON BASE MAGNETIC MATERIAL WITH HIGH INITIAL PERMEABILITY AT LOW TEMPERATURES BACKGROUND OF THE INVENTION current instrument transformers and transmitters which operate at cryogenic temperatures such as obtained in liquid nitrogen or helium. For this type of application, the magnetically soft material must have as high as possible an initial permeability in the range of low temperatures. In magnetic shielding, the high initial permeability is a desirable condition for highly effective shielding against extremely weak extraneous magnetic fields. Moreover, for the current transformers, the indication or measuring error becomes smaller with increasing permeability of the transformer material, while in case of low current transmitters a very high inductivity can be obtained with a small number of turns if the transmitter material has a high permeability at small field intensities.

The high permeability magnetically soft materials which have been heretofore known have not met the above stated requirements. The relative permeability of the magnetically softest alloys with 70 to 80% of nickel when measured at room temperature and at a field intensity of 0.5 mOe (millioersted) is over 100,000 and decreases sharply with lower temperatures to about 10,000 to 15,000 at a temperature of -1 20 C.

In comparison, sendust alloys, that is, the ternary iron base alloys with about 7 to 14% of silicon and with about 2 to 7% of aluminum and which also fall into this category of the technology, reach higher permeability values even slightly below C. but these higher permeability values are achieved in a relatively narrow range of temperature and these values are obtained only for field intensities of about 40 to 200 mOe, that is, for relatively high field intensities. Moreover, the point of maximum permeability depends specifically on the respective silicon and aluminum content of the alloy. For example, an iron-silicon-aluminum alloy with 9.9% of silicon and 5.6% of aluminum has at 1 00 C. a sharply defined maximum with a peak value of permeability of about 64,000 at a field intensity of 100 mOe. For field intensities below 30 mOe the permeability decreases to less than 15,000; moreover, for a field intensity of 1 mOe, the permeability amounts to even less than 10,000 (see Journal of Physics, 1941, vol. IV, pages 569 to 572).

More importantly however the iron-silicon-aluminum alloys of the above specified composition are not suitable for many applications not only on the basis of their unfavorable dependency of their permeability on the field intensity but also because of their technological characteristics, that is, their high degree of brittleness (see C. Heck: Magnetic Materials and Their Technical Applications, 1967, pages 403 and 404) does not permit any of the usual forming or cutting operations (other than grinding) and correspondingly there cannot be produced from these materials any strips, core laminations, or deep-drawn parts.

SUMMARY OF THE INVENTION Therefore the purpose of this invention is to obtain in ductile alloys the best possible magnetically soft properties at low temperatures. The invention is based specifically on the problem of preparing a nickel-iron base magnetic material which has, at temperatures below 180 C., a relative initial permeability of more than 40,000 in weak magnetic fields.

Broadly speaking this is accomplished by selecting the alloying components such that there is present between about 8.9% and 27.6% iron, up to 12.5% copper, up to 4.6% molybdenum, from about 0.2% to about 1.0% manganese and the balance essentially nickel with incidental impurities. The alloy is thereafter processed by hot and cold working and the finish gauge material is thereafter annealed at a temperature within the range between about 1,050" and about l250 C. for a time period of between about 2 hours, and, about 8 hours followed by cooling to room temperature. The annealed material is then subjected to a final heat treatment at a temperature between the Curie temperature and 550 C. for a time period of between about 1 hour and about 5 hours followed by quenching to room temperature.

An object of the present invention is to provide a ductile nickel-iron base alloy having high initial permeability at cryogenic temperatures and at low field intensities.

A specific object of the present invention is to provide a ductile nickel-iron base magnetic material and a heat treatment therefor whereby the material will exhibit an initial permeability of at least 40,000 in a field intensity of 0.5 mOe at a temperature of less than 180 C.

Other objects of the present invention will become apparent to those skilled in the art when read in conjunction with the following description and the drawings in which:

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a ternary diagram illustrating the broad and preferred limits of the alloying components;

FIG. 2 is a ternary diagram illustrating the relation of the copper content with respect to the balance of the alloying components;

FIG. 3 is similar to FIG. 1 but illustrating the actual composition of alloys made and tested as set forth in Table I; and

FIGS. 4 through 9 inclusive illustrate the relationship between initial permeability and temperature for

alloys

3, 8, l9, l5, 9 and 17 respectively of Table I.

DESCRIPTION OF PREFERRED EMBODIMENT The alloy of the present invention is a nickel-iron base alloy to which controlled amounts of at least one of copper, manganese and molybdenum are added. While in broad general terms the alloy contains, in percent by weight, from about 8.9% to about 27.6% iron, up to 12.5% copper, up to 4.6% molybdenum, from about 0.2% to about 1.0% manganese and the balance nickel incidental impurities, the alloying components must be balanced in accordance with the circumscribed areas of FIGS. 1 and 2.

More particularly, according to this invention the actual composition of the magnetic material lies within or in immediate vicinity of a range of multicomponent system nickel- (iron copper manganese)-molybdenum which is defined in FIG. 1 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.

The preferred range of alloying components is defined by 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 restriction that the content of manganese is 0.2 to 1.0% in each instance. Moreover, the content of copper associated with the content of nickel must be within the range which in FIG. 2 is determined by the polygon K (72.2% Ni; 19.4% (Fe-l-Mn-l-Mo); 8.4% Cu) L (77.5% Ni; 22.5% (Fe+Mn-l-Mo); 0% Cu) M (80.5% Ni; 19.5% (Fe+Mn-l-Mo); 0% Cu) N (80.5% Ni; 18.1% (Fe-l-Mni-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. Preferred results are obtained where the copper content is maintained within the polygon O (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)-Qof FIG. 2.

When the alloying components are balanced within the circumscribed areas of FIGS. 1 and 2, the material is annealed during its manufacture in a non-oxidizing atmosphere for several hours, specifically 2 to 8 hours, at 1,050 to 1,250 C. and afterwards it is subjected to final heat treatment for several hours, specifically l to hours, at a temperature in a vacuum fumace there were produced nickel-iron alloys with the chemical composition given in per cent by weight in Table l and indicated by the same numbers in the nickel- (iron copper manganese)-molybdenum alloying diagram in FIG. 3. After forging, the ingots were hot rolled to a thickness of 2.5 mm followed by annealing at l,050 C. Thereafter, the material was cold rolled to a final thickness of 0.1 mm with intermediate annealing where necessary. From the strip 0.1 mm thick and 10 mm wide there were produced wound ring cores of mm inside diameter and mm outside diameter. These cores were then annealed for 5 hours at 1,200 C. in pure hydrogen, cooled to room temperature, subjected to final heat treatment in hydrogen at the time and temperatures set forth in Table I1 and subsequently the cores were 0 between the Cum temperatur? and 550 15 quickly brought to room temperature.

Improvement of the magnetic propertles in the range of low 1 temperatures obtained by the selection of alloying and heat The P P Y (l -0.5) ofthe f cores was determined y treatment canbeseen from the following examples. Reference a Maxwell budge at field lmellsflty of mos 0 at the is directed to Table I and to FIG. 3 which tabulates the chemif fl of t These condnlms closely approxlmate the cal composition of a number of alloys which were made and 20 i f For measuring dependency of the meet pen'neabllity of the temperatures in the range between 268.9 C. and +20 C., the cores were placed in a suitable TABLE I protective copper casing, cooled in a cryostat to the tempera- [Chemlcal composmo by Weghm ture of liquid helium (i.e. 268.9 C.) or liquid nitrogen (i.e. Ni Fe Cu Mo Mn Si 25 195.8 C.) and then permitted to warm naturally while the 75. 00 20 L 63 Trace permeability and temperatures were moni tored. The measure- 70.05 17.25 4. 37 1.75 0.50 0.02 ments of the temperatures below 200 C. were made by g" g" 8} means of a goldiron-chromel thermocouple and above -200 77. 50 15. 30 4. 5g 2. 23 8. 01 T 3 3 C. by means of a copper-constantan thermocouple which was 77. 05 14. 30 4. 4 2. 32 .03 70.35 10. 50 4.75 1.50 8.03 0. 0 30 P a the PP 93 3% 213? ii i? 21 '22 Trace The test results reproduced in Table I1 and the permeability 77.30 14. 05 4.40 2. s0 8. 77 0 values shown in FIGS. 4 to 7 as a function of temperature 3;: ,8 1%: g i: fig g: 2? 132 Trace demonstrate that the magnetic alloys with nickel-iron base ob- 72.20 14. 05 12. 30 g 1 g. 77 8 tamed according to th1s1nvent1on and when heat treated as set $1 $8 Z3 1;: 0 35 forth herein have in the range of low temperatures a far higher 70.75 14.10 13. 00 0.72 3.8 8-8: initial permeability than the presently available high grade 3: Q3 1 0 commercial nickel-iron materials whose maximum permea- 70. 15 17.15 0 3.05 g. 78 g a bility is in the range of room temperature as it is shown by the (0. 05 16. 25 0 4. 1 7 race dotted curvg infiFlGi TABLE 11 Final heat treatment Test Tem- Maximum temperainitial pera- Permeability 0.5 mile. at- Alloy Time ture permeability ture Shape of permeability, No. (hrs) C.) at, 0.5 1110c. C.) 200 C. 196 C. 0. temperature curve 2 600 54,000 260 54,000 44,000 20,000 Maximum below 260 c. 2 2 30,000 52,000 Narrow maximum.

2 60,000 32,000 Broad maximum. 3 2 63,000 34,000 (Fig. 4) 2 00, 000 23, 000 Do. 4 2 44, 000 26, 000 Narrow maximum.

2 69,000 32,000 Broad maximum. 5 2 04,000 32,000 Do. 2 00, 000 27,000 Do. 6 2 46,000 25,000 Maximum below 269 c. 2 27,000 17,000 7 2 80,000 43,000 Broad maximum.

2 68,000 24,000 D0. 8 2 03,000 25,000 Fi 5). 2 53,000 Do. 0 2 15,000 32,000 Fi 5). 10 2 100,000 27, 000

2 52,000 18,000 ll 2 16,000 10,000 Very narrow maximum. 12 2 52,000 32,000

2 33,000 20,000 Maximum under -250 2 54, 000 17, 000 14 2 30,000 20,000 2 32,000 14,000 15 2 30,000 25,000 (Fig. 7)- 2 70, 000 Do. 10 2 12, 000 10,000

2 43,000 36,000 Very narrow maximum. 17 2 3,000 17,000 (Fig. 0) 2 14,000 80,000 Do. 18 2 43,000 22,000 Maximum under 260 c. 13 2 00,000 14,000 (Fig. 0). 2 30,000 Do. 20 2 50,000 32,000 Broad maximum.

From the test data in Table II and from the permeabilitytemperature curves in FIGS. 4 to 9 it can be seen how the position and the form of the maxima of permeability depend on the composition of the alloys and on the heat treatments. As a principle for selection of a suitable material with easy magnetization at low temperatures it was found that in general the maximum of permeability is shifted toward the low temperatures by a lower final heat treatment temperature and also by longer annealing times. To avoid the Perminvar effect the final heat treatment must be at a temperature above the Curie temperature.

Another relationship found to exist in the alloy of the present invention is that where the molybdenum content increases toward the upper limit at any given nickel level the final heat treatment temperature must decrease toward the Curie temperature in order to achieve the high initial permeability. Also, where the alloy has a composition near the line F-G of FIG. 1 increasing nickel contents require higher final heat treatment temperatures approaching 550 C. in order to obtain the high initial permeability at low temperatures.

The maximum initial permeability of the alloys found outside of the range limit A B C D E A (Nos. 9, 11, 16 and 17) cannot be shifted into the temperature range of liquid nitrogen and of liquid helium by a final heat treatment at a lower temperature.

The advantage obtained with the invention consists in making available a more ductile magnetically soft material which has a very high permeability at the low temperatures, especially in the range between l80 and 269 C. The relationships which have been found permit the selection of the alloy and the final heat treatment so that the highest possible permeability or a permeability of predetermined value in a given range may be selected at will.

The magnetic materials according to this invention with the nickel-iron base with high permeability at low temperatures are suitable above all for the low temperature cooled magnetic shields, current transformers, and transmitters as well as for relays, magnetic switches, memories, and multipliers.

I claim as my invention:

l. A heat treated ductile nickel-iron base magnetic alloy consisting essentially of, by weight, from about 8.9% to about 27.6% iron, up to about 12.5% copper, up to about 4.6% molybdenum, from about 0.2% to about 1.0% manganese and the balance essentially nickel, the alloy exhibiting maximum initial permeability at subzero temperatures when the alloying components within the ranges set forth hereinbefore are balanced to provide an alloy having a composition within the area ABCDEA of FIG. 1 and in which the copper content is balanced with respect to the remainder of the alloying components to provide an alloy having the composition falling within the area KQLMNSOPK of FIG. 2, and the alloy has been given a final heat treatment at a temperature within the range between the Curie temperature and 5 50 C.

2. The alloy of claim 1 in which the copper content is balanced with respect to the remainder of the alloying component to provide an alloy having the composition within the area QRSTQ of FIG. 2.

3. The alloy of claim 1 in which the alloying components are balanced to provide an alloy having the composition within the area FGHJF of FIG. 1.

4. A readily workable heat treated nickel-iron base alloy containing copper, molybdenum and manganese, the alloying components being selected to provide an alloy having a composition falling within the area FGHJF of FIG. 1, the copper content is selected with respect to the remaining elements to provide a composition within the area QRSTQ of FIG. 2 and the alloy has been given a final heat treatment at a temperature within the range between the Curie temperature and 5 50 C, said alloy being characterized by exhibiting its maximum initial permeability at a temperature of below about l 00 C.

5. A magnetic core suitable for use at temperatures below about l00 C. having a high initial permeability and formed from the alloy of claim 1.

6. A heat treated ductile nickel-iron base magnetic alloy consisting essentially of, by weight, from 8.9 to 27.6% iron, up to 12.5% copper, up to 9.6% molybdenum, from 0.2% to 1.0% manganese and the balance nickel with incidental impurities, the alloy exhibiting maximum initial permeability at a temperature below I 00 C. when the alloying components within the ranges set forth hereinbefore are balanced to provide an alloy havin a composition withinthe area FGHJF of FIG. 1 and in whrc the copper content s balanced with respect to the remainder of the alloying components to provide an alloy having the composition falling within the area KQLMNSOPK of FIG. 2 and the alloy has been given a final heat treatment at a temperature within the range between about 440 C. and about 550 C.

Claims

2. The alloy of claim 1 in which the copper content is balanced with respect to the remainder of the alloying component to provide an alloy having the composition within the area QRSTQ of FIG. 2.
3. The alloy of claim 1 in which the alloying components are balanced to provide an alloy having the composition within the area FGHJF of FIG. 1.
4. A readily workable heat treated nickel-iron base alloy containing copper, molybdenum and manganese, the alloying components being selected to provide an alloy having a composition falling within the area FGHJF of FIG. 1, the copper content is selected with respect to the remaining elements to provide a composition within the area QRSTQ of FIG. 2 and the alloy has been given a final heat treatment at a temperature within the range between the Curie temperature and 550* C, said alloy being characterized by exhibiting its maximum initial permeability at a temperature of below about -100* C.
5. A magnetic core suitable for use at temperatures below about -100* C. having a high initial permeability and formed from the alloy of claim 1.
6. A heat treated ductile nickel-iron base magnetic alloy consisting essentially of, by weight, from 8.9 to 27.6% iron, up to 12.5% copper, up to 9.6% molybdenum, from 0.2% to 1.0% manganese and the balance nickel with incidental impurities, the alloy exhibiting maximum initial permeability at a temperature below -100* C. when the alloying components within the ranges set forth hereinbefore are balanced to provide an alloy having a composition within the area FGHJF of FIG. 1 and in which the copper content is balanced with respect to the remainder of the alloying components to provide an alloy having the composition falling within the area KQLMNSOPK of FIG. 2 and the alloy has been given a final heat treatment at a temperature within the range between about 440* C. and about 550* C.