US1845113A - Magnetic material and magnet core - Google Patents

Description

mmmm, CROSSREFERENEEJ Exa comma OR PLASTC mm;

Feb. 16, 1932. w, ANDREWS ET AL 1,845,113

MAGNETIC MATERIAL AND MAGNET CORE Filed Dec. 31. 1927 WWW/1M Patented Feb. 16, 1932 Human STATES JOHN WENDELL ANDREWS, OF CHICAGO,

ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED,

A CORPORATION OF NEW YORK am) RANDALL GILLIS, or 131mm, rumors,

OF NEW YORK, N. Y,

MAGNETIC MATERIAL AND MAGNET CORE Application filed December 81, 1927. Serial 1T0. 244,020.

This invention relates to magnetic materials and magnet cores, and especially to magnetic cores for loading coils for use in telephone circuits. j The principal object of the invention is the production. of magnetic elements hav ng stab e magnetic properties undel: varying magnetic conditions. a

Another object of the invention is the production of magnetic elements having low core losses and a relatively high permeability to enable a given inductance "to be obtained from a minimum amount of material, and possessing to a high degree those electrical f and magnetic characteristics which make 11:

highly desirable in electrical signalling apparatus, particularly in loading coils for telephone circuits. I Y Y In accordance with one embodiment, the present invention contemplates the construc-' tion of magnetic cores of an allo including nickel and iron in finely divided iorm, heat treated to -Ha'r e a higher inherent magnetic permeability and lower inherent hysteresis 26 loss'tha n iron, and combined with a suitable insulatin material. More specifically, the

: mates the formation of magnetic cores of a n'ckel-iron allo in finely divided form in whlcli the proportions of its :0 constituents are .such that the resulting alloy has tlhe maiiimum magneltic stabilit The meta partic es are treate with a re ractory insulating material whereby the a 0y particles are individually insulated after which they are compressed into cores of the desired sha e and size.) The cores are heat tr ategl at t e optimum temperature for the paftid lar alloy of which they are constructed to give the cores'the' desired mechanical, elec- 40 trical and magnetic characteristics.

It is believed that the mvention will be clearly understood from the following detailed description of one embodimentthereof and the accompanying drawings, which Fig. 1 is a perspective view of a section of a loading coil core. made in accordance with the present invention, and

Fig. 2 shows a plurality of these sections assembled to form a completed core.-

It will be understood, however, that this is merely illustrative and the invention is not limited to the production of this form of core, but is adapted to the production of cores for magnetic articles of many forms.

In carrying out the present invention the ma netic material is prepared in the followmg manner. e magnetic material employed is pre ared from a nickel-iron alloE commonly re erred to as erma o w 10 is treated in a manner more u y described in the copending application of H. M. E. Heinicke, Serial No. 229,801, filed October 29, 1927, to reduce the alloy to a finely divided form. Experience has proven that where low eddy current losses are desired it is essential that the particles be of a small size and preferably 0 such size that all of the particles will readily pass through what is generally known as a 120 mesh screen and a large percentage pass through a 200 mesh screen. According to one embodiment of the invention, the alloy is prepared by melting ap roximately 80 parts of nickel and 20 parts 0 iron in an oxidizing atmosphere and pouring the resulting alloy into a mold. When prepared according to the 'foregoin process,'the resulting alloy will be exceedingly brittle and it is therefore particularly adapted to be reduced-to a finely divided or dust form from which cores may be molded.

The brittle ingots obtained from the above described process are successively passed through progressively reducing hot rolls which decrease the cross sectional dimensions of the piece of material and the final roll is effected at approximately the temperature at which the alloy ceases to be malleable, after which the rolled material is quenched to a temperature below that at which it loses its malleability. By the hot rolling and quenching process the size of the crystalline structure is materially reduced, which is very de I sirable because disintegration of the material takes place mainly at the crystal boundaries, and consequently the smaller the size of the crystals the finer the dust which can be produced from the finished product. The rolled and quenched material is broken into 'shortpieces and thepieces are crushed in a jaw crusher, hammer mill, or any other suitscam PlAS 'C able type of apparatus, after which .the crushed material is reduced to a fine dust in a ball mill or any other suitable p'ulverizing device. The dust is sieved through a 120 5 mesh sieve and any residue-is remelted and again carried through the above described operations to reduce the material to a finely divided form. The finel 1 tained by t e above described operations is particularly adapted to be formed into rings or cores for loading coils by individuallyinsulating the particles with a refractory insulating material and ,compressing the.

insulated particles. The particles ma be insulated in accordance with the metho described more fully in our copending applicain which method the finely divided particles of the nickel-iron alloy are annealed in a closed container at a temperature of approximately 925 (1, after which the resulting cake of annealed alloy is again reduced to a finely ivided form. The annealed then individually insu ate articles are w1t1 a refrac- A tory insulator comprising approximately:

- parts of chromic acid 5 parts of ta 0 4 parts of water lass composed of 50% so 2 total solids an con alning approximately 1.58 parts of SiO to 1 part of Na O.

The insulated dust particles are then in a form suitable for ressing into cores or rings 35 which are prefera ly formed with a pressure of approximately 200,000 pounds. per. square inch. A hi hpressure is used in forming the rings in 5? er toiaatase their density, since it has been found that the'permeability of the 40 rings increases with increased density. Following this step, the cores are transferred without unduly exposing them to the air into an annealing furnace in which they are annealed at the optimum annealing temperature of approximately Q. and cooled. If

"he i1 d..ia-ua r.

necessary, the cores may M a to remove soluble substances and to render the cores chemically stable, and dried at a temperature of approximately 100 C.

A plurality of rings thus romaine then stacked coaxially to form a core on which the usual toroidal winding is applied, the number of such ringsfu'sed depending upon the existing electrical characteristics of the telephone circuit with which the loading coils are to be associated.

Although the alloy "has been des'cribed asing composed of approximately 80% nickel and the remainder principally iron, 50 it is to be understood that the proportions of the ingredients may be varied without departin from the spirit and scope of the invention. For example, nickel-iron allo having substantially stable magnetic properties may be produced by employing from divided magnetic material obposed of the oxides of the constituents of the tion, Serial No. 102,729, filed April 17, 1926,

LAQQIHIIV alloy upon the particles. In fact, any insulating material which will serve to individually insulate the finely divided particles and which will withstand the effects of the annealing treatment to which the compressed rings are subjected may be employed with. satisfactory results. a

By the term magnetic stability which is employed hereinbefore in the specification and hereinafter in the annexed claims, is meant that the permeability of the material and consequently the inductance of a' coil employing such material is substantially unaffected by instantaneous direct current magnetizations. The magnetic stability of the alloy may be computed from the diflerence in the inductance of a coil before and after being subjected to an instantaneous direct current magnetization, and may be expressed "by the following formula:

100AL L .JOOAL which represents the percent change in inductance produced by the instantaneous direct current magnetization, falls within the limits of i.5% andconsequently the magnetic stability, represented by the letter for an alloy containing approximately nickel is 99.5% to 100.5%.

B using an alloy of the proportions stated in t e preceding paragraphs and by followingi the foregoing method of insulating the ividual alloy particles and compressing the particles into cores or rings, magnetic structures are produced which have an extremely *high magnetic stability and permeability from the minimum amount of material. By the use of such cores or rin s, inductance units having a high magnetic stability, having the same permeability with What is claimed is:

1. A magnetic core of high magnetic stability composed of finely divided individually insulated particles of an alloy of approximately 80% nickel and iron annealed at a temperature of approximately 925 C. formed into shape under a pressure of approximately 200,000 pounds per square I inch and annealed as a whole at a tempera-' ture of approximately 500 C.

2. The process of manufacturing ma netic cores of high magnetic stability whic consists in reduclng an alloy of approximately 80% nickel and 20% iron to dust, annealing the dust at a temperature of ap roximately 925 C., reducing the anneale cake to dust a ain, coating the particles of dust with a re ractory insulating material, pressing the insulated dust into form under a pressure of approximately 200,000 pounds per square inch, and annealing the formed cores at a temperature of approximately 3. A magnetic core of high ma etic stability comprising finely divided in ividually insulated particles of an alloy comprising from 79% to 84% nickel and the remainder principally iron annealed at a temperature of the order of 925 0. formed into shape under a pressure of the order of 200,- 000 pounds per square inch and annealed as a .whole to produce a high magnetic stability. In witness whereof, we hereunto subscribe our7names this 24th day of December, A. D. 192

JOHN WENDELL ANDREWS. RANDALL GILLIS.

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