US1669645A

US1669645A - Magnetic material

Info

Publication number: US1669645A
Application number: US158800A
Authority: US
Inventors: Andrews John Wendell; Gillis Randall
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1927-01-03
Filing date: 1927-01-03
Publication date: 1928-05-15
Anticipated expiration: 1945-05-15

Description

May 15, 1928. 1,669,645

J. W. ANDREWS ET AL MAGNETIC MATERIAL Original Filed Jan. 5, 1927' men/0w:- John W And/9W5 Ram/M 6////3 Patented May 15, 1928.

1,669,645 PATENT OFFICE.

JOHN WENDELL ANDREWS, OF CHICAGO, AND RANDALL GILLIS, 0E IBERWYN, 1am- NoIs, AssIeNoRs zro WESTERN ELECTRIC COMPANY, INCORPORATED, on NEW YORK, N. 2., A CORPORATION OF NEW YORK.

MAGNETIC MATERIAL.

Application filed January 3, 1927, Serial No. 158,800. Renewed February 16, 1923,

This invention relates to magnetic materials and magnet cores, and more especially to magnet cores for loading coils for telephone circuits and their method of production.

The principal object of the invention is the production of a magnetic element having low core losses and a relatively high permeability to enable a iven inductance to be obtained from a minimum amount of material, and possessing to a high degree those'electrical and magnetic characteristics which make it highly desirable in electrical signalling apparatus, particularly in loading coils for telephone circuits.

In accordance with one embodiment, the present invention contemplates the construction of magnet cores of an alloy including nickel and iron in finely divided form, heat treated to have a higher inherent magnetic permeability and lower inherent hysteresis loss than iron, and combined with a suitable insulating material. More specifically, the invention contemplates the formation of the magnetcores of a nickel iron alloy in finely divided form in which the proportions of its constituents are more than 25% of nickel and the remainder principally iron, and in a form which has proven satisfactory the nickel content being approximately 78 of the whole. The meta particles are treated with a solution of a nitrate which is. capable of being decomposed to form an adherent insulating coating around the particles, after which the particles are pressed into cores of the desired shape and size. The cores are heat treated at the optimum temperature for the particular alloy of which the cores are constructed to obtain the characteristics desired for the use to which the cores are to be put. 1

It is believed that the invention will be clearly understood from the following detailed description of one embodiment thereofand the accompanying drawing, in 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 duced to a fine dust.

cores for magnetic articles of many forms.

In carrying out the present invention the magnetic material is prepared in the followmg manner. The magnetic material employed is preferably prepared from a nickel iron alloy commonly referred to as permal- 10y, which is treated in a manner more fully described in the copending application of P. Beath and H. M. E. Heinicke, Serial No. 101,179, filed April 10, 1926, 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 of such size that all of the particles will readily pass through what is generally known as a one hundred and twenty mesh screen and a large percentage pass through a two hundred mesh screen. According to one embodiment of the invention the alloy 18 prepared by melting approximately 7 8 parts of nickel and 21 parts of iron in an oxidizing atmosphere and pouring the resulting alloy into a mold. When prepared according to the foregoing process the resulting alloy will be exceedingly brittle and is therefore particularly adapted to be reduced to a finely divided or dust form from which the finished cores are molded.

After the brittle ingots are obtained they are passed successively through progres sively reducing hot rolls which form the alloy into fiat slabs approximately thick. By the hot rolling process the size of the crystalline structure is materially reduced, which, since the disintegration of the material takes place mainly at the crystal boundarms, is essential in order to have a satisfactory yield of dust. The rolled slabs are broken into short pieces and are then crushed in a jaw crusher, hammer mill or any other suitable type of apparatus in which a further reduction occurs. The material after being passed through the jaw crusher is subsequently rolled in a ball mill until it is re- This dust is sieved through a one hundred and twenty mesh sieve and any residue is remelted and the foregoing operation is again repeated to reduce the material to a finely divided form. Prior to the addition of the insulating material the finely divided particles of the nickel iron alloy are annealed in a closed container at a temperature of approximately 750 C.

to 980 (3., a temperature of about 925 C. having proven to be one which produces very satisfactory results. It is then necessary to again reduce the annealed alloy which is now in the form of. a cake, to a finely divided form after which itis mixed with the insulator.

According to one form of the invention, the insulator for the dust particles is prepared by dissolving a quantity of mercuric nitrate equal to from 5 to 5.5 per cent of the finished product in a sufficient quantity of water to form a mixture which will cover the entire quantity of dust to be insulated. lhe permalloy particles are added to the solution of mercuric nitrate and the entire mass is boiled to dryness accompanied by constant stirring to prevent caking and to insure a thorough coating ofthe individual dust particles. Shortly after the dust becomes dry, oxides of nitrogen will be evolved which may be noted by the appearance of brown fumes. The dust is dried for a definite length of time after the appearance of the fumes, which time depends upon the insulator used, the temperature at which it is heated and the characteristics desired in the finished ring, a period of from fifteen to thirty minutes having proved to give satisfactory results with mercuric nitrate as the insulator. The dried insulated dust parti else are then in a form suitable for pressing into cores or rings which are preferably formed with a pressure of approximately 200,000 pounds per square inch. A high pressure is used in forming the rings in order to increase their density, since it has been found that the permeability of the rings increases with increased density. Following this step in the process of constructing the cores and without unduly exposing them to the air they are transferred to an annealing furnace in which they are annealed at the optimum annealing temperature of approximately 500 C. and cooled. A few test rings may be made of dust insulated in the above described manner and their permeability measured. Should their permeability be too low, it may be increased b the addition of a predetermined quantity 0% uninsulated dust to the insulated dust before it is pressed into rings.

A plurality of rings thus formed are then stacked coaxially to form a core on which the usual toroidal winding is applied, the number of such rings used depending upon the existing electrical ephone circuit with which the loading coils are to be associated.

Although in the above described method the permalloy particles are insulated with a solution containing mercuric nitrate amounting to approximately 5 to 5.5 per cent of the finished product,.it is, of course, to be understood that the proportions of the ingrecharacteristics of the telaecaess dients may be varied without departing from the spirit and scope of the invention and that the length of the drying period may be varied to produce varying characteristics in the final product. Also nitrates other than mercuric nitrate which upon heating with the permalloy decompose with the formation of an adherent insulating material may be employed as the insulating medium, the following having proved to be satisfactory substitutes: aluminum, ammonium, barium, bismuth, cadmium, chromium, c0- balt, copper, iron, lead, magnesium, manganese, mercurous, nickel, silver and zinc nitrates. Or the particles may be insulated by treating them with a nitric acid solution which interacts with the alloy to give the nitrates of iron and nickel which in turn may be treated in the manner described above for solutions containing added nitrates.

By using an alloy of the proportions stated in the preceding paragraphs and by following the foregoing method of insulating the individual alloy particles and compressing the particles into cores or rings, magnet cores or rings are produced which have a high permeability. By the use of such cores or rings, inductance units having the same permeability with equal or less hysteresis and eddy current losses as cores constructed according to previously known methods, but with much less core volume and much less coil volume, are available.

What is claimed is:

1. As a new article of manufacture, a magnetic substance composed of particles of a magnetic material, and an insulating material consisting of a metal nitrate separating the particles.

2. As a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy, and an insulating material consisting of the residue of a decomposed nitrate separating the particles.

3. As a new article of manufacture, a magnetic substance composed of particles of a magnetic material, and an insulating material consisting of mercuric nitrate separating the particles.

4. As a new article of manufacture, a magnetic substance composed of particles of a magnetic nickel iron alloy, and an insulating material obtained from a metal nitrate.

5. As anew article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy composed of more than 25 per cent nickel and the remainder principally iron, and an insulating material consisting of mercuric nitrate separating the particles.

6. As a new article of manufacture, a magnetic substance composed of particles of ill) a magnetic alloy enveloped by an insulating material resulting from the partial decompogition 01 a nitrate.

t. The method of making magnetic structures which consists in treating particles of a magnetic material with a metal nitrate, and partially decomposing the nitrate to form a coating upon the particles.

8: The method of making magnetic structures which consists in treating particles of a magnetic material with a metal nitrate, and heating the treated particles for a predetermined period of time to produce an insulating coating thereon.

9. The method of making magnetic structures which consists in coating the particles of a magnetic material with a metal nitrate, and forming a mass of such coated particles into a homogeneous solid.

10. The method of making n'iagnetic structures, which consists in immersing particles of a magnetic alloy in a solution of a metal'nitrate, evaporating the solvents, and heating the resulting mass to partially decompose the metal nitrate.

11. The method of making magnetic structures composed of an alloy, which consists in reducing the alloy to a finely divided form, heating the finely divided mixture, again reducing the product so obtained to a finely divided form, coating the resulting product with a metal nitrate, and partially decomposing the metal nitrate upon the particles.

12. The method of making magnetic structures, which consists in reducing a magnetic alloy comprising more than per cent nickel and the remainder principally iron to a finely divided form, heating the finely divided mixture at a temperature of approximately 750 C. to 980 (3., again reducing the product so obtained to a finely divided form, treatin the resulting product with a metal nitrate, i orming a mass of such treated particles into a homogeneous solid, and heating the solid mass at a temperature of approximately 500 C.

In witness whereof, we hereunto subscribe our names this 23rd day of December A. D.,

JOHN WENDELL ANDREWS. RANDALL GILLIS.