US1669648A - Magnetic material - Google Patents

Description

May 15, 1928.

1,669,648 A. F. BANDUR MAGNETIC MATERIAL Filed Jan. 5, 192'? mmmfa/ Adaflffiawda/ mz'.

tailed description of one embodiment t Patented May 15, 1928.

UNITED STATES PATENT orrica.

ADOLZH FRANCIS BANDUR, 0F BERWYN, ILLINOIS, ASSIGNOR TO. WESTERN ELECTRIC COHRANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

HAGNETIC MATERIAL.

Application filed January 3, 1927. Serial No. 158,801.

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 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 and magnetic characteristics wh ch make it highly desirable in electrical signaling apparatus, particularly in loading coils for telephone circuits.

In accordance with one embodiment, the present invention contemplates the c0nstr uction of magnet cores of an alloy including nickel and iron in finely divided form combined with a suitable insulating material and heat treated to have ahigher inherent magnetic permeability and lower inherent hysteresis loss than iron. More especlally, the invention contemplates the formation of the magnet cores 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 principall iron, and in a form which has proven satis actory the nickel content being approxlmately 78 of the whole. The metal particles are cleaned and are then treated so as to chemically change the surface layer of each dust particle to. form an adhering coating thereon, after which the particles may be pressed into rings or cores of the desired shape and size. Or the chemically treated particles may be thoroughly mixed with a heat resistant material until they have received a secondary insulating coating before they are pressed into rings. The cores so formed are finally heat treated to the opti mum temperature for the particular combination of alloy and insulator of which the cores are constructed'to give them the dc sired characteristics for the use to which they are to be put.

It is believed that the invention will be clearly understood from the followingI deereof and from the accompanying drawing, in Which Fig- .1 is a p p tive view at a .sectlon of core but is adapted to the production of 4 cores of magnetic particles of many forms.

In carrying out the present invention the magnetic material is prepared in the follow 111g manner: The magnetic material employed is preferably prepared from a nickel iron alloy commonly referred to as permalloy which is treated in a manner more fully described in the copendin application of C. P. Beath and H. M. E Heinicke, Serial No. 101,179, filed April 10, 1926, to reduce the alloy to a finely divided form. Expe name has proven that where low edd current losses are desired it is essential that the particles be of small size and preferably of 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 approximately 78% parts of nickel and 21 parts of iron in an oxidizing atmosphere and pouring the resulting alloy into a mold. hen 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 while hot throu h progressively reducing rolls which form t e alloy into flat slabs approximately onequarter of an inch 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 boundaries, 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 ap paratus in which a further reduction occurs. The material after being passed through the jaw crusher is ,subsequeutly rolled in a ball mill until it is reduced to a fine dust. The dust is sieved through a 120 mesh sieve and any residue is remelted and the foregoing operationis repeated to again 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 proximately closed container at a temperature of ap- 750 C. to 980 6., the temper-' ature of about 925 C. having provcn 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 the particles are cleaned in any suitable manner, such as by immersing them in an acid solution, to remove any grease or other adherent material so that a chemical change may be readily eifected in the surface layers of the individual particles.

'According to'one embodiment of the nvention, the surface layer of each of the individual particles is chemically changed by combining the constituents of the alloy present in the layer with sufficient oxygen to form an oxide, coating around each particle. This combination may be effected in any one of several ways, a very satisfactory method comprising spreading the partlcles in a thin layer upon a suitable plate and heating the particles in the open air at a temperature of approximately 550 to 800 C. for about twenty minutes, by which treatment an adherent, insulating coating consisting of oxides of nickel and iron is produced upon each of the particles. The oxidized particles may then be pressed into cores or rings-under high pressure Instead 'of forming the cores or rings from the oxidized particles alone, satisfactory rings may be formed of the oxidized,

particles coated with a secondary insulating material. In order to form this secondary coating, the oxidized particles are placed in a revolving drum and a heat resistant material, such as kaolin, whose insulating properties are unimpaired by high temperatures, 15

added, the amount of heat resistant material used depending upon the characteristics desired in the finished core. This mixture is tumbled in the drum to thoroughly mix the ingredients until the dust particles assume a uniform color which indicates that they are thoroughly coated with the secondary insulator. The insulated dust particles 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. Finally the cores, whether formed of the oxidized particles alone or of the'coated, oxidized particles,

are transferred to an annealing furnace Where they are annealed'at a temperature of from 425 C. to 780 C. A few test rings may be made of dust insulated in the above manner and their permeability measured. Should their permeability be too low, it may be increased by the addition of a predetermined amount of'nninsulated dust or dust which has a light coating of insulator, to the insulated dust before it is pressed into rings.

A plurality of rings thus formed are 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 characteristics of the telephone circuit with which the loading coils are to be associated.

Although in the above described method of treating the permalloy particles they are t given a primary insulating coating by oxidizing'the surfaceelayers of the individual particles by heating the particles in the open air, it is, of course, to be understood that the primary insulating coating may be produced by effecting any chemical change in the surface layer which will produce an insulating T coating upon the particles. Instead of oxidizing the particles by heating them in air it is possible to effect an oxidation by heating the particles in pure oxygen or by treating the particles with an oxidizing agent. Or instead of oxidizing the particles they may be treated with fluorine, bromine, chlo- 1 will retain their insulating properties during the subsequent heat treating operation, maybe employed to form a secondary insulating coating around the particles, and the resulting cores will be satisfactory from both a magnetic and electrical standpoint.

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 ex- .tremely desirable electrical characteristics with a minimum amount of materialemployed. By the use of such cores or rings, inductance units having a higher premeability with equal or less hysteresis and eddy current losses as cores constructedaccording 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 alloy, and an insulating material consisting of the constituents of the alloy chemically combined with another substance separating the particles.

2. As a new article of manufacture, a

- magnetic substance composed of finely divided particles of a nickel iron alloy, and an insulating material consisting of oxides of nickel and iron enveloping the particles.

3. As a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy composed of more than 25% nickel and the remainder principally iron, and an insulating material consisting of oxides of the constituents of the alloy.

4. As a new article of manufacture, a magnetic substance composed of particles of a magnetic alloy, and a plurality of coatings of different insulating materials enveloping the particles, one of the coatings comprising oxides of the constituents of the allo 5. As a new article of manufacture, a magnetic substance composed of particles of a magnetic alloy, and a plurality of coatings of different insulating materials enveloping the particles, one of the coatings obtained from the magnetic alloy by chemical reaction and another coating comprising a heat resistant material.

6. As a new article of manufacture, a magnetic substance composed of particles of a magnetic alloy, a rimary coating obtained by the chemical union of the alloy with another material, and a secondary insulating coating of kaolin separating the particles.

7. As a new article of manufacture, a magnetic substance composed of a magnetic allow composed of more than 25% nickel and the remainder principally iron, a primary coating obtained by the chemical union of the constituents of the surface layer of each of the alloy particles with oxygen, and a secondary insulating coating of kaolin separating the particles.

8. The method of making magnetic structures composed of a magnetic alloy, which consists in reducing the alloy to finely divided particles, heating the particles, again reducing the product so obtained to finely divided particles, effecting a chemical change in the surface layer of each of the particles, forming a mass of such particles into a homogeneous solid, and heating the solid mass to a high temperature.

9. The method of making magnetic structures, which consists in forming an oxide coating upon particles of a metallic alloy,

enveloping the oxidized particles with a heat resistant insulating material, and forming a mass of such insulated particles into a homogeneous solid.

10. The method of making magnetic structures, which consists in treating finely divided particles of a magnetic alloy so as to effect a chemical change in the surface layer of each of the particles, enveloping the treated particles with a heat resistant insulating material, and forming a mass of such insulated particles into a homogeneous solid.

11. The method of making magnetic structures, which consists in treating particles of magnetic material to effect a change in the surface layer of the particles, forming a mass of the changed particles into a homogeneous solid, and heat treating the solid mass at a temperature to impart thereto the desired magnetic properties.

12. As a new article of manufacture, a magnetic substance composed of a magnetic alloy, a primary coating obtained by the chemical union of the alloy with another material, and a refractory insulating material separating the particles.

13. A metallic structure comprisin elements of magnetic material separated y an insulating coating thereon comprising an oxide of said material and a non-conducting oxide of another material.

14. A magnetic structure comprising magnctic material in the form of dust and an insulating coating on the dust particles comprising an oxide of said material and a nonconducting oxide of another material.

In witness whereof, I hereunto subscribe my name this 24th day of December, A. D. 1926.

ADOLPH FRANCIS BANDUR,

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