US1857201A - Process for insulating magnetic bodies - Google Patents

Description

its. COMPOSITION/IS, GROSS Emma comma I UNITED STATES-PATENT orr cs HUBBEL LATHBOP, or enmwrcn, colmncrrcu'r, .ASSIGNOB "r BELL rnnnrnoma- LABORATORIES, mcoarom'rm), on NEW YORK, N. 2., a conronnrron or NEW Yonx a t rnocnss on msunn'rme menn'rrc nomns in Drawing. Application and my a, 1931. Serial 110. 548,484.

.This invention relates to magnetic bodies form, and a volatile li uid such as wajzgr, and particularly to methods of producing and then to evaporate the whole to dFy ness magnetic bodies of the ty e employingfinely with constant stirring in order to coat the divided magnetic matena l; magnetic particles with the-insulating mate- An object of the invention is to improve the rial. The total amount of insulating material magnetic characteristics of magnetic bodies is thus applied to the magnetic dust particles of the type employing magnetic material in In one layer. The insulated magnetic pa'r-' finely divided form, for example, magnetic ticles are then compressed under hi h presdust cores for loading coils. sure into the desired core form, an the re- 1 Magnetic cores made from finely divided sulting cores are givenasubsequent annealing magnetic material, so-called magnetic dust heat treatment to improve their magnetic cores, are being extensively used for the loadlfl erl csing coils which are inserted in telephone lines In accordance with the resent invention to improve their transmission characteristics. the rocess of insulation a ove described is L 15 Such cores are usually constructed by submodified in that the ipgulating material is a jec'ting the finely divided particles of the lied to themagp etic dggpapt clesapofi on magnetic material and a non-magnetic matea a times?) as to' obtam several layers ofthe rial between the magnetic particles, to ex samemsulating material between the magtremely high pressures in the neighborhood n ic part cl Th ch ng in the m t go of 200,000 pounds per square inch. The high of insulating has been found to materially pressures are utilized to form the component improve the magnetlc properties, and particuv materials into a substantially homogeneous larly to reduce the eddy current loss in the mass in the desired core form, and to give sufcompleted core. ficient mechanical strength to the completed The exact nature of the invention and the as core. The non-magnetic material is of such advantages thereof will be better understood a nature as to serve as a binder, andalso as from the following detailed description of an insulation between the magnetic particles the process for producing a magnetic dust to reduce eddy current losses in the completed core or a loading coil embodying the inven-' core., 'In the-case especially where the magtion.

a netic material in the core made in the above In practicing the present invention, the described manner is a magnetic alloy includmagnetic material is preferably prepared ing nickel and iron, it is desirable also to subfrom a brittle alloy containing nickel and ]ect the core to subsequent heat treatment at iron, with or without the addition of other a high temperature to remove the strains inconstituents, and commonly known aW SI troduced in the magnetic material by the alloy The-alloy may be prepare 1n e pressing operationtending to impair them described in the U. S. Patent No. magnetic properties of the magnetic alloy in 1,669.649 issued May 15, 1928 to (LP. Beaththe core. and to fully develop the magnetic and H. M. E; Heinicke, wherein the magcharacteristics of the alloy. It is desirable, netic metals, for example, nickel and iron in 40 therefore, that the insulating material have proportions depending upon the desired persuch characteristics and be applied in such centage of the alloy, are melted together in manner to the dust particles that it will withsin-oxidizing atmosphere, the resulting alloy stand without deterioration from an insulatbeing poured into a mold to form an ingot. ing standpoint the heat treatment and'me- The-ingot while still hot is successively passed v chanical operations utilized in producing the through progressively reducing rolls to decore. a crease its cross-section, the final roll being Amethod commonly used for insulating the preferably efiected at approximatel the temma netie dust in the process of making loadrature at which the allo ceases to mallea mg coil cores is to mix the magnetic dust 1e, after which the ingot 1s quenehedinwater with the insulatim in finely divided at a temperature below that in which it loses i th solution of SQd nm .sili cm, and chromic 15 a ball mill for several hours.

46 of the annealed finely silicatp in sol utip n with 1.1 grams of chromic Each 1000 grams of 55 mixed with 2.5 grams el 60 stirring,

its malleability. This treatment is for the purpose of producing a fine crystalline struc ture in the allo material since when the material is reduce to finely divided form its disintegration takes place at the crystal boundaries, and conse uently the smallerthe size of the crystals the finer the dust which can be produced therefrom. The slabs of-alloy material 'so produced are then broken into short pieces and the pieces reduced to the form of dust in any suitable manner for example by crushing in a rock crusher, hammer mill, or other suitable apparatus, after which the crushed material is pulverized by rolling in After several hours of rolling the resulting dust is sieved through a 120 mesh sieve and that portion which will not pass through the sieve is returned to the ball mill for further rolling, go this process being repeated until a 'sufiicient uantity of the very'fine dust is obtained.

r-iorto the addition of the insulating material the finely divided articles of the alloy are annealed in a closed container at a temperature of approximately 885 C. It is then necessary to again reduce the annealed alloy which is now in the form of a cake to a finely.

divided iorm ready for insulation.

' The general method of insulating the magnetic particles in accordance with this invention was tried with several insulating com- 1 positions. In each case a material improvement inthe magnetic properties of the completed core was observed over that obtained when the usual method of insulation was employed.

' In one case the method of the invention was applied to the insulation of the annealed magnetic articles with an i sulatin com 081- 40 tlon comprislng lggglgm talc @E upfi s i licte, F cliromlc acetate and waterfieuc as isclosed 3 an speci ca y claimed inmy co plication, Serial No. 556,951, file August .14,

1931. It was desired to insulate 1000 grams rmallo d 1 1 st with a total of 6.5 grams fine y ivided kaolin, 6.5 grams ivided talp and 11.0grams of sodium ioetat This was done as follows: I 5 .The 11.0 grams of sodiun i sili cate and 1.1 f grams of chromic acetate were first dissolved in wate'r toTt'otal s olution volume of 333 cc.

v1 ed talc and 2.5 grams finely divided aolin .11I cc. of

' Then, an' additional 2.0 grams talc and 2.0

grams kaolinwere mixed witE the coated magnetic particles an additional 111 cc. of

the

solution added thereto, and the whole sodium silicate. One third-o ding aptransferred to an annealin rmallo dust were then evaporated again to d ess with constant st1rr1ng,"toform a secon "1a" "er of insulation on the permallo dustparticles. Then the resulting coate magnetic particles were mixed with the remaining 2.0 grams talc and 2.0 grams kaolin, the remaining HT 6c. of the solutiofi'a'dded thereto, and the whole evaficTfia'fEd to dryness to form a third layer of insulation on the magnetic particles.

In another case it was desired to insulate the annealed permalloy dust with an insulating composition such as disclosed in my copending application, Serial No. 459,564 filed June 6, 1930. The insulating material used comprises 1.6 grams sodium silicate and 1.0 grams tale for each ams of the ma etic diTstT A solutiono the sodium silica fi in water was first made up, 40 cc. of waterbeing used for each 1.6 rams of the the tale in dry powder form was then mixed with the total amount of the permalloy dust, one third of the sodium silicate so ution was added the magnetic particles. The insulate 'mag- I netic particles were then mixed with another one third of the tale, another one third of the sodium silicate soliition was added thereto and the resulting mixture was again evaporated to dryness to form the second coating of the insulating material on, the magnetic dust .particles. The remaining one third ortion of talc was then mixed with the insuated maone thir of the sodium silicate solution was added thereto and then the resulting mixture was evaporated todryness to form the third coating of insulating material upon the magnetic particles.

above described manner were respectively etic dust particles, the remaining flhe magnetlc dust particles insulated with the difierent insulating compositions in the sifted through a 16 mesh sieve, placed in a.-

mold and compressed into core partsunder a pressure of approximately 200,000 pounds per square inch. The core parts were then furnace where they were annealed at a high temperature either in airor in hydrogen to relieve the internal stresses set up by the pressing operation, thereby producing a core having low hysteresis loss. I

Where the annealing heat treatment is carried out in air, the core parts are preferably subjected to a temperature of approximately 500 C. forabout 45 minutes. Where the'annealing heat. treatment is carried out in hydrogen,.the core parts are preferably subjectedto a temperature of approximately 650 C. for about 30 minutes. a

One or more core parts thus formed are then stacked to form a core to'which the usual toroidal winding'is applied to form a loading coil, the number of core parts used in I06. COMPOSITIONS,

COATING ORPIASUC 'inpi coil is to be associated.

each core depending u on the electrical char-' acteristics 0 the circuit with which the loadestsof magnetic cores insulated by the method of the invention in which the insulating material ,was applied in three or more stages as described above and other cores made at the same time using the same amount and kind of insulating material applied in" a single layer by the usual method, showed that the former method resulted in much lower eddy current losses in all cases and in most cases in improved hysteresis characteristics not limited to the particular constituents and proportions of the magnetic and insulating materials above mentioned which were given by way of example only, but that it is of a eneric nature applicable to all magnetic and insulating materials which are commonly used in the production of magnetic bodies of the type employing magnetic material in finely divided form. It is to be understood also that the method of applying the insulatmg material may be varied somewhat from that described above without departing from the spirit of the invention which is limited only within the scope of the appended claims.

a What is claimed is:

1. In the'process of makin a magneto body comprising finely divided magnetic particles insulated from each other by a given, amount of insulating material, the method of insulating the magnetic particles which-consists in mixing sa1d particles with a portion of the insulating material in a volatile liquid and evaporating the mixture to d ness, and mixingthe resulting product wit another portion of the insulating material in a volatile lii uid and evaporating to dryness.

n the process of makin a'magnetic body comprising finely divided magnetic "CR SS mamas" body having a low eddy current loss from a given amount of finely divided ma etic material and a given amount of a fine insulatin and binding material mcluding both solu 1e and insoluble in redients, which method consists in mixingt e total amount of the mamietic material with a'portion of the insoluble ingredients of the insulating and binding material in dry form, adding to the mixture a liquid solution of a portion of the solubleingredients of the insulating and binding material and evaporating the whole to dryness with constant stirring mixing. the resulting coated magnetic particles with another portion of said insoluble ingredients in dry form; addin to the resulting mixture 9. liquid solution 0 another portion of said soluble ingredients and evaporating the whole to dryness with constant stirring,- repeating the rocess until all of the insulating an binding material has been applied as coatin s to the magnetic particles, compressing t e resultant product into a substantially h0- mogeneous mass in the desired 'form, and then heat treating the formed product to remove strains in the ma etic material.

4. In the process 0 makin a magnetic body comprising finely divided particles of magnetic material insulated from each other by a given amount of insulationcomprising several constituent materials, the method of insulating the magnetic particles which consists in mixing in a volatile liquid said mag- Examiner divided netic particles with a portion of the insulation comprising a portion of each of the constituent materlals and evaporating the mixture to dryness, mixing the resulting product in a volatile liquid with another portion of the insulation'comprising a portion of each constituent material and evaporating the mixture to dryness, and repeating this process until the entire amount of the insulation has been applied to the magnetic particles in successive layers.

In witness whereof, I hereunto subscribe my name this 1st day of'July, 1931. v

.HUBBEL LATHROP.

particles insulated from each other by a given amount of insulating material, the method of insulating the magnetic particles which consists in mixin said magnetic particles with a portion of t e total amount of insulating material in a volatile liquid and evaporat ing the mixture to dryness'to form an insulating coating on the particles, mixing the coated particles with another portion of the insulating material in a volatile liquid and evaporating the mixture to dryness to form a applied to the magnetic articles in layers;

. 3.The method. of pro ucin'g a magnetic second layer of insulating material on the