US2118285A - Composite permanent magnets of mixed comminuted alloys - Google Patents

Description

Patented Mal {24, 1 93s 2,11 235 UNITED STATES PATENT- OFFICE COM'POSITE PERMANENT MAGNETS OF MIXED COMMINUTEI) ALLOYS No Drawing. Application November 7, 1936, Se-

rial No. 109,683. In Germany November 16,

7 Claims. (Cl. 175-21) This invention relates to permanent magnets.

. out the use of a binding agent, for example, of

a resinous or similar material.

It has been proposed in shaping magnets of I the type above described to cast the molten binding agent containing the finely divided magnetic material in suspension. Where a binding other words, the energy content per cubic centimetre of the pressed magnet oi. finely divided material must be increased, and the remanence increased to obtain the necessary reduction in magnet cross section. a

The invention is based on the new discovery that permanent magnets of pressed finely divided material with or without the assistance of a binding agent can be given the most variable prop- 10 agent is not used it has been usual to press the erties by employing instead of a single finely l0 finely divided material in a shell of non-magdivided permanent magnetic material, two or netizable material. more such materials of different compositions.

Permanent magnets of the type above described Both magnetic indices and other properties such have been found even with the employment of as temperature stability and the like may be high pressures in the pressing operation (4 tons usefully modified by alteration of the percentage 15 per square centimetre or over) to have a density proportions of the ingredients of the mixture.-

' only about 65% of that obtainable when the The essential condition for the attainment of magnetic material is in the coherent form obspecial eiiects by mixing together diiferent pertained by casting or rolling the magnetic metal. manent magnetic materials is that the coercive The consequence of the low specific density of force of the ingredients of the mixture should 20 magnets made from finely divided materials, be the same or similar. that is to say, its low volumetric fullness factor, Conveniently, only such materials are used in .is'generally a considerable lowering of the remwhich the coercive forces diiler by not more anence of the pressed magnet as compared with than 20% between one material and another.

a magnet of the same cross section and same If a material is used in which the coercive force composition in the coherent form obtained by differs by more than 20%, conveniently a special casting or rolling. At the same time, the curve heat treatment should be carried out ijor one or fullness factor as expressed by the equation (more. materials in order to bring nearer together BHmax the values for the coercive forces. The heat B H treatment consists either in heating and quenching or in the case of precipitation hardenable in comparison with the coherent material 18 alloys, to bring about precipitation hardening in lowered on an average to the extent of about any suitable manner 30%. The coercive force remains unaltered By suitable mixture of djflerent permanent Whether the magnet is n the coherent finely magnetic materials there is obtained, apart from divided n p s condition the advantages which are derived from the press- In of the ing process itself, such as easier preparation of the available energy per cubic centimetre of a complex shapes, the possibility of u efuny Permanent magnet of finely divided material ploying waste material from the preparation of compared with a permanent magnet in coherent permanent magnets f the most varying kind 40 wndition 0f the Same is without the necessity of a remelting process. Maably lower, a l'eductiims have been observed terials which are of little use in the pressing of a ut Consequently, for any given purprocess, in particular so far as their remanence D Dressed magnet finely divided material and their curve fullness factor is concerned, can must be made of considerably greater cross secbe improved by mixing one or more materials 4r tion than where 'a coherent magnet of the same which, t approximately t same coercive composition is used. This greater cross section for e have a higher remanence and higher is not Permissible for many PurPOses- Even the curve fullness factor, but which alone are of litwell-knowll iron-nickel-aluminium magnetic tle use for the preparation of pressed magnets io s wi h th h e er y content have not since they contain, for example, large amounts enabled the above-mentioned difilculties 170 be of expensive alloy constituents or they are not overcomeobtainable in sufilcient quantity in the form of It is an object'of this invention to produce waste mateflaL ma net consisting 0f finely divided materials Apart from the above-mentioned advantages p d n ape which to a greater exten with regard to magnetic values, by suitable se- 55 wlllbe e Suitable than those hitherto p lection of mixture constituents the temperature duced for a Var y Of ,P DO d n particustability of the finished pressed magnets can be lar in such cases in which increased cross section advantageously influenced. In the case of perand volume are undesirable owing to restrictions manent magnetic material with approximately .60 of space in the magnetic system concerned. In the same magnetic indices the separate materials 2 may, for example, have different temperature stabilities. If then a constituent of lower temperature stability be mixed with a constituent which has the property of temperature stability in a high degree, a pressed magnet is obtained which has a temperature stability which lies between the temperature stability properties of both constituents. The value may be advantageously influenced by the mixture proportions selected. X

In the following are given some suitable examples of carrying out the invention;-

Por the preparation of a permanent magnet from pressed finely dividedmaterial a nickel-aluminium-iron permanent alloy with a coercive force of about 500 oersted, a 'remanence of about 6,000 to 6,500 gauss and a curve fullness factor 1; equal to 0.36-0.40 is mixed with a nickel-cobaltiron permanent magnetic material with a coerclve force of 500 oersted, a remanence of about 9,000 gauss and a curve fullness factor 1 =0.50, for example, in the proportion of 1:1. The pressed permanent magnet so obtained shows the following V8.1l1BS1-3r about 4,450 gauss; He about 500 oersted; a about 0.31;

BHmax about 28,000 ergs/cm. Of course, it is possible to use other mixture proportions than 1:1 and thereby attain an extensive modification of the above-mentioned magnetic values.

In the employment of nickel-aluminium-iron for permanent magnetic alloys, materials can also be mixed which have alower coercive force, for example, 275 oersted in which the remanence comes to 10,000gauss. This is the case with cobalt-molybdenum-iron permanent magnetic alloys. In order to be able to mix such materials with nickel-aluminium-iron permanent magnetic materials, it is necessary to modify the coercive force of the latter by a special heat treatment consisting of heating and quenching, so that it also has close upon 275 oersted. In consequence of this heat treatment, the magnetic material has a remanence of 8,000 to 8,500 gauss. The curve fullness factor n for the heat treated nickel-aluminium-iron material comes to 0.5-0.6. with a mixing proportion of 1:1 the above mentioned material gives a permanent magnet with the following valuesz-B: 5550 gauss; He 275 oersted; 1 0.36;

BHrnax 81' 22,000 erg/cm Carbon chromium cobalt iron permanent magnetic alloys and cobalt-molybdenum-iron alloys have with suitable composition mainly the same magnetic indices, for example, both alloys have a coercive force of about 275 oersted, a

remanence of 9,000 to 10,000 gauss. Carbon-chromium-cobalt-iron alloys have the undesired property of being sensitive to temperature influences while the precipitation hardenable perwere not suitable on account of space and reasons of construction.

What I claim is:-

1. Permanent magnets consisting of compressed finely divided magnetic metal alloys, the finely divided material consisting of a mixture of a plurality of different permanent magnetic metal alloys in the finely divided state, the difierence between the coercive forces of which is not substantially greater than 20%. v

2. Permanent magnets as claimed in claim 1, wherein the finely divided material is united with the aid of a binding agent.

3. Permanent magnets consisting of com so pressed finely divided magnetic metal alloys, the finely divided material consisting of a mixture of a plurality of different permanent magnetic metal alloys in the finely divided state, wherein a part of the permanent magnetic materials has' a high remanence and high curve fullness factor ands part has a low remanenceand low curve fullness factor, both parts having approximately the same coercive force, the diiference between the coercive forces being not substantially greater than 20%.

4. Permanent magnets consisting of compressed finely divided magnetic metal alloys, the finely divided material consisting of a mixture of a plurality of different permanent magnetic metal alloys, wherein the permanent magnetic materials have the same coercive force and remanence, but differ from each other in their sensitivity to temperature infiuences.

5. A process for the preparation of finely divided permanent magnetic metal alloys for the production of permanent magnets by pressure, characterized in that a plurality of permanent magnetic metal alloys of differing coercive forces are employed, wherein before mixing one or more of the constituent materials is submitted to a" heat treatment for the purpose of equalising the coercive forces, the said heat treatment consisting of heating and quenching the material; and thereafter the constituents are intimately mixed together.

6. A process for the preparation of finely divided permanent magnetic metal alloys for the production of permanent magnets by pressure, characterized in that a plurality of permanent magnetic metal alloys of differing coercive forces are employed, wherein before mixing one or more of the constituent materials is submitted to a heat treatment for the purpose of equalising the coercive forces, the said heat treatment consisting in a precipitation hardening process; and thereafter the constituents are intimately mixed together.

7. A process for the preparation of finely divided permanent magnetic metal alloys for the production of permanent magnets by pressure, characterized in that a plurality of permanent magnetic metal alloys of differing coercive forces are employed, wherein before mixing one or more of the constituent materials is submitted to a heat treatment for the purpose of equalling the coercive forces, and thereafter the constitucuts are intimately mixed together.

ZUMBUSCH.