US1947274A

US1947274A - Permanent magnet and method of making it

Info

Publication number: US1947274A
Application number: US654764A
Authority: US
Inventors: William E Ruder
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1933-02-01
Filing date: 1933-02-01
Publication date: 1934-02-13
Anticipated expiration: 1951-02-13

Description

Patented Feb. 13, 1934 1 UNITED STATES PATENT OFFICE 1,941,274 v PERMANENT moms-r AND ua'rnon or MAKING rr William E. Ruder, Schenectady, N. 2., assignor to General Electric Company, a corporation of New York No Drawing. Application Februaryl, 1933 Serial No. 654.764

6 Claims. (Cl. 1'I521) The present invention relates to magnetic maemployed. For example, when the casting is terial and more particularly to cast alloy permaheated to a temperature of 600 C. the heatin nent magnets and to a method of making them. period may be about five hours, while for a tem- It is one of the objects of the present invention perature of 650 C. the same results may be 5 to provide a permanent magnet, composed of obtained in about half an hour. The product so relatively cheap materials, which may be fabriobtained after heating the casting in the 600 to bated easily and cheaply and which has desirable 700 C. temperature range etches entirely diil'ermagnetic qualities. ,ent from the product obtained after heating the The novel features which are characteristic of casting at about 1000 C. The explanation of 1 my invention are set forth with particularity in this is that heating in the 600 to 700 0. range the appended claims. My invention however will affects precipitation of an age hardening combest be understood from reference to the followpound in thecasting. This hardening compound ing specification. is composed of particles of sub-microscopic size.

My improved magnet material generally con- I have obtained the most satisfactory results 15 sists of a mixture of iron, nickel and aluminum with alloys consisting of 10 to 12% aluminum, 7 in which the iron may comprise from about 60% about 20% nickel and the remainder iron. Age to 70% of the composition, the aluminum from hardened alloys of this composition have a coabout 6% to about 15% and the nickel from about ercive force varying from about 330 to 350 gilto about 30%. The ingredients of the alloy berts per centimeter, a residual varying from 20 in desired proportions are melted in any suitable about 7100 to 8500 gauss, and a maximum energy 7 furnace and then poured into castings. To obor BHmBX. varying from about one to one and tain the most satisfactory magnetic qualities in one-half million. For the same maximum enthe alloy the casting preferably should be cooled ergy the relation of the coercive and residual may from the liquid to the molten condition very be varied with variations of the heat treatment 5 quickly. This may be accomplished by casting and composition. For example, a composition the metal in a chill mold. If desired, however, 2. containing nickel gives a lower residual, sand mold may-be employed. Under the latter other things being equal, and a higher coercive circumstances it will be found desirable to sprinforce than a composition containing 20% nickel, kle water on the mold immediately after the castwhile prolonging the time or increasing the teming has been poured and to pull the casting out perature of the treatment, increases the residual 5 of the mold as soon as it has solidified sufliciently andreduces the coercive force. to permit such action. If desired, the cover of If the cross section of the casting is very small, the sand mold may be removed and the casting for example x it will be found that its exposed to a strong air blast. magnetic qualities in the cast condition are about Since difference in size and necessary variaas good as the magnetic properties of larger cast- 0 tions in casting conditions for various shapes ings which have been age hardened according to makes it difiicult to get uniform results on all my improved process. However, although castmagnets of the same compositiomit will generalings of very small cross sections have desirable 1y be found desirable to give the alloy a heat magnetic qualities in the as cast condition, it

treatment after the casting operation to obtain will nevertheless be found desirable to age harden 5 uniform results. This may c mprise heating the all castings. This will be apparent when it is casting at a normalizing temperature in the considered that castings having a cross section neighborhood of 1000 to 1500 C. This is merely of x are improved by the aging process.

a corrective h treatment and is u l y 41- In general, the magnetic qualities of castings of 45 plied until the e tir Castlng s heated to the relatively small cross section are better than the normalizing temperature- After h r a m nt magnetic qualities of castings of relatively large he casting is r p Cooled Preferably in cross section. This is apparently due to the ing air or oil. When the casting has been cooled rapidity t which t small castings solidity to the desired extent, i. e. about room temperafrom t hquid t t 5 -ture usually or to the temperature of retreatment, While I prefer to employ only iron, nickel and it is given a further heat treatment which comaluminum as the ingredients of my improved prises he in h ing to a temperature bealloy the presence of minor impurities does not tween about 600 C. and 700 Q. The time at materially affect the magnetic properties of the which the casting is held in this temperature alloy. If desired, a few per cent of chromium,

55 range may vary according to the temperature for example about 3 to 5%, may be present in the alloy. However, the presence of chromium is not desirable since it does not improve the magnetic properties of the alloy and does in= crease its cost. 1

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An age hardened magnet consisting substantially of about 6% to aluminum, about to 30% nickel with the remainder iron.

2. An age hardened magnet consisting substantially of 10% to 12% aluminum, 20% to nickel with the remainder iron. I

3. An age hardened permanent magnet con sisting of about 10% aluminum, about 20% nickel and about 70% iron.

4. The method of making a permanent magnet cast alloy consisting substantially of about 6% to 15% aluminum, about 20% to nickel, and the remainder iron, which comprises melting the ingredients of the alloy, casting the alloy, quickly cooling the alloy from the liquid to the solid state and aging the alloy at a temperature varying from about 600 to 700 C.

meagre 5. The method of making a permanent magnet cast alloy consisting substantially of about 6% to 15% aluminum, about 20% to 30% nickel, and the remainder iron which comprises melting the ingredients, casttng the alloy. quickly cooling the alloy from the liquid to the solid state, heating the casting at a temperature between 1000 C. and 1500" C. and cooling and then heating the casting at a temperature below 1000 C. but high enough to cause precipitation hardness thereof.

6. The method of making a permanent magnet cast alloy consisting of about 6% to 15% aluminum, about 20% to 30% nickel and the remainder iron which comprises melting the ingredients of the alloy, casting the alloy, quickly cooling the alloy from the liquid to the solid state and aging the casting at a temperature below 1000 C. but high enough to cause precipitation hardness of the alloy.

WILLIAM E. RUDER.