US2121799A - Process for making cast permanent magnets - Google Patents

Description

Patented June 28,

PROCESS FOR MAKING OAST PERMANENT 'MAGNETS Hugh A. HowelL-Berwyn, 111., animal to es, Chicago. Ill.

No Application June 29, 1937,

' Serial No.1 51,029

8 Claims. (01. 15-27) This invention relates to cast permanent magnets and more'partlcularly to a new process for their fabrication.

It is one of the objects of the present invention tov provide a method of making castv magnets easily and cheaply without resource to orthodox foundry methods, materials and equipment.

This invention relates particularly to the vari 'ous new magnet alloys containing iron, nickel, aluminum and other ingredients in vary percentages.

One of the important objects of this invention is the provision of a simple, economical method of producing cast alloys which can be later readily magnetized and which, on account of the I method of manufacture, will acquire and possess a highdegree of magnetic power.

A further object of the invention is the provision of a magnetic alloy which eliminates the necessity of annealingor aging so far as the final product is concerned, particularly inthat the super-heating, which accompanies the process of manufacture, produces a product which, when cooled, is practically automatically normalized.

My new process permits the making of cast magnets cheaply; and quickly, either in the shop or laboratory, without theme of a furnace or the conventional molding equipment necessary in a foundry where small castings are made.

The new features which I believe to be characteristic of my invention are set forth in the followingspeciflcations and particularly in the appended claims. 7

My invention will be best understood from a reference to the well-known chemical reaction between iron oxide and aluminum based on .the equation FezOa+2Al=2Fe+Ala0a Iron oxide and metallic aluminum in a properly divided state, mixed inabout the proportions of the foregoing equation, will react when properly ignited in such a way that the oxygen in the iron oxide is released and combines with the metallic aluminum to form aluminum oxide or slag, setting free the iron. The combustion is started by igniting a the-mixture at one spot and continues throughout the entire mass without the use of any other heating agency and results in super heated liquid iron and slag. The completereaction is completed in less than one half minute, creating a temperature in the neighborhood of 5000 F. The liquid iron produced represents one half of the original mixture by weight and one third by volume. The foregoing chemical reaction was first observed in 1857 by Friederich Woehler, the discoverer of aluminum.

In fabricating magnet alloys with my new process, I mix iron oxide in the proper physical state with aluminum, nickel or other metals in a divided and commercially pure state in an ordinary graphite crucible. I ignite this mixture with a small electric arc produced in any convenient manner. While the chemical reaction is taking place, Iagitat the mixture by rocking and twirling the crucible, while holding in an upright position in order to cause the superheated slagto freeze or adhere to the sides of the crucible. After the reaction has beencompleted, and before the liquid iron has had time to solidify, I pour all but the slag into an unheated carbon mold built up of several parts. Immediately after the casting has solidified, I remove it from the mold to cool naturally in the open air.

The cast material may be magnetized in a suitable manner either in one piece or after having been cut or broken into separate parts. Further machining, shaping and finishing may also be accomplished either before or after magnetizing.

I make my molds of pre-fabricated carbon sections, the number of sections depending upon the size and shape of the magnet and the amount of detail desired.

Cores and even parts of the mold can also be made of a mixture consisting of graphite one part and fine molding sand, two parts, with any good core binder. I fire all core and mold parts to remove water and carbonize. the binder; I

' have made as high as one hundred castings from Parts byweight. Iron oxide (scale)approximate1y 40 Fine commercially pure aluminum shot-approximately 15 Fine nickel shot-approximately 10 with above mixture and variations of same, I have poured castings weighing as little as five 50 grams, the only equipment necessary being a pair of tongs, a small crucible and a suitable igniting device.

With a mixture consisting of 40 grams of. iron oxide, 15.grams of aluminum shot and lo grams I the magnetic properties of the nickel-aluminumiron family of alloys. In fact, others have claimed that the addition of a certain amount of cobalt, chromium, copper, vanadium or manganese, etc. gives improved characteristics to the alloys.

I have not observed any marked improvement by special heat treatment of magnets made by my method, therefore heat treatment does not form a part of my process. I

The mixture described, consisting of about 40 grams of flake iron oxide, 15 grams of shotted aluminum and lograms of nickel will, after the chemical reaction is completed, produce about 35 grams of magnet alloy with approximately the following analysis and characteristics:

It will be noted that when the crucible is whirled, the liquid slag, which will not mix with the metal and evidently has a higher melting point, freezes or solidifies in a thin strata on the sides of the still relatively cool crucible so that when the thermic action is completed, the liquid metal is easily poured out of the crucible, there being absolutely no slag in the pour. After the crucible has cooled to about 400 F. or lower, the layer of slag clinging to the sides and bottom of the crucible will drop out by simply inverting the crucible. It may sometimes be necessary to tap the bottom of the crucible with a wooden mallet. In all cases, the slag formation drops out in a one-piece cup shape.

It will also be observed that the cooled magnet alloy will, under practically all conditions, retain a silvery white 'untarnished finish, especially if carbon molds are used. The accuracy of castings seems to be limited only by the design and tolerances in the mold.

Alloys, when made with this process and poured soon enough after the chemical reaction is completed, will be. superheated and very liquid, as comparedwith ordinary foundry practice. I have filled in cavities in carbon molds resulting in fins over one inch square and less than .010 inch thick-proving the fluidity of alloy.

, I am aware that many changes may be made in the ingredients and numerous details in the process varied throughout a wide range without departing from the principles of thisinvention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than as necessitated by the prior art.

What I claim as new in the fabrication of permanent magnet alloys and desire to secure by Letters Patent of the United states is:

l. The method of making a permanent magnet alloy consisting substantially of mixing by weight 30 to 50 parts iron oxide, 10 to 20 parts aluminum parts of flake iron oxide, to 25 parts of shotted aluminum, and 2 to 20 parts of shotted nickel, igniting said mixture in a crucible, whirling the crucible to cause slag to solidify on sides of crucible, and pouring resultant liquid metal into a carbon mold immediately after chemical action is completed.

3. The method of making a permanent magnet alloy consisting substantially of mixing by weight 30 to 50 parts of flake iron oxide, to 20 parts of fine shotted aluminum and 5 to parts of fine shotted nickel; pouring this mixture 'in a graphite crucible and igniting said mixture; agitating with a whirling motion during chemical reaction tofreeze liquid'slag to sides of crucible and pouring resultant liquid metal into a carbon mold after combustion is completed, removing the solidified casting 'and allowed to cool in air.

4. The method of making a permanent magnet alloy consisting substantially of 30 to 50 parts of iron oxide and 10-20 parts nickel and 10-20 the, sides of the crucible, and then magnetizing the casting.

6. A method of making a magnetic alloy, comprising mixing fiake iron oxide, aluminum and nickel in a crucible, igniting the mixture, centrifuging out the slag while the thermic reaction is taking place and pouring the molten metal into molds.

7. A method of making a magnetic alloy, comprising mixing iron oxide, aluminum and nickel in acrucible in such proportions as to yield a final composition containing approximately iron 60%, nickel 30%, and aluminum 10%, igniting the mixture, separating the liquid from the slag by centrifugal action and pouring the molten metal into molds.

8. A method of making a magnetic alloy, comprising mixing iron oxide, aluminum and nickel in a crucible in such proportions as to yield a final composition containing approximately iron 50 to 70%, nickel 20 to 40%, and aluminum 8 to 15%, igniting the mixture, centrifuging out the slag and pouring the molten metal into molds.

HUGH A. HOWELL.