US2211311A

US2211311A - Heat treating apparatus

Info

Publication number: US2211311A
Application number: US257177A
Authority: US
Inventors: Adolph F Bandur
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1938-02-25
Filing date: 1939-02-18
Publication date: 1940-08-13
Anticipated expiration: 1957-08-13

Description

Aug. 13, 1946. A BANDUR 2 211 311 HEAT TREATING APPARATUS I Original Filed Feb. 25, 3.939

Patented Aug. 13, 1940 HEAT TREATING APPARAT S Adolph F. Bandur, Berwyn, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Original application filed February 25, 1938, Serial No. 192,485. Divided and this application filed February 18, 1939, Serial No.' 257,177

3 Claims.

This invention relates to heat treating apparatus and more particularly to apparatus for the heat treatment of finely divided magnetic ma terial suitable for use in insulated dust cores, and is a division of my copending application Serial No. 192,485,'fi1ed February 25, 1938. v

In the manufacture of insulated-dust magnetic cores the magnetic metal or alloy is usually cast in an ingot and pulverized to the required fineness on suitable apparatus, after which the particles are coated with insulation and compressed into required shape. Because the pulverizing action produces internal stresses in the particles which detract from their magnetic properties, the particles are annealed before they are incorporated in a core. It has been customary to anneal the dust in a conventional sealed pot and, as the dust tends to sinter during this operation,

' it has generally been necessary to regrind the annealed material before use which results in the restoration of objectional stresses therein.

An object of this invention is the provision of improved heat treating apparatus for producing finely divided magnetic material possessing magnetic, electrical and physical properties which are highly desirable in electrical signalling equipment, especially in cores for loading coils in telephone circuits.

In one embodiment of the invention comminuted magnetic material in a plurality of shallow trays supported at spaced intervals in a ventilated container is subjected to a heat treating cycle in a furnace. A cover on the container has a vent in its central portion through which gases gener- 35 ated by the magnetic material during one portion of the cycle escape from the container and through which outside air is admitted to the container during another portion of 'the cycle.

The incoming air passes over a sheet of hot 40 iron which removesoxygen from the air. With this procedure and apparatus the dust is effectively annealed without sintering, which precludes regrinding, and the treated dust is more adaptable to subsequently applied insulation than 45 previous materials, which enables the production of cores having higher permeability values.

This apparatus is especially suitable for treating nickel-iron magnetic alloys of the permalloy type. For convenience the invention will be described in detail as applied to that material, in conjunction with the appended drawing, in which Fig. 1 is an elevation in section of an apparatus for the heat treatment of magnetic dust embodying certain features of the invention, and

(Cl. 263-49) I Fig. 2 is a sectional view of Fig. 1 taken on the line 2--2'.

A measured quantity of the magnetic material in the form of finely divided particles or dust I0 is placed in a shallow fiat-bottomed tray I I 5 or pan having sides extending at an angle of about 45 to the plane of the bottom. Inside the tray and welded or otherwise secured to the bottom thereof .are four V-shaped supports it, a conveniently formed from strip steel. Each sup- 1o portis mounted-in the tray with the'two legs of the V extending along the bottom of the tray and the flat top surfaces of the legs are positioned about below the .top rim of the tray in a plane parallel to the tray bottom. The tray can 15 be made of sheet metal and a low carbon steel gives good results.

The dust is spread evenly in the tray to a depth governed by the sintering tendency of the particular material under treatment. Sintering is a function of temperature and pressure, which vary with the composition and particle size of the dust, and in each case the depth of the dust in the tray is restricted to avoid a fusing pressure on the bottom strata of dust in the tray at the applied temperature. For permalloy dust of 120 mesh size a depth of about oneinch is satisfactory and the optimum value for other materialsis readily determined experimentally.

A number of the loaded trays are placed in a so thick walled container 13 or box of rectangular shape. The number of trays in each container is based on handling convenience, but it is advantageous to treat a substantial quantity of dust in a single container to provide material of uniform quality. The lower tray rests on the fiat container floor and the upper trays are successively positioned on the four supports in the adjacently lower tray. On the Supports in the top tray is placed a rectangular sheet of iron 4o l4 which extends over the entiresurface of the dust in the tray and extends closely to the tray edges on all sides. Y

After the trays and sheet iron are positioned in the container, a fiat cover I5 is placed on the container and its edges are sealed thereto with loam [6 or other suitable medium in a continuous channel I l at the top of the container into which a peripheral flange ill on the cover extends to provide an efiective seal. At the approximate center of and extending through the cover is a vent l9 about one-eighth inch in diameter providing an opening into the container.

The assembled container is placed in a suitable furnace (not shown) and subjected to a prescribed heat treating routine. For the treatment of the certain types of permalloy dust the container is heated to a temperature around 850 C. and maintained at that temperature for about one hour. During this period of heat application an internal pressure is built up in the container due to the development of certain gases generated by heating of the dust. These gases escape from the container through the cover vent and burn in a tapering flame at the outside of the cover.

After the completion of the heating cycle the container and contents are cooled at a rate not exceeding 10 C. per minute. During this cooling period the gases in the container contract in volume, and the current flow is consequently reversed, causing air to enter the vent into the container from the furnace chamber. It is desirable to prevent oxidation of the hot dust during this interval and this is accomplished by removing oxygen from the incoming air by means of the heated iron sheet over the top tray, and the heated trays. Before reaching the dust particles in the pans the air passes through a labyrinth of hot iron formed by the sheet and trays. The hot iron has a high affinity for oxygen which causes deoxidation of the air and prevents oxidation of the dust. To maintain the full deoxidizing eifectiveness of the labyrinth the trays are cleaned at suitable intervals to remove any surface oxide and the iron sheet is cleaned or replaced periodically.

At the termination of the cooling cycle the dust is removed from the trays and the particles are coated with suitable insulation such as the mixture of magnesium silicate, sodium silicate and magnesium hydroxide disclosed in applicants Patent 2,105,070 after which the insulated particles are compressed at high pressure into the form of a core.

Magnetic particles treated in the described apparatus exhibit new and improved properties that are valuable in insulated dust cores. Formerly, when the dust was heat treated in a sealed pot any gases generated by heating were largely reabsorbed during the cooling period. By eliminating these gases and cooling the dust in deoxidized air as provided in the present disclosure a dust is produced that requires less insulation when incorporated in a core. Apparently the described treatment imparts to the particles 2. new capacity to receive and retain a thin coating of insulation. Certain types of cores made with permalloy particles treated in this apparatus required 10% less insulation than dust treated by old methods for equivalent core service. Because of the smaller percentage of insulation present, the new cores have higher permeability values than the old structures which enhances the utility of the cores when they are used in loading coils and similar apparatus. v

The described apparatus can be used for heat treating various types of magnetic material and modifications of the apparatus specifically disclosed herein can be readily adapted to a variety f materials to supply new and useful properties thereto. It is, therefore, to be understood that the invention is restricted only by the scope of the appended claims.

What is claimed is:

1. Apparatus for heat treating finely divided magnetic particles to improve the magnetic properties of the particles comprising a container, a plurality of individual trays superimposed at definitely spaced intervals in the container and each containing approximately the same quantity oi magnetic particles to be heat treated, a cover sealed to the container and having a vent aligned with the central portion of the superimposed trays, and a sheet of iron in the container above the top tray, said sheet being spaced from the vent and from the particles in the top tray and extending over the surface of the particles in the top tray.

2. In an apparatus for heat treating finely divided magnetic metal for the purpose of improving the magnetic property of the metal, a container of substantially rectangular shape, a plurality of superimposed trays in the container for supporting the finely divided metal, each tray comprising a fiat bottom, side walls extending at an inclined angle to the bottom, and a plurality of supports secured to the tray bottom for positioning the adjacent upper tray, a cover for the container having a vent in its central portion, and a metal sheet on the supports in the top tray, the container, trays, metal sheet, and supports being dimensioned to provide a labyrinth for the passage of air flowing from the cover vent to the finely divided metal in the trays.

3. In an apparatus for heat treating finely divided magnetic metal for the purpose of improving the magnetic properties of the metal, a container of substantially rectangular shape, a plurality of superimposed sheet metal trays in the container for supporting the finely divided metal,

each tray comprising a fiat bottom, side walls extending at an angle of about 45 to the bottom, and a plurality of members secured to and projecting above the tray bottom with their top surfaces in a plane slightly below the top edge of the tray side walls for supporting the adjacent upper tray, a cover for the container having a vent in its central portion, and a metal sheet supported on the members in the top tray and extending over the finely divided metal in the tray, the container, trays, metal sheet, and members being dimensioned to form a passage for conducting air from the cover vent to the finely divided metal in each of the trays.

ADOLPH F. BANDUR.