US1704256A - Refractory article - Google Patents

Description

Patented Mar. 5, 19 29.

UNITEDOST'ATES PATENT OFFICE.

CHARLES FREDERICK LORENZ, OF EAST ORANGE, NEW JERSEY, ASSIGNOR '10 "WEST- INGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

REFRACTORY ARTICLE.

No Drawing. v Application filed April 24 This invention relates to a method of producing refractory ware and to the articles resulting from practicing such method.

An object of the invention is to provide a method of producing a reinforced refractory body. I

Another object of the invention is to produce a refractory body having comparative- 1y thin walls but possessing a relatively high degree of strength.

A still further object of the invention is to produce a hollow body, such as a crucible, having the necessary tenacity to withstand handling incident to its use.

Other objects will be apparent upon a reading of the following description.

It is well known that certain refractory bodies, especially hollow bodies composed of homogeneous metallic powder such as tungsten or the like, are of a fragile character and must be handled accordingly to prevent breakage.

The common method of making. these bodies is first to mold a metallic powder into a hollow member and then heat the molded body to a temperature at which the powder is sintered to produce a coherent mass. Refractorybodies of this character, commonly used as crucibles, lack the necessary amount of toughness or tensile strength to avoid rupture which often occurs through comparatively light impact with other bodies.

By the present method, a refractory body may be produced which is sufiiciently tena .cious to avoid rupture through handling when employed as a crucible or for any purpose for which it may be intended.

To produce a refractory body in accordance with my invention, I employ a tangled or entwined mass of wire which may be of tungsten, molybdenum or other metal. It is possible, with my method, to employ, any discarded or scrap wire, such as the residue commonly resulting in manufacture of certain electrical devices. A quantity of this vwire, which is often termed metallic wool, may be given any desired shape and positioned in a mold. Metallic powder, such as tungsten, is deposited in the mold until the interstices within and on the sides of the shaped wool are substantially filled. A suitable plunger is inserted into the mold and pressure applied until the intermingled or 1922. Serial No. 556,834.

,interlaced wire and metallic powder are compressed to form a compact mass.

Refractory bodies made according to my process may, for certain purposes, be found strong enough, after pressing, b reason of the embedded wire, to be hand ed without the necessity of sintering, inasmuch as the entwined wire gives considerable strength to the body. A body ma be produced without sintering and may e heated during a pressing operation to a degree suflicient to set the wire which otherwise might tend to oppose being compacted. A more intimate union between the wire and the powdered metal may, however, be obtained by sintering the mass after the pressing operation has been performed.

The present method isparticularly adapted for making a crucible which may have its walls composed of a layer or layers of metallic wool, such as tungsten and a metallic powder.

A crucible may be fproduced by depositing one or more layers 0 tungsten or other suitable wool upon the inner surface of a mold and a given quantity of a suitable metallic powder, such as tungsten, may be deposited within the mold. A. die or male member may then be inserted in the mold to press the powdered substance into .intimate contact with the wool or intermingled wire. The die is then caused to exert sufli'cient pressure upon the powder and wool to compress them into an adherent mass. The hollow body thus produced will have the wall thereof reinforced by the'wool and may be removed from the mold and placed in a sintering furnace, whereupon it attains greater strength by reason of the resultant more intimate association betwen the powdered substance and the wool through incipientfusion.

Heretofore, when crucibles were produced by compressing a powdered metal, great difficulty was encountered in transferring the partially finished crucible from the mold to the sintering furnace, because the crucible was extremely fragile.

A crucible made according to my process may be more safely and, consequently, more conveniently removed from a mold, inasmuch as the entwining reinforcing strands of wire practically constitute an internal fabric within the wall of the crucible and hold the metallic powder in place.

- in a mold together with the tungsten It will be appreciated that, by reason of this reinforcing net work of wrought material within the wall of a crucible the crucible will, after sintering, possess, in virtue of the inherent tenacity of the meta lic wire or a wool, sufiicient strength to resist, to a gfeat extent, the impact due to careless han- A wall of a refractory substance hav' substantially the equivalent of a fabricate interior and consequent relatively high ten:

sile strength is of advantage for other ur-.

poses than in the making of a crucible. or instance, an electrode of spherical or hemispherical shape ma .be desired. Ihave found that an electrode aving a thin wall is de-. sirable to meet certain conditions but was ve difficult to obtain before recourse was ha d to the present method of embodying a net work of wire within the wall to give it strengthto support/its own weight.

In practicing my method, I have found that, by placing a quantity of tungsten wool powder and a plying pressure during the application 0 sufiicient heat to set-wire, good results are obtained. A body is thus formed which may then be sintered in any desirable manner. I have also found that a convenient manner of temporarily associating the wire and tungsten or other powder previously to pressing, is to mix any suitable volatile blnder, such as cryolite of camphor, with the powder to form a pasty or plastic substance which will then flow into the crevices or interstices of the mass or wire under pressure.

Heat being applied during the pressing operation the cryolite or other binder is volatilize leaving the metallic elements in a compressed state. The molds for compressing the mass duringa heat treatment must necessarily be of a metal which will withstand the heat without. losing its strength or hardness at a temperature at which tungsten wire will set.

My process may also be practiced for the production of slugs used in the manufacture oftungsten wire, in which case, a quantity of tun sten powder and tungsten wool or scrap lament wire is united by the application of pressure in a suitable mold. The resultant slug has considerable strength and may be more readily handled for thesintering, swaging and drawing operation than slugs composed entirely of tungsten powder. In the manufacture of .these slu it may be desirable to obtain aslug for t e production of a filament wire containing a given amount of thoria to increase the resistance of the wire; in which case, a quantity of thoria powder may be addedto the tungsten powder during the production of the slu I t will also be evident that, by the present method, a refractory body may be shaped to -mass of wire or wool; for instance, it ma bedesirable to produce a target having a re atively high heat-conductive material incorporated therewith.

"It has been found diflicult heretofore, to produce an intimate union between certain substances such, for instance, as copper, having high heat conductivity and refractory bodies such as tungsten. [be reason being that a layer of oxide forms upon the tungsten and this interposed layer of tungstic oxide prevents the copper from adhering in a degree suflicient to provide a practical target.

By the use of tungsten wool, a target may be made by compressing a quantity of coppe powder and a layer or layers of t wool in a mold until the wder has I forced around the wire in t e manner above explained when tungsten powder is employed. In this case, however, it is preferable to provide a layer of tungsten powder, a layer of tungsten wool and a layer of copper powder; e tungsten wool being interposed between the layers of powder. Pressure may then be applied to force the powders disposed upon each side of the wire or wool therethrough. The tungsten portion of the body will offer high resistance and become heated to a point at which it will be sintered,

whereas, the copper portion of the body will rapidl conduct eat away at a sufficient rate to avoid its being heated excessively. If-desirable, the layer of copper may be of suflicientl greater mass than the tungsten wool, and t e conductivity of the copper will be relatively greater than that of the tungsten,

with a corresponding increase in the dissipation of heat. It may be preferable to rovide a cooling element, such as a water jac et,

in association with the copper portion of the body and thereby carry away the heat to avoid the vaporization of the copper to any reat extent during the time the tungsten 1S ein sintered.

A though the temperature of the copper may be raised to a point at which the copper melts, a mold may e provided to confine the molten-copper in contact with the tungsten wire so that, after the tungsten has been sintered and the entire bod cooled, the copper will be bound fast by t e integral portions ill thereof which lie between the strands of tungsten wire. Thus, the copper and tungsten are consolidated and produce a composite body for use as a target inlX-ray tubes or for other uses. It is obvious that, in place of the tungsten powder, a layer of other refractory powder may be used, or a layer of tungsten or nickel wire and a layer of copper or other material of relatively high heat conductivity may be found desirable. Thus, a composite body composed of elements of different atomic weights may be produced.

By means of my process, I may produce-a composite body of a given coeflicient of expansion by utilizing a metallic wool of a given coeflicient of expansion and uniting it by means of my method with a metal of a different coefiicient of expansion to obtain a slug or other body. A slug of the above character may readily be swaged and drawn with the result that a wire will be obtained of a predetermined coefiicient of expansion. The production of a body which will have a given coeflicient of expansion is particularly desirable in the electrical art as, for example,

that, although I have given certain specific methods embodying my invention and examples of articles produced thereby, it is to be understood that many variations may be made therein without departing from the spirit and scope of the invention.

What is claimed is 1. A crucible composed of tungsten powder sintered to tungsten wool.

2. A vessel composed of a metallic refractory powder sintered to a mass of metallic wool. V

3. A vessel composed of tungsten powder sintered to metal wool.

In testimony whereof, I have hereunto sub scribed my name this 22nd day of April, 1922.

CHARLES FREDERICK LORENZ.