US1940308A - Method of making carbides - Google Patents

Description

Dec.'l9, 1933. F. c. KELLEY 1,940,303

METHOD OF MAKING CARBIDES Filed Sept. 26, 1928 Inventor: Floyd C'Kelleg,

I 14% His Attorney.

Patented Dec. 19, 1933 UNITED STATES PATENT OFFICE METHbD OF MAKING CARBIDES Floyd 0. Kelley, Schenectady, N. Y., mantra General Electric Company, a corporation of New York Application September 26, 1928 Serial No. 308,565.

11 Claims (CL 23-408) In making hard metal compositions, such as 16 quantity of auxiliary metal of lower melting point than the carbide, for example cobalt, it is desirable to provide a product of uniform quality. This can be accomplished only by controlling accurately the quantities of the various constituents 20 entering into the composition. While it is an easy matter to control the tungsten and cobalt content of such compositions, it is diflicult to control accurately the carbon coritnt of the carbide by methods heretofore employed.

carbide which is to be employed in the manufacture of hard metal compositions, such as described in the Schriiter patent, to combine from 5.5% to 6.2% of carbon with the tungsten. In

80 making the carbide, it has been customary to effect the carbonization of the'tungsten by means of powdered carbon placed with the tungsten in an open carbon furnace, an excess amount of powdered carbon being placed in the carbon hold- 86 er. During the carbonization process, a certain amount of powdered carbon is burned out. However, it is diii'icult to determine when the proper amount of carbon has been removed and as a result the carbide oftenicontains less than 5.5%

40 or more than 6.2% of carbon.

In carrying out the present invention, the tungsten and carbon in powderedform and in definite sten. Tools, dies and other materials made from such a product are of unvarying quality.

-- The novel features which I believe to be characteristic of my invention are set forth with partljcularityintheappendedclaims. Theinventicn It is preferable in the manufacture of tungsten itself, however, will best be understood from reference to the following specification when considered in connection with the accompanying drawing, in which the single figure shows partly in elevation and partly in section, an electric furnace 00 whereby my invention may be carried into effect.

Referring more particularly to the drawing, I have indicated at 10 an electric furnace comprising a steel casing 11 and a concentric coaxial alumina tube 12, the latter being surrounded by a molybdenum heating coil 13 connected at its ends to binding posts 14 and 15 which may be connected to a suitable source of energy, not shown. The space between the casing 11 and the outer surface of the tube 12 is filled with suitable insulating material such as powdered alumina 16.

Hydrogen is supplied to the interior of the casing 11 through inlet pipes 17 and 18 so that the molybdenum heating coil and the outer surface of tube 12 are completely surrounded at all times by an atmosphere of hydrogen. Tube 12 permits the passage of hydrogen therethrough. Hydrogen is also supplied at one end of the tube 12 from a pipe 19 and through valve 20. The hydrogen flows through the tube 12 to the opposite end thereof where it is burned as indicated at 21. A water jacketed chamber 22, having inlet and outlet water pipes 23 and 24, respectively, issecured to one end of the furnace 86 for a purpose which will be disclosed presently.

In carrying the invention into effect, tungsten and carbon in powdered form and in the desired proportions, that is, about 94% tungsten and about 6% carbon are placed in a carbon receptacle 25 which is closed by a .carbon plug 26. The receptacle 25 is placed in the furnace 10 and heating current is supplied to the coil 13 while hydrogen is caused to flow over and around the receptacle 25. The powdered materials are 95 heated in this manner at a temperature above 1000 C. but below the melting point of the tungsten, for example about 1500 C. for about three hours, at the end of which time the tungsten is substantially completely carbonized and substantially no free carbon powder remains in receptacle 25. At the end of the three hour period, the circuit to coil-13 is opened, the hydrogen supply shut oil and the carbon receptacle pushed in the water jacketed chamber 22 where it is 7'." allowed to cool to room temperature. Thereafter a plug 27 may be removed from the water jacketed chamber and the receptacle 25 removed therefrom.

When in the manner shown, it no will be found that although the receptacle is nace at an elevated temperature but below the made of carbon, substantially none of it commelting point of said materiaLand in a hydro- -bines with the tungsten powder and that the gen atmosphere.

percentage of powdered carbon placed in the re- 2. The method of forming a carbide of a metal ceptacle originally does not vary more than one which comprises placing the metal and carbon, tenth of one per cent fromthe carbon content of each in powdered condition, in a closed recepthe finished product. Although I find it adtacle, the walls of which are porous to hydrogen vantageous to heat the powdered material to a and contain an appreciable quantity of carbon, temperature of 1500 C. for about three hours, and heating said receptacle in a current of hydroa lower temperature may be employed if desired, gen at an elevated temperature butbelow the although the heating period would be lengthened melting point of said metal for a period or time under such circumstances. Likewise the temlong enough to cause combination of the powperature may be raised above 1500 C. and the dered carbon and metal. heating period shortened somewhat. 3. The method of forming a carbide with an My explanation of the above action is that element of the tungsten group, which comprises Qthe hydrogen in passing through the carbon reheating said element and carbon in powdered ceptacle 25 combines 'with a certain portion of form at an elevated temperature below the meltthe carbon thereof to form a hydro-carbon gas. ing point oi! said element and in a closed carbon When this hydrocarbon gas comes in contact with receptacle while said receptacle is surrounded the'tungsten metal a combination'between the by an atmosphere of hydrogen. carbon in the gas and the tungsten metal occurs, 4. The method of forming tungsten carbide tungsten carbide being formed while hydrogen is which comprises placing about 93.8% to 94.5% liberated. The liberated free hydrogen in the tungsten powder and about 6.2% to- 5.5% carbon tube being in a very active condition,- combines powder in a carbon receptacle, closing said rewith the powdered carbon or the charge to receptacle and heating it to a temperature of about Q00 form the hydrocarbon gas. The hydrocarbon 1500 C. for about three hours in hydrogen. gas in the tube therefore remains in a condition 5. The method of forming tungsten carbide oi equilibrium with respect to the carbon at the which comprises placing approximately 94% temperature employed while effecting carburizatungsten powder and approximately 6% carbon tion of the tungsten. The reactions which take powder in a carbon receptacle, closing said replace may be indicated as follows: c eptable and heating it for an appreciable period nH+mC(gmphite of tube) QCmHn of time in an atmosphere of hydrogen at a tem- CmHnGn contact with W) mC+nH Hence mC+mW- mWC and nH+mC (in charge) CmHn etc.

until all tungsten has been carburized.

perature above 1000 c. but below the melting point or tungsten.

6. The method of iorming a carbide oi. an element of the tungsten group which comprises placing approximately 94% of said element in I powderedv form and 8% of carbon in powdered ess. The container in such a case should have low the melting point or said metal and for a While I have shown the use of a carbon re- .Iorm in a receptacle, the walls of which consist ceptacle, other porous receptacles containing an mainly of carbon, clomng said receptacle and appreciable amount of carbon in their-composiheating it for an appreciable period oi! time in 'tion may .be employed if desired. While such an atmosphe're'ot hydrogen at a temperature receptacles should permit diffusion of hydrogen above 1000 C. but below the melting point oi. said therethrough, they should not permit diifusion element.

at such arate that any hydrogen passing through 7, The method of forming a carbide or an the receptacle is uncombined with carbon. element oi. the tungsten group which comprises Although I have illustrated my invention in placizig approximately 94% of said element in connection with the formation of tungsten carpowdered form and approximately 8% of carbon hide, it is byno means limited to the formation i powdered form in a receptacle and heating of carbide or to this particular-carbide. For ext owderedmixture at an elevated temperap e, the invention may be appli d to material, ture but below the melting point of said element such as iron or steel which contains an appreciand in the presence 01. a hydro-carbon gas which able amount of carbon, when it is desired to anneal at that temperature is in a state of equilibrium such material without decarbonization. If such with respect to carbon.

material is enclosedin a wrought iron pipe 112- 8. The method 01 forming a carbide of a metal ptacle provided with closed pip balls and then which comprises placing a powdered composition heated to an annealing temperature in a hydrocomprising said metal and carbon in a closed gen furnace, it is found that the carbon content carbon tube and heating said closed tube in hy- 0! the nn aled meta is n h n ed by the pr drogen at a relatively high temperature but beenough carbon in its composition to combine period of time sumcient to cause combination with all the hydrogen which penetrates to the or said metal and powdered carbon. interior of the receptacle and walls should be 9 The method of forming a carbide of a metal thick enough so that the walls are never comwhich comprises placing a powdered composition pletely decarbonized during the annealing period, consisting substantially of said metal and car-' What I claim as new and desire to secure by bon a closed carbon tube. t e quantity of Letters Patent or the United States, is:-- powdered carbonbeins flicient to convert sub- 1. The method of heat treating solid material stmtlally all Said metal to & carbide QI Sald containing an appreciable quantity oi! carbon so metal and 1168191118 d o ed tube inahy fl as 'to prevent variation oi. the carbon content atmosphere at an elevated mp ra r but Jaethereof, which comprises placing in a Iumace a l the melting Point Of Sa d etal and fo BI.

closed receptacle containing said material, the period of time suflicient to au e co at n o walls or said receptacle containing'an appreci- Said metal wi Said car able quantity or carbon and being porous to' method f f minaa ar id o m t hydrogen, andheating thereceptacle insaid rurwhich pri e placing in a furnace a closed which comprises placing in'a furnace a closedcarbontubecontainingapowderedmixture consistingmainlyotsaidmetalandcarbomsaid carbon being present in such quantity that when combined with said metal substantially no free carbon will be present in said tube and heating' said closed tube in a'hydrogen atmosphere at a temperature above 1000 C. but below the meltin: point of said metal for a period of time sumcient to cause combination or said metal and carbon.

1 FLOYD O. KELLEY.

Images