US1839518A - Method of forming tungsten carbide - Google Patents

Description

Jan. 5, 1932- G. w. WOODS ET AL METHOD OF FORMING TUNGSTEN CARBIDE Filed Nov 7, 1929 GWWOODS V R HBIWOODS [1:1 70 5 :ITTOR/VEY Patented Jan. 5, '1932 UNITED STATES PATENT OFFICE GORHAM W. WOODS AND HENRY B. WOODS, OF HOUSTON, TEXAS, ASSIGNORS TO HUGHES TOOL GOMIANY, 01F HOUSTON, TEXAS, A CORPORATION OF TEXAS METHOD OF FORMING TUNGSTEN CARBIDE.

Application filed November 7, 1929. Serial No. 405,391.

Our invention relates to a method of form- 'ing tungsten'carbide and the like, and pertains to the proper melting and cooling of the charge so as to produce the best quality of tungsten carbide for the purpose to which th carbide is to be applied.

Tungsten carbide is now commonly applied to tools where a hard surface is desired to resist abrasion. For this purpose, the carbide should not be too brittle and should not contain too large a proportion of carbon.

It is an object of the invention to so treat the tungsten carbide that the molten charge will not take up an excess of carbon over the desired amount.

We also desire to cool the carbide quickly so as to obtain a proper grain and consistency to the finished product.

The invention lies in the process of treating the materials in the obtaining of the final product, and the salient features of the invention will be set out in the specification which follows. i

In the drawing herewith is a front view largely in section of an apparatus which may be used to carry out the invention.

This application is a continuation, in part, from the co-pending application of Gorham W. Woods, Serial No. 333,501, filed January 18, 1929. It differs. therefrom in the addition of more effective cooling means.

The ingredients consisting of the proper proportions of tungsten and carbon are placed in a crucible 1 of graphite or other heat resisting material. Said crucible may be of cylindrical form, open at its upper end and closed at its lower end, except for a small discharge opening 2. The walls of the crucible are thickened at the lower end, and the inner wall thereof is tapered or sloped downwardly at 3 to direct the molten charge to the outlet. By making the walls thicker the electrical resistance is decreased about the opening 2. The crucible has a vent opening 5 adjacent its upper end for gas.

The top of the crucible may be closed by a plate 6 also of graphite. The plate contacts with an electrical conductor 7 arranged to be cooled by the circulation of a. cooling liquid therethrough. Said conductor forms an electrode of hollow construction, the upper end of which is connected to a heavy conductor 8 of copper, which forms part of an electrical circuit. The electrode 7 may also be of copper and adapted to be filled with the cooling liquid circulated therethrough from pipes 9 and 10' leading to some source of liquid under pressure or to a circulating pump, not shown. A weight 11 is employed to hold the electrode 7 in firm contact with the cru-- cible.

The crucible is supported upon a plate 12 of graphite resting upon a mold 14. Said plate 12 has a central opening 13 below the opening 2 in the crucible to allow the dis charge of the molten tungsten carbide to the mold. The mold chamber 15 receives the metal, and,as this mold also forms an electrode, its lower end is'connected to an electrical conductor 16.

The mold is preferably made of copper, or other good electrical conductor, and is water cooled on the outside thereof by forming a liquid chamber 17 about the, mold chamber.

The liquid chamber is connected by pipes 18.

drawing will be melted under the heat of the carbide, which is about 2800 C., and will be vaporized to some extent, thus, also adding to the cooling effect of the salt bath.

In operation, the tungsten and carbon in powdered form are introduced into the crucible, and the crucible then heated by passing the electrical current through the walls of the crucible which are heated through the resistance of the graphite to the passage of the current. melted when the temperature of fusion is The contents of the crucible will be from the vent subsides, the current will be turned on more fully and the heat is rapidly increased. The opening 2 at the lower end of the crucible is closed by some unmelted tungsten carbide at the vbeginning of the ptill hill

oration, and as the material at the lower end of the crucible heats more slowly, due to the thicker walls, the plu of carbide in the opening will melt last an will release the charge, as soon as the said charge has been completely fused.

The molten carbide is received within the mold chamber 15 which is cooled by the circulation oi. cooling fluid. in the container l7. Also the salt 20 in the mold will melt, and thus serve tofurther cool the carbide. By the use of the salt, the rapidity of cooling of the charge is materially increased, thus add ing to the hardness of the i'inished product.

There is usually a small amount oi tungsten carbide remaining in the opening 2 after the charge has passed to the mold, and this melts with the next charge to allow the contents to be discharged. W e contemplate filling the opening 2' each time with carbide or some material of the same or slightly higher melting point, so that the charge will he automatically released as soon as it is completely melted, and before it is allowed to comloine with carbon gas irom the crucible. If the molten material remains too len the crucible the product will show graphite ilalres due to carbon included from the cruci" his and to decomposition the carbide which has formed.

The advantageol the invention lies the convenient operation of the device who the charge is quietly and uniformly me and automatically discharged heiiore remained too long in a molten state in he crucible. The rapid cooling at the also results in the host quality of product.

What We claim as new is:

1. A method of manufacturing tungsten carbide comprising pulverizing the ingredi ents, placing them in pulverized form into a crucible in the presence of carbon, melting the charge, discharging the same as soon as it is completely melted, and immersing the melted carbide in a liquid bath.

2. A method of manufacturing tungsten carbide comprising mixing a charge of inredients in the desired proportions, melting t 0 charge, quickly discharging the molten material after it has been com letely melte immersing the char e in a bat of salts, an rapidly. coolin sai char e.

3. A method of menu acturing tungsten carbine comprising mixing a charge of inglredients in the desiredproportions, melting t e charge, quickly discharging the molten signatures.

GORHAM W. WOODS. HENRY B. WOODS.

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