US2113171A - Carbide material - Google Patents

Description

I memes 4 a v I 2,113,171 a 9 L UNITE-D STATES ,PATENT oar-"lea .Hugh 84 Cooper, Cleveland lull hi8, Ohio, assitnor to Cooper Products, Inc., Cleveland,

Ohio, a corporation of Ohio No Drawing. Application April e, 1936,- Serial No. 73,344 r 9 Claims. (CL 75-136) The present invention relates to a hard 'carput into the mixture in this case'is less than bide Zmaterial, especially a'hard tungsten car;- that desired in the final product. This adjustbide material, suitable for cutting tools, wire ment of carbon content varies with the particudrawing. dies, and the like, and to a method of lar dimensions of equip 9 8 1 nd h producing the same; exact relation between the original and theflnal 5 Tungsten carbideis known toexist in two forms carbon content has to be determined by trial. having 'the formulae, respectively, of WC and: After the powder has cooled it is rubbed in a WaC. I Of these two they first, WC, which has a mortar and is then ready to be pressed in a suittheoretical carbon content; of 6.12%, has the able die into the final form of die-or tool ,regreater hardness and suitability as a cutting tooi quired; A pressure of fifteen tons per Square 10 and die material. This form of tungsten carinch of p e s s ce o th e u ed isusua iy bide requires a bonding agent as it will not sinsatisfactory. After pressing, the shaped pieces ter together into a sumciently strong body when are placed on a tungsten carbide slab in a graphheated in pure form. Even when brought to ite cylinder and heated in a carbon tub'e resistor fusion it produces a porous and rather weak and furnace for about thirty minutes at about 2200 brittle mass. Heretoforetth preferred bonding C. to 2400 0., preferably 2300 C. Pieces treated. material has been cobalt added in'sufilcient quanin this way are then ready for use after suitable tity to form a% to 12% of the final product by grindin a shins to the exactsize req e W i h I Material made in the manner just described I have discovered that if the carbon content has a fine silky fracture and great strength and is reduced to about 5.5% the resulting material hardness. The modulus of transverse. rupture has novel and, unpredictable self-bonding qualiis about one hundred thousand pounds per. Square ties, and in additionit has great hardness and inch, and the hardness is from 1400- to 1800 strength suitablefor die and cutting ,tool ma- Brinell, as determined with a diamond point terial. With a carbon content of "5.5%, the maimpressor. 4 terial must necessarily consist of a mixture or The carbon content is quite critical and may 35 compound of WC and W, or WC and W2C, or not vary more than 35% from the preferred coni all three. So far I have not determined which tent of 5.5%. In fact if it is reduced by as little v s of these three possible'form's the material actuas say .15% (to 5.35%) the strength may drop ally takes, although an examination of, it by to one-half or less, and the hardness may drop M 'X-ray spectroscopy favors the theory that it below 1000. Increasing the carbon content by consists of a mixture of WC and W and thatthe the same amount (to 5.65%) has a similar effect excess tungsten acts as the binder and sinters and. in addition, in the final heating the matethe material together. Irrespective of which of rial may pull up and form blisters, and be enthe possible forms the final product takes, I have tirely unsuitable for use. Although variations 85 found that it 11 the desir le properties of good of the carbon content within the limits aforebonding, great strength, and great hardness. said produce material suitable for certain pur The preferred process of producing the mateposes, the most satisfactory tool and die material of the present invention comprises intimately rial is obtained when the carbon content is not 40 mixing together very finely powdered tungsten, varied widely from the preferred content of 5.5%. o and very finely powdered carbon, usually as To the best of knowledge this-cementing lamp-black, in such proportion that the carbon action of W1C or pure W (as the case may be), forms approximately 5.5% of the total by weight. has never before been observed or reported, nor To insure thorough blending, this mixture may the critical relation of. the strength and hardi 4 be ball milled forabout forty-eight hours. The ness of the self-bonded product with its exact 4 resulting powder is then heated in a. hydrogen carbon content. atmosphere furnace for. thirty to forty-five .min- Having thus described my invention, I claim: utes at about 1200 C. to 1800 0., preferably 1. The processoi'making'ahard sintered tungv 1400? C. For this purpose it is preferably packed sten carbide material, which comprises pressing in a graphite cylinder which is perforated or a powdered substance containing from 5.35% to loosely stoppered to permit the ready difiusion 5.65% carbon and the balance substantially tungf of gas. When a graphitecylinder is used, as sten into a desired shape, and subsequently sinsuggested, the powder picks up some carbon from tering the same at approximately 2800' C. the graphite during the'heating, and to com- 2. The process ofmaking ahardsintered tungpensate for this, the amount of carbon actually sten carbide. material which consists in heating a powdered substance containing approximately 5.5% carbon and approximately 94.5% tungsten in a hydrogen atmosphere at approximately 1400 C., pressing the resulting material into a desired shape, and subsequently'sintering the pressed material at approximately 2300 C.

The process of making a hard sintered tungsten carbide material which comprises forming a tungsten carbide material containing from. 5.25% to 5.75% carbon and the remainder substantially tungsten, pressing the same to a desired shape, and subsequently sintering the pressed material at approximately 2200 C. to 2400 C.

4. The process of making a hard sintered tungsten carbide material which comprises forming a tungsten carbide material containing from 5.25

to 5.75% carbon and the remainder substantially tungsten, pressing the same to a desired shape, and subsequently sintering the pressed material out of contact with tree carbon at a temperature of from 2200 C. to 2400 C.

5. The process of makings hard sintered tungsten carbide material which comprises forming a tungsten carbide material containing approximately 5.5% carbon and approximately 94.5% tungsten. pressing the same to a desired shape, and subsequently sintering the pressed material at approximately 2300 C.

6. The process of making a hard sintered tun sten carbide material which comprises forming a tungsten carbide material containing approxi-.

mately 5.5% carbon and approximately 94.6% tungsten, pressing the same to a desired shape and subsequently sintering the pressed material out of contact with free carbon at approximately 230,0 C.

7. The process of making a hard sintered tungsten carbide material which comprises forming a tungsten carbide material containing approximately 5.5% carbon and approximately 94.5%

tungsten, pressing the same to a desired shape, and subsequently sintering the pressed material on a tungsten carbide slab at approximately 8. A self-bonded hard sintered tungsten carbide material containing from 5.35% to 5.65% carbon and the remainder substantially tung-' sten produced by pressing a simple tungsten-carbide material comprising from 5.35% to 5.65% carbon and the remainder substantially tungsten into a desired shape, and subsequently sintering the same out of contact with free carbon at approximately 2200" C. to 2400 C.

9. A self-bonded hard sintered tungsten carbide material containing approximately 5.5% carbon and the remainder substantially tungsten produced by pressing a simple tungsten carbide material comprising 5.5% carbon into a desired shape, and subsequently sintering the same out of contact with free carbon at approximately 2300 C.

HUGH S. COOPER.