US1826455A - Composition of matter - Google Patents

Description

Y od hereinafter described.

Patented Oct. 6 EON entree stares rear it GREGORY J. COMSTOCK, OF PITTSBURGH, AND ELMER B. WELCH, OF MCKEESPORT, PENN- SYLVANLA, ASSIGNORS TO FIRTH-STERLING STEEL COMPANY,

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PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA COMPOSITION OF MATTER No Drawing. Application filed April 9,

The present invention relates broadly to an improved composition of matter, and more particularly to a composition comprising the combination of a cutting agent or cutting agents of abrasive characteristics with a binding agent.

We have found that certain materials, which are hereinafter referred to as cutting agents, when held together by definite percentages of a suitable binder, provide a com position of matter having such characteristics as to render them suitable for a wide variety of purposes. Within the class of cutting agents are included such materials as silicon carbide, tungsten barbide, and vitrified zirconium oxide, these materials being considered as cutting or abrasive agents due to their extreme hardness. The utility of the invention, however, is not limited necessarily with respect to the] particular cutting agent employed, although those referred to give desirable results in accordance with the meth- While the present invention adapts itself to the use of a wide variety of binders, we preferably utilize a metallic binder comprising a high speed'steel. Within this classification we include any of the well known types of high speed steels, such, for example, as those having 14% tungsten, those having 18% tungsten, or those having from 14% to 18% tungsten with from 3% to 8% of cobalt.

It is understood that chromium and vanadium should be present in-the proportions usually adopted forthese alloys, and that carbon is also present in these high speed steels according to the usual limits of composition.

Although in high speed steels chromium and vanadium are usually present, we include in the definition of high speed steels, steels which do not include these'elements.

Where chromium is present it is usuall present in amounts varying from 3% to 6 0,

vanadium from 4 to 2 7,}, and carbon from .3% to 1%. In high speed steels in which cobalt is present, molybdenun is also preferably utilized in amounts varying from /i.% to /270- r In carrying out the present invention we 1928. Serial No. 268,391.

preferably take the desired cutting agent or mixture of cutting agents and pulverize the limiting factor, smaller percentages of binder may be used, but where strength and resistance to shock are required, larger percentages of binder must be present. It is notable that where the binder is increased, the cutting or abrading value of the abrasive, and likewise the cutting or abrading value of the product,

is necessarily decreased due to the relatively greater dispersion of the cutting particles.

For example, in cases of the character first referred to, we may utilize as high as 95%.

of the cutting agent or cut-ting agents with desirable results while in the latter case the binding agent may be increased up to 95% or even higher. In some cases we have found that beneficial results are obtained by the mere addition of a trace of the cutting agent to a standard high speed steel.

In some cases it is desired to provide a composition of matter of such nature that it lends itself to shaping and deforming by hot working. In such cases we utilize not less than 30%, and preferably not less than 50% of the binding ,agent, although variations inthis amountmay be made one way or theother While retaining some degree of workability.

Example I A specific example of a composition suitable for use in the production of tools such as drawing dies, extrusion dies; high speed cutting tools such as bits, shapers, drills, cutters, saws and the like, is as follows:

Tungsten carbide, 87%; 13% of a high speed steel consisting of the following: 0., .70; Si, .25; Mn, .25; S., .025; R, .035; W., 18.00; Cr., 4.50; Va, 1.25; balance iron.

' application,

Example [I As a specific example of a composition of brittle characteristics, adapting the composition to use for the production of dressing tools, metal grinding stones, knife sharpenei's and the like, we refer to the following:

Tungsten carbide 95%; 5% of a typical high speed steel of the following composition: 0., .75; SL, .25; Mn., .40; S., .025; P, .040;W., 18.50; Cr, 5.00; Va, 1.75; Mo, .75; 60., 8.50; balance iron.

Emample I 11 with any of four different methods. The

first of these involves the pressing to shape followed by fusing without any subsequent pressure; the second involves the pressing to shape followed either in sequence or simultaneously by heat and pressure; the third involves the aplication of heat and pressure simultaneously without any preliminary pressing; while the fourth involves the application of heat followed by the application of pressure, without any preliminary pressing.

Tn acco dance with the first method, which will hereinafter'be referred to as the cold compacting method, we preferably form a paste by using a resin, such as gum tragacanth in the amount of one ounce of the gum tragacanth to a pint of liquid, such as water, and add this paste to the mixture of cutting agent or cutting agents and binding agent, in the ratio of about of 1% by weight.

This mixture is then subjected to pressure while cold, the pressure preferably being of the order of 150 tons to the square inch. This produces a clomly compacted mixture which is then subjected to a temperature sufficiently high to melt the binding agent and cause it to actually flow around the cutting agent or cutting agents, so that upon cooling, such agent or agents will be substantially uniformly dispersed or distributed throughout the product with each particle firmly bonded in the binding material, which in this case forms a metal matrix.

In the second method, the preliminary steps of forming a paste-like mixture, and

pressing the same, are followed. Thereafter this mixture is subjected to heat to fuse the bindin g agent, and either simultaneously with the application of the heat, or subsequently thereto while the mixture is still hot, is subjected to pressure.

In the third method, the preliminary cold compacting is dispensed with, the mixture being subjected in a suitable mold to heat and pressure simultaneously.

In accordance with the forth method, which per square inch producing satisfactory results with some mixtures.

Tn heating, in each of the methods above referred to we prefer to employ temperatures in the neighborhood of 2800 F., although it will be obvious that this temperature depends on the particular metallic binder employed, and may vary within fa-irlywide limits. During the heating, suitable precautions must be taken to prevent oxidation of the product. 5 This may be accomplished, for example, by heating in a reducing atmosphere of hydroen. g In all cases where a paste has been formed by the use of gum tragacanth the application of heat volatilizes the same from the mixture.

The hardness of the composition in accordancewith our invention is such that once it. has been produced it does not lend itself to grinding or cutting by known methods. It is therefore desirable, in case the proportions are not such as to produce a workable product, i. e., a product lending itself to shaping or deformation when heated to a suitable temperature, to subject the mixture to pres- 11 sure in a mold having the configuration of the finished article. lln this manner, a completed article, such as a tool, can be formed directly from the mixture.

Throughout the foregoing description H where we have referred to tungsten carbide, we preferably utilize a carbide having approximately 6% of carbon combined with the tungsten. We have found that the other carbides of tungsten produce compositions of materially different characteristics.

While in the specific examples herein given we have referred to the use of tungsten carbide, this being the present preferable cutting agent, either alone or in conjunction 1: with other cutting agents of the character herein referred to, it will be understood that the other cutting agents may be utilized to replace or partly replace the tungsten carbide, the results obtained varying with the char- 11 acteristics of the particular cutting agent utilized.

It will be understood by those skilled in the art that the present invention, according to the best of our present knowledge, results purely in a mechanical mixture or aggre ate, the different materials utilized not com ining chemically to any material degree under thetemperature and pressure conditions to which they are subjected.

It is to be understood that we have described the present preferred embodiment of our invention, but that it is not limited except as required by the appended claims.

We claim:

1. A sintered aggregate comprising finely divided tungsten carbide particles embedded in a matrix of high speed steel, the tungsten carbide constituting about 87% and the high speed steel about 13% by weight of the tool.

2. A sintered aggregate comprising finely divided tungsten carbide particles embedded in a matrix of high speed steel, the tungsten carbide constituting about 87% and the high speed steel about 13% by weight of the tool, the high speed steel matrix containing from about 14 to 18% of tungsten.

3. A sintered aggregate comprising finely divided tungsten carbide particles embedded in a matrix of high speed steel, the tungsten carbide constituting the major portion of the aggregate. i

In testimony whereof we have hereunto set our hands.

GREGORY J. COMSTOCK. ELMER B. WELCH.