US1922178A - Metal-working implement - Google Patents

Description

g- 1933- w. J. SCHULTZ 1,922,178

METAL WORKING IMPLEMENT Filed Jan. 27, 1932 2 Sheets-Sheet; 1

INVENTOR Aug. 15, "1933.

W. J. SCHULTZ METAL "'JOEIKING IMPLEMENT Filed Jan. 27 19:52

2 Sheets-Sheetv 2 Patented Aug. 15, 1933 n'rAL-wonmn'o. IMPLEMENT .William J. Schultz, Glassport la assignorto Firth-Sterling Steel Companm a Corporation of Pennsylvania hpplicationjanuary z'l,1932. steal No. 589.1 91

= 4 Claims. (areas-26y The invention relates to metal-working implements of composite structure, two'representative types of which are wire-drawing dies and tools for cutting metal. A die for the drawing of wire, s for example, usually comprises an orificed block of some extremely hard substance, such as the diamond (which, in the strict ,senseof the word,

is itself the die) and a metallic carrieror casing, in which the block is veryfirmly secured or,

10 embedded. It is usually essential that the setting of the block in its carrier shall be of the greatest attainable rigidity, for the block when in serviceis often subjected to strainsand shocks so very great that an irregularity or looseness of mounting so slight in magnitude as to be termed microscopic may cause the block of diamond or other valuable substance to crack and thus ruin thedie. I 1

I In the accompanying drawings Figure l is a view in sectional elevation of, a suitable mold for the formation of a composite die structure ,em-

bodying the invention. Figure 2 is a like ,view of the finished composite die. Figure 3 is a central cross-sectional view of the ,orificedblock of the die. I Figure 4 is a view imperspective of a lathe tool embodying the invention. Figure 5 shows in central vertical section a mold of modifled structure for the forming of the composite die- Figure 6 is a likeview, showing in outline the casting made in the mold of Figure 5, and

, illustrating the finished die structure;

In recent years it has been found that for wire I drawing purposes what; are knownas cemented carbides ofv some of the more refractory metals,.

such as tungsten or tantalum, may be, used as die substances, as substitutes for the diamond, The hardness and the ruby or the sapphire. durability of these cementet' :arbides approxie mate the hardness and durability of the precious 0 stones referred to, and their cost is less; but they are nevertheless subject to failure under heavy stresses, and their cost of manufacture is relatively high. They therefore can be used economically in dies or other metaleworking implements only as the precious stonesare used, that is, as

smaller bodies set into or supported by larger bodies of cheaper metal. i I Heretofore it has; been the general practice in the manufacturing of composite dies for drawing wire provided with working. blocks of cemented,

tungsten or tantalum carbide, to form the block and grind its exterior surface to a slight taper, and then to fit this tapered block intopa corresponding cavity in a cup or matrix of toolsteel or 1 other suitable substance, ordinarily metal. The

block-may or may not be brazed into its carrier;

in; some cases it has been secured in place mechanically, as by wedging; in other cases the tungsten carbide block has been molded into the matrix or eupof steel, under heatand pressure, as shown and described, for example, in United States Letters Patent No. 1,637,109. But in whatever manner the blockhas been secured, it has heretofore been true that theheavy strains or shocks which are incident to the drawing ofwire have often caused premature cracking or breaking of the block. q

, It is theobject of the present invention to produce such a composite die or other metal-working (implement, by casting a carrier body upon (and in the case of a die, entirely around) the surface of the work-engaging body (or core) of cemented carbide, the carrier body being, of such material hereinafter specified, as to form with the substance of the block, or other work-engaging body, 76

a union secure against failure under, the strains of service. Continuing, for present purposes, specific reference to the manufacture of dies for the drawing of wire, and choosing by way of example cemented tungsten carbide as the material for the 0 block, that substance has the property of conducting heat muchmore rapidly than steel, and itscoeflicient of thermal expansion is much lower than are those of steel and of numerous ferrous alloys which might conceivablybe used as materialfor the carrier for the tungsten carbide block.

Most metals which I have tried are not suitable for use as material for the carrier for thecemented carbide. block, for the reason that theunion between the block and the carrier is insecure in spots, or not sufficiently rigid. I believe that this is due to the differences in coeflicients of expansion between the block on the one hand and the carrier on the other; buthowever that maybe, the results with cast steel and various steel alloys have been unsatisfactory.

I have, found, however, that when an iron of the type to be presently described is cast in a suitable mold upon and around the surface of the cemented tungsten carbide block, a

;very intimate and satisfactory union is obtained,

and that the composite die thus formed is superior inservice to any of which I am aware The metal which I prefer to use for the cast carrier is one which is known commercially as Meehanite, and it is the productof the methods described in United States LettersPatent No. 1,499,068, No. 1,683,086, No. 1,683,087 and No. 1,731,346. I Briefly stated, this product is obtained by the addition to the bettergrades of molten commercial cast iron of a small amount of a siliside of an alkaline earth metal, such as calcium or magnesium, orby the addition of metallic calcium. The product has been called'synthetic processed and graphitized cast iron, and it possesses the physical properties of density, tensile strength, and thermal conductivity in much greater degree than ordinary cast iron. Its content of graphitic carbon isapparently in a nodular form instead of existing as flakes of :graphite, and in structure the metal is close grained and homogeneous. In order to define this metal I have called it in the appended claims modified cast iron. Modified cast iron, then, as used in this specification, will be understood to be the metal last above defined.

During the operation of forming the compositestructure the outer portion of the tungsten carbide block becomes absorbed by or dissolved in the molten metal, decreme'ntally or in gradually decreasing quantities outwardly. Thus the crosssectional areas immediately surrounding the undissolved carbide block will partake to some extent a of the physical properties of the block itself, and

' cracked or broken under the severe conditions to which it is subjected in operation;

Referring first to Figure 1 of the drawings, the

carbide block 1, which in this case is pierced entirely through, is set upon the tapering shoulder 2a of a core portion 2 of the mold The core portion 2 is constructed of a baked sand composition known to foundrymen, and is pasted in position in the bottom of the mold. Foundrymens paste is also used to secure the block 1 upon the core portion 2, and, additio'nally, a core portion 3 is secured in place, as shown, between the top of core portion 2 and the top of the mold. The molten modified cast iron may be supplied to the mold through the gate 4, and the molten metal may be'poured in the usual way.

Heretofore in wire-drawing apparatus the dies v have been'provided with auxiliary water-cooled rings, surrounding the'dies and serving with some degree of success to maintain the dies in a cool condition. However, the'results have not been all that they'were desired to be. I have discovered how a composite die-may be constructed to permit direct cooling within its own body--this resulting in improved temperature conditions during servioe. To provide a water-cooled die, I construct an annular blanked-sand core member 5, having integrally attached thereto the downwardly proj ecting legs 6, to form in the casting inlet and outlet ports for the annular water-chamber formed by the core 5. Advantageously the core 5 and legs 6 are provided with vents for the escape of gases during the "casting operation.

After the solidified casting has been removed 1 from the mold and the substance forming the core members broken up and cleaned out of the casting, the wire-drawing orifice in the inner carbide block may be machined with diamond dust, in the usual manner. The inlet and outlet openings 7 may be threaded, and the-water pipes8 inserted in the openings 7, and the die be thus completed, as shown in Figure 2.

The mold may be constructed of a baked-sand composition, and insuch case will comprise a The two mold members are complementary in shape at 22, so that they nest snugly together in accurate relative positions. As in the case of the structure first described, the mold 20, 21 may be provided with an annular core-member 5a, having two legs 6a to provide outlet and inlet ports for the annular chamber formed in the casting by the core-member 5a. The legs 6a are pasted in secureposition in sockets 6b provided in the stool 20.

The carbide block 111 is supported upon the pointed end of a stem 23; the block may be pierced through, or only partly pierced, but in either case it is positioned upon the point of stem 23. Foundrymens cement or paste is used with good results to secure the block upon the stem.

I have found that an unusually sturdy and precise positioning of the block 1a may be obtained by this structure. The stem 23 may be formed of modified cast iron and be initially molded within a sand core 24, and the core 24 is then baked. The baked-sand core is provided withtapering sides, to fit a tapered seat 25 provided in the mold. stool 20. The core 24 is pasted in seat 25. In the completed structure the block 1a will be found to have maintained its truly-centered position. The stem 23 is readily machined out, and the drawing orifice shaped to proper size and condition for service when the casting C (Figure 6) is being finished into its final form.

While the method of manufacture of the carbide block forms no part of the present invention, it may be said that in some cases it will be advantageous to place the carbide block in the mold in a partially sintered state, since it is possible during the molding operation to sinter the block finally, without the use of hydrogen or other reducing gases and packing materials previously regarded as necessary to the proper sintering of the carbide.

Also, if there should be used a sintered carbide block having its pores filled with cast iron, as described for instance in United States Letters Patent No. 1,512,191, the sintered carbide block may be set in the mold, as shown, and both the saturation of the carbide block and the formation of the composite die be completed in a single operation.

Owing to the fact that the relative sizes of the carbide block and the cast iron carrier, together with the temperature of the molten metal and the time of cooling, will exercise an important influence upon the product, it will be seen that by carefully regulating conditions of size, time and temperature, the amount of carbide which will be absorbed or dissolved in the cast carrier may be regulated with'great accuracy, and a superior product be thereby obtained.

It may be remarked that a carbide block of exceedingly small wall thickness may be employed as a result of my invention. For example, I have constructed a wire-drawing die in which the wall of the carbide block is less than onesixteenth of an inch thick. Manifestly, great savings in the valuable metal may be thus effected, and field for use widened. Indeed, I contemplate its use in wire guides and bearings, and in other machine parts normally subject to great wear.

In view of the foregoing description, the man- I ufacture of the lathe tool shown in Figure 4 of the drawings need notbe described in detail. It

stool 20 and a body 21, as shown in Figure 5. is made up of a working tip 10 formed of the m R 7 1,922,178 carbide, and a shank 11 formed of the modified cast iron hereinbefore specified, the parts being welded together in a molding operation substantially the same as that already described.

It will be understood that by reference to the carbide of which the block is formed I intend to include the hard carbides of tungsten, tantalum, silicon, titanium, zirconium, thorium, beryllium, vanadium, chromium, molybdenum, uranium, and of alloys and mixtures of such elements. Also, the term "cemented carbide as heretofore employed may not in all cases be accurately descriptive of the method of manufacture. For example, in some instances the term sintered carbide" has been employed. Whatever may be the detailed method of manufacture, these hard metallic carbides constitute in themselves a well known class of metallic substances, and by the l use of the term carbide" in the appended production.

I claim as my invention: 1. A metal-working implement comprising a carbide metal block having a supporting body of modified iron cast and autogenously welded upon itssurfacea 2. A wire-drawing die consisting of an oriflced blockof tungsten carbide set in a carrier of modified cast-iron in a union characterized by the autogenous penetration of the block material into the substance of the carrier material incident to the casting of the carrier upon the previously formed block.

3. A metal-working implement comprising a carbide metal block set in a carrier of modified cast-iron in a union characterized by the autogenous penetration of the block material into the substance of a carrier material incident to the casting of the carrier upon the previouslyformed block. 7

' 4;. A metal-working implement comprising a tungsten carbide metal block set in a carrier of modified cast-iron in a union characterized by the autogenous penetration of the block material into the substance of the carrier material incident to the casting of the carrier upon the previously-formed block. I

WILLIAM J. SCHULTZ.

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