US2151874A - Method of making wire drawing dies and other articles - Google Patents

Description

March 28, 193%. L. SIMONS zvlslvgiy METHOD OF MAKING WIRE DRAWING DIES AND OTHER ARTICLES OriginaLFiled-Aug. 7, 1955 2 Sheets-Sheet l INVENT OR.

BY k M ATTORNEYS Ma h 28, 1939. L, MQNS' 2,151,874

METHOD OF MAKING WIRE DRAWING DIES AND OTHER ARTICLES Original Filed Aug. 7, 1935 2 Sheets-Sheet. 2

Fig.1

ATTORNEY! Fatented Mar. 2%, 193% entree stares METHOD Parent OF MAKING WIRE DRAWING DIES AND OTHER ARTICLES Lu u Leon Simons, Bronx, N. m assignor to Master Wire Die Corp, New York, N. 8., a corporation of New York Application August 'z. 1935, Serial No. 35,039

Renewed August 22,1938

Claims.

dies, or dies or articles used for other purposes,-

from finely divided particles of hard and refractory material, without using any binder, although I do not wish to eliminate the use of a binder or binding materials from the scope of the invention.

Another object of my invention is to provide a method and mechanism which can be used for making wire-drawing dies and other articles from finely divided tungsten carbide, boron carbide, and other compounds or substances which have high melting points.

Another object of my invention is to provide a special method for utilizing heat and pressure in order to make dense and hard bodies from said materials, either in powdered form or in lump form.

Another object of my invention is to provide a method whereby the films of air which surround said lumps or particles or which are occluded by said lumps or particles, are removed by means of a high frequency current, together with the simultaneous use of suitable heat and pressure, so as to weld said particles or lumps to each other, preferably without the use of a binder, although I do not exclude the use of one or more binding materials.

Other objects of my invention will be set forth in the following description and drawings which illustrate a preferred embodiment thereof, it being understood that the above statement of the objects of my invention is intended to generally explain the same without limiting it in any manner. l

Fig. l is a side elevation, partially in section, illustrating the mechanism or device which is used for practicing the improved method.

Fig. 2 is a sectional view on the line 22 of Fig. l. r

Fig. 3 is a detail view showing the completion of the process.

Fig. 4 represents a micro-photograph of the completed material, magnified 1500 times. In this case, the article was made from broken-down tungsten carbide material, having a cobalt binder.

Referring to Fig. 1, this shows a base I made out of steel or other metal. m The upper surface of the base i is provided with a covering A, which is made of asbestos or of other heat insulating and refractory material. The member A is preferably rigid and it is made of what is termed in the trade as frock asbestos and it contains vari-. ous ingredients in addition to the asbestos itself. The upper surface of the refractory block A is provided with a recess, in which there is located a filling of a suitable refractory material. Said filling 3 may consists of a mixture of lamp black and of silica.

This material is a commercial product which can be brought in powdered form, and it can be formed into a coherent block, under suitable pressure. Under suitable pressure, the filling 3 can be formed into a dense and coherent block which will withstand a pressure which is as high as one thousand pounds per square inch, or higher.

The filling 3 is utilized because it is a better.

heat insulator than the asbestos block A and it is desirable that this filling 3 should possess maximum heat insulating properties. 7

At the temperature utilized, even rock asbestos will melt and fiow, without the use of a special and superior heat insulation.

The asbestos block A closes the lower end of a casing 2. The casing 2 is held in position by means of any suitable holding device, which is not shown. rhe casing 2 is made of a suitable refractory material such as alundum, this being a trade name for fused-alumina refractory products. The casing 2 can be madeof quartz or any other refractory material.

Above the block A, the casing 2 can be filled with material 9, which is preferably in finely divided and powdered form. The powdered material s can be similar in composition to the material 3, so that the material 9 has maximum heat-insulation properties. I

While the material d is subjected to some pressure during the operation of the device, it remains substantially in loose powdered form, whereas the filling 3 is a very dense block of material.

A block A, which is identical with the block A, has its lower surface recessed and provided with a filling 3, which is identical with the dense coherent filling Prior to utilizing the members A and A in the apparatus, together with their associated fillings 3 and 3., the recesses of said members .A and A can be filled with said fillings in powdered,

form, and said powder can then be subjected to suitable pressure, as high as one thousand pounds per square inch, in order to form dense and coherent blocks of filling material.

A graphite mould d is provided with a bottom planar surface, which rests upon the top of the block 3. The diameter of the base of the mould d is less than the diameter of the block 3. The distance between the edge of the bottom of the mould 4i, and the edge of the top of the block 3, should be sufiicient so as to provide for emcient heat insulation. This distance may be about one-eighth of an inch or more if desired, depending upon conditions.

The bottom of the mould it may be provided jection and recess prevent any lateral shifting of the mould 4 relative to the block 3. Said center projection and recess are not shown in the,

drawings as this expedient is well known per se.

The interior of the graphite mould 4 is filled with the material 1 whichis to be used for making the blank for the die. or other article.

As previously stated, said material 1 may consist of tungsten carbide, boron carbide, or other hard and refractory material, either in finely divided powdered form, or in lump form, or any gradation of these forms.

It is not necessary that the material 1 should be in pieces of uniform size,

The plunger 8 has a cylindrical bottom portion which fits slidably and closely in the cylindrical bore of the recessed upper portion 6 of the mould 4. The plunger 8 is also made of graphite and its top surface may be prevented from shifting laterally, relative to the block 3, by-means of a centering projection and recess, as previously specified.

The upper block A is subjected to pressure by means of removable weights III. In compressmg the material 1, I can use pressures as high as four thousand pounds per square inch. The amount of pressure to which the plunger block A is subjected, depends upon the cross sectional area of the object which is to be formed from the material 7,

The cavity in the mould is surrounded byand it is located in the field of a hollow coil G which is supplied with a suitable high frequency current. Thishigh frequency current may have a frequency as high as seventy thousand (70,000)

cycles per second, and the voltage which is induced or produced at the ends of the coil G, may be as high as 1000 volts.

The coil G is cooled by forcing water or other cooling liquid or vapor or gas through the same. The cooling medium can be forced in through the inlet H, and it emerges from the outlet l2. .The ends of the coil can be provided with electrical couplings l4 and I5 to which the electrical leads l4 and I5 are connected. Said leads I and I5 are connected to a suitable source of high frequency current. This source may be a high frequency converter of any conventional type.

The apparatus is utilized as follows:

I A suitable charge of material 1 is placed within the recess of the graphite mould. The plunger 8 is then located in position, and the interior of the casing 2 is tlgen filled with the loose powdered material 9. The plunger block A is then inserted into the top of the casing 2. Said member A fits closely and slidably in casing 2. 4

One or more of the weights III are preferably placed upon the plunger A, so as to produce some pressure, but not the maximum pressure. Current is then supplied to the coil G. For example, while I do not wish to limit myself to the preferred method illustrated herein, if the maximum pressure which is to be exerted upon the powdered material 1 is 4000 pounds per square inch, the powdered material I can be subjected to a pressure of about one-half this maximum, before the current is supplied to coil G. The current is supplied as soon as the initial pressure has been applied.

The effect of the high frequency current is to remove a part of the films of air or other gas or gases which have been occluded on or adsorbed by the particles or lumps of the material 1.

Graphite has a certain porosity so that the air or other gases can either escape through' the wall of the graphite mould, or else, which is more likely, the graphiteadsorbs the air orother gases.

The wall of the graphite mould, around the recess therein, may have a thickness of from onequarter of an'inch to'three-quarters of an inch depending upon the thickness or diameter of the object which is being made.

In making small sizes of dies, the diameter of the recess of the mould may be equal to one-half of the thickness of the wall of the mould around the recess. This proportion can be followed if the diameter of the recess of the mould is onehalf of an inch.

In making larger sizes of articles, there may be a closer approximation between the diameter of the recess and the thickness of the wall of the mould.

While the drawings are diagrammatic, they are nevertheless substantially to scale.

In addition to removing occluded or adsorbed air, the high frequency current also heats the material 1 by means of induction.

' The powdered material 1 may contain and it preferably does contain a small percentage of iron, which may be as high as 2%. This iron or other paramagnetic material may be a constituent part of the particles of the material 7, and

this is preferred. Other paramagnetic material or materials may be present in suitable proportion in the material I. Likewise while I prefer not to use any binder such as cobalt or nickel or I the like, I do not wish to exclude the use of such binder, which may be paramagnetic.

Hence, the material is heated by means of the alternating polarity which is created by the electromagnetic induction of the field 1. However, I do not wish to be limited to any definite theory of operation because it is sufficient if the particles of the material I have sufficient conductivity so as to permit a current to be induced in the body of material 1. by the alternating electrostatic induction. That is, the particles of the material 1, may be considered as forming a series of conductors of electricity which abut each other more or less loosely and which are frequently separated by very thin films of air. When 2. current is induced in said body of material, said current produces heat at the adjacent points of said particles and this heat is sufficient to remove intermediate air and to cause the fusing of the particles or lumps of material 7. Said particles or lumps of material may be wholly fused and welded to each other or they maybe fused and welded to each other partially, depending upon the size of the particles, the temperature, the pressure, and the composition of material 7. This fusing can be accomplished either substantially by electro-magnetic induction, or by electrostatic induction (if the material has little or no paramagnetic properties), or by a. combination of said two effects. It requires a temperature of at least substantially 2500 C., in order to fuse the broken down or salvaged tungsten carbide material which was made with the use of a nickel binder or cobalt binder.

Likewise, the heating effect is produced at least in part by eddy currents, and also by hysteresis if the material has paramagnetic properties.

Since the wall of the graphite mould around the recess therein, has a substantial thickness, as

previously stated, an alternating current is in mould 5. Likewise the plunger 8 fits closely in the bore of the recessed portion of the mould,

and the varying electro-magnetic flux passes through said plunger 8, so that said plunger is also heated by the varying electro-magnetic flux.

Since the plunger 8 and the mould 4 are surrounded by material which has high heat-insulation properties, the varying electromagnetic flux heats the mould d and the plunger 8, to the desired high temperature.

In the specific example shown in Fig l, to which I do not wish'to be limited, the heating current in the mould and plunger, flows in a horizontal plane.

If the material 1 is conductive, the secondary voltage also has a closed circuit through the material l.

As the contacting parts of the pieces of material l fuse, more weights are added to the top of the plunger A.

The final stage of the operation is illustrated in Fig. 3, which shows how the material I has The initial application of the weights produces sumcient pressure so as to produce contact between particles of the material I, but this contact is only along small points or areas.

As the material softens, the area of contact between the particles or lumps of the material is increased, more current passes through the material 7, and the heating effect is increased.

Ordinarily, in forming a block of material whose diameter is one-half of an inch and whose height is about three-eighths of an inch, the process takes from five to eight minutes. After the plunger A has descended to its lowest position, after the maximum pressure has been applied, the current supplied to the coil G isdiscontinued. The material i is then maintained under the maximum pressure, while the supply of current is discontinued, for a suitable period of time, such as about fifteen minutes, until the material 11 has solidified. Since the carbide is subjected to simultaneous heat and pressure, the period during which the material is heated is relatively short so that the tungsten carbide is not oxidized to any substantial extent, thus making it unnecessary to use a reducing atmosphere.

By maintaining the material 7 in a. space which is sufilciently air-tight, and under suitable pressure, the material is prevented from taking up any air or other gases while it solidifies at its points of fusion, and the material is also prevented from. expanding while it solidifies at its points of fusion.

While the material is being heated, the coil G is continuously cooled to about 50 F. After the supply of current has been discontinued, the flow of water through the coil G is continued so as to maintain the cooling efiect thereof,-even though the coil G does not actually contact with the tube 2, which is a good insulator of both heat and electricity.

The completed die or other article can be removed by breaking or cutting the graphite mould.

I prefer to use a mould made of graphite because it has a very high melting point and because it has also great strength and it can adsorb air or other gases.

Likewise the process is valuable for utilizing the material of worn out and broken tungsten carbide dies, of the type in which cobalt or, nickel or other relatively low melting metal has been used as a binder. For this'purpose said dies can be broken into lumps or crushed into powder.

The graphite mould permits the cobalt or other low melting metal to pass wholly or partially into or through the wall thereof, while retaining the tungsten carbide or boron carbide or the like.

The temperature to which the material I is raised, is above the melting point of the cobalt or nickel or the like. When the process is utilized for treating material of, the tme previously mentioned, in which a metal having a relatively low meltingpoint has been used as a binder, the operatlng temperature is below the melting point of pure tungsten carbide, because the initial sintered material has a lower melting point than pure.

Upon examining the completed material through a high-power microscope, after it has been removed from the graphite mould, it can be seen that the completed material-consists of particles which contact along substantial areas, but

all or nearly all of said particles may have small intervening spaces between them.

The block A is made removable from the casing 2 so as to facilitate the removal of the mould, after the operation has been completed.

The casing 2, and the members A, 3, A" and 3, and the filling 9, are very good electrical insulators. The mould l and the plunger 8, which are made of graphite, are good conductors oi electricity. The plunger 8 fits closely in the recess of the mould, so that the inner end of said plunger is in conducting contact with the mould. Hence a high frequency current is induced in, and confined to, the mould and the plunger, and through the material I. By using a current of sufliciently high frequency, it is possible to heat the material I to the desired high temperature, even though the ends of the mass of material 1 are not electrically connected. I prefer not to complete the electricclrcuit between the ends of the mass of material I, because there would be a considerable waste of electricity and heat if 'the mass of material 1 formed part of a continuous electric circuit.

When I refer to inducing a current in the material l, in some of the claims, I refer to a system in which the mass of material 1 acts as the core or secondary member, of a primary coil.

The mould and. plunger 8 are made of very refractory material, which can withstand the high temperature and pressure. The powdered filling 9 can be compressed suiliciently, without becoming too coherent, and witho t losing its insulating properties,.so as to pern the compression of material '5. The inner end'of plunger 8 is provided with a point or projection, as shown in Fig. 3, so as to provide a recess in the blank, which is completed in the usual way, in order to make a wire-drawing die. I The projection may have a circular cross-section or a cross-section of any shape, such as hexagonal.

Since the heat is generated internally in the material I, it can be brought to the desired temperature without the use of a furnace.

The entire apparatus, including base i, may be mounted on an insulated support, so as to pre-- vent sparking due to electrostatic induction When tungsten carbide material is used, which includes-a. metal binder, such as cobalt, the final piece of material consists predominantly of tungsten carbide crystals (containingiron or the like) and these crystals are regular in shape, in-

dicating recrystallization from solid solution.

1 The matrix or cementing material between crystals is a solid solution of cobalt and tungsten carbide. The material is in effect, a hot pressed alloy. This is shown in Fig. 4,-which represents the manufacture of a new die from broken-down dies made of tungsten carbide material having a cobalt or nickel binder of the well-known type known as Carboloy etc. scribed in Reissue Patent No. 17,624.

It will be noted that the current is induced in the particles and also in the mold and plunger (if they are made of conducting material) by causing said particles to act as the secondary circuit of the alternating electro-magnetic flux. When I refer to inducing a current in the particles, in some of the claims, I refer to the system shown in Fig. 1, in which the particles act as the secondary to the primary coil G.

I have shown a preferred embodiment of my invention but is is clear that numerous changes and omissions can be made without departing from its spirit.

I claim:

1. A method of connecting a mass of oxidizable refractory particles to each other so as to form a coherent mass, said particles containing a major proportion of carbide material and having a minor proportion of a metallic binder which has a lower melting point than said carbide material, which consists-in subjecting said particles while they are enclosed in a container made of conducting material, to the heating effect of a varying electro-magnetic flux which is caused to induce a secondary voltage having a closed circult within said conducting material and said particles, said mass being heated to a temperature which is at least substantially equal to the fusion temperature of said refractory particles so that the heated particles can be shaped under pressure and the volume of said mass can be diminished under pressure, and while subjecting said heated particles to pressure while they are enclosed in said container during a sufficient part of said period of heating so as to form a coherent mass of smaller volume than the original mass of said particles, and while preventing any substantial oxidation of said particles during the formation of said coherent mass.

2. A method of connecting a mass of oxidizable refractory particles to each other so as to form a coherent mass, said particles comprising a major proportion of oxidizable refractory carbide material and a minor proportion of a cementing metal which has a melting point lower than said carbide material, which consists in subjecting said particles while they are enclosed in a container having a graphite wall, to the heating effect of a varying electro-magnetic flux which is caused to induce a secondary voltage having a; closed circuit within the wall of said graphite container, the heating temperature being above the melting point of said cementing metal, said heated particles being subjected, while they are enclosed in said container, to pressure while they are enclosed in said container, so as to diminish the volume of said mass and to cause said particles to coalesce under pressure, the heat being sufficient to eliminate only some of said metal from said mass through the inner surface of said graphite wall, said particles being connected without any substantial oxidation thereof.

3. A method of connecting a mass ofoxidizable refractory particles to each other so as to :form a coherent mass, said particles containing a This material is demajor proportion of oxidizable carbide material and having a minor proportion of a metallic binder which has a lower melting point than said carbide material, which consists in subjecting said particles in an enclosed space to the heating effect of a varying electro-magnetic flux which is caused to induce a secondary voltage having a closed circuit within said particles, said heating effect being suflicient to raise said particles at least substantially to the fusion temperature of said particles so that said particles can be shaped under pressure, said mass being thus heated to a temperature which is above the melting point of said metallic binder, subjecting the heated particles to pressure in said enclosed space in order to connect said particles and to reduce the volume of said original mass, and eliminating only a portion of said metallic binder from said particles during the action of said heat and pressure, said operations being performed wholly in said enclosed space and without any substantial oxidation of said carbide material.

4. A method of salvaging tungsten carbide material which includes a metal having a lower melting point than said tungsten carbide material, which consists in heating particles of said material in an enclosed space, by means of a varying electro-magnetic flux which is caused to induce a secondary voltage having a closed circuit within said particles of material, whilesubjecting said heated particles to pressure in said enclosed space to connect said particles, said heating temperature being at least substantially equal to the fusion temperature of said tungsten carbide material so that said particles can be shaped 'under said pressure and the volume of said material is diminished under said pressure, the temperature of said heating being above the melting point of said metal, and then allowing the heated and pressed material to cool, said heating temperature being sufliciently high to produce regular crystals of tungsten carbide substantially throughout the final material and to produce a cementing material between said crystals which consists of a solid solution of said metal and tungsten carbide.

5. A method of salvaging tungsten carbide material which includes a metal having a lower melting point than said tungsten carbide material, which consists in heating particles of said material in an enclosed space by means of a varying electro-magnetic flux which is caused to induce a secondary voltage having a closed circuit within said particles of material, while subjecting said particles to pressure, the temperature of said heating being at least substantially equal to the fusion temperature of said tungsten carbide material so that said tungsten carbide material can be shaped under said pressure and the volume of said material is diminished under said pressure, the temperature of heating being above the melting point of said metal, and then allowing the heated and pressed material to cool, the heating temperature being suflicient to produce regular crystals of tungsten carbide substantially throughout the final material, and to produce a cementing material between said crystals which consists of a solid solution of said metal and tungsten carbide, only some of said metal having said lower melting point being driven out of said salvaged material and out of said enclosed space during the heating of said particles, said final material being produced without any substantial oxidation of said tungsten carbide material.

LEON SIMONS.

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