US2698232A - Method of making cemented carbide articles and casting compositions therefor - Google Patents

Method of making cemented carbide articles and casting compositions therefor Download PDF

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US2698232A
US2698232A US166180A US16618050A US2698232A US 2698232 A US2698232 A US 2698232A US 166180 A US166180 A US 166180A US 16618050 A US16618050 A US 16618050A US 2698232 A US2698232 A US 2698232A
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carbide
ether acetate
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Edward W Golibersuch
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides

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  • I-Iot pressing comprises compacting hard metal carbide process for forming cemented presintering and mechanically working or grinding wheels to producethe final powdered materials in-a* mold'---with the 2,698,232 Patented Dec. 28, 1954 that such removal is necessary to enable the cast-article to perform its-expected function.
  • Hard metal carbide powdered materials as used herein are intended to include all the refractory hard-metal carbide powders which are used as ingredients in manufacturing commercial carbide products, having added hard metal carbide thereto as a binder an iron group metal, such as, for example, tungsten carbide, tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide and mixtures thereof together with a binder of the iron group, preferably cobalt.
  • an iron group metal such as, for example, tungsten carbide, tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide and mixtures thereof together with a binder of the iron group, preferably cobalt.
  • the purpose of the casting vehicle is to give the dry powdered materials suflicient fluidity to permit the pouring-thereof without heating, and also by polymerization to bond the powdered materials into a hardened body so that the mold may be removed and the cast article handled or even mechanically Worked where this is-desirable.
  • ing vehicle for hard metal results 1 when an unsaturated mixed with a vinyl derivative such as styrene-is diluted
  • the unsaturatedpolyesters of the maleic type for example, reaction products of a polyhydric alcohol and maleic acid or anhydride mixed with a vinyl derivative such as styrene form an excellent material for cold cast plastics, but when they are used alone they are not satisfactory as casting vehicles for my process as they-cannot be conveniently' removed from the cast cementedcarbide -articie.
  • cemented carbide articles by my process contemplates the steps ofmixin'g hard metal carbide powdered materials .with an'organic casting vehicle,
  • liquid ethers or esters of ethylene glycol or diethylene glycol such as diethylene glycol monoethyl ether "acetate, ethylene glycol monoethyl ether acetate, glycol diacetate, ethylene glycol monomethyl ether acetate, mixtures "of diethylene glycol with one of the abovenamed I Theconvemenhremoval of the polymerizedcastmg.
  • the initially miscible, nonpolymerizable organic liquid should amount to about 65% to about 83% of the volume of the casting vehicle. If the vehicle contains less than about 65 of organic liquid the drying time is increased and it becomes very difficult to expel the vehicle without cracking the cast article. On the other hand, if the organic liquid is present in amounts greater than about 83%, the polymerizable ingredients will not impart sufficient green strength to the cast article to allow mechanical working or handling.
  • compositions are particularly suitable as a casting vehicle for my process in that they form a thixotropic gel when mixed with the powdered hard metal carbide or carbides.
  • vehiclecarbide mixture is capable of undergoing isothermal, reversible sol-gel transformations, a fluid sol existing as long as the mixture is agitated, the sol reverting into a gel within a short time after agitation has ceased.
  • This property is important because it permits the use of a mixture which is fluid enough to pour while agitated, stirred or vibrated, but which prevents appreciable settlingofhe on heating the thixotropic mixture after casting, the ve- -hicle polymerizes into an infusible product which is no longer capable of reversion into the fluid sol state.
  • the prevention of settling greatly reduces the unequal d1str1- bution of the carbide powders in the casting and thereby keeps distortion on sintering to a minimum.
  • compositions have the following properties: during agitation they are fluid enough to be cast at room temperature without the use of pressure; they are sufficiently thixotropic to prevent excess settling of the heavy constituents of the carbide powdered materials before permanent setting or solidification by polymerization occurs; they will cold set at room temperature or 4 harden with the application of heat; they impart sufficient green strength to the casting to allow handling and even mechanical working; they are conveniently removable bv heating without cracking the article or destroying its shape; and they leave no detrimental residue to aifect the physical properties of the finally sintered article.
  • volume percentage in relation to the powdered hard metal carbide or carbides I refer to a calculated volume which is determined by dividing the weight of the powdered carbides by the final sintered density of the carbide material, which density is a well known quantity for any particular carbide composition to those who are skilled in the art.
  • cemented carbides such as tungsten carbidecobalt mixtures in which the cobalt varied from 6 to by weight; to tungsten carbide-tantalum carbide-cobalt mixtures in which the tantalum carbide varied to a maximum of 27% by weight; to tungsten carbide-titanium carbide-tantalum carbide-cobalt mixtures, and. to tungsten carbide-titanium carbide-cobalt mixtures in which the titanium carbide varied to a maxium of 32% by weight.
  • Particle size of the cemented carbide powdered materials has a slight eifeet upon the amount of casting vehicle which is required, with more casting vehicle being needed as the particle size decreases.
  • the above limits relate to carbide powdered materials of normal commercial particle size.
  • a more satisfactory and controllable composition can be made from a mixture of diethylene glycol and ethylene glycol monoethyl ether acetate. The degree of syncresis can then be increased and evaporating time decreased by increasing the proportion of diethylene glycol in the mixture.
  • a formulation which has been found to give good results comprises:
  • 131g. 1 is a perspective view of the mixing apparatus which may be used 1n carrying out my process.
  • F g. 2 1s a sectional view along line 2--2 of Fig. 1.
  • Fig. 3 1s a s1de v1ew section of a typical mold that may be employed in my process.
  • MlXllJg chamber 5 is attached toa'the plate-6::bymeans of screws 7 forming an air tight seal therewith.
  • Son mixing chamber. 5 and rubberseal 2 are closed and hopperland mixingchamber 5.are evacuated through 1ines 9and 10 which are connected to a commercialrvacuum pump. After evacuation, valve 11.0n l1ne.9 and valve 12 in line 10- are closed so that hopper 1 and :mixing chamber 5 remain evacuated.
  • Equal weights of styrene or vinyl acetate and unsaturated maleic polyester are mixed together. to form a standard stock casting vehicle. 'A measured quantity of this mixture is thenadmixed with the desiredamount of the nonpolymerizable.
  • the vacuum is released on mixing chamher 5 and my casting composition is ready for casting into a typical mold such as that shown in Fig. 3. This is accomplished by opening valve 8 and allowing the mixed castlng composition to fill the mold.
  • the mold may be under vacuum if desired, or it mav be open to atmospher1c pressure.
  • casting in an evacuated container is beneficial when the surface configurations are of fine detail involving minute cavities in the mold in order to obviate the tendency to bridge over these cavities, but otherwise casting in air is perfectly satisfactory.
  • tapping on the side of mixing chamber 5 aids the continuous flow of the thixotropic casting composition, and it will be appreciated that this may be accomplished by vibrations supplied from vibration apparatus if desired.
  • Mold materials which I have used successfully include wax, glue, Woods metal, aluminum, steel, etc., but I prefer wax or glue due to their cheapness, availability and ease of manufacture into the shape desired. Specifically, I have successfully used paraffin, casting waxes and micro-crystalline waxes and special glue mold materials which are commercially available.
  • the casting composition After the mold is filled, the casting composition is allowed to stand therein until it hardens; the time required for polymerization or hardening will depend upon the actual casting composition used and the temperature, as well as the size of the article. In general, higher amounts of catalyst and higher temperatures speed up the hardening. Hardening will occur at room temperature but higher temperatures cause hardening in shorter periods of time. I have found that sufiicient hardening occurs at approximately 80 C. in approximately four hours.
  • the next steps in my process comprise removing the sol vent and polymer from the cast article.
  • the first step is accomplished by placing the article in a drying furnace at 45 C. to 150 C. for 2 to 5 days depending upon the size and shape of the article with the larger articles requiring proportionately more time.
  • the second step is to expel the polymer by heating in a hydrogen or other inert atmosphere at 450 C. to 800 C. for approximately one hour.
  • the process for making hard metal carbidearticles of complicated shape which comprises the following steps: (1) preparing a thixotropic casting composition comprising a mixture of finely pulverized refractory hard metal carbides and an iron group metal, a casting vehicle consisting of styrene and the reaction product of a polyhydric alcohol and maleic acid and a nonpolymerizable organic liquid having an appreciable vapor pressure below C.
  • a casting mixture comprising a thixotropic mixture of about 38% to about 41.5% by volume of hard metal carbide powdered materials, a copolymerizable mixture of vinyl acetate and the reaction product of a polyhydric alcohol and maleic acid in amounts of about 10% to about 20% and about 41.5% to about 48% of an organic solvent capable of dissolving the said copolymerizing mixture prior to polymerization selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate, and ethylene glycol monomethyl ether acetate, and a small amount of a polymerization catalyst.
  • a thixotropic casting composition comprising about 39% of tungsten carbide and cobalt by volume, said cobalt falling within a range of 6% to 20% by weight of the tungsten carbide, about 7.8% styrene. about 6.1% of a tetrahydrofurfuryl alcohol modified dipropylene glycol maleate, about 11.5% diethylene glycol, about. 35.9% diethylene glycol monoethyl ether acetate and about .15 benzoyl peroxide.
  • the process for making hard metal carbide articles of complicated shape which comprises the following steps: (1) preparing a thixotropic casting composition comprising a mixture of finely pulverized refractory hard metal carbides and an iron group metal, a casting vehicle consisting of vinyl acetate and the reaction product of a polyhydric alcohol and maleic acid and a non-polymerizable organic liquid having an appreciable vapor pressure below 150 C.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mold Materials And Core Materials (AREA)
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Description

1954 E. w. GOLIBERSUCH 2,698,232
METHOD OF MAKING CEMENTED CARBIDE ARTICLES AND CASTING COMPOSITIONS THEREFOR Filed June 5. 1950 INVENTOR. Edward W. Go/fbersuch United States Patent METHOD OF MAKINGCEMENTED CARBIDE ARTICLES AND CASTING COMPOSITIONS THEREFOR Edward W.- Golibcrsuch, Detroit, Mich.,-assignorto Genera! Electric Company, a-corporation fof New -York Application June 5', 1950;. Serial No. 166,180 '7 Claims. (Cl. 75-403) comprises compacting the hard metal carbide powdered materials under a pressure of approximately 2'to=.30 tons per square inch, with cutting tools desired shape.
I-Iot pressing comprises compacting hard metal carbide process for forming cemented presintering and mechanically working or grinding wheels to producethe final powdered materials in-a* mold'---with the 2,698,232 Patented Dec. 28, 1954 that such removal is necessary to enable the cast-article to perform its-expected function.
Hard metal carbide powdered materials as used herein are intended to include all the refractory hard-metal carbide powders which are used as ingredients in manufacturing commercial carbide products, having added hard metal carbide thereto as a binder an iron group metal, such as, for example, tungsten carbide, tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide and mixtures thereof together with a binder of the iron group, preferably cobalt.
The purpose of the casting vehicle is to give the dry powdered materials suflicient fluidity to permit the pouring-thereof without heating, and also by polymerization to bond the powdered materials into a hardened body so that the mold may be removed and the cast article handled or even mechanically Worked where this is-desirable.
1 ing vehicle for hard metal results 1 when an unsaturated mixed with a vinyl derivative such as styrene-is diluted The unsaturatedpolyesters of the maleic type for example, reaction products of a polyhydric alcohol and maleic acid or anhydride mixed with a vinyl derivative such as styrene form an excellent material for cold cast plastics, but when they are used alone they are not satisfactory as casting vehicles for my process as they-cannot be conveniently' removed from the cast cementedcarbide -articie. I
have found, however, that a conveniently-removable'castcarbide powdered materials polyester of the maleicstype 'with a miscible andnonpolymerizable organic liquid. The
nonpolymerizable liquid should preferably be' relatively simultaneous application of heat and pressure =toproduce a fully sintered carbide body-as disclosed in-Hoyt'U. S. Patent 1,843,768 and Gilson U:S.- Patent 1,756,857. The process of forming carbide articles byextrusion-iis disclosed in Taylor U. S. Patent 2,271,960. r'The'se three methods provide a largevarietyof simple and-semi-complicated shapes, but all of these methods are generally limited to planar variations from rectangular;triangular or cylindrical base shapes.
-- highboiling but-should be removable by evaporation below 150 C. Moreover, the combination of nonpolymerizable and polymerizable ingredients must be such that a gel forms-upon polymerization. When such acombination is employed the cast article- Will havesufiicient strength even though the major fraction of the vehicle consists of nonpolymerizable liquid. The major fraction It is one of the objects of the present invention to provide a process for forming cemented carbide articles of extremely complicated shapes which are not limited to planar variations from rectangulantriangular .or cylindrical base shapes. provide a process for forming cementedcarbide articles of complicated shape which eliminates the necessity for mechanical forming in the partially sintered state.- i It is a further object to provide a casting composition for cast- A still further object is to provide a process for casting cemented carbide articles of ing such complicated shapes.
complicated shape which is simple, efficient and inexpensive.
The manufacture of cemented carbide articles by my process contemplates the steps ofmixin'g hard metal carbide powdered materials .with an'organic casting vehicle,
casting this mixture into a wax, glue or preshaped mold at room temperature :without the -application of pressure, polymerizing the. casting vehicle to harden the cast article, expelling the casting vehicle from the. formed article and, finally sintering.theformed-article to produce a hard sound...ce me'ntedcarbide article. The
other inexpensive process differs fundamentally from the castingj ofdhermoplastic or thermosetting,materials,..in the respe t; that the casting or binding-vehicle .is .not presentli-n the, finally sintered cemented carbide article;
a closely packed pulverulent .hard,meta1...formed1.article without destroyingthe shape of gthe articleor-iietrimentally alfecting .its, propert1es,. is diificult, but .it. willbdunderstood Another object of my-mventiong is to -strength. Organic I immiscible ;or to 'cause separation upon polymerization of the vehicle, consisting of nonpolymerizable liquid, can
then be expelled from the cast article by evaporation below 150 C. rendering the cast article sufiiciently porous so that the-polymerizable fraction can be rapidlydecomposed and expelled at higher temperatures without cracking the article.
If thenonpolymerizableliquid-is not initiallyr'niscible with the polyester or if separation occurs upon polymerization, the resulting casting will not have the required liquids which have been found to be are,.for example, ethylene glycol, diethylene glycol, glycerine,ipropylene glycol and polyhydroxy compounds in general.
The use of organic liquids containingchlorine, bromine or fluorine should also'be avoided.
Casting vehicles which I have found IO'bB. satisfactory are comprised of anunsaturated-polyester.of the= maleic macid type, and preferably an'alkyd resin more particularly disclosed and claimedin a .Jrom:maleicanhydride, -dipropylene.glycol and tetrahydrofurfuryl alcohol,
' taining compound, for example, a vinyltderivativei such as Agens : Patent 2,3 19,5--: prepared a terminallyunsaturated CH2=C constyrene, vinyl acetate etc., initially miscible nonpolymerizable. liquid ethers or esters of ethylene glycol or diethylene. glycol such as diethylene glycol monoethyl ether "acetate, ethylene glycol monoethyl ether acetate, glycol diacetate, ethylene glycol monomethyl ether acetate, mixtures "of diethylene glycol with one of the abovenamed I Theconvemenhremoval of the polymerizedcastmg. vehicle from the interstices of acetates, etc., and a polymerizationicatalyst, as for in- .:';stance;:.benzoyl peroxide, ditertiary butyldiperphthalate, etch: .Thesecompositions are. convertible .by the application evolution-of water vapor into an inorganic liquid=mayhe removed.: below of heat ,without the fusible gel, and the heavy carbide constituents before hardening occurs.
150 C. in air without decomposing the polymer. The initially miscible, nonpolymerizable organic liquid should amount to about 65% to about 83% of the volume of the casting vehicle. If the vehicle contains less than about 65 of organic liquid the drying time is increased and it becomes very difficult to expel the vehicle without cracking the cast article. On the other hand, if the organic liquid is present in amounts greater than about 83%, the polymerizable ingredients will not impart sufficient green strength to the cast article to allow mechanical working or handling.
It will of course be apparent to those skilled in the art that polymerizable compositions other than those disclosed above may also be used without departing from the scope of the invention. Additional examples of maleic polyesters, terminally unsaturated compounds copolymerizable therewith, and polymerization catalysts may be found in U. S. 2,450,682 issued October 5, 1948, and
in U. S. 2,443,735 issued June 22, 1948.
I have also found that the above compositions are particularly suitable as a casting vehicle for my process in that they form a thixotropic gel when mixed with the powdered hard metal carbide or carbides. The vehiclecarbide mixture is capable of undergoing isothermal, reversible sol-gel transformations, a fluid sol existing as long as the mixture is agitated, the sol reverting into a gel within a short time after agitation has ceased. This property is important because it permits the use of a mixture which is fluid enough to pour while agitated, stirred or vibrated, but which prevents appreciable settlingofhe on heating the thixotropic mixture after casting, the ve- -hicle polymerizes into an infusible product which is no longer capable of reversion into the fluid sol state. The prevention of settling greatly reduces the unequal d1str1- bution of the carbide powders in the casting and thereby keeps distortion on sintering to a minimum.
The above compositions have the following properties: during agitation they are fluid enough to be cast at room temperature without the use of pressure; they are sufficiently thixotropic to prevent excess settling of the heavy constituents of the carbide powdered materials before permanent setting or solidification by polymerization occurs; they will cold set at room temperature or 4 harden with the application of heat; they impart sufficient green strength to the casting to allow handling and even mechanical working; they are conveniently removable bv heating without cracking the article or destroying its shape; and they leave no detrimental residue to aifect the physical properties of the finally sintered article.
In accordance with my invention, casting mixtures falling within the following approximate volume percentages have been used advantageously:
Percent Hard metal carbide powdered materials 38-415 Polymerizable ingredients -20 Nonpolymerizable liquid 48-415 Polymerization catalyst 0.1-0.75
By volume percentage in relation to the powdered hard metal carbide or carbides I refer to a calculated volume which is determined by dividing the weight of the powdered carbides by the final sintered density of the carbide material, which density is a well known quantity for any particular carbide composition to those who are skilled in the art.
The above limits have been found applicable to the casting of powdered ingredients used in the manufacture of cemented carbides, such as tungsten carbidecobalt mixtures in which the cobalt varied from 6 to by weight; to tungsten carbide-tantalum carbide-cobalt mixtures in which the tantalum carbide varied to a maximum of 27% by weight; to tungsten carbide-titanium carbide-tantalum carbide-cobalt mixtures, and. to tungsten carbide-titanium carbide-cobalt mixtures in which the titanium carbide varied to a maxium of 32% by weight.
Particle size of the cemented carbide powdered materials has a slight eifeet upon the amount of casting vehicle which is required, with more casting vehicle being needed as the particle size decreases. The above limits relate to carbide powdered materials of normal commercial particle size.
Typical compositions which have been cast are as follows:
Vol. Per- Measured Quancent titles Hard metal carbide powdered material,
94% WC+6% Co 39. 6 1 Kilogram. Styrene 8.1 13.7 cc. Unsaturated maleic polyester 6.3 10.6 cc. Diethylene glycol monethyl ether acetate.. 45.8 77 cc.
Benzoyl peroxide 2 .3 cc.
Hard metal carbide powdered material,
80% WC+20% Co 38. 6 1 Kilogram. Styrene 7. 8 14.9 cc. Unsaturated maleic polyester 6. 0 11.5 cc. Diethylcne glycol monoethyl ether acetate- 47. 5 91 cc.
Bcnzoyl peroxide 0. 1 .2 cc.
Hard metal carbide powdered material,
84% WC+16% Co 37. 8 1 Kilogram. Styrene 7. 8 14.9 cc. Unsaturated maleic polyester 6.0 11.5 cc. Diethylene glycol monoethyl ether acct e- 48. 3 92 cc.
Bcnzoyl peroxide 1 0.2 cc.
9 Hard. metal carbide powdered material,
87% WO+13% O9 39.0 2.3 Kilograms. Vinyl acetate (distilled) 7. 2 30 cc. Unsaturated malcic polyester 5. 8 24.2 cc. Ethylene glycol monocthyl ether acetate 47. 8 198 cc. Benzoyl peroxide .2 .75 cc.
Hard metal carbide powdered material,
57% WG+27% TaC+16% Co 37. 8 2.2 Kilograms. Styrene 7. 7 33 cc. Unsaturated maleic polyeste 6. 0 25.7 cc. Diethylene glycol monoethyl ct e. 48. 4 207 cc. Benzoyl peroxide 1 .3 cc.
Hard metal carbide powdered material,
61% WO+32% TlC+7% Co. 40. 2 1.53 Kilograms. Styrene 7. 6 31.8 cc. Unsaturated maleic polyester 5. 9 24.8 cc. Di ethylene glycol monoethyl ether acetate- 46. 2 193 cc. Diternary butyl diperphthalatc 1 .3 cc.
Hard metal carbide powdered material,
76% WC+4% 'la0+12% '.liO+8% Co. 38.8 1.19 Kilograms. Styrene 7. 6 31.8 cc. Unsaturated malcic polyester 5. 9 24.8 cc. Ethylene glycol monocthyl ether acetate 47. 6 198 cc. Ditcrtrary butyl diperphtlmlate 1 .3 cc.
I have also found that the time required for evaporating the n0npolymer1zable organic liquid from the solidified casting can be considerably reduced by adding a liquid which spontaneously exudes from-the casting after polymerrzation. Thus, by employing ethyl butanol as a substitute for diethylene glycol monoethyl acetate a gel exhibiting syneresis is formed upon polymerization and the time required for removal of the organic liquid may be reduced by as much as 50%, using the same 'procedures.
When ethyl butanol is used, however, the surface tends to become crusty or irregular. A more satisfactory and controllable composition can be made from a mixture of diethylene glycol and ethylene glycol monoethyl ether acetate. The degree of syncresis can then be increased and evaporating time decreased by increasing the proportion of diethylene glycol in the mixture.
A formulation which has been found to give good results comprises:
VoLPer- Measured cent Quantities Hard metal carbide powdered material, 87%
WC+13% Co 38.6 1 Kilogram. Styrene 7.8 14.3 cc. Unsaturated Ina-1cm polyester comprising a tctrahydrofurl'nryl alcohol modified dipropylene glycol maleate 6. 1 11.1 cc. Diethylene glycol. 11. 5 21 cc. Ethylene glycol mo aceta 35.9 63 cc. Bcnzoyl peroxide 1 .3 cc.
. The accompanying drawings illustrate certain features employed in the practice of my invention. More particularly,
131g. 1 is a perspective view of the mixing apparatus which may be used 1n carrying out my process.
F g. 2 1s a sectional view along line 2--2 of Fig. 1. Fig. 3 1s a s1de v1ew section of a typical mold that may be employed in my process.
In mak ng an article of the type which would result from casting my molding composition in the mold of Fig. 3,I first select thehard metal carbidepowdered ingredients which experience has taught will;possess the desired:characteristics for the application in.:;which the article ,-.is=-to-be used. The desired measured quantity of hard me'tal carbidepowdered ingredients which are in a finely groundcondition inaccordance with commercial. practice, ,is' placed in hopper.1 sealed with an air tight rubber seal.2 and. having a butterfly valve 3 actuated by crank 3 for controlling the release-of carbide. powdered ingredients 4 into-mixing chamber 5. MlXllJg chamber 5 is attached toa'the plate-6::bymeans of screws 7 forming an air tight seal therewith. Stopcock valve. Son mixing chamber. 5 and rubberseal 2 are closed and hopperland mixingchamber 5.are evacuated through 1ines 9and 10 which are connected to a commercialrvacuum pump. After evacuation, valve 11.0n l1ne.9 and valve 12 in line 10- are closed so that hopper 1 and :mixing chamber 5 remain evacuated. Equal weights of styrene or vinyl acetate and unsaturated maleic polyester are mixed together. to form a standard stock casting vehicle. 'A measured quantity of this mixture is thenadmixed with the desiredamount of the nonpolymerizable. organic liquid and if desired, diethylene glycol and, immediately prior to the actual mixing'with the cemented carbide powdered materials, the catalyst added and admixed. My liquid casting vehicle 13 is then placed into fluid inlet 14 and allowedtoenter into mixing chamber 5 through valve 15. Motor 16'which is attached to cross member 17 by strap 18"is'started and drives stirrer 19 at approximately 10,000 R. P. M. through housing 20 and air tight bushing 21; with stirrer 19 rotating the carbide powdered ingredients are admitted into mixing chamber 5 through valve 3 and therein mixed With the casting vehicle 13 for approximately 1 to 1 /2 mmutes. It may be seen in Fig. 2 that the inside surface of mixing chamber 5 is not cylindrical, but rather is irregular as shown to facilitate thorough mixing.
After mixing, the vacuum is released on mixing chamher 5 and my casting composition is ready for casting into a typical mold such as that shown in Fig. 3. This is accomplished by opening valve 8 and allowing the mixed castlng composition to fill the mold. The mold may be under vacuum if desired, or it mav be open to atmospher1c pressure. I have found that casting in an evacuated container is beneficial when the surface configurations are of fine detail involving minute cavities in the mold in order to obviate the tendency to bridge over these cavities, but otherwise casting in air is perfectly satisfactory. I have also found that tapping on the side of mixing chamber 5 aids the continuous flow of the thixotropic casting composition, and it will be appreciated that this may be accomplished by vibrations supplied from vibration apparatus if desired.
Mold materials which I have used successfully include wax, glue, Woods metal, aluminum, steel, etc., but I prefer wax or glue due to their cheapness, availability and ease of manufacture into the shape desired. Specifically, I have successfully used paraffin, casting waxes and micro-crystalline waxes and special glue mold materials which are commercially available.
After the mold is filled, the casting composition is allowed to stand therein until it hardens; the time required for polymerization or hardening will depend upon the actual casting composition used and the temperature, as well as the size of the article. In general, higher amounts of catalyst and higher temperatures speed up the hardening. Hardening will occur at room temperature but higher temperatures cause hardening in shorter periods of time. I have found that sufiicient hardening occurs at approximately 80 C. in approximately four hours.
After removing the hardened articles from the mold, the next steps in my process comprise removing the sol vent and polymer from the cast article. The first step is accomplished by placing the article in a drying furnace at 45 C. to 150 C. for 2 to 5 days depending upon the size and shape of the article with the larger articles requiring proportionately more time. After this initial heating period which expels the solvent, the second step is to expel the polymer by heating in a hydrogen or other inert atmosphere at 450 C. to 800 C. for approximately one hour.
Thereafter the article is sintered in a hydrogen atmosphere furnace at approximately 1350" 0-1500 C. for l to 2 hours and the resultant product is a fully formed,
hard, sound cemented carbide bodyhaving=;allz-.-the prop-r erties of a cemented carbide body of simpler-shapet).
.- The selection of: the-specific casting:vehiclenfor the manufacture of any specific article .withintheilimitshere-2 inbefore-set forth will depend somewhat uponthe size and shape of the article to be manufactured. For-ex.--
ample, small articles or articles havingthin wall sections:
which are easily dried but not easily handled. without being damaged should be cast using the'higherpercenv age of polymerizable ingredients :to increase their-green strength, while largearticles' should be cast usingaihighen percentage of nonpolymerizable solvent to improvetheir:
provides a method which is useful in manufacturing semi-1 complicated shapes that are presently manufactured by; known forming methods. My process has theadvantages of reducing labor operations involving the usev of forming machinery and the elimination of carbide ingredient. losses in the mechanical forming operations, as well as allowing casting in inexpensive molds at room'temperature.
What I claim as new and desire to secure'by Letters. Patent of the United States is:
l. The process for making hard metal carbidearticles of complicated shape which comprises the following steps: (1) preparing a thixotropic casting composition comprising a mixture of finely pulverized refractory hard metal carbides and an iron group metal, a casting vehicle consisting of styrene and the reaction product of a polyhydric alcohol and maleic acid and a nonpolymerizable organic liquid having an appreciable vapor pressure below C. selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate and ethylene glycol monomethyl ether acetate and a polymerization catalyst, (2) casting the mixture into a mold, (3) heating to effect hardening of the cast article, (4) heating the cast article to drive off the nonpolymerizable organic liquid, (5) heating the cast article to drive off the polymerized ingredients, and (6) finally sintering the cast article into a dense hard metal carbide body.
2. A casting mixture comprising a thixotropic mixture of about 38% to about 41.5% by volume of hard metal carbide powdered materials, 10% to about 20% of a mixture of the reaction product of a polyhydric alcohol and a butenedioic acid and a terminally unsaturated CH2=C containing compound and about 41.5% to about 48% of a nonpolymerizable organic solvent capable of dissolving the said copolymerizing mixture prior to polymerization selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate and ethylene glycol monomethyl ether acetate, and a small amount of a polymerization catalyst.
3. A casting mixture comprising a thixotropic mixture of about 38% to about 41.5% by volume of hard metal carbide powdered materials, a copolymerizable mixture of vinyl acetate and the reaction product of a polyhydric alcohol and maleic acid in amounts of about 10% to about 20% and about 41.5% to about 48% of an organic solvent capable of dissolving the said copolymerizing mixture prior to polymerization selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate, and ethylene glycol monomethyl ether acetate, and a small amount of a polymerization catalyst.
4. A thixotropic casting composition comprising about 39% of tungsten carbide and cobalt by volume, said cobalt falling within a range of 6% to 20% by weight of the tungsten carbide, about 7.8% styrene. about 6.1% of a tetrahydrofurfuryl alcohol modified dipropylene glycol maleate, about 11.5% diethylene glycol, about. 35.9% diethylene glycol monoethyl ether acetate and about .15 benzoyl peroxide.
5. A process for casting hard metal cemented carbide articles comprising the steps of forming a thixotropic mixture by mixing (a) a powdered hard metal carbide composition, (b) an organic liquid casting vehicle comprising essentially a copolymerizable mixture of the re action product of a polyhydric alcohol and a butenedioic acid and a terminally unsaturated CH2=C containing compound, (0) an initially miscible and non-polymerizable solvent which has an appreciable vapor pressure below 150 C. selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate and ethylene glycol monomethyl ether acetate and (d) a small amount of a polymerization catalyst; casting the thixotropic mixture; heating the cast article to drive off the non-polymerizable solvent; subsequently heating the cast article to drive off the copolymer and sintering the cast article into a dense hard metal carbide object.
6. The process for making hard metal carbide articles of complicated shape which comprises the following steps: (1) preparing a thixotropic casting composition comprising a mixture of finely pulverized refractory hard metal carbides and an iron group metal, a casting vehicle consisting of vinyl acetate and the reaction product of a polyhydric alcohol and maleic acid and a non-polymerizable organic liquid having an appreciable vapor pressure below 150 C. selected from the group consisting of diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, glycol diacetate and ethylene glycol monomethyl ether acetate and a small amount of a polymerization catalyst, (2) casting the mixture, (3) heating the cast article to drive oil the nonpolymerizable organic liquid, (4) heating the cast article to drive ofl? the polymerized ingredients, and (5) sintering the cast article into a dense hard metal carbide body.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,369,689 Robie et a1. Feb. 20, 1945 2,403,213 DAlelio July 2, 1946 2,446,872 Ehlers Aug. 10, 1948 FOREIGN PATENTS Number Country Date 572,801 Great Britain Oct. 24, 1945 626,983 Great Britain July 25, 1949 OTHER REFERENCES Ellis: Chemistry of Synthetic Resins, Vol. 2. Published by Reinhold Publishing Corp., New York city, 1935, pages 862-864.

Claims (2)

1. THE METHOD FOR MAKING HARD METAL CARBIDE ARTICLES OF COMPLICATED SHAPE WHICH COMPRISES THE FOLLOWING STEPS: (1) PREPARING A THIXOTROPIC CASTING COMPOSITION COMPRISING A MIXTURE OF FINELY PULVERIZED REFRACTORY HARD METAL CARBIDES AND AN IRON GROUP METAL, A CASTING VEHICLE CONSISTING OF STYRENE AND THE REACTION PRODUCT OF A POLYHYDRIC ALCOHOL AND MALEIC ACID AND A NONPOLYMERIZABLE ORGANIC LIQUID HAVING AN APPRECIABLE VAPOR PRESSURE BELOW 150* C. SELECTED FROM THE GROUP CONSISTING OF DIETHYLENE GLYCOL MONOETHYL ETHER ACETATE ETHYLENE GLYCOL MONOETHYL ETHER ACETATE, GLYCOL DIACETATE AND ETHYLENE GLYCOL MONOMETHYL ETHER ACETATE AND A POLYMERIZATION CATALYST, (2) CASTING THE MIXTURE INTO A MOLD, (3) HEATING TO EFFECT HARDINING OF THE CAST ARTICLE, (4) HEATING THE CAST ARTICLE TO DRIVE OFF THE NONPOLYMERIZABLE ORGANIC LIQUID, (5) HEATING THE CAST ARTICLE TO DRIVE OFF THE POLYMERIZED INGREDIENTS, AND (6) FINALLY SINTERING THE CAST ARTICLE INTO A DENSE HARD METAL CARBIDE BODY
4. A THIOXTROPIC CASTING COMPOSITION COMPRISING ABOUT 39% OF TUNGSTEN CARBIDE AND COBALT BY VOLUME, SAID COBALT TUNGSTEN CARBIDE, ABOUT 7.8% STYRENE ABOYT 6.1% THE TUNGSTEN CARBIDE, ABOUT 7.8% STYRENE ABOUT 6.1% OF A TETRAHYDROFURFURYL ALCOHOL MODIFIED DIPROPYLENE GLYCOL MALETATE, ABOUT 11.5% DIETHYLENE GLYCOL, ABOUT 35.9% DIETHYLENE GLYCOL 11.5% DIETHYLENE ACETATE AND ABOUT .15% BENZOYL PEROXIDE.
US166180A 1950-06-05 1950-06-05 Method of making cemented carbide articles and casting compositions therefor Expired - Lifetime US2698232A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3112283A (en) * 1959-09-10 1963-11-26 Chrysler Corp Molding composition comprising unsaturated monomer modified polyester and filler
US3115698A (en) * 1960-02-29 1963-12-31 Gen Electric Casting metal powders
US3131239A (en) * 1957-04-26 1964-04-28 Commissariat Energie Atomique Method of manufacturing porous barriers
US3859056A (en) * 1972-02-17 1975-01-07 Sumitomo Electric Industries Cemented carbide intermediate therefor and process for producing the same
US20070186721A1 (en) * 2006-01-09 2007-08-16 Sandvik Intellectual Property Ab Method of gel-casting a cemented carbide body slurry and gelled body

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2369689A (en) * 1941-11-06 1945-02-20 Carborundum Co Abrasive articles and methods of manufacturing the same
GB572801A (en) * 1942-01-24 1945-10-24 Edward Alexander Seeley Improvements in or relating to the production of shaped articles of sintered metals
US2403213A (en) * 1944-06-16 1946-07-02 Prophylactic Brush Co Synthetic resin bonded abrasive
US2446872A (en) * 1941-12-04 1948-08-10 Gen Motors Corp Method of molding ceramic articles
GB626983A (en) * 1946-12-09 1949-07-25 William David Jones Metallic castings

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2369689A (en) * 1941-11-06 1945-02-20 Carborundum Co Abrasive articles and methods of manufacturing the same
US2446872A (en) * 1941-12-04 1948-08-10 Gen Motors Corp Method of molding ceramic articles
GB572801A (en) * 1942-01-24 1945-10-24 Edward Alexander Seeley Improvements in or relating to the production of shaped articles of sintered metals
US2403213A (en) * 1944-06-16 1946-07-02 Prophylactic Brush Co Synthetic resin bonded abrasive
GB626983A (en) * 1946-12-09 1949-07-25 William David Jones Metallic castings

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3131239A (en) * 1957-04-26 1964-04-28 Commissariat Energie Atomique Method of manufacturing porous barriers
US3112283A (en) * 1959-09-10 1963-11-26 Chrysler Corp Molding composition comprising unsaturated monomer modified polyester and filler
US3115698A (en) * 1960-02-29 1963-12-31 Gen Electric Casting metal powders
US3859056A (en) * 1972-02-17 1975-01-07 Sumitomo Electric Industries Cemented carbide intermediate therefor and process for producing the same
US20070186721A1 (en) * 2006-01-09 2007-08-16 Sandvik Intellectual Property Ab Method of gel-casting a cemented carbide body slurry and gelled body
US7666349B2 (en) 2006-01-09 2010-02-23 Sandvik Intellectual Property Ab Method of gel-casting a cemented carbide body slurry and gelled body

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