CA2320546A1 - Fluid composition for electrical discharge machining - Google Patents

Abstract

A dielectric fluid for electrical discharge machining which contains an ester of branched acids and branched alcohols. The dielectric fluid reduces fire hazard during use due to a high flash point. In addition, the dielectric fluid has very low odor, is non toxic, and has good biodegradability.
Improved surface finish or production speed can be achieved. A phosphite containing additive is shown to improve color stability.

Description

FLUID COMPOSITION FOR ELECTRICAL DISCHARGE MACHINING
Field of the Invention This invention is directed to fluid compositions for use in electrical discharge machining, also called electrical spark machining.
BackarQUnd of the Invention Electrical discharge machining is g~n~rally known in the pertinent technology field as a process for the removal of electrically conductive materials from a workpiece by taking advantage of artificial electric sparks. The two major components employed in an electrical discharge machining process are a machine tool and a power supply. An electrode connected to the power supply advances into the workpiece to produce a shaped cavity. During this operation which produces the cavity on the workpiece, the electrode never actually touches the workpiece, but is instead separated therefrom by a small spark gap. The electrode is moved toward the workpiece until the space between the workpiece and the electrode is sufficient to ionize the dielectric fluid surrounding the piece and allow an electrical discharge (spark) to pass from the electrode to the workpiece. Consecutive spark discharges are pulsed on and off at high frequency. Each pulse or electrical discharge melts or vaporizes a small area of the workpi~ce surtace. This vaporized/melted metal is cool~d in the surrounding dielectric fluid where it solidifies into small particles. The particles are then flush~d away by the dielectric fluid. This flushing process is critics! to high metal removal rates and good machining conditions.
Electrical Discharge Machining (EDM) Fluids (Spark Erosion Fluids) are very important in the EDM process as they influence machining _2_ performance, machining quality, and h~alth and environmental quality of the process. The fluid functions to insulate the electrodes from each other, so that breakdown occurs only when the distance between the electrodes is small. The fluid also functions to insulate the electrode from the workpiece, so that breakdown occurs only when the distance is small. The size of this distance for a given discharge voltage depends on the breakdown strength (or dielectric strength) of the fluid. In service, high dielectric strength results in a small~r gap and accurate copying, but too high a strength can result in higher electrode wear and slower machining speeds. The fluid further provides the high pressure flushing necessary for the removal of molten material and ~rosion particles, and cools the gap to recover the insulating property after a discharge. The fluid must be filtered to remove coarse particles which can lead to process failures and short circuits. However, a certain amount of finely dispersed particles can be desirable as the particles increases the conductivity of the oil.
The properties of the EDM fluid which are commonly thought to be desirable include but are not limited to some of the following: Ivw viscosity, which allows the fluid to flow rapidly though the spark gap, to flush away particles, and to remove heat; sufficient flash point, which helps to eliminate potential for fire hazard; low vaporization tendency; good separation characteristics, with regard to separation of th~ fluid from metal particles, which facilitates the rapid removal of the particles from the work area; and, finally, chemical stability and aging stability, which relates to the fluid not attacking other materials employed during the process, not emitting noxious fumes, resistance to breakdown under operating conditions, and low coking tendency.
Most fluids commonly used in plunge type EDM applications are highly refined petroleum fractions. In some cases, synthetic hydrocarbon oils have been used, such as those described as polyalphaalefins.

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(n addition, Ohhazama, et. al (US Patent 5,136,116) disclosed the use of selected mineral oils or synthetics oils and blends thereof combined with small amounts of alkylbenzenes. The synthetic oil or mixture thereof as described in this disclosure consists of polybutenes, alpha-olefin oligimers, alkylnaphaline diesters, polyol esters, polyglycols, silicone oils, n-paraffins and iso-paraffins.
Another approach, set forth in US Patent No. 5,049,257 to Furukawa, involves using a low viscosity mineral oil or synthetic oil as the base oil, and adding an ultrahigh-viscosity oil to raise the efficiency of chip removal.
In another instanc~, a non-combustible aqueous dielectric fluid for electrical discharge machining which contains an ester solution is suggested. The ester is selected from the group consisting of acetate ester, carbonate ester and phosphate ester. In each case the ester has a flash point greater than 100°C. Examples of the carbonate ester include ethylene carbonate and propylene carbonate. These are taught in US Patent No.
4.536,633 to Onizuka.
It is common practice to include an additive formulation with components such as corrosion inhibitors, rust inhibitors, oxidation inhibitors and anti-foaming agents. Since it is desirable to see the workpiece as it is submerged in the EDM fluid, color stabilizers are also desirable in some instances. Although not generally used, it is conceivable that dispersants, coupling agents, surfactants, tube flow improvers, diluents, detergents, and pour point depressants can be included.
In Yatomi, et al., U.S. Patent 5,081,333, rust inhibitors for electrical discharge machining solution which contain a fatty acid amide are suggested, The machining solution comprises a fatty acid ester of polyglycerin, which is principally of a monoester. Yatomi describes the Invention as it relates to improvements in electrical discharge machine solutions of the aqueous solution type, and also improvements in electrical discharge machining processes which make use of an electrical discharge machining solution of the aqueous type. The solution is intended to replace conventional fluids, such as k~rosene, which have the drawback of being highly flammable liquids. Kerosene gas once evaporated and vaporized tends to catch fire due to spark or a pillar of arc produced upon electrical discharge, with the inherent drawback that it involves high fire hazards.
More recently, there have been used EDM fluids using a dielectric with conductive powders. This technique uses an EoM fluid with suspended electroconductive powders that improve the quality of the workpiece surface in the finishing stages of EDM. This technology has recently been introduced in commercial machines, Mineral oils and hydrocarbon fluids, including kerosene, typically used for EDM operations do not have a sufficiently high flash point, i.e., in excess of about 100°C, necessary far safebperation. Moreover, these fluids can have a disagreeable odor, Another problem with mineral oils is that they tend to cause skin irritation and rashes if the operator comes in contact with the oil, Synthetics, such as silicones, chlorinated oils and fluorinated oils, have been proposed to eliminate fire hazards, However, silicone and fluorinated oils are too expensive to be commonly used and chlorinated oils are too toxic, Aqueous mixtures of esters have been proposed, however evaporation of the water component during continuous operation can cause the fluid to become flammable or alter the physical characteristics thereof, which can then affect the machine performance of the fluid.

Summary of the Invention ft is the object of this invention to provide an improved fluid for electrical discharg~ machining which overcomes the foregoing disadvantages. The inventive EDM fluid disclosed herein exhibits a higher flash point than Commonly used hydrocarbon fluids and mineral oils, and further provides good machining performance.
Another object of the invention is to provide a dielectric fluid for EDM that addresses health and environmental concerns, i.e., is not malodorous, is non-toxic and has no ill effect on the working environment.
The EDM fluid in accordance with this invention, which meets the foregoing criteria, comprises a low viscosity ester fluid made from branched acids and branched alcohols. It is intended for use as the base oil in the EDM composition, to which additives as previously noted may or may not be added.
Detailed Descri tion of the Invention The invention is characterized by the use of an ester as a dielectric fluid for electrical discharge machining (EDM) processing. The preferred ester should have a flash point of at least about 120 degrees C. It is desirable that the ester be non-toxic and not cause skin irritation. It is also desirable that the ester be easily biodegradable. These properkies can be achieved using an ester which is the reaction product of branched acids and branched alcohols. Preferably, the branched alcohol is one having the general formula:

R(OH) wherein R is an aliphatic or cyclic aliphatic group having from about 2 to about 20 carbon atoms and wherein n is 1. The branched acid is preferably one having a carbon number of about CS to about Coo.
By way of example, and not wishing to be bound by any specific parameters of this ~xample, but rather offering the same as a means of helping the skilled artisan better understand the full invention, the following sets forth the manner in which an ester, Ester A, was prepared in keeping with the subject invention. Ester A was prepared from 2-ethylhexanol and 2-ethylhexanoic acid. The typical physical prop~rties of this ESTER A ar~
shown in Table 1.
Table 1 - Typical Properties of Ester A
Viscosity at 40 C, cSt 2.7 ASTM D-445 Flash Point (COC), C 135 ASTM D-92 Specific Gravity, 20/20 C 0.86 ASTM D-4052 Biodegradability, % ~2 ASTM-5864 Dielectric Strength, kV @25 68 ASTM D-187 Dielectric Constant @ 25 3.5 ASTM D-924 C

Power Factor @ 25 C, % 0.20 ASTM D-924 Volume Resistivity @ 25 C, 7.7 x 10'ZASTM D-1169 ohm-cm Ester A is considered biodegradable under ASTM-5864 which requires a minimum biodegradability of 60°~. This property is increasingly important in modern manufacturing processes where the result in the dispersion of such lubricants into waterways, such as rivers, oceans and lakes, has generated substantial interest by the environmental community.
Ester A was used to supply a Raycon RB-20 EDM machin~.
The RB-20 power supply uses a solid state multi-vibrator oscillator to produce _7_ a wave signal, which is amplified and used to control power transistors on the power circuit board. Energy from the power output board is then used to produce the sparks at the electrical work piece spark gap. Settings were 50,000 sparks per second and 20 microseconds spark to spark. The finish selector was set to 7. A graphite electrode was used. After 20 hours of continuous manufacturing, the processing was evaluated. The machined parts exhibited a smoother finish, no skin irritation was detected by the operator, and no odor was detected. Particl~s were removed efficiently from the work piece and later separated rapidly from the fluid. A sample of the fluid showed no sign of deterioration when evaluated. It was observed that the fluid had cleaned deposits from the previous hydrocarbon oil from the system. It was also determined that the parts were kept clean with no signs of coking or deposit build-up on the parts or th~ machine components.
Table 2 :Typical Characteristics Property Test MethodEsterA PAO ''type Synthetic Premium Synthetic Hydrocarbon Fluid Appearance Almost Water WhiteAlmost Water White Water White Water White Odor Almost A~most Almost Almost Odorless Odorl~ss Odorless Odorless Density Ibs/gal 7.18 6.653 6,7 6.58 60F 15.6C

Gravi API D 1298 47.5 Flash, COC,D 92 138 >145 101 B5 eC

Pour Point,D 97 <-90 <-60 -26 -48 "C

Viscosity, D 445 2.7 5.54 2.37 2.35 cSt at 40C

DieleCtfiC D-1816 64 60 40 Not Available Stren th KV

Dielectric 3.5 2.076 Not AvailableNot Available Constant (1 ) PAO Is a Poly Alpha Olefin oligimer type Syntnetic rlyarocarnon.

_$-The data in Table 2 above demonstrates that Ester A exhibits a higher flash point than commercial products of similar viscosity. The exception is the Poly Alpha Olefin Synthetic Hydrocarbon (PAO) which has a much higher viscosity. High flash point is beneficial for safety. Ester A has a mild characteristic odor that is generally considered pleasant.
Viscosity is another important fluid characteristic. Low viscosity helps to provide fluidity through the spark gap and speeds particle removal.
This characteristic, combined with a higher density, improves heat transfer characteristics to improve cooling properties. All of the products shown in Table 2 have adequately low viscosity with the exception of the PAO. Low pour point is important for us~rs where product is stored outsid~ in cold climates.
One problem that is typical with ester type fluids is the increase in color after aging. This is not desirable in EDM applications as it makes it difficult for the machinery operator to observe parts being manufactured.
While it is well known that phosphate containing materials have helped to stabilize polyols, polyol esters, complex esters and diesters from changing color, it has previously been unknown if these materials have any influence on the subject materials. These phosphates include, but are not limit~d to:
amine phosphates, triaryl phosphates, trialkylphosphites, monodecyl-diphenylphosphite, Bis(2,4-di-t-butyl)pentaerythritol diphosphite, Distearyl pentaerythritol diphosphite, didecylphenylphosphite, triphenylphosphite, dioctyl-phenyl-phosphate, dihexyl-phenyl-phosphate, diisodecyl-phenyl-phosphite, diisooctyl-phenyl-phosphate, didecyl-o-methyl-phenylphosphite.
didecyl-p-methylphenylphosphite, Tris(2,4-di-tart-butylphenyl)phosphite, Cyclic neopentane tetrayl bis(octadecyl phosphate), 4,4'-Isopropylidene-diphenol alkyl (C12-C15) phosphate, Tris nonyl phenyl phosphate, biphenyl isodecyl phosphate , biphenyl isooctyl phosphate, Tris phenyl phosphate, tris-_g_ (3~hydroxy-4,6-di-t-butylphenyl) phosphate, tris (nonylphenyl) phosphate and tris-(3-hydroxy-hexadecylphenyl) phosphate. As shown hereinaft~r, phosphate can affect the EDM fluid with respect to several different fluid parameters, thus proving very beneficial.
The fluid must be oxidation resistant for long fife. For this purpose an antioxidant can be added in small amounts of up to a few percent by weight. Excessive amounts of additives can later deplete and settle out on machinery components or tEle parts being manufactured. The maximum amount depends on the type of additive used but is generally thought to be between about 0.01 % by weight and up tv about 5.0% by weight, more preferable between about 0.01 % by weight and up to about 1.5°r6 by weight.
Typical antioxidants include butylated hydroxy toluene, phenolic, or amine type antioxidants. Some suitable antioxidants are described in US Patent 5,892,051 to Wirth , et al. Phenolic imidazoline antioxidants and others are well known in the art. Phosphate additives, such as tris (nonylphenyl) phosphate, triaryl phosphates and trialkyl phosphates, have also be~n described as antioxidants and can be useful to this invention, possibly serving a dual purpose as a color stabilizer and an antioxidant. A more recent description of phosphates used as antioxidants has been described by Kikuchi, et al. in United States Patent No, 5,891,939.
The addition of corrosion and rust inhibitors can also benefit the EDM fluid by protecting not only the machining tool but also the parts being manufactured. High molecular w~ight phosphates can also act as a corrosion inhibitor. For example, amine phosphates are commercially sold as corrosion inhibitors and are thought to help catalytic decomposition at high temperatures in blends of carboxylic acid tetraester of pentaerythritol blended with phosphate esters with polyalphaolefin or alkylated naphthalene, as described in United States Patent No. 5,236,618, to Perez, et al.

As shown above, while the subject invention can, in one embodiment, be used in the commercially pure form, in another embodiment combination of the fluid with additives or its use in blends can also be desirable. For example, including a color stabilizer such as a phosphite, or an antioxidant, or corrosion inhibitor all are desirable for long duration applications. Further, there can be a cost benefit to blending the subject invention fluid with less expensive hydrocarbons, even polyalphaolefin oligimer type synthetic hydrocarbons. Blends with fluids such as the PAO in Table 2 can achieve different viscosity while maintaining or improving the flash point or other properties. For example, a mixture of 10% by weight of the PAO with 90°~ by weight of the Ester A was made. The resulting properties are shown in Table 3.
Table 3 :Typical Characteristics Property Test Ester A 90% wt.
Method PAO"~ type synthetic 1 O~
wt A earance Almost Water-White Odor Almost Odorless Density Ibs/gal 7.13 60F 15.B C

Flash, COC, D 92 140 F

Pour Paint C D 97 <-60 viscosity, cst D 445 2.7 at (1 ) PAD is a Poly Alpha Dleftn Oligimer type Synthetic Hydrocarbon (2) Test discontinued at -60°C

(3) No measurable difference from the pure component Ester A using this method The results indicate that a small improvement in flash point can be achieved without a major change in viscosity as measured using ASTM

D445. More importantly, the ability to blend the two components allows the formulator to adjust other properties of the finished EDM fluid. For example, esters tend to swell certain rubbers and elastomers used in seals whereas PAO type synthetic fluids tend to shrink these same materials which are used as o-rings and gaskets. The combination of the two can help tailor the fluid for a particular EDM machine manufacturer's choice of materials. Severely hydrotreated hydrocarbon oils mixed with the subject esters can also benefit by such blending as they also tend to shrink certain el~stomers.
Thermal and Color Stability Testing The affect of combining the subject EDM fluid with additives and blending it with other EDM fluids was tested to compare th~rmal and color stability. The test used was a simple oven test in the presence of steel. For this test, 300 ml of fluid was placed in each of several glass beakers, and steel rods of equal dimensions and composition were placed in each beaker.
The beakers were placed in an oven, open to the air for 20 days at 120 degrees C. At the end of the 20 day test period the samples were visually compared as shown in Tables 4 and 5.
Table 4 Ester PAO Premium Ester Ester Ester Ester "' A A A A l A type Hydro- AdditiveAdditiveAdditivePAO

SyntheticcarDOn 1 ~'~ 2 ~3~ 3 ~''~ Additive Fluid Appear- Yellowfight Yellow Very Yellow Very Very slight ance Yeliow slight slight yellow After yellow yellow da s Notes Nearly 50~

evapor-ates ~ ~ ~ rHV is a roiy Hipna merln vllgimer type Synthetic Hydrocarbon (2 cSt at 100 degree C such as Amoco Durasyn 162) (2) Additive 1 is a phosphite inhibitor Tris(2,4-di-tart-butylphenyl)phvsphite) at O.Z % by weight with the remaining weight being Ester A

(3) Additive 2 is 0.5°~ wt Ethyl 702, a commercially available sterically hindered phenolic antioxidant 4,4'-methylene-bis (2,6-di-tert-butylphenol) (4) Additive 3 is comprised of 0.03°~ weight of Tris(2,4-.di-tert-butylphenyl)phosphite, 0.5 °~6 wt Ethyl 702 with the remaining weight being Ester A

(5) A blend of Ester A at 90% wt and PAO (2 cSt at 100 degree C) at 10 °~ wt was first prepared, then this blend was mixed with Additive 3 such that the additive levels were approximately 0.03~~ weight of Tris(2,4-di-tert-butylphenyl)phosphite and 0.5 % weight Butylated Hydroxy Toluene in the final mixture, Table 6 Ester A Ester A Ester A / Ester A / PAO
Additive Additive PAO Additive 5 ~e~
4 ~~ 5 m Additive 4 ~8~

-Appear- Light yellowVery Light yellow Very slight light slight tan ance brown tan brown (almost colorless) After da s /G1 AiliJ:~:...~ w :- n a wn.
~ni ._ m_ ---w-- . .- ~----~.. ~~..~~~ ~. v~~wrcyy ~-vv ~a commercial alKyl-Substituted phenyl-alpha-naphthylamine, the balance of the mixture being the base fluid.
(7) Additive 5 is 0.2°~ weight Ciba Geigy L-06 and 0.1 % weight Tris(2,4-di-tert-butylphenyl)phosphite the balance of the mixture being the base fluid.
(8) A blend of Ester A at 90% weight and PAO (2 cSt at 100 degree C such as Amoco Durasyn 162) at 10 °r6 weight is first prepared, then this blend is mixed with the additives as described.
From the observations in Tables 4 and 5, it is seen that the phosphite additive effectively improved color stability in the case of Ester A.
The yellow color described in Table 5 was clear but definitely darker than the light yellow, which Was also clear in all cases. Similarly the slight tan described where the phosphite additive was used in Table 6 was much lighter than the light yellow brawn.

It was also noted that the premium hydrocarbon fluid had significant evaporation. A high level of evaporation can lead to excessive consumption of fluid. With regard to this parameter or characteristic of performance, the use of Ester A has a Clear advantage over the use of the hydrocarbon fluid and even greater advantage over hydrocarbon solvents such as kerosene or mineral solvents commonly used.
In a further test sample run (field test) a sample was used with the addition of 6% mineral oil. This sample run established that mineral oil was compatible with the products and methods of the present invention, thus using mineral oil of this concentration was beneficial. Additionally, the operator noted there is much less irritation to the skin than with the other sample fluids. Therefore, this composition has the desired qualities of being both non-toxic and not causing any skin irritation. Further, as the composition is easily biodegradable, this product is preferred for use in the methods of the present invention.
In addition to the additives set forth above, it is contemplated that other additives can also be included, such as dispersants, coupling agents, surFactants, tube flow improvers, diluents, detergents, pour point depressants, anti-foaming agents, color stabilizers and micro particles. Each of these additive categories is well known in the art, and given the physical data and specifications presented herein., the skilled artisan will be capable of selecting among potential common additives to achieve a desired result.
While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, as many modifications can be made, and it is, therefore, contemplated to cover by the appended claims any such modification as fall within the true spirit and scope of the invention.

Claims (28)

1. Electrical discharge machining fluid which comprises an ester from the reaction product of a branched alcohol having the general formula R(OH)n, wherein R is aliphatic or cyclo-aliphatic group having from about 2 to 20 carbon atoms and n is 1; and a branched acid having a carbon number in the range of C5 to C10; wherein said ester exhibits a flash point of at least 120 degrees C.

2. The electrical discharge machining fluid according to claim 1 wherein said branched acid has a carbon number in the range between about C5 to C10.

3. The electrical discharge machining fluid according to claim 1 wherein said branched acid is selected from the group consisting of 2-ethylhexanoic acids, isoheptanoic acids, isooctanoic acids, isononanoic acids and isodecanoic acids.

4. The electrical discharge machining fluid according to claim 1 wherein the branched alcohol is 2-ethylhexanol and the branched acid is 2-ethylhexanoic acid.

5. The electrical discharge machining fluid according to claim 1 wherein said fluid is a blend of a plurality of said fluids.

6. An electrical discharge machining fluid comprised of at feast 10% by volume of the electrical discharge machining fluid described in claim 1 added to a hydrocarbon fluid or synthetic fluid wherein the mixture has a flash point of at least 110 degrees C.

7. The electrical discharge machining fluid according to claim 6 wherein said said hydrocarbon fluids and synthetic fluid is selected from the group consisting of polybutenes, alpha-olefin oligomers, alkylbenzene, alkylnaphthalene, diester, polyol ester, polyglycol, polyphenyl ether, tricresyl phosphate, silicone oil, perfluro alkylether, n-paraffin, diphenyl alkane, iso-paraffin, highly refined hydrocarbon fluid, mineral oil, and mixtures therof.

8. The electrical discharge machining fluid according to claim 1 wherein a phosphite containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

9. The electrical discharge machining fluid according to claim 2 wherein a phosphite containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

10. The electrical discharge machining fluid according to claim 3 wherein a phosphite containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

11. The electrical discharge machining fluid according to claim 4 wherein a phosphite containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

12. The electrical discharge machining fluid according to claim 5 wherein a phosphite containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

13. The electrical discharge machining fluid according to claim 6 wherein a phosphate containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

14. The electrical discharges machining fluid according to claim 7 wherein a phosphate containing additive is added in the amount of at least 0.02% by weight to 5% by weight.

15. The electrical discharge machining fluid according to claim 1 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

16. The electrical discharge machining fluid according to claim 2 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM.5864.

17. The electrical discharge machining fluid according to claim 3 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

18. The electrical discharge machining fluid according to claim 4 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

19. The electrical discharge machining fluid according to claim 5 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

20. The electrical discharge machining fluid according to claim 6 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

21. The electrical discharge machining fluid according to claim 7 wherein said fluid exhibits at least 60% biodegradation in 28 days as measured by ASTM-5864.

22. The electrical discharge machining fluid according to claim 1; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, lube flaw improvers.
diluents, detergents, rust inhibitors, pour point depressants, anti-foaming agents, color stabilizers and micro particles.

23. The electrical discharge machining fluid according to claim 2; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, lube flow improvers, diluents, detergents, rust inhibitors, pour point depressants, anti-foaming agents, color stabilizers and micro particles.

24. The electrical discharge machining fluid according to claim 3; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surtactants, lube flow improvers, diluents, detetgents, rust inhibitors, pour paint depressants, anti-foaming agents, color stabilizers and micro particles.

25. The electrical discharge machining fluid according to claim 4; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, tube flow improvers, diluents, detergents, rust inhibitors, pour point depressants, anti-foaming agents, color stabilizers and micro particles.

26. The electrical discharge machining fluid according to claim 5; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, tube flow improvers, diluents, detergents, rust inhibitors, pour paint depressants, anti-foaming agents, color stabilizers and micro particles.

27. The electrical discharge machining fluid according to claim 6; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, tube flow improvers, diluents, detergents, rust inhibitors, pour point depressants, anti-foaming agents, color stabilizers and micro particles.

28. The electrical discharge machining fluid according to claim 7; and an additive package wherein said additive package comprises additives selected from the group consisting of corrosion inhibitors, oxidation inhibitors, dispersants, coupling agents, surfactants, tube flow improvers, diluents, detergents, rust inhibitors, pour point depressants, anti-foaming agents, color stabilizers and micro particles.