volume i1 theory and design - p2 infohouse · 2018-06-13 · cij'itiwg fluids ralph kelly and...

14
Volume I1 Theory and Design Editor E. Richard Booser, Ph.D. Senior Engineer Electromechanical Systems Engineering Turbine Technology Laboratory General Electric Company Schenectady, New York

Upload: others

Post on 07-Aug-2020

0 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

Volume I1 Theory and Design

Editor

E. Richard Booser, Ph.D. Senior Engineer

Electromechanical Systems Engineering Turbine Technology Laboratory

General Electric Company Schenectady, New York

Page 2: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

CIJ'ITIWG FLUIDS

Ralph Kelly and Gregory Foltz

INTRODUCTION /

The primary function of any cutting id is to control heat.' A cutting tool generates temperatures of 375 to 750°C and the resulting chip as it slides up the tool face creates

.tremendous pressures (up to 1,379,000 @a). About 75% of the heat is generated by de- formation of the metal, the other25% by friction between the chip and the tool. By controlling the temperature generated in the cut zone, tool wear can be controlled and tool life increased.2

As the cutting tool cuts (or the grinding wheel grinds), metal deforms by shear or plastic flow along a shear plane extending from the top of the tool to the surface of the metal (Figure 1). Below theshear plane is undisturbed metal; above it, the deformed metal forms a chip. Reduced friction at the chip-tool interface increases the shear angle, produces a thin chip, and deforms less metal.

Where a tool face is examined under a microscope, rough peaks and valleys can be seen (Figure 2). These tiny projections collide with the chip as it slides up the tool face and weld to the chip under the conditions of very high heat and pressure. Continuous shearing of these welds results in tool wear, the tip of the tool becomes cratered, and heat concentrates at this point. Small pieces of sheared-off metal form a built-up edge on the face of the tool, a major cause of poor surface finish.

When a cutting fluid is introduced between the tool and chip, friction is reduced, the shear angle increases, the chip becomes thinner, the power requirement is reduced, and less heat is generated. Also, the built-up edge disappears, the finish smooths out, and size control improves. The nascent metal exposed under the high temperature and pressure conditions reacts with chemicals in the cutting fluid to form a low shear strength solid between the chip and the tool. The chip slides freely up the tool face, tools last much longer, speeds and feeds can be stepped up, and more work can be done with each tool. The cooling and lubricating mechanisms are dependent on the job: slow-speed, slow-feed operations need more lubrication while high-speed, high-feed operations need more cooling.

TYPES OF C U " G FLUIDS3

Cutting Oils A cutting oil contains m

petroleum derivatives; fatty oils are derived from animal or vegetable sources. Extreme pressure (EP) sulfur, chlorine, or phosphorus additives are employed to improve

antiweld properties for heavyduty applications. Sulfur forms a better lubricant, but chlorine is more reactive than sulfur and brcaks down to form the EP lubricant at lower temperatures. Phosphorus is not as effective as either sulfur or chlorine and its use is less common. Cutting oils are often classified as active or inactive; an inactive dl will not darken a copper strip

Straight mineral dl - Used for light-duty machining of ferrous or nocfeno its major function is as the base fluid for ttae blends and additive oils listed below

Page 3: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat
Page 4: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

film in the machining process. This reduces friction and built-up edge, and provides antiweld properties. These oils are useful for machining tough, ductile metals. Reactivity of the sulfur makes them unsuitable for copper or copper alloys.

Sulfo-chlorinated mineral oil - Combination of sulfur and chlorine additives produces products with exceptional antiweld properties over a wide temperahue range. They are used for machining (especially threading) tough, low-carbon steels. Fatty oils added to this type of product produce a cutting oil for a wide range of heavy-duty and slow-speed operations.

Cutting oils generally provide the excellent lubrication needed in low-clearance, low- speed operations; especially where a high quality surface finish is required. They have good rust control. Sump life is long since rancidity-causing bacteria do not grow in pure oil unless it is contaminated with water. The straight-oil cutting fluids do allow buildup of excessive heat, since oil diksipates heat only half as fast as water and because it is much more viscous than water-based fluids. These oils are also somewhat of a safety hazard in that they smoke and bum. In addition, he i r high misting properties cause the parts and surrounding area to become slippery and dirty.

and better size control Soluble oils have se

filtration. ~n extreme cases, from a soluble oil can leav aad work areas in a messy, slippery condition.

Page 5: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat
Page 6: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

and wetting agents

Chemical solutions (synthetic fluids).

Gases and Solids Compressed air can be directed into the cut zone, both for heat removal and for removing

chips. Inert gases and those boiling below room temperature, such as carbon dioxide, may also be used. High cost generally outweighs any added benefits. Low-boiling point liquids like Freon@ (1,1,2 trichloro- and 1,2,2 trifluoroethane) are occasionally used where extremely clean parts are needed.

Solids are used on a verj. limited basis since they must be dispersed in some carrier. Some sulfur compounds ak d form a frlm on the workpiece in the same manner as extreme pressure additives.

CUnrNG FLUID SELECTION

Both needs of th es must b;: consi g fluid.4

e e

Page 7: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

a shop may dictate the cutting fluid selection.

between the chip and tool interface is minimal is considered iighr duty. Examples would be turning 1112 steel or surface grinding cast iron; (2 ) moderare-duty operations are those in which adhesion between the chip and tool is noticeable and contributes to poor fmishes and poor size control, Examples would be key seat milling and intemal race grinding; (3) a heavy-duty operation involves severe adhesion between the chip and tool. Examples would be sawing of large parts, deep slotting, or centerless grinding heavy parts; and (4) extremely heavy-duty operations involve extremely severe adhesion between the chip and tool and small tool clearances, thus creating severe rubbing conditions between the tool and work- piece. Examples are thmid chasing and tapping 4140 steel, deep hole drilling, or form and thread grinding. As severity increases, it may also be necessary to increase the lubricity of

of soluble oils for m

treatment, and many other factors can affect mac machinable, other metals are divided in Table 1 into six machinability classes. machinability classes have been used in the fluid selection chart of Table 2.

Page 8: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

Ferrous (>70%)

A 4 2 3 A 4 2 4 A-5120 8-1111 B-1112 B-1113 C-1016 C-1018 C-1019 c-1021 c-1022 C-1026 C- 1030 c-1109 C-1116 c-1 I17 C-1118 C-1119 c-1120 C-1137 C-1141 c-I144 Cast steel

Table 1 MACHINABILITY GROUPS

Ferrous eo- FUTOUS FwrouS Noatvrous (<40%)

A-23 17 A-1320 317 Aluminum Titanium A-3 t A- 1330 418 A4027 A-I340 440 A4028 A-2330 A-2515 A132 Ti-5AI-2.5Sn A4032 A-2340 53310 195 Ti-8Mn A-4937 A-25 15 E-50100 214 TidAI4V A-4042 A-3240 E-51100 355 Ti-84-IMo-IV A-4047 A4340 E-52100 A356 TidAI-6V-2Sn A4130 A 4 1 5 E-93 15 A357 Ti-13V-I ICr-34 A4145 A4820 Tool steel 750 A - s L A-6 120 201 1 Nickel

A-5 t 2024 Brass 3003

A* A-8645

5052 A-86_ A-8750

A-9445 A-98, 5056

6061 A-x C-1008 c- IO20 c-I010 C-1035 C-1015 7075 c-1040 C- 1050 C- 1045 C- 1070 Leaded brass C-1060 E-2512 Magnesium alloys C- IO70 E-33 IO wrought + cast

Ad150 2014 copper A-8650

A-87, 3004

Malleable iron E - 4 L Wrought iron zinc Stainless iron Cast iron ~ Stainless 18-8 Silicon bronze

Nore: These ratings were based upon a comparison with BI 112 stccl and given in AIS1 listings.

hard-water soaps to plug the filter media. Products that contain some emuIsified oil ag- glomerate the fines and create a better, inore open cake on the filter media. Solution-type fluids often allow dense chip packing on the filter media. If diatomaceous earth or other material is used as a precoat for the filter, a solution-type product is usually-needed since

ess is due mainly to calcium, magnesium, and €e wetting agents, and emulsifiers to form insoluble co

microbicides, coat p i p , q

Page 9: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

Ferrous Ferrous Nonferrous Nonferrous 70%) (50-705) (>-%) (e@%) (>loo%) (sloO%)

6. Sulfochlorinated mineral oil 7. Soluble oil 8. Chemical emulsion 9. Simple chemical solution

10. Complex chemical solution

Water-bascd fluids should not be used on magnesium grinding and great m m be used in fluid sel magnesium machining.

osmosis is beneficial.

often found in a cuttlng

cts may either reject tramp oil contamination tive solutions c8n increase alkalinity ro

Page 10: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

, aluminum, or their chemical attack. For products that are mixed,

r to avoid an inverted emuls

t program, but waste treatment at some time will be inevitable. Most prevalent waste is acidification followed by the addition of alum, ferric chloride or ferric sulfate, polyelectrolytes, or polymer-inorganic combinations. Physical methods axt based on separation of water from the pollutants by evaporation, distillation, filtration, ~ltrafilmtion,~~ reverse osmosis, cen- trifugation, or activated carbon. Many plants that generate insufficient waste to justify their own treatment have it hauled away by a commercial disposal company.

Freedom from U Side Cutting fluids should not leave an objectionable residue on either the parts or the machines;

and they should be nontoxic and noninitating to eyes, nose, and skin. R a n ~ i d i t y , ' ~ . ~ ac- companied by its unpleasant odors, should ideally be controlled by the product or by mi- crobicides added to the mix if needed. Rancidity can be controlled by good sanitation practices, correct concentration, aeration, and the use of good water. A cutting fluid should provide rust protection on parts for at least 72 hr under favorable conditions. Cutting fluid mixes should not smoke, bum, or damage paint on machine tools. Since World War 11, most machine tool manufacturers have changed to resistant acrylic, epoxy, and polyurethane coatings.

18

Performance vs. Costa1 Ail cost factors should be considered - tool life, cleaning the machines, resharpening

tools, part cleaning, recharging frequency, and a host of others. Performance factors in cutting fluid selection include tool life, fluid life, operator satisfaction, shop cleanliness, freedom from corrosion and rancidity, adaptability to several j , and elimination of health and safety hazards. /Y

C U " G FLUID CONTROLS

Control of nts as well

3. 4. 3-

Maintain the cutting fluid mix concentration at the Keep the cutting fluid free of chips and grit Use water that has a low dissolved solids content

6. Aerate the cutting fluid

Page 11: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

Improved tool life, better surface finish, lower power consumption, greater accuracy, and

and grinding, m3/sec = machining kW/i20

An exception to the rule of low under pressure, through the tool s problem in vertical milling, reaming, etc.

s in gun drilling. Here the cutting fluid is fed,

1. 2. 3.

For high stock removal, tank sizes obey the same formulas since flow rate has already increased in relation to machine horsepower.

Manual Application

Grinding - tank volume = flow/min X 10 Machining cast iron and aluminum - tank volume = flow/min X 7 Machining steel - tank volume = flow/min X 5

door frames where the machine is not equipped with a cutting fluid Mist application also makes the use of fluids practical with portable

according to Occupational Safety and Health Act (OSHA) regulations, chemical emulsions and chemical solutions are recommended. If soluble o

vided or mist coll

chip is formed using

Page 12: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

367

RGURE 6. High-velocity grinding nozzle.

or tapping through-holes with hollow-shank tools, a cutting-fluid retainer assures that all cutting edges will be flooded and that chips will be flushed from the hole. For thread chasing, direct the cutting fluid to the cutting edges of the tool; and when using a self-opening die, direct the cutting fluid ‘to each chaser in the die head. A ring-type distributor is most effective in intemai broaching.

High Pressure Application

&on reduced as the chip is formed. Tht heat produced

use of a special high-velocity be reduced to acceptable lid

uld be decreased flow should then

Page 13: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

368 CUC Handbook of Lubrication

Cutting fluids can be tested using procedures specified in the Federal Hazardous Substances Act for such factors as acute inhalation and oral toxicity, primary skin and eye irritation, and acute dermal toxicity. The Environmental Protection Agency (EPA) administers the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), which requires registration of bactericides and fungicides, many of which are used as additives for cutting fluids. In order to get EPA registration of a biocide, the manufacturer must run many tests which prove that the biocide is effective but not extremely harmful to aquatic life, wildfowl, and man.

The Department of Transportation (DOT) administers a law which governs the shipment of hazardous materials, including chemicals and cutting fluids. The law specifies appropriate labeling and training of all employees involved. If one reships between plant locations, or repackages, these regulations must be followed.

The Occupational Safety and Health Act (OSHA), enacted by Congress in 1970, sets 5 mg/m3 as the maximum allowable level of oil in air that operators breathe. This has resulted in installation of new ventilation or exhaust equipment in many shops. Other manufacturers switched to metalworking fluids which contained little or no oil.

Under the Clean Water Act of 1977, EPA will put severe restrictions on toxic pollutants in industrial effluents. Two alternatives exist: either eliminate products which contain ma- terials listed or install wastewater treatment equipment to remove the pollutants from the effluent.

Although there are no government regulations in the U.S. regarding nitrosamines in cutting fluids, the National Institute for Occupational Safety and Health (NIOSH) issued a 1976 Intelligence Bulletin, announcing the discovery of a nitrosamine, diethanolnitrosamine, in cutting fluids. NIOSH pointed out that, “Although nitrosamines are suspected to be human carcinogens, their carcinogenic potential in man has not been proved.”24 Diethanolnitro- samine forms from a reaction between secondary or tertiary amines (or both) and an oxide of nitrogen. Many manufacturers have removed the nitrite from their cutting fluids to elim- inate this problem. Tests are being conducted by NIOSH; in the meantime OSHA is con- sidering guidelines that probably will recommend housekeeping and hygiene measures.

On May 5, 1980, the EPA released the Resource Conservation and Recovery Act (RCRA), which deals with all hazardous wastes and affects all generators, transporters, and disposers. RCRA deals with the identification of wastes as hazardous based on the following charac- teristics; ignitability, corrosivity, reactivity, and toxicity. It also provides standards for

Only when a large volume of clean fluid bathes the tool and reaches the cutting zone are full benefits obtained from cutting fluids. Relatively simple, inexpensive modifications to existing machine tools will often increase tool life as much as loo%, improve surface finish, give greater accuracy, reduce or eliminate steam, smoke, and operator complaints.

SAFETY AND HEALTH FACTORS

facilities which store, treat, or dispose of hazardous wastes. A cutting fluid may be classified as hazardous depending on its composition or through contamination from use. Applicabili of RCRA regulations is dependent on individual ~i tuat ions.~~

Many additional state and local standards exist, covering all facets of the metalwo industry. Responsibility for compliance lies with both the manufacturers and the use

Page 14: Volume I1 Theory and Design - P2 InfoHouse · 2018-06-13 · CIJ'ITIWG FLUIDS Ralph Kelly and Gregory Foltz INTRODUCTION / The primary function of any cutting id is to control heat

REFERENCES

I . Cookson, J. O., An introduction to cutting fluids. Tribol. In t . . 5 , February 1977. 2. Merchant, M. E., Fundamentals of cutting fluid action, Luhr. Eng.. 163, August 1950. 3. Dwyer, J. J., Cutting fluids, Special Rep. 548, Am. Mach., 105, March 1964. 4. Kelly, R., Selection and Maintenance of Cutting Fluids, Tech. Pap. MR73-I IO. American Society of

5 . Springborn, R. K., Cutting and Grinding Fluids: Selection and Application. American Society of Tool

6. Joseph, J. J., Cleaning metalworking fluids, Am. Mach.. 75, March 1971. 7. Brandt, R. H., Fluid Longevity and Central Clar$cation Systems. Tech. Pap. MR74-171, American

8. Bennett, E. O., Water quality and coolant life, J . ASLE. 30, 549. 1974. 9. Bennett, E. O., The Effect of Water Hardness on the Deterioration of Cutting Fluids, Tech. Pap. MR72-

10. Suskind, R., Occupational skin problems, J. Occup. Med.. No. I , 39, 1959; No. 2, 119, 1959; No. 4,

1 1. Ciesko, R., The Effects of Water Soluble Cutting Fluids on Operating Conditions in Machining, Tech. Pap.

12. Rum, G. A., Coolant control of a large central system, J. ASLE, Preprint No. 79-AM-2A-I, 1979. 13. Tomko, J., Cutting Fluid Maintenance. Tech. Pap. MR7 1-804. American Society of Mechanical Engineers,

14. McCoy, J. S., A practical approach to central system control, J. ASLE. preprint No. 77-AM-IE-I, 1979. 15. Kulowiec, J. J., Techniques for removing oil and grease from industrial wastewater, Pollut. Eng. . 49,

16. Nemerow, N. L., Liquid Waste of Industry, Theories. Practices. and Treatment, Addison-Wesley, Reading,

17. Priest, W., Treatment of waste oil emulsions by ultrafiltration, Water Waste Treat.. 21, 42, 1978. 18. Vaughn, R. L. and Miller, H. B., Cutting Fluids and Environmental Compatibility. Tech. Pap. MR70-

19. Bennett, E. O., The biology of metalworking fluids, Lubr. Eng., 28, 237, 1972. 20. Rossmore, H. W., Microbiological Causes of Cutting Fluid Deterioration. Tech. Pap. MR74-169, Amer-

ican Society of Mechanical Engineers, New York, 1974. 21. Mason, J. W., Cost Savings Through Cutting Fluid Selection, Tech. Pap. MR69-259, American Society

of Mechanical Engineers, New York, 1969. 2 1 ASME, Machine Design Considerations for Improving Metalworking Fluid Performance. Tech. Pap. MR76-

252, American Society of Mechanical Engineers, New York, 1976. 23. Gettelman, K. and Fisher, R. C., The not-so-fine art of precision grinding, Mod. Mach. Shop, 78, April

1975. 24. Finklea, J. F., Current intelligence bulletin: nitrosamines in cutting fluids, U.S. Department of Health,

Education and Welfare, Washington, D.C., 1976. 25. Anon., Hazardous waste and consolidated permit regulations, Fed. Reg., 45(98), 33063, May 1980.

Mechanical Engineers, New York, 1973.

and Manufacturing Engineers, Dearborn, Mich., 1967.

Society of Mechanical Engineers, New York, 1974.

226, American Society of Mechanical Engineers, New York, 1972.

230, 1959.

EM75-380, American Society of Mechanical Engineers, New York, 1975.

New York, 1971.

February 1979.

Mass., 1971.

714. American Society of Mechanical Engineers, New York, 1970.