US3007871A

US3007871A - Water-base lubricant composition

Info

Publication number: US3007871A
Application number: US727055A
Authority: US
Inventors: Robert P Pardee; Joseph F Lyons
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1958-04-08
Filing date: 1958-04-08
Publication date: 1961-11-07
Anticipated expiration: 1978-11-07

Description

United States Patent Office 3,007,871 Patented Nov. 7, 1961 3,007,871 WATER-BASE LUBRICANT COMPOSITION Robert P. Pardee, Albuquerque, N. Mex., and Joseph F. Lyons, Poughkeepsie, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed Apr. 8, 1958, Ser. No. 727,055 10 Claims. (Cl. ESL-46.4)

This invention relates to an improved Water-base lubri- \cant composition. More particularly, the invention relates to an improved water-base cutting fluid.

Cutting fluids essentially function both as coolants and lubricants in machining of metals. As a coolant, the fluid acts to cool the cutting tool so as to reduce abrasive wear and loss of hardness, and to cool the Work to prevent distortion and dimensional inaccuracies. As a lubricant, the fluid acts to lubricate the chip-tool interface to reduce frictional heat, tool wear, and power consumption, and to improve surface finish. The fluid in its lubricating capacity also acts to prevent welding of metal to tool point and subsequent rough surfaces due to slough in-g-off of the built-up edge on the finished face of the work.

Cutting fluids also play secondary but nevertheless important roles in machining operations. The fluid should flush chips away from the work area; protect the finished work surfaces, the tools, and the machines against rust and discoloration; be smokeless and fogless in use; and either be odorless or have reasonably pleasant odor.

Generally, Water is one of the best coolants known and also performs the secondary roles of cutting fluids in an excellent manner. However water lacks essential lubricating characteristics necessary for a good cutting fluid. 'For example water lacks the film strength inherent in good mineral oils. This is essential to the cutting fluid in order to form and maintain a tough lubricant film to reduce friction between the tool and the work to protect the surface from being married by bits of abrasive materials which may be present.

In accordance with the present invention a composition which meets the requirements of a good cutting fluid and includes superior cooling and lubricating properties comprises a major portion of Water and a minor amount of the combination of a water soluble metal phosphate and a water soluble metal thiocyanate suflicient to improve the extreme pressure property of the composition. The amounts of each of these salts found effective in the combination ranges from 0.1 to about 5 percent by weight. The preferred combination is about 2.0 percent phosphate and 2.0 percent thiocyanate in a water base to obtain an excellent cutting fluid. The combination may vary in the amount and ratio of the constituents. For example 1.0 percent phosphate and 0.5 percent thiocyanate, or 0.5 percent phosphate and 3.0 percent thiocyanate.

The preferred metals used in the salts are the alkali metals including potassium, sodium and lithium. Other metals which form water soluble phosphate and thiocyanate salts are also very useful for the combniation of the invention. The alkaline earth metals are excellent metal components for the salts. The phosphate of copper, and the thiocyanates of copper; zinc, manganese and iron are examples of other Water soluble salts which are useful for the present invention. The metal portion of the phosphate and thiocyanate molecules can be the same or different in the combination of the invention however the metal is usually the same in each salt.

A rust inhibitor, such as a nitrite salt or an amine, is generally employed in the composition of the invention. Triethanolamine is preferred and in amounts ranging from 0.1 to l percen Other additives, such as water soluble extreme pressure agents, sequestering or settling agents, detergents, dyes an bactericides can be added to the composition without any deleterious effect.

This invention also includes an improvement in an orthogonal metal cutting process wherein a tool is directed against the metal to remove chips. The improvement comprises contacting the cutting edge of the tool and the work surface of the metal with water containing a minor amount of a water soluble metal thioeyanate suflicient to lend lubricity to the water. The minor amounts found useful range from about 0.5 to 5 percent by weight. The alkali metals are particularly good for the thiocyanate salt of the invention but alkaline earth metals, copper, Zinc, manganese and iron thiocyanates are also excellent in the process.

Other additives including rust-inhibitors such as nitrites or amines, are generally employed in the water-base composition of the process.

To demonstrate the excellence of the compositions of the invention with respect to extreme pressure property they were subjected to the well known Mean Hertz Load Test a description of which is set forth in US. Patent 2,600,058. Briefly, the test consists of rotating a steel ball under pressure against three locked steel balls.

' The test lubricant is applied to the balls and the amount of wear occurring at the rubbing points is a measure of the extreme pressure property of the lubricant tested. The more pressure which can be exerted without increasing the amount of wear, the better the extreme pressure property of the lubricant.

The following table shows the Hertz Load Test:

results of the Mean As a further means of determining the extreme pressure property or wear resistance of the compositions of the invention, they were subjected to the SAE Load Test (500 rpm.) the following table shows the results of this testing.

TABLE II SAE (500 Run Distilled Water Plus Additive rpm.)

Avg. Scale Load, lbs

N o additive 92 2% K PO4+0.5% triethanolarninc 82 2% KCNS+0.5% triethanolamine 206 4% K3PO4+0.5% trietl1anolamine 144 4% KCNS+0.5% triethanolamine 433 2% KONS+2% K PO4+0.5% trietha- 550+ nolamine.

In Tables I and II the unexpectedly high extreme pressure property of compositions of the invention is well demonstrated. This feature of supplying better lubrieating properties to water is not new but the excellence of compositions of the invention in this respect was not expected.

The water-base compositions containing just the chiccyanate although not as good as those containing the combination phosphate and thiocyanate nevertheless show unexpectedly good results in these extreme pressure bench tests as compared to the fluids containing just the phosphate.

The compositions are suitable for hydraulic systems or other systems as well as for cutting fluids where extreme pressure or anti-wear properties are desired. Such lubricant compositions are superior to mineral oil or oil emulsions since they are non-combustible and stable in storage.

As previously stated, the compositions of the invention are particularly suitable as cutting fluids owing to the excellent cooling property afforded by the presence of large amounts of water as well as the improved lubricating properties. The efliciency of cutting fluids is now well able to be determined by a test procedure disclosed in copending co-assigned application of Norwin C. Derby, S.N. 719,193 filed March 5, 1958. This test procedure briefly consists of measuring the electrical resistance of a metal chip produced from a cut of known length in a metal turning operation wherein a cutting fluid, the efficiency of which is to be measured, is employed. This resistance measurement is compared to the electrical resistance of a chip formed from a cut of a length equal to the cut from which the other chip was formed while utilizing a cutting fluid having a known efficiency. The higher the electrical resistance, the more efficient is the cutting fluid.

The specific test procedure is as follows:

Details of apparatus The lathe employed for this test was an American Pacemaker, a 16 inch by 30 inch tool room metal cutting lathe.

The test tool was a Rex AA high speed steel blank measuring /8 inch by 76 inch by 3 inches in length and supplied by Crucible Steel Co. The tool blank met the following specifications:

Tungsten "percent" 18.00 Chromium do 4.00 Vanadium do 1.10 Carbon do 0.73 Hardness, Rockwell C-63 The cutting head of the tool was of an inch in length. The side vertical face of the cutting head, forming one facet of the cutting edge, was a minimum of 5 of an inch in height and was ground at a 4 angle starting from the cutting edge. The top horizontal face of the cutting head, which formed the other facet of the cutting edge, was ground at an 8 angle starting from the cutting edge. The end vertical face of the cutting head was ground at a 4 angle starting from the top horizontal edge and at a 4 angle starting from the front vertical edge of the cutting head. This vertical edge was initially rounded to a radius of 0.010 of an inch. The three ground faces of the tool had a maximum surface roughness of two (2) microinchcs root-mean-square as measured with a Brush Surface Analyzer.

The metal stock or billet to be cut in the lathe was vanadium deoxidized steel, stock C-45, furnished by the Bethlehem Steel Co. The billet was 88 /2 inches in diameter as received but was reduced to 7 /2 inches for testing. The ladle analysis of the steel used for this billet was as follows:

Carbon percent 0.48 Manganese do 0.89 Phosphorous do 0.010 Sulfur do 0.027 Silicon do 0.25 Vanadium do 0.16 Tensile strength lbs./ sq. in.-- 87,000 Yield point lbs./sq. in 50,000 Brinell hardness 163-174 Details of procedure As previously indicated, the billet was slotted or scored longitudinally to a depth of about one-fourth the depth of the intended test cutting depth. A scoring tool made from the same type blank previously described and having a cutting head ground down to A3 inch in length, A inch in height and inch in width was used. The cutting edge was along the A inch width and the front face was ground at an 8 angle starting from the cutting edge.

This slotting tool was mounted in the tool post of the lathe with its center line in the same horizontal plane as the centerline of the billet but perpendicular thereto. The slotting tool was oriented with the cutting edge tangential to the cylindrical billet. With the billet locked, the cutting tool was traversed longitudinally along the billet using the hand travel crank of the lathe apron. A number of passes were made taking only a few thousandths of an inch on each pass until a depth of A of an inch was reached.

After slotting the billet, the slotting tool was removed and the test cutting tool was mounted in the tool post with the cutting edge of the tool at the center line of the billet perpendicular to and with the end of the tool 0.150 of an inch beyond the face of the billet at the starting end thereof. The lathe feed was adjusted to give a feed of 0.002 of an inch per revolution of the billet. Therefore, for each revolution a volume of metal 0.002 of an inch thick, 0.150 of an inch wide and equal in length to the circumference of the billet was removed.

The cutting speed of the lathe was set at 180 surface feet per minute and the cutting oil flow was at the rate of 4 gallons per minute.

With a freshly ground tool a ten second cut was made under the above conditions and the chips thrown away. Then, another ten second cut was made for the test. This cut was terminated by stopping the lathe leaving the chip attached to the billet. The chip was broken off and starting at that end the chip was examined until the first crack caused by the slot was found. The end portion was removed and the next ten segments designated by the cracks spaced along the chip were saved for resistance measurement.

The ten segments were separated into individual chips and then washed in Stoddard solvent and etched in oxalic acid to assure good electrical contact. Their electrical resistance was then measured on a standard Wheatstone Bridge Modified only by the addition of small clamps to contact and hold the end of the chips.

Two more ten second cuts as described above were made using the same tool. The same procedure, of four ten second cuts, was then followed for each of two other new cutting tools. This resulted in a total of ninety chips which were measured for electrical resistance. These ninety electrical resistance measurements were subsequently averaged to obtain the rating of the cutting oil for the run.

The results of this Chip Resistance Test on certain fluids including the composition of the invention is set forth in the following table.

TABLE III Chip Resist- Distilled Water Plus Additive ance (milliohms) No additive 65 4% Reference Fluid 1 76 2% K3PO4+0.5% triethan01amine 84 2% KCNS+0.5% triethanolamine 98 2% K3PO4+2% KCNS+0.5% triethanolatuin Ihe reference fluid consisted of 20% (wt) polyethylene glycol (M.W.=600), 9% (wt) sodium nitrite, 7% (wt) triethanolamine, and 25 ppm. brilliant blue dye.

We claim:

1. A lubricant composition comprising a major proportion of water, and the synergistic combination of from 0.1 to 5 percent by weight of a tri-alkali metal ortho phosphate and from 0.1 to 5 percent of an alkali metal thiocyanate, in sufiicient amounts to impart substantially improved extreme pressure properties to the said composit-ion.

2. A lubricant composition comprising a major proportion of water, the synergistic combination of from 0.1 to 5 percent by weight of a tri-alkali metal ortho phosphate and 0.1 to 5 percent of an alkali metal thiocyanate in sufiicient amounts to impart substantially improved extreme pressure properties to the said composition, and a rninor proportion of an alkylolarnine having rust inhibiting properties.

3. A lubricant composition comprising a major proportion of water, the synergistic combination of from 1 to 3 percent by weight of tri-potassium ortho phosphate and from 1 to 3 percent potassium thiocyanate, and from 0.1 to 1 percent by weight of thieth-anolamine.

4. In an orthogonal metal cutting process wherein a tool is directed against the metal to remove chips, the improvement which comprises contacting the cutting edge of the tool and the work surface of the metal during the cutting operation with water containing a minor amount of a water soluble metal thiocyanate sufficient to impart improved extreme pressure properties to the water.

5. In an orthogonal metal cutting process wherein a tool is directed against the metal to remove chips, the improvement which comprises contacting the cutting edge of the tool and the work surface of the metal during the cutting operation with water containing from about 0.5 to 5 percent by weight of an alkali metal thiocyanate, said thiocyanate being present in a sufiicient amount to impart extreme pressure properties to the water.

6. The orthogonal metal cutting process as described in claim 5 wherein a minor proportion of an alkylolamine having rust inhibiting properties is included in the water.

7. The orthogonal metal cutting process as described in claim 6 wherein the said alkylolamine is triethanolamine in the amount of 0.1 to 1 percent by weight.

8. In an orthogonal metal cutting process wherein a tool is directed against the metal to remove chips, the improvement which comprises contacting the cutting edge of the tool and the work surface of the metal during the cutting operation with water containing about 0.5-5 percent by weight of a water soluble tri-alkali metal ortho phosphate and about 0.5-5 percent by Weight of an alkali metal thiocyanate sufficient to impart improved extreme pressure properties to the water.

9. The orthogonal metal cutting process as described in claim 8 wherein the water contains a minor proportion of an alkylolarnine having rust inhibiting properties.

10. The orthogonal metal cutting process as described in claim 9 wherein the water contains the combination of from 1 to 3 percent by weight of tri-potassium ortho phosphate and from 1 to 3 percent potassium thiocyanate, and from 0.1 to 1 percent by weight of triethanolamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,008,939 Tufts July 23, 1935 2,198,965 Hochwalt Mar. 19, 1940 2,318,629 Prutton May 11, 1943 2,432,784 Miller Dec. 16, 1947 2,474,325 Rodgers June 28, 1949 2,825,693 Beaubien et a1 Mar. 4, 1958 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, 3 007 871 November 7 1961 Robert P. Pardee et a1,

It is hereby certified that error appears in the above numbered patent requiring correction and th at the said Letters Patent should read as corrected below.

Column 1 line 38 for "married" read marred V column 5 line 21 for "thiethanolamine" read triethanolamine Signed and sealed this 10th day of April 1962,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

Claims

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF WATER, AND THE SYNERGISTIC COMBINATION OF FROM 0.1 TO 5 PERCENT BY WEIGHT OF A TRI-ALKALI METAL ORTHO PHOSPHATE AND FROM 0.1 TO 5 PERCENT OF AN ALKALI METAL THIOCYANATE, IN SUFFICIENT AMOUNTS TO IMPART SUBSTANTIALLY IMPROVED EXTREME PRESSURE PROPERTIES TO THE SAID COMPOSITION.