US3505844A - Rolling lubrication - Google Patents

Description

April 14, 1970 J. o. MCLEAN 3,505,844

ROLLING LUBRICATION Filed Aug. 22, `1966 INVENTOR JOHN O. MCLEAN RNEYS United States Patent O 3,505,844 ROLLING LUBRICATION .lohn 0. McLean, Henrico County, Va., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed Aug. 22, 1966, Ser. No. 573,945 Int. Cl. B21b 45 /02; C10m 7/24, 7/ 20 U.S. Cl. 72-42 6 Claims ABSTRACT OF THE DISCLOSURE A lubricating system for cold rolling aluminum employs as a lubricant an aqueous dispersion of from about 0.1% to about 15% by weight of at least one polar compound such as a long chain fatty alcohol, a long chain fatty acid alkyl ester, or a long chain aliphatic carboxylic acid.

This invention relates to the deformation of aluminous metals, and to a novel lubricant therefor. More particularly, the invention concerns a method of cold rolling aluminum employing as a lubricating system therefor an aqueous dispersion of a polar lubricant.

Although for many years it has been common practice to employ mineral oil based lubricants for the rolling and drawing of both ferrous and nonferrous metals, the current trend is toward the introduction of waterbased lubricating systems wherever possible. Among the advantages possessed by water-based lubricants is the substantial cost saving by elimination of mineral oil. Other advantages include the fact that water is a much more efficient heat transfer medium, premitting higher mill speeds, and that a greater reduction of metal thickness per mill pass can be obtained than with an all oil system. Further, fire and toxicity hazards are eliminated.

For successful sheet rolling lubrication, the lubricant employed must be capable of supplying a uniform monolayer of a friction reducting material to the moving metal surfaces, and must, moreover, be capable of transporting metallic by-products for subsequent removal. The rolling process as a whole must produce bright, flat, nonstaining, clean metal at high volume with a minimum of scrap formation, and of roll changing.

It is known to use so-called soluble oils, incorporating a mineral oil base, in the form of aqueous dispersions or solutions, for hot rolling aluminum, but these preparations have the drawback of producing streaking on the metal surface, and of detaching aluminum oxide film, thereby interfering with the formation of an effective lubricant layer. It is also known to employ liquid fatty acid esters, such as butyl stearate, as lubricants for rolling aluminous metal, as disclosed, for example, in U.S. Patent No. 3,105,400. It is also known to employ such esters as additives to mineral oil dispersons, as disclosed in British Patent No. 988,073. Further, there is disclosed in U.S. Patent No. 3,195,332, the use of aqueous solutions or dispersions of polyoxyethyleneimidazolines in which the polyoxyethylene moiety contains from 4 to 2O oxyethylene groups per mole of imidazoline, and the imidazoline moiety is substituted at the 2-position by an alkyl or alkenyl group containing from 1l to 20 carbon atoms, for the hot rolling of aluminum.

In accordance with the present invention, it has been found that an effective lubricant for the rolling of aluminous metals is provided by forming an aqueous dispersion of a water-insoluble polar lubricant and applying said dispersion to the surface of the metal during rolling.

The term aluminous metal as employed herein refers to aluminum metal, and to aluminum base alloys.

The term polar lubrican means a compound which possesses the ability to adsorb on a metal surface as an oriented monolayer. Polar lubricants include polar subice stances in a number of broad categories of long chain organic compounds, such as carboxylic acids, alcohols, esters, amines, amides, ketones, and certain hydrocarbon polymers.

Physical adsorption and intermolecular adhesion are the basic mechanisms in the wetting and friction-reducing properties of monolayers of polar compounds adsorbed on metals, and this is reflected in the fact that the relative adsorptivities of the foregoing types of compounds on metals increase in the order: esters, alcohols, carboxylic acids, primary amine and amides. Both oil and polar compound molecules are capable of forming adsorbed films before adsorption equilibrium is attained, but these are metastable lms which form only when the molecules of solvent and compound are able to adlineate completely. At adsorption equilibrium, no solvent molecules are included in the monolayer formed, but attainment of equilibrium may require several hours. Because boundary lubricant films between rapidly moving metal surfaces will usually be mixed films, it appears that the mineral oil used in conventional rolling lubricant compositions can adversely affect the load-carrying qualities of the lubricant.

In accordance with the present invention, the use of mineral oil components of rolling systems is eliminated, and there is employed instead, a lubricant consisting essentially of a polar lubricant compound as the dispersed phase in an aqueous medium. The polar compounds th-us utilized contain one or more polar groups which are not sterically hindered from adsorbing on metal surfaces or reacting with them, e.g. such as by salt formation of organic acids.

The lubricant compositions of the invention comprise aqueous dispersions of polar lubricants in which the proportion of polar compound ranges from about 0.1% to about 15 by weight.

The polar compound may be dispersed with the aid of any dispcrsing agent conventionally employed for this purpose, including triethanolamine stearate, alkali metal petroleum sulfonates, condensation products of higher alkyl phenols with ethylene oxide, and the like.

Preferably, the dispersion of the polar compound is formed by mechanical means, employing for this purpose a disperser of the ultrasonic type, which may be advantageously placed in the lubricant circulating system.

Examples of suitable polar lubricants which may be employed in accordance with the invention include oleic acid, lauryl alcohol, palmityl (cetyl) alcohol, methyl stearate, butyl stearate, stearylamine, stearic acid amide, and the like, and mixtures thereof.

The practice of the invention will be illustrated with respect to the rolling of aluminum, but it is to be understood that the lubricants of the invention are equally suitable for metal drawing and similar operations.

For a better understanding of the invention and of its other details, objects, and advantages, reference is now made to the accompanying drawings, which show, for purposes of illustration only, a present preferred embodiment of the invention. The sole figure of the drawing is a diagrammatic elevation view of the apparatus according to the invention.

In that figure, opposed steel rolls 2 of a rolling mill act upon metal workpiece 4 to elongate it and reduce its thickness. Rolls 2 are provided with a continuous lubrication system in which a plurality of rows of nozzles 6 are mounted to spray lubricant into the area of contact between rolls 2 and workpiece 4. Pit or trough 8, which is mounted below rolls 2 for collecting lubricant falling from rolls 2, drains into lubricant receiving and storage tank 10. Suction pipe `12, which terminates near the bottom of tank 10, communicates through piping 14 with the intake of centrifugal pump 16. Pump 16 is connected at its discharge side to pipe 18, which leads into junction 20, where the lubricant circulating system branches into two parallel legs, a dispersion leg 28 and a dispersion bypass leg 22. Bypass leg 22 includes piping 24 and flow regulating valve 26. Dispersion Ileg 28 consists of piping 30 in which is disposed, going downstream, ow regulating valve 32, junction 34, gear pump 36, ultrasonic disperser 38, and valve 39. Polar lubricant supply tank 40 communicates with junction 34 through piping 42 in which is disposed, going downstream, valve 44 and pump 46. Dispersion leg 28 and bypass leg 22 rejoin at junction 50 with common piping 52 leading to junction 54. From junction 54, roll bypass leg 56 including valve 58 and piping 60 connects directly to the top of tank 10. Also connected to junction 54 is piping 62 including valve 64. Piping 62 leads into junction 66, where the circulating system branches into supply pipes 68 and 70, in which nozzles 6 are located. A makeup line 80 including valve 82 connects into a side Wall of tank 10.

A suitable type of ultrasonic dispersing device is, for example, the device available commerically under the designation Sonolator (Sonic Eengineering Corp., Norwalk, Conn.). In these types of devices, a high velocity uid stream passes over a metal reed that is then forced into vibration at ultrasonic frequencies. The mechanical agitation and cavitation disperses the Water-immiscible fluid into suspended particles substantially all of which are less than about microns in diameter, and forms a homogenized, relatively stable dispersion.

In the operation of the lubricating system in accordance with the invention, valve 82 is opened and ordinary city water introduced via makeup line 80 into tank 10. With valves 32, 39 and 58 open and valves 26, 44, 64 and 82 closed, pumps 16 and 36 are started, thereby circulating the water from tank through piping 18, dispersion leg 28, piping 52 and roll bypass leg 56, back to tank 10. Next, valve 44 is opened and pump 46 operated to inject polar lubricant contained within tank 40 into dispersion leg 28 at junction 34. Gear pump 36 forces the mixture of water and polar lubricant into ultrasonic disperser 38, which forms a mechanical dispersion of the polar lubricant in the water. When the desired concentration in the range of about 0.1% to about by Weight of polar lubricant is reached, valve 44 is closed and pump 46 stopped.

The poplar lubricant and water are continued to be circulated through the path 10, 18, 28, 52, 56, 10 as described above, until substantially all of the polar lubricant is mechanically dispersed in the water. Then valve 64 is opened, valve 58 closed, and workpiece 4 introduced to the bight of rolls 2. The mechanical dispersion is sprayed from nozzles 6 into the area of contact of rolls 2 and workpiece 4, and, at the interface between the two, performs its lubricating and cooling functions previously described. (Of course, if desired, the dispersion could be applied at the interface by being sprayed or otherwise applied to either the workpiece or the rolls alone.)

It has been found that mechanical dispersions formed and employed in the manner just described will continue to be satisfactory dispersions for rolling lubrication for a number of hours or even days. Therefore, various economies are achieved by adjusting valves 26, 32 and 39 to pass only a portion of the dispersion flowing through piping 18 through dispersion leg 28, with the remainder passing through bypass leg 22. In this manner the rate at which the polar lubricant settles out or is otherwise removed from the circulating polar lubricant-Water dispersion can be balanced by the rate at which ultrasonic disperser 38 produces fresh dispersion, thereby achieving a steady state condition. Alternatively, valves 32 and 39 can be closed completely and pump 36 and ultrasonic disperser 38 shut down for limited intervals, and reopened and restarted when the degree of dispersion reaches a minimum tolerable level.

Fresh water and polar lubricant may be added via makeup line and polar lubricant supply system 40, 42, 44, 46, respectively, to replace that lost by evaporation and pickup by workpiece 4.

Although the lubricant dispersion may be maintained at ambient temperature, it is preferable to operate with the lubricant at a temperature between about and F.

A reduction per pass of up to 65% and more may be employed.

The following examples illustrate the practice of the invention, but are not to be regared as limiting:

EXAMPLE 1 A laboratory size rolling mill having 8-inch long rolls, 5 inches in diameter, the rolls being flat ground and polished to a bright finish, was equipped with a temperature controlled lubricant reservoir, spray nozzles directed at both top and bottom rolls, and a circulating system with sonic disperser. The rolls were set for 53% reduction and bright surface with a single pass of aluminum alloy 5086H-38 strip, 1% inches wide and 0.019 inch thick. Comparative rolling tests were made with commercial soluble mineral oil lubricant (Acra-2, Far Best Corp.) at room temperature, and with water based lubricant systems at 110 F. The polar lubricants were dispersed as follows: (l) 1% butyl stearate; (2) a blend of 0.5% lauryl alcohol and 1% butyl stearate; and (3) 1% technical methyl stearate (Chemol 44, Chemol, Inc., Greensboro, N.C.).

The following table summarizes the results obtained:

Roll force, Percent Final gauge Lubricant. No. lbs/in. reduction (mils) Rating 590 39. 5 9. 5 Good. 539 57.9 8. 0 Very good. 3 539 55. 3 8. 5 Good. Aura-2 (,5%) 348 60.6 7. 5 Do.

EXAMPLE 2 Employing a 58-inch rolling mill, and a system similar to that shown in the drawing, a coil of alloy 5086-13, 22 inch Width and 0.030 inch thickness, was reduced to 0.011 inch (63.3%) at 450 f.p.m. speed and full mill power. The Water-based lubricant used Was an ultrasonically homogenized aqueous dispersion of 0.8% technical methyl stearate (Chemol-44) and 0.01% di-linoleic acid (Dimer acid, Empol 1014). The rolling performance exceeded mineral oil based cold rolling oil at comparable speed and reduction, and the surface and shape obtained were both good.

EXAMPLE 3 Employing a 5 S-inch rolling mill, and a system similar to that shown in the drawing, a coil of scrap alloy 3003-F, 36 inches Wide and 0.035 inch thickness, was reduced to 0.018 inch (48.6% reduction) at 1600 f.p.m. mill speed and full mill power. The lubricant used was an ultrasonically homogenized aqueous dispersion of gallons of technical methyl stearate (Chemol-44) and 25 gallons of di-linoleic acid (Dimer acid, Empol 1014) dispersed over a period of 8 hours into 2,000 gallons of city water at 75-100 F.

The coil was re-rolled at a top speed of about 2000 fpm. at slightly less than full mill power obtaining a further reduction from 0.018 inch to 0.0085 inch (52.8%). The rolled metal shape and surface were rated good.

What is claimed is:

1. Method of cold rolling an aluminous metal workpiece by contact with a harder metal surface comprising the step of applying to the interface between said workpiece and said harder metal a dispersion in Iwater of about 0.01% to about 15% by Weight of at least one polar lubricant selected from the group consisting of a long chain fatty alcohol, a long chain fatty carboxylic acid, a long chain fatty acid ester of a monoalkanol having 1 4 carbon atoms, a long chain fatty mono amine and a long chain fatty acid amide, while deforming said workpiece.

2. The method of claim 1 in which the dispersion is maintained at a temperature of about 110 to 115 F.

3. The method of claim 1 in which the polar lubricant is a blend of methyl stearate Iand di-linoleic acid.

4. The method of claim 1 in which the polar lubricant is a iblend of lauryl alcohol and butyl stearate.

5. The method of claim 1 in which the polar lubricant is methyl stearate.

6. The Imethod of claim 1 in which the polar lubricant is butyl stearate.

References Cited UNITED STATES PATENTS 2,962,401 1l/l960 Guminski 252-52 3/1962 Gaynor et a1. 252-18 6 Parker 252-495 Katzer 252-493 Hurtt 72-42 Goppelt 72-42 Daly et al. 252-495 Klein et al. 252-495 Ranauto 72-42 rFletcher et al 72-42 Zvanut 72-42 Davis 252-495 U.S. Cl. X.R.

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