AQUEOUS SOLUTION LUBRICANT FOR ALUMINUM COLD ROLLING

Abstract

Compositions related to a water-based lubricant fluid for aluminum cold rolling which is free from measurable particles or oil droplets which can be applied in field production. A single-phase lubricant fluid may include water-soluble polymers, lubricating additives, anti-rust additives, anti-oxidant additives, pH-adjust additives, or combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit from U.S. Provisional Patent Application No. 61/580,799, filed on Dec. 28, 2011, which is incorporated by reference in its entirety.

BACKGROUND

Aluminum cold rolling is one of the most important processes of aluminum application. The lubricant is critical for continuous production and good quality. Traditionally, there have been two primary types of lubricating methods for the cold rolling processes: 1) lubrication with neat oils and 2) lubrication with oil-in-water emulsions. The first generation lubricant is neat oil. Neat oil products provide good sheet surface quality but also have critical defects: 1) easily combustible; and 2) higher rates of consumption. The second generation product is oil-in-water emulsion products. Compared with neat oil, emulsions avoid the issues presented by the use of neat oil products. Potential shortcomings of the emulsions include: 1) limited strip cleanliness after anneal as a result of too high evaporation temperature; and 2) ease in emulsification of tramp oil, which decreases rolling performance.

U.S. Pat. No. 4,828,737 discloses the use of aqueous products in aluminum cold rolling. However, according to that patent, these aqueous products require a temperature of 360° C. before they evaporate. The aqueous solution lubricants of embodiments of the present invention may be completely evaporated at 240° C., thereby allowing all process conditions that are applied when (partially) annealing aluminum alloys.

The aqueous solution lubricant for aluminum cold rolling of some embodiments of the present invention has addressed the shortcomings of traditional lubrication.

SUMMARY OF THE INVENTION

According to some embodiments, a lubricant fluid for aluminum cold rolling includes a single-phase water-based solution with a water soluble polymer. In some embodiments, the polymer includes at least one hydrophilic group, such as ethylene oxide. In some embodiments, the polymer's molecular weight is about 200 or greater. In certain embodiments, the lubricant fluid includes about 5 wt % to about 99 wt % water soluble polymer. In some embodiments, the lubricant fluid includes at least one lubricant additive, which may be water soluble. In some embodiments, the lubricant additive includes one or more carbon chain structures, one or more hydrophilic groups, or a combination thereof. A lubricant fluid may include about 0.1 wt % to about 10.0 wt % lubricant additive. In certain embodiments, the lubricant fluid includes at least one functional additive, such as anti-rust additives, anti-oxidant additives, pH-adjust additives, or combinations thereof. The lubricant fluid may include about 0.05 wt % to about 5 wt % functional additive.

DESCRIPTION OF THE FIGURES

FIG. 1 shows evaporation of lubricant fluids at different temperatures.

FIG. 2 shows a rolled strip with a reference formulation.

FIG. 3 shows a rolled strip with a formulation of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Compositions and methods of some embodiments of the present invention relate to aluminum cold rolling processes with single-phase water-based lubricant fluids. Compositions and methods of the present invention may include a water-based lubricant fluid for aluminum cold rolling which is free or substantially free from measurable particles or oil droplets. In some embodiments, a lubricant fluid includes one or more water-soluble polymers. A lubricant fluid may also include one or more of lubricant additives, and various functional additives.

Traditionally, oil-in-water emulsions are applied to the strip during aluminum cold rolling. However, use of oil-in-water emulsions may have disadvantages, such as limited strip cleanliness after anneal, insufficient filterability, fluctuating emulsion characteristics leading to inconsistency on the mill, high oil consumption, etc. In some embodiments, such disadvantages may be avoided by use of a single-phased water-based lubricant fluid according to some embodiments of the present invention. Single-phased water-based lubricant fluids according to some embodiments of the present invention may be useful for application in cold rolling of any type of aluminum and alloy.

According to the traditional lubrication theory of cold rolling and industry experience, two regimes of lubrication exist in the rolling process: boundary lubrication and elastic-hydrodynamic lubrication (“EHD”). Many aluminum rolling processes may be conducted in the mixed lubrication regime, including characteristics of both boundary lubrication and EHD lubrication. Therefore, in some embodiments, lubricant fluids of the present invention may provide lubrication-boundary lubrication and/or elastic-hydrodynamic lubrication. Due to aluminum deformation stress, lubrication is inclined to boundary lubrication. In some embodiments, lubricant fluids of the present invention may provide the following characteristics: 1) provide good surface quality with no obvious water-stain impression; 2) show no residue on aluminum sheet after annealing, where all materials should be eliminated before 240° C.; and 3) reject tramp oil, which should be easily separated from the solution.

Therefore, in some embodiments of the present invention, single-phased water-based lubricant fluids may provide sufficient lubrication properties in boundary lubrication for use in cold rolling processes.

Lubricant Fluid Composition

In some embodiments, a lubricant fluid of the present invention includes a single-phase water based lubricant fluid. In some embodiments, a single-phase water based lubricant fluid may include a water soluble polymer and optionally one or more lubricant additives, and various functional additives.

Water Soluble Polymer

A lubricant fluid of the present invention may include one or more water soluble polymers. In some embodiments, the polymers may be dissolved or dispersed in a volume of water.

In some embodiments, a suitable water soluble polymer includes one or more hydrophilic groups. Examples of suitable hydrophilic groups include but are not limited to ethylene oxide, propylene oxide, hydroxyl, carboxyl, acyl-amine and combinations thereof. In some embodiments, the evaporation temperature of these polymers is such that the final product is completely evaporated at temperatures less than 240° C.

In some embodiments, a lubricant fluid includes one or more water soluble polymers in an amount of about 5 wt % to about 99 wt %; 10 wt % to about 95 wt %; about 15 wt % to about 90 wt %; about 20 wt % to about 85 wt %; about 25 wt % to about 80 wt %; about 30 wt % to about 75 wt %; about 35 wt % to about 70 wt %; about 40 wt % to about 65 wt %; about 45 wt % to about 60 wt %; about 50 wt % to about 55 wt %; about 5 wt %; about 10 wt %; about 15 wt %; about 20 wt %; about 25 wt %; about 30 wt %; about 35 wt %; about 40 wt %; about 45 wt %; about 50 wt %; about 55 wt %; about 60 wt %; about 65 wt %; about 70 wt %; about 75 wt %; about 80 wt %; about 85 wt %; about 90 wt %; about 95 wt %; or about 99%.

Lubricant Additives

A lubricant fluid of the present invention may optionally include one or more lubricant additives. Any suitable lubricant additive may be used in the lubricant fluids of the present invention. In some embodiments, a suitable lubricant additive includes one or more types of carbon chain structures. Examples of suitable lubricant additives may include but are not limited to water soluble C₆-C₁₈ phosphoric ester, phosphorous ester, phosphate ester, and organic acid.

In some embodiments, a suitable lubricant additive includes one or more hydrophilic groups. Examples of suitable hydrophilic groups include but are not limited to ethylene oxide, propylene oxide, hydroxyl groups, carboxyl groups, and acyl amine groups.

In some embodiments, a lubricant fluid includes one or more lubricant additives in an amount of about 0.05 wt % to about 10 wt % of the lubricant fluid; about 0.1 wt % to about 8 wt % of the lubricant fluid; about 0.1 wt % to about 6 wt % of the lubricant fluid; about 0.1 wt % to about 4 wt % of the lubricant fluid; about 0.1 wt % to about 2 wt % of the lubricant fluid; about 0.05 wt % of the lubricant fluid; about 0.1 wt % of the lubricant fluid; about 0.5 wt % of the lubricant fluid; about 1 wt % of the lubricant fluid; about 2 wt % of the lubricant fluid; about 3 wt % of the lubricant fluid; about 4 wt % of the lubricant fluid; about 5 wt % of the lubricant fluid; about 6 wt % of the lubricant fluid; about 7 wt % of the lubricant fluid; about 8 wt % of the lubricant fluid; about 9 wt % of the lubricant fluid; or about 10 wt % of the lubricant fluid.

Functional Additives

A lubricant fluid of the present invention may include one or more functional additives. Any suitable functional additive may be included in the lubricant fluids of some embodiments of the present invention. In some embodiments, such functional additives may be chosen in order to cover boundary lubrication and other process requirements of aluminum cold rolling. Examples of suitable additives include but are not limited to anti-rust additives, anti-oxidant additives, pH-adjusting additives, and the like. Any suitable functional additive may be included to achieve the desired result. Examples of a suitable corrosion inhibitor additive include but are not limited to derivatives of triazole, tolutriazole, organic and inorganic phosphorous compounds, and organic and inorganic phosphate compounds. An example of a suitable antioxidant additive includes but is not limited to alkylated amino phenol. An example of a suitable pH-adjusting additive includes but is not limited to ammonia, alkane amines, and alkanol amines like trolamine.

In some embodiments, a lubricant fluid includes one or more functional additives in an amount of about 0.01 wt % to about 10 wt % of the lubricant fluid; about 0.05 wt % to about 9 wt % of the lubricant fluid; about 0.05 wt % to about 8 wt % of the lubricant fluid; about 0.05 wt % to about 7 wt % of the lubricant fluid; about 0.05 wt % to about 6 wt % of the lubricant fluid; about 0.05 wt % to about 5 wt % of the lubricant fluid; about 0.1 wt % to about 4 wt % of the lubricant fluid; about 0.5 wt % to about 3 wt % of the lubricant fluid; about 1 wt % to about 2 wt % of the lubricant fluid; about 0.01 wt % of the lubricant fluid; about 0.05 wt % of the lubricant fluid; about 0.1 wt % of the lubricant fluid; about 0.5 wt % of the lubricant fluid; about 1 wt % of the lubricant fluid; about 2 wt % of the lubricant fluid; about 3 wt % of the lubricant fluid; about 4 wt % of the lubricant fluid; about 5 wt % of the lubricant fluid; about 6 wt % of the lubricant fluid; about 7 wt % of the lubricant fluid; about 8 wt % of the lubricant fluid; about 9 wt % of the lubricant fluid; or about 10 wt % of the lubricant fluid. In some embodiments, the lubricant fluid has a pH of about 4.0 to about 9.0; about 5.0 to about 8.0; about 6.0 to about 7.0; about 4.0; about 5.0; about 6.0; about 7.0; about 8.0 or about 9.0. In some embodiments, a lubricant fluid includes a pH-adjusting additive in an amount such that the lubricant fluid has a pH of about 4.0 to about 9.0 at 25° C.

In some embodiments, lubricating fluids of the present invention show, in a typical boundary test on different types of aluminum strips, friction coefficients of about 0.05 to about 0.15; about 0.06 to about 0.14; about 0.07 to about 0.13; about 0.08 to about 0.12; about 0.09 to about 0.11; about 0.05; about 0.06; about 0.07; about 0.08; about 0.09; about 0.10; about 0.11; about 0.12; about 0.13; about 0.14; or about 0.15.

In some embodiments, lubricant fluids also include water, such as demineralized water.

The following examples are provided merely for the purpose of describing some lubricant compositions representative of the present invention in greater detail and are in no way to be considered as setting a limitation on the scope of the invention.

EXAMPLES

Single-phase water-based lubricant fluids were evaluated using an array of experiments which are considered in the industry to be highly predictive of the performance of a lubricant package when applied in an aluminum cold rolling process, including:

• • a) intrinsic lubrication properties evaluated with boundary lubrication tests;
  • b) thermal stability and evaporation properties with thermo gravimetric analysis TGA) equipment;
  • c) anti-staining properties with stack staining and energy dispersive spectrum analysis (EDS) tests; and
  • d) rolling performance characteristics tested with a 2-high single reversing rolling test mill with a test procedure correlating to the various production mill processes.
  • Two typical formulations were prepared for use in the examples:

Formulation 1:

EO-PO polymer: 10.0 wt %
Phosphoric ester: 1.0 wt %

Trolamine: 0.5 wt %

Demineralized water. 88.5 wt %

Formulation 2:

PEG 200: 90.0 wt %

Phosphoric ester: 1.0 wt %

Tolutriazole: 5.0 wt %

Trolamine: 1.5 wt %

Demineralized water: 3.5 wt %

An oil soluble conventional emulsion lubricant package, widely used in multiple production high speed reversing mills with good performance results is a product based on kerosene. This product was used as reference product.

Example 1

Boundary Lubrication

The intrinsic lubrication properties of the lubricant packages were evaluated in a boundary tester. The applied test procedures are commonly used for evaluating lubrication properties of lubricants for use in aluminum cold rolling.

Boundary tester
T = 60 C.	Reference	Formulation 1	Formulation 2
SWA 1050* CoF**	0.127	0.106	0.098
SWA 3104 CoF	0.081	0.080	0.048
SWA 5052 CoF	0.110	0.097	0.051
*SWA 1050/3104/5052: Different aluminum alloys
**CoF: coefficient of friction

The reference (usually used in production mills) has coefficients of friction of about 0.08-0.13 on different types of aluminum strips. As shown in the table above, Formulation 1 demonstrated CoF's successfully within this standard range, while Formulation 2 gave lower COF's.

Example 2

Anti Staining Properties

Anti staining properties are key parameters for strip cleanliness after rolling and annealing. The anti staining properties of the lubricant fluids were evaluated with stack staining tests. This is a key parameter which evaluates strip cleanliness after rolling and annealing. To test the lubricant fluids, the fluid was applied between the surfaces of two aluminum panels and wrapped tightly with adhesive tapes. The wrapped panels were then placed in an oven at about 90° C. while pressing with a load of about 4.5 kg. After 24 hours, the wrapped panels were removed and the surfaces observed. Energy dispersive spectrum analysis (EDS) was applied to measure amount of different elements on the stained surface. Oxygen was used as subject matter to evaluate the degree of water-staining.

	O content %	Al content %
	Reference	14.30	85.70
	Formulation 1	10.05	89.95
	Formulation 2	16.52	83.48

The resulting oxygen contents illustrate that the two single-phase water-based lubricant fluids (Formulations 1-2) exhibit comparable anti staining properties as the traditional products (Reference).

Example 3

TGA

For mills without cleaning line, the evaporation properties of the water solution lubricant packages are important. In order to be able to roll all aluminum alloys, all materials on the aluminum surface must be removed below 240° C. Thus, in terms of a TGA curve, products should be volatilized before this temperature is reached. Thermal stability and evaporation properties of the water solution lubricant packages were evaluated by thermo gravimetric analysis (“TGA”), to demonstrate the cleanliness of the strip surface after annealing.

The above test results are obtained in air condition. Such testing may also be conducted in an oxygen environment.

It can be seen from the results shown in FIG. 1 that the single-phase water-based lubricant fluids of Formulations 1-2 evaporate at a higher temperature than the reference. However, they are completely evaporated below 240° C. Based on this property, also a clean sheet surface can be expected after (batch) anneal when using a single-phase water-based lubricant fluid.

Example 4

Tramp Oil Rejection Property

Tramp oil rejection properties of the lubricant fluids were evaluated with anti-tramp oil tests. This is a key parameter which evaluates the sensitivity of the lubricant for pollution. To test the lubricant fluids, 1% tramp oil was mixed in reference and Formulation 1 and 2. The mixtures were then placed in an oven at about 60° C. After 1 hour the amount of tramp oil floating on top of the product was determined

	Reference	Formulation 1	Formulation 2
1 hour	0%	80%	79%
Rejection percent

It can be seen from the results shown in table above that the single-phase water-based lubricant fluids of Formulations 1-2 exhibit superior tramp oil rejection compared to Reference, because in each of Formulations 1 and 2 about 80% tramp oil has been rejected.

Example 5

Pilot Mill Test

Rolling performances of the water solution lubricant packages were evaluated by a 2-high single stand reversing rolling test mill from Southwest Aluminum Factory. The spraying system is a PE pipe which has several holes on it (range interval 10 cm, bore diameter <2 mm) hung above the roller (parallel). The liquid flew from a 10 L barrel which was positioned higher than the pipe, then went though the pipe and dropped on to the aluminum strip near the entrance side. There was no blown-off at the exit side.

The original thickness of the aluminum strips was 0.57 mm. The strip thickness after rolling one pass with the same force is indicated in the table.

	Thickness after 1 pass	Reduction %
	Reference	0.408	28
	Formulation 1	0.405	29
	Formulation 2	0.405	29

The results above demonstrate that aluminum can be rolled with Formulation 1 and 2 and that the exit thicknesses are comparable with those obtained with the reference. Moreover the surface of the aluminum strip rolled with the solutions shows a homogeneous metal color which is comparable with the surface rolled with the reference. The results demonstrate that the surface quality is good.

Example 6

Production Mill Test

Rolling performances of the water solution lubricant packages were evaluated on a 4-high single stand reversing rolling production mill. The mill width is 1400 mm and work roll's diameter is 300 mm. The maximum rolling speed is about 4.0 m/s, the maximum rolling force is 1000 ton.

Rolling results are below:

Reference:

	Entry	Exit				Roll
	Thickness	Thickness	Reduction	Width	Speed	Force
	mm	mm	%	mm	m/s	(Ton)
Pass 1	4.50	3.10	31%	1000	2.0	450
Pass 2	3.10	2.20	29%	1000	4.0	500
Pass 3	2.20	1.55	30%	1000	2.0	500

Formulation 1:

	Entry	Exit				Roll
	Thickness	Thickness	Reduction	Width	Speed	Force
	mm	mm	%	mm	m/s	(Ton)
Pass 1	4.50	3.10	31%	1000	2.4	460
Pass 2	3.10	2.20	29%	1000	4.0	490
Pass 3	2.20	1.55	30%	1000	3.3	480

These results show that aluminum can be rolled under the same conditions with Formulation 1 as with the reference.

The strip's quality is comparable as rolled with the reference product. No obvious defect on the surface.

Neither Formulation 2 nor an aqueous dilution of it was tested in this mill. Based on the experiments before, it is expected that the rolling performance will be comparable with Formulation 1.

Claims

1. A lubricant fluid for aluminum cold rolling comprising a single-phase water-based solution, wherein the solution comprises a water soluble polymer.

2. The lubricant fluid of claim 1, wherein the polymer comprises at least one hydrophilic group.

3. The lubricant fluid of claim 2, wherein at least one hydrophilic group comprises ethylene oxide.

4. The lubricant fluid of claim 1, wherein the polymer evaporates at or below 240° C.

5. The lubricant fluid of claim 1, comprising about 10 wt % to about 99 wt % water soluble polymer.

6. The lubricant fluid of claim 1, wherein the solution further comprises at least one lubricant additive.

7. The lubricant fluid of claim 6, wherein at least one lubricant additive is water soluble.

8. The lubricant fluid of claim 6, wherein at least one lubricant additive comprises organic acids or organic phosphoric ester having a carbon chain of C6-C18.

9. The lubricant fluid of claim 6, comprising about 0.1 wt % to about 10.0 wt % lubricant additive.

10. The lubricant fluid of claim 1, wherein the solution further comprises at least one functional additive.

11. The lubricant fluid of claim 1, wherein at least one functional additive comprises anti-rust additives, anti-oxidant additives, pH-adjusting additives, or combinations thereof.

12. The lubricant fluid of claim 11, wherein the anti-rust additive comprises inorganic or organic phosphorus compounds or derivatives of triazole.

13. The lubricant fluid of claim 11, wherein the pH-adjusting additive comprises ammonia, alkane amines or alkanol amines.

14. The lubricant fluid of claim 11, wherein the lubricant fluid includes the pH-adjusting additive in an amount such that the lubricant fluid has a pH value of about 4.0 to about 9.0 at 25° C.

15. The lubricant fluid of claim 11, comprising about 0.05 wt % to about 5.0 wt % functional additive.

16. A method of cold-rolling aluminum, comprising application the lubricant fluid of claim 1 to an aluminum strip.