Patent Application
20060281646
The present invention relates to additives for lubricants for use in working metal and, more particularly, to additives for cold rolling oils.
A thin plate of metal is conventionally produced by means of a hot or cold rolling operation. Cold rolling is a process by which the sheet metal or strip metal stock is fed between rollers and then compressed and squeezed at a temperature below the softening point of the metal in order to create strain hardening. The amount of strain introduced during the process determines the hardness and other mechanical properties of the final metal product. Cold rolling changes the mechanical properties of the metal sheet or strip and produces certain combinations of hardness, strength, ductility, stiffness, and other properties which are commonly referred to as tempers. The primary advantages of cold rolling are a relatively uniform metal thickness and a good surface finish.
When metal is subjected to cold rolling, lubricants are used to decrease friction between the metal and the rolls of the rolling mill. These lubricants also promote the creation of a good surface finish on the metal. During the operation of a rolling mill, the lubricant is conventionally sprayed onto or allowed to flow onto the metal just upstream from each set of rolls and/or onto the rolls themselves. The introduction of lubricants into the cold rolling process allows higher rolling speeds and reductions (changes in the thickness of the metal plate), a reduction of roll wear, and consistent mill performance. In order to lubricate the contact between the roll and the metal strip, known as the roll bite, the lubricant forms a protective film on the metal sheet and/or the roll to reduce friction. As a result, when lubricants are used the wear on the rolls is reduced and smooth rolled metal is produced.
Conventionally, various lubricants have been employed in the cold rolling process. The particular lubricating oil used is determined by the manner of the rolling operation and the type of metal to be rolled. Generally, there are two important considerations for cold rolling lubricants: (1) the lubricant should form an adequate film in the roll bite; and (2) the intrinsic properties of the lubricant should allow the lubricant to reduce friction and roll wear. In order to function well as a lubricant, the lubricant used in the rolling mill must be capable of forming a relatively uniform layer of friction-reducing material on the surface of the rolls and the metal. Additionally, given the advent of modern high-speed rolling mills, the lubricant must be effective at the high process speeds and loads of such mills.
The lubricants used in cold rolling may also serve as coolants in order to remove the heat generated in the rolls and the metal during rolling. The rolling process causes the temperature of the metal to increase so much that the metal and the rolls must be continuously cooled with some type of coolant. Conventionally, the lubricant plays the dual role of a lubricant and a coolant and, thus, the cooling properties of the lubricant are often important. Additionally, the lubricant's ability to be mixed with water may also be important, as water is an effective, cheap, and widely available coolant.
Cold rolling lubricants often contain additives of various kinds to increase the lubricating ability of the base lubricant. Generally, these additives are compounds such as fatty alcohols and fatty esters. The effect of these additives is to improve the lubricating ability of the base lubricant, thereby further decreasing the friction between the rolls and the metal. This decrease in friction allows a greater and more efficient reduction in the thickness of the metal being rolled per pass through the rolling mill. The additives also generally serve to decrease the tendency of particles of metal to be picked up by the surface of the rolls during rolling.
Due to industry practices, as well as for economic reasons, the rolling lubricant is usually allowed to remain on the surface of the metal after cold rolling and as the metal moves on to later processes, such as annealing or heat treatment. Although the lubricant may be completely removed using special cleaning or degreasing processes after cold rolling, these processes cause excessive production costs. As a result, lubricants generally also contain additives which minimize the staining of the surface of the metal during annealing cycles or in storage, particularly if the base lubricant exhibits such staining characteristics when used alone. Such additives are used to prevent the discoloration of the metal during later processes, increasing the luster and value of the final metal product. One important characteristic of such additives is their boiling point, as it has been found that, in general, additives with lower boiling points generally are less likely to remain as a film on the surface of the metal and cause staining.
Finally, if residual films of lubricant remain on the metal surface, which generally is the case, the lubricants should be non-toxic to mill workers during use and non-toxic to future users of the metal, particularly if the metal is to be used in the food industry.
The present invention was developed in connection with the cold rolling of aluminum and aluminum alloys and reference to such a use will be made from time to time herein in describing the invention. It should be understood, however, that the present invention is not limited to such a system, but rather is also applicable to systems for use in other metalworking operations and for other metals where lubrication is an important issue.
In accordance with the present invention there is provided an additive for cold rolling lubricants which improves the lubricity, as well as the cooling properties, of the lubricant. As a result, the additive of the present invention allows for increased production and the production of metal with improved brightness and cleanliness and with a uniform appearance.
In accordance with the present invention, a polar liquid with a boiling point between 25° C. and 500° C. is added as an additive to a hydrocarbon oil-based cold rolling lubricant in the proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent. The polar liquid reduces friction, improves cooling, improves metal cleanliness, and acts as a water scavenger to prevent staining during the cold rolling process. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent polar liquid, about 1-10 percent fatty alcohol, and a balance of hydrocarbon oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as anti-corrosion or anti-staining additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
In accordance with the present invention, a dialkylene glycol is added as an additive to a hydrocarbon oil-based cold rolling lubricant in the proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent. Preferably, dipropylene glycol or diethylene glycol may be used as the dialkylene glycol, but other dialkylene gylcols may be used as well. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent dialkylene glycol, about 1-10 percent fatty alcohol, and a balance of hydrocarbon oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as anti-corrosion or anti-staining additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
The resulting additive/cold rolling oil composition exhibits excellent lubricity and was found to lower friction at higher metal speeds and reductions. The use of an additive according to the present invention also exhibited improved cooling ability, resulting in a reduction in the temperature of the finished metal coil after cold rolling.
Additionally, the additive/rolling oil composition does not exhibit any staining of the metal when the metal is subjected to later processing steps.
In another embodiment, water may also be added to the dialkylene glycol additive or the additive/cold rolling oil composition. The addition of small levels of water to the rolling oil further facilitates the heat dissipation ability of the rolling oil without causing water staining of the metal.
Finally, dipropylene glycol has been approved for incidental contact with food when applied in accordance with FDA guidelines for residual levels. As a result, an additive in accordance with the present invention may be used in the production of metal for use in the food industry without requiring additional special cleaning processes.
In accordance with the present invention, a polar liquid with a boiling point between 25° C. and 500° C. is added as an additive to a hydrocarbon oil-based cold rolling lubricant. Proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent, of the polar liquid may be added to the lubricant as an additive. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent polar liquid, about 5-10 percent fatty alcohol, and a balance of hydrocarbon oil. Even more specifically, the additive/lubricant composition may comprise about 0.1-10 percent polar liquid, about 10 percent VX-462-WA (which comprises about 79.6 percent fatty alcohol, 20 percent fatty ester, and 0.4 percent antioxidant; available from D. A. Stuart, Warrenville, Ill.), and a balance of hydrocarbon oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as anti-corrosion or anti-staining additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
In accordance with another aspect of the present invention, a dialkylene glycol is added as an additive to a hydrocarbon oil-based cold rolling lubricant. Proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent, of the dialkylene glycol may be added to the lubricant as an additive. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent dialkylene glycol, about 1-10 percent fatty alcohol, and a balance of hydrocarbon oil. Even more specifically, the additive/lubricant composition may comprise about 0.1-10 percent dialkylene glycol, about 10 percent VX-462-WA, and a balance of hydrocarbon oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as anti-corrosion or anti-staining additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
In one embodiment of the present invention, dipropylene glycol may be used as an additive for cold rolling lubricants. Proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent, of dipropylene glycol may be added to the base lubricant. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent dipropylene glycol, about 1-10 percent fatty alcohol, and a balance of hydrocarbon oil. Even more specifically, the additive/lubricant composition may comprise about 0.1-10 percent dipropylene glycol, about 10 percent VX-462-WA, and a balance of hydrocarbon oil. More specifically, the hydrocarbon oil may be a NORPAR® or Magiesol® base oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as various types of additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
In yet another embodiment of the present invention, diethylene glycol may be used as an additive for cold rolling lubricants. Proportions of about 0.1 to about 10 percent, and preferably 1 to 4 percent and more preferably 1 to 3 percent, of diethylene glycol may be added to the base lubricant. The rolling lubricant may be a typical rolling oil, such as an oil comprising of about 1-10 percent fatty alcohol and about 1-10 percent fatty ester in a hydrocarbon oil. More specifically, the additive/lubricant composition comprises about 1-10 percent fatty ester, about 0.1-10 percent diethylene glycol, about 1-10 percent fatty alcohol, and a balance of hydrocarbon oil. Even more specifically, the additive/lubricant composition may comprise about 0.1-10 percent diethylene, about 10 percent VX-462-WA, and a balance of hydrocarbon oil. More specifically, the hydrocarbon oil may be a NORPAR® or Magiesol® base oil. The additive/lubricant is prepared by combining the ingredients, including any optional ingredients such as various types of additives, in the amounts described in any manner known to those skilled in the art. More specifically, in one aspect of the present invention the additive/lubricant may contain less than 1 percent corrosion inhibitor.
The resulting additive/lubricant composition lowered friction at higher metal speeds and reductions, and also exhibited an improved cooling ability. Because of the lower levels of friction and improved cooling characteristics of the additive/lubricant composition, the temperature of the finished metal coil was also reduced when the additive/lubricant composition was used.
Due to the low boiling points of dipropylene glycol (approximately 231-233° C.) and diethylene glycol (approximately 244-245° C.), the additive/rolling oil composition does not exhibit any staining of the metal during later processing steps. Staining did not occur when dipropylene glycol and diethylene glycol were applied to the feed metal sheet in its neat form, nor did staining occur when applied as part of the additive/lubricant composition. Due to the low boiling points of dipropylene glycol and diethylene glycol, the additive evaporates from the surface of the metal sheet when subjected to the elevated temperatures of later processing steps, such as annealing or heat treatment, without leaving a film on the metal sheet. While polyalkylene glycols may be used in conjunction with the present invention, testing has determined that polyalkylene glycols, such as UCON™ fluids (available from Dow Chemical, Midland, Mich.), have a greater risk of annealing stain.
Additionally, it was found that the addition of small levels of water, such as about 200 parts per million (“ppm”) to about 300 ppm, to the rolling oil further facilitates the heat dissipation ability of the rolling oil. It is believed that the addition of the small amounts of water to the additive/lubricant mixture produces a coupling or synergistic effect with the dipropylene glycol or diethylene glycol additive which increases the heat dissipation ability of the mixture. It was found that these levels of water could be added to the additive/lubricant mixture without causing water staining of the metal.
Finally, dipropylene glycol has been approved for incidental contact with food when applied in accordance with FDA guidelines for residual levels. As a result, the additive/lubricant composition may be used in the production of metal intended for use in the food industry without the requirement of additional special cleaning processes. This results in expanded markets for metal produced in typical mills and reduced production costs in mills producing metal particularly for the food industry.
Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents. While only specific embodiments of the invention have been described and shown, it is apparent that various alterations and modifications can be made therein. It is, therefore, the intention in the appended claims to cover all such modifications and alterations as may fall within the scope and spirit of the invention.
Several control and additive/lubricant compositions were prepared and evaluated for use in the cold rolling of metal. Formulas 1-3 were control lubricant compositions and Formulas 4-6 were experimental additive/lubricant compositions prepared in accordance with the present invention. Each composition was prepared by combining and mixing the ingredients until the composition was homogeneous using any known method.
Formula 1 was a control lubricant comprising 10 percent VX-462-WA (D. A. Stuart, Warrenville, Ill.) in NORPAR® 15 (ExxonMobil Corp., Irving, Tex.). The VX-462-WA comprised about 79.6 percent C14C16 fatty alcohol, 20 percent hydrogenated methyl tallowate, and 0.4 percent butylated hydroxytoluene.
Formula 2 was a second control sample comprising 10 percent VX-462-WA and 0.6 percent water in NORPAR® 15.
Formula 3 was a third control sample comprising 10 percent VX-462-WA and 200 ppm water in NORPAR® 15.
Formula 4 was an experimental additive/lubricant composition comprising 1.0 percent dipropylene glycol and 10 percent VX-462-WA in NORPAR® 15.
Formula 5 was an experimental additive/lubricant composition comprising 5.0 percent dipropylene glycol and 10 percent VX-462-WA in NORPAR® 15.
Formula 6 was an experimental additive/lubricant composition comprising 1.0 percent dipropylene glycol, 10 percent VX-462-WA, and 200 ppm water in NORPAR® 15.
Formula 7 was an experimental additive/lubricant composition comprising 5.0 percent diethylene glycol, 10 percent VX-462-WA, and 200 ppm water in NORPAR® 15.
Laboratory lubricity tests, also known as Four Ball Wear Tests (or the Four-Ball Method), were conducted to evaluate the control and experimental Formulas prepared above in Example 1.
The Four Ball Wear Test determines the wear protection properties of a lubricant by measuring the wear scars produced by four metal balls in sliding contact under the test parameters. Three aluminum metal balls are damped together and covered with the lubricant being tested, while a fourth ball made of steel is pressed into the cavity formed by the damped balls. The smaller the average wear scar, the better the wear protection provided by the lubricant.
The Four Ball Wear Test was conducted using a steel rotating ball with three 6061 aluminum stationary balls. The test was conducted at a temperature of 75° C. with a 40 kg load. The rotating ball was rotated at a speed of 1800 rpm for the test.
Table 1 shows the results of the Four Ball Wear Test conducted on the Formulas prepared above in Example 1.
The experimental cold rolling lubricants prepared according to Formulas 4-7 were found to have significantly improved lubricity when compared to the standard lubricant without the additive as in Formula 1. The experimental additive/lubricant compositions of Formulas 4-6 also exhibited greater lubricity than the standard lubricant with small amounts of water added as in Formula 3. Finally, Formula 6, the additive/lubricant composition with a small amount of water, was found to have lubricity very similar to that of Formula 2, the standard lubricant with a significantly larger amount of water.
Although the experimental lubricants containing dipropylene glycol, having Formulas 4-6, were found to have better lubricity than the experimental lubricants containing diethylene glycol, having Formula 7, the addition of either additive to the base lubricant exhibited improved lubricity relative to the base lubricant alone.
The data indicates that higher wear occurs at a higher dipropylene glycol concentration, suggesting a possible antagonistic effect with one of the other additives. Nevertheless, significant wear reduction due to the addition of the dipropylene glycol to the control formulas at 1 percent and 5 percent concentrations was noted.
Laboratory tests were also conducted in order to determine the cooling effectiveness off different combinations of additives and base oils. A second set of additive/lubricant compositions were prepared and evaluated to using a quench test determine the cooling effectiveness of these combinations. Each composition was prepared by combining and mixing the ingredients until the composition was homogeneous using any known method.
Quench tests were conducted using a quenchometer. A cylindrical test probe made of Inconel 600 alloy, with a chromel/alumel thermocouple located in its geometric center, is heated in a furnace to 932° F. The test probe is rapidly transferred to the additive/lubricant composition at a specified temperature. The change in temperature measured by the thermocouple within the test probe is recorded and the cooling rates of the additive/lubricant composition may be determined.
Formula 8 was an experimental additive/lubricant composition comprising 2.0 percent dipropylene glycol, 7 percent VX-462-WA, and 300 ppm water in NORPAR® 15 base oil.
Formula 9 was an experimental additive/lubricant composition comprising 2.0 percent dipropylene glycol, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 55-LX (Magie Bros. Oil Co., Franklin Park, Ill.) base oil.
Formula 10 was an experimental additive/lubricant composition comprising 2.0 percent dipropylene glycol, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 52 (Magie Bros. Oil Co., Franklin Park, Ill.) base oil.
Formula 11 was an experimental additive/lubricant composition comprising 2.0 percent UCON™ LB-285 (Dow Chemical, Midland, Mich.), 7 percent VX-462-WA, and 300 ppm water in NORPAR® 15 base oil. UCON™ fluids are polyalkylene glycols and, as such, UCON™ LB-285 is a polyalkylene glycol. The number following the UCON™ designation indicates the molecular weight of the polyalkylene glycol and therefore UCON™ LB-285 is a polyalkylene glycol with a molecular weight of 285.
Formula 12 was an experimental additive/lubricant composition comprising 2.0 percent UCON™ LB-285, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 55-LX base oil.
Formula 13 was an experimental additive/lubricant composition comprising 2.0 percent UCON™ LB-285, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 52 base oil.
Formula 14 was an experimental additive/lubricant composition comprising 2.0 percent propylene glycol, 7 percent VX-462-WA, and 300 ppm water in NORPAR® 15 base oil.
Formula 15 was an experimental additive/lubricant composition comprising 2.0 percent propylene glycol, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 55-LX base oil.
Formula 16 was an experimental additive/lubricant composition comprising 2.0 percent propylene glycol, 7 percent VX-462-WA, and 300 ppm water in Magiesol® 52 base oil.
Table 2 shows the results of the quench tests performed at 45° C. (113° F.) on Formulas 8-16, as prepared above.
It can be seen from the results shown in Table 2 that the use of different base oils resulted in only small changes in the maximum cooling rate of the additive/lubricant composition. In each case, it was found that the point of maximum cooling was shifted to a higher temperature by 20-30° F. through the use of the Magiesol® base oils.
The experimental tests also show that dipropylene glycol was more effective at accentuating the cooling effects of water than propylene glycol. While the inventors do not wish to be limited by theory, it is likely that this more effective cooling of dipropylene glycol is a result of the extra oxygen present in dipropylene glycol, which allows for more effective hydrogen bonding.
To further examine the cooling effectiveness of dipropylene glycol and polyalkylene glycols, quench tests where conducted on additive/lubricant compositions at different temperatures. Quench tests were conducted on dipropylene glycol, polyalkylene glycol (UCON™ LB-625 and UCON™ LB-285 fluids), and water additives. Each of these additives was separately added to a base composition of 7.0 percent VX-462-WA in NORPAR® 15 and the quench tests were conducted at temperatures of 600, 700, and 800° F.
Table 3 shows the results of the quench tests performed.
As may be seen in Table 3, it was determined that polyalkylene glycols and water had the most influence over maximum cooling rate at high temperature. However, dipropylene glycol gave higher cooling rates at 600-700° F.
To determine the potential risk for staining, thermogravimetric analysis (TGA) of several potential additives was completed and the TGA residue of the potential additives was measured at 300° C.
TGA is a thermal analysis technique used to determined the amount of residue left by a composition at a particular temperature. A sample of the composition is placed into a tared sample pan which is attached to a sensitive microbalance assembly. The sample holder is placed in a high temperature furnace and the balance assembly monitors changes in the mass as heat is applied to the sample. The amount or percent of noncombusted residue at a final temperature, in this case 300° C., is then measured to determine the potential staining risk of the composition.
The TGA residue tests were conducted on propylene glycol, dipropylene glycol, and three polyalkylene glycols (UCON™ LB-625, UCON™ LB-285, and UCON™ LB-260 fluids). These additives were tested in an experimental design to determine the effect of these additives on TGA residue.
Table 4 shows the results of these tests.
As may be seen in Table 4, the TGA test results suggest that annealing residues would possibly be a concern with polyalkylene glycol. As explained above, the UCON™ fluids are polyalkylene glycols and the number following the UCON™ designation indicates the molecular weight of the polyalkylene glycol. As may be seen in Table 4, the TGA test results indicate that lower molecular weight polyalkylene glycols, such as UCON™ LB-260, are preferred, as they are more volatile and are less prone to staining. Therefore, the concentration of polyalkylene glycol in the additive should be the minimal necessary for improved cooling. On the other hand, the propylene and dipropylene glycols were found to have minimal impact on TGA residue. In particular, it was found that dipropylene glycol is completely “burned-off” from the surface of the metal at 190° C.
The stability of the second set of experimental additive/lubricant compositions was also tested. The stability of the experimental additive/lubricant compositions was tested at room temperature (77° F.) for 14 days and a 120° F. for 14 days.
Table 5 shows the results of the stability testing performed on Formulas 8-16, as prepared above in Example 4.
As may be seen in Table 5, it was found that all of the experimental additive/lubricant compositions were stable at 120° F. for 14 days and all of the samples, save Formulas 15 and 16, were also stable at room temperature for 14 days. It was determined that Formulas 15 and 16 failed to remain stable at room temperature, which suggests that the propylene glycol did not form a stable composition with the Magiesol® base oils and water.
Laboratory lubricity tests, also known as Four Ball Wear Tests as described in Example 2, were conducted to evaluate the experimental compositions, Formulas 8-13 as prepared above in Example 3.
The Four Ball Wear Test was conducted using a steel rotating ball with three aluminum stationary balls. The test was conducted at a temperature of 70° C. with a 40 kg load. The rotating ball was rotated at a speed of 1800 rpm for the test.
Table 6 shows the results of the Four Ball Wear Tests performed on Formulas 8-13, as prepared above in Example 3.
As can be seen Table 6, the use of different base oils has a minimal effect on the wear performance of the additive/lubricant compositions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 60451473 | Mar 2003 | US | national |
This application is based on and claims benefit of U.S. Provisional Application Ser. No. 60/451,473, filed Mar. 3, 2003.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US04/04620 | 2/17/2004 | WO | 5/25/2006 |
