Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Graphite – coal – or elemental carbon
Reexamination Certificate
1998-12-21
2001-02-27
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Graphite, coal, or elemental carbon
C508S148000, C508S143000, C508S154000, C508S156000, C508S158000, C508S539000, C508S175000, C072S042000, C072S043000, C072S046000
Reexamination Certificate
active
06194357
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a waterborne lubricant for use during the plastic cold working (e.g., forging, tube and pipe drawing, wire drawing, and the like) of stock of a metal such as iron, steel, titanium, titanium alloy, copper, copper alloy, aluminum, aluminum alloy, and the like. Below, this lubricant is referred to simply as the “waterborne lubricant”.
REVIEW OF RELATED ART
Lubricants that form a liquid or solid film are used in the plastic working of metals, for example, in the cold drawing of steel tubing and pipe. These lubricants facilitate drawing by reducing the friction between the work piece and the tool, e.g., die, plug, or the like, and thereby prevent scuffing and seizure.
Among lubricants of this type, the so-called oil-based lubricants are typical of the liquid lubricants. The base oil in oil-based lubricants is a mineral oil, animal or plant oil, or a synthetic oil. Lubrication is generally carried out by flowing the oil-based lubricant directly onto the tool or work piece from a lubricating oil applicator built into the processing equipment. Oil-based lubricants are frequently used in the case of relatively low degrees of working. In the case of heavy working, the oil viscosity is increased or a solid lubricant or extreme-pressure additive is added. Typical of the solid films are the so-called conversion coatings in which a carrier film that tenaciously adheres to the substrate is formed by a reaction with the work piece. Phosphate coating treatments that form a zinc phosphate-based film are used with carbon steels and low-alloy steels, while oxalate coating treatments that form an iron oxalate-based film are used with stainless steel. A reactive soap lubrication treatment is generally performed after these conversion coating treatments. The combination of these two processes gives a lubrication method with a very high resistance to seizure, because of the combination of the carrier function of the conversion coating and the lubricating function of the reactive soap lubricant. This sequence of reactive soap lubrication treatment after a conversion coating treatment is generally carried out by immersing the work piece in various treatment baths prior to drawing. However, since reactive treatments are involved, the treatments are carried out on batches of several tens of units in order to minimize variations in lubricant add-on, even though parts of the work pieces may be brought into lineal contact with each other to a greater or lesser degree.
However, requirements for higher speeds and higher pressures in the working operation as well as environmental and energy considerations have created demand for a lubricant which can solve the problems associated with conversion films while still exhibiting a lubricating function equal to or greater than that for the combination of a conversion coating treatment with a reactive soap lubrication treatment. Conversion films are associated, for example, with environmental and cost problems and with problems in removing the lubricant film after the working that utilized the film is complete. The environmental problems include issues with waste management and issues concerned with the working environment. For example, due to the use of an acidic treatment bath maintained at 80° C. to 90° C., the treatment bath has a disagreeable odor and its mist degrades the immediate environment of the bath. The cost issues involve shortening the process and economizing on energy and space. Finally, the problems with post-working film removal have generally required alkaline degreasing plus an acid treatment.
Within the realm of oil-based lubricants that address the problems described above, Japanese Patent Publication [Kokoku] Number Hei 4-1798 [1,798/1992] discloses a “cold working lubricant in which a metal soap or solid lubricant is blended into a lubricating oil comprising the blend of a plant or animal oil, a copolymer of isobutylene and n-butene, and an extreme-pressure agent such as chlorinated paraffin or phosphate ester”. However, even though this is a high-performance lubricating oil, its performance in working operations is somewhat poorer than that afforded by reactive soap lubrication treatment after a conversion coating treatment. Moreover, since large amounts of extreme-pressure agent (a term which is equivalent to “extreme-pressure additive”) are used, undesirable odors are generated during the working operation and there is a risk of adverse effects such as work piece corrosion by chlorine or phosphorus in the post-working step of softening and annealing.
The waterborne lubricants include lubricants which are used wet and lubricants which are used in the form of their dried films. Like the oil-based lubricants discussed above, the wet-use waterborne lubricants are used by direct application to the tool or work piece. The dry-use waterborne lubricants, like the conversion films discussed above, provide a solid film by immersion in a treatment bath followed by evaporation of the water fraction in a drying process. An example of the wet-use waterborne lubricants is disclosed in Japanese Patent Publication [Kokoku] Number Sho 58-30358 [30,358/1983]. This reference discloses a “lubricant for the cold or hot working of metal tubing, comprising a bicarbonate salt (solid) as the main component and small amounts of dispersant, surfactant, and solid lubricant”. This lubricant, however, has not achieved wide use in place of conversion coating treatments. With regard to dry-use waterborne lubricants, Japanese Patent Application Laid Open [Kokai or Unexamined] Number Sho 52-20967 [20,967/1977] teaches a “lubricating coating composition comprising water-soluble polymer or a waterborne emulsion thereof as its base, which is blended with solid lubricant and a conversion film-forming agent”. In addition, Japanese Patent Application Laid Open [Kokai or Unexamined] Number Sho 50-147460 [147,460/1975] discloses a “method for drawing stainless steel wire using the combination of a borax-based film and lime soap or metal soap”. However, when the dry film is produced by immersing a large number of workpieces at one time followed by forced drying, a nonuniform add-on is inevitably produced by the partial contact that occurs among workpieces. As a result, these dry-use lubricants are unable to solve a major problem with nonreactive lubricants, i.e., a pronounced tendency for seizure to occur during drawing operations.
Thus, as discussed above, no lubricant has appeared that can meet all of the demands elaborated above (single step, working performance, environmental issues, waste management, energy savings, film removal, etc.) and is able to replace the combined lubrication system of conversion coating treatment (phosphate treatment, oxalate treatment, etc.)+reactive soap treatment.
PROBLEMS TO BE SOLVED BY THE INVENTION
The present invention was developed in order to meet the requirements outlined above. The object of the present invention is to provide a one-step, highly lubricating waterborne lubricant for use in the cold plastic working of metals, that can replace the conversion coating treatment+reactive soap treatment combined lubrication system, is free of the environmental issues described above, provides for facile film removal, and/or is not subject to the decline in seizure resistance caused by nonuniform add-on when large numbers of individual workpieces are treated by immersion.
SUMMARY OF THE INVENTION
It has been found that the above stated object of the invention can be achieved by a waterborne lubricant comprising, preferably consisting essentially of, or more preferably consisting of, in addition to water:
(A) as its base, a water-soluble inorganic salt that strongly adheres to the substrate, and that can introduce the lubricating component(s) to the tool surface and maintain the lubricating component(s) in place during the cold working operation;
(B) as lubricating component, a solid lubricant;
(C) as lubricating
Koyama Takashi
Matsumura Yoshio
Murata Motoharu
Nishizawa Yoshihiko
Harper Stephen D.
Henkel Corporation
Jaeschke Wayne C.
McAvoy Ellen M.
Wisdom, Jr. Norvell E.
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