Patent Application
20080090740
The present invention discloses a lubricant for use in hot-forging applications, such as those utilized in forging aluminum and aluminum workpieces into the desired articles. Such hot forging applications require lubricant materials that do not produce smoke or flame in the general temperature range of about 300° C. to about 600° C. In order to comply with safety and health regulations, such lubricants are substantially lead-free.
The lubricant of the present invention is an oil-based lubricant. The oil utilized may be virtually any composition known in the art, including but not limited to mineral oil, such as naphtenic, aliphatic, paraffinic or steam cylinder oil, vegetable oil, such as sunflower oil, olive oil or rapeseed oil, animal oil, such as lard oil, synthetic oil, such as polyalphaolefins and silicone oil, semi-synthetic oil, such as glycerol trioleate and mixtures thereof. Preferred oils include vegetable, mineral and animal oils. Such oils are commercially available as Process Oil 1000 from Texaco (UK), Lard oil from Welch, Holm and Clark Co. (USA), Soybean oil from BG International (USA.).
A second component of the lubricant is a graphite additive. The graphite may be in any form known in the art, including but not limited to coarse, fine, milled, unmilled, natural, synthetic or mixtures thereof. The graphite component of the lubricant provides for a physical separation between the workpiece and the die during the forging operation. Fine graphite having a particle size distribution with about 90% of the particles below 15 microns in size is especially preferred. Such graphite is commercially available from Acheson Industries, Inc.
One or more phosphorus-based additives are included in the lubricant. The phosphorus additive reduces and eliminates burning of the lubricant at high temperatures. The phosphorus can be in any desired form, such as phosphate, ester phosphate, phosphate amine, ammonium phosphate or mixtures thereof. One preferred phosphorous-based material is phosphate ester. Such phosphorous is commercially available from Connect Chemical (F), Ferro (USA).
The hot forging lubricant composition optionally contains one or more metallic lubricating additives. The metallic additives may be chosen from one or more of the metallic elements, including tin, bismuth, zinc, aluminum or any alloys thereof.
The lubricant composition may optionally contain additional ingredients such as dispersants, rheology modifiers, biocides, anticorrosives, extreme pressure additives, antifoam agents, wetting agents, metal soaps and mixtures thereof.
The lubricant of the present invention comprises in the range of about 1 to about 99 weight percent oil, preferably in the range of about 1 to about 70% oil and most preferably in the range of about 15 to about 40 weight percent oil. The lubricant contains in the range of about 1 to about 99 weight percent graphite, preferably in the range of about 1 to about 30 weight percent graphite and most preferably in the range of about 3 to about 20 weight percent graphite. The lubricant contains in the range of about 1 to about 99 weight percent phosphorous additive, preferably in the range of about 1 to about 80 weight percent phosphorous additive and most preferably in the range of about 30 to about 80 weight percent of the phosphorous additive.
A further embodiment of the invention comprises a method for forging an article. The method comprises the steps of applying the lead-free lubricant to one or both of the forging apparatus or the workpiece to be forged. The workpiece is inserted into the forging apparatus and forged into the desired article. The forging apparatus is opened and the article is easily removed due to the presence of the lubricant. In an alternative embodiment, the workpiece is inserted before the application of the lubricant and the workpiece and die surface are then lubricated simultaneously
The invention is further illustrated by the following non-limiting example:
Example. A lubricant composition may be produced by adequately mixing the raw materials together via standard mixing techniques, such as mastication of stirring. The composition of the samples is shown in Table 1.
The lubricant composition of Table 1 was applied on hot forging dies at temperatures of 440° C.±40° C. The dies were utilized for a series of hot aluminum forging applications and the lubricant did not produce flames during the process. In addition, the lubricant properties relating to the die and the aluminum part being forged were superior.
Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.
