Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Elemental sulfur – selenium – or tellurium
Reexamination Certificate
2002-07-25
2004-03-23
McAvoy, Ellen (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Elemental sulfur, selenium, or tellurium
C508S463000, C508S496000, C072S042000
Reexamination Certificate
active
06710021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to compositions for lubricating articles in metalworking operations. More particularly the present invention relates to lubricating compositions, which are non-corrosive and non-staining to non-ferrous metals.
2. Brief Description of Related Technology
Metalworking processes mechanically shape and work metallic articles or work pieces. Lubricating fluids are often used on the work pieces in metalworking processes to reduce friction between a tool and the work piece and to dissipate heat resulting from any remaining friction. The reduction of friction and dissipation of heat promotes tool life, increases production and allows the attainment of high quality finished metal products.
Metalworking operations mechanically shape and work metallic work pieces by cutting and non-cutting operations. The cutting processes include, for instance, drilling, grinding, milling, tapping, turning and broaching. Non-cutting processes include, for example, rolling, drawing, extrusion, drawing and ironing, punching, stamping and spinning processes. These metal working processes are often characterized into three general categories (for instance, light duty, medium duty and heavy duty) according to severity of the operation. Light duty jobs may include boring and milling. Medium duty may include tapping, reaming and gear cutting. Heavy duty may include broaching and threading. Increased friction and increased heat generation generally coincide with increased severity or duty of a particular metalworking process.
The type of metal also often influences the duty of the metalworking operation. For example, a metalworking operation on a stainless steel is often a more severe, operation than a similar operation on a carbon steel due to the higher strength of the stainless steel.
Lubricating fluids for metalworking operations are also distinguished by duty corresponding to a particular metalworking operation. A light duty fluid is generally appropriate for lubricating light duty metalworking operations. A heavy duty fluid has greater lubricity characteristics than a light duty fluid and is generally appropriate for lubrication in a heavy duty operation. Increased lubricity of a heavy duty fluid is often partially achieved through the use of a more viscous oil than used for light duty fluid.
Additives may also be incorporated into a heavy duty metalworking fluid to increase the lubricity of the fluid at metal-to-metal contact points, such at points where a tool contacts a work piece. Sulfur is a common additive used to increase lubricity at metal-to-metal contact points. Many fluids would not function as a heavy duty metalworking lubricant without the use of a sulfur additive.
A heavy duty lubricant containing sulfur, however, may not always be appropriate for the lower duty operations or heavy duty operations with particular work pieces. While a sulfur-containing heavy duty fluid can generally provide adequate lubricity for light, medium and heavy duty metalworking operations, sulfur-containing heavy duty fluids often stain or corrode non-ferrous metals. As such, there is a need for a sulfur-containing metalworking fluid suitable for heavy-duty operations, which does not stain or corrode nonferrous metals.
SUMMARY OF THE INVENTION
The present invention provides compositions for heavy duty metalworking fluids that do not corrode or severely stain nonferrous metals. The inventive compositions also provide greater lubricity for metalworking processes using ferrous and nonferrous metals. Improved product finishes result from the use of the inventive compositions on both ferrous and nonferrous metallic articles.
In one aspect the present invention provides a metalworking fluid composition that does not stain non-ferrous metals and is useful for heavy duty metalworking operations thereon. In one desirable feature the present inventions contains greater quantities sulfur than previously achieved in the prior art to increase lubricity and wear characteristics of a metalworking oil without staining nonferrous articles.
In another aspect of the present invention lubricating compositions are provided which include a fatty oil to inhibit staining of non-ferrous metals during metalworking processing. Useful fatty oils include monoglycerides, diglycerides, triglycerides, esters of monocarboxylic acids, esters of dicarboxylic acids and combinations thereof. The fatty oils may also be sulfurized, chlorinated or chlorosulfurized.
The invention will now be described with reference to the section entitled “Detailed Description of the Invention.”
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to metalworking fluid compositions suitable for heavy duty metalworking processes without the disadvantages described above. A metalworking lubricant serves many functions, including use as a heat-transfer medium, providing protection against rust and corrosion, and serving as a carrier for debris. Among the many other advantages and uses of the inventive metalworking compositions are (1) preventing corrosion and staining of the tool and the work piece; (2) keeping a metalworking tool cool and preventing it from being heated to a temperature at which the hardness and resistance to abrasion are reduced; (3) maintaining the work piece cool, thereby preventing it from being machined in a warped shape to inaccurate final dimensions; (4) providing a good finish on the work piece; (5) aiding in satisfactory chip formation to promote the metalworking operation; (6) washing away chips, especially in deep-hole drilling, milling and grinding; (7) lubricating moving machine parts close to the cutting tool; and (8) reducing power consumption of the metalworking operation through lubrication.
In one aspect the inventive composition is an oil-based lubricant. An oil-based fluid composition is particularly useful in metalworking operations where lubrication and high grade finishing cuts are especially desirable, or where aqueous fluids adversely effect product finishes. For example, frictional heat from the metalworking operation is dissipated in an oil film resulting from application of the oil onto a work piece. The amount of heat dissipated is generally related to the film thickness, fluid velocity and fluid density. Insufficient heat dissipation can often cause high fluid temperatures that decrease the viscosity of the oil sufficiently to break down the film. Such a film breakdown can result in metal-to-metal contact between the tool and the work piece. Metal-to-metal contact can often result in failure of the tool, the work piece, or both the tool and the work piece.
Thus, film thickness, fluid density, velocity and viscosity are important properties for such an oil-based lubricating composition. High severity or heavy-duty metalworking operations generally require oil-based lubricants with a high viscosity to provide adequate lubrication. Oil-based lubricants may be broadly classified into duties based on their viscosity. The viscosity ranges described herein are not intended to limit the scope of the invention, but are generally recognized in the industry and are intended to serve as examples to aid in the understanding of the invention. A light duty fluid generally has a kinematic viscosity from about 10 cSt (centistokes) at 25° C. to about 30 cSt at 25° C. A medium duty fluid generally has a kinematic viscosity from about 30 cSt at 25° C. to about 75 cSt at 25° C. A heavy-duty fluid generally has a kinematic viscosity greater than 75 cSt at 25° C. A heavy-duty fluid which has a maximum kinematic viscosity of 160 cSt at 25° C. is particularly useful as a heavy duty metalworking fluid.
In another aspect of the present invention, an inventive composition which serves as a heavy duty metalworking fluid with a kinematic viscosity range of about 75 cSt to about 160 cSt at 25° C. is useful. Desirably, compositions of the present invention may have a kinematic viscosity range of about 75 cSt to about 90 cSt at 25° C.; and more desirabl
Bauman Steven C.
Henkel Loctite Corporation
McAvoy Ellen
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