Page 18 - MetalForming March 2011

Additives
Key toLube
Success
Two Northeastern-U.S. lubricant formulators and one of their metalforming customers explain how new lubricant recipes contribute to improved performance in the press, particularly when deep-drawing difficult-to-form materials and cosmetic parts.
BY BRAD F. KUVIN, EDITOR
By introducing performance addi- of a single ‘silver bullet’ type of additive,
tives into the mix, metalforming-
lubrication suppliers create formu- lations that, besides reducing friction and preventing tooling and part material from sticking together, strive to maximize lubri- cant service life. According to Joe Purn- hagen, global commercial manager of metal processing additives for the Lubrizol Corp., Wickliffe, OH, oil-based metal- forming lubricants have long-excelled at providing good service life and minimal maintenance requirements. In these fluid types, lubricant formulators are primarily concerned with additive solubility in the base oil, and achieving the right balance of different additives to meet the performance requirements of the given application.
Conversely, says Purnhagen, water- based (emulsion) metalforming lubricants present a much greater design challenge. “The presence of water creates an ideal breeding ground for microbes, and control of corrosion is more difficult in a water- based system,” Purnhagen says. “Perfor- mance additives used in metalforming lubricants include lubricity enhancers, extreme-pressure (anti-weld or sticking) agents, corrosion inhibitors, emulsifiers and biocides. Achieving long service life from water-based metalforming lubri- cants is not as simple as the introduction
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but a result of careful consideration of the entire performance additive system and the interaction between the various components. The additives that deliver the primary functions of the fluid for the forming operation—lubrication and cor- rosion protection—will cease to perform properly if the overall system in which they are delivered becomes unstable.”
Emulsifier additives are the key com- ponents that allow for a lubricant to mix with water, and retain a stable mixture over an extended period of service. Various types of emulsifier additives are used in soluble-oil (milky appearance) and semi- synthetic (translucent appearance) met- alforming-fluid formulations.
“These additives provide the ability to create stable emulsion of materials that are inherently insoluble in water,” says Purnhagen, “such as petroleum oils, esters, vegetable oils and synthetic base stocks. In modern lubricant formulations, a care- fully balanced ratio of several different emulsifier chemistries is used to achieve the ideal performance for a particular application. The emulsifier system must be durable enough to maintain consistency through the demanding service conditions in a stamping press, including high pres- sure and introduction of metallic content