Page 39 - MetalForming Magazine May 2023

THE PATH TOWARD
OIL-FREE METALWORKING FLUIDS
tribute between the time a lubricant enters an operation until its disposal. However, company initiatives and cus- tomer demands can drive efforts toward sustainability, including adopt- ing new compositions, saving energy by lowering the temperature needed for parts cleaning and using fluids that offer easier removal from parts.
“I see a long-time trend toward semisynthetic, emulsion-based prod- ucts,” says Marty Brunker, senior sales account manager at Univar Solutions, a specialty chemicals distributor, adding that semisynthetics prove much more versatile than either fully synthetic fluids or mineral-oil prod- ucts. Fluid formulations using oil-sol- uble additives require an oil compo- nent, he also notes, and an oil film on the workpiece provides a barrier against corrosion.
Chad Crocker, territory sales man- ager for S&S Chemical, also sees a long- term trend away from mineral oils toward semisynthetics with low to medium oil content. Severe operations such as deep drawing still require lubricity additives (i.e., chlorinated paraffins, especially longer-chain paraf- fins) that make some amount of oil and emulsifier necessary. However, lubricity additives have improved, offers Crocker, including good options such as esters and phosphate esters— fluid manufacturer Castrol moved on from chlorinated compounds many years ago, he adds, so it can be done. However, MWFs require a balance of different properties, and pricing remains a big factor.
“Right now,” Crocker says, “oil is cheaper than additives.”
Crocker mentions multiple proj- ects over the past 15 yr. where com- panies developed MWFs using veg- etable-based oils. However, he notes, the economic crash in 2008 and the COVID-19 pandemic halted many experimental projects for the next generation of MWFs. Another factor: fluctuations in petroleum prices, Crocker points out, as some MWFs can contain as much as 50 percent mineral oil.
Changes in Formulations
Oil-free fully synthetic fluids have a niche, according to Brunker, mostly for clean-running applications that don’t require a great deal of lubricity or long-term corrosion inhibition from the MWF. High speeds and low pres- sures are ideal for these fluids, he says. For instance, light grinding applications
“You see their formulations becom- ing very complex, using different raw materials to reduce the price and the potential for foam,” Brunker says.
Also, dilution-water quality varies from location to location, and even among different shops within a given area, thus a water-dilutable formula- tion that works in one shop might foam
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Light- to medium-duty applications can use fully synthetic fluids, but these formulations rely on water- soluble additives, meaning that they require different extreme-pressure additives than oil-soluble, emulsifiable additives such as chlorinated paraffins.
excessively in another. Reduc- ing antifoaming agents in a for- mulation reduces costs and cuts down on the number of raw materials needed for the formula- tion.
Lower-oil sys- tems tend to run cleaner, accord- ing to Crocker, as high-oil systems run under higher
for metals such as cast iron or steel can employ synthetic fluids. However, the lack of an oil component limits the types of fluid additives available for use and the number of applications for a given formulation.
Brunker notes that the technology does not yet exist for lubricity additives and corrosion inhibitors for synthetic fluids to be used with higher-demand applications. Conversely, fully synthetic fluids more efficiently draw heat away from the cutting area because they do not contain high levels of solids that limit the cooling capacity of oil-con- taining fluids. Because synthetic fluids don’t often use surfactants or other additives that produce foam, they often don’t require antifoaming agents, and many of the lubricity components in synthetic fluids also help to reduce foaming, Brunker offers—another fac- tor that makes these fluids attractive.
Indeed, some fluid manufacturers have moved on from certain antifoam- ing agents, including silicones and siloxanes, which can adhere to the workpiece and cause paint-adhesion problems.
pressure, making them more likely to generate mist and foam. Even in enclosed systems, mists can settle on machines and workpieces, leaving residue when water evaporates. While most U.S. facilities employ mist guards and enclosures, facilities in some other parts of the world do not, making this a worker-health issue.
We also see movement toward biobased oils, but their biodegradabil- ity, attractive from a waste-disposal standpoint, also shortens MWF service life. Rapeseed and canola oil represent the most common vegetable-based oils for MWFs. However, according to Crocker, mineral oil is the best call for heavy-duty operations.
Light- to medium-duty applications can use fully synthetic fluids, but these formulations rely on water-soluble additives, meaning that they require different extreme-pressure additives than oil-soluble, emulsifiable additives such as chlorinated paraffins. For straight oils and semisynthetics, the oil component acts as both an additive carrier and a lubricant. Fully synthetic fluids—several are on the market—rely