Seeking New Additives for Metalworking


STUTTGART, Germany – Metalworking fluid suppliers are facing challenges from changes in the raw materials they are able to use and also from shifts in the type of metal forming operations employed by industry, Lanxess officials told a conference here last month.

As a result, they predicted that formulators will lean more heavily on certain types of chemistries, such as sulfur-carrying extreme pressure additives.

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Addressing the Mineral Oil Technology Forum organized by Uniti, the German association of medium-sized mineral oil companies, Lanxess Senior Application Technology Manager Wilhelm Rehbein said that one of the biggest challenges facing metalworking fluid suppliers is the ongoing broadside regulatory attack on chlorinated paraffins, which have long served as effective extreme pressure additives.

Chlorinated paraffins include a range of varieties defined by the length of their molecules. Short-chained chlorinated paraffins have already been banned by numerous countries because they persist in the environment, accumulate in humans and animals and are suspected of causing cancer. The European Union and the United Nations are considering proposals to ban medium-length varieties, and the United States is discussing potential bans on medium-length and long varieties.

At the same time, Rehbein said, fluid suppliers are coping with a shift in base stock supply from API Group I to Group II and III oils. Group I oils accounted for 74% of global mineral base oil production capacity in 2007, but just 30% by 2020. Group II and III oils, which have picked up the share lost by Group I, offer advantages in better antioxidation performance, lighter color and less odor, he noted, but unfortunately they also provide less solvency for many of the additives used in metalworking fluids.

Meanwhile, the rising popularity of electric vehicles is causing shifts in the metalworking processes used by the auto industry. EVs mean less need for crankshafts, camshafts, engine blocks and gear boxes, all of which are manufactured through chip removal processes such as drilling, cutting and lathing. Instead, plug-in hybrids and vehicles powered purely by battery have rotor- and stator sheets and battery components made through stamping, fine blanking and drawing processes.

“This means increased need for fluids and prelubes” used to prepare metals before they are formed, Rehbein said. “That requires transformation to higher viscosity, better lubricating properties and increased content of extreme pressure and antiwear additives for high-performance applications.”

Types of metals used – for EVs and other types of products – are also evolving. The push toward lighter products is leading manufacturers to use materials with greater strength-to-density ratios, such as advanced and ultra-high strength steels, and in stamping processes they cause excessive abrasive wear due to the metal’s high tensile strength and tendency to spring back.

Consequently, fluids used for chip removal or stamping and drawing processes require increased extreme pressure and antiwear performance, Rehbein said. They also need to be compatible with titanium, aluminum and magnesium alloys.

Matthias Mickler, Lanxess’ head of application technology for Europe, the Middle East and Africa, said the company has been seeking sulfur-carrying chemicals that could replace chlorinated paraffins and meet the developing needs of metalworking manufacturers. Mickler said there are numerous sulfur-carriers offering a range of polarities and activities and that Lanxess found they offer outstanding efficiency over a broad temperature range.

He said they are also compatible with most metalworking fluid additives and that their performance can be enhanced by combining them with over-based sulfonates, polycarboxylates and other polar compounds. And they can be disposed of through standard waste treatment methods, as opposed to chlorinated paraffins, which are expensive to disposed of where highly regulated.

“By combining suitable sulfur carriers and other lubricant additives, it is possible to adjust the characteristics of metalworking fluids to the specific demands of the processes and to even exceed the performance of cutting and forming lubricants containing chlorinated paraffins,” Mickler said.

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