Lubricated on wire New lubricants extend the limits of cold metal forming

At the Fraunhofer Institute for Applied Polymer Research (IAP), the positive effect of poly lubricants on wire production is being investigated.

Metals can be processed into wires through cold forming, but this is an extremely complex process, say the IAP researchers. Moreover, the lubricants required often do not meet the demands of the end-users. As part of the KMU-innovativ project "Polyschmierung," five partners from industry and research have therefore developed a new class of polymer lubricants. They are intended to make the forming process significantly more environmentally friendly and economical. The novel lubricants are already being successfully used industrially, as emphasized by the IAP. The project was funded with approximately 680,000 euros, by the Federal Ministry of Education and Research BMBF via the Project Management Agency Karlsruhe (PTKA).

The problem with conventional wire drawing

Metal springs, wire mesh, or nails are products that ultimately originate from the cold forming process of wire drawing – a procedure associated with intensive pre- and post-treatment and high effort. In this cold forming of metals, a previously hot-rolled wire, up to 50 millimeters thick, is pulled through a series of drawing dies with successively smaller openings. This process elongates the metal and continuously reduces its diameter, explain the researchers. Lubricants or drawing compounds play a critical role in this process. Their functions are to reduce friction, minimize heat development, protect against corrosion, improve formability, and extend the life of the drawing dies. However, before applying the lubricant, the base metal must also undergo intensive treatment, and a carrier layer must be applied. This carrier layer, however, needs to be removed later, which is costly, time-consuming, and environmentally damaging because it involves chemical agents. Often, the existing range of lubricants does not meet requirements, as already mentioned above. This is because, in addition to significant effort, it can, for example, lead to cold welding of the wires if the pretreatment and the drawing lubricant do not function properly.

It lubricates better with sustainable polymer systems

As part of the project, researchers, in close collaboration with industry partners who face such challenges on a daily basis, have developed innovative polymer-based lubricants. The requirements for the new lubricant were high, admit the experts. It was supposed to consist of environmentally friendly, water-soluble polymers and reduce the treatment effort before drawing. Despite thinner layers on the metal, it should more efficiently reduce friction-related energy loss and thus significantly minimize accompanying tool wear. The polymers developed at the IAP meet all these conditions, as the team can emphasize. They are applied directly to the metal, thus without complex pretreatment. Because they are water-soluble, they can easily be removed afterward with a gentle water-based solvent. This new class of polyschmiermittel (polymer lubricants) is given the abbreviated name HPPL (High Performance Polymer Lubricant).