from the conferences organized by TANGER Ltd.
One of the most important parameters used for qualitative evaluation of lubricants in cold drawing of steel wires is the coefficient of friction. Its magnitude cannot be determined directly, but it can be determined from the measured total drawing force (TDF) or total drawing torque (TDT). In addition to the coefficient of friction, the TDF is mainly influenced by the size of the partial strain during pass and also by the geometry of the die, which is mainly described by the die approach angle. In order to determine the coefficient of friction for the individual analysed lubricating oils, a series of experiments was carried out, consisting of drawing a phosphated low-carbon steel wire with a diameter of 5.5 mm in one pass on a Koch KGT direct drawing machine. In total, two single pass reduction values were used for the evaluation of four oils (when drawn to a diameter of 5.1 resp. 4.9 mm, it was 14 resp. 20.6 %) and 6 different die approach angles (8 to 18°). The TDF was determined from the measured TDT and the coefficient of friction was determined inversely from the Siebel TDF equation. For a strain of 20.6 %, the correlation between the measured and calculated values as a function of die approach angle was high, but at a strain of 14 % the data showed a low correlation. Therefore, the data were corrected using the contact pressure value, which is also a function of die geometry. Thanks to this modification, a new equation was established for calculating the frictional component of the TDF under conditions of mixed friction.
Keywords: Steel wire, drawing, coefficient of friction, total drawing force, lubricating oils, geometry of die© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.