Improving the quality of high and low-carbon steel rods employed in wire drawing operations

High and low tensile strength as well as high ductility are required for both, high and low-carbon steel rods which are to be further processed in wire drawing operations. In addition to chemical composition, suitable cooling rates are important for the control of mechanical properties, as far as the Stelmor process is concerned. In this investigation, heat transfer models are coupled with the kinetics of austenite transformation into pearlite and ferrite-pearlite, respectively, in order to understand the link between the Stelmor process parameters and the final quality of low and high-carbon steel rods. In applying these models a considerable difference occurred in the mechanical properties of high-carbon rod samples taken from the loop edge of the Stelmor conveyor and those taken from the loop center. The latter showed higher tensile strengths, furthermore, the difference to the lower-strength samples increased with low conveyor speeds. Most homogeneous mechanical properties were found for a conveyor speed of 0.4 m/s. In the case of low-carbon steels, low nitrogen contents during steelmaking and a slow and controlled cooling in the Stelmor process were found to be the most important factors regarding mechanical properties. The conclusions of this investigations are actually being applied to production so as to obtain a better quality of steel rod semies.