Cold drawing schedules for RSt 34-2 (1.0034) steel wire for correction of overheating defects and breakless ensuring

Abstract

The paper’s authors researched the defects correction for RSt 34-2 (1.0034) steel wire, obtained as result of its overheating at 1140...1160 °C. Instead of the re-heat treatment method, the authors proposed five cold drawing, annealing and overheating combination schedules, which ensure the increase in strength to DIN EN ISO 6892-1-2020 requirements. The experiments were performed on 4 mm diameter wire with increased grain size (up to 70 μm). It was found that at low initial values of wire material’s ultimate strength and yield strength there are frequent breaks of the wire at ends clamping by tongs. An equation that allows to predict the acceptable cross-sectional area of the wire end sections during drawing has been devised. An inequation for relating the Korber-Eichinger equation parameters and the wire ends sharpened sizes with reduced area due to the tongs jaws deepening after clamping the wire ends has been work out. The authors experimentally proved that the drawing overheated wire process designing taking into account the conditions of this inequation guarantees the elimination of breaks both at the wire end (at the drawing beginning) and at the process stable stage. The drawing processes for overheated wire have been developed eliminated the additional heat treatment operation to overheating defects correction.