The influence of the multipass drawing process in clasical and hydrodynamic dies on residual stresses of high carbon steel wires

Abstract

In the paper the influence of the multipass drawing process on residual stresses of high carbon steel wires has been assessed. The drawing process of φ5.5 mm wires to the final wire of φ1.6 mm was conducted in 11 passes, in industrial conditions, by means of a modern Koch multi-die drawing machine. The drawing speed in the last passes was 10 m/s. The experimental measure of residual stresses in wires drawn in classical and hydrodynamic dies by Sachs-Linicus method has been done. On the basis of numerical analyses of the wire drawing process, the distributions of longitudinal residual stresses on the cross section of wires, temperatures and redundant strain have been determined. The investigations have shown the essential influence of the multipass drawing process in hydrodynamic dies on residual stresses of high carbon steel wires. In the case of the wires drawn with hydrodynamic dies, in comparison to the wires drawn in classical dies, the 30% decrease of longitudinal residual stresses have been noted. It has been shown that the decrease of residual stresses in wires drawn in hydrodynamic dies is connected with a lower redundant strain by 14.7%. In addition, the application of hydrodynamic dies in the multipass drawing process leads to significant decreasing of temperature of the wire surface (in the last pass above 500°C). Undoubtedly, the large increase of temperature in the sub-layer of wires drawn in classical die caused the rise of internal stresses related to the thermal expansion of steel. In consequence, it caused the increase of residual stresses.