Effect of thermo-mechanical treatments on residual stresses measured by neutron diffraction in cold-drawn steel rods

Cold-drawing is employed to fabricate wires and rods, which are mainly used as structural reinforcements in construction as well as in the tyre industry. As a consequence of processing, a residual stress profile is developed. The wires are subjected to post-drawing thermo-mechanical treatments with the aim of improving their durability and stress relaxation behaviour. It is claimed that they do so by reducing the residual stresses produced by cold-drawing, although no conclusive data have been given. In this paper, residual stress profiles are measured by neutron diffraction in two cold-drawn pearlitic steel rods subjected to a true strain 1.7: “as-drawn” and “stabilized” (thermo-mechanical treatment). The results show that the post-drawing treatment is very successful in reducing the residual stresses produced by drawing, especially in the surface region of the rods. This explains the improvement of the stress relaxation and stress corrosion behaviour observed in the “stabilized” samples.