Effect of ferrite crystals' plastic anisotropy on residual stresses in cold-drawn steel wire

Abstract

The effect of plastic anisotropy of the BCC lattice on residual stresses was analyzed for the case of severely cold-drawn steel wire. According to the analysis, lateral stresses develop inside individual crystallites of ferrite resulting from the plastic anisotropy, the compatibility requirements at the crystallite boundaries, and the strong 〈110〉 axial texture. It was shown that in a crystallite with the [110] axis parallel to the drawing direction, the tensile stress appears along the [001] axis and the compressive stress along the [1 1 0] axis. Only these stresses, referred to as mesostresses, cause non-linearity of the interplanar spacing dependencies on sin 2ψ, where ψ is the angle between reflecting planes and the wire specimen surface. Such non-linearity, observed in the case of cold-drawn steel wire, does not allow one to estimate residual stresses by means of the usual X-ray “sin 2ψ technique”. The model suggested in this work enables one to estimate the macrostresses acting on the scale of the wire as well as the mesostresses acting on the scale of the individual crystallites. For the cold-drawn 0.7% C steel wire the mesostress level is about 300 MPa. The approach used in this work can be applied to the residual stress analysis of other materials and methods of cold-metal working.