EFFECT OF FERRITE CRYSTALS PLASTIC ANISOTROPY ON RESIDUAL-STRESSES INCOLD-DRAWN STEEL WIRE

The effect of plastic anisotropy of the BCC lattice on residual stress es was analyzed for the case of severely cold-drawn steel wire. Accord ing to the analysis, lateral stresses develop inside individual crysta llites of ferrite resulting from the plastic anisotropy, the compatibi lity 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 th e [001] axis and the compressive stress along the [1(1) over bar0$] ax is. Only these stresses, referred to as mesostresses, cause non-linear ity of the interplanar spacing dependencies on sin(2) psi, where psi i s the angle between reflecting planes and the wire specimen surface. S uch 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-r ay ''sin(2) psi technique''. The model suggested in this work enables one to estimate the macrostresses acting on the scale of the wire as w ell as the mesostresses acting on the scale of the individual crystall ites. For the cold-drawn 0.7% C steel wire the mesostress level is abo ut 300 MPa. The approach used in this work can be applied to the resid ual stress analysis of other materials and methods of cold-metal worki ng.