BRITTLE-FRACTURE OF COLD-WORKED STEEL WITH A FIBROUS STRUCTURE

The brittle fracture of cold drawn steel wire is related to its structural condition, which is characterized by intense loosening as the result of formation of stable microcracks. In this case failure by breaking away must be considered as a normal but alternative variation of brittle fracture. Lamination is an extreme case of brittle behavior of steel in torsion, which is aided not only by strong accumulation of microdiscontinuities and sharply expressed anisotropy but also the increasing influence of residual internal stresses. The tendency of high-strength wire toward lamination may be evaluated in torsion tests from the change in torsional moment and length of the specimens and also from the external appearance of the fracture. A treatment of the drawn wire promoting a reduction in residual microstresses makes it possible to decrease the tendency toward lamination. For example, a short temper under load promotes relaxation of these stresses. © 1990 Plenum Publishing Corporation.