The effect of annealing process on the microstructures and properties of 2 000 MPa cold-drawn steel wire

Annealing was used to simulate the galvanizing process of a kind of cold drawn steel wire, and the changes in the structure and properties of the cold drawn steel wire during the galvanizing process were studied utilizing a scanning electron microscope, transmission electron microscope, combined with conventional mechanical testing methods in this paper. The test results showed that the annealing time affected the steel wire′s microstructure and mechanical properties. With the extension of annealing time, the strength of cold drawn steel wire fluctuated first and then decreased significantly subsequently. Meanwhile, the torsional property showed a trend of decreasing first and then rising, and the stage of strength rising was consistent with the stage of significant deterioration of its torsional property. In addition, the surface structure of the steel wire firstly degenerated, the lamellar cementite breaks, forming cementite particles, and the internal dislocation density in the ferrite decreased, while the internal structure of the steel wire could maintain a relatively complete pearlite lamellar structure; after a long time of heat treatment, the surface and internal pearlite lamellar structures all degenerated. The severe deterioration of the torsional properties of cold drawn steel wire in the process of galvanizing was the surface structure inconsistent with the internal structure, and the surface strength was high, causing the deformation was the largest in the torsion process. As a result, stress concentration rapidly deteriorated the torsional performance.