During cold drawing, the microstructure and mechanical properties of steel wire change, resulting in work hardening. With increasing cold deformation, the tensile strength, hardness, and elastic limit of the steel wire generally increase, while elongation and reduction of area decrease. Due to work hardening, once the degree of deformation reaches a certain value, the cold workability of the steel wire significantly decreases, making further drawing unsuitable. Intermediate heat treatment is required to restore its machinability; this process is called annealing.
Annealing aims to modify the internal molecular structure of a metal wire by slowly heating it to a certain temperature, holding it for a sufficient time, and then cooling it at a suitable rate. The purpose is to reduce hardness, improve machinability, eliminate residual stress, stabilize dimensions, reduce deformation and cracking tendency, refine grains, adjust the microstructure, and eliminate structural defects.
In short, annealing reduces the internal molecular structure of the metal wire to prepare it for redrawing.
The annealing process: The drawn low-carbon steel wire or stainless steel wire is placed in an annealing pot or furnace, heated to a suitable temperature, and then slowly cooled. After removal, the annealing process is complete. Wire that has undergone annealing is called annealed wire.
