Study of Mechanical Properties and Structure of Steel C70D After Drawing Deformation and Spheroidizing Annealing

The effect of plastic deformation of steel C70D and different modes of spheroidizing annealing after drawing on the mechanical properties and microstructure is studied. The suitability of the wire for certification to meet the special requirements of the user is assessed. After experimental fivefold drawing of the wire with diameter 3.7 mm and processing of the data of the mechanical tests, a reliable linear regression equation is obtained for determining the change in the tensile strength (σ_r) of the wire as a function of the total reduction, which makes it possible to estimate the hardening factor of the wire material. To reduce the strength of the cold-drawn wire to the demanded values of σ_r ≤ 650 MPa, the spheroidizing annealing mode is selected to be 710°C for 6 h, which provides the required grade of granular pearlite in the steel structure according to TU 14-178-110–89.