مشخصات پژوهش

In this study, the effects of open-die cold forging on corrosion behavior of pressure vessel sheet (A516 GR70) were investigated. To reduce the effect of the spring back a die with high radius was used and three passes were selected and employed. The variations in the microstructure, mechanical properties and corrosion behavior of the sheets were investigated after each pass. Microstructural analysis showed a strong anisotropy of rolling grains due to the fact that the orientation of the first grains change greatly by performing the pressing process. By increasing the number of passes, the orientation of the grains become more uniform and this produce a consequent enhancement of mechanical properties. In detail, due to the Bauschinger effect, the tensile strength and yield stress and hardness are reduced to 331 MPa and 155 HB at the first step of the pressing process, respectively. In the following steps, the mechanical properties such as tensile strength are increased by repeating the pressing process in 2 and 3 passes up to 520 and 528 MPa, respectively. Electrochemical Impedance Spectroscopy and potentiodynamic polarization tests evidence that forging process has a positive effect on the corrosion resistance. The highest corrosion resistance was obtained by forging after 3 passes.