Abstract:

Temper rolling, as a final manufacturing procedure, brings the change of surface features and hence affects the corrosion behaviors of interstitial-free (IF) steel. This study investigates changes in residual stress, microstructure, and surface topography of IF steel using X-ray diffraction, electron backscatter diffraction, and optical interferometric microscopy. And the synthetic influence of surface features on the corrosion process of the steel was evaluated by damp heat tests and electrochemical measurements. Results showed that low tensile and compressive residual stresses are introduced to the surface of the IF steel. Some grains had a grain orientation spread (GOS) value greater than 0.5^° after temper rolling. Moreover, temper rolling caused a slight change in the surface profile of the IF steel. The compressive residual stress had an overwhelming role at the macroscopic level, in retarding the corrosion evolution process of IF steel, as well as in decreasing the average corrosion rate. And corrosion was more likely to initiate and propagate in matrices with a high GOS value, which played the determinant role at the microscopic level. Moreover, the depth of valley in the surface profile could affect the diffusion process involved in the electrode reactions, which was more likely to exert an extra influence on the corrosion rate of IF steel.

Key words: Temper rolling, Surface feature, Corrosion behavior, Interstitial-free steel