Influence of phosphorous and boron on dynamic recrystallization and microstructures of hot-rolled interstitial free steel

Abstract

This paper examines the effects of phosphorous (P) and boron (B) of Nb–Ti added interstitial free (IF) steel on dynamic recrystallization, mechanical properties and microstructures. For this purpose, four Nb–Ti added IF steels that contain different contents of P and B were selected. The dynamic recrystallization behavior was investigated using hot compression testing. Mechanical properties and microstructures of pilot hot-rolled IF steel sheet were analyzed as well using uni-axial tensile test and electron back-scattered diffraction (EBSD) following pilot hot rolling experiment. It has been found that B strongly retarded dynamic recrystallization of the IF steel in the temperature range of 900–1100 °C. However, P did not delay dynamic recrystallization at 1100 °C. The effect of P on dynamic recrystallization was less than that of B. EBSD analysis revealed that absence of P and B induced fine ferrite grain size and many high angle grain boundaries. The ferrite grain size of P and B free IF steel was 46.4% smaller than that of IF steel having 0.1% of P and 0.001% of B.