Effect of rolling temperature on the microstructure and mechanical properties of interstitial free steel

Abstract

In the present research, to improve the mechanical of interstitial free steel, the hot rolling process has performed for 50% reduction in area at three different phase regions (below the lower critical point, above the upper critical point and intermediate region) of interstitial free steel. Samples were cooled down to room temperature by normal air cooling in the room temperature. The microstructure and mechanical properties of control rolled steel have been investigated by an optical microscope, Vickers hardness tester and tensile test. It has found that yield strength and ultimate tensile strength of sample rolled at a lower critical temperature (600°C) improved significantly without much significant change in ductility, due to ferrite grain refinement and an increase of dislocation density. Scanning electron microscope fractography analysis shows cup and cone fracture. Finally, it is suggested that a controlled rolling process of interstitial free steel in pure ferritic region conferred optimum properties.