Mechanical Properties and Transformation Behaviors of Ti-Zr Killed Low-Carbon Steels with High-Temperature Hot-Rolling Process

摘要

The authors describe here the relationship between the microstructure and mechanical properties of Ti-Zr killed low-carbon steels based on hot-rolling experiments and thermo-mechanical simulation. High-temperature hot-rolling and controlled cooling are carried out. Microstructural evolution is studied in quenched steels subjected to hot-rolling simulation. The study suggests that non-metallic inclusions in steel are (Ti, Zr)-rich and are effective in promoting nucleation of acicular ferrite in the recrystallized austenite grains such that the as-rolled microstructure is significantly refined in spite of coarse austenite grain size induced by high-temperature rolling. The addition of boron and accelerated cooling also favored nucleation of acicular ferrite. The tensile strength and low-temperature impact toughness is significantly improved in comparison to the Al-killed steel. The microstructural evolution is divided into two stages including formation of interlocking acicular ferrite structure and coarsening of the ferrite plates with the decomposition of residual austenite.