Development of Ti–V–Mo Complex Microalloyed Hot-Rolled 900-MPa-Grade High-Strength Steel

Abstract

A new Ti–V–Mo complex microalloyed hot-rolled high-strength steel sheet was developed by controlling a thermo-mechanical controlled processing (TMCP) schedule, in particular with variants in coiling temperature. The effects of coiling temperature (CT) on various hardening mechanisms and mechanical properties of Ti–V–Mo complex microalloyed high-strength low-alloy steels were investigated. The results revealed that the steels are mainly strengthened by a combined effect of ferrite grain refinement hardening and precipitation hardening. The variation in simulated coiling temperature causes a significant difference in strength, which is mainly attributed to different precipitation hardening increment contributions. When the CT is 600 °C, the experimental steel has the best mechanical properties: ultimate tensile strength (UTS) 1000 MPa, yield strength (YS) 955 MPa and elongation (EL) 17%. Moreover, about 82 wt% of the total precipitates are nano-sized carbide particles with diameter of 1–10 nm, which is randomly dispersed in the ferrite matrix. The nano-sized carbide particles led to a strong precipitation hardening increment up to 310 MPa.