Microstructure evolution and precipitation behavior of hot-rolled high-strength Ti–Mo–V micro-alloyed steel

Abstract

The microstructure evolution and precipitation behavior of hot-rolled Ti–Mo–V micro-alloyed high-strength steel processed at different final rolling temperatures (FRT) and coiling temperatures (CT) were investigated. The results indicated that the decrease of FRT (880 °C–820 °C) promoted the ferrite refinement and strain-induced precipitation in austenite, but it also led to the decrease of pearlite content, which finally led to a slight difference in properties, and CT obviously changed the phase component, grain size, and precipitation behavior. Appropriate reduction of the CT (650 °C–600 °C) could promote the precipitation of (Ti, Mo, V)C and refine ferrite grains, thus improving strength. As the CT further lowered to 550 °C, the precipitation hardening effect would be seriously lessened owing to the significant reduction of (Ti, Mo, V)C volume fraction, finally resulting in the loss of strength. The optimum mechanical properties were attained for the FRT850-CT600 sample, and the ultimate tensile strength (UTS), yield strength (YS), and total elongation (TE) were 908 MPa, 848 MPa, and 21.5 %, respectively, with precipitation hardening up to 383.51 MPa.