Effect of Reheating and End Cooling Temperature on Microstructure Refinement in a Low Carbon High Strength Nb-Ti Microalloyed Dual Phase Steel
In this study, a TMCP was attempted to obtain a low carbon high strength Nb-Ti microalloyed dual phase with low yield ratio at Baosteel. Optical and scanning electron microscopy was utilized to analyze microstructures. A mixed fine microstructures consisting of acicular ferrite and martensite/austenite was observed. The austenite maintained a small grain size during reheating in the temperatures ranging from 1100°C to 1250°C. The growth of austenite was strongly retarded by Nb and Ti nitride and carbide. The higher end cooling temperature (650°C) had much influence on the refinement of microstructures, especially the length of ferrite packets, whereas the lower temperatures (600-500°C) had little effect on the microstructure refinement.
Young Won Chang, Nack J. Kim and Chong Soo Lee
L.D. Yao et al., "Effect of Reheating and End Cooling Temperature on Microstructure Refinement in a Low Carbon High Strength Nb-Ti Microalloyed Dual Phase Steel", Materials Science Forum, Vols. 561-565, pp. 49-52, 2007