Papers by Keyword: Ti Microalloyed Steel

Abstract: In recent years, the ultra-fast cooling process is a new technology used to control the strip cooling process in the international which corresponds to an average cooling rate higher than 150°C/s. This new technology can provide an effective means to the development of low-cost and high-performance steels. In this paper, the phase transformation temperatures, microstructures and mechanical properties of a Ti microalloyed steel were investigated by means of a themomechanical simulator and a D450mm mill equipped with ultra-fast cooling device. The results show that the phase transition temperatures decreased and micro-hardness increased with the increasing of cooling rate. The microstructures of steel used ultra-fast cooling process was small and more uniform than the ones used laminar flow cooling and air cooling process, and finer and uniformity dispersed precipitates can be produced under ultra-fast cooling process, hence higher yield strength and good elongation was obtained for the steel. The ultra-fast cooling technology has a good effect on the microstructures and properties of the Ti microalloyed steel.

Abstract: Hot rolled Ti microalloyed steel with polygonal ferrite and granular bainite microstructure and 640 MPa yield strength has been developed in BOF-CSP process. By chemical phase analysis, XRD, EDS and high resolution TEM, the particle size distribution, morphology, composition, crystal structure of precipitates were identified. Results revealed the steel containing Ti exhibits fine and uniformly distributed Fe3C-type carbides, the amount of M3C particles less than 18 nm in size was 0.2565 mass %. The high strength of steel is attributed to the precipitation strengthening effect of Fe3C, the yield strength increment from precipitation strengthening of Fe3C calculated according to the formula by Olson and Ashby-Orowan attained 234.4 MPa.

Abstract: This study analyzes the recrystallization behaviour of Ti microalloyed low carbon steels processed by near net shape technology. Faster solidification rates associated with this technology allows for a finer precipitation of TiN particles that are very effective in controlling austenite grain growth during hot working. Furthermore, these small precipitates are shown to be able to retard ecrystallization compared to the kinetics of a plain carbon steel.