Effect of Coiling Temperature on the Hardening Mechanisms of a High-Ti Steel

摘要

In recent years, steels microalloyed with high Ti levels have received increasing attention due to the interesting combination of high strength and formability because of the dispersion of nanometric sized titanium carbides that can be formed within the matrix. However, one of the problems related to these compositions is that their performance can be highly sensitive to variations in the processing route. To study this, in this work coiling simulations were performed by dilatometry tests with a reference Nb microalloyed steel (0.03%Nb) and a high-Ti steel (0.03%Nb-0.1%Ti) using temperatures from 550 to 675oC. The mechanical behaviour of the samples was characterized using Vickers hardness. A large hardness increase was observed in the high-Ti steel samples, resulting in estimated yield strength increases between 69 and 214 MPa. This improvement in the mechanical behaviour was very dependent on the coiling temperature; the maximum hardness was observed at 625oC-650oC, while this decreased drastically for temperatures from 550oC to 600oC and at 675oC. EBSD and TEM analysis has been performed to study the contribution of microstructural constituents and precipitation to the observed mechanical behaviour.