Hot ductility behavior of a continuously cast Ti-Nb microalloyed steel

Abstract

The hot ductility behaviour of a Ti-Nb micro alloyed steel was investigated to evaluate the probability of surface crack formation during the continuous casting process, by performing hot tensile tests. The testing temperatures are ranging from 1100 °C to 700 °C. The effects of testing temperature range and deformation rate on hot ductility were investigated. The results show that this steel exhibits poor ductility over almost the whole testing temperature range. The ductility starts to decrease at 1000 °C in the single phase γ-region, characterized by grain boundary sliding and surface cracks, reaches a minimum in the two-phase α-γ-region at 750 °C and slightly increases with decreasing testing temperature. Furthermore, low deformation rates severely decrease the ductility behaviour. Microstructural examinations and supplementary thermo-kinetic computer simulations revealed distinct Ti-Nb precipitation throughout the microstructure being responsible for the deteriorated materials hot ductility.