Comparing the Hot Ductility Behaviour of Low-Carbon Microalloyed Nb-V-Ti Steels During Two Thermal Cycling Routes: Solutionizing and Precipitation Treatments

摘要

The hot ductility behavior of commercial low-carbon microalloyed Nb-V-Ti-steel was studied in both wrought and cast conditions by means of hot tensile tests over a wide range of temperature (750-1200 degrees C) and at three strain rates (0.01, 0.002 and, 0.0005 s(-1)). To replicate the straightening operation undergone by the two materials during hot drawing of plates and continuous casting process, respectively, two kinds of thermal cycles, namely solutionizing and precipitation treatments, were adopted to compare their respective influence on the formation of surface cracking. After deformation, the lowest ductility values were found at 900 degrees C in the single -domain for the as rolled material in the former treatment, and at 800 degrees C in the two-phase domain for the as cast product in the second one. By contrast, the largest values were observed at 750 degrees C and above 1000 degrees C for the two examined materials in both types of treatment. On the whole, surface cracking was found as a result of grain boundary sliding which was acknowledged as the main fracture mechanism. An attempt was also made to determine a relationship between the synergistic effect of the various intervening micromechanisms and the resulting embrittlement.