Effect of Vanadium and Strain Rate on Hot Ductility of Low-Carbon Microalloyed Steels

Hot tensile tests were conducted in this study to investigate the effect of strain rate (10(-3) and 10 s(-1)) and vanadium content (0.029 and 0.047 wt.%) on the hot ductility of low-carbon microalloyed steels. The results indicate that a hot ductility trough appears at a low strain rate (10(-3) s(-1)) because of the sufficient time for ferrite transformation and the growth of second particles, but it disappears at a high strain rate (10 s(-1)). The hot ductility is improved with the increase in strain rate at 700 degrees C or higher temperatures. In addition, with the increase in vanadium content, the large amounts of precipitate and increased ferrite transformation result in poor hot ductility of steels fractured at a low temperature range (600~900 degrees C). However, when the steel is fractured at a high temperature range (1000~1200 degrees C), more vanadium in the solid solution in the austenite inhibits the growth of parental austenite grains and results in grain refinement strengthening, slightly improving the hot ductility.