Effect of process parameters on the static recrystallisation and precipitation behaviours of V–Ti–N microalloyed steel

Abstract

Hot rolling process often consisting of several successive deformation stages, static recrystallisation and precipitation may occur in microalloyed steels during the inter-pass periods between two stages, which have a great impact on the mechanical properties of the final products. To obtain the products with high performances, the process parameters must be controlled. In this study, static recrystallisation and precipitation in a vanadium titanium microalloyed steel was investigated by double compression method. Especially, the effect of process parameters, such as, temperature, pass time interval, strain and strain rate on the static recrystallisation and precipitation behaviours was discussed in details. The results showed that the static recrystallisation and precipitation behaviours of the tested steel could be affected by the process parameters significantly. At a higher temperature of 950 °C or 900 °C, static recrystallisation fraction increased with increasing time interval, while plateaus could be observed on softening curves due to the vanadium titanium carbonitride precipitated in the tested steel at a lower temperature of 850 °C or 800 °C. In addition, an increase in strain rate or an increase in strain could promote static recrystallisation. Especially, plateaus could not be observed on the softening curves obtained from the tested steel deformed at the strain rate of 1 s−1 and at the temperature of 850 °C or 800 °C. The prohibition on static recrystallisation was not recognisable as a larger strain of 35% was applied at 850 °C but it could still be observed at 800 °C.