Effect of Cooling Rate on Phase Transformation Kinetics and Microstructure of Nb–Ti Microalloyed Low Carbon HSLA Steel

Nb–Ti microalloyed low carbon high strength alloy (HSLA) steels are used to fabricate components, particularly for the automobile and piping applications requiring optimum combination of mechanical properties along with good weldability. These depend on transformed ferrite microstructure grain size obtained after cooling from hot rolling temperatures which always well above austenitizing temperature. Hence, an attempt was made study austenite decomposition (phase transformation) kinetics accompanying microstructural evolution in steel by subjecting it austenitization at 1100 °C 3 min followed different rates ranging 1 100 °C/sec a B $$\ddot{a}$$ hr DIL 805 A/D dilatometer. The first derivative method employed identify critical transformation dilation curves. A modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis (used non-isothermal conditions) carried out find time exponent (n’) values controlling rate rates. nature observed change polygonal acicular type, its found decrease increase rate. EBSD also revealed have profound effect microtexture concerned alloy. “ $$\gamma$$ ” fibre rotated cube components replaced copper (“ $$\alpha$$ fibre) owing faster lack recrystallization $$\alpha $$ Finally, power law logarithmic relationship microhardness applied were established.