Determination of Optimal Recrystallization Annealing Temperature of Nb-Ti Microalloying High Strength IF Steel

The Nb-Ti microalloying high strength IF steel sheet was used to study the effect of annealing temperature on the microstructures,mechanical property and textures.The experimental results showed that experimental steel was incomplete recrystallization when annealing temperature is 750℃,and the recrystallization has finished when annealing temperature was from 780℃ to 870℃ under experimental condition.With the increasing of annealing temperature,the yield strength and tensile strength gradually reduced,and the the plastic strain ratio and yield point elongation gradually increased.The yield strength,tensile strength,elongation percentage,the plastic strain ratio and the strain hardening exponent were approximate 300 MPa,410 MPa,36.5%,1.7 and 0.22 under annealing temperature 810℃ to 840℃.When the annealing temperature was increased,the α textures and γ textures were gradually weakened,and the α textures have a trend of close to texture {111}.Therefore,the suggested optimal recrystallization annealing temperature of industrial production is 810℃ to 840℃.