Effect of Niobium on Dynamic Recrystallization Behavior of 5%Ni Steel

The single-pass hot compressions of two 5%Ni steels with and without niobium addition at different temperatures of 800-1150 degrees C and strain rates of 0.01-1 s(-1) were performed by using a Gleeble-3500 thermal simulator and the effect of niobium on the dynamic recrystallization (DRX) behavior was analyzed. The results showed that the niobium addition of 0.04% can retard DRX in 5%Ni steel significantly by increasing the activation energy for DRX from 394 to 462 kJ/mol. The critical strain required for starting DRX in 5%Ni steel was increased by 0.04-0.10 with niobium addition when the steel was deformed at a strain rate of 0.01 s(-1) and temperatures varied from 950 to 1 000 degrees C. The critical temperature required for starting DRX in 5%Ni steel was also increased from 1 000 to 1 050 degrees C with niobium addition when the steel was deformed at a strain rate of 0.1 s(-1). Such a retarded DRX occurring in Nb-added 5%Ni steel can be attributed to the pinning effect of precipitates containing niobium.