The influence of niobium content on austenite grain growth in microalloyed steels

摘要

The relationship between niobium content and austenite grain growth has been investigated through hot rolling simulation on a Bahr dilatoraeter. The effect of delay time between passes during rough rolling in Nb-microalloyed steels with nitrogen contents typical for electric arc furnace (EAF) melting was studied. The results indicate that the grain growth constants n, Q, and A increase with an increase in Nb content. The activation energy for austenite grain growth Q was found to be in the range of 239 to 572 kj/mol, the exponential constant n ranged from 2.8 to 6.2, and the material and processing condition constant A from 4.24 ×10~(12) to 4.96 ×10~(28), for steels with niobium contents ranging from 0.002% Nb to 0.1% Nb. A general constitutive equation for the prediction of austenite grain growth in these Nb-microalloyed steels under rough rolling conditions has been developed. Good agreement between the experimental and the predicted values was achieved with this constitutive equation.