The relationship between niobium content and austenite grain growth hasbeen investigated through hot rolling simulation on a Bähr dilatometer.The effect of delay time between passes during rough rolling in Nbmicroalloyedsteels with nitrogen contents typical for electric arc furnace(EAF) melting was studied. The results indicate that the grain growthconstants n, Q, and A increase with an increase in Nb content. Theactivation energy for austenite grain growth Q was found to be in therange of 239 to 572 kJ/mol, the exponential constant n ranged from 2.8 to6.2, and the material and processing condition constant A from 4.24 × 1012to 4.96 × 1028, for steels with niobium contents ranging from 0.002% Nb to0.1% Nb. A general constitutive equation for the prediction of austenitegrain growth in these Nb-microalloyed steels under rough rollingconditions has been developed. Good agreement between the experimentaland the predicted values was achieved with this constitutive equation.
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