Abstract: A high-temperature viscoplastic constitutive model is the basis of numerical simulation on the deformation behaviors of continuous casting billet in a near-solidification-finishing reduction(NSFR) process. However， the lack of the stress and strain data under this condition extremely limits the development of new continuous casting processes. The rheological behaviors of axle steel under the NSFR and conventional hot deformation processes are studied through thermal simulation experiments. Based on the theory of dynamic recovery and recrystallization， a revised constitutive model in the NSFR process is established. The results show that the austenite grains are coarser and the rheological stress is lower under the NSFR process， compared with those under the conventional one. Under the same reduction， the volume fraction of dynamic recrystallization grain is higher. The predicted stresses from the constitutive model under different conditions are in good agreement with the experimental ones and the average relative error is about 2.62%.

Key words: casting microstructure; high-temperature viscoplastic constitutive model; work hardening; dynamic recrystallization; rheological behavior