| Multistage torsion tests in the range of 1200∼750℃, 3.78×10^(-1)∼5.00/sec were performed to study rolling simulation of a V-microalloyed steel with declining temperature T, constant and varying strain rate ε, and constant pass strain ε₁. The dependence of the flow stress on temperature, strain rate, and holding time was examined. On each pass of multistage simulation, the flow stress could be calculated from the relation with 1n ε vs. 1n σ. The dependence of the strain rate on flow stress and temperature in this multistage deformation followed a power-law, ε=A σⁿ exp(-Q/RT), which is similar to cantinuous deformation. The microstructure was observed with optical microscopy and STEM after testing, exhibited grain refinement with progressing the process and reducing finish-rolling temperature. As the finish-rolling temperatures decrease, the vanadium carbide precipitates play an important role in the strength of a V-microalloyed steel. |
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