Hot Ductility Analysis and Flow Stress Prediction of (C-Mn-S-Al-Nb-V-Ti) Micro-alloyed Steel

Abstract

The objective of this work is to study the hot ductility of (C-Mn-S-Al-Nb-V-Ti) micro-alloy steel of industrial production whose initial structural state is rolling stock. To simulate the thermomechanical treatments imposed we have deformed by pulling our samples after subjecting them to a solution treatment at 1200 °C and a precipitation treatment cycle before deformation. Hot deformations were carried out at temperatures from 700 °C and 1150 °C and deformation rates ranging between 10-2 s-1 and 5.10-4 s-1. The results show a decrease in hot ductility. Minimum values of hot ductility are determined at 800°C, and another decrease in hot ductility was observed at 900°C. Ferrite precipitation is observed at austenitic grain boundaries in the intercritical temperature range, causing intergranular embrittlement. Precipitation makes the hot ductility curve wider and deeper around 900°C. Hot ductility losses can explain by the presence of precipitates in the austenitic region and the presence of the two-phase structure in the intercritical region. Finally, based on experimental stress-deformation data, artificial neuron network (ANN) methods were used to predict flow stress of (C-Mn-S-Al-Nb-V-Ti) micro-alloy steel. This model is more effective in predicting flow stress and results can also be used in the mathematical simulation of hot metal formation processes.