UHPM - 95
J. Phys. IV France 05 (1995) C7-347-C7-353
Hot Ductility of a Microalloyed Steel in the Intermediate Temperature RangeA. Darsouni1, B. Bouzabata1 and F. Montheillet2
1 Unity of Research in Metallurgy and Materials, University of Annaba, Algérie
2 Microstructure and Processing Laboratory, URA 1884 du CNRS, S.M.S., Ecole Nationale Supérieure des Mines de Saint Etienne, 42023 Saint-Etienne, France
In this study hot ductility has been determined from tensile tests for two states of a microalloyed steel : after casting and after rolling processes. Hot deformations were carried out at speeds varying from 10-4s-1 to 10-2s-1 and temperatures from 750°C to 1100°C. Two heat treatments were chosen before hot deformation. A ferrite precipitation is observed at austenitic grain boundaries in the intercritical temperature range, causing intergranular embrittlement. Ductility trough is deeper in the as-cast samples due to the growth of large grain size. Also, precipitation makes the hot ductility curve wider and deeper around 900°C. The results show a decrease in hot ductility. Minimum values of hot ductility are determined for (ITC) treatment at 900°C and for (DTC) treatment at 800°C. For this second treatment another decrease in hot ductility was observed at 900°C. We can explain hot ductility losses by the presence of precipitates in the austenitic region and the presence of the two-phase structure in the intercritical region.
© EDP Sciences 1995