K K RAKESHA
Articles written in Sadhana
Volume 47 All articles Published: 15 October 2022 Article ID 0206
Strips of micro-alloyed steel grade 27MnSiVS6 was subjected to austenitization, followed by forced air cooling and austempering conditions. The forced air cooled condition resulted in a tensile strength of 1345 MPa and 13.5% elongation with an yield ratio of 0.41, with a microstructure consisting of ferrite, bainite with blocky martensite/austenite (M/A) constituent. The same steel was subjected to austenitization at 950 °C for 10 min followed by austempering in a salt bath at 450 °C for 5 min, showed a fully bainitic ferrite microstructure with very fine M/A constituents, where a tensile strength of 969 MPa and an elongation of 16.8% and an yield ratio of 0.82 were noticed. During austempering, the holding time at the austenitization temperature and isothermal temperature were varied which resulted in a moderate influence on the strength and the ductility. The work hardening behavior of the steel was examined using the Hollomon equation and modified C–J (Cussard–Jeoul) analysis. The work hardening initially takes place in the softer ferrite phase, which is beyond acritical strain, changes over to harder tempered martensite phases followed by void nucleation and failure. The study establishes a new range of mechanical properties in the micro-alloyed steel that can be used in flat products.