Papers by Keyword: Thermo-Mechanical Controlled Processing

Abstract: A low-carbon, titanium and niobium (Ti-Nb) bearing and a low-carbon titanium, niobium and copper (Ti-Nb-Cu) bearing ultra high strength steel have been thermo-mechanically processed on a laboratory scale unit. Evolution of microstructure and mechanical properties of the above air cooled steels have been studied at different finish rolling temperatures (FRTs). Microstructural characterization reveals largely a mixture of granular bainite and bainitic ferrite along with the precipitation of microalloying carbide/carbonitride particles and/or Cu-rich precipitates. (Ti-Nb) bearing steel yields higher yield strength (1114-1143 MPa) along with higher tensile strength (1591-1688 MPa) and moderate ductility (12-13%) as compared to (Ti-Nb-Cu) bearing steel having yield strength (934-996 MPa) combined with tensile strength (1434-1464 MPa) and similar ductility (13%) for the selected range of 850-750°C FRT. Due to higher strength-ductility combinations, these present investigated steels can be regarded as the replacement material for ballistic applications as well as other sectors like defense, pipeline, cars, pressure vessels, ships, offshore platforms, aircraft undercarriages and rocket motor casings etc. Key words: Thermo-mechanical controlled processing, ultra high strength steel, microstructure, mechanical properties.

Abstract: Thermomechanical controlled processing of concrete reinforcement bars, comprising quenching and autotempering, produces a microstructural gradient across the diameter - tempered martensite near to the surface, bainite and/or degenerated pearlite in the intermediate layers and pearlite-ferrite within the core. Since martensite is the strength controlling phase in steels, its fractional thickness in TMCP bars have beeen correlated to tensile properties. The developed empirical model, helped in revealing that upto a fractional rim of about 20%, volume fraction of ferrite-pearlite predominantly influenced the YS, UTS and % elongation, whereas at higher fractions, martensite found to control these properties.