Microstructure, texture, property relationship in thermo-mechanically processed ultra-low carbon microalloyed steel for pipeline application

An ultra-low carbon Ti-containing microalloyed steel has been thermo-mechanically controlled rolled and water-quenched. Microstructural characterization of the samples finish rolled in the temperature range of 750-850 °C revealed the presence of polygonal ferrite, quasi-polygonal ferrite, acicular ferrite and granular bainite. Micro-texture study showed the dominance of random texture and cube orientation at higher deformation temperatures, whilst, α-fiber and γ-fiber components intensified with the decrease in finish rolling temperature. Characteristic ferrite-bainite microstructure with fine ferrite grain size (<4 µm) and a uniform distribution of fine TiC particles (<100 nm) offered decent combination of strength (yield strength: 478-497 MPa, ultimate tensile strength: 557-571 MPa), ductility (total elongation: 20-26%), and impact toughness (110-114 J at −40 °C). Such a combination of mechanical properties makes the steel a potential choice for pipeline application.