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Published online by Cambridge University Press: 20 December 2012
This work study the effect on aging thermal treatment on micro-alloyed steels API X70 pipe, microstructure and mechanical properties such a yield strength (Y), hardness (Hv) and Young´s modulus (E) are presented in this work. Thermal treatment consists of two phases: i) The solution treatment introducing samples in a electric induction furnace at 1100 °C for 30 min under argon atmosphere and water quenching, ii) aging process for five temperature in the range between 204 to 650 °C for 30 min of time exposition and water quenching, respectively. The microstructural characterization was examined by optical microscopy and matrix samples aging showed microstructures like acicular ferritic, polygonal ferritic and bainitic-ferritic, and the secondary phases were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) obtained by SEM evidencing the presence of precipitates composed of vanadium (V), niobium (Nb) and titanium (Ti). The mechanical properties were evaluated by depth sensitive indentation test at the samples aging, the results showed increase of the (Hv) and (E)to the conditions of low temperature aging.