On the strengthening mechanisms of a Fe-0.2% C-0.6% Mn-0.2% Mo-1.0% Cr steel intended for pipelines applications.

Abstract

High-strength low-alloy (HSLA) steels are still of great importance for different areas of engineering, such as in applications that include automotive, building, and pipeline industries. In the present work, steel intended for pipeline applications, Fe-0.2%C-0.6%Mn-0.3%Mo-1%Cr, was induction melted and hot-rolled (HR) from 1250 °C to 870 °C achieving 63 % of total deformation. After thermomechanical treatment, the alloy was processed via two different routes: (1) water-quench + temper (HR+WQ+T), and (2) air-cooled to room temperature (HR+AC). Microstructure in both conditions exhibited the following mechanical properties: 0.2 % yield strength (YS) = ~ 980 MPa, ultimate tensile strength (UTS) = ~ 1050 MPa and Elongation (El.) = ~ 32 %; and 0.2 % (YS) = ~ 880 MPa, (UTS) = ~ 920 MPa, (El.) = ~ 36 %, respectively. Due to the relevance of the yield strength value related to the proposed application, predictions using linear and square root equations were performed. In this respect, different strengthening mechanisms were considered. The linear equation showed a good agreement with the experimental values. Finally, the mechanical properties of the steel understudy positioned it as HSLA-120 steel.