Correlation of Rolling Schedules, Mechanical Properties, and SCC Susceptibility of API X70 Steel

Abstract

The effect of thermomechanical rolling schedules on the development of crystallographic texture, mechanical properties, and SCC susceptibility were studied in an API X70 steel. The rolling temperatures and the magnitude of deformations (rough and finish rolling) were highly influential on the development of crystallographic texture and the resulting mechanical properties and SCC performance. Complete rolling above RLT (Tnr) resulted in the formation of large, equiaxed upper bainite and the highest yield strength and ultimate tensile strength. Finish rolling in the two-phase region increased the polygonal ferrite formation and deteriorated mechanical properties of the rolled steels. When finish rolling above the Ar3, an increase in the magnitude of the initial rough rolling deformation increased the proportion of granular bainite within the structure. Optimising the rolling strategy has shown to positively affect SCC performance.