Properties of pipeline steel subjected to long-term holding under constant load

Changes of structure and properties of the normalized pipeline steel 09G2S are studied after constant loading at 0.75 of the yield stress for up to 10 years. It is found that in the first five years of loading the strain aging develops in the steel causing significant changes of physical properties and increase of ductile-brittle transition temperature. On further loading the processes of strain aging are stabilized and their rate decreases, as can be seen from the measurement of physical properties and the character of substructure.