Recent development status of high strength linepipe steels for sour service

POSCO is involved in efforts to produce superior linepipe steels for sour service and to develop high strength linepipe steels for sour service. Several experimental trials involving multiple process variables have been performed to enhance the mechanical properties and HIC/SSC resistance of high strength linepipe steels. Results after ERW pipe forming of API X80 hot strip show that an increase in the t/D ratio increases the sensitivity to hydrogen cracking mechanisms, such as HIC. The increased dislocation density resulting from pipe forming can increase the diffusible hydrogen content. This paper summarizes the effect of pipe forming on the sour resistance of high strength linepipe steels. (AU) © CBMM