Manufacturing an upset end by friction welding in an API X65 steel

Abstract

Deepwater and ultra-deepwater oil and gas exploitation might be challenge due to the fatigue damage at the touchdown zone (TDZ). Therefore, the development of risers with thicker pipe ends (upset end) is a solution to diminish issues related to fatigue through reducing the average axial stress. In the current study, manufacturing of an upset end was carried out by friction welding in an API X65 PLS2 steel pipe with outer diameter of 220 mm. Considering the welding geometry called ‘tube to tube’, pipe sections were machined with different thickness. Thus, in the welding process, the rotational speed was employed in the upset (thicker pipe), while the axial force was applied in the thinner pipe. Hence, this work presents the feasibility of manufacturing an upset end through friction welding and the metallurgical and mechanical properties of the joint. The results showed a suitable welded joint with good top surface appearance and no defects. The samples have not fractured in fatigue tests, which indicate high fatigue life.