Welded joint properties of X60 pipeline steel at -20℃

In accordance with the site construction of X60 pipeline steel at -20℃,the mechanical properties,metallograpic structure,hardness,Charpy impact absorbing energy and the fracture structure of the girth welded joints of φ711×15.9 mm pipeline are analyzed.The results show that the highest HAZ hardness value of the X60 pipe steel joints girth-welding at -20℃ cryo-welding is 210 HV10 which meets related standards.The welding procedure specification has been used on the long-distance pipeline projects in China's northern area,which obtains satisfactory results:no hardened structures in the joints through metallurgical microscopic observation and the toughness of the joints meeting the requirement of related technical standards through microscopic observation of the cross section of the Charpy test sample.