October 12, 2005 | By Yu.N. Saraev
The welding process and ambient temperature affect the structure and mechanical properties of welded joints in large-diameter (1,420 mm) pipes of manganese low-alloy steels, which are used commonly in oil and gas pipelines. Pulsed welding can improve the homogeneity of the structure and reduce the grain size of metal of the weld and HAZ zones. The ambient temperature causes structural changes, which affect the ductility and impact toughness in the welded joint zones. Temperature plays a role. Research shows that welding at 20 degrees C leads to an increase in ductility and impact toughness of 8 percent to 27 percent, and welding at -60 degrees C leads to an increase of 15 percent to 24 percent.