Abstract: After the establishment of the PipeChina Group, it is clearly required that welding of pipeline with steel grade of X70 and above should adopt automatic welding. Hence automatic welding of domestic longdistance pipelines has been promoted comprehensively. With the large-scale applications of internal pipeline automatic root welding technology, its technical weaknesses have gradually emerged. And the external pipeline automatic root welding technology can overcome these weaknesses. It has unique technical advantages and is worthy of in-depth research. Through the analysis and research of the automatic root welding equipment and root welding technology at home and abroad, the basic theories and key technical points of pipeline automatic root welding technology have been mastered. Through actual welding tests, it is proved that the external automatic root welding has good welding quality, high efficiency and wide scope of application. It is worthy of further promotion and use in long-distance pipeline projects.

Key words: pipeline, external automatic root welding, equipment, welding technology