摘要
With the progress in the field of manufacturing, welded pipes have been gradually replacing seamless pipes and have become the mainstream in the development of pipe and tube technologies. During the 1970s and the 1980s, the second substitution climax in the markets of western countries occurred with the massive replacement of seamless oil country tubular goods （OCTG） by welded ones. Nowadays, almost all linepipes in western countries have been replaced by welded pipes, and most casing pipes in OCTG are welded, too.
With the progress in the field of manufacturing, welded pipes have been gradually replacing seamless pipes and have become the mainstream in the development of pipe and tube technologies. During the 1970s and the 1980s, the second substitution climax in the markets of western countries occurred with the massive replacement of seamless oil country tubular goods （OCTG） by welded ones. Nowadays, almost all linepipes in western countries have been replaced by welded pipes, and most casing pipes in OCTG are welded, too.
