In this paper, the improvement of vertical down welding in piping is introduced and the technology of mixed vertical downwards welding and co - operated vertical down welding are described .

• 介绍了手工向下焊焊接工艺在长输管道焊接方面的发展,主要叙述了混合型向下焊焊接工艺和复合型向下焊焊接工艺的应用。