The technological principle of the equipment used for RMD semi-automatic root welding, the technological features of new type welding materials and the application of RMD root welding technique in X80 pipe steel are describes.

This paper introduces the technology principle and characteristic,new welding material of equipment used by RMD semi-automatic root welding technique,and application of RMD root welding technique for X80 alloy steel pipeline welding.

This paper mainly discusses the technical characteristic of some important root welding technology, such as STT semiautomatic root welding, inner automatic root welding and external automatic root welding.

Application of flux cored wire semiautomatic welding in the long distance transmission pipeline;

The welding technology, practical application on long distance transportation pipeline and characteristics of the semiautomatic welding with self-shielded flux cored wire were simply summarized.

Application of semi-automatic welding about the western pipline engineering;

Detailed analysis of the use of semi-automatic welding torch,notices,troubles and solutions in maintenance of welding torch.

This paper describes a self-shielded flux-cored wire semi-automatic welding technology applying in the large wall thickness of small diameter pipeline welding,the defects of the technology and related factors of the welding quality.