Compound is backing down welding ,welding electrodes and heat welding are used in the welding to the welding method, welding and capping fill up welding method using the welding process. The wall thickness is mainly used in welding large pipes.
The decade of the 20th century 90 large wall thickness of pipe is widely used in domestic and international oil, gas and water industry in the long-distance pipelines, water pipelines in the industry, the pressure above the normal diameter of 1m, the wall thickness of 10 ~ 60mm, in northern China cold regions oil and gas pipeline wall thickness of 10 ~ 24mm. Compared with the traditional upward welding, welding heat input to the next low penetration shallow weld thin steel tube wall thickness increases with the number of layers also increased rapidly weld, welding time and labor intensity become larger , simply difficult to play under its welding to the welding speed and high efficiency. Manual arc welding of steel pipe(Stainless Steel Electrode) when the level of different thickness and the channel number in Table 2. The backing welding, thermal welding with the next to the welding, welding and capping fill up the welding of the compound with the next two to welding technology can play the advantages of welding methods to achieve quality and efficient results. Under the semi-automatic gas shielded welding technology to the pipeline construction is not used before, a large wall thickness under the pipe to use more complex welding

Technologies. If an industrial park works with a steel water pipeline specifications for φ400mm × 14mm, material is Q235-A. Weld backing during welding, heat welding cellulosic electrodes J425G, fill welding and capping the ordinary J422 (E4303) electrode, the weld bead layer welded by a single click to the desired level was reduced to 7 to8 4 to 5 layers, welding time can be shortened 30min, greatly improving production efficiency.

Keywords: welding electrode material