Under the composite primer to Welding Electrode is welding and thermal welding under the welding method used, filling and cover pass welding welding method using the welding process up. Its mainly used in welding the pipe wall thickness greater.

Period of the 1990s is not large pipe wall thickness is widely used in domestic and international oil, gas and water industry in the long-distance pipelines, water pipelines in the general industrial pressure up to more than 1m diameter, wall thickness of 10 ~ 60mm, in northern China cold regions oil and gas pipeline wall thickness of 10 ~ 24mm. Compared with traditional welding up, because next to the welding heat input is low, shallow penetration, thinner weld, pipe wall thickness increases with the number of layers is also increasing rapidly weld, welding time and labor intensity will be increased , next to the weld is difficult to simply play the welding speed, high efficiency characteristics. Manual arc welding of steel pipe wall thickness at different levels and number of channels shown in Table 2. The backing welding, heat welding used to weld the next, filling and cover pass welding using welding up next to the welding of complex technologies can play the advantages of two kinds of welding methods to achieve high quality and efficient results. In the semi-automatic gas shielded welding technology is not applied to the next pipeline construction before the big wall pipe to use more complex next to the welding technology. Industrial Park as a water pipe used in pipeline project specifications φ400mm × 14mm, material is Q235-A. Weld backing during welding, Aluminum Electrode with cellulose electrodes J425G, filling and cover pass welding using ordinary J422 (E4303) electrode, the weld bead layer welded by a single bit to the required level reduced to 7-8 4 to 5 layers, welding time can be shortened 30min, greatly improving production efficiency.