Welding rod arc welding of pipeline: welding rod arc welding of pipeline is the most commonly used welding method in general factories at present. It is a method of manually melting pipe wall and welding rod, mixing to form molten pool and solidification to form weld. The electrode arc welding equipment is simple, flexible and easy to apply. It is suitable for the welding of small-diameter pipes, thin-wall pipes and narrow pipes. Electrode arc welding can be applied to any space and position.
Rotary welding of pipeline: when processing pipeline in prefabrication plant, rotary welding is generally adopted, which has simple operation and high productivity. Pipe welding quality is closely related to butt welding and spot welding.
Pipe butt welding and tack welding: the specification of pipe butt welding shall comply with the relevant standards of national enterprises. At the same time, the flatness of the groove end face shall be less than 0.5mm, and the joint assembly dislocation shall not be more than 1mm. For small-diameter pipes, it is only necessary to conduct tack welding on both symmetrical sides of the pipe. For large diameter pipes, three or more welding spots can be spot welded, and the size of the spot welding spot shall be determined. When the pipe wall thickness is less than or equal to 5mm, the thickness of the welding spot is 2.5-3mm. If the pipe wall thickness is greater than 5mm, the thickness of the welding spot is about 4-5mm, and the length of the spot welding is about 20-30mm. In order to facilitate the penetration of the joint, both ends of the welding spot must be made into a gentle slope shape.
Root welding: rotary welding of pipes without gaskets. In order to make the root easy to penetrate, the strip transportation range shall be selected at the vertical welding position. The operation method can be linear or slightly swinging crescent. If the gap between butt joints is large, arc extinguishing method can be used for welding. For thick walled pipes, sometimes the rotation is very laborious. At the same time, in order to prevent cracks at the root of the joint due to vibration during rotation and facilitate operation, the pipe shall be placed on a flat rotating table before docking. When welding, it is better to weld before turning once. At the same time, the weld must have sufficient strength, and the distance between two fulcrums close to the joint shall not exceed 1.5-2 times of the pipe diameter.
