What is the welding technology of L360NB LSAW pipe?

The welding of L360NB LSAW pipe adopts multi-wire submerged arc welding technology.

Since the core process of L360NB straight seam steel pipe production is welding, especially the LPG steel pipe, which requires high quality and large welding volume. It is required to improve welding efficiency as much as possible while maintaining excellent welding quality. The L360NB LSAW pipe has a large weld length (usually a single length of about 12m) and the weld is in a horizontal position, which has given birth to the application and development of multi-wire submerged arc welding. At present, the number of filaments in the tube industry has grown to 4 to 5 filaments.

Compared with traditional single-wire submerged arc welding, the multi-wire submerged arc welding of L360NB LSAW pipes has the following advantages:

Single wire submerged arc welding due to the small size of the welding pool, low quality, short existence time, and crystallization cooling. Under the welding specifications, the welding speed is limited, generally 300~600mm/min. Too fast welding speed can easily lead to melting The pool is cooled and crystallized to produce welding defects. Too slow speed leads to excessive heat input and widening of the heat-affected zone, which reduces joint performance and low production efficiency. However, multi-wire submerged arc welding is mostly multi-wire longitudinal tandem, forming a shared molten pool during the welding process, and the length of the molten pool can reach more than 80~100mm in three-wire welding. The molten pool has a long existence time and sufficient metallurgical reaction. Ample time for gas and impurities to emerge. The welding quality is good, as long as the process and specifications are well controlled, there are few welding defects. The welding speed can reach above 1.0~2m/min, production. 3~5 times higher than single wire submerged arc welding. The inner and outer welding of products below 30mm can be completed. At the same time, by adopting a reasonable groove form, matching high-toughness welding wire and high-toughness high-speed sintered flux, and reasonable welding process specification parameters, it can meet the quality requirements of welded pipe butt joints. The welding process mainly depends on equipment capabilities and processes, and the skill level of welders is required. Not high, easy to realize mechanized assembly line production.