LSAW pipe pre-welding technology

In the pipeline construction, oil and gas long-distance pipeline is toward large-diameter high-pressure transmission and the direction of the development of thick submarine pipeline, a growing number of pipeline requests using LSAW steel pipe. As China's few through-submerged arc welded pipe production line put into the introduction, to grasp the advanced welding technology LSAW is especially key.

1 Pre-welding technology status

Pre-LSAW pipe welding is the welding work part of it along the length of seam forming a "light welding," is the production of LSAW steel pipe one of the special procedures. In the early years of the LSAW is not pre-welded steel pipe production until the second generation uoe welded pipe began to emerge in the pre-welding, but this time the pre-welded to intermittent welding, spacing of about 300mm, to uoe welding control the development of third-generation unit (1968 to 1979 Q), pre-welding has been a great focus and development, the form has not changed one after another after another form of this phase of the pre-welding technology, welding technology for the pre-modern foundation. Contemporary pre-welding technology uses a succession of high-speed gas welding (mag) in the form of laser tracking and weld, welding speed up to 7 m / min, bead molding straight decency. The mag welding, the front there are two ways: one is the we and Germany and other countries using a single wire high-speed dual-supply-current gas pre-welded, the other is used in Japan's two-wire high-speed gas pre-welded. Front of those who use more gas for the pre-high-speed single-wire welding, two of China's imported from Germany LSAW weld pipe production lines are expected in this way. Quality standards from the carbon steel pipe can also be reflected in the pre-welding technology, the latest on the ocean, low, flat and acidic conditions, standard pipe and gb/t9711.3 is03183-3 of 6.3, have been clearly does not permit the use of off continued spot, indicating a pre-welded steel quality on the main form of.

2 pre-welding work

Pre-welding, steel tube for the first commissure, followed by another gas welding, seam welding conditions and welding the same time quality monitoring and feedback. Specific work process is: to accept imports of roller tube - adjust the seat tube openings - transportation equipment delivery tube leaves the tube seam - to confirm the seam quality - welding torch landed prepare - activate the laser tracker to track - shielding gas and cooling water valve open - start welding (welding speed tube to feed) _ - stop welding to the terminal extinction - lag off shielding gas - rose back to the gun position - structural steel pipe pass down procedure. This, a pre-welding cycle is complete.