The main production process of large-diameter welded pipe,

Plate inspection: After the steel plate used to make large-diameter submerged arc welded pipe enters the production line, the whole plate is firstly inspected by ultrasonic;

Edge milling: Double-sided milling is performed on both sides of the steel plate by a milling machine to make it reach the required plate width, plate edge parallelism and groove shape.

 Pre-bending: Use a pre-bending machine to pre-bend the edge of the board so that the edge has a curvature that meets the requirements;

Forming: On the JCO forming machine, one half of the pre-bent steel plate is stamped repeatedly and pressed into a "J" shape, and then the other half of the steel plate is bent into a "C" shape, finally forming an opening The "O" shape 5.

Pre-welding: The formed longitudinally welded steel pipes are joined together and the gas maintenance welding (MAG) is selected for continuous welding.

Internal welding: For large-caliber self-seam welded pipes, longitudinal multi-wire submerged arc welding (four wires at most) is used for welding on the inside of the welded pipe;

Outer welding: large-diameter self-seam welded pipes are welded on the outside of the longitudinal submerged arc welded steel pipe with longitudinal multi-wire submerged arc welding.

Ultrasonic inspection I: 100% inspection of the front and back welds of the longitudinally welded steel pipe and the base materials on both sides of the weld; welded pipes.

X-ray inspection I: 100% X-ray industrial TV inspection of the welds on the outside and inside, and an image processing system is selected to ensure the sensitivity of flaw detection;

Diameter expansion: large-diameter self-seam welded pipe expands the full length of the submerged arc welded pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of internal stress in the steel pipe.

Hydraulic test: The expanded steel pipes are inspected one by one on the hydraulic testing machine to ensure that the steel pipe reaches the test pressure required by the specification. The machine has the function of automatic recording and storage;

Chamfering: Process the pipe end of the qualified steel pipe to reach the required pipe end bevel size.