Production process for large diameter LSAW welded pipe

Large diameter LSAW welded pipes are suitable for demanding applications in various industries. To make sure that large diameter LSAW welded pipes meet stringent quality and performance standards, comprehensive production process need to be guaranteed.

·  Plate Probe: Upon entering the production line, the steel plates intended for manufacturing large diameter submerged arc welded (LSAW) pipes undergo full-board ultrasonic testing to detect any imperfections.

·  Milling: A milling machine is used to trim the edges of the plates, ensuring the width meets specifications and the edges are parallel with the required groove shape and degree.

·  Pre-curved Side: The edges of the plates are pre-bent using a pre-bending machine, ensuring the curvature meets the specified requirements.

·  Forming: The pre-bent plate undergoes several stamping steps in a JCO forming machine. Initially, the plate is pressed into a "J" shape, followed by a "C" shape, and finally formed into an open "O" shape.

·  Pre-welding: The formed steel pipe undergoes continuous welding of the seam using gas metal arc welding (MAG).

·  Inside Weld: The internal seam of the LSAW steel pipe is welded using a tandem multi-wire submerged arc welding process, which can use up to four wires.

·  Outside Weld: The external seam is welded using the same tandem multi-wire submerged arc welding method as the internal seam.

·  Ultrasonic Testing: Both the internal and external seams, as well as the base material on both sides of the weld, are subjected to 100% ultrasonic inspection to ensure weld integrity.

·  X-ray Inspection: The welds undergo 100% X-ray inspection using an industrial TV inspection system with image processing to ensure detection sensitivity.

·  Expansion: The welded steel pipes are expanded to improve dimensional accuracy and ensure even stress distribution throughout the pipe.

·  Hydraulic Test: Each expanded pipe is subjected to a hydraulic pressure test to verify that it meets the required pressure standards. The test machine is equipped with automatic recording and storage capabilities.

·  Chamfering: After inspection, the pipe ends are processed to meet beveling size requirements, ensuring proper fit and finishing.