LSAW steel pipe is a longitudinally parallel steel pipe. Usually divided into metric welded steel pipe, welded thin-walled pipe, transformer cooling oil pipe and so on. The straight seam welded pipe has a simple production process, high production efficiency, low cost, and rapid development. LSAW steel pipe according to the production process can be divided into high-frequency straight seam steel pipe and submerged arc welded straight seam steel pipe. Submerged arc welded straight seam steel pipes are divided into UOE, RBE, and JCOE steel pipes according to their different forming methods. The following describes the most common high-frequency straight seam steel pipe and submerged arc welded straight seam steel pipe forming process.
1. Striking: After the steel plate used for manufacturing large-diameter submerged-arc welded straight-joint steel pipes enters the production line, full-plate ultrasonic inspection is first performed;
2. Milling edge: Through the edge milling machine, the two edges of the steel plate are double-sided milled to achieve the required plate width, plate edge parallelism and groove shape;
3. Pre-bend: Pre-bending machine for pre-bending the edge so that the edge of the board has a curvature that meets the requirements;
4. Forming: Firstly, half of the pre-bent steel plate is stamped and stamped into a "J" shape on a JCO forming machine. The other half of the steel plate is also bent and pressed into a "C" shape to form an opening. The "O" shape
5. Pre-welding: After the formation of straight seam welded steel pipe joints and continuous welding using gas shielded welding (MAG);
6. Internal welding: Use vertical multi-wire submerged arc welding (up to four wires) to weld inside the straight seam steel pipe;
7. Outer welding: Use vertical multi-wire submerged arc welding to weld outside LSAW steel pipe;
8. Ultrasonic inspection I: 100% inspection of the internal and external welds of the longitudinal welded steel pipe and the base metal on both sides of the weld;
9. X-ray inspection I: 100% X-ray industrial television inspection of the inner and outer welds, using image processing systems to ensure the detection sensitivity;
10. Expanded diameter: The full-length of the submerged-arc welded straight seam steel pipe is expanded to improve the dimensional accuracy of the steel pipe, and the distribution of the internal stress of the steel pipe is improved;
11. Hydraulic pressure test: The root diameter of the expanded steel pipe is tested on the hydrostatic testing machine to ensure that the steel pipe meets the required test pressure. The machine has automatic recording and storage functions;
12. Chamfering: After passing the inspection, the steel pipe is processed by the pipe end to reach the required pipe end groove size;
13. Ultrasonic inspection II: Ultrasonic inspection is performed one by one again to check for defects that may occur in straight seam welded steel pipes after diameter expansion and water pressure.
14. X-ray examination II: X-ray industrial television inspection and tube-end weld seam examination of steel tubes after diameter expansion and hydrostatic pressure testing;
15. Tube end magnetic particle inspection: This inspection is performed to find the tube end defects;
16. Anti-corrosion and coating: The qualified steel pipe is anti-corrosion and coating according to the user's requirements.
