Thick-walled welded pipes are round thick-walled welded pipes made from steel strips or steel plates from steel mills through presses or thick-walled pipe welding machines, and then welded by double-welding or submerged arc welding. All welded pipes made by this method can be called thick-walled welded pipes. Thick-walled welded pipes have lower costs and higher production efficiency than seamless steel pipes. The range of processable sizes and thicknesses is relatively wide, and the blanks used are mainly steel plates. Thick-walled welded pipes have strong corrosion resistance in acidic environments.
Thick-walled welded pipe production process
1. Steel plate inspection: Before the steel plate used to manufacture thick-walled welded pipes enters the production line, it is first subjected to full-plate ultrasonic inspection;
2. Cutting: The edges of both sides of the steel plate are milled by the edge milling machine to achieve the required steel plate width, plate edge parallelism and groove shape;
3. Pre-bending: Use a pre-bending machine to pre-bend the plate edge to meet the curvature requirements. For thicker ones, a press can be used for pre-bending.
4. Forming: First, half of the pre-bent steel plate is rolled several times on the forming machine to make it into a "J" shape, and then the other half of the steel plate is pressed into a "C" shape in the same way, and finally an open "O" shape is made
5. Pre-welding: The thick-walled welded pipe after forming is jointed and continuously welded by gas shielded welding;
6. Internal welding: The inner side of the thick-walled welded pipe is welded by longitudinal multi-wire submerged arc welding (up to four wires);
7. External welding: The outer side of the thick-walled welded pipe is welded by longitudinal multi-wire submerged arc welding;
8. Trimming: The entire welded steel pipe is trimmed to ensure the precise size required by the customer and improve the distribution of stress in the steel pipe;
9. Inspection: Ultrasonic inspection or X-ray inspection, water pressure test, anti-corrosion and coating can be performed on the thick-walled welded pipe according to customer requirements.
