thin-wallLarge diameter spiral steel pipeIt is a general term that generally refers to spiral steel pipes with a diameter greater than 1 meter. Spiral steel pipes are made by bending steel strips and then welding them together. Steel pipes need to undergo tests such as water pressure, bending, and flattening, and there are certain requirements for surface quality. The usual delivery length is 12 meters, and it is often required to be delivered to a fixed length. The specifications of spiral steel pipes are expressed in nominal diameter (millimeters), which may differ from the actual diameter. According to regulations, there are two types of wall thickness: ordinary steel pipes and thickened steel pipes. Thin walled large-diameter spiral steel pipe is a spiral seam steel pipe made of strip steel coil as raw material, often formed by warm extrusion, and welded by automatic double wire double-sided submerged arc welding process Submerged arc welding (including submerged arc welding and electric slag welding, etc.) is a method of welding in which an arc burns under the flux layer. Its inherent advantages such as stable welding quality, high welding productivity, no arc light, and minimal smoke and dust make it the main welding method in the production of important steel structures such as pressure vessels, pipe sections, and box beams and columns. In recent years, although many efficient and high-quality new welding methods have emerged, the application field of submerged arc welding has not been affected in any way.

Production process of thin-walled large-diameter spiral steel pipe

1. Raw materials include steel coils, welding wire, and flux. Strict physical and chemical tests must be conducted before investment.

2. The head and tail of the strip steel are connected by single or double wire submerged arc welding, and automatic submerged arc welding is used for repair welding after being rolled into a steel pipe.

Before forming, the strip steel undergoes leveling, trimming, planing, surface cleaning, conveying, and pre bending treatment.

4. An electric contact pressure gauge is used to control the pressure of the oil cylinders on both sides of the conveyor, ensuring the smooth transportation of the strip steel.

5. Adopt external or internal control roller molding.

6. Adopt a weld seam gap control device to ensure that the weld seam gap meets the welding requirements, and the pipe diameter, misalignment, and weld seam gap are strictly controlled. Both internal and external welding are carried out using American Lincoln welding machines for single or double wire submerged arc welding, in order to obtain stable welding specifications.

8. The welded seams are all inspected by an online continuous ultrasonic automatic damage tester, ensuring 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically sound an alarm and spray a mark, and production workers will adjust the process parameters accordingly to eliminate the defect in a timely manner.

9. Use an air plasma cutting machine to cut steel pipes into individual pieces.

10. After cutting into individual steel pipes, each batch of steel pipes must undergo a strict initial inspection system to check the mechanical properties, chemical composition, solubility, surface quality of the welds, and undergo non-destructive testing to ensure that the pipe manufacturing process is qualified before it can be officially put into production.

11. For the parts with continuous ultrasonic testing marks on the weld seam, manual ultrasonic and X-ray re examination shall be carried out. If there are indeed defects, they shall be repaired and undergo non-destructive testing again until it is confirmed that the defects have been eliminated.

12. The pipes where the butt welds of the strip steel and the T-shaped joints intersecting with the spiral welds are located are all inspected by X-ray television or film.

13. Each steel pipe undergoes a hydrostatic pressure test, and the pressure is sealed radially. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Automatic printing and recording of experimental parameters.

14. Mechanical processing of pipe ends to accurately control the perpendicularity, slope angle, and blunt edge of the end face.