The welding process of straight seam can be divided into resistance welding straight steel pipes and buried arc welded straight seam steel pipes. Among them, resistance welded straight seam steel pipes are divided into high -frequency welding straight seam steel pipes, medium -frequency welding straight seam steel pipes, low -frequency welding straight seam steel pipes. The buried arc welding straight seam steel pipe is also called double -sided buried arc welding straight seam steel pipe or LSAW straight seam steel pipe. The LSAW is (Longitudinally Submerged Arc Welding abbreviation is abbreviated as LSAW).
The Electric Resistance Weldin, also known as ERW straight steel pipe, is also called Electric Resistance Weldin. High -frequency welding straight seam steel pipe is also called ERW straight seam steel pipe. ERW is a collective name for resistor welding steel pipes. Electric resision welding (ELW) ERW is the first letter corresponding to English words, respectively.
The resistance welding steel pipe is divided into two forms: AC welded steel pipe and DC welded steel pipe. The AC welding is divided into low -frequency welding, medium frequency welding, ultra -medium -frequency welding and high -frequency welding according to different frequencies. High -frequency welding is mainly used for the production of thin -walled steel pipes or ordinary wall thick steel pipes. High -frequency welding is divided into contact welding and inductive welding. DC welding is generally used for small -caliber steel pipes.
Regardless of which straight steel pipe welding process, the main steps are similar:
1. Plate exploration: After the steel plates used to create large -caliber buried arc welding straight seam steel pipes enter the production line, first perform the full board ultrasonic inspection;
2. Milling edge: Double -sided milling on both edges of the steel plate by milling machine can achieve the required plate width, parallel parallelity, and shape of the slope;
3. Pre -bending edge: Use the pre -bending machine to pre -bending on the edge of the plate to make the edge of the board have a curved curvature;
4. For molding: First of all, half of the steel plate after the pre -curved steel plate was stamped multiple times on the JCO molding machine, pressed it into a "J" shape, and then the other half of the steel plate was also bent, pressed into a "C" shape, and finally formed an opening opening. "O" shape
5. Pre -welding: Make the forming straight seam welded steel pipes and seams and use gas protection welding (MAG) for continuous welding;
6. Internal welding: Use the columns to bury the arc welding (up to four wires) on the inside of the straight steel pipes;
7. External welding: Use the columns to bury the arc welding on the outside of the stitched arc welded steel pipe for welding;
8. Ultrasonic inspection Ⅰ: 100%inspection of the latch weld and welded seams and welds in the straight seam welded steel pipes;
9. X -ray examination Ⅰ: 100%X -ray industrial TV inspection of welded seams internal and external welds, using an image processing system to ensure the sensitivity of the detection;
10. Expansion: The full length of the buried arc welding straight seam steel pipe is expanded to improve the size and accuracy of the steel pipe, and improve the distribution state of the stress in the steel pipe;
11. Water pressure test: The steel pipe after the diameter expanded on the hydraulic test machine is inspected to ensure the test pressure of the steel pipe to meet the standard requirements. The machine has an automatic recording and storage function;
12. Inverted edges: The pipe ending of the tube after the inspection is passed to meet the requirements of the required pipe end slopes;
13. Ultrasonic test II: Ultrasonic inspection is performed again to check the defects that the straight seam welded steel pipes may produce after the diameter and water pressure;
14. X -ray examination II: The X -ray industrial TV inspection and pipe welding seam filming of the steel pipes after the diameter and hydraulic test;
15. Tube -side magnetic powder test: conduct this inspection to discover the tube -side defects;
16. Anti -corrosion and coating: The qualified steel pipes perform anticorrosion and coating according to user requirements.
