Straight seam steel pipes are steel pipes whose welds are parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe and so on. Longitudinal welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can also be used to produce welded pipes with different pipe diameters. But compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower. Straight seam steel pipes can be divided into high frequency straight seam steel pipes and submerged arc welded straight seam steel pipes according to the production process. Submerged arc welded straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. 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 forming process.

3. Pre-bending: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements;
4. Forming: First half of the pre-bent steel plate is pressed into a "J" shape on the JCO forming machine through multiple stepping steps, and then the other half of the steel plate is also bent and pressed into a "C" shape, and finally an opening is formed "O" shape;
5. Pre-welding: Join the formed longitudinally welded steel pipe and use gas shielded welding (MAG) for continuous welding;
6. Internal welding: use longitudinal multi-wire submerged arc welding (up to four wires) to weld on the inner side of the straight seam steel pipe;
7. External welding: use longitudinal multi-wire submerged arc welding to weld on the outside of the longitudinal submerged arc welded steel pipe;
8. Ultrasonic inspection I: 100% inspection of the inner and outer welds of the longitudinally welded steel pipe and the base materials on both sides of the weld;
9. Radiographic inspection I: 100% X-ray industrial television inspection of the inner and outer welds, using an image processing system to ensure the sensitivity of flaw detection;
10. Diameter expansion: expand the total length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of the internal stress of the steel pipe;
11. Hydraulic test: The expanded steel pipes are inspected one by one on the hydraulic testing machine to ensure that the steel pipe meets the test pressure required by the standard. The machine has automatic recording and storage functions;
12. Chamfering: Process the pipe ends of the steel pipes that have passed the inspection to meet the required pipe end groove size;
13. Ultrasonic inspection Ⅱ: Perform ultrasonic inspection again one by one to check the possible defects of the longitudinally welded steel pipe after the diameter expansion and water pressure;
14. X-ray inspection Ⅱ: X-ray industrial television inspection and pipe end weld filming of the steel pipe after the expansion and water pressure test; 
15. Pipe end magnetic particle inspection: this inspection is carried out to find the pipe end defects;
16. Anti-corrosion and coating: Qualified steel pipes are anti-corrosion and coating according to user requirements.