Longitudinal Welded Pipe Forming Process

1 、Plate inspection: after the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipes enters the production line, the entire plate is ultrasonically inspected;

2、Edge milling: use the edge milling machine to mill the two edges of the steel plate on both sides to make it meet the required plate width, plate edge parallelism and groove shape;

3、Pre-bending: Use a pre-bending machine to pre-bend the edge of the plate so that the edge of the plate has a curvature that meets the requirements;

4、 Forming: On the JCO forming machine, half of the pre-bent steel plate is pressed into a "J" shape by multiple steps, and then the other half of the steel plate is also bent into a "C" shape, and then the opening is formed. "O" shape;

5、 Pre-welding: Make the formed straight seam welded steel pipe seam together and use gas shielded welding (MAG) for continuous welding;

6、Internal welding: use tandem multi-wire submerged arc welding (mostly four wires) to weld on the inner side of the straight seam steel pipe;

7、External welding: use tandem multi-wire submerged arc welding to weld on the outside of the straight seam submerged arc welded steel pipe;

8、 Ultrasonic inspection Ⅰ: high-standard inspection of the inner and outer welds of the straight seam welded steel pipe and the base metal on both sides of the weld;

9、X-ray inspection Ⅰ: Carry out high-standard X-ray industrial TV inspection for internal and external welds, and use image processing system to ensure the sensitivity of flaw detection;

10、 Diameter expansion: expand the full length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of internal stress of the steel pipe;

11、Hydrostatic test: On the hydrostatic testing machine, inspect the expanded steel pipes one by one to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;

12、 Chamfering: process the pipe end of the qualified steel pipe to meet the required bevel size of the pipe end;

13、Ultrasonic inspection Ⅱ: Conduct ultrasonic inspection one by one again to check the possible defects of straight seam welded steel pipes after diameter expansion and hydraulic pressure;

14、 X-ray inspection II: Carry out X-ray industrial TV inspection and filming of pipe end welds on steel pipes after diameter expansion and hydrostatic test;

15、Tube end magnetic particle inspection: This inspection is carried out to find tube end defects;

16、Anti-corrosion and coating: The qualified steel pipes are anti-corrosion and coating according to user requirements.