Technological process of double-sided submerged arc welding spiral steel pipe

After the steel plate enters the production line, firstly, the whole plate is inspected by ultrasonic; Edge milling: Double-sided milling is carried out on the two edges of the steel plate by an edge milling machine, so as to achieve the required plate width, plate edge parallelism and groove shape; Pre-bending edge: pre-bending the edge of the plate by using a pre-bending machine to make the edge of the plate have the required curvature; Forming: firstly, on the JCO forming machine, half of the pre-bent steel plate is pressed into a J shape by multiple steps, then the other half of the steel plate is bent into a C shape, and finally an open O-shaped pre-welding is formed: the formed steel pipe is jointed and continuously welded by gas shielded welding (MAG); Internal welding: longitudinal multi-wire submerged arc welding (up to four wires) is used to weld the inside of straight welded steel pipe; G, external welding: welding on the outer side of the spiral submerged arc welded steel pipe by adopting multi-wire submerged arc welding; Ultrasonic inspection I: 1% inspection of the inner and outer welds of spiral steel pipe and the parent metal on both sides of the weld; X-ray inspection ⅰ: 1% X-ray industrial television inspection of internal and external welds is carried out, and image processing system is adopted to ensure the sensitivity of flaw detection; Expanding: the full length of straight-seam steel pipe is expanded to improve the dimensional accuracy of steel pipe and improve the distribution of internal stress in steel pipe; Hydrostatic test: the expanded steel pipes are inspected one by one on the hydrostatic testing machine to ensure that the steel pipes meet the test pressure required by the standard, which has the function of automatic recording and storage; Chamfering: the qualified steel pipe is processed at the end to meet the required pipe end groove size; Ultrasonic inspection Ⅱ: ultrasonic inspection shall be carried out one by one again to check the possible defects of straight seam welded steel pipes after expanding and water pressure; X-ray inspection II: X-ray industrial television inspection and tube-end weld shooting are carried out on the steel tube after expanding and hydrostatic test; Magnetic particle inspection of pipe end: this inspection is carried out to find pipe end defects; Anti-corrosion and coating: qualified steel pipes shall be subjected to anti-corrosion and coating according to user's requirements. In addition to the above inspection items, according to API standards and other related standards and the special requirements of some users, it is necessary to carry out destructive inspection and other inspections on steel plates and steel pipes, including random inspection of physical and chemical properties of raw materials entering the factory and 1% appearance inspection of steel plates.