What are the manufacturing processes of straight seam steel pipes?

LSAW pipes can be divided into high-frequency straight seam steel pipes and submerged arc welded straight seam steel pipes according to the production process. The following introduces the most common forming processes of high-frequency straight seam steel pipes and submerged arc welded straight seam steel pipes.

submerged arc welding
After the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipe enters the production line, the entire steel plate must first be subjected to ultrasonic inspection; the two edges of the steel plate are milled on both sides with a milling machine to achieve the required plate width. Parallelism and groove shape. Use a pre-bending machine to bend the edge of the plate so that the edge of the plate has the desired curvature; press the front half of the pre-bent steel plate into a "J" shape on the JCO forming machine. Then, the other half of the steel plate is also bent and pressed into a "C" shape, and finally an open "O" shape.
The formed longitudinal welded steel pipes are connected together and continuously welded by gas shielded welding (MAG); longitudinal multi-wire submerged arc welding (up to four wires) is used to weld the inside of the longitudinal steel pipe; longitudinal multi-wire submerged arc welding is performed on Made of LSAW steel pipes on the outside. After the welding is completed, the first ultrasonic inspection (mainly inspection of the weld and the base materials on both sides), the first X-ray inspection (inspection to ensure flaw detection sensitivity), diameter expansion and hydraulic pressure test (hydraulic pressure tester Records will be saved automatically)
The qualified steel pipe is then processed into the required size, and then the second ultrasonic inspection, the second X-ray inspection, the pipe end magnetic particle inspection, anti-corrosion and coating treatment are performed in sequence to complete the entire processing process.
High frequency welding
High-frequency welding is based on the principle of electromagnetic induction and the skin effect, proximity effect and eddy current heating effect of AC charges in the conductor. The steel at the edge of the weld is heated to a molten state and then pressed with a roller to achieve intergranular bonding of the butt weld, thereby achieving the purpose of seam welding. High frequency welding is a type of induction welding (or pressure contact welding). It requires no weld filler, no welding spatter, narrow welding heat affected zone, beautiful welding shape and good welding mechanical properties. Therefore, it is widely used in the production of steel pipes. Wide range of applications.
High-frequency welding of steel pipes utilizes the skin effect and proximity effect of AC. After rolling the steel (strip), a circular tube blank with a cross-section is formed, which rotates in the tube near the center of the induction coil. Or a set of resistors (magnetic rods) that form an electromagnetic induction loop with the opening of the tube blank. Under the action of skin effect and proximity effect, the edge of the opening of the tube blank produces a strong and concentrated thermal effect, so that after the edge of the weld is rapidly heated to the temperature required for welding and squeezed by the pressure roller, the molten metal achieves intergranular bonding. , forming a strong butt weld after cooling.