Square pipe production process flow

　　(1) raw materials, namely, steel coil, welding wire and flux. Strict physical and chemical tests must be carried out before putting into operation.

　　(2) Single wire or double wire submerged arc welding is used for butt welding of strip head and tail, and automatic submerged arc welding is used for repair welding after coiling square pipe.

　　(3) before forming, strip is leveled, trimming, planing, surface cleaning, transportation and bending.

　　(4) Electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of strip steel.

　　(5) external control or internal control roller forming. Carbon steel flange

　　(6) The weld gap control device is adopted to ensure that the weld gap meets the welding requirements, and the pipe diameter, staggered edge and weld gap are strictly controlled.

　　(7) Both internal welding and external welding are carried out by single wire or double wire submerged arc welding with American Lincoln welding machine to obtain stable welding specification.

　　(8) The welds are inspected by on-line continuous ultrasonic automatic flaw detector to ensure 100% coverage of spiral welds. If there is a defect, the automatic alarm and spray marking, production workers at any time to adjust the process parameters, timely elimination of defects.

　　(9) use the air plasma cutting machine to cut the square pipe into a single root.

　　(10) After cutting into a single square pipe, each batch of square pipe head three to carry out a strict first inspection system, check the mechanical properties of welds, chemical composition, dissolution status, square pipe surface quality and through non-destructive testing, to ensure that the tube-making process qualified before formally put into production.

　　(11) The part with continuous acoustic flaw detection mark on the weld, after manual ultrasonic and X-ray re-examination, if there is a defect, after repair, through non-destructive testing again, until it is confirmed that the defect has been eliminated.

　　(12) The butt welded seam of strip steel and the tube where the D-joint intersects the spiral weld seam are all examined by X-ray television or photography.

　　(13) every square tube is subjected to hydrostatic pressure test and the radial seal is adopted. The test pressure and time are strictly controlled by the square pipe hydraulic pressure microcomputer testing device. The test parameters are automatically printed and recorded.

　　(14) machining the end of the pipe, making the verticality of the end face, the slope angle and the blunt edge accurately controlled.