Spiral steel pipe production process

　　(1) Raw materials are strip steel coil, welding wire and welding flux. Before investment, strict physical and chemical tests shall be carried out.

　　(2) Single wire or double wire submerged arc welding is adopted for butt joint of strip steel head and tail, and automatic submerged arc welding is adopted for repair welding after being rolled into steel pipe.

　　(3) Before forming, the strip steel shall be levelled, sheared, planed, cleaned, transported and pre bent.

　　(4) The electric contact pressure gauge is used to control the pressure of the press down oil cylinders on both sides of the conveyor to ensure the smooth transmission of the strip steel.

　　(5) External or internal roll forming is adopted.

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

　　(7) Both internal welding and external welding are conducted by single wire or double wire submerged arc welding with American Lincoln electric welding machine, so as to obtain stable welding specifications.

　　(8) The welded seams are inspected by online continuous ultrasonic automatic damage detector, ensuring 100% coverage of nondestructive testing of spiral welds. If there is any defect, it will automatically alarm and paint the mark, and the production workers will adjust the process parameters at any time to eliminate the defect in time.

　　(9) The air plasma cutting machine is used to cut the steel pipe into single pieces.

　　(10) After cutting into a single steel pipe, the first inspection system shall be strictly carried out for three steel pipe heads of each batch to check the mechanical property, chemical composition, fusion condition of the weld, the surface quality of the steel pipe and the non-destructive inspection to ensure that the pipe manufacturing process is qualified before the pipe can be formally put into production.

　　(11) The position with continuous acoustic flaw detection mark on the weld shall be rechecked by manual ultrasonic and X-ray. If there is any defect, it shall be repaired and then undergo NDT again until it is confirmed that the defect has been eliminated.

　　(12) The pipe where the butt weld of strip steel and the T-shaped joint intersected with the spiral weld are located shall be inspected by X-ray television or film.

　　(13) Each steel pipe is subject to hydrostatic test, and the pressure is sealed radially. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Test parameters are automatically printed and recorded.