Compared with seamless steel tubes, lsaw steel pipes have simple production processes, high production efficiency, low cost and rapid development. The strength of the ssaw steel pipe is generally higher than that of the straight welded pipe.
It is possible to produce a welded pipe with a larger diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter with a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low. Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded.
Production Process:
(1) Raw materials are strip coils, welding wire, flux. Strict physical and chemical testing is required before input.
(2) The steel head and tail are butt jointed, and the single wire or double wire submerged arc welding is used, and the automatic submerged arc welding is used after the steel pipe is rolled.
(3) Before forming, the strip is leveled, trimmed, planed, surface cleaned and pre-bent.
(4) The 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 the strip.
(5) Adopt external control or internal control roll molding.
(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are strictly controlled.
(7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding by American Lincoln welding machine to obtain stable welding specifications.
(8) The welded seams are all inspected by online continuous ultrasonic automatic injury inspection to ensure the non-destructive testing coverage of 100% spiral welds. If there is a defect, the alarm is automatically alarmed and sprayed, and the production worker adjusts the process parameters at any time to eliminate defects in time.
(9) The steel pipe is cut into individual pieces by an air plasma cutting machine.
(10) After cutting into a single steel pipe, each batch of steel pipe shall be subjected to a strict first inspection system to check the mechanical properties, chemical composition, bonding condition, surface quality of the steel pipe and non-destructive testing to ensure the pipe making process. After that, it can be officially put into production.
(11) The part of the weld with continuous acoustic flaw detection mark, after manual ultrasonic and X-ray review, if it is defective, after repair, it will pass the non-destructive test again until it is confirmed that the defect has been eliminated.
(12) The tube of the butt weld of the strip and the joint of the butt joint intersecting the spiral weld are all inspected by X-ray television or film.
(13) Each steel pipe is subjected to hydrostatic pressure test and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. The test parameters are automatically printed and recorded.
(14) Pipe end machining, so that the verticality of the end face, the groove angle and the blunt edge are accurately controlled.