The spiral steel pipe is made by rolling low-carbon structural steel or low-alloy structural steel strip into pipe , according to a certain angle of spiral line (called forming angle), and then welding the pipe seams.
It can be used for produce large diameter steel pipe with narrow strip steel.
The specification of spiral steel pipe is expressed by outer diameter * wall thickness.
The welded pipe shall be tested by the hydrostatic test, tensile strength and cold bending, the performance of the welding seam shall meet the requirements of specification.
Main purpose:
The spiral steel pipe is mainly used for oil and natural gas transmission.
Production process:
(1) Raw materials: steel coil, welding wire and flux. Strict physical and chemical inspection shall be carried out before production.
(2) The butt welding the head and tail of coil to make the two coils jointed ,then adopts single wire or double wires submerged arc welding, and automatic submerged arc welding is adopted for welding after rolling into steel pipe.
(3) Before forming, the strip steel shall be leveled, trimmed, planed, surface cleaned, transported and pre bent.
(4) The electric contact pressure gauge is used to control the pressure of the pressing oil cylinder on both sides of the conveyor to ensure the transportation of strip steel smoothly .
(5) For the roll forming, use external control or internal control.
(6) Use the weld gap control device to ensure that the weld gap meets the welding requirements, then the pipe diameter, misalignment and weld gap can be strictly controlled.
(7) Both internal welding and external welding adopt American Lincoln Electric welding machine for single wire or double wires submerged arc welding, so as to obtain stable welding performance.
(8) All welding seams are inspected by on-line continuous ultrasonic automatic flaw detector to ensure 100% NDT test covering all the spiral welding seams. If there are defects, it will automatically alarm and spray marks, and the production workers will adjust the process parameters at any time to eliminate the defects in time.
(9) The steel pipe is cut into single piece by cutting machine.
(10) After cutting into single steel pipe, each batch of steel pipe will be subject to a strict first inspection system to check the mechanical properties, chemical composition, fusion condition, surface quality of steel pipe and NDT to ensure that the pipe making process is qualified before it can be officially put into production.
(11) The parts with continuous acoustic flaw detection marks on the welding seam shall be rechecked by manual ultrasonic and X-ray. If there are defects, after repair, the pipe shall be subject to NDT again until it is confirmed that the defects have been eliminated.
(12) The pipe of butt welding seam and T-joint intersecting spiral welding seam shall be inspected by X-ray television or film inspection.
(13) Each steel pipe is subject to hydrostatic test. The test pressure and time are strictly controlled by the computer detection device of steel pipe water pressure. Test parameters are automatically printed and recorded.
(14) The pipe end is machined to accurately control the perpendicularity, bevel angle and root face.
Post time: Jul-13-2022