Large-diameter spiral steel pipe is a general term, generally referring to spiral steel pipes with a diameter greater than 1 meter. Spiral steel pipes are made of steel strips that are bent and then welded. Steel pipes need to undergo hydraulic pressure, bending, flattening and other experiments, and have certain requirements for surface quality. The delivery length is usually 12 meters, and delivery to fixed length is often required. The specifications of spiral steel pipes are expressed in nominal diameter (mm). The nominal diameter is different from the actual diameter. According to the specified wall thickness, there are two types: ordinary steel pipes and thickened steel pipes.
Commonly used materials are: Q235A, Q235B.Q23b, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb. Q345 L245 L290 X42 X46 X70 X80
Spiral steel pipes are mainly used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction. They are one of the twenty key products developed. For liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural purposes: piling pipes, bridges; pipes for docks, roads, building structures, etc.
production process
Spiral steel pipe is a spiral seam steel pipe made of strip steel coil as raw material, extruded at constant temperature, and welded by automatic double-wire double-sided submerged arc welding process. The main production process is as follows:
(1) Raw materials include steel strip coil, welding wire and flux. They must undergo strict physical and chemical inspections before being put into use.
(2) The head and tail of the steel strip are butt-jointed using single-wire or double-wire submerged arc welding. After being rolled into a steel pipe, automatic submerged arc welding is used for repair welding.
(3) Before forming, the strip steel is leveled, trimmed, planed, surface cleaned, transported and pre-bent.
(4) Electric contact pressure gauges are used to control the pressure of the cylinders on both sides of the conveyor to ensure smooth transportation of the strip.
(5) Adopt external control or internal control roller forming.
(6) A weld gap control device is used to ensure that the weld gap meets the welding requirements. The pipe diameter, offset amount and weld gap are all strictly controlled.
(7) Both internal and external welding use American Lincoln welding machines for single-wire or double-wire submerged arc welding to obtain stable welding specifications.
(8) All completed welds have been inspected by an online continuous ultrasonic automatic flaw detector, ensuring 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically alarm and spray mark, so that production workers can adjust the process parameters at any time to eliminate defects in time.
(9) Use an air plasma cutting machine to cut the steel pipe into individual pieces.
(10) After cutting into individual steel pipes, the first three steel pipes in each batch must undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, the surface quality of the steel pipes, and non-destructive testing to ensure the pipe making process Only after passing the test can it be officially put into production.
(11) The areas with continuous sonic flaw detection marks on the welds will undergo manual ultrasonic and X-ray re-examination. If there are indeed defects, they will be repaired and then undergo non-destructive inspection again until it is confirmed that the defects have been eliminated.
(12) The pipes where the strip butt welds and the T-shaped joints intersecting the spiral welds are located must be inspected by X-ray television or film.
(13) Each steel pipe has undergone a 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. Test parameters are automatically printed and recorded.
(14) The pipe end is machined to accurately control the end face verticality, bevel angle and blunt edge.
