Spiral steel pipe is a spiral seam steel pipe made of strip steel coil as raw material, extruded at regular temperature, and welded by automatic double-wire double-sided submerged arc welding process. The spiral steel pipe sends the strip steel into the welded pipe unit, and after rolling by multiple rollers, the strip steel is gradually rolled up to form a circular tube billet with an opening gap. Adjust the reduction of the extrusion roller to control the weld seam gap at 1~ 3mm, and make both ends of the welding port flush.
Production Process
(1) Raw materials are strip steel coils, welding wires, and fluxes. Before putting into use, they must go through strict physical and chemical tests.
(2) The head-to-tail butt joint of strip steel adopts single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after being rolled into steel pipes.
(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 the smooth conveying of the strip.
(5) Adopt external control or internal control roll forming.
(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, misalignment and weld gap are strictly controlled.
(7) Both internal welding and external welding use American Lincoln welding machine for single-wire or double-wire submerged arc welding, so as to obtain stable welding quality.
(8) The welded seams are all inspected by an online continuous ultrasonic automatic flaw detector, which ensures 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically alarm and spray the mark, and the production workers can adjust the process parameters at any time according to this to eliminate the defect in time.
(9) Use an air plasma cutting machine to cut the steel pipe into single pieces.
(10) After cutting into single steel pipes, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, steel pipe surface quality and non-destructive testing to ensure that the pipe-making process is qualified After that, it can be officially put into production.
(11) The parts marked by continuous ultrasonic flaw detection on the weld shall undergo manual ultrasonic and X-ray re-examination. If there are indeed defects, after repairing, they shall undergo non-destructive inspection again until the defects are confirmed to be eliminated.
(12) The pipes where the strip steel butt welds and the D-joints intersecting with the spiral welds are located have all been inspected by X-ray TV or film.
(13) Each steel pipe has passed the 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) The pipe end is machined to accurately control the verticality of the end face, the bevel angle and the blunt edge.
Weld treatment
1. If the gap is too large, the proximity effect will be reduced, the heat of the eddy current will be insufficient, and the intergranular bonding of the weld will be poor, resulting in lack of fusion or cracking.
2. If the gap is too small, the proximity effect will increase, the welding heat will be too large, and the weld seam will be burned; or the weld seam will form deep pits after extrusion and rolling, which will affect the surface quality of the weld seam.
After the two edges of the tube blank are heated to the welding temperature, under the extrusion of the extrusion roller, the common metal grains are formed to penetrate and crystallize each other, and finally form a firm weld. If the extrusion force of the spiral steel pipe is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracks will occur after being stressed; if the extrusion force is too large, the molten metal will be squeezed out of the weld, It not only reduces the strength of the weld seam, but also produces a large number of internal and external burrs, and even causes defects such as weld laps.
Process characteristics
Main process characteristics of spiral steel pipe:
a. During the forming process, the deformation of the steel plate is uniform, the residual stress is small, and the surface does not produce scratches. The processed spiral steel pipe has greater flexibility in the size and specification range of diameter and wall thickness, especially in the production of high-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes. There are more requirements in terms of spiral steel pipe specifications.
b. Using advanced double-sided submerged arc welding technology, welding can be realized at the best position, and it is not easy to have defects such as misalignment, welding deviation and incomplete penetration, and it is easy to control the welding quality.
c. Carry out 100% quality inspection of steel pipes, so that the whole process of steel pipe production is under effective inspection and monitoring, effectively ensuring product quality.
d. All the equipment of the entire production line has the function of networking with the computer data acquisition system to realize real-time data transmission, and the technical parameters in the production process are checked by the central control room.
Post time: Dec-02-2022