Spiral steel pipe (SSAW steel pipe)
is a spiral seam steel pipe made of strip steel coils as raw materials, often extruded and formed by automatic double-wire double-sided submerged arc welding. The spiral steel pipe feeds the strip steel into the welded pipe unit. After rolling by multiple rollers, the strip steel is gradually rolled up to form a round tube blank with an open gap. The reduction of the squeeze roller is adjusted to control the weld gap at 1~ 3mm, and make both ends of the welding joint flush.
SSAW Steel Pipe Manufacturing Process:
(1) Raw materials: strip coil, welding wire, flux. Strict physical and chemical inspections are required before investment.
(2) Butt joint of strip steel head and tail, adopt single wire or double wire submerged arc welding, after coiling into steel pipe, adopt automatic submerged arc welding repair welding.
(3) Before forming, the strip undergoes leveling, edge trimming, edge planing, surface cleaning and conveying, and pre-bending treatment.
(4) The electric contact pressure gauge is 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 welding seam gap control device is used to ensure that the welding seam gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the welding seam gap are all strictly controlled.
(7) Both internal welding and external welding adopt American Lincoln electric welding machine for single-wire or double-wire submerged arc welding, so as to obtain stable welding quality.
(8) The welded seam after welding has been inspected by an online continuous ultrasonic automatic flaw instrument, which guarantees 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 individual pieces.
(10) After cutting into single steel pipes, each batch of steel pipes must undergo a strict initial inspection system to check the mechanical properties, chemical composition, fusion status of the weld, the surface quality of the steel pipe and pass non-destructive inspection to ensure that the pipe-making process is qualified. After that, it can be officially put into production.
(11) The parts with continuous sonic flaw detection marks on the weld are re-examined by manual ultrasonic and X-ray. If there are defects, after repairing, they will go through non-destructive inspection again until it is confirmed that the defects have been eliminated.
(12) The pipes where the strip steel butt welding seams and the D-shaped joints intersecting with the spiral welding seams are all inspected by X-ray television or filming.
(13) Each steel pipe undergoes hydrostatic pressure test, and the pressure adopts radial seal. The test pressure and time are strictly controlled by the steel pipe hydraulic microcomputer detection device. The test parameters are automatically printed out.
(14) The pipe end is machined to accurately control the verticality of the end face, the bevel angle and the obtuse edge.
1. If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the weld will not be fused or cracked due to poor intercrystalline joints.
2. If the gap is too small, the proximity effect will increase, and the welding heat will be too large, causing the weld to burn; or the weld will form a deep pit after being extruded and rolled, which will affect the surface quality of the weld.
After the two edges of the tube blank are heated to the welding temperature, under the squeeze of the squeeze roller, a common metal crystal grain is formed to infiltrate and crystallize each other, and finally a firm weld is formed. If the extrusion force of the spiral steel pipe is too small, the number of common crystals formed will be small, and the weld metal strength will decrease, and cracks will occur after the force is applied; if the extrusion force is too large, the molten metal will be extruded from the weld. Not only reduces the strength of the weld, but also produces a large number of internal and external burrs, and even causes defects such as weld overlap.
Main technological characteristics of spiral steel pipe:
a. During the forming process, the steel plate deforms evenly, 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-steel-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes. It has advantages that other processes cannot match, and can satisfy users. There are more requirements in terms of spiral steel pipe specifications.
b. Adopting advanced double-sided submerged arc welding technology, welding can be realized in the best position, and it is not easy to have defects such as wrong edge, welding deviation and incomplete penetration, and it is easy to control welding quality.
c. Perform 100% quality inspection on steel pipes, so that the whole process of steel pipe production is under effective inspection and monitoring, which effectively guarantees product quality.
d. All equipment of the entire production line has the function of networking with the computer data acquisition system to realize instant data transmission, and the central control room will control the technical parameters in the production process.