Causes of Wrong Edges of Large-diameter Spiral Steel Pipes

Causes of wrong edges of large-diameter spiral steel pipes (SSAW):

In the production of large-diameter spiral steel pipes, misalignment occurs from time to time, and there are many influencing factors. In production practice, steel pipes are often degraded due to dry misalignment and out-of-tolerance. Therefore, it is necessary to analyze the causes of wrong edges of large-diameter spiral steel pipes and preventive measures.

1. The sickle bend of the steel belt is the most important factor causing the wrong edge of the steel pipe.
In the forming of spiral welded pipes, the sickle bend of the steel strip will continuously change the forming angle, resulting in the change of the weld gap, resulting in seams, staggered edges and even overlapping edges. The quality of the steel pipe is seriously affected. Therefore, observe the sickle bend of the steel strip after uncoiling. By controlling the vertical roll, the disc shear can cut off part of the sickle bend. The continuous control and correction of the forming angle are to reduce the sickle bend of the steel strip during the production process. An effective way to produce wrong sides.

2. Due to the poor shape and dimensional accuracy of the head and tail of the untrimmed steel strip, it is easy to cause the steel strip to bend hard and cause the wrong side to be caused by the butt joint.
3. When the reinforcement of the welding seam of the head and tail butt welding of the steel strip is large, if the over-forming is not handled properly, it is easy to cause a large misalignment.

4. The poor condition of the edge of the steel strip is another important reason for the wrong edge.

Spiral steel pipe production process:

(1) The raw materials are strip steel coils, welding wires, and fluxes. Strict physical and chemical inspections are required before investment.
(2) Butt joint of strip steel head and tail, using single wire or double wire submerged arc welding, after coiling into steel pipe, automatic submerged arc welding is used for 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 force meter is used to control the pressure of the cylinders on both sides of the conveyor to ensure the smooth conveying of the strip.
(5) Externally controlled or internally controlled roller molding is adopted.

(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 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 seams are all inspected by the online continuous ultrasonic automatic flaw instrument, which guarantees 100% non-destructive testing coverage of the spiral welds. If there is a defect, it will automatically alarm and spray the mark, and the production workers will 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 a single steel pipe, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties, chemical composition, melting condition of the weld, the surface quality of the steel pipe and the non-destructive inspection to ensure that the pipe manufacturing process is qualified. Only later can it be officially put into production.

(11) The parts with continuous sonic flaw detection marks on the welds are re-examined by manual ultrasonic and X-ray.
eliminate.
(12) The pipes where the butt-welded seams of Fe-steel and the J-joint intersecting with the spiral welds are all inspected by X-ray television or filming.
(13) Each steel pipe undergoes a hydrostatic pressure test, and the force adopts a radial seal. The test pressure and time are strictly controlled by the steel pipe hydraulic 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 obtuse edg.

As a carbon steel pipe manufacturer, Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes, welded steel pipes(ERW/SSAW/LSAW), stainless steel pipes, hollow sections, pipe fittings, etc., with more than ten years of production experience. (Fluid pipe/Boiler pipe/Fire pipe/Line pipe/Structural pipe)