LSAW Pipe

LSAW steel pipe is a technical term for Longitudinally Submerged Arc Welding steel pipe. LSAW steel pipe is created by using a medium-thickness plate as the raw material, pressing the steel plate into a tube blank in a mold or forming machine, applying the double-sided submerged arc welding method and also enlarge the diameter.

There is a wide range of specifications of this kind of products, and the weld-seam has good uniformity, compactness, plasticity and toughness. It has the strong points of large pipe diameter, thick pipe wall. It also has the advantages of corrosion resistance, high pressure resistance and low temperature resistance.

LSAW Pipe Specification

Product nameLSAW steel pipe
MaterialQ195/Q215/Q235/Q345/#20/#45
StandardAPI, ASTM, BS, GB, JIS, API 5L
Steel GradeA53,A106,SS400,STK400,STK500,Q235,Q345,X42,x46,x52,x56,x60,x70,etc.
Length5-12m
Pipe Wall Thickness8.0-60.0mm
Out Diameter325mm–1420mm
Surface TreatmentBlack coating, Anti-Finger printing, Chromating, Oiled/ Non-oiled
Pipe EndPlain end/ Bevel end, Threaded on two ends, One end with coupling, One end with a plastic cap
ApplicationBoiler Pipe/Fluid Pipe/ Boiler Pipe/Gas pipe, Bridge/Building construction/Drill Pipe
PackageStandard export package (Detailed picture is as follows)
HS code7305310000
Country of originChina
Business typeSupplier and Manufacturer
Brand nameCOSASTEEL
Business typeSupplier and manufacturer
Brand nameCOSASTEEL

LSAW Pipe Manufacturing Process

  1. Ultrasonic flaw detection of steel plates: When the production line starts, the first thing to do is perform an ultrasonic inspection of the whole plate. We need to strictly check the raw materials for the production of steel pipes.
  2. The edge milling procedure: We can carry out double-face milling on the longitudinal side of the steel plate through an automatic edge milling machine so that it can meet the processing requirements of the plate width. The milling machine has the automatic centering function of the steel plate, and the milling head has the function of rod dynamic copying tracking. The position of the milling head can be automatically adjusted according to the flatness of the steel plate to ensure that both sides of the steel plate have the same groove shape and size. The position of the milling head ensures that both sides of the steel plate have the same groove shape and size.
  3. The pre-bending procedure: Pre bending machine is used for plate edge pre-bending. The bending machine prebends the plate edge to the appropriate curvature ensures the geometric shape of the weld area and prepares for subsequent forming, welding, and expanding procedures.
  4. The forming procedure: JCO forming method is progressive multi-step molding. The steel plate is realized as an ideal circle by a numerical control system. The deformation of each part of the steel plate is uniform without obvious stress concentration, and the residual stress is small and evenly distributed.JCO forming machine will be prebent after half of the steel plate through several steps stamping, pressing into “J” shape, and then the other half of the steel plate bending, pressing into “C” shape, finally forming the “O” shape of the opening.
  5. The pre-welding procedure: The rapid joint pre welding of an open pipe is carried out by the welding machine, which lays a foundation for guaranteeing the quality of internal and external multi-wire submerged arc welding. Meanwhile, high-power continuous active gas shielded arc welding (MAG) is adopted to ensure the quality of pre-welding, which lays a good foundation for internal and external welding.
  6. The internal welding procedure: Internal welding uses tandem multi-wire submerged arc welding on the inside of the steel pipe. Its advantages are high production efficiency, less porosity, low slag inclusion rate, low crack tendency, good mechanical properties of the joint, and easy control of the weld geometry.
  7. The external welding procedure: The external welding uses longitudinal multi-wire submerged arc welding on the exterior of the steel pipe.
  8. The Acoustic flaw detection I: 100% UT automatic flaw detection of the inside and outside of the longitudinally welded pipe and the base material near the weld.
  9. The X-ray flaw detection I: The internal and external welds were inspected with 100% X-ray and the image processing system was used to ensuring the sensitivity of inspection.
  10. The diameter expansion procedure: Diameter expansion machine can expand, round, and straighten the full length of LSAW steel pipe (LSAW) to enhance the accuracy of steel pipe geometry and And the distribution of stress in steel tube can be improved.
  11. The hydrostatic test: The hydrostatic testing machine performs a hydrostatic test on the steel pipes which was expanded. The hydraulic press has the function of automatically recording and storing test pressure and time. The supercharger can increase the water pressure in the pipe within a short period of time to reach the test pressure required to meet the standard test. To ensure that the steel pipe quality can meet the requirements.
  12. Chamfering: The chamfering machine processes the pipe end beveling of the steel pipe to achieve the required pipe end bevel size, in order to ensure the welding quality of steel pipe.
  13. Sonic flaw detection I I: Perform UT flaw detection on the weld and the base metal on both sides again to inspect the possible defects of the welded pipe after the diameter expansion procedure and water pressure test.
  14. X-ray flaw detection I I: Using X-ray to detect the pipe end after the diameter expansion and hydraulic test to ensure the quality of the delivered steel pipes.
  15. Magnetic particle inspection of the pipe end: Perform this inspection to find the defects of the pipe end.
  16. Anti-corrosion and coating procedure: After all the inspection, the steel pipe shall be treated with anti-corrosion and coating.

SSAW vs LSAW pipe

SSAW steel pipe refers to the metal pipe with spiral seam welded by a submerged arc welding process. It is made by rolling low-carbon carbon structural steel or low-alloy structural steel strip according to a certain spiral angle (called forming angle) into a tube blank and then welding the tube seam together. It can be made with narrower strip steel that produces large-diameter steel pipes.

The SSAW steel pipe does not have 100% ultrasonic flaw detection and diameter expansion of the base material. The output is low, the automatic tracking of the weld is difficult, and the forming and welding are completed under the dynamic continuous operation; continuous production can be realized, using a width belt Steel can produce steel pipes of several different diameters.

The price of a coil is lower than the price of a steel plate, the production of straight seam pipe needs a great deal of human labor and needs expensive tooling, therefore, the production cost of straight seam submerged arc welding pipe is higher, the price is about 1 times higher than spiral seam submerged arc welding pipe.

SMLS vs LSAW pipes

SLMS steel pipes are perforated from whole round steel, and the steel pipes without welds on the surface are called seamless steel pipes. According to the production method, SMLS pipes can be divided into hot-rolled seamless steel pipes, cold-rolled seamless steel pipes, cold-drawn seamless steel pipes, extruded seamless steel pipes, and top pipes.

The main difference between the LSAWl pipe and SMLS pipe is production technology and application. LSAW pipe is made of iron plate, which is produced through press bending, jointing, welding, and other processes. One weld is allowed. SMLS pipe is hot-rolled from round steel through a pipe rolling mill, and there is no weld. When the diameter and wall thickness of the seamless tube and the straight seam tube are equal, the pressure and firmness of the seamless tube are far greater than that of the straight seam tube. Generally, seamless pipes are selected for engineering pipes with relatively high pressure, and straight seam pipes with relatively low cost are selected for projects with no pressure or relatively low pressure.

LSAW Steel Pipe Features

(1) The testing of 100% ultrasonic of the parent metal ensures the tube’s internal quality.

(2) Because there was no process of unwinding, flattening and alignment, the base material is dented and scratched less.

(3) The welding is carried out in a straight line in a horizontal position after the forming is completed. Therefore, the diameter and circumference of the staggered and slotted pipe are better controlled, and the welding quality is excellent.

(4) There is basically no residual stress in the finished pipe after discharge pressure.

(5) The welding seam is short and the probability of causing defects is small.

(6) It can be used to transport moist acidic natural gas conditionally.

(7) After expanding the diameter, the geometric dimensions of the steel pipe have high accuracy, which greatly facilitates the on-site butt welding of the pipeline and can improve the quality of the entire pipeline.

Applications of LSAW Pipe

LSAW pipe can be widely used in the transport of land, Marine oil and gas, natural gas, heat supply, water supply, coal slurry, and mineral slurry and other media as well as the manufacture of pipe bodies and structures for offshore platforms, power stations, railway, highway and bridge culverts, paper making, chemical industry, sports venues, and urban buildings.

ERW vs DSAW vs LSAW pipe

ERW Straight Seam Welded Pipe is a kind of welded steel pipe in which the hot-rolled sheet is melted by high-frequency current and welded under the squeeze of the squeeze roller. ERW welded pipe has the advantages of excellent dimensional accuracy, good surface quality, high production efficiency, less investment, short construction period, low production cost, and quick effect, but it requires relatively high forming quality. At present, ERW welded pipe has been widely used in petroleum, chemical industry, coal, machinery, construction, metallurgy, mining, light industry, etc. Compared with seamless steel pipes, the key to determining the mechanical properties of ERW welded pipes lies in the quality and strength of the weld.

The process principle of DSAWand single-sided submerged arc welding is basically the same, that is, using the arc heat ignited between the welding wire and the weldment to melt and evaporate the weldment, the welding wire, and the flux, and the vapor of the metal and the flux blows the molten flux away. , Form a bubble, the arc burns in the bubble to form a molten pool, as the wire feed nozzle moves forward, the molten pool cools and crystallizes to form a smooth and beautiful weld.

LSAW pipe is still the main pipe type used in oil and gas pipelines, especially for crossing pipes, submarine pipelines, and thick-walled pipelines. The development of large strain tubes and X90-X120 ultra-high-strength steel pipes mainly adopts the LSAW process.

ERW welding is through the high-frequency induction principle, so that the steel plate edge melting under pressure welding as a whole, generally suitable for welding relatively thin pipe, mostly in small and medium-sized straight seam welded pipe, DSAW is the use of welding wire, generally used in a spiral welded pipe.

DSAW is a welding process, SSAW pipe is the double-side submerged arc, LSAW pipe resistance welding and double-side submerged arc welding two kinds.

LSAW pipe is still the main pipe type used in oil and gas pipelines, especially for crossing pipes, submarine pipelines, and thick-walled pipelines. The development of large strain tubes and X90-X120 ultra-high-strength steel pipes mainly adopts the LSAW process.

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