What is a LSAW Pipe?
Longitudinal Submerged Arc-Welding Pipe, LSAW， is taking the steel plate as raw material, mold it by the molding machine, then do double-sided submerged arc welding. Through this process the LSAW steel pipe will get excellent ductility, weld toughness, uniformity, plasticity and great sealing.
Diameters range and performances of LSAW pipe
Pipe O.D: Ф406.4～Ф.4mm（16-56in）
Pipe Length: Max.12.2m(40ft)
Wall Thickness: When the steel grade is X70, the wall thickness ranges from 6.4 to 26.4mm(0.252–1.04in);
When the steel grade is lower, the wall thickness will be increased accordingly
Product Standard: ISO-3; API Spec 5L, GB
Capacity: The annual output is 0.2million tons
The purpose of cold expansion for lsaw steel pipe:
After cold expansion for lsaw steel pipe, steel tube and pipe end diameter will increase by about one percent difference in diameter of the diameter, roundness, and the pipe ends are greatly improved, also have greatly improved the straightness of the steel pipe, steel pipe length of about 0.5% reduction in wall thickness decreases by about 0.8%.
Fully develop LSAW process should consider these changes, to determine the pipe plate width, length and thickness, and the pipe diameter in front of the enlarged diameter, in order to avoid the enlarged diameter steel pipe geometry reach the final requirements caused by substandard.
The purpose of cold expansion for lsaw steel pipe has the followings:
(1) Improve pipe end geometric dimensional accuracy of LSAW steel pipe, so that the diameter of the steel tube and pipe end, roundness, and the diameter of the pipe ends Poor meet the standard requirements, facilitate field welding construction.
(2) Reduce inhomogeneous deformation of LSAW steel pipe forming and welding process and decrease the residual stress of forming and welding of tube, and improve its distribution, improve the overall mechanical properties of the steel pipe.
(3) Inspect the steel pipe overall performance comprehensively and effectively.
(4) Improve the straight degree of lsaw steel pipe, especially for the smaller diameter LSAW pipe straight is more obvious.
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In the long-distance pipeline construction, pipe-line account for a large proportion, generally 35% to 40% of line pipe accounts for investment projects total investment.
How to choose a reasonable price, excellent performance pipe is particularly important to a reasonable choice of pipe to save construction investment, easy construction and safe operation of the pipeline system has a very important influence. Gas Pipelines straight seam steel high-frequency electric resistance welded steel pipe, spiral submerged arc welded pipe, LSAW steel pipe.
Limited frequency straight seam electric resistance welded steel pipe diameter range is generally limited to domestic steel Φ406.4 mm or less, the largest in Japan has reached a diameter Φ508mm. For large diameter pipe in the form of a spiral SAW, LSAW two kinds. Spiral welded steel pipe because the pipe forming process and characteristics of many shortcomings, the proportion is gradually declining in the long-distance pipeline.
In other countries, especially in many European countries, it has banned the use of spiral submerged arc welded pipe used as the main line pipe. The advantage of its unique LSAW are widely used in long-distance oil and gas pipelines, and its advantages are as follows:
One. Production process introduction of large diameter lsaw steel pipe
Rolling machine→Uncoiler→Unwinder→Retripper leveling machine→Vertical roll centering→Shear butt welding→Strip position control (double-head vertical roller)→Disc shearing→Strip position control (Double-head vertical roller )→ Edge Milling Machine (Fine Milling X Groove)→ Double End Roller→ Strip Surface Cleaning of Strips→ Double End Roller→ Conveyer→ Strip Feeding and Strip Position Control→ Molding Machine→ Inner Welding→ Outside Welding → steel pipe righting device → plasma cutting → straight seam steel pipe outlet
Two. Production process details of large diameter lsaw steel pipe
1. Work before forming
Raw materials are steel coils, welding wire, and flux. Have to go through rigorous physical and chemical tests before investing. The butt joints of the steel strips are welded with monofilament or double wire submerged arc welding. After the steel tube is rolled, automatic submerged arc welding is used for welding.
2. Molding process
The electric contact pressure gauge is used to control the pressure of the compression cylinders on both sides of the conveyor to ensure the smooth delivery of the strip. The main machine is positioned at the center. Therefore, the adjustment of the vertical roller (especially before and after the head) should be checked frequently to ensure the strict delivery edge of the strip. Run on the route specified by the process and pass the designed meshing point. External control or internal control roll forming is used to check whether the perimeter, ellipticity, straightness, etc. of the steel pipe comply with the standard requirements. If it does not meet the requirements, it will continue to be adjusted until it meets the requirements.
3. Welding process
The weld gap control device is used to ensure that the weld gap satisfies the welding requirements. The pipe diameter, the amount of misalignment, and the weld gap are all strictly controlled. The quality of the forming seam should be observed continuously, and it should be found that the misaligned edges, open seams, etc. Fine-tune the angle of the rear axle in time to ensure the quality of the forming; when the situation is abnormal, check whether the working width of the strip, the pre-bending condition of the edge, the position of the delivery line, the angle of the small roller, etc. have changed, and take corrective measures in time. Hebei’s straight seam steel pipe manufacturers currently use the United States Lincoln welding machine for single wire or double wire submerged arc welding in order to obtain stable welding quality. Straight seam steel pipe manufacturers shall continuously observe the quality of the forming joints, and shall promptly fine-tune the rear axle angle to ensure the molding quality in the case of misaligned edges, open seams, etc.; if the conditions are abnormal, check the working width, edge pre-bending condition, and delivery of the steel strip. Whether there is any change in the line position, the small roller angle, etc., and take corrective measures in time.
4. Detection
The welded welds were all inspected on-line by an automatic ultrasonic flaw detector to ensure 100% non-destructive inspection coverage of the spiral weld. If there are defects, they will be automatically alarmed and painted. The production workers will adjust the process parameters at any time to eliminate defects in time. When the nominal diameter D ≥ 426mm, the internal defects of the steel pipe should be cleaned and repaired inside; when D ≤ 426mm, the internal defects can be removed from the outside to perform the external welding. After repair welding, the weld must be ground and the remaining wall thickness after grinding should be within the specified wall thickness tolerance. Before repairing the welded steel pipe into the next process, it is necessary to carefully inspect whether there is any missing or missed defect on the steel pipe and correct it before proceeding to the next process. The butt-welded joints of the steel butt-welded joints and the spiral welds were all examined by X-ray television or film. Each pipe was hydrostatically tested and the pressure was radial sealed. The test pressure and time are strictly controlled by the steel pipe hydraulic pressure testing device. Test parameters are automatically printed and recorded.
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Post time: Jun-06-