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Metallurgical Properties and Quality Assurance of Spiral Steel Pipe
Date:2019-06-23      View(s):22      Tag:Metallurgical Properties and Quality Assurance of Spiral Steel Pipe
Straight seam steel pipe is produced by steel plate, while spiral welded pipe is produced by hot rolled coil. The hot strip rolling process has a series of advantages, and has the ability to obtain metallurgical technology for producing high quality pipeline steel. For example, water cooling systems are provided at the output stage to accelerate cooling, which allows the use of low alloy components to achieve specific strength levels and low temperature toughness, thereby improving the weldability of steel. But this system is basically not in the steel plate factory.  Coil alloy content (carbon equivalent) is usually lower than that of similar steels, which also improves the weldability of spiral welded pipes. It should be noted that the coil rolling direction of spiral welded pipe is not perpendicular to the axial direction of steel pipe, and the rolling direction of steel plate of straight welded pipe is perpendicular to the axial direction of steel pipe. The crack resistance of welded pipe is better than that of straight seam pipe. According to the requirements of the production standard of spiral welded pipe, the main inspection/control items of spiral welded pipe include: dimension: outer diameter, wall thickness, ellipticity, curvature, pipe end verticality, length and appearance quality: welded pipe tensile test, hydraulic test, acid corrosion test, non-destructive testing, while straight welded pipe does not meet the corresponding production standard. Generally, the on-line continuous inspection method is used in the spiral welded pipe unit to ensure the welding quality, which is different from another important feature of spiral welded pipe production. Continuous inspection is conducive to the monitoring of welding defects, stable welding quality and guarantee of welding grade. Due to the limitation of production process, it is extremely difficult to realize continuous and uninterrupted detection of longitudinal welded pipe. This will increase the probability of welding hazards and quality problems, and even affect the overall reliability of future pipeline operation.

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