Metallurgical Properties and Quality Assurance of Spiral Steel Pipe

Straight seam steel pipe is the production of steel plate, and spiral welded pipe is hot-rolled coil production. The rolling process of the hot strip mill has a series of advantages, and has the ability to obtain the metallurgical technology of producing high quality pipeline steel. For example, a water cooling system is provided on the output stage to accelerate cooling, which allows the use of low alloy components to achieve specific strength grades and low temperature toughness, thereby improving the weldability of the steel. But this system is basically not in the steel plate production plant. Coil alloy content (carbon equivalent) is often lower than similar grades of steel, which also improves the weldability of spiral welded pipe. It should be noted that, since the coil rolling direction of the spiral welded pipe is not perpendicular to the axial direction of the steel pipe, the rolling direction of the steel plate of the straight seam steel pipe is perpendicular to the axial direction of the steel pipe, The crack resistance of welded pipe is better than that of straight seam steel pipe. In accordance with the requirements of spiral welded pipe production standards, the main inspection / control items of spiral welded steel pipe include: Dimension: outer diameter, wall thickness, ellipticity, curvature, pipe end verticality, length Appearance quality: Welded pipe tensile test, hydrostatic test, acid corrosion test, non-destructive testing, while the straight seam welded pipe does not have the corresponding production standards. General spiral welded pipe units are used on-line continuous inspection method to ensure the welding quality of the weld, which is different from the spiral welded pipe production of straight seam welded pipe is another important feature. Continuous inspection is conducive to the monitoring of welding defects, welding quality stability, welding grade assurance. As the production process constraints, straight seam welded pipe is extremely difficult to achieve continuous uninterrupted inspection. This will increase the probability of occurrence of welding hazards and quality problems, and even affect the overall reliability of future pipeline operation.