DN300 LSAW Pipes

What's the difference between LSAW and SSAW?

To distinguish the two, we must first start with the names of "vertical seam" and "Spiral seam" which directly point out their core differences: weld shape and forming method, which also determines their performance boundaries.

LSAW Pipe: A Strong Straight-Seam Steel Sheet "Deformed"

The full name of LSAW is "longitudinal submerged arc welded pipe", which is made of a single wide and thick steel plate through three steps of "forming-welding-straightening". The most critical feature is that the weld is parallel to the axis of the steel pipe. In the LSAW workshop in Huayang, most of the raw materials we use are high-strength steel plates such as Q345B and X70 produced by Angang and Shougang. The thickness ranges from 9mm to 50mm, and the maximum width can reach 1.4m. This directly determines that the maximum diameter of LSAW pipes can reach DN1400.

Many clients wonder how a flat steel plate turn into a round pipe. Taking DN800 LSAW pipe produced by Huayang for Sinopec's high-pressure gathering and transportation project in 2023 as an example, we first send X70 steel plate with a thickness of 16mm into a pre-bender, press the edges of both sides of the steel plate into arcs, and then use a 4,000-ton hydraulic press to gradually press it into a tube blank in the order of "U-shape →O-shape". In this process, the pressure accuracy of the hydraulic press must be controlled within 0.1MPa, otherwise the roundness deviation of the tube blank will exceed the standard. After the tube blank is formed, the longitudinal weld is welded by double-wire submerged arc welding technology. The arc covered with flux can effectively isolate the air and avoid the oxidation of the weld. The tensile strength of the final product is 5% higher than that of the base metal.