LSAW STEEL PIPE

LSAW steel pipe is steel plate production, and is used in the production of spiral welded pipe hot rolled coil. The rolling process of hot strip mill has a series of advantages, which has the ability of producing high quality pipeline steel. For example, a water cooling system is installed on the output stage to accelerate the cooling, which allows the use of low alloy components to achieve a special strength grade and low temperature toughness, thereby improving the ability of the steel to be welded. But this system in the steel plate production plant basically did not. The content of alloy coil (carbon equivalent) are often lower than similar grades of steel, it also improves the weldability of spiral welded steel pipe. More to the point, as a result of the spiral welded pipe plate rolling direction is vertical pipe axis direction (the clip solution depending on the steel pipe of the spiral angle), and straight seam steel pipe plate rolling direction vertical to the axis direction of the steel pipe. Therefore, the crack resistance of spiral welded pipe material is better than straight seam steel pipe.

In welding process, spiral welded pipe and straight seam steel pipe welding method is consistent, but straight seam welded pipe inevitably will have a lot of T-shaped seam, so the existence of welding defects but also greatly enhance the probability, and T-shaped seam welding residual stress force is larger, the weld metal often in triaxial state of stress, increase the possibility of cracks. Moreover, according to the process of submerged arc welding, each weld should have arc ignition and extinguishing tube when the pressure is under internal pressure, usually on the tube wall to produce two main stresses, namely, the radial stress Delta Y and the axial stress Delta X. The synthesis of Y (l/4sin2 alpha +cos2 alpha) 1/2, which is the helix angle of the welded joint of the spiral welded pipe. Spiral welded pipe seam angle is 50-75 degrees, so the stress synthesis of spiral weld seam welded pipe is principal stress 60-85%. In the same work under pressure, with a diameter ratio of spiral welded pipe  wall thickness can be reduced. According to the above characteristics:DSAW steel pipe Bao Po, due to the weld is to be force and resultant stress is relatively small, Bao Po mouth is generally not originated in the spiral seam and its safety better than straight seam welded steel pipe is high.