The technical characteristics of spiral welded pipe and welded pipe

Metallurgical properties of materials

LSAW 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 pipe.

It should be noted that the coil due to rolling direction of spiral welded pipe is not vertical pipe axis (the solution depends on the pipe clamp, spiral angle) and plate rolling direction perpendicular to the axis of the steel pipe direction, therefore, anti cracking performance is better than that of spiral welded pipe straight seam steel pipe materials.

welding technology

From the welding process, welding method and uniform spiral welded pipe welded steel pipe welded pipe, but inevitably there will be a lot of T weld, so there are chances of welding defects are greatly improved, and the T-shaped seam welding residual stress of weld metal, often in three dimensional stress state, increase the possibility of cracks.

Moreover, according to the provisions of the submerged arc welding process, each weld shall be at the arc and arc quenching, but each longitudinal welded pipe in girth welding, can not meet the conditions, resulting in the arc welding defects may have more.

Strength characteristics

When the pipe is under internal pressure, two main stresses are usually generated in the pipe wall, that is, 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 welded pipe wall thickness can be reduced.