Forming angle formula of spiral welded pipe

The forming angle formula of the spiral welded pipe (ssaw): The forming angle of the spiral welded pipe is an important parameter, which refers to the angle (acute angle) between the center line of the strip steel or coiled plate in the production of the spiral welded pipe and the axis of the formed spiral welded pipe. The formula is as follows: cosa =B/(πXD)

B refers to the thickness of the strip or coil, and D refers to the middle diameter of the steel pipe (the outer diameter of the steel pipe - the inner diameter of the steel pipe).
Through the formula, it is not difficult to analyze that the choice of forming angle directly affects the raw material, finished product quality and production efficiency of the spiral welded pipe.

Comparison of strength characteristics between spiral welded pipe and straight seam welded pipe: When the pipe is subjected to internal pressure, two main stresses are usually generated on the pipe wall, namely radial stress δY and axial stress δX.

The resultant stress at the weld is δ=δY(l/4sin2α+cos2α)1/2, where α is the helix angle of the weld of the spiral welded pipe. The helix angle of the spiral welded pipe weld is generally 50-75 degrees, so the composite stress at the spiral weld is 60-85% of the principal stress of the straight seam welded pipe. Under the same working pressure, the wall thickness of the spiral welded pipe with the same pipe diameter can be reduced than that of the straight seam welded pipe.

Advantages of submerged arc welding straight seam steel pipe: it can destroy the casting structure of the steel ingot, refine the grain of the steel, and unify the microstructure, so that the steel structure is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the straight seam steel pipe is no longer isotropic to a certain extent; bubbles, cracks and looseness formed during pouring. It can also be welded under high temperature and pressure.

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