The difference between spiral welded steel pipe and straight seam steel pipe

The difference between spiral welded steel pipe and straight seam steel pipe:

First: welding process

From the welding process, the spiral welded steel pipe and the straight seam steel pipe are welded in the same way, but the straight welded pipe inevitably has a lot of T-weld joints, so the probability of welding defects is greatly improved, and the T-weld joint The welding residual stress is large, and the weld metal is often in a three-direction stress state, which increases the possibility of cracking. And, root

According to the submerged arc welding process regulations, each weld joint should have an arc striking and arc extinction, but each straight seam welded pipe cannot meet this condition when welding the circular joint, so there may be more arc extinguishing. Welding defects.

Second: withstand the pressure

When the tube is subjected to internal pressure, two main stresses, namely radial stress δ and axial stress δ, are usually generated on the pipe wall. The weld stress is δ, where α is the helix angle of the spiral welded pipe weld. The helix angle of the spiral steel pipe weld is generally degree, so the synthetic stress at the spiral weld is the principal stress of the straight seam welded pipe. Spiral of the same diameter under the same working pressure

The welded pipe can be reduced in wall thickness compared to the straight welded pipe.
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