the differences between straight seam welded pipe and spiral welded pipe

According to welding methods, the welded steel tubing is generally divided into two types: straight seam welded pipe and spiral welded pipe.

The Difference Between Straight Seam Welded Pipe and Spiral Welded Pipe:

Welding Process
For the welding process, welding methods of the spiral welded pipe and straight seam welded pipe is consistent, but straight seam welded pipe inevitably has a lot of T-shaped weld on the surface. So the probability of weld defects is also greatly improved and the T-shaped seam welding residual stress is larger. And the stress state of the weld metal are often in a three-way increased the possibility of crack. According to the regulations, during the submerged arc welding process, each weld seam has arc, when weld girth, each straight seam welded pipe can not meet the conditions, maybe there are more arc welding defects.

Strength Characteristics
When the pipe withstand pressure, the pressure includes radial and axial . Synthetic weld stress, where is the helix angle of the spiral welded pipe. Spiral welded seam degree helix angle is generally synthetic, and spiral welded longitudinal stress is the main stress. Under the same operating pressure, spiral pipe of the same diameter can be reduced compared with the longitudinal wall thickness.

Hydrostatic Burst Strength
The spiral welded pipe and longitudinal yield pressure and burst pressure is measured value is matched with the theoretical values by the relevant comparison test. However, whether it is the yield stress or burst pressure, is lower than the longitudinal spiral welded. And burst test also shows the rate of deformation ring spiral welded pipe bursting longitudinal significantly is greater than the mouth. It is confirmed that spiral welded is less than plastic deformation longitudinal. The blasting mouth generally is confined to a pitch which is the extension of the spiral weld to rip from a strong binding effect due.

Toughness and Fatigue Strength
The trend of pipeline development is larger diameter and high pressure features. With the increasing of the pipe diameter and the steel grade, the greater the ductile fracture tip steady expansion trend. Although spiral welded pipe and straight seam welded pipe have the same level, spiral welded pipe is with high impact toughness. Transmission pipelines due to the amount of change in the actual operation, is subjected to random alternating load effect.