In spiral welded pipe technology, forming angle is an important parameter, which refers to the angle (acute angle) helical axis of spiral welded steel production (tube) after welding and forming the center line between it and the strip (tube) width, coil diameter, stress and productivity have a certain relationship. 

Relationship with the strip forming angle (tube) width and diameter spiral welded pipe 
Under certain circumstances the width of the strip, forming angle changes directly affect changes in pipe diameter, while the diameter of the steel pipe of the same strip of different widths can be used, the use of different molding angle molding. From the production feasibility and economic considerations, strip width and pipe diameter ratio is a certain boundary and scope. From an economic consideration, forming angle smaller productivity is higher, if a 30 °angle than molding molding using 50 °angle to produce the same yield about a quarter the diameter of the pipe. From feasibility is concerned, after forming angle is too poor roundness minor type steel, steel quality is poor. 

Relationship molding angle and weld stress 
Spiral weld seam is exposed to stress smaller than straight, just straight seam of 75% -90%, and therefore able to withstand greater pressure. Longitudinal compared with the same diameter, wall thickness can be reduced by 10% -25%. Thus, in determining the wall thickness of the radial stress is the determining factor. Angle between the longitudinal direction on the straight line tangent to the cylinder surface of the tube formed by the helical seam angle is formed.