The forming angle refers to the sharp angle at which the centerline of the steel pipe intersects the horizontal projection of the centerline of the steel strip, usually expressed in α. The forming angle is the most important parameter in the forming process of spiral seam double-sided submerged arc welded pipe, which not only represents the angle at which the center line of the steel pipe should be tilted against the center line of the steel strip, but also determines the position of the unit on the rolling line, which is crucial for the reasonable matching of the diameter of the steel pipe and the width of the steel strip. When the forming angle < 90°, spiral forming can be formed, and spiral forming is the result of the functional relationship between B, D, and α:
D= B/ π cos α
