Investigation of the Factors Having Effects on the Circumference of Spiral Pipe and Its Control

Abstract

Geometrical and physical factors having effects on the circumference of spiral pipe have been investigated experimentally. Geometrical factors such as weld seam gap, swing angle of pipe by gap controlling system and especially camber of coil after trimming have big effects on it. In order to avoid the camber after trimming, a coil walk control system has been developed and the accuracy of circumference is much improved by it. Physical factors such as yield strength of hot rolled coil and deflection of coil by forming rolls (δ) have no direct influences on it but big influences on residual stress of pipe. The change of residual stress of pipe causes a change of geometrical factors such as seam gap and/or forming angle and leads to the pipe circumference deviation. Therefore the δ must be kept constant in spiral pipe forming operation.