METHOD FOR ROLL FORMING STEEL PIPES, AND EQUIPMENT FOR SAME

摘要

It is an object of the present invention to provide a novel roll-forming method for steel pipes and equipment for same with which (1) the evidence that forming work in the FF forming method is mainly carried out at the cluster forming portion showing the poor formability is modified and improved without any deteriorating the advantage of the common-utilization of rolls in the FF forming method which employs basically the circular-bend method, and (2) the forming function at the breakdown forming portion is enhanced. Accordingly, the pinch-point formed by the upper and lower rolls is set at a boundary area between the target forming zone in the material's width direction and previously-formed zone or un-formed zone. The target forming zone is wound around a certain caliber of the upper roll on the bend-inner side, and bend-formed in such a way that the target forming zone is almost in non-contact with the lower roll. As a result, the formability is remarkably improved and occurrences of roll flaws and roll marks or buckling can be prevented.