Conventional roll-forming practices are used by many major steel companies for the manufacture of thin-walled ERW steel pipe. Modern trends in the pipe-rolling industry have been towards producing thinner-walled pipe with higher-strength steels. Since many of the existing conventional rolling mills were designed to accomodate heavier-walled pipe, roll forming the lighter sections can result in quality-control problems. As the sheet material, or skelp, becomes thinner its lateral stiffness decreases, increasing the occurrence of edge buckling that can reduce the overall weld quality. This manufacturing difficulty is aggravated by the lack of a theoretical model describing the strain history of the skelp during the roll-forming process. Consequently, a general understanding of the cause and cure of the problem has been difficult to achieve. This paper presents a method of describing the complex deformed geometry of the skelp material and a method of using this geometric description to define the strain state in the deformed skelp. By developing a geometric model of the deformation, based on the mill set-up parameters, a study of the factors influencing the process will be possible. This could facilitate the optimization of current forming practices and mill set-up so that the product range can be increased and the quality of the finished product improved. © 1990.
