MODELING OF SKELP EDGE INSTABILITIES IN THE ROLL FORMING OF ERW PIPE

Modern trends in the pipe-rolling industry have been to produce thinne r-walled pipe with higher-strength steel. However, as many of the exis ting conventional pipe-rolling mills were designed to accommodate heav ier-walled pipe, the forming of the lighter sections can lead to formi ng difficulties. As the sheet material, or skelp, becomes thinner, its bending stiffness decreases, increasing the occurrence of edge instab ilities that can reduce the overall weld quality. Recent research has developed analytical and numerical models for the prediction of the st rain history in the roll-forming process, but there has been little wo rk done on the skelp edge instability phenomenon. This paper presents an investigation of skelp edge instability in the roll forming of ERW pipe. A model has been developed to predict the skelp edge instability , based on prediction of local axial deformation, during the forming p rocess. The model reveals the relationship between the local axial def ormation and the mill set-up parameters, which can be used to assist i n adjusting the mill to eliminate skelp edge instability.