Stretch reduction of seamless steel tube by skew rolling and its numerical simulation

This study proposes the stretch reduction of seamless steel tubes using concave and skew rolling. This process is particularly designed to solve the hexagonal bore of the inner wall of thick-walled seamless tubes that have been subjected to stretch reduction using longitudinal rolling. A certain roller centerline angle is deflected to spirally move the tube and avoid the hexagonal bore through non-uniform local wall thickening when the tube passes through the cross. The roll deflection angle is calculated, and the expression of roller-groove curve projection is derived. Numerical simulations of stretch reduction using longitudinal and skew rolling with ANSYS/LS-DYNA, as well as comparison of simulation and experimental results, prove that stretch reduction by skew rolling is an effective solution to the hexagonal bore in the inner wall of a steel tube.