Explicit FE modelling of tube stretch reduction and analysis of wall thickness variation

In order to minimise transverse wall thickness variation of seamless steel tube produced by stretch reduction, an explicit coupled thermomechanical FE model was established to simulate the stretch reduction process and corresponding experiments were carried out to validate the accuracy of the model. In addition, the plastic flow behaviour of metal in both radial and circumferential directions during forming process was analysed, and the influence of temperature on plastic flow behavior is investigated. Analysis results show that: first, the circumferential flow direction of metal is from roll groove root to roll gap in single pass rolling. Circumferential flowability of metal near the +/- 30 degrees position of the roll groove shape angle is the most active, and the circumferential flowability of metal near groove root and gap is much weaker. Second, in the entire stretch reduction process, metal flows from positions of roll groove root and gap to the +/- 30 degrees position of roll groove angle along the circumference. Third, temperature has huge influence on transverse flow behaviour. Metal temperature near the +/- 30 degrees position of roll groove shape is higher than the temperature of roll groove root and gap. This lowers the deformation resistance of the material so the flowability from roll groove root and gap positions towards the +/- 30 degrees position is strengthened, leading to the transverse wall thickness variation.