Simulation of the Process of Hot Rolling of Seamless Tubes

Abstract

Seamless tubes are manufactured, as it is well known, via continuous mandrel rolling process. A billet is first pierced, then the hollow is reduced and rolled with mandrel at temperatures higher than 1000oC. After mandrel extraction, the hollow can either cool down to room temperature or be directly charged in an intermediate furnace for re-austenitization. Finally, the tube is finished in a stretch-reducing mill to several gauges. The thermomechanical process is complex allowing little flexibility along the line. The aims of this paper are a) to describe the industry schedule in terms of simple process variables and b) to simulate this process via numerical and physical models. The latter uses torsion testing as experimental technique. It is shown that good agreement is obtained between industry results and predictions from the numerical model. Torsion experiments have produced somewhat larger predictions for ferrite grains sizes, however. This is mostly attributed to the necessary simplifications made to the mechanical testing experiments due to restrictions in maximum strain rates and shortest dwell times achievable with thermomechanical simulators.