Plug temperature effects on the billet formability during seamless tube piercing process

Seamless tube piercing is sensitive to the thermal state of the plug, yet the influence of plug temperature on tube geometry during Mannesmann-type piercing is not well quantified. In this study, plug temperatures of 500 °C, 700 °C and 900 °C are analysed using a three-dimensional thermo-mechanical finite element model, complemented by pilot-scale measurements from an industrial line for validation at 500 °C. The simulations resolve heat transfer at the plug–tube interface and its effect on material flow, wall thinning and twist. Across the investigated range, tube length increased by about 2.5 % per 100 °C rise in plug temperature, while wall thickness decreased by about 5 % per 100 °C. Higher plug temperatures also enhanced surface twisting and reduced internal twisting, consistent with shifts in velocity gradients through the wall, and led to an increase in drive energy demand. The results link temperature-dependent flow stress and heat transfer to the observed changes in tube geometry and process energy consumption in seamless tube piercing.