A new analytical model to predict the profile and stress distribution of tube in three-roll continuous retained mandrel rolling

Abstract

To minimize the adjustments to the initial roll speed setting in tube manufacturing, both the tube profile and the tube stress distribution during the rolling are needed to be predicted before the actual rolling. While predicting the tube profile is to make the rolling reach to the metal flow balance state efficiently, predicting the tube stress distribution is to decrease the potential formation of the rolled defects caused by the non-ideal stress distribution in tube at each pass. This requires the rolling model to combine the prediction of tube profile with the prediction of stress distribution of tube in its formulation. A new analytical model which can meet the above requirements is presented in this paper. The mechanics of rolling tube in three-roll continuous retained mandrel rolling has been analyzed in the model. Validity of the model has been examined by hot rolling experiments at the plant. According to the experimental results, the predicted tube profiles are in good agreement with the measured, with the prediction errors of cross-sectional areas being in the range of 0.8∼2.5 %. The theoretical initial roll speed setting calculated based on the proposed model can be applied directly to tube manufacturing, with further adjustments at the mill being less than 4 %. The predicted roll forces calculated based on the proposed model have a maximum deviation from the measured less than 15 %. In general, the hot rolling experimental results at the plant have proved the validity of the proposed model.