A SIMPLE-MODEL FOR CONVENTIONAL HOT-ROLLING OF SHEET MATERIALS

Temperature transients during the bare hot rolling of sheet materials have been modeled using a simple one-dimensional, finite-difference he at-transfer approach. The model addresses heat losses associated with (1) the transfer of the sheet from the reheat furnace to the rolling m ill and (2) the actual rolling operation itself. The former step compr ises heat losses primarily through radiation and the latter through ch illing of the hot workpiece in contact with the cooler rolls. The prin cipal output of the model is the temperature field through the thickne ss of the sheet. The usefulness of the model was gaged through an inve stigation of the effect of temperature transients on the hot-rolling b ehavior of Ti-6Al-4V sheet. Specifically, the effect of temperature tr ansients on rolling pressure and development of nonuniform microstruct ure was determined. Over the entire temperature range studied, the rol ling pressure for Ti-6Al-4V was found to be dependent only on the aver age temperature of the workpiece within the roll gap, irrespective of metastable phase transformations that may have accompanied the deforma tion process itself. The one-dimensional heat-transfer model was also successful in explaining the occurrence of the nonuniform microstructu res produced during rolling at nominal (furnace) temperatures near the beta transus.