DOE techniques applied to the modelling of scale in hot forging and relevant effects on temperature distribution and forging load in the tooling system

Scale is an oxide layer that grows on the free surface of metal components during heating at high temperatures. During hot forging operations the oxide scale deeply influences heat transfer at the tool-workpiece interface. In order to optimise process parameters and the quality of finished products it is very important for manufacturers to understand scale growth. This work presents the results of an experimental campaign (planned using Design of Experiments techniques) aimed at investigating the scale phenomenon on typical hot-forged steel considering the effects of time and temperature on the oxide layer growth. The thickness of scale response has been described using a first-order model. The experimental model has been used to predict different scale layers and their effects on temperature distribution at the tool-workpiece interface and the forging load was investigated using a FE (Finite Element) simulation.