Development of an experimental model for scale growth and its application to the numerical analysis of hot forming processes

The scale is an oxide layer that grows on top of the free surface after the heating at high temperatures and following cooling of metals. During hot forming operations the oxide scale deeply influences the heat transfer and friction at the tool-workpiece interface. In order to optimize the process parameters and the quality of finished products it is very important for the manufactures to understand the growth of the scale. This work presents the results of an experimental campaign (planned using Design of Experiment techniques) aimed to investigate the scale phenomenon of a typical hot-formed steel taking in account the effects of time and temperature on the oxide layer growth. The relationship between the scale and the significant predictors has been investigated using a multivariate regression analysis. The experimental model has been used to predict different scale layers and their effects on temperature distribution at the tool-workpiece interface was investigated using a FE simulation.