Experimental evaluation and FE simulation of thermal cycles at tool surface during cooling and deformation phases in hot and warm forging operations

In hot and warm forging operations, surface layers of tools at the tool-workpiece interface are not only exposed to high mechanical stresses but also to severe temperature cycles, which often lead to loss of strength and hardness and thermal fatigue failure as well. This paper offers an approach for determining heat transfer conditions at the surface of punches and dies during both the deformation and the cooling-lubrication phases of forging cycles. The approach is based on temperature readings inside the tool, FE simulation and inverse analysis. An application case is illustrated where operating conditions reproduce hot forging of turbine airfoil sections.