Additive Manufacturing of H-13 Inserts for Optimal Extrusion Die Cooling

The hot extrusion process is a widespread manufacturing technology selected to produce sound profiles of almost any complex section. Even when the consolidated state of the process is assumed, however, many process-related aspects still need to be completely solved, such as those related to the high temperatures involved. Many defects can indeed arise consequently to the heat generated for the work, spent to overcome friction at the tool/workpiece interfaces and to plastically deform the material, as well as to the set pre-heating temperatures. These defects (hot cracks, tearing, pick-up) can affect both the quality of the extrudate and the achievable productivity, thus reducing the overall process efficiency. A solution adopted at the industrial level is the use of liquid nitrogen cooling supplied by means of a channel manufactured on the mating face of the die with the backer. However, this has the main drawback of removing heat far from the regions where the highest temperatures are reached, the bearing zones. In this context, the additive manufacturing technologies offer a valid turning key, allowing integrating in the dies of additional functionalities, such as conformal cooling channels. The aim of the present work was the design and the selective laser melting (SLM) manufacturing of an H-13 insert for extrusion dies with a conformal cooling channel. To support the design phase, numerical simulations have been carried out by including liquid nitrogen. Finally, experimental tests were successfully performed on ZM21 magnesium (Mg) and aluminum alloy (AA) 6063, confirming the efficiency of the achieved targeted cooling.