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 assumed the consolidated state of the process, however many process related aspects need still 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, tearings, pick-up, ..) can affects both the quality of the extrudate and the achievable productivity thus reducing the overall process efficiency. A solution adopted at 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 to remove heat far from the regions where the highest temperature are reached, the bearing zones. In this context, the additive manufacturing technologies offer a valid turning key allowing integrating in the dies additionally functionalities such as conformal cooling channels. 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 and AA6063 aluminium alloys confirming the efficiency of the achieved targeted cooling.