Experimental Analysis of Heat Transfer at the Interface between Die Casting Molds and Additively Manufactured Cooling Inserts

Abstract

The rate of heat transfer to the mold during solidification determines the cooling rate of castings, which significantly impacts their characteristics. The use of an insert produced by additive manufacturing in the mold, with appropriately designed cooling channels, enables adequate cooling control of the entire piece. This article investigates the heat transfer properties at the interface between two types of steel used for die casting molds (steel A) and additively manufactured cooling inserts (steel B). The study analyzed the impact of coolant water flow rate channel (215, 300, and 425 mL/min.) and contact pressure between the two types of steel (0, 15, and 30 bar) on the thermal behavior of the mold/insert assembly in both transient and steady states. The time constants of the system associated with the coolant flow rate transitions from 215 to 300 mL/min and from 215 to 425 mL/min were determined during the transient mode. The findings indicated that increasing the proximity of the cooling channel to the interface, coolant flow rate, and contact pressure resulted in a faster cooling response in the transient state. For the tested conditions, the determination of thermal contact resistance (TCR) was carried out in the steady state. The TCR values were affected by the contact pressure between the two steel pieces, showing, with an increase of 30 bar, a decrease of 21% and 33% for cooling channels located at 6.5 and 9.5 mm from the interface, respectively. Within the tested range, the TCR values were not significantly affected by variations in cooling flow rates. Lower TCR values were observed when the cooling channel was positioned closer to the interface (~ 28%). The study provides valuable insights into the factors affecting thermal contact resistance and process parameters. It can aid in optimizing cooling insert design for casting molds, namely by numerical analysis.