Application of High Thermal Conductivity Steels to Automotive Aluminum Die-Cast Molds 2007-01-1221

In recent years, the use of aluminum die cast parts in automobile manufacturing has increased due to greater demand for automotive weight reduction. For even wider application, it is necessary to reduce manufacturing costs and improve product quality. Finite element method (FEM) analysis suggested that a new material, featuring 50% improved thermal conductivity within the working temperature of the die compared to the conventional 5% chromium hot work tool steel AISI-H13 (H-13), would decrease thermal stress on the die surface and lower the maximum surface temperature. As a result, the reduced stress should increase the die service life with respect to heat checks. At the same time, the reduced surface temperature should increase the cooling rate of die cast products, which will in turn improve product quality due to finer structure formation.

In this research, a new die material, with thermal conductivity an average of 50% greater than the conventional H-13, was developed and the mechanical properties were examined. As a result, mechanical properties very similar to the conventional material were seen, and thus, use in die casting dies is thought to be possible. Surface temperature variations and product quality of the conventional material (H-13) and the new material (HDS-1) were compared, by using HDS-1 for the water jacket core of an engine block die for a high-pressure die casting machine and a cylinder head die for a low-pressure die casting machine. Through this comparison, the surface temperature of the HDS-1 die was found to decrease more quickly, leading to die cast products with finer structures in the areas close to the surface contacting the die.