High Thermal Conductive Tool Steels for Part Quality Improvement in Permanent Mold and Die Castings of Light Alloys

This work deals with a series (HTCS^(R)) of  new tool steels,  recently developed and patented by Rovalma, S. A. Company, for the application in permanent mold and die casting of light alloys. HTCS^(R) posses a high thermal conductivity (58-62 W/mK), which is at least two times larger than this of conventional H11 and H13 tools steels, and remarkable mechanical properties. The high die thermal conductivity enhances the effective thermal conductivity and the thermal conductance at the casting-die interface. Hence the heat transfer is higher during solidification of the casting in a HTCS die. Higher heat transfer rate results in finer microstructure of solidified castings and superior part properties such as tensile strength and percentage elongation. Higher heat transfer improves also the die liftime as the extraction of heat from the casting is faster, the  die surface temperature is lower and the die cooling system is more efficient during the first stage of contact between molten alloy and die surfaces. A large experimental investigations are currently carried out,  using alternately H11 and HTCS ^(R) for the die material, on gravity and high pressure die casting of Al-Si alloys. The obtained microstructure, mechanical properties of the castings along with the heat transfer during thier solidification are closely studied for the two cases .