Effect of Core Temperature at HPDC on the Internal Quality of the Casting

Abstract

High pressure die casting (HPDC) is one of the most productive casting methods to produce a wide range of aluminum components with high dimensional accuracy and complex geometries. The process parameters of high-pressure casting generally directly affect the resulting quality of the castings, such as the presence of pores in the casting or the microstructure. In addition to air entrapment, porosity can also be caused by the dissolution of hydrogen. Hydrogen is released by the reaction of water vapor and melt at high temperatures and is released during solidification. These defects can lead to a significant reduction in mechanical properties such as strength and ductility and especially fatigue properties. The aim of the presented article is to describe the effect of the temperature of the core of the high-pressure mold on the presence and distribution of porosity and the microstructure of the aluminum casting in two geometric variants. The temperature of the core was changed due to the use of two flowing media in the thermoregulation circuit of the core, i.e. demineralized water and heat transfer oil and worked with a core temperature of 130 ± 5 and 165 ± 5 °C. With both geometric variants, a higher porosity was achieved when using water (core temperature 130 ± 5 °C) than when using oil (core temperature 165 ± 5 °C). The opposite results were observed for microporosity, where higher microporosity was observed for tempering oil. The microstructure of the casting with water-cooled cores was more characterized by finer grains of phase α (Al) and eutectic Si. In tempering oil, the microstructure was characterized by coarse grains of the α phase (Al) and the Si lamellae were in the form of sharp-edged formations.

Keywords

• hpdc
• al-si-cu alloy
• porosity
• microstructure