Die soldering: Effect of process parameters and alloy characteristics on soldering in the pressure die casting process

Die soldering has been a major cause for concern in the aluminium metal mould casting industry for the past few years. In recent times, this defect has posed a major concern because of the notable decrease in productivity and efficiency of casting operations. Due to the high affinity that aluminium has for iron, a vigorous physio-chemical reaction occurs at the die/molten metal interface when aluminium melt comes into direct contact with the ferrous die. This reaction results in the immediate formation of a series of iron-aluminium-silicon inter-metallic compounds over the die surface and eventually the cast metal sticks to this inter-metallic layer. The casting parameters, such as the temperature of the melt, the alloy chemistry and the die pre-heat play a significant role in causing soldering. In this study, the critical process parameters affecting soldering have been identified and studied. The effect of seven alloying elements in aluminium 300 series alloy, their interactions, cycle time and temperatures of melt and die have been quantified through various experiments. The experiments were performed in a laboratory environment on an apparatus designed to simulate the harsh casting conditions under which soldering occurs. All the results and conclusions have been verified and validated in several production facilities. Recommendations to mitigate soldering have been proposed based on our conclusions.