When making castings of AlSi10Mg alloy with high pressure die casting (HPDC), grain-refiner Nucleant 100 SP, based on titanium and boron is used to achieve small grain size and consequently better mechanical properties. It is added in ratio 100 g per 150 kg when the melt is melted only from ingots but when scrap material is added this ratio decreases to 100 g per 150–200 kg of melt. To spend whole melt from dosing furnace of HPDC machine it usually takes about two hours so the concentration of titanium and it´s phases is not constant because of undissolved grain-refiner or settling. In this BSc thesis, we focused on contact time after grain-refiner addition to the melt and its impact on the properties of the alloy. We made a simulation of process by sand gravity casting in Croning measuring cell without mixing the melt. AlSi10Mg alloy was melted and first poured without the addition of Nucleant 100 SP and after the addition we poured melt after 10, 20, 30, 60 and 120 minutes of contact time and in that way tried to simulate the production process. After casting and ETA analysis, whereas mainly the undercooling size was monitored, we prepared specimens for chemical analysis from which the thermodynamic calculations were made. We also made differential scanning calorimetry (DSC) analysis, microstructure analysis, and the grain size measurement.
The results of all research methods showed that the best contact time of the addition of Nucleant 100 SP in AlSi10Mg alloy is 20 minutes, when the minimum undercutting and the minimum α-Al crystal grain in the microstructure is achieved.
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