Abstract This study presents an experimental and exploratory evaluation of the influence of flux composition on the melt quality and casting fluidity of secondary AlSi7Mg0.3 aluminum alloys. Four distinct melt conditions were investigated, including a flux-free reference and three flux compositions based on MgCl 2 –KCl with varying NaF–KF additions. Melt quality was assessed through Density Index (DI) and K -mold inclusion tests, while casting behavior was evaluated using both a spiral and a four-strip sectioned (2–8 mm) fluidity molds. The results showed that optimized flux composition led to a significant reduction in DI—6.31–1.21% and in K -values—2.6 to 0.4—indicating effective hydrogen degassing and oxide removal. These improvements translated into a spiral fluidity increase from 58 to 177 mm (≈ 205%), and a 400% enhancement in 2 mm strip flow length, demonstrating a direct link between melt cleanliness and casting fill performance. A multivariate regression model relating DI and K -values to spiral fluidity yielded a determination coefficient of R 2 ≈ 0.85 with a mean absolute percentage error (MAPE) of 12.49%, supporting the potential for integrated quality prediction even with a limited dataset. Although exploratory in nature, the findings emphasize the critical role of flux composition in improving both internal melt integrity and functional casting outcomes. The study also highlights the diagnostic potential of four-strip sectioned mold, rarely addressed in the literature, as a sensitive indicator of melt behavior in geometrically constrained conditions. The integrated approach presented here offers a practical framework for optimizing flux selection and evaluating melt quality in secondary aluminum casting processes.

Abstract A new user function was developed to simulate carbon macrosegregation in medium to large-sized steel ingots, derived for use in the post-processing stage of casting simulations. This new proposed formulation accounts for critical parameters such as cooling rate, thermal gradient, and ingot geometry, and can be implemented within commercial simulation software to estimate steel carbon content. The methodology was first applied to an industrial-scale 36-tonne ingot, comparing simulation and experimental analyses. Characterisation of the industrial ingot, performed by sectioning and chemical analysis, showed good agreement between the carbon segregative index values predicted by the user function and those experimentally measured. To further assess the reliability of the model, a second case study was conducted on a 40-tonne ingot using the same approach. The results confirmed the predictive capability of the developed function, which can be effectively employed to evaluate carbon macrosegregation in medium to large-sized ingots, particularly for medium- to low-alloy steel grades. Graphical Abstract

Abstract Ductile irons (spheroidal graphite cast irons, SGI) are widely used in automotive and energy systems due to their high strength, ductility, and excellent machinability. The casting quality of these alloys largely depends on the flow and filling behavior of the molten metal, namely its fluidity. In this study, the effects of pouring temperature, filling time, and metallurgical quality on the fluidity of GGG40 ductile iron were investigated through both experimental and numerical approaches. Experimental trials were conducted at pouring temperatures of 1350 °C, 1400 °C, and 1450 °C; metallurgical quality levels of 10%, 50%, and 90%; and filling times of 5 s and 10 s. The fluidity lengths were measured and statistically evaluated. The results revealed that increasing the pouring temperature and metallurgical quality significantly improved fluidity, while shorter filling times allowed the molten metal to travel longer distances before solidification. Modeling studies performed using a commercial casting simulation software showed strong correlation with the experimental data. Microstructural examinations indicated that higher pouring temperatures and improved metallurgical quality led to a more homogeneous distribution of graphite nodules and an increased ferrite fraction in the matrix. The findings provide valuable insights into the influence of process parameters on the fluidity behavior of ductile iron and offer critical design data for enhancing casting quality and productivity in industrial foundry applications.

Abstract In metal casting, creating undercuts in components requires cores, typically made from sand–binder mixtures such as environmentally friendly sodium silicate binders. For intricate geometries like cooling channels, higher binder content is used to achieve sufficient core strength. However, removing inorganic-bound high-strength sand cores mechanically without residue remains challenging, limiting cavity complexity in thin-walled aluminum parts. This research develops an alternative process chain for aluminum gravity casting, using sodium chloride (NaCl) salt without binding agents as the core material in the core shooting process. Moist salt powder is fluidized with compressed air and injected into a mold, where crystallization—controlled by moisture content and drying—yields a stable, temperature-resistant core. After casting, the water-soluble cores are removed and can be recycled, eliminating harmful emissions and worker exposure to respirable dust. This study examines the influence of core-shooting parameters and in-mold drying on the three-point flexural strength of porous salt cores. Increasing the fine-particle fraction is found to enhance strength, and complete drying is essential. Binder-free, salt-based cores provide superior surface quality and sufficient strength for gravity casting and can be removed either dry or by washout with water. Future work will focus on strengthening the cores to meet typical sand casting standards and reducing the crystallization process time.