Martina Bašistová

Aluminium dross represents an important secondary raw material containing significant amounts of metallic and oxidised aluminium. The present study investigates the hydrometallurgical processing of two aluminium drosses originating from secondary aluminium alloy production, namely rotary furnace dross and post-refining dross, representing two technologically different aluminium dross streams. The materials were characterised using X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), and digital microscopy. Leaching experiments were performed using 5 wt.% NaOH, 5 wt.% KOH and 5 wt.% H2SO4 solutions at laboratory temperature. Aluminium concentrations in the leachates were determined by ICP-AES, while the solid residues were analysed by ED-XRF, XRD and SEM/EDS. The highest aluminium concentrations in the leachates were achieved using sodium hydroxide, reaching 21 800 mg·L-1 for rotary furnace dross and 25 000 mg·L-1 for post-refining dross. Lower aluminium concentrations (7 930–10 400 mg·L-1) were obtained for potassium hydroxide and sulphuric acid. XRD analysis revealed the presence of stable phases including AlN, MgAl2O4, Al2O3, CaAl12O19 and CaF2 after leaching, indicating incomplete dissolution of the original dross constituents. SEM observations confirmed substantial microstructural changes associated with partial dissolution of aluminium-bearing phases. The results indicate that, under the investigated conditions, alkaline leaching, particularly using NaOH, provides the most favourable conditions for aluminium recovery from the investigated drosses and confirms their potential as secondary raw material sources for hydrometallurgical processing.

Foundry dust is a significant component of the waste produced by the foundry industry worldwide. This waste is generated during mould making, melting, casting and discharging of moulds, where dust particles are released and subsequently captured by filters. Like most foundry waste, foundry dust usually ends up in landfills. However, this method of waste management faces problems related to environmental and economic requirements, especially in view of tightening legislation. It is important to point out that foundry dust contains components that could be reused in the production of foundry mixtures. The aim of this study is to evaluate the possible positive and negative effects of two foundry dust samples on the quality of the green sand mixtures. Basic analyses include the chemical composition of the leachate in aqueous solution and the granulometric composition of the dust particles. Furthermore, the properties of other ingredients for the preparation of green sand mixtures will be characterized. The study serves as a starting point for future research in the reuse of foundry dust in green sand mixtures, thus contributing to the sustainability of industrial processes.

This study investigates the use of steel and cast iron for producing cast furnace rolls to replace welded rolls, which often fail from cracks and limited durability. Casting had not been previously considered by the manufacturer, but rising demands for durability and quality make it a promising alternative. Material selection focused on mechanical properties, wear resistance, and production costs. To ensure casting quality, Magmasoft 6.0 software was applied for detailed simulation of casting, solidification, and cooling. Results showed that steel alloys (GS-34CrMo4 and GS-20Mn5) are prone to shrinkage and porosity, which cannot be fully avoided even with feeders. In contrast, GJS-500-7 cast iron exhibited low shrinkage tendency and minimal defects, proving suitable for production while reducing costs. It also offers lower weight and efficient metal use, improving cost-effectiveness. Detected defects were concentrated in the central casting area, where they have little impact on functionality. Based on sixteen simulations, GJS-500-7 cast iron emerged as the most suitable material for furnace rolls thanks to its thermal resistance, castability, low porosity, and ability to meet required specifications. This process optimization represents an efficient, cost-effective choice, improving final product quality and creating new opportunities for the manufacturer.

This work deals with the preparation and characterization of TiAlV/ZnAlCu composite materials. The aim is to create a model for biomaterial with good biocompatibility and acceptable mechanical properties. Infiltrating zinc into the reinforcement made of the titanium alloy could significantly improve the osseointegration of the bioimplant made from this material. The investigated reinforcements of three different geometries made from Ti-6Al-4V prepared by the SLM method (selective laser melting) were infiltrated with molten zinc or the Zn-based alloy. Two infiltration approaches were used—suction of the melt using a vacuum pump and centrifugal casting. By these procedures, different infiltration rates were achieved. Furthermore, the mechanical properties of the prepared composite materials were characterized by compression tests. The results were compared with the mechanical properties of the Ti-6Al-4V alloy reinforcement.

Quality quartz sand is globally utilized in construction due to its availability and economic factors, especially in the production of composite cements. Despite its positive properties, quartz sand also has several disadvantages. The dilation of quartz sand can be technologically significant for certain high-temperature applications. This dilation has a non-continuous character with sharp volume change caused by the phase transformation from β to α SiO₂ at temperatures around 573 °C. The extent of dilation depends on various factors such as compaction, grain size, the quantity of sand, as well as the shape and character of the grain and chemical purity, particularly the SiO₂ content. In this study, six types of quartz sand from different locations in Central Europe were examined, and the influence of chemical composition and grain shape was correlated with the final dilation of these samples. Evaluation methods included X-ray fluorescence spectroscopy (XRFS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), and linear thermal expansion analysis. It was found that angular grains, despite their chemical purity, may exhibit minimal dilation. Conversely, the least suitable combination in terms of dilation appears to be a high SiO₂ content and high roundness of grains with a smooth surface.

The quality of silica sand used in composite cements is crucial. A significant factor is the dilation of sand grains. In this study, two types of silica sands from related deposits were examined to identify differences in properties, such as grain size and shape, chemical purity (using SEM and XRFS), and their impact on dilation. It was found that the location supplying coarser-grained sand exhibited higher chemical purity but also 19.8% higher dilatation.

The quality of the castings depends, among other influences, on the quality of the moulding mixture used. The silica sands used are characterized by high thermal expansion compared to other sands. The tendency to dilatation of the moulding mixture can be influenced by the choice of the granulometric composition of the basic sand and the grain size. The aim of this work is to present the influence of grain distribution of foundry silica sand BG 21 from Biala Góra (Poland) and the degree of sorting (unsorted, monofraction, polyfraction) on the degree of thermal dilatation of the sand and thus on the resulting quality of the casting and susceptibility to foundry defects. For the purpose of measuring thermal dilatation, clay wash analysis was performed, sieve analysis of the sand was carried out, and individual sand fractions were carefully sorted. The measurements confirmed a higher thermal expansion in the case of monofractional sand grading, up to 51.8 %. Therefore, a higher risk of foundry stress-strain defects, such as veining, can be assumed.

This paper describes the technology for the production of precursors (space holder material) used to form the complex internal structure of cast metal foam. The precursor material must exhibit sufficient refractoriness, resist contact with liquid metal and at the same time should exhibit good collapsibility after casting. With regard to the greening of foundry production, the focus of this paper was on materials that could exhibit the above properties and at the same time do not have a negative impact on the environment. In this paper, the technology for the production of spherical precursors from a self-hardening mixture with a geopolymer-based binder system is described and verified. The motivation for the choice of material and all the sub-steps of the process – molding into the core box, tumbling, including the necessary accompanying tests of the mechanical properties of the core mixture being verified – are described.

The constant effort of all metal alloy manufacturing technologies and processes is to improve the resulting quality of the processed part. Not only the metallographic structure of the material is monitored, but also the final quality of the cast surface. In foundry technologies, in addition to the quality of the liquid metal, external influences, such as the behaviour of the mould or core material, significantly affect the cast surface quality. As the core is heated during casting, the resulting dilatations often lead to significant volume changes causing stress foundry defects such as veining, penetration and surface roughness. In the experiment, various amounts of silica sand were replaced with artificial sand and a significant reduction in dilation and pitting of up to 52.9% was observed. An important finding was the effect of the granulometric composition and grain size of the sand on the formation of surface defects from brake thermal stresses. The specific mixture composition can be considered as an effective prevention against the formation of defects instead of using a protective coating.