Dehydroxylation of Perlite and Vermiculite: Impact on Improving the Knock-Out Properties of Moulding and Core Sand with an Inorganic Binder

The article presents the results of research aimed at examining the type of swelling material introduced into moulding or core sand to improve their knock-out properties. Tests on Slovak perlite ore (three grain sizes), Hungarian perlite ore and ground vermiculite (South Africa) were carried out. For this purpose, thermal and structural analyses (FTIR—Fourier Transform Infrared Spectroscopy), a chemical composition test (XRF-X-Ray Fluorescence), phase analysis (XRD—X-Ray Diffraction), and scanning electron microscopy (SEM—Scanning Electron Microscope) as well as final strength tests of moulding sands with the addition of perlite ore and vermiculite were carried out. The results of thermal studies were related to IR (Infrared Spectroscopy) spectra and XRD diffractograms. It has been shown that the water content in the pearlite ore is almost three times lower than in vermiculite, but the process of its removal is different. Moreover, the chemical composition of the perlite ore, in particular the alkali content and its grain size, may influence its structure. The phenomena of expansion (perlite) and peeling (vermiculite) have a positive effect on the reduction of the final sand strength and eliminate technological inconveniences (poor knocking out) that significantly limit the wide use of moulding sands with inorganic binders.

Implementation of Nanoparticles in Materials Applied in Foundry Engineering

The ceaseless progress of nanotechnology, observed in the last years, causes that nanomaterials are more and more often applied in several fields of industry, technique and medicine. E.g. silver nanoparticles are used in biomedicine for disinfection and polymer nanoparticles allow insulin transportation in pharmacology. New generation materials containing nanoparticles are also used in the chemical industry (their participation in the commercial market equals app. 53 %). Nanomaterials are used in electronics, among others for semiconductors production (e.g. for producing nanoink Ag, which conducts electric current). Nanomaterials, due to their special properties, are also used in the foundry industry in metallurgy (e.g. metal alloys with nanocrystalline precipitates), as well as in investment casting and in moulding and core sand technologies. Nanoparticles and containing them composites are applied in several technologies including foundry practice, automotive industry, medicine, dentistry etc. it is expected that their role and market share will be successively growing.

POSSIBILITY OF APPLICATION OF SODIUM SILICATE IN MOULDING AND CORE SAND MIXTURES IN ART CASTING

The environmental issues come to the forefront in the 21st century. The 2017th year is announced in Russia as the year of ecology. The possibilities of application of sodium silicate and phosphate binder for production of large forms and cores in machine-tool industry are considered in the article.

Effect of Sulfur on the Formation of the Graphite Degradation in Ductile Iron

The objective of this study is to evaluate the effect of sulfur in core sand on the formation of the graphite degradation in ductile iron. The graphite degradation is caused by the depletion of Mg in liquid iron resulting in low nodularity zone underneath the casting surface. The content of sulfur in molding materials has been known as an important factor of the occurrence of the graphite degradation. It was found that the greater content of sulfur in the core sand promoted the formation of the graphite degradation. The graphite degradation with the thickness ranged from 113 to 1116 μm was observed for the sulfur content from 0.24 to 1.68 wt%S.

Effects of core sand type and heat treatment on solid particle erosion of core box AISI H13 tool steel

The paper reports on investigations into the erosion, microstructural features, and material removal mechanisms of AISI H13 core boxes eroded by two types of core sand (silica and chromite). Different heat treatment operations are carried out, namely martempering, carbonitriding, quenching, and tempering, in order to vary hardness, microstructure, and surface morphology. Scanning electron microscopy inspections show that erosion is not only a function of surface hardness of the target material but also of its microstructure. Erosion of martensitic microstructure, consisting of very fine carbides with a uniform martensitic substructure, is much less severe than erosion of a material characterized by dispersed coarse carbide. Hardness effects on the erosion process are discussed in terms of material removal modes.