Using the available analytical methods, including the determination of chemical composition using wavelength-dispersive X-ray
fluorescent spectroscopy technique and phase composition determined using X-ray diffraction, microstructural observations in a highresolution
scanning microscope equipped with an X-ray microanalysis system as well as determination of characteristic softening and
sintering temperatures using high-temperature microscope, the properties of particular chromite sands were defined. For the study has been
typed reference sand with chemical properties, physical and thermal, treated as standard, and the sands of the regeneration process and the
grinding process. Using these kinds of sand in foundries resulted in the occurrence of the phenomenon of the molding mass sintering.
Impurities were identified and causes of sintering of a moulding sand based on chromite sand were characterized. Next, research methods
enabling a quick evaluation of chromite sand suitability for use in the preparation of moulding sands were selected.
The goal of this article is to application of non-silica sands based on alumininosilicates as an alternative of traditionally used chromite sand for alloyed steel and iron castings. Basic parameters as bulk density, pH value of water suspension, refractoriness, grain shape of the testing sands were evaluated. Also mechanical properties of furan no-bake moulding mixtures with testing sand were determined. Finally, the influence of non-silica sand on casting quality was evaluated via semi-scale under normal casting production for sand characterization Optimization of production process and production costs were described.
In the paper, a research on effects of baking temperature on chromite sand base of moulding sands bonded with sodium silicate is
presented. Pure chromite sand and its chromite-based moulding sand prepared with use of sodium silicate were subjected to heating within
100 to 1200 °C. After cooling-down, changes of base grains under thermal action were determined. Chromite moulding sand was prepared
with use of 0.5 wt% of domestic made, unmodified sodium silicate (water-glass) grade 145. After baking at elevated temperatures, creation
of rough layer was observed on grain surfaces, of both pure chromite sand and that used as base of a moulding sand. Changes of sand
grains were evaluated by scanning microscopy and EDS analyses. It was found that changes on grain surfaces are of laminar nature. The
observed layer is composed of iron oxide (II) that is one of main structural components of chromite sand. In order to identify changes in
internal structure of chromite sand grains, polished sections were prepared of moulding sand hardened with microwaves and baked at
elevated temperatures. Microscopic observations revealed changes in grains structure in form of characteristically crystallised acicular
particles with limited magnesium content, intersecting at various angles. EDS analysis showed that these particles are composed mostly of
chromium oxide (III) and iron oxide (II). The temperature above that the a.m. changes are observed in both chromite-based moulding sand
and in pure chromite sand. The observed phenomena were linked with hardness values and mass of this sand.
In the paper, a research on effects of baking temperature on chromite sand base of moulding sands bonded with sodium silicate is
presented. Pure chromite sand and its chromite-based moulding sand prepared with use of sodium silicate were subjected to heating within
100 to 1200 °C. After cooling-down, changes of base grains under thermal action were determined. Chromite moulding sand was prepared
with use of 0.5 wt% of domestic made, unmodified sodium silicate (water-glass) grade 145. After baking at elevated temperatures, creation
of rough layer was observed on grain surfaces, of both pure chromite sand and that used as base of a moulding sand. Changes of sand
grains were evaluated by scanning microscopy and EDS analyses. It was found that changes on grain surfaces are of laminar nature. The
observed layer is composed of iron oxide (II) that is one of main structural components of chromite sand. In order to identify changes in
internal structure of chromite sand grains, polished sections were prepared of moulding sand hardened with microwaves and baked at
elevated temperatures. Microscopic observations revealed changes in grains structure in form of characteristically crystallised acicular
particles with limited magnesium content, intersecting at various angles. EDS analysis showed that these particles are composed mostly of
chromium oxide (III) and iron oxide (II). The temperature above that the a.m. changes are observed in both chromite-based moulding sand
and in pure chromite sand. The observed phenomena were linked with hardness values and mass of this sand.
The paper presents an original method of measuring the actual chromite content in the circulating moulding sand of foundry. This type of
material is applied for production of moulds. This is the case of foundry which most frequently perform heavy casting in which for the
construction of chemical hardening mould is used, both the quartz sand and chromite sand. After the dry reclamation of used moulding
sand, both types of sands are mixed in various ratios resulting that in reclaimed sand silos, the layers of varying content of chromite in
mixture are observed. For chromite recuperation from the circulating moulding sand there are applied the appropriate installations
equipped with separate elements generating locally strong magnetic field. The knowledge of the current ratio of chromite and quartz sand
allows to optimize the settings of installation and control of the separation efficiency. The arduous and time-consuming method of
determining the content of chromite using bromoform liquid requires operational powers and precautions during using this toxic liquid.
It was developed and tested the new, uncomplicated gravimetric laboratory method using powerful permanent magnets (neodymium).
The method is used in the production conditions of casting for current inspection of chromite quantity in used sand in reclamation plant.