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.

Chromityty, stanowiące podstawową rudę chromu, uważane są za jedne z ważniejszych surowców strategicznych. Wykorzystywane są w różnych gałęziach przemysłu jako chromity metalurgiczne, chromity chemiczne, chromity dla przemysłu materiałów ogniotrwałych i chromity dla odlewnictwa. Chromity wydobywane są głównie ze złóż magmowych, rzadziej innego typu. Złoża magmowe tworzą dwie odmiany genetyczne - złoża typu 'podiform' związane ze skałami ultramaficznymi kompleksów ofiolitowych oraz złoża 'stratiform' powstałe w wyniku magmowych procesów wewnątrzskorupowych. Niestety Polska nie posiada własnych złóż rud chromu. Na obszarze Dolnego Śląska znane są jednak dwa wystąpienia chromitytów, zlokalizowane w skałach ultramaficznych tzw. ofiolitu sudeckiego. Traktowane są one jako nagromadzenia typu 'podiform', o charakterystycznej soczewkowej budowie ciał rudnych i wyższej zawartości Al w porównaniu z wystąpieniami typu 'stratiform'. Złoże w Tąpadłach (masyw Gogołów-Jordanów) zostało w XIX i XX wieku całkowicie wyeksploatowane (wydobyto 3500 ton rudy). Natomiast drugie wystąpienie chromitytów, zlokalizowane w masywie Braszowice-Brzeźnica, nigdy nie było przedmiotem prac badawczych. W trakcie prac terenowych w masywie Braszowice-Brzeźnica znaleziono w zwietrzelinie dużą ilość okruchów chromitytów. Badania wykazały, że są to skały o teksturach charakterystycznych dla wystąpień typu 'podiform', w dużej części masywnych i groniastych. Analizy chemiczne niezmienionych części ziaren spineli chromowych wskazują, że skład ich jest zbliżony do składu spineli typowych dla chromitów dla przemysłu materiałów ogniotrwałych. Jednak późniejsze procesy metamorficzne zmodyfikowały ich skład powodując wzbogacenie w Fe i względnie w Cr, a zubożenie w Al w stosunku do składu pierwotnego. Dodatkowo, skład chemiczny całej skały wskazuje, że chromityty z Braszowic charakteryzują się parametrami technologicznymi wykluczającymi ich wykorzystanie w stanie nie wzbogaconym. Ponadto rozmiar i ilość ciał rudnych, opisanych w XIX wieku, były niewielkie. Zarówno skład chromitytów z masywu Braszowice-Brzeźnica jak i nieznaczny rozmiar ciał nie stanowią przesłanek do podjęcia ich poszukiwań, nawet przy wysokich cenach surowców chromitowych.

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.