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.