Influence of sand base preparation on properties of chromite moulding sands with sodium silicate hardened with selected methods

Abstract

The paper presents a research on the relation between thermal preparation of chromite sand base of moulding sands containing sodium silicate, hardened with selected physical and chemical methods, and structure of the created bonding bridges. Test specimens were prepared of chromite sand -fresh or baked at 950°C for 10 or 24 hours -mixed with 0.5 wt.% of the selected non-modified inorganic binder and, after forming, were hardened with CO 2 or liquid esters, dried traditionally or heated with microwaves at 2.45 GHz. It was shown on the grounds of SEM observations that the time of baking the base sand and the hardening method significantly affect structure of the bonding bridges and are correlated with mechanical properties of the moulding sands. It was found that hardening chromite-based moulding mixtures with physical methods is much more favourable than hardening with chemical methods, guaranteeing also more than ten times higher mechanical properties.

Archives of Foundry Engineering

“…Sodium silicate was modified by treating methyl silicone oil as a modifier to improve the moisture resistance of samples in this study. The macroscopic and microscopic analysis can be also performed to evaluate modified effect [7,8].…”

Archives of Metallurgy and Materials

“…Thus the character of the sand is changed and this effect could be a source of various casting defects as burrs, burnt-on sand etc. [8][9][10].…”