SELF-HARDENING MOULDING OR CORE SAND

A manufacturing method for self-hardening mould sand or core sand, consisting in the mixing of silica flour in the quantity of 60-75% per weight with hydrolysed ethyl silicate in the quantity of 24-39% per weight, and then with 10% water solution of ammonium bicarbonate in the quantity of 0.6-1.0% per weight, characterized in that the silica flour is tridymizated by means of adding K potassium ions and Al aluminium ions, or Na sodium ions and Al aluminium ions in the quantity of 2-10% per weight of flour, and then roasting at temperature of 900-1000 degrees C for 5-7 hours, whereas the hydrolysed ethyl silicate includes 15.9-30.1% per weight of silica, and is preferably subjected to a magnetic field.