FIELD: technological processes, casting.
SUBSTANCE: invention is related to foundry, in particular to making of sand-cement moulds. Prior to preparation of moulding mixture, Portland cement is exposed to high-temperature annealing. For this purpose Portland cement is mixed with dispersed coal in the following ratio, wt %: Portland cement 97-99; dispersed coal 1-3. This mixture is annealed for 30-55 minutes. Annealing of Portland cement mixture with dispersed coal is carried out either at pressure of 1.01·105 Pa in temperature range of 850-950°C, or at pressure of 1.33·105 Pa in temperature range of 500-850°C. In process of Portland cement annealing, gypsum is decomposed, which is the main source of gases.
EFFECT: method provides for prevention of gas pockets development in cast iron foundry goods due to reduction of gas generation in moulding mixture in process of melt casting.
1 cl, 1 tbl, 1 ex
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