Abstract
Partition of nitrogen between austenite and melt during solidification of hypo-eutectic iron-carbon alloys was investigated by measuring the solubility of nitrogen in the phases involved. When primary austenite crystallizes, nitrogen is rejected from the austenite to the melt at temperatures higher than about 1,320 degree C, but this partition behavior is reversed at lower temperatures. As for partition of nitrogen between cementite and austenite in nearly eutectic iron-carbon alloys, nitrogen concentrates into cementite. Nitrogen concentration in cast iron melt during solidification was calculated as a function of temperature and initial nitrogen concentration in the melt. The result indicates that, when nitrogen in cast iron melt is in equilibrium with the atmosphere, there is higher possibility of nitrogen bubbles being formed as the carbon content of the cast iron is reduced.
