Fe-C合金の凝固時における気孔生成に及ぼすSの影響

抄録

Experiments on the formation of N₂ blowholes and CO blowholes in unidirectionally solidified Fe-C alloy with various sulfur concentrations are made, and the experimental results are discussed on the basis of the interdendritic segregation model.
Sulfur enhnaces the formation of bubbles and retards the detachment of bubbles from solid-liquid interface. Consequently, sulfur enhances the formation of blowholes. This characteristic of sulfur is shown remarkably in the formation of N₂ blowholes. This effect of sulfur is attributed to that sulfur is surface active; the surface tension of iron is reduced by sulfur and the formation of bubbles in interdendritic liquid becomes easy, and the rate of the gas evolution from iron is decreased by the adsorption of sulfur on the surface of iron.
In addition, the effect of stirring of liquid phase by high frequency induction on the formation of blowholes is studied. Stirring of liquid phase depresses the formation of blowholes especially that of N₂ blowholes. This effect of stirring is attributed to the lag of enrichment of the solute in interdendritic liquid.