Abstract
The present paper deals with the experimental study made of the uni-directional solidification of iron with blowhole formation at various solidification velocities ranging from 5 to 13.5mm/min and [%C]L≈0.1. It is found that the lower limit of the transitional oxygen concentration, [%0]t, 1, for the formation of elongated blowholes is 0.003-0.004% and almost independent of solidification velocity ƒ. On the other hand, the upper limit of the transitional concentration, [%O]t, u, increases with increasing ƒ until ƒ=10mm/min is reached, beyond which [%O]t, u tends to decrease.
On the bases of the equilibrium solidification model, an attempt has been made to calculate the lower limit of the transitional oxygen concentration. The calculation is in good agreement with the experimental findings.
The relationship found between the upper limit of the transitional concentration and solidification velocity is interpreted in terms of the relative rates of growth of the bubble and of advance of the interface.
A series of experiments has been made of solidification from the iron melt in equilibrium with CO-CO2 gas mixtures. It is shown that both kp* and kc* increase with the increase of solidification velocity.
