鉄の一方向凝固におけるCO生成とマクロ偏析
1973 年 59 巻 7 号 p. 874-886
詳細
1973 年 59 巻 7 号 p. 874-886
Experimental studies have been made of the uni-directional solidification of iron with a view of studying the mechanism of solidification with the formation of CO. From the experiments at the solidification velocity of 5mm/min and [%C] L≈0.1, it is shown that oxygen contents of 0.003 to 0.006% correspond to the transitional concentrations for the formation of CO bubbles and macrosegregation. In this concentration range elongated blowholes are formed, resulting in lowering kc* and kp*. At oxygen contents higher than 0.006%, kp* is unaffected by the increase of oxygen concentration of the melt, whereas kc* tends to decrease at high oxygen contents.
An expression has been derived to predict the onset of constitutional supercooling for the case of solidification without the formation of CO. From the calculation, it is suggested that the solidification morphology at oxygen contents below 0.003% is dendritic structure.
The solute distribution at solid-liquid fronts growing with bubble formation is explained on the bases of the model that the enriched liquid is being pushed to the liquid ahead of the growth front. Due to the consumption of carbon in the reaction with oxygen kc* is lowered more than kp*.
It is shown that the present data give a satisfactory explanation to the phenomena occurring during solidification of a rimming steel.
