鉄凝固時の CO 気孔生成およびマクロ偏析におよぼす液攪拌の影響

概要

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Two series of experimental studies have been made of uni-directional solidification of iron for the variation of intensity of CO formation at the solidification velocity of 5mm/min : one was solidification from inductively stirred melts, and the other from quiescent melts. In the latter case a molybdenum tube was used as the susceptor of high frequency induction. The transitional concentration range for the formation of elongated blowholes was unaffected by the stirring and was found to be [%O]_t, l=0.003∿0.004 ([%C]_L=0.11∿0.13) to [%O]_t, u=0.010∿0.011 ([%C]_L=0.14∿0.17). Elongated blowholes observed in the solidified specimens were classified into three types : cylindrical, beads-like, and discrete beads-like. It was found that the formation of blowholes was unaffected by the stirring. In the case of solidification without CO formation, the effective distribution coefficient k for quiescent melts was nearly equal to one, whereas in the presence of stirring it was 0.90∿0.95. In contrast to this, in the case of solidification with the formation of CO, the stirring produced no detectable effect on k. With the onset of CO blowhole formation, k was lowered rapidly. With further increase of CO formation, k decreased slowly and tended to approach a constant value. It is shown that the present data give a reasonable explanation to macrosegregation occurring during solidification of a riming steel.
社団法人日本鉄鋼協会の論文
1975-11-01