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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 7, Number 1
February 20, 1963 

Study on the Spheroidizing Mechanism of Graphite in Cast iron (part 1)
Hyung Sup Choi, Ji Yung Chang
보통 적철은 석철흑연이 편상으로 되어 있어 그 기계적 성질이 약하다. Magnesium이나 Cerium 등의 nodulizing element를 가했을 때에는 흑연이 구상화되어 늑성 또는 연성이 증가되며 충격등으 외력이 대한 내력이 좋아진다. 그러나 아직 흑연의 구상화 기구를 포괄적으로 설명할 수 있는 이론은 확립되어 있지 않으며 Mg나 Ce 등 nodullizing element의 『 핵작용에 의한다는 설』『흡착설』『계면에네르기 설』 등에 의한다는 설』『흡착설』과 『계면에네르기 설』 등 많은 학설이 있으나 결국 어떠한 경로를 밟았든 흑연이 적철내에서 구상화 되었다는 흑연과 지금의 wettability가 가장 나쁜 상태라고 판단할 수 있다. 저자는 이와 같은 판단을 실증하기 위하여 제일단계로서 wettability 측정용 진공아크로를 제작하고 진공 또는 질소가스기위에서 철과 흑연의 접촉각 및 철과 Mg를 흡착한 흑연간의 접촉각을 측정 비교하였는데 양자간에는 현저한 차가 있음을 발견하다. 이것은 장시일을 두고 해결해야 할 흑연 구상화 모양 구명의 제일보이며 새로운 연구 방향을 개척해 나가는데 지침이 될수 있을 것이다.

It is well known that the graphite flakes become spherulite, when a suitable amount of nodulizing element, such as cerium or magnesium, is added to the cast iron. The change of graphite from flake to nodular shape improves not only the tensile strength but the ductility as well. However, the mechanism of spheroidization of graphite in cast iron has not yet been clearly understood, and various theories proposed by a number of investigators were such that it may be due to the special nucleation effect, prevention of flake formation by the adsorption of magnesium vapour on the graphite surface or file surface free energy difference between plain graphite and magnesium-adsorbed graphite. Regardless of the speculations of spheroidizing mechanism of the graphite in the cast iron, the final phenomenon comes to the conclusion that it may be due to the lack of wettability between graphite and iron matrix. In order to collaborate this fact through an experimental method, the authors have constructed a vacuum arc furnace for the wettability measurement as its first step. Our study and experiments were then directed to the comparison of the wettabi]ity between iron and graphite on the two cases (namely, the one where magnesium was preliminarily coated on the graphite surface and the other not coated), by means of contact angle measurements. The result was such that a significant difference of the contact angles has been shown between the above two cases. indicating the spheroidization of graphite which might have resulted from the lack of wettability between magnesium-adsorbed graphite and iron matrix.

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