Fe-C合金の黒鉛形態に及ぼす硫黄と酸素の影響 Influence of Sulfur and Oxygen on Graphite Morphology in Fe-C Alloys
The present research was conducted to verify the effects of sulfur and oxygen on graphite morphologies using a Fe-C-120 massppm S mother alloy. In order to control the sulfur content in melt, three kinds of crucibles, namely, alumina, calcia, and calcia crucible with CaO-CaF<sub>2</sub> powders were used. To control oxygen partial pressure, air, argon, and Ar-3%H<sub>2</sub> atmosphere were employed. <br> After melting in the alumina crucible, only flake graphite was formed in the specimen containing 78～98 massppm S. In the case of calcia crucible, aggregated and chunky graphite were observed in the specimen containing 11～20 massppm S. The specimen melted in a calcia crucible with CaO-CaF<sub>2</sub> powders, showed spheroidal graphite with chunky graphite whose sulfur content was 1 to 11 massppm. <br> We confirmed that the spheroidal graphite is formed due to the low activity of sulfur and oxygen below critical levels. The critical levels changed with the cooling rate of samples. In addition, the cooling curve of the specimen melted in calcia crucible with CaO-CaF<sub>2</sub> powders did not show constant eutectic temperature, which is generally observed in that of flake graphite cast iron. This result is attributed to the solidification mode of spheroidal graphite, which differs from that of the flake graphite cast iron.
- 鋳造工学 = Journal of Japan Foundry Engineering Society
鋳造工学 = Journal of Japan Foundry Engineering Society 78(4), 175-180, 2006-04-25
Japan Foundry Engineering Society