Fe
3C in white cast iron of Fe-C system fuses at 1,143°C as Fe
3C eutectic without graphitization of the Fe
3C even at a slow heating rate 0.625°C/min. Graphite eutectic solidifies in the melt. The amount of the solidifying eutectic decreases as the heating rate is speeded up. This eutectic fuses at 1,153°C. The graphite structure in grey iron hardly changes by heating, and only the melting of graphite eutectic is detected on the differential thermal analysis curve. Parts of Fe
3C eutectic and graphite eutectic in mottled iron behave as independent white and graphite irons. Fe
3C in white iron of Fe-C-Si system containing Si up to 0.12% fuses as Fe
3C eutectic without being graphitized. The amount of the fusing Fe
3C eutectic decreases with 0.17% Si, because graphitization of the Fe
3C increases with the decreased heating rate. The amount of graphite eutectic solidified in the melt increases. Fe
3C is completely graphitized with Si 0.39% or more even at the high heating rate 20°C/min. The graphitization of Fe
3C occurs at lower temperatures as Si is increased and the heating rate is reduced. The graphite particles become finer and increase in number as the Si content and heating rate increase.
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