Carbon equivalent of cast iron is known as the following equation: CE = [%C] + (1/3) [%Si]. This equation is basically calculated from the carbon solubility in hypereutectic composition. On the other hand, liquidus from hypoeutectic to eutectic composition in Fe–C phase diagram is well known. Liquidus temperature (hereinafter referred to as T_L) can be measured easily with thermal analysis by focusing primary crystallization temperature. In this study, the effects of elements on T_L and carbon equivalent in cast iron were examined from the view point of cooling curve, carbon flotation, and internal shrinkage, and a more accurate equation for calculating carbon equivalent is suggested. It is revealed by the experiment that the relationship between T_L and elements from hypoeutectic to eutectic composition is as follows; T_L (°C) = 1625 − 110 [%C] − 25 [%Si] + 3 [%Mn] − 35 [%P] − 71 [%S] − 2 [%Ni] − 7 [%Cr]. Dividing this equation by carbon coefficient, the carbon equivalent equation of liquidus (hereinafter referred to as CE_L) from hypoeutectic to eutectic composition is obtained as follows: CE_L = [%C] + 0.23 [%Si] − 0.03 [%Mn] + 0.32 [%P] + 0.64 [%S] + 0.02 [%Ni] + 0.06 [%Cr]. This CE_L is different from the commonly used CE since it is determined from liquidus. We investigated how the difference of carbon equivalent (CE/CE_L) application in the range of hypoeutectic to eutectic composition affected on the cast iron and revealed that CE_L = [%C] + 0.23 [%Si] should be applicable.

中文翻译：

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碳饱和度与液相线碳当量之差的研究

铸铁的碳当量称为以下方程式：CE = [％C] +（1/3）[％Si]。该方程基本上由过共晶组成中的碳溶解度计算得出。另一方面，Fe–C相图中从次共晶到共晶组成的液相线是众所周知的。液相线温度（以下，称为Ť_大号）可以很容易地用热分析通过聚焦初晶温度来测量。在这项研究中，从冷却曲线，碳浮选和内部收缩的角度研究了元素对铸铁中T _L和碳当量的影响，并提出了一个更精确的碳当量计算公式。实验表明，T之间的关系_L和从亚共晶到共晶组成的元素如下：T _L（°C）= 1625-110 [％C]-25 [％Si] + 3 [％Mn]-35 [％P]-71 [％S]-2 [％Ni]-7 [％Cr] 。通过将该方程除以碳系数，可以得到从亚共晶成分到共晶成分的液相线的碳当量方程（以下称为CE _L）：CE _L  = [％C] + 0.23 [％Si]-0.03 [％Mn] + 0.32 [％P] + 0.64 [％S] + 0.02 [％Ni] + 0.06 [％Cr]。该CE _L与通常使用的CE不同，因为它是由液相线确定的。我们调查了碳当量的差异（CE / CE _L）在影响铸铁的亚共晶至低共熔成分范围内的应用，并表明CE _L  = [％C] + 0.23 [％Si]应该适用。