2019 Volume 60 Issue 9 Pages 1983-1988
Generally, carbon equivalent is calculated with the following equation; CE = [%C] + (1/3) [%Si]. However, the value calculated with chemical analysis method such as emission spectrochemical analysis is different from that calculated with the primary crystal temperature (Hereafter TL) of the CE meter. In this study, the influence of elements on primary crystal temperature and carbon equivalent in cast iron was examined, and a more accurate equation for calculating carbon equivalent was suggested.
The relationship between the various element content and TL from hypo-eutectic to eutectic composition is as follows; TL (°C) = 1625 − 110 [%C] − 25 [%Si] + 3 [%Mn] − 35 [%P] − 71 [%S] − 2 [%Ni] − 7 [%Cr] Dividing this equation with carbon coefficient, a carbon equivalent equation from hypo to eutectic composition is obtained, as follow; CEL = [%C] + 0.23 [%Si] − 0.03 [%Mn] + 0.32 [%P] + 0.64 [%S] + 0.02 [%Ni] + 0.06 [%Cr]. This is calculated from the drop in the solidification temperature and is different from the generally used CE = [%C] + (1/3) [%Si]. We investigated which causes the difference and which is more correct from hypo to eutectic composition.
From the review of references, it is assumed that CE = [%C] + (1/3) [%Si] is calculated from the carbon solubility in hyper-eutectic composition. Compared to this, as for the references in which carbon equivalent are calculated from the solidification temperature from hypo to eutectic composition, Si coefficient is not (1/3) but 0.22 to 0.25.
From all the following viewpoints, it can be said that CEL = [%C] + 0.23 [%Si] is more correct than CE = [%C] + (1/3) [%Si]: (a) experimental result, (b) cooling curve of CE meter, (c) carbon floatation result, (d) TL and chemical analysis, (e) internal shrinkage test result, and (f) thermodynamic simulation with JMatPro. The silicon coefficient (α) is constant as 0.23 until 3.65% silicon, but it increases linearly if the silicon content exceeds 3.65%.
This Paper was Originally Published in Japanese in J. JFS 91 (2019) 87–93. Figure 12 was slightly modified.
