Prediction of Graphite Nodule Count and Shrinkage Tendency of Spheroidal Graphite Cast Iron by One Cup Thermal Analysis

抄録

Three cup thermal analysis is a good method for predicting chill depth, tensile strength and graphite type in gray cast iron. However, it cannot be used in ductile cast iron due to several reasons. For this reason, we have developed a method for investigating the graphite eutectic temperature (hereafter T_EG) and cementite eutectic temperature (hereafter T_EG) in ductile cast iron, from the chemical composition of the molten metal, as follows;

T_EG = 1149.1(℃) + 4.7Si% − 4.0Mn% − 44P% + 2.7Cu% + 1.0Ni% + 1.8Co% + 13.9Al% − 17.7Mo% − 10.5Cr% − 9.3Sn% − 5.2Sb% − 6.1W% − 3.7Nb% − 14.8V% − 80.3B%

T_EC = 1142.6(℃) − 11.6Si% − 0.75Mn% − 46.2P% − 1.4Cu% − 1.1Ni% − 0.7Co% − 1.8Al% − 14.5Mo% + 5.9Cr% − 6.0Sn% − 5.1Sb% − 2.8W% + 0Nb% + 3.3V% − 26.0B

Using the cooling curve of 1 cup and the above equations, we calculated eutectic graphitization ability (hereafter EGA). We investigated if this one cup thermal analysis can be used to predict the quality of molten metal (graphite nodule count and shrinkage tendency) correctly even in ductile cast iron, before it is poured.

The graphite nodule count (N) of CE cup T.P. is determined by EGA(= ΔT₁ × 100/ΔT_E) as follow; N = 6.13 × (ΔT₁ × 100/ΔT_E) − 126 In addition, when EGA exceeds 90%, the shrinkage tendency parameter (θ) becomes low near 55° which is that of gray cast iron. Consequently, one cup thermal analysis is a good system for predicting the quality of molten metal (graphite nodule count and shrinkage tendency) correctly in ductile cast iron before pouring.

 

This Paper was Originally Published in Japanese in J. JFS 89 (2017) 332–337.