Abstract
Abstract The paper presents a solidification sequence of graphite eutectic cells of A and D types, as well as globular and cementite eutectics. The morphology of eutectic cells in cast iron, the equations for their growth and the distances between the graphite precipitations in A and D eutectic types were analyzed. It is observed a critical eutectic growth rate at which one type of eutectic transformed into another. A mathematical formula was derived that combined the maximum degree of undercooling, the cooling rate of cast iron, eutectic cell count and the eutectic growth rate. One type of eutectic structure turned smoothly into the other at a particular transition rate, transformation temperature and transformational eutectic cell count. Inoculation of cast iron increased the number of eutectic cells with flake graphite and the graphite nodule count in ductile iron, while reducing the undercooling. An increase in intensity of inoculation caused a smooth transition from a cementite eutectic structure to a mixture of cementite and D type eutectic structure, then to a mixture of D and A types of eutectics up to the presence of only the A type of eutectic structure. Moreover, the mechanism of inoculation of cast iron was studied.
Highlights
Cast iron is the most important and most widely used casting alloy and its inoculation phenomenon was discovered in 1920 [1] and patented by Meeh in 1924 [2]
The appearance of skeletons in the graphite eutectic cells of A and D types are shown in Fig. 1a,b while microphotographs of their cross–sections are given in Fig. 1c, d
D type eutectic λ 16,1 u 0,25 ; m. The graphs of these equations indicate a discontinuity within the interface distance between the A and D types of graphite eutectic structure (Fig. 3)
Summary
Cast iron is the most important and most widely used casting alloy and its inoculation phenomenon was discovered in 1920 [1] and patented by Meeh in 1924 [2]. There are many studies on this phenomenon, which are summarized and analyzed in [3]. Elements such as Ba, Ca and Sr, which are usually introduced to a bath in ferrosilicon, are the most important inoculants of cast iron. Ferrosilicon that contains these elements is treated as a complex inoculant. The purpose of this study were to analyze the inoculation effects and explain the inoculation mechanism of cast iron
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