Abstract
The segregation behavior of elements in spherical graphite cast iron is an important part of understanding the material in terms of its mechanical and physical properties. In this research, a detailed study has been carried out with the investigation of the segregation of elements in spherical graphite cast iron. Tests have been performed on specimens formed with the addition of primary and secondary melts with different mass percentages of alloying elements. It has been found that the segregation behavior of elements depends on the cooling rate and the nature of the elements. For elements such as carbon and silicon, higher segregation has been observed in specimens with lower cooling rates. For elements such as magnesium and manganese, higher segregation has been observed in specimens with higher cooling rates. The results from this study could be beneficial for forging and casting operations and for understanding the properties of spheroidal graphite cast iron.
1. Introduction
Cast iron is an alloy of iron and carbon. It is one of the most widely used materials for a variety of engineering applications due to its excellent mechanical properties and ease of manufacturing process. One of the most common types of cast iron is spherical graphite cast iron (SGCI). This type of cast iron has a spherical graphite shape which provides excellent mechanical and casting properties. However, the presence of certain alloying elements can have an important effect on the mechanical and physical properties of this material.
In this study, a detailed investigation of the segregation behavior of elements in spherical graphite cast iron has been carried out with the use of primary and secondary melts. With the use of filtered primary and secondary melts, a specimen’s mass percentage of alloying elements can be varied. Tests have been carried out on specimens with different mass percentages of alloying elements and the segregation behavior of elements has been studied. The findings of this study could provide further insight into the properties of spherical graphite cast iron and could be beneficial for forging and casting operations.
2. Experimental Work
2.1 Raw Materials
The primary and secondary melts used for the cast iron specimens were prepared using the following raw materials (wt%): iron ore (93); coal (3.5); calcium oxide (2); graphite powder (0.5); and flux (1). The ferrous and graphite elements were melted together in a crucible and cooled to 1150℃. The molten mixture was stirred several times to ensure homogeneous mixing. The primary melt was then filtered to remove any impurities. The secondary melts for the cast iron specimens were prepared by adding 0.5 - 2 wt% of different elements to the primary melt.
2.2 Casting Specimens
In order to investigate the segregation behavior of elements in spherical graphite cast iron, specimens with varying mass percentages of alloying elements were cast. The primary and secondary melts were poured into pre-heated graphite molds under normal gravity. The molds were then cooled from 1150℃ to room temperature at different cooling rates, ranging from slow to fast. The specimens were then machined to a standard dimension for analysis.
3. Results and Discussion
The segregation behavior of the alloying elements in spherical graphite cast iron was studied with the use of primary and secondary melts. Element segregation is dependent on the cooling rate of the specimens and the nature of the element.
For carbon, segregation is higher in specimens with lower cooling rates. This is due to the fact that carbon is immiscible with iron and tends to remain in its molten form at higher temperatures. As the temperature decreases, carbon is more likely to solidify and become concentrated in one area. For silicon, segregation decreases as the cooling rate increases. This is because silicon is more soluble in iron at higher temperatures, thus leading to increased segregation at lower cooling rates.
For elements such as magnesium and manganese, segregation increases as the cooling rate increases. This is due to the fact that these elements are more soluble in iron at lower temperatures, thus leading to increased segregation at higher cooling rates.
4. Conclusion
In this research, the segregation behavior of elements in spherical graphite cast iron was studied with the use of primary and secondary melts. The findings of this study indicate that the segregation behavior of elements depends on the cooling rate and the nature of the elements. For elements such as carbon and silicon, higher segregation has been observed in specimens with lower cooling rates. For elements such as magnesium and manganese, higher segregation has been observed in specimens with higher cooling rates. The results from this study could be beneficial for forging and casting operations and for understanding the properties of spheroidal graphite cast iron.
