Introduction
The application of inoculants in ductile iron casting is necessary to obtain the mechanical properties specified in the ASTM specification. In order to get the best cast results, it is important to use the right inoculants and to use them in the right amount. This paper will discuss the different types of inoculants used in ductile iron casting and the factors that need to be taken into account when choosing the right inoculant. It will also give an overview of the different types of inoculants and their associated parameters.
Types of Inoculants
The main types of inoculants used in ductile iron casting are magnesium, calcium, strontium, barium, and zirconium. Magnesium is used to reduce carbide formation, promote graphite formation, and increase strength. Strontium and barium are used to reduce hot tearing and size porosity, along with being agents for nodule and globular graphite formation. Zirconium is used to promote graphite nodularity, reduce graphite exfoliation, increase impact strength, and to refine the matrix microstructure.
Calcium is the most widely used inoculant in the ferrous casting industry and is used to reduce the size of graphite flakes and to regulate graphite nodule structure. Magnesium is the second most used inoculant and is typically used in combination with calcium to promote nodularity and high strength. Strontium and barium are used to reduce size porosity and hot tearing and to increase the impact strength of the castings. Zirconium is used to refine the matrix and to promote nodular graphite.
Parameters to Consider
When selecting an inoculant for a casting application, there are several important parameters to consider: type of inoculant, dosage rate, melt treatment, and alloy composition. The type of inoculant used depends on the desired properties of the casting and the melting process used. The dosage rate depends on the properties of the melt, such as the carbon equivalent, nodule count, and ferrite content. The melt treatment should be chosen depending on the inoculant used and the desired properties of the castings. Finally, the alloy composition should be selected based on the type of inoculant and the desired mechanical properties.
Conclusion
In conclusion, the selection of the right inoculant for ductile iron casting is a complex process that involves several parameters. It is important to select the right type of inoculant, dosage rate, melt treatment, and alloy composition in order to obtain the desired properties in the castings. With the right selection of inoculants and the proper use, high-quality castings can be obtained.
