With the inoculation of ductile iron, we can effect on the size and distribution of the
graphite nodules and consequently adapt the mechanical properties to the needs of
usage. The inoculation is carried out by adding inoculants into the melt. One of the
elements in inoculants that increases graphite nodule count and reduces their size is
barium. The role of barium in the inoculation of ductile iron remains unknown but there
are multiple theories that are trying to explain it.
To determine the role of Ba in nucleation, an experiment was carried out in which 7
samples containing an inoculant called Barinoc and one without inoculant were casted.
The inoculant was inserted by two methods. By the first method, larger grains of
inoculant were attached on the measurement cell with a kanthal wire. The purpose
was to monitor how Ba dissolves during casting and solidification. In the other method,
the grains were crushed into smaller granulation and inserted in the paper cups. The
late stream inoculation was simulated that way. Four different amounts of Barinoc were
used, based on the prescribed amount. The results should tell us how different amount,
shape and method affects the nucleation of graphite nodules.
During casting, the temperature of each sample was measured. Through collected
temperatures thermo analysis and cooling curves were made. Through them the
success of inoculation was evaluated.
A chemical analysis was performed on the inoculant-free sample to verify the
adequacy of the chemical composition of our alloy. Chemical analysis was performed
on individual samples to determine the percent of barium in each sample.
Using an optical and scanning electron microscope, a metallographic analysis of the
microstructure of each sample was made with emphasis on analysing the cores of
graphite nodules and surface of one of samples. The chemical composition of nucleus
and surface was also made.
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