The master's thesis analysed and categorized non-metallic inclusions in two lead alloys
Pb-Ca-Sn, which are used for production of lead-acid starter batteries. These batteries
are characterized by long lifespan, low maintenance requirements, and the ability to
maintain power in a ready to use state. Non-metallic inclusions that occur in lead alloys
are undesirable and have a negative impact on the casting process, as well as on
mechanical and electrochemical properties of the alloys. Non-metallic inclusions
mostly occur due to contact between the melt and the atmosphere.
Chemical analysis of the alloys was performed using spark-induced optical emission
spectrometry. Samples were examined using light and electron microscopy, which
allows analysis of chemical composition. The solidification and melting processes of
the two alloys were studied using differential scanning calorimetry. Thermodynamic
calculations of equilibrium and non-equilibrium solidification were defined based on the
chemical composition of the alloys, which help explain the formation of inclusions.
The results show that Pb-Ca-Sn alloys mostly contain oxide inclusions. Non-metallic
inclusions with the chemical composition of PbO2, Pb2O3, Al2O3, and CaO were
identified. Most inclusions are located near the surface of the sample, which had the
most contact with the atmosphere. The proportion of non-metallic inclusions can be
reduced by using a protective atmosphere during melting.
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