In general, simple thermal analysis is most often used in industry to monitor the solidification of metallic materials. Based on the obtained cooling curves, the course of solidification can be determined based on the characteristic temperatures. Due to uneven temperatures throughout the casting, different proportions and sizes of microstructural components can be obtained during metallographic analysis.
The purpose of this thesis was to measure the specific electrical resistivity and dimensional changes of the casting in addition to the temperature measurement. The purpose is to compare the obtained measurements with the characteristic temperatures obtained by thermal analysis and to define the type of graphite that is formed in the microstructure. The diploma thesis covers the description and interpretation of metallographic analysis, thermal analysis, dilatometric analysis and measurements of specific electrical resistivity.
Measurements were performed on material of EN-GJS-400-18-LT. In the experiment, we had several samples that were inoculated and nodularized. The aim was to prepare as similar chemical composition as possible for all samples, as this allowed us to compare the obtained results. The obtained samples were used to determine the type of cast iron and define the shape of the graphite.
Thus, we defined the change in electrical resistivity during the transition from liquid to solid state and showed that the specific electrical resistivity is higher if the graphite is in the form of lamellae instead of spheres. At the same time, we found that an inert atmosphere was not suitable for melting cast iron, as we had problems ensuring the similarity of the chemical composition of the samples.
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