Vplivi grafita na električne lastnosti sivih litin z lamelnim grafitom

Žolnir, Janez (author), Petrič, Mitja (mentor), Vončina, Maja (co-mentor)

Meritve električne prevodnosti kovin so pomemben del analiznih metod pri razvoju in testiranju materialov. Uporabljajo se za spremljanje reakcij, ki potekajo v materialih pri spremembi temperature, kot so premene v trdnem, izločanje faz ter potek strjevanja kovin in zlitin. Velik vpliv na električno upornost imajo mikrostrukturne sestavine, še posebej velikost in oblika delcev. Namen diplomskega dela je bil ugotoviti, kakšen vpliv ima oblika grafita na električno upornost sive litine. Izdelali smo sivo litino z lamelnim grafitom, ki smo jo po taljenju in cepljenju v različnih časovnih intervalih ulivali v merilno celico za merjenje električno upornost. Znano je, da učinek cepiva s časom pada, kar pa povzroči spremembo oblike grafita in njegovo porazdelitev, ki vpliva na električno prevodnost litin. Uporabljene metode za ovrednotenje rezultatov so bile poleg meritev električne upornosti še termična analiza, kemijska analiza, simultana termična analiza, meritve trdote in optična mikroskopija. Meritve električne upornosti so pokazale, da manj kot je grafita in finejša kot je mikrostruktura, nižja je električna upornost, kar smo tudi predpostavljali.

• Language: Slovenian
• Keywords: siva litina, mikrostruktura, oblika grafita, električna upornost, cepivo, titan
• Work type: High school thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2019
• PID: 20.500.12556/RUL-112889
• COBISS.SI-ID: 1846879
• Publication date in RUL: 19.11.2019

Secondary language

• Language: English
• Title: The effects of graphite on the electrical properties of gray cast iron with lamellar graphite

Abstract

The electrical resistivity measurements are important piece at analysing and testing of materials. They are used for monitoring reactions in materials during temperature variations, which are phases transformation in solid and solidification of materials and alloys. Most important influence on electrical conductivity are microstructure and size of phases in materials. In my diploma work I want to discover what influence have graphite lamellas on gray cast iron. We had made three different alloys of gray cast iron, which we poured in different timings in cells for measuring electrical resistivity. The inoculations in melt of gray cast iron is losing the effect over the time, whilst we detect the changes. For analysis we use electrical resistivity measurements, thermal analysis, chemical analysis, simultaneous thermal analysis, hardness test and optical metallographic analysis. We found that the smaller the microstructure and lowest is concentration of graphite the lower is electrical conductivity.

• Keywords: gray cast iron, microstructure, shape of graphite, electrical resistivity, modification, titanium