Dilatometrijska analiza in električna upornost sivih litin med strjevanjem : diplomsko delo

Kocijančič, Staš (avtor), Petrič, Mitja (mentor)

V splošnem se v industriji za spremljanje strjevanje kovinskih materialov najpogosteje uporablja enostavno termično analizo. Na podlagi dobljenih ohlajevalnih krivulj lahko iz karakterističnih temperatur določimo potek strjevanja. Zaradi neenakomernih temperatur po celotnem ulitku lahko pri metalografski analizi dobimo drugačne deleže in velikosti mikrostrukturnih sestavin. Namen te diplomske naloge je poleg meritve temperature merili tudi specifično električno upornost in dimenzijske spremembe ulitka. Namen je primerjati dobljene meritve s karakterističnimi temperaturami pridobljenimi s termično analizo ter opredeliti tip grafita, ki nastaja v mikrostrukturi. Diplomsko delo zajema opis in razlago metalografske analize, termične analize, dilatometrijske analize in meritve specifične električne upornosti. Meritve so se izvajale na materialu kakovosti EN-GJS-400-18-LT. V eksperimentu smo imeli več vzorcev, ki so bili cepljeni in nodulirani. Namen je bil pripraviti za vse vzorce čim bolj podobno kemijsko sestavo, saj smo tako lahko primerjali dobljene rezultate. Dobljenim vzorcem smo določili vrsto litine in opredelili obliko grafita. Tako smo definirali spreminjanje električne upornosti na prehodu iz tekočega v trdno stanje in pokazali, da je specifična električna upornost večja, če je grafit v obliki lamel namesto kroglic. Hkrati smo ugotovili, da za taljenje litine ni bila primerna inertna atmosfera, saj smo imeli težave z zagotavljanjem podobnosti kemijske sestave vzorcev.

• Jezik: Slovenski jezik
• Ključne besede: Ključne besede: metalografska analiza, termična analiza, karakteristične temperature, dilatometrijska analiza, specifična električna upornost.
• Vrsta gradiva: Diplomsko delo/naloga
• Tipologija: 2.11 - Diplomsko delo
• Organizacija: NTF - Naravoslovnotehniška fakulteta
• Kraj izida: Ljubljana
• Založnik: S. Kocijančič
• Leto izida: 2023
• Št. strani: XI, 48 f.
• PID: 20.500.12556/RUL-151101
• UDK: 669
• COBISS.SI-ID: 168574467
• Datum objave v RUL: 29.09.2023

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Dilatometric analysis and electrical resistivity of cast irons during solidification : diploma work

Izvleček

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.

• Ključne besede: Key words: metallographic analysis, thermal analysis, characteristic temperatures, dilatometric analysis, specific electrical resistance.