magistrsko delo
Matic Mahkovic (Author), Mitja Petrič (Mentor), Primož Mrvar (Co-mentor)

Abstract

S cepljenjem sivih litin s kroglastim grafitom lahko vplivamo na velikost in razporeditev grafitnih krogel in posledično prilagajamo mehanske lastnosti potrebam uporabe. Cepljenje poteka z dodajanjem cepiv v talino. Eden od elementov v cepivih, ki poveča število grafitnih krogel ter zmanjša njihovo velikost, je Ba. Vloga Ba pri nukleaciji sivih litin s kroglastim grafitom ostaja neznana, obstaja pa več teorij, ki jo poskušajo razložiti. Z namenom ugotovitve vloge Ba v nukleaciji je bil izveden eksperiment. V eksperimentu se je ulilo 7 vzorcev s cepivom, ki vsebuje Ba, imenovano Barinoc in eden vzorec brez cepiva. Cepivo se je v vzorce vneslo po dveh postopkih. Pri prvemu so se večja zrna pritrdila s kanthalovo žico na merilno celico. Namen je bil spremljati kako se Ba raztaplja med ulivanjem in strjevanjem. Pri drugem pa so bila zrna zdrobljena v finejšo granulacijo in vstavljena v papirnate lončke. Na takšen način se je simuliral postopek cepljenja v curek. Vnesle so se štiri različne količine Barinoca, določene glede na predpisano količino. Rezultati naj bi podali kako različna količina, oblika in postopek vplivajo na nukleacijo grafitnih krogel. Med litjem se je merila temperatura posameznega vzorca. Preko zbranih temperatur se je opravila termična analiza in izrisalo ohlajevalne krivulje, preko katerih se je ocenilo uspešnost cepljenja. Izvedla se je kemijska analiza na vzorcu brez cepiva, s katero se je preverila ustreznost sestave naše litine. Na posameznih vzorcih pa se je izvedla kemijska analiza z namenom določitve predvsem deleža Ba v posameznem vzorcu. Z optičnim in elektronskim mikroskopom se je izvedla metalografska analiza mikrostrukture vzorcev s poudarkom na analizi faz v sredini grafitnih krogel, ki predstavljajo kali in površine enega od vzorcev. Prav tako se je določevala kemijska sestava kali in površine enega od vzorcev.

Keywords

siva litina s kroglastim grafitom;heterogena nukleacija;cepljenje;cepiva;barij;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL NTF - Faculty of Natural Sciences and Engineering
Publisher: [M. Mahkovic]
UDC: 669
COBISS: 90371587 Link will open in a new window
Views: 244
Downloads: 39
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Other data

Secondary language: English
Secondary title: ǂthe ǂrole of barium in the graphite nucleation mechanism at spheroidal graphite cast iron
Secondary abstract: 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.
Secondary keywords: ductile iron;heterogeneous nucleation;inoculation;inoculants;barium;
Type (COBISS): Master's thesis/paper
Study programme: 0
Thesis comment: Univ. v Ljubljani, Naravoslovnotehniška fak., Oddelek za materiale in metalurgijo
Pages: XIV, 50 f.
ID: 14040750