Ispitivanje svojstava reciklirane DE-OX aluminijske legure za dezoksidaciju čelika

master's thesis

• Title (english): Testing the properties of recycled DE-OX aluminium alloy for steel deoxidation
• Author: Marija Papeš
• Mentor: Zdenka Zovko Brodarac (mentor)
• Mentor: Franjo Kozina (pomoć pri izradi, neposredni voditelj)
• Mentor: Siniša Lazić (pomoć pri izradi, neposredni voditelj)
• Committee member: Anita Begić Hadžipašić (predsjednik povjerenstva)
• Committee member: Zdenka Zovko Brodarac (član povjerenstva)
• Committee member: Natalija Dolić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2024-09-10, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Interdisciplinary Technical Sciences

Abstract

U ovim diplomskom radu ispitan je reciklirajući potencijal aluminija na primjeru tvrtke CIAL d.o.o. kao jedine ljevaonice aluminija na području Republike Hrvatske ovlaštene za oporabu i pretaljivanje metalne aluminijske ambalaže – limenki. Istraživanje je provedeno u svrhu određivanja otpornosti na degradaciju uzorka DE-OX legure koja se u obliku ingota koristi za dezoksidaciju čelika. Uvjeti ubrzane degradacije simulirani su uranjanjem uzoraka u EXCO otopinu u vremenskim intervalima od 5, 24, 48, 72 i 96 sati. Stabilnost legure procijenjena je karakterizacijom kemijskog sastava, mikrostrukture i mikrotvrdoće uzoraka prije i nakon uranjanja. Kemijski sastav uzorka nalazi se unutar granica propisanih deklaracijom proizvođača. Kombinacijom rezultata proračuna ravnotežnog i neravnotežnog slijeda skrućivanja s rezultatima metalografske analize određen je slijed skrućivanja te identificirane intermetalne faze prisutne u metalnoj osnovi primarnog αAl. Rezultati procjene stabilnosti DE-OX legure ukazuju na porast pH vrijednosti otopine te nastanak i porast pukotina s vremenom zadržavanja uz minimalni gubitak mase. Porast vrijednosti pH otopine posljedica je kemijskih reakcija i izmjene iona između ispitivane površine uzorka i EXCO otopine, dok su nastanak pukotina i njihovo interdendritno napredovanje posljedica razlike u potencijalu između metalne osnove i intermetalnih faza. Minimalni gubitak mase ukazuje na nastanak i zadržavanje sloja korozijskih produkata. Približno slične vrijednosti mikrotvrdoće izmjerene uz ispitivanu površinu uzoraka nakon izlaganja ukazuju na stabilnost i zaštitnu ulogu sloja korozijskih produkata.

Abstract (english)

In this work, the recycling potential of aluminum was examined using the example of the company CIAL d.o.o., which is the only aluminum foundry in the Republic of Croatia authorized to recover and remelt metallic aluminum packaging - cans. The study was performed to determine the degradation resistance of a DE-OX alloy used in the form of ingots for steel deoxidation. Accelerated degradation conditions were simulated by immersing the samples in EXCO solution at time intervals of 5, 24, 48, 72 and 96 hours. The stability of the alloy was evaluated by characterizing the chemical composition, microstructure and microhardness of the samples before and after immersion. The chemical composition of the sample is within the limits specified in the manufacturer's declaration. By combining the results of the thermodynamic equilibrium and non-equilibrium calculations with the results of the metallographic analysis, the solidification sequence and the intermetallic phase present in the primary αAl matrix were determined. The results of degradation testing show an increase in the pH value of the EXCO solution as well as the nucleation and propagation of cracks with increasing exposure time. At the same time, a minimal loss of mass was observed during the experiment. The increase in the pH of the solution is the result of chemical reactions and ion exchange between the tested surface of the sample and the EXCO solution, while the formation of cracks and their interdendritic propagation is due to the difference in electrochemical potential between the matrix and the intermetallic phases. Minimal mass loss indicates the formation and retention of a layer of corrosion products. The approximately equal values of microhardness measured along the tested surface of the samples after exposure indicate the stability and protective role of the layer.

• Keywords: sekundarna aluminijska legura; kemijski sastav; mikrostruktura; elektrokemijska korozija; degradacija
• Keywords (english): secondary aluminum alloy; chemical composition; microstructure; electrochemical corrosion; degradation
• Language: croatian
• URN:NBN: urn:nbn:hr:115:135823
• Study programme: Title: University graduate study program in Occupational Safety, Health and Environment; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/ka sigurnosti, zdravlja na radu i radnog okoliša (magistar/magistra inženjer/ka sigurnosti, zdravlja na radu i radnog okoliša)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-08-27 07:00:59