Repository of Faculty of Metallurgy University of Zagreb
Not a member yet
491 research outputs found
Sort by
60. godina studijskih programa Metalurškog fakulteta Sveučilišta u Zagrebu – II. dio
No full textMetalurški fakultet Sveučilišta u Zagrebu je jedina znanstveno-nastavna ustanova u Republici Hrvatskoj koja, poštujući kulturu kvalitete, na preddiplomskoj, diplomskoj, poslijediplomskoj i stručnoj razini pruža visokoškolsko obrazovanje iz područja metalurgije i materijala, industrijske ekologije i sigurnosti, zdravlja na radu i radnog okoliša, a organizacijom savjetovanja, seminara, radionica, javnih tribina i predavanja sustavno provodi program cjeloživotnog obrazovanja i usavršavanja te pruža potporu gospodarskim subjektima metalurške, metaloprerađivačke, brodograđevne i ljevačke industrije. U ovom je dijelu naglašen pojam i važnost metala u svakodnevnoj primjeni te opisana specifičnost moderne metalurgije. Proizvodne djelatnosti i obrazovanje čine temelj razvoja svake države, te je i strategiju razvoja nužno osloniti upravo na izvrsne mlade ljude koji stjecanjem znanja te istraživačkim pristupom obogaćuju Republiku Hrvatsku rijetkim znanjima, vještinama i kompetencijama. Sve se to ogleda u strateškim pravcima Metalurško inženjerstvo, Metalni materijali te Sigurnost, zdravlje na radu i radni okoliš. Izvrsnost se temelji na ulaganju u visokosofisticiranu opremu kao potencijal postizanja novih i/ili inovativnih znanja, kreativnosti te prepoznatljivosti na europskoj istraživačkoj karti. Prikazan je razvoj studijskih programa te smjernice za razvoj Metalurškog fakulteta u 21. stoljeću. Istaknuta je važnost implementacije infrastrukturnih projekata poput Centra za ljevarstvo-SIMET i VIRTULAB-Integrirani laboratorij za primarne i sekundarne sirovine.Ulaganje u opremu nije samo sebi cilj. Uspostavljeni znanstvenoistraživački potencijal čini temelj za ulaganje u znanje, vještine i kompetencije djelatnika i studenata, ali i otvara mogućnost ciljanih djelatnosti kroz spin off budući da je u društvenom poretku koji danas živimo nužno doseći samodostatnost. U razvoju polja nužno je koncentrirati se na trojstvo konkurentnosti metalske industrije – suvremenu tehnologiju, učinkovit proizvodni postupak i visokokvalificiranu radnu snagu. Za razvoj znanstvene, nastavne i stručne djelatnosti Metalurškog fakulteta, ali i razvoj metalske industrije u Republici Hrvatskoj ključnu ulogu ima reprezentativan trokut utjecajnih čimbenika (Triple Helix): poslovni sektor, znanstvenoistraživački kapaciteti i javna politika
Toxicity of non-precious metal jewellery
No full textUgljični čelik je materijal koji zbog svojih svojstava i cijene ima mnogo različitih namjena.
Nedostatak ovog materijala je taj što nema otpornost prema koroziji. Vrlo često se zbog toga
na ugljični čelik nanose različite prevlake.
U ovom radu praćena je migracija iona kroma, nikla i bakra iz prevlaka na ugljičnom čeliku
koji je korišten za izradu nakita. Nakit od čelika je stavljan u kontakt s modelnom otopinom
znoja da bi se simulirali uvjeti koji nastaju prilikom nošenja nakita uslijed interakcije kože
(znoja) i nakita. Dobiveni rezultati su pokazali da postoji značajna migracija navedenih iona u
otopinu znoja. Koncentracija migriranih iona ovisi o vremenu kontakta nakita i otopine, ali i o
debljini prevlake i eventualnim oštećenjima na nakitu. Za usporedbu rezultata provedena su
identična istraživanja na nakitu koji je napravljen od nehrđajućeg čelika.Carbon steel is a material that is widely used for various purposes due to its properties and price.
However, it is not resistant to corrosion, which is one of the major drawbacks. Therefore,
different coatings are often applied to carbon steel. In this graduate thesis, the migration of
chromium, nickel and copper ions from coatings on carbon steel used for jewellery making was
monitored. Steel jewellery was placed in contact with a model solution of sweat to simulate the
conditions that occur during the interaction of jewellery and skin perspiration. The obtained
results showed that there is a significant migration of these ions into the perspiration solution.
The concentration of migrated ions depends on the contact time of the jewellery and the
solution, but also on the thickness of the coating and possible damage on the jewellery. To
compare the results, identical studies were performed on jewellery made of stainless steel
Determination of Al-2.18Mg-1.92Li Alloy’s Microstructure Degradation in Corrosive Environment
No full textThe utilization of aluminum-lithium-magnesium (Al-Li-Mg) alloys in the transportation
industry is enabled by excellent engineering properties. The mechanical properties and corrosion
resistance are influenced by the microstructure development comprehending the solidification of
coherent strengthening precipitates, precipitation of course and angular equilibrium phases as
well as the formation and widening of the Precipitate-free zone. The research was performed to
determine the microstructure degradation of Al-2.18Mg-1.92Li alloy in a corrosive environment using
electrochemical measurements. The solidification sequence of the Al-2.18Mg-1.92Li alloy, obtained
using Thermo–Calc software support, indicated the transformation of the Al dendritic network and
precipitation of AlLi (), Al2LiMg (T), and Al8Mg5 () phase. All of the phases are anodic with respect
to the Al enabling microstructure degradation. To achieve higher microstructure stability, the sample
was solution hardened at 520 C. However, the sample in as-cast condition showed a lower corrosion
potential (749.84 mV) and corrosion rate (17.01 mm/year) with respect to the solution-hardened
sample (752.52 mV, 51.24 mm/year). Higher microstructure degradation of the solution-hardened
sample is a consequence of phase precipitation at the grain boundaries and inside the grain of Al,
leading to intergranular corrosion and cavity formation. The phase precipitates from the Li and Mg
enriched the Al solid solution at the solution-hardening temperature
Šumarstvo, izazovi u području sigurnosti na radu
No full textU završnom radu opisane su, kroz tehnologiju rada, opasnosti u šumarstvu i njezine štetnosti i napori koje prijete radnicima u djelatnostima koje su tim rizicima najviše izloženi, a to su djelatnosti šumskog radnika, šumskog radnika sjekača, šumskog radnika na poslovima uzgajanja šuma, vozača kamiona i traktorista-kopčaša. Kroz tehnologiju rada, radne postupke u sječi i izradi drvnih sortimenata, najlakše se upoznati sa prijetnjama sigurnosti na radu u šumarstvu. Važnu ulogu u sigurnom radu, pa tako i u ovom slučaju, ima procjena rizika u šumarstvu. Kroz procjenu rizika, uz opasnosti, štetnosti i napore, ukazano je na mjere zaštite na radu u šumarstvu i načine smanjenja rizika za radnika.This paper describes trought the work technology dangers in forestry, its harms and strains that are potential threat to the workers who are the most exposed to the risks in this industry. Most of activities in this profession are dangerous, especially activities of the forest worker, logger, worker in forest cultivation, lorry and tractor driver. Working technology and working procedures in felling and making wood assortments are the best introduction to the health and safety risks in forestry. Risk assessment in forestry plays main role in safe organised work following protection measures and pointing out how to reduce risks for the manpower
The influence of vibrations on humans and measures to protect workers from risks due to exposure to vibrations at work
No full textU ovome radu definirane su vibracije te je dana njihova podjela. Pobliže je objašnjen njihov utjecaj na čovjeka i radnika te je obrađena zakonska regulativa čijim se pridržavanjem štetan utjecaj vibracija smanjuje na najmanju moguću mjeru. Osim navedenog, definirano je i samo mjerenje vibracija te mjere zaštite od vibracija koje bi bilo poželjno implementirati u radni proces.In this paper, vibrations are defined and their division is given. Vibrations influence on humans and workers is explained in detail, and the legal regulations, whose compliance reduces the harmful impact of vibrations to the smallest possible extent, are discussed. In addition, vibration measurement and vibration protection measures that would be desirable to implement in the work process are defined
Influence of remelting on mechanical properties of AlSi9Cu3(Fe) alloy
No full textConventional AlSi9Cu3(Fe) (EN AC 46000) alloy is the most common Al-alloy used in the automotive industry. Also, the high-pressure die-casting (HPDC) represents the most common process for this type of complex geometry and high performance castings due to economy and shortening of process cycle. The AlSi9Cu3(Fe) alloy enables achievement of relatively high mechanical properties, strength and hardness, excellent fluidity and resistance to hot cracking, although it shows slightly lower elongation and corrosion resistance. Usage of secondary charge material influences is cost-effective due to saving of raw materials and energy and reduction of pollution. The mechanical properties of aluminium cast alloys are strongly dependent from the microstructure which develops on the base of chemical composition, melt treatment, solidification rate, casting process and from potential heat treatment. This paper investigates the influence of remelted AlSi9Cu3(Fe) alloy on the mechanical properties in as-cast state, and after 4 and 80 weeks of natural aging. The metallographic analysis showed that the microstructure of such alloy does not deviate significantly from usual practice obtained by using 50 % or 100 % of returnable material. Mechanical properties investigation indicates degradation of the yield strength in as-cast state and after 4 weeks of natural aging, despite the same microstructure constituents. After 80 weeks, the effect of natural ageing led to the increase in yield strength and achievement of satisfactory mechanical properties
Influence of microstructure on the resistance of tool steels to local corrosion in 3.5% NaCl medium
No full textIn this research, electrochemical and metallographic tests were carried out on tool steel for cold and hot work, as well
as steel for cementation, with the goal to obtain corrosion parameters to determine which of the examined samples is
more resistant to local pitting corrosion. Electrochemical tests were performed in a medium of 3.5% NaCl, and were
based on conducting cyclic anodic polarization in the potential range from -2000 mV to 200 mV vs SCE and vice versa.
The results of the research showed that all three samples are subject to pitting corrosion, but the worst was the cementing tool steel sample X19NiCrMo4, which had the lowest pitting potential. The W600 tool steel sample for hot work
proved to be the best, with the highest pitting potential.
The results of the electrochemical tests coincide with the metallographic tests, because after corrosion in the chloride
medium only the beginnings of pitting corrosion are visible on the surface of the W600 sample in the form of partial
accumulations of corrosion products, while the X19NiCrMo4 cementing steel sample was completely covered with
corrosion products, which means that of the three tested tool steels, cementing steel is the most susceptible to pitting
corrosion and is not recommended for use in conditions where it comes into contact with chloride ions. The martensitic
microstructure of cementing tool steel is responsible for the very low pitting potential and, consequently, pronounced
pitting corrosion. On the other hand, the W600 tool steel showed better corrosion resistance due to its finer grain and
uniform carbide distribution
Experiences in asbestos-containing waste management in the Republic of Croatia
No full textThis paper presents an overview of asbestos production data worldwide and in the Republic of Croatia in the period 2000 to 2018 as well as the asbestos consumption data from 1995 to 2010. The results of asbestos waste collection from 1995 to 2018 have been analyzed and the experiences of the Republic of Croatia in the management of asbestos- containing waste have been described in accordance with the applicable national legislation. Although asbestos does not pose a risk as long as its products do not become damaged by fracture, or during transportation or decomposition, it poses a potential danger to human health. In today's world, every five minutes someone dies from a disease related to asbestos, such as asbestosis and cancer caused by asbestos. For these reasons, most countries adopted the obligation to execute a series of measures to stop using asbestos in 1999, while at the same time in the Republic of Croatia still imported about 4000 tonnes of asbestos per year. In 2006, the Republic of Croatia banned the production, transport, and use of asbestos, and the asbestos objects whose lifetime expired ended up in municipal waste, causing the need for special regulations in order to arrange the management of asbestos containing waste. Over the past ten years, the Republic of Croatia has developed an asbestos waste management system. Regardless of the success of its application, certain improvements are needed, as data on the amounts of reported construction waste, and thus the part containing asbestos, do not coincide with economic and other indicators for the construction sector
Adsorption of Zn(II) Ions on Metallurgical Waste
No full textMetalurški otpad ima velik potencijal za uporabu kao adsorbens za uklanjanje teških metala iz otpadnih voda, ističući se kao mogući jeftini adsorbens. U ovom članku prikazano je adsorpcijsko ponašanje Zn(II) iona na dva kruta metalna otpadna materijala – otpadnoj kalupnoj mješavini (OKM) i otpadnoj anodnoj prašini (AP). Dobiveni rezultati pokazali su da se oba otpadna materijala mogu upotrebljavati kao potencijalni adsorbensi. Anodna prašina ima bolja adsorpcijska svojstva. Ravnotežni podatci za adsorpciju Zn(II) na otpadnim metalurškim materijalima ispitani su Freundlichovim i Langmuirovim izotermnim modelima. Utvrđeno je da je Langmuirov model prikladniji te da se adsorpcija odvija kao kemisorpcija.Metallurgical waste has great potential for use as an adsorbent for the removal of heavy metals from wastewater, standing out as possible low-cost adsorbents. This article presents the adsorption behaviour of Zn(II) ions on two solid metal waste materials – waste mould sand (WMS) and anode dust (AD). The obtained results showed that both waste materials could be used as potential adsorbents. Anode dust has better adsorption properties. The equilibrium data for the adsorption of Zn(II) on waste metallurgical materials were examined by Langmuir and Freundlich’s adsorption isotherm models. It was found that the Langmuir model is more appropriate, and that adsorption takes place as chemisorption
Roughness of the Surface of Zirconia Reinforced Lithium Disilicate Ceramic Treated by Different Procedures
No full textLithium disilicate and zirconia are the two most popular materials for aesthetic and dental prosthetic work; however, due to their limitations, a new material is being researched, namely zirconia-reinforced lithium disilicate, the surface of which is treated with different procedures to achieve the best possible surface properties. In this study, the surface of zirconia-reinforced lithium disilicate glass-ceramic was treated using different methods (conventional and laser) to determine the effects of the treatment procedures on the surface properties and surface roughness to achieve a higher strength of adhesion from the self-adhesive resin cement to zirconia-reinforced lithium disilicate. The treated surfaces were investigated using profilometry, X-ray diffraction and energy dispersive X-ray fluorescence. The results obtained were statistically evaluated. The results show that the surface roughness is highest for the samples treated with Er:YAG (erbium-doped yttrium aluminium garnet laser) and silanisation. Furthermore, the surface treatment procedures applied did not change the composition of the surface