Repository of Faculty of Metallurgy University of Zagreb
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The dark side of artificial light
No full textIn the recent past, Earth inhabitants had a completely dark night and sky full of stars at night, while in the last twenty years, only the inhabitants of less-developed countries could enjoy the starry sky, who had no possibility to install sources that would threaten the night sky by overuse of artificial lighting. Specifically, today we are faced with light pollution, which is primarily the result of the scattered light of cities and other light emissions from artificial sources, mainly from urban areas and areas where economic operators (factories, warehouses, etc.) are concentrated. Much of the light flux from these sources, and therefore energy, is scattered and lost in the sky, which makes the night sky brighter and the celestial objects in its background become invisible. Light pollution is now considered a complex problem that has a detrimental effect on the environment with a very wide range of consequences. The harmful effects on the environment are primarily reflected in disturbances in astronomical observations, inducing hormonal disorders in humans working at night, in plants disturbing vegetation cycles in plants, disorienting birds in space, sea turtle cubs and some other animal species, which all together directly affects at their survival, often causing changes in the habitat of endangered animal species. This has led to the development of scotobiology, which as a branch of biology deals with the benefits of darkness and helps to establish a safe level of brightness, duration and color of night illumination to avoid the harmful effects of light pollution on the living world. Given that there is a need to protect the environment as a whole, and human health as well, from light pollution, it is necessary to take appropriate measures to educate the public about the potential adverse effects of light pollution while at the same time improving legislation in this area of environmental protection, because only through valid legal framework for the adoption of regulations on protection against light pollution, it is possible to reduce, if not completely eliminate, the harmful effects of light pollution in the environment
The influence of hot deformation on the quality of welding of niobium microalloyed seam pipes intended for plumbing installations
No full textResearch was carried out on seamed and hot-rolled seamed pipes intended for water installations. The tubes are rolled from hot-rolled strip microalloyed with 0,046% Nb. All pipes met the required properties. The quality of the welds, base material and heat-affected zone, was examined in detail. It was found that the quality of the welds in hot-rolled seamed pipes is significantly better. Special attention is paid to the removal of internal excess welds of hot-rolled seamed pipes. Improper internal weld excess can lead to the clogging of pipes during their use in production process
Waste disposal and processing in the city of Sisak
No full textRadi očuvanja okoliša i zdravlja ljudi te s obzirom na europsku i hrvatsku legislativu, sakupljen otpad potrebno je svesti na minimum. Prvi korak je prikupljanje otpada, odnosno sirovine te obrada u smislu sortiranja prema vrsti, frakcijama i svojstvima. Slijedeći korak je priprema za ponovnu uporabu, poput baliranja ili usitnjavanja te prijevoz do ovlaštenog oporabitelja. Cilj sustava gospodarenja otpadom jest smanjiti količinu otpada koja se odlaže na odlagališta.
U ovom radu je opisan postupak gospodarenja otpadom u gradu Sisku. Poseban naglasak odnosi se na sortiranje miješane ambalaže, odnosno izdvajanja korisnih frakcija te njihova priprema za ponovnu uporabu. Dodatno je opisan proces odlaganja otpada sa naglaskom na praćenje emisija u okoliš.In order to preserve the environment and human health, and with regard to European and Croatian legislation, the collected waste must be reduced to a minimum. The first step is the collection of waste, i.e. raw materials and processing in terms of sorting according to type, fractions and properties. The next step is preparation for reuse, such as baling or shredding and transport to an authorized recycler. The goal of the waste management system is to reduce the amount of waste disposed on landfills.
This paper describes the process of waste management in the city of Sisak. Special emphasis is placed on the sorting of mixed packaging, that is, the separation of useful fractions and their preparation for reuse. Additionally, the process of waste disposal is described with an emphasis on monitoring emissions into the environment
Communication skills of occupational safety experts
No full textKomunikacijske vještine imaju ključnu ulogu u efikasnom obavljanju uloge stručnjaka zaštite na radu. Ovaj završni rad istražuje važnost komunikacijskih vještina u kontekstu stručnjaka zaštite na radu. U radu je provedena anketa kako bi se procijenila iskustva i mišljenja stručnjaka zaštite na radu o važnosti komunikacije. Ovaj rad naglašava potrebu za kontinuiranim usavršavanjem komunikacijskih vještina stručnjaka zaštite na radu kako bi se osigurala efikasna razmjena informacija i podizanje svijesti o važnosti sigurnosti na radu među radnicima.Communication skills play a key role in the effective performance of the role of occupational safety experts. This final paper explores the importance of communication skills in the context of occupational safety experts. A survey was carried out in order to assess the experiences and opinions of occupational safety experts on the importance of communication. This paper stresses the need to continuously improve the communication skills of occupational safety professionals in order to ensure efficient exchange of information and raise awareness of the importance of occupational safety among workers
The role of recycling aluminum cans in a circular economy
No full textZavršni rad obrađuje temu kružnog gospodarstva s naglaskom na ulogu metalurgije i recikliranja aluminijske ambalaže u kružnom gospodarstvu.
U prvom dijelu dan je pregled ekonomskih, ekoloških i drugih aspekata vezanih uz recikliranje aluminijskih proizvoda, ali i na smanjenje ovisnosti o ograničenim prirodnim resursima. Naglasak je stavljen na aluminijske limenke, jer čine većinu oporabljenih aluminijskih proizvoda, a njihovim recikliranjem postiže se izuzetno kvalitetna talina aluminija kao osnova za formiranje gotovih proizvoda lijevanjem ili novih legura daljnjom obradom taline.
U drugom dijelu rada opisuje se dobar primjer prakse u recikliranju aluminijskih limenki. U dvije odvojene faze prerade ispitana su mehanička svojstva, kemijski sastav i strukturna analiza ostvarenih talina. Navedenim ispitivanjima utvrđeno je da recikliranjem aluminijskih limenki, pored izuzetno pozitivnih ekonomskih i ekoloških pokazatelja, dobivamo veoma čist aluminij, upotrebljiv kao dezoksidans u proizvodnji čelika, ali i kao odličnu sirovinu za proizvodnju novih aluminijskih legura.The final paper deals with the topic of the circular economy with an emphasis on the role of metallurgy and recycling of aluminum packaging in the circular economy.
In the first part, there is an overview of economic, ecological and other aspects related to the recycling of aluminum products, but also on the reduction of dependence on limited natural resources. Emphasis is placed on aluminum cans, because they make up the majority of recycled aluminum products, and their recycling results in an extremely high-quality aluminum melt as the basis for the formation of finished products by casting, or development of new alloys by further processing of the melt.
In the second part of this final paper, a good example of practice in recycling aluminum cans is described. In two separate stages of processing, the mechanical properties, chemical composition and structural analysis of the resulting melts were tested.
The above mentioned experiments have concluded that by recycling aluminum cans, in addition to extremely positive economic and ecological indicators, we obtain very pure aluminum, which can be used as a deoxidizer in the production of steel, but also as an excellent raw material for production of new aluminum alloys
Investigation of recycled AlSi9Cu3(Fe) alloy
No full textDue to European Union legislative and recently the difficulties faced by casting manufacturers, more and more attention is focused on raw materials. Raw materials are found at the beginning of all industrial value chains. These critical (CRMs) and strategic raw materials (SRMs) are often indispensable inputs for a wide set of strategic sectors including renewable energy, the digital industry, the space and defence sectors, health sector all connected to the metal industry. Aluminium and its alloys plays an important CRMs and SRMs. Standard aluminium alloy AlSi9Cu3(Fe) (EN AC 46000) is widely used in the automotive and transport industry. High mechanical properties such as strength and hardness, as well as elongation and corrosion resistance are the main advantages of AlSi9Cu3(Fe) alloy. The functional and useful properties of aluminium cast alloys are dependent from the chemical composition, melt treatment, solidification rate, casting process and potential heat treatment. Most of them are conditioned by the microstructural development. This paper investigates the recycling potential of AlSi9Cu3(Fe) alloy using completely return material without any additions or refining. The presence of wide range of alloying elements AlSi9Cu3(Fe) alloys indicates development α-Al15Si2M4 (M= Cr, Fe, Mn, Mo), β-Al5FeSi, Al2Cu and even more complex one such as Al3Cu2Mg9Si7 using theoretical modelling. Complex solidification path indicates primary aluminium αAl, eutectic phase αAl+βSi, intermetallic phase on the iron base in Al5FeSi and “Chinese script” morphology, intermetallic phase on the magnesium and copper base such as Mg2Si and Al2Cu, and complex intermetallic such as Al8Mg3FeSi2 and Al5Mg8Si2Cu2 phases. Thermodynamic effects of elements interaction during solidification sequence significantly influence on solidification path and manner. Although the investigated samples maintain high tensile strength and elongation, slight degradation in chemical composition and therefore in thermodynamic effect, significantly influence on microstructure development. In despite of chemical composition degeneration, obtained microstructure was correct and therefore justified achieved high mechanical properties. Therefore, on the base of thermodynamic and microstructural investigation of the secondary AlSi9Cu3(Fe) alloy indicated raw material as a quality charge material with good application and recycling potential
Effect of dynamic formation of multiphase slag skin on heat transfer and magneto-hydrodynamic flow in electroslag remelting process
No full textDuring the electroslag remelting (ESR) process, the effect of dynamic formation of slag skin on magneto-hydrodynamic multiphase flow and temperature field is studied using a 2-D axisymmetric model. The electromagnetic field is described by user-defined functions. The dynamic formation and distribution of multiphase slag skin, as well as the interface between slag and metal, are investigated by using the volume of fluid (VOF) model and the dynamic meshing method. Especially, the effect of slag skin/air gap on heat transfer characteristics is considered and developed by user-defined functions. The results show that the thickness of slag skin at the interface between slag and metal increases as the axial distance from free surface of slag rises, reaching a maximum of about 25 mm. With the height of ingot increasing, the thickness of slag skin drops to 17 mm. When the current changes from 2.0 kA to 3.0 KA in the ESR process, the current density, Joule heat, velocity and temperature increases. In the meanwhile, the slag skin becomes thinner and the melt pool becomes deeper. The vibration of electrode has a weak effect on the formation behavior of slag skin, and only has effects on formation of metal droplet and velocity field
The role of deoxidation in steel production
No full textDo danas čelik je najviše korišteni metalni materijal, a koristi se i više nego što se ikada koristio. U 21. stoljeću upotreba čelika raste, godišnje se proizvede preko milijardu tona. Prema podatcima Svjetskog udruženja za čelik ukupna svjetska proizvodnja sirovog čelika u 2022. godini iznosila je 1878 Mt. Čelik definiramo kao „zeleni materijal“, jer njega recikliramo više od svih drugih materijala. Za višestruku upotrebu „zelenog materijala“ su zaslužna njegova svojstva poput rastezljivosti, žilavosti, čvrstoće, otpornosti na koroziju i toplinu, itd. Primjena mu je u većini djelatnosti, kao npr. u prometu (za izradu mostova, automobila, željezničkih pruga), u medicini (kirurški instrumenti), građevinarstvu (profili, šipke, žice) itd.
Tijekom proizvodnje čelika u oksidacijskim uvjetima, velika količina kisika ostaje u čeliku te se ona mora smanjiti u svrhu eliminiranja grešaka u lijevanim poluproizvodima. Dezoksidacija čelika se odvija dodatkom elemenata koji imaju visok afinitet prema kisiku, poput aluminija, silicija, kalcija itd. Ti elementi se nazivaju dezoksidanti i dodaju se u lonac, a njihova uloga je da otopljeni kisik u čeliku vežu u stabilne okside koji će se kasnije u određenoj mjeri ukloniti iz čelika. U ovom završnom radu opisat će se ukratko postupci proizvodnje čelika, navest će se podjela čelika s obzirom na stupanj dezoksidacije (umireni, poluumireni i neumireni) te će se objasniti postupak i načini dezoksidacije. Također, opisat će se dezoksidacija pojedinim elementima i dati naglasak na važnost dezoksidacije u samome procesu proizvodnje kvalitetnog čelika.To this day, steel is the most used metal material, and it is used more than ever before. In the 21st century, the use of steel is growing, more than a billion tons are produced annually. According to data from the World Steel Association, the total global production of crude steel in 2022 was 1878 Mt. We define steel as a "green material" because we recycle it more than any other material. The multiple use of "green material" is due to its properties such as elongation, toughness, strength, corrosion resistance and heat resistance etc. It is used in many areas, such as transport (for the construction of bridges, cars, etc.), medicine (surgical instruments), construction industry (profiles, bars, wires), etc.
During the production of steel under oxidizing conditions, a large amount of oxygen remains in the steel and it must be reduced in order to eliminate defects in cast semi – finished products. Deoxidation of steel takes place by adding elements that have a high affinity for oxygen, such as aluminum, silicon, calcium, etc. These elements are called deoxidizers and are added to the ladle, and their role is to bind dissolved oxygen in the steel into stable oxides that will later be removed from the steel to a certain extent. In this bachelor thesis, the steel production procedures will be briefly described, the division of steel according to the degree of deoxidation (killed steel, semi – killed steel and rimmed steel), and the procedure and methods of deoxidation. Also, the deoxidation with individual elements will be described and emphasis will be placed on the importance of deoxidation in the production process of quality steel
Cleaner energy for sustainable circular economy implementations: Integrated energy, water and environment systems
No full textThis is the first Virtual Special Issue (VSI) of Cleaner Energy Systems. It contains research articles originating from some of the papers presented at the 16th Conference on Sustainable Development of Energy, Water and Environmental Systems (SDEWES), which was held both onsite and online in Dubrovnik, Croatia, from 10 to 15 October 2021, related to the scope of Cleaner Energy Systems. The main target of this VSI, which is in line with the conference goals, is to cover topics that focus on preventing the generation of waste while increasing efficiencies in the use of energy, water, resources, and human capital. The articles in this VSI present extended developments as follow-ups from the conference papers. The treated topics are central to making energy systems cleaner – heat transfer and heat exchanger efficiency, Heat Integration and District Heating, policies for promoting the use of renewable energy, and energy efficiency of buildings
Technological and structural calculation of the recuperator for air preheating on the cupola furnace
No full textIn cases of melt preparation for larger tonnage production, the most common melting method used in iron casting plants is the cupola furnace. The main advantages of cupola furnaces compared to electric ones are: less sensitive to low quality charge materials and contaminants, oxidation and reduction reactions take place within and above the melt zone during cupola melting, which allows the use of highly oxidized and low quality scrap material, lower prices of alloys and non-metallic additions. The metallurgical process in the cupola furnace can be intensified by preheating the air that is blown into the working space of the furnace through nozzles. In addition to increasing aggregate productivity, reduced coke consumption and higher melt temperatures are also achieved. For this purpose, tubular recuperators are usually used, which exploit the enthalpy of the output cupola gases, and in some cases also the enthalpy of natural gas combustion gases. For the cupola furnace with a capacity of 3 t/h, the technological and construction calculation of the recuperator sections was carried out. The calculation is based on the experimental data of furnaces and recuperators that are used in practice. It consists of the calculation of the combustion of natural and cupola gases and the calculation of the construction of three recuperator sections. In the first section, which is connected to the nozzles, i.e. in the zone of the highest temperatures of the combustion gases, the final heating of the air is achieved before entering the cupola furnace, in the second section the cupola gases are reheated before its combustion, while in the third section the air is heated from the initial ambient temperature. The design of the tubular heat exchanger with counter-flow of flue gases and air, composed of steel U-tubes, was adopted