Repository of Faculty of Metallurgy University of Zagreb
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Metallurgy development: Discovery and utilization of aluminum through history
No full textSince the early human civilizations, the discovery and use of new materials and the development of new technologies have changed culture and influenced the development of the modern human environment. At the same time, innovations based on scientific discoveries and technological advances are connected to increasingly complex social and political structures and international relations, which have an impact on economic growth and social benefits. Unfortunately, the human capacity for technological and strategic innovation has most often been demonstrated under stressful conditions inspiring the phrase “necessity is the mother of invention”. The goal of this review is to examine the necessity that compelled mankind to search for metals, primarily focusing on the discovery of aluminum and the challenges represented by the complex nature of its minerals. Although men’s first contact with metal initiated with native copper and meteoritic iron, bronz was the first metallic material significantly impacting human society. The experiments with its chemical composition led to the development of metallurgical processes such as smelting, refining, and casting as well as mechanisms of economics and communication. The accidental discovery of iron in the process of copper ore refining gave mankind greater control over its environment, resulting in increased population and expanded settlements. Aluminum, as a brilliant white metal, was introduced to the world through the works of Wöhler and Deville. However, it became commercially available after electrolysis was discovered by Charles Martin Hall on February 23rd 1886 in a woodshed using home- made battery. A few months later, the similar results were obtained by Paul Louis Toussaint Héroult, so the process for electrolytic production of aluminum bears both of their names. As a symbol of modernity aluminum is used today in the automotive, aerospace, railway, marine, electric, and architectural applications. At the end of this work, it is superfluous to ask whether humanity would have been able to explore the universe and reach the stars if it had been restricted by stone, bones and wood
Quality assessment of the AlSi9Cu3(Fe) alloy with regard to recycling ratio
No full textThe most common aluminum alloy in automotive industry is the AlSi9Cu3(Fe) alloy due to relatively high mechanical properties, fluidity and resistance to hot cracking. The mechanical properties of aluminium cast alloys are strongly dependent from the microstructure developed on the base of chemical composition and casting process with the emphasis on solidification sequence. Green production is an imperative in nowadays industry. Usage of secondary charge material comprehend to the green production certification with 0% CO2 footprint when own return has been used. Maintaining the alloy quality with regard to functional properties while promoting green production makes economical production imperative. In this research, modeling of the solidification sequence in equilibrium and non-equilibrium conditions was carried out and compared with the obtained microstructure for a conventional AlSi9Cu3(Fe) alloy and alloy made of 100% return charge material. Modelled equilibrium phase diagram enables solidification sequence prediction which can be easily confirmed using metallographic analysis. Modeling of solidification sequence revealed some differences in solidification path. Microstructural investigation of obtained samples confirms the presence of following phases: primary aluminium evolution (αAl), iron phases (Al5FeSi, Alx(Fe,Mn)yCuuSiw), primary eutectic phase (αAl+βSi) as well as other intermetallic phases as Al7Cu2Mg, Al5Mg8Si6Cu2, Al2Cu and Al8Mg5FeSi2. The comparison of the obtained results indicates a lowering of the main alloying element Si and thus an influence on the displacement of the solidification sequence equilibrium. Despite the observed differences in the solidification path, the comparison of the microstructures for both cases (conventional and 100% return alloy) does not reveal a degradation in the quality of the alloy. The quality assessment thus indicates that production with 100% recycled AlSi9Cu3(Fe) charge material meets all functional properties in the automotive industry
Influence of homogenization on chemical properties of aluminum alloy EN AW-5083
No full textThe aim of this paper is to estimate the chemical composition homogeneity of six aluminum EN AW-5083 alloy slabs
produced by the Direct Chill Process in as-cast and homogenized condition. The homogeneity assessment is based on the
content of magnesium (Mg) as a main alloying element.
The experimental part of this work is based on the analysis of Mg content on previously defined positions within the
cross-sectioned plates taken from the slabs’ fronts and rears. The determination of chemical composition homogeneity
was based on the Latin square experiment design. The statistical processing enabled the determination of the difference
in the cross-section of each individual plate. The chemical homogeneity of the slabs as a whole was evaluated by
comparing the results from the slabs’ fronts and rears. The significance and influence of homogenization on the
magnesium content was quantified by comparison of the obtained measurement results for the as-cast and homogenized
state of the tested EN AW-5083 alloy.
The obtained results indicate that the Mg content of all melts and all average values of magnesium content in as-cast and
homogenized state per individual charges are within the values prescribed by the norm. A small deviation in the
magnesium content was detected in the first three tested alloys in the homogenized state (3112, 3113, 3114) as well as
decrease in Mg content from the melt to as-cast and homogenized slabs due to oxidation loss. The average value of Mg
loss for all six charges is: during casting from the amount of Mg in the melt to the cast slab 0.18 %, additional Mg loss of
0.14 % during the homogenization, while the average total loss of magnesium is 0.32 %
Application of characterisation methods in the development of biomedical titanium alloys
No full textBiomaterials are becoming an increasingly important research topic over time as they are used to replace parts and functions of the human body, helping to improve the quality of human life. Titanium alloys are particularly important for the development of new biomaterials. Commercial pure titanium and its alloys are used as essential structural biomaterials in the manufacture of implants due to their excellent biocompatibility, good corrosion resistance and mechanical strength. However, studies have shown that aluminum and vanadium ions are released in alloys such as Ti-6Al-4V, which can cause health problems over time. Because of the problems that occur, researchers are working to improve the properties of titanium alloys by adding new elements. In most cases, different metals are added to titanium and it is known that with the presence of different metals, the properties of titanium also change. All biomedical titanium alloys must undergo various testing procedures before they can be used. The article describes the characterisation methods used in the development of titanium alloys, such as: light and scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction analysis, differential scanning calorimetry, differential thermal analysis. The reliability of the results depends on the methods used and the avoidance of errors in the characterisation of biomedical alloys in order to reach better conclusions and produce alloys of the highest quality desirable for use in the human body
Influence of thermal microclimate factors on workers` health and the working environment
No full textOd kada je rada i svijesti za zdravljem radnika, od tada se čovječanstvo bavi rješavanjem što sigurnijeg i mikroklimatski što zdravijeg okoliša te toplinski što udobnijim radnim prostorom. Mikroklimatski uvjeti su vrlo bitan element očuvanja ljudskog zdravlja i zadovoljstva na radnom mjestu. Drugim riječima, nepovoljni mikroklimatski uvjeti dovode do zdravstvenih problema koji rezultiraju narušavanjem zdravlja radnika i/ili pojave profesionalnih bolesti zbog čega nepovoljno utječu na radnu sposobnost te dovode do smanjenja učinkovitosti i proizvodnosti samog poduzeća. Mikroklimatski čimbenici se dijele na toplinske te kemijske i biološke. Budući je tema ovoga rada utjecaj toplinskih mikroklimatskih čimbenika na zdravlje radnika i radni okoliš, u radu su pobliže objašnjeni toplinski mikroklimatski čimbenici koji obuhvaćaju: temperaturu zraka, temperaturu zračenja plohe, brzinu strujanja zraka, vlažnost zraka i tlak zraka. Nadalje, opisani su uređaji i postupak mjerenja nabrojenih čimbenika te izrada procjene rizika. Također, definiran je pojam toplinske udobnosti, kao i faktori koji utječu na nju te su obrađeni mogući poremećaji u regulaciji temperature. Opisano je kojim indeksima se ocjenjuje djelovanje topline okoline na udobnost radnika te su navedene mjere zaštite od toplinskih mikroklimatskih čimbenika.
Za zadovoljstvo radnika na radnom mjestu vrlo je bitna njihova sigurnost i kvaliteta učinjenoga, jer samo zadovoljan radnik može biti učinkovit radnik.Since the beginning of work and awareness of the health of workers, since then mankind has been dealing with the solution of the safest and microclimate-healthy environment possible, and the most thermally comfortable working space.
Microclimatic conditions are a very important element of preserving human health and satisfaction at the workplace. In other words, unfavorable microclimate conditions lead to health problems that result in the deterioration of workers' health and/or the appearance of occupational diseases, which adversely affect the ability to work and lead to a decrease in the efficiency and productivity of the company itself. Microclimatic factors are divided into thermal, chemical and biological factors. Since the topic of this paper is the influence of thermal microclimatic factors on the health of workers and the working environment, thermal microclimatic factors are explained in more detail in the paper, which include: air temperature, surface radiation temperature, air flow speed, air humidity and air pressure. Furthermore, the devices and the procedure for measuring the listed factors and creating a risk assessment are described. Also, the concept of thermal comfort is defined, as well as the factors that influence it, and possible disorders in temperature regulation are addressed. It is described which indices are used to assess the effect of ambient heat on worker comfort, and protection measures against thermal microclimate factors are listed.
For the satisfaction of workers at the workplace, their safety and the quality of work are very important, because only a satisfied worker can be an efficient worker
Comparison of the application of 2D and 3D digital image correlation in the investigation of deformations of metallic materials
No full textUpotreba aluminija i njegovih legura je danas gotovo nezaobilazna tema. Poznato je da pojedine legure aluminija pokazuju određeni nehomogeni tok materijala prilikom njihovog oblikovanja plastičnom deformacijom u gotove proizvode, a povezuju se s pojavama Lüdersovih linija i/ili Portevin-Le Chatelier efekta. Prilikom istraživanja ovih pojava danas se uz statički vlačni pokus primjenjuju beskontaktne metode istraživanja kao što su metoda digitalne korelacije slike i termografija. Napretkom tehnologije napredovale su i metode istraživanja, tako su danas dostupne razne metode digitalne korelacije slike. U ovom završnom radu korištene su 2D i 3D metoda za korelaciju digitalne slike. Istraživanjima su dane usporedbe osjetljivosti dvaju različitih metoda pri praćenju i mjerenju promjena deformacije i brzine deformacije. Iz rezultata kvalitativne i kvantitativne analize zaključeno je kako pri određivanju deformacije nema razlike između korištenih metoda, dok u slučaju mjerenja brzine deformacije postoje određene razlike.Today, use of aluminum and its alloys is almost unavoidable. It is well known that certain aluminum alloys, during their plastic deformation into finished products, exhibit a certain inhomogeneous flow of material associated with the appearance of Lüders bands and/or the Portevin-Le Chatelier effect. In the study of these phenomena, non-contact investigation methods, such as the digital image correlation and thermography, are used in addition to the static tensile test. The investigation methods have also evolved with the technological progress, so today there are different versions of methods that use digital image correlation. In this work, 2D and 3D methods were used for digital image correlation. The research provided comparison of the sensitivity of two different methods in monitoring and measuring deformation and strain rate changes. From the results of qualitative and quantitative analysis, it was concluded that there is no difference between the systems used in determining deformation, while there are some differences in measuring strain rate
Active fire protection measures in the Sisak oil refinery
No full textU radu su prikazane aktivne mjere zaštite od požara u rafineriji nafte Sisak. Aktivne mjere
zaštite od požara u rafineriji nafte Sisak sastoje se od stabilni i polustabilnih sustava, sustava
hidrantske mreže, vatrogasnih aparata, stabilnih i mobilnih bacača te vatrodojave. Glavna
zadaća aktivnih mjera zaštite od požara je rano otkrivanje požara, dojavljivanje korisnicima
prostora i hitnim službama te početno gašenje požara i hlađenje okolnih objekata. Sigurnost i
zaštita od požara temeljna je obaveza svakog poduzeća, objekta i prostora. Cilj ovog rada je da
se upoznamo sa aktivnim mjerama zaštite od požara u rafineriji nafte Sisak te da ukažemo na
njihove prednosti i nedostatke.The paper presents active fire protection measures in the Sisak oil refinery. Active fire
protection measures in the Sisak oil refinery consist of stable and semi-stable systems, hydrant
network systems, fire extinguishers, stable and mobile water gun and fire alarms. The main task
of active fire protection measures is the early detection of fires, notification of the area to users
and emergency services, and initial fire extinguishing and cooling of surrounding buildings.
Safety and fire protection is a fundamental obligation of every company, facility and space. The
aim of this paper is to familiarize ourselves with active fire protection measures in the Sisak oil
refinery and to point out their advantages and disadvantages
Influence of the stretching rate on the appearance of the Portevin-Le Chatelier effect in the AlMg alloy
No full textAluminij i legure na bazi aluminija u današnje vrijeme su neizostavni materijali o kojima ovisi industrija na globalnom nivou. Određene aluminijske legure, poput AlMg legura pokazuju nehomogenu, lokaliziranu deformaciju pri određenim temperaturama i brzinama deformacije poznatu kao Portevin–Le Chatelier (PLC) efekt. Portevin–Le Chatelier efekt pridonosi smanjenju duktilnosti materijala i pojavi grešaka na površini materijala što je naravno nepoželjno i predstavlja nerješiv problem, stoga se sve veća pažnja obraća na proučavanje pojave PLC efekta kako bi se navedene posljedice koje PLC efekt ostavlja minimizirale ili u potpunosti uklonile. Kod proučavanja utjecaja brzine razvlačenja na pojavu Portevin–Le Chatelier efekta kod AlMg4,5 legure u ovom diplomskom radu korištene su metode digitalne korelacije slike i infracrvene termografije paralelno sa statičkim vlačnim ispitivanjem primjenom konstantnih brzina razvlačenja 10 mm/min, 20 mm/min i 50 mm/min te konstantnim porastom naprezanja od 5 MPa/s i 10 MPa/s. Metodama digitalne korelacije slike i termografije je ustanovljeno kako do pojave PLC efekta dolazi pri svim primijenjenim brzinama razvlačenja i porastima naprezanja te kako se PLC linije formiraju kroz cijeli period plastične deformacije sve do loma uzorka. Također, kako je i za očekivati, ustanovljeno je kako s porastom brzine razvlačenja dolazi i do porasta brzine deformacije.Aluminum and aluminum based alloys are nowdays irreplaceable materials on which industry worldwide depends. Certain aluminum alloys, such as AlMg alloys exhibit inhomogeneous, localized deformation at certain temperatures and strain rates known as the Portevin-Le Chatelier (PLC) effect. The Portevin-Le Chatelier effect contributes to the reduction of the materials ductility and the appearance of defects on the surface of material, which is obviously undesirable and represents an unsolvable problem. Therefore, more attention is paid to the study of the occurrence of the PLC effect, in order to minimize or completely eliminate the above consequences of the PLC effect. In this thesis, digital image correlation and infrared thermography methods were used simultaneously with static tensile testing in the study of the influence of stretching rate on the occurrence of the Portevin-Le Chatelier effect in AlMg alloy. The static tensile test was performed with constant stretching rates of 10 mm/min, 20 mm/min and 50 mm/min and with constant stress increase of 5 MPa/s and 10 MPa/s. Using the digital image correlation and infrared thermography methods it was found that the PLC lines formed throughout the entire period of plastic deformation until the specimen fractured. Also, as expected, it was found that as the stretching rate increased, the deformation rate also increased
The role and importance of slag in metallurgy
No full textTroska je otpad/nusproizvod koji nastaje pri procesu proizvodnje metala. Ima veliku ulogu u metalurškoj industriji, prvenstveno zbog toga što u nju odlaze nečistoće tijekom taljenja metala, čime se poboljšavaju svojstva metala. Ona služi i kao izolacijski sloj, kako kisik ne bi došao do tekućeg metala, jer kada dođe do toga, nastaju mjehurići tijekom hlađenja, zbog kojih dolazi do slabljenja strukture metala. Ona ima veliku ulogu i u zadržavanju temperature tijekom procesa, inače će se metal prebrzo hladiti i neće se odvojiti sve nečistoće u samu trosku. Također je bitna i u cestogradnji i poljoprivredi. U cestogradnji se pokazala kao dobra, ali i bolja zamjena za uobičajene eruptivne agregate koji se koriste za asfalt, dok u poljoprivredi ima jako puno primjena, od anorganskog dodatka tlu čime se ono obogaćuje, preko toga da poboljšava općenitu kvalitetu tla te stabilizatora teških metala u tlu.
Stoga, u ovom radu navedene su vrste čelika i postupci njegovog dobivanja s naglaskom na elektropećni postupak. Detaljno je objašnjena uloga i važnost troske u metalurgiji, kao i njezina široka primjena. Također su navedene vrste i svojstva troske, kao i najvažnije teorije nastanka troske
Morfologija biorazgradnje polimernih mješavina
No full textIzvrsna svojstva polimernih materijala i danas ih čine gotovo nezamjenjivim materijalima u svakodnevnoj uporabi. No svijest o ograničenim izvorima nafte kao i rastuća svijest o očuvanju okoliša, stavlja sve veći naglasak na uporabu polimernih materijala dobivenih iz obnovljivih izvora. Upravo škrob, kao prirodni materijal ima velik potencijal u primjeni zbog svoje prirodne biorazgradivosti u širokom rasponu okruženja, niske cijene te lake dostupnosti. U ovom istraživanju naglasak je stavljen na biorazgradnju polimernih mješavina polietilena i termoplastičnog škroba. Biorazgradnja provedena je procesom kompostiranja u adijabatskom reaktoru tijekom 16 dana. Biorazgradnja polimernih mješavina pratila se promjenom mase kao i praćenjem promjene strukture svjetlosnim (LM) i pretražnim elektronskim mikroskopom (SEM). Procesom kompostiranja došlo je do potpune biorazgradnje TPS-a. TPS zbog hidrofilnog karaktera, upija i zadržava vlagu iz kompostne mase, što pridonosi bržoj biorazgradnji polimernih mješavina. LM-om kao i SEM-om potvrđena je brža i prodornija biorazgradnja polimernih PE /TPS mješavina i to naglašeno s većim udjelom dodanog TPS-a