Repository of Faculty of Metallurgy University of Zagreb
Not a member yet
491 research outputs found
Sort by
Properties of continuously casted Cu-Al alloy
No full textIn this work are shown properties of continuously casted Cu – 9.1Al alloy before and after heat treatment. The continuously cast cylindrical bar with 8 mm diameter was produced using the device for the vertical continuous casting which is connected with the vacuum induction furnace. Heat treatment was consisted of annealing at 900 °C/30 minutes and water quenching. Microstructural analysis was performed by optical microscopy (OM), scanning electron microscopy (SEM) equipped by device for energy dispersive spectroscopy (EDS) and using differential scanning calorimeter (DSC). Also, hardness and mechanical properties were measured. EDS analysis confirmed that as-cast state of Cu – 9.1Al alloy is successfully done and alloy with homogeneous composition was produced. Optical and scanning electron microscopy showed existence of dual-phase α+β microstructure, which keeps after heat treatment but with certain sporadic changes of α - phase shape. DSC analysis on all samples presented one endothermic change of the heat flow during the heating, which probably represents α→β transformation and one exothermic change of the heat flow during the cooling which probably represents β→α transformation. The effect of heat treatment on the hardness and yield strength values is insignificant, while the tensile strength decreases with annealing
Influence of microstructure and strain rate on the beginning of cold deformation in niobium microalloyed steel
Get PDFČelik je danas najrasprostranjeniji materijal u svijetu. Istraživanja su pokazala kako mikrolegirani čelici sa titanom ili niobijem imaju bolja mehanička svojstva od ostalih čelika. Dobra mehanička svojstva podrazumijevaju visoku žilavost, deformabilnost, otpornost i čvrstoću. Takva svojstva postižu se odgovarajućom kombinacijom kemijskog sastava i parametara termomehaničke obrade. U ovom radu ispitano je ponašanje niskougljičnog čelika mikrolegiranog sa 0.035% niobija na početku plastičnog toka materijala. Ispitivanja su provedena statičkimvlačnim pokusom, digitalnom korelacijom slike, te metalografskim ispitivanjima. Dobiveni rezultati su pokazali da brzina razvlačenja ima utjecaj na početak plastičnog toka niobijem mikrolegiranog čelika dok mikrostrukturna ispitivanja nisu dala jasnu sliku o utjecaju mikrostrukture. Daljnja istraživanja trebala bi dati odgovore kako utječe mikrostruktura na početak plastičnog toka niobijem mikrolegiranog čelika.Today, steel is the most widespread material in the world.Studies have shown that microalloyed steel with titanium or niobium have better mechanical properties than other steels. Good mechanical properties include high toughness, deformability, resistance and strength.Such properties are achieved by an appropriate combination of chemical composition and thermomechanical processing parameters. In this bachelor thesis has been examined the behavior of low-carbon steel microalloyed with 0.035% niobium on the beginning of plastic flow of material. Researches were conducted by static tensile test, digital image correlation and metallographic observation. Obtained results have shown that the stretching rate has an influence on the start oftheplasticflowofniobiummicroalloyedsteelwhilethemicrostructuralobservationdidnotgive a clear insight of the influence of the microstructure. Further research should provide answers on how the microstructure influences on the beginning of the plastic flow of niobium microalloyed steel
Electric arc furnace dust as a valuable production residue from the steel production process
Get PDFIako je elektropećna prašina razvrstana kao opasni otpad zbog prisutnosti teških metala, može se iskoristiti u razne svrhe što predstavlja prihvatljiviji način njenog zbrinjavanja nego što je odlaganje na za to predviđena odlagališta, čime metali prisutni u prašini ostaju neiskorišteni. U radu je dan pregled nastanka elektropećne prašine, njenih fizikalno – kemijskih svojstava i moguće uporabe. Imajući u vidu fizikalno – kemijska svojstva prašine i visok sadržaj željeza, veoma pogodno rješenje je njeno vraćanje u matični proces za dobivanje čelika. Osim toga, prašina se može koristiti u industriji neželjeznih metala za dobivanje teških metala kao što je cink te u nekim drugim industrijama (npr. za proizvodnju cementa, keramike, boja, itd.)
Effect of heat treatment on corrosion properties of CuAlNi shape memory alloy
Get PDFThe effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% NaCl solution at pH 7.4 and 37 °C by open circuit potential measurements, polarisation techniques, and electrochemical impedance spectroscopy. Investigations were performed on CuAlNi alloy samples in as-cast state and after heat treatment procedure containing annealing at 850, 885 and 920 °C followed by water quenching. Electrochemical impedance measurement results indicate that heat treatment of CuAlNi alloy leads to the increase in charge transfer resistance and surface layer resistance and the decrease in values of capacitance of the double and surface layers, indicating higher corrosion resistance compared with the as-cast CuAlNi alloy. The increase in polarisation resistance and the decrease in corrosion current density of heat-treated CuAlNi alloy also suggest beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Optical microscopy, SEM/EDX and XRD analysis of samples surface after polarisation measurements show the occurrence of pitting corrosion on the electrode surfaces, with the existence of CuCl2, AlCl3 and Cu2Cl(OH)3 compounds as the surface corrosion products
Efficiency of adsorption of copper (II) ions on waste steel shot
No full textČelična sačma koristi se u ljevaonicama za čišćenje površine odljevaka prije nanošenja odgovarajuće zaštite ili prije stavljanja na tržište. Postupak čišćenja odvija se na taj način da čestice sačme velikom brzinom udaraju u površinu odljevka. Prilikom tog postupka dio kuglica sačme biva oštećen i postaje otpad. U ovom radu istraživana je mogućnost uporabe otpadne čelične sačme kao adsorbensa za uklanjanje Cu(II) iona iz vodene otopine. Nakon adsorpcijskog procesa određivana je efikasnost adsorpcije ovisno o početnim koncentracijama otopine Cu(II) iona. Rezultati su pokazali da ova vrsta otpada ima vrlo veliku efikasnost uklanjanja (adsorpcije) Cu(II) ion, čak i preko 80 % što upućuje na zaključak da bi se ova vrsta otpada mogla koristiti kao adsorbens. Na ovaj način bi se omogućilo korištenje, a samim time i smanjivanje ove vrste otpada
The influence of pH and electrolyte temperature on corrosion behaviour of CuAlMnTi alloy ribbons in NaCl solution
Get PDFThe influence of pH and temperature of 0.9% NaCl solution on corrosion behavior of CuAlMnTi alloy ribbons, produced by rapid solidification using melt spinning method, were investigated by electrochemical methods. Open circuit potential measurement, linear and potentiodynamic polarization were employed during the investigation, and the measurements were conducted in the electrolyte temperature of 10, 24, 37 and 50 oC and in solution pH of 7.4, 5.4 and 3.4. In has been found that corrosion rate generally increase with increasing the temperature of the electrolyte while the influence of pH change on CuAlNiTi ribbon corrosion is little less pronounced. After polarization measurements CuAlNiTi ribbon surfaces were investigated with light microscope and with SEM/EDS analysis
Analysis of the microstructure of steel sheets for the automotive industry joined by spot welding
Get PDFU radu je dan teorijski pregled postupaka elektrootpornog zavarivanja s detaljnijim opisom
postupka elektrootpornog točkastog zavarivanja. Opisan je osnovni fizikalni princip
elektrootpornog zavarivanja te je istaknut utjecaj ključnih parametara na kvalitetu zavarenog
spoja. Navedeni su uređaji i vrste elektroda primijenjeni kod elektrootpornog točkastog
zavarivanja. Opisan je proces formiranja točkastog zavara i navedene su njegove karakteristične
strukture.
U eksperimentalnom dijelu rada izrezane su trake limova različitih proizvođača motornih vozila
(Opel, Peugeot i Toyota) i u uzdužnom smjeru trake na četiri mjesta zavarene elektrootpornim
točkastim zavarivanjem. Nakon zavarivanja traka, limovi su rasječeni po sredini zavarenog
spoja, zaliveni u vodljivu masu, brušeni i polirani te je provedena metalografska analiza
osnovnog lima i zavarenih limova na mjestu točkasto zavarenog spoja. Nakon provedene
diskusije rezultata metalografskih ispitivanja zaključilo se da se prijenosnim uređajem za
točkasto zavarivanje mogu postići mikrostrukturne karakteristike zavarenog spoja koje se postižu
boljim uređajima s mogućnostima regulacije ulaznih parametara.The paper provides a theoretical overview of electric resistance welding procedures with a
more detailed description of the electric resistance spot welding procedure. The basic physical
principle of electric resistance welding is described and the influence of key parameters on the
quality of the welded joint is emphasized. Devices and types of electrodes used for electric resistance spot welding are mentioned. A process of the formation of a spot welded joint is described and its characteristic structure are mentioned.
In the experimental part, the strips of sheets of various motor vehicle manufacturers (Opel,
Peugeot and Toyota) are cut and in the longitudinal direction of the strip in four places by
electric resistance spot welding are welded. After welding the strips, the sheets are cut off at the
centre of the welded joint, suffused in the conductive mass, grinded and polished and a
Metallographic analysis of the base sheet and welded sheets on the point of the spot welding joint are performed. After conducted discussion of the results of the metallographic tests, it was concluded that the portable spot welding device could achieve the microstructural characteristics of welded joints which are achieved by better devices with the possibilities of regulation of the input parameter
Processing of the waste sludge from waste water treatment plants
Get PDFUloga pročišćivaća voda ima veliki značaj od samih početaka civilizacije. Kao negativan produkt pročišćavanja voda je mulj, a njegov sastav uvelike ovisi o vrsti vode koja se pročišćava. Odgovarajućom obradom i postupcima uklanjanja svih opasnih čimbenika iz mulja, od kojih pojedini mogu biti vrlo skupi,dobiva se mulj koji se dalje može koristiti za razne svrhe.
U ovom radu je opisan postupak obrade otpadnih voda te pojedine faze pročišćavanja u kojima nastaju muljevi. Nastali muljevi mogu sadržavati različite opasne tvari (teške metale, patogene mikroorganizme) što ga može svrstati u opasan otpad te je zbog toga potrebna njegova prethodna obrada. Metode obrade mulja su kondicioniranje, zgušnjavanje, stabilizacija, odvodnja, toplinska obrada, kompostiranje i anaerobna digestija. Iskorištavanje mulja nakon obrade će ovisiti o njegovom fizikalnom i kemijskom sastavu te je stoga vrlo važno pratiti kakvoću mulja. Ovisno o svojstvima mulj se može koristiti u energetske svrhe, poljoprivredi, građevini te na razne druge načine ili se mora zbrinuti na odgovarajući način.The role of waste water treatment plant has been significant since the very beginnings of civilization. As a negative product of water treatment is sludge, and its composition depends largely on the type of water being treated. By appropriate sludge processing and removal of all hazardous factors, what can be very expensive, sludge can be used for various purposes.
This paper describes the process of waste water treatment and some purification stages in which sludge is produced. The sludge produced may contain various dangerous substances (heavy metals, pathogenic microorganisms) which classify the sludge as a hazardous waste and therefore requires prior treatment. Sludge treatment methods include conditioning, condensation, stabilization, drainage, heat treatment, composting and anaerobic digestion. Usage of sludge after processing will depend on its physical and chemical composition and therefore it is very important to monitor the quality of the sludge. Depending on the properties, sludge can be used for energy purposes, agriculture, construction, etc. or it must be handled appropriately
Sulfur compounds in metallurgical coke
Get PDFMetalurški koks ima važnu ulogu u metalurgiji gdje se koristi kao gorivo, redukcijsko sredstvo i sredstvo za naugljičenje. U novije vrijeme je također važna sirovina za proizvodnju vrijednijih ugljičnih materijala. Metalurški koks je umjetno gorivo koje se dobiva iz ugljena kao prirodnog goriva postupkom koksiranja.
Spojevi sumpora su jedni od glavnih nepoželjnih sastojaka ugljena i metalurškog koksa,pridonose onečišćenju okoliša i poteškoćama pri njihovoj uporabi.
U ovom radu je dan pregled relevantne literature koja se odnosi na povezanost spojeva sumpora u ugljenu za koksiranje i metalurškom koksu, reakcijama spojeva sumpora tijekom procesa koksiranja, postupcima odsumporavanja i interakciji spojeva sumpora i okoliša s obzirom na to da su spojevi sumpora važni čimbenici onečišćenja okoliša i klimatskih promjena.Metallurgical coke plays an important role in metallurgy where it is used as a fuel, a reducing agent and a carburizer. Recently, it is also an important raw material for the production of more valuable carbon materials. Metallurgical coke is an artificial fuel obtained from coal as a natural fuel by the coking process.
Sulfur compounds are one of the major undesirable components of coal and metallurgical coke,contribute to environmental pollution and difficulties in their use.
This paper presents a review of relevant literature related to the connection of sulfur compounds to coking coal and metallurgical coke, sulfur compounds reactions during the coking process, desulphurization process andinteractions between sulfur compounds and the environment where are sulfur compounds are important factors of environmental pollution and climate change
Thermal characteristics of enamels and enamelled metal sheets
Get PDFThe main task of the research was to find out why sometimes cracking of the enamelled layer occur and to what extent enamel layer affects the heat transfer in the cooking oven. The samples of the enamelled streel sheet were metallographically analysed by scanning electron microscopy (SEM-EDX) and optical microscopy (OM). Measurements of the thermal properties of two types of enamels, which are used for oven interior enamelling was carried out in accordance with the standard ISO 22007-2 by transient planar heat source method (TPS Hot Disk 2200). To ensure proper measurement conditions, the samples of the enamels were prepared in the form of thick layers. The results show that enamel density has significant influence on its thermal properties. An assessment of the influence of the thermal conductivity of the enamel layer on the heat transfer in the oven is also given