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Utjecaj debljine stjenke na razvoj mikrostrukture i mehanička svojstva visokotlačno lijevane AlSi12 legure
No full textZahvaljujući oblikovljivosti i jednostavnosti procesa proizvodnje, odličnim mehaničkim svojstvima i kombiniranju s drugim metalima, aluminijske legure pronalaze široku primjenu u svim industrijskim granama. Radi poboljšanja mehaničkih, fizikalnih i korozijskih svojstva aluminijskih legura dodaju se legirajući elementi poput silicija, magnezija ili bakra te elementi u tragovima poput željeza, mangana, bora, titana, stroncija ili natrija. Njihov utjecaj doprinijet će ciljanom razvoju mikrostrukture koja će u konačnici poboljšati mehanička svojstva. Važnu ulogu ima i odabir tehnologije lijevanja, te parametri lijevanja koji će utjecati na brzine hlađenja i/ili skrućivanja te pritom činiti osnovu razvoja mikrostrukture i konačnu upotrebnu vrijednost odljevaka.
U teorijskom dijelu rada opisana su svojstva i upotreba aluminija i njegovih legura, utjecaj kemijskih elemenata i brzine hlađenja na mehanička svojstva i mikrostrukturu. Također je pojašnjen proces skrućivanja Al legura.
Eksperimentalni dio rada proveden je u suradnji s ljevaonicom Lipovica d.o.o. Cilj provedenog istraživanja bio je procijeniti utjecaj debljine stijenke na mikrostrukturu i mehanička svojstva AlSi12 legure. Na uzorcima različitih debljina stijenki napravljena je analiza kemijskog sastava, analiza mikrostrukture, statički vlačni pokus i mjerenje tvrdoće. Istraživanjem je utvrđeno kako debljina stijenke ima utjecaj na mikrostrukturu i mehanička svojstva AlSi12 legure.Due to formability and simplicity of production process, excellent mechanical properties and combination with other metals, aluminum alloys are widely used in all industries. Alloying elements such as silicon, magnesium or copper and trace elements such as iron, manganese, boron, titanium, strontium or sodium are added to improve the mechanical, physical and corrosion properties of aluminum alloys. Their impact will contribute to the targeted development of microstructures that will ultimately improve the mechanical properties. An important role plays the choice of casting technology, casting parameters that will affect the cooling and / or solidification rates, and therefore the development of the microstructure and the final application value of the castings.
The theoretical part describes the properties and use of aluminum and its alloys, the influence of chemical composition and cooling rate on mechanical properties and microstructure. The solidification process of Al alloys is also clarified.
In the experimental part of the work, an experiment was conducted in the foundry Lipovica d.o.o. For the experiment, we used an AlSi12 alloy cast by a high-pressure casting process. The aim of the study was to evaluate the influence of wall thickness on the microstructure and mechanical properties of AlSi12 alloy. Chemical composition analysis, microstructure analysis, static tensile test and hardness measurement were performed on samples with different wall thicknesses. The research established that the wall thickness has an impact on the microstructure and mechanical properties of AlSi12 alloy
Aging of photocatalysis based on titanium (IV) oxide and graphene oxide
No full textZbog sve većeg porasta broja stanovništva i potrebe za industrijalizacijom radi što lagodnijeg života prouzrokovano konzumerizmom, razna industrijska postrojenja i tvrtke otpad ispuštaju u okoliš. Uporabom pesticida, farmaceutika, plastike, kao i ostalih onečišćujućih tvari koje nisu biorazgradive, narušavamo prirodni balans ujedno uništavajući okoliš u kojem živimo. Potrebno je pronaći što učinkovitiji način uklanjanja mikroonečišćivača. Jedni od modernijih načina uklanjanja mikroonečišćivača jesu napredni oksidacijski procesi, konkretno u ovom slučaju fotokataliza.
U ovom radu provedena je fotokataliza, kao metoda za uklanjanje salicilne kiseline iz vode. Fotokataliza je proces u kojemu pomoću UV zračenja i fotokatalizatora, nastaju hidroksilni radikali koji sudjeluju u razgradnji organskih mirkoonečišćujućih tvari. U svrhu poboljšanja fotokatalitičkih svojstava TiO2 dodan je grafen oksid. Radi usporedbe učinka grafen oksida na fotokatalitička svojstva, pripremljene su dvije vrste mrežica. Prva mrežica sadržava fotokatalizator TiO2, a druga TiO2 u kombinaciji sa grafen oksidom. Ispitivana su fotokatalitička svojstva prije starenja i nakon 6 mjeseci starenja u vodi i na zraku. Iz rezultata ispitivanja vidljivo je da se fotokatalizatori starenjem „troše“, odnosno smanjuje im se fotokatalitička sposobnost razgradnje salicilne kiseline u vodi. Iz dobivenih rezultata vidljivo je da je bolji fotokatalizator čisti TiO2.Due to the growing population and the need for industrialization for more comfortable life caused by consumerism, various industrial plants and companies release waste into the environment. By using pesticides, pharmaceuticals, plastics, as well as other pollutants that are not biodegradable, we disturb the natural balance while destroying the environment we live. It is necessary to find the most effective way to remove micro-pollutants. One of the more modern ways of removing micro-pollutants are advanced oxidation processes, specifically in this case photocatalysis.
In this paper, photocatalysis was performed as a method for removing salicylic acid from water. Photocatalysis is a process in which, using UV radiation and photocatalysts, hydroxyl radicals are formed that participate in the decomposition of organic micro-pollutants. Graphene oxide was added to improve the photocatalytic properties of TiO2. To compare the effect of graphene oxide on photocatalytic properties, two types of glass fiber meshes were prepared. The first mesh contains the photocatalyst TiO2, and the second TiO2 in combination with graphene oxide. Photocatalytic properties before aging and after 6 months of aging in water and air were studied. The test results show that photocatalysts "wear out" with aging, ie their photocatalytic ability to decompose salicylic acid in water decreases. The obtained results show that the better photocatalyst is pure TiO2
Effect of processing parameters on the microstructural characteristics of sintered dental titanium-zirconium alloy
No full textTitan i legure titana pokazuju jedinstvenu kombinaciju čvrstoće i biokompatibilnosti, što omogućuje njihovu upotrebu u medicini i objašnjava njihovu široku upotrebu kao implantacijski materijali u posljednjih 50 godina. Jedna od prednosti titana je sposobnost vezivanja za kost i urastanje u implantat dok zacjeljuje. Materijal je također poznat po svojoj trajnosti tako da implantat može trajati godinama - ili čak trajno. S obzirom da titan ima visoku cijenu razvijaju se i koriste nove ekonomičnije legure.
Stoga je u okviru ovog rada cilj metalurgijom praha proizvesti leguru titana s dodatkom 20 at.% cirkonija za dentalnu primjenu. Pri tome će se odgovarajućim metodama analizirati utjecaj procesnih parametara (tlaka kompaktiranja, temperature i vremena sinteriranja) na mikrostrukturne značajke sinterirane legure.
Iz dobivenih rezultata se može vidjeti da se primjenom metalurgije praha može proizvesti titan - cirkonij legura sa svojstvima povoljnima za dentalnu medicinu, s time da bi se veća pažnja trebala obratiti na vrijeme miješanja polaznih prahova.Titaniumandtitaniumalloys show a uniquecombinationofstrengthandbiocompatibility, whichallowstheir use in medicine andexplainstheir wide use as implantmaterialsinthelast 50 years. One oftheadvantagesoftitaniumisitsability to bind to bone andgrowintotheimplant as itheals. Thematerialisalsoknown for itsdurabilitysotheimplantcanlast for years - orevenpermanently. Sincetitaniumhas a highprice, new, more economicalalloys are beingdevelopedandused.
Therefore, theaimofthisworkis to producetitaniumalloywiththeadditionof 20 at.% zirconium for dental use bypowdermetallurgy. The influence ofprocessparameters (compactionpressure, temperature andsintering time) on themicrostructuralcharacteristicsofthesinteredalloywillbeanalyzedbyappropriatemethods.
Fromtheobtainedresultsitcanbeseenthattheapplicationofpowdermetallurgycanproducetitanium - zirconiumalloyswithpropertiesfavorable for dental medicine, with more attentionshouldbepaid to the time ofmixingthestartingpowders
Application of thermography in determining the proportionality limit
No full textThe determination of the proportionality limit was performed to determine the beginning of the plastic flow of steel during cold deformation as accurately as possible. Measurements were performed by static tensile tests using an extensometer and a thermographic camera. The research has shown that with thermography is possible to determine the beginning of the plastic flow of material with high accuracy
Cold drawing of steel tubes
No full textPrecizno hladno deformirane cijevi proizvode se hladnim izvlačenjem i hladnim pilgerovanjem. Hladno izvlačenje cijevi provodi se na vučnoj klupi, gdje se kroz matricu određenih dimenzija izvlači cijev s većeg promjera na manji. Kako bi se dobila tražena debljina stijenke cijevi i promjera potrebno je prije sljedećeg izvlačenja provesti žarenje. U ovom radu prikazani su rezultati hladnog izvlačenja cijevi. Istraživanja su provedena na čeliku E355. Cijev promjera 30 mm i debljine stijenke 3 mm vučena je na konačnu dimenziju promjera 20 mm i debljine stijenke cijevi 2 mm. Nakon izvlačenja cijevi su ispitivane statičkim vlačnim pokusom i mjerenjem tvrdoće metode po Vickersu. Detaljno je ispitana promjena tvrdoće u zoni deformacije i određen stupanj očvršćivanja tijekom hladne deformacije. Strukturna ispitivanja provedena su na skenirajućem elektronskom mikroskopu (SEM).Precision cold-drawn tubes are produced by cold drawing and cold pilgering. The cold drawing of the tubes is carried out at the draw bench, where the diameter of the tube from a larger diameter to the smaller is drawn through the die of certain dimensions. In order to obtain the required thickness of the tube wall and diameter, it is necessary to carry out the annealing before the next draw. This paper presents the results of cold drawn tubes. Research was carried out on steel E355. The tube diameter of 30 mm and wall thickness of 3 mm is drawn to the final dimension of 20 mm diameter and wall thickness of 2 mm. Metallographic tests on optical microscope, static tensile tests and Vickers hardness tests were used for testing tubes after cold drawing. The hardness change in the deformation zone and the degree of hardening during cold deformation in one draw were examined in detail. Structural testing was performed on a scanning electron microscope (SEM)
Characterization of Duplex Stainless Steel after Welding and Annealing
No full textDupleks nehrđajući čelici se nazivaju još i austenitno-feritni nehrđajući čelici te svoje ime duguju miješanoj strukturi austenita i ferita pri sobnoj temperaturi. Osnova dupleks nehrđajućih čelika je Fe-Cr-Ni-N sustav, a glavne faze su austenit (γ) i ferit (α). Glavna prednost dupleks nehrđajućih čelika je dobra korozijska otpornost. Oni uglavnom sadrže viši sadržaj kroma te niži sadržaj nikla, a često sadrže i molibden radi povećanja otpornosti na koroziju. U ovom radu provedena je mikrostrukturna analiza i ispitivanje mikrotvrdoće zavarenog dupleks nehrđajućeg čelika X2CrNiMoN22-5-3. Uzorci su zavareni tako da je korijen zavara zavaren TIG postupkom, a za popunu zavara korišten je REL postupak zavarivanja. Analiza mikrostrukture i mikrotvrdoće je provedena prije i nakon žarenja (850 °C/60min/zrak). Uzorci su nakon žarenja metalografski pripremljeni. Optička mikroskopija i pretražna elektronska mikroskopija s energetsko disperzijskom spektrometrijom su korištene za mikrostrukturnu karakterizaciju. Prije žarenja mikrostruktura se sastojala od ferita i austenita, a nakon žarenja je utvrđena prisutnost sigma faze u zoni taljenja. Mikrotvrdoća uzoraka prije i nakon žarenja mjerena je metodom po Vickersu. Nakon žarenja zamijećen je najveći porast mikrotvrdoće u zoni taljenja (s 294,9 HV1 na 357,0 HV1).Duplex stainless steelsalso called austenitic-ferritic stainless steels, owe their name to the mixed austenite and ferrite structure at room temperature. Basis of duplex stainless steels is Fe-Cr-Ni-N system, whereas austenite (γ) and ferrite (α) are main phases. Main adventage of duplex stainless steel is very good corrosion resistance. They usually contain higher content of chromium, lower content of nickel and often contain molybdenum to increase corrosion resistance. In this paper microstructure analysis and microhardness testing was carried out on welded duplex stainless steel X2CrNiMoN22-5-3. Samples were welded so that the root of weld was welded with TIG process, and for filling REL process was used. Analysis of microstructure and microhardness was conducted before and after annealing (850 °C/ 60 min/ air). Afterannealing,the samples were metallographically prepared. Optical microscopy and scanning electron microscopy with energy dispersion spectrometer were used for microstructural charaterization. Before annealing microstructure was consisted of ferrite and austenite, and after annealing presence of sigma phase was determined in melting zone.Microhardness of samples before and after heat treatment was measured by Vickers method. After annealing it is noticed the highest increase in microhardness in melting zone (from 294,9 HV1 to 357,0 HV1)
Market of Titanium and its Alloys
No full textU ovom radu dan je opći prikaz titana i njegovih legura, a detaljnije je prikazano njihovo tržište sa naglaskom na određene proizvode i njihovu najširu primjenu, njihovo trenutno stanje, odnose cijena te njihov potencijal u budućnosti. Također, sukladno situaciji kakva je trenutno u svijetu, u ovom radu govori se o tržištu titana u doba Covid-19 virusa te promjene u trendovima uporabe titana i cijene istog u zadnjih 20 godina.This paper gives a general overview of titanium and its alloys, and presents their market in more detail with an emphasis on certain products and their widest application, their current state, price relations and their potential in the future. Also, in accordance with current situation in the world, this paper discusses the titanium market in the era od Covid-19 virus and changes in trends in the use of titanium and its price in the last 20 years
Structural changes during copper wire drawing
No full textBakar je materijal koji je poznat od davnina po svojim poželjnim svojstvima kao što su dobra toplinska i električna vodljivost, visoka tvrdoća, pristupačna cijena itd. Možemo reći kako svakodnevnica koju poznajemo ne bi bila ista bez bakra jer je kao vodič, sastavni dio elektroničkih komponenti. Bakrena žica dobiva se izvlačenjem. Izvlačenje je postupak koji je karakterističan po tome što tijekom obrade metala ne dolazi do razaranja, odnosno skidanja čestica kako bi se dobio konačan oblik. Pri proizvodnji bakrene žice najzastupljeniji je postupak provlačenja kroz matrice gdje dolazi do smanjenja poprečnog presjeka uslijed provođenja samog procesa na način da se žica provlači kroz jednu ili više matrica. Rezultat su poboljšana mehanička svojstva, kao što je tvrdoća te promjena u strukturi materijala. U ovom radu istražena su upravo ova dva čimbenika, a naglasak je stavljen na promjenu u strukturi. Bakrena žica koja je proizvedena UPCAST postupkom, naknadno je provlačena na vučnoj klupi gdje se reducirao njezin poprečni presjek. U svakoj fazi prerade uzimani su uzorci kako bi se pratila promjena u strukturi i tvrdoći žice. Uzorci su prošli metalografsku pripremu pri kojoj je došlo do isticanja mikrostrukture te je potom provedena analiza mikrostrukture pomoću metalografskog mikroskopa te u konačnici ispitivanje tvrdoće. Dobiveni rezultati istraživanja su pokazali i dokazali promjenu u mikrostrukturi lijevane žice, u smislu usmjerenije strukture sa sitnijim zrnima te je došlo do porasta tvrdoće materijala.Copper is a material which is known since ancient times by its desirable properties such as thermal and electrical conductivity, high material hardness, approachable price etc. We may say that everyday life which is known to us would not be the same without copper, because as a conductor is the main part of the electrical components. Copper wire is obtained by drawing. Drawing is a process that is characterized by the fact that during the processing of the metal there is no destruction or removal of particles to obtain the final shape. In the production of copper wire the most common is the process of drawing through the dies where there is a reduction in cross section due to the implementation of the process itself in such way that the wire is drawn through one or more dies. The result is improvedmechanical properties, such as hardness and changes in material structure. In thispaperthesetwofactors are explored and the emphasis is givenon the change in structure. The copper wire that hadbeenpreviouslyproduced bythe UPCAST process, was drawn on a drawing table where its cross section wasreduced. Samplesweretaken at eachstage of processing, in order to monitor the changes in structure and hardness of wire. The samplesunderwentmetallographicpreparation where the microstructurefeaturedand then the microstructureanalysiswasperformedusing a metallographicmicroscope and finally the hardness testwasperformed. The obtained researchresultsshowed and proved a change in the microstructure of the cast wire, in terms of more directedstructurewithfinergrains, while the increase in hardness is more pronounced
Influence of medium on corrosion and microstructural properties of K110 tool steel for cold work
No full textThis paper presents the results of testing the corrosion behaviour of K110 tool steel for cold work in industrial emulsion medium (Lenox Band- Ade semi-synthetic oil + water, in a ratio of 1:10), water and 3.5% NaCl medium. Using the method of electrochemical impedance spectroscopy (EIS) and Tafel extrapolation, electrochemical measurements were performed in order to determine the corrosion parameters. After polarization measurements, the surface of the sample was examined with an optical microscope. Tafel extrapolation of the polarization curves revealed that the tested tool steel showed the lowest corrosion rate in the Lenox Band-Ade emulsion medium and the highest in the medium of 3.5% NaCl. The obtained results were confirmed by the method of electrochemical impedance spectroscopy, where the lowest charge transfer resistance was registered in the 3.5% NaCl medium, which indicates the fact that the thinnest oxide layer was formed in tested medium, which has a very weak protective role in the corrosion process. Metallographic analysis of the sample surface after polarization measurements in 3.5% NaCl medium indicates the occurrence of pitting corrosion caused by the action of aggressive chloride ions from the solution, which caused the destruction an already weak passive layer on the metal surface. At the same time, chloride ions from the acid medium attack more aggressively the matrix of the metal base of the tool steel, in contrast to the precipitated carbides on the sample surface
The Application of a Factorial Experiment with Repeated Measurements in the Investigation of Parameters Influencing the Properties of Niobium Microalloyed Cold Drawn Welded Steel Tubes
No full textIt has been observed that inhomogeneous deformations occur at the beginning of the plastic material flow during the cold drawing of welded tubes and after the proportionality limit Rp has been reached. Therefore, it is important to determine the most influential factor at the beginning of the plastic material flow. Tests were carried out on a welded joint and on the base material. The study was performed on two steels with different contents of the microalloying element niobium. Tubes were drawn with two different degrees of reduction. The factorial experiment consisting of three factors at two levels 2^3 with repeated measurements showed that the degree of reduction has the greatest influence on the proportionality limit