Repository of Faculty of Metallurgy University of Zagreb
Not a member yet
491 research outputs found
Sort by
The influence of forging and heat treatment on microstructure and hardness of CuAlMn shape memory alloy
No full textCuAlMn legure s prisjetljivosti oblika značajne su prvenstveno zbog primjene u elektroindustriji. U diplomskom radu istraživan je utjecaj kovanja i toplinske obrade na mikrostrukturu CuAlMn legure s prisjetljivosti oblika koja je dobivena postupkom lijevanja u grafitnu kokilu te kovanjem u šipke promjera 6,5 mm i 13 mm. Nakon kovanja, dobivene šipke toplinski su obrađene pri temperaturi od 850 ˚C, u trajanju od 30 minuta, a potom hlađene u vodi sobne temperature. Mikrostrukturna karakterizacija uzoraka prije i nakon toplinske obrade provedena je svjetlosnom mikroskopijom (LM) i pretražnom elektronskom mikroskopijom (SEM). Analizom mikrostrukture kod kovanih uzoraka primijećena je dvofazna (α+β) mikrostruktura, dok je na uzorcima koji su toplinski obrađeni vidljiva martenzitna mikrostruktura. Tvrdoća uzoraka se smanjuje kod toplinski obrađenih uzoraka u odnosu na kovane uzorke.CuAlMn shape memory alloys are significant primarily due to their application in the electrical industry. In this paper, the investigation of influence of forging and heat treatment on microstructure of CuAlMn shape memory alloy. The alloy was obtained by casting in a graphite mold, and then forged into bars with a diameter of 6.5 mm and 13 mm. After forging, the obtained bars were heat treated at 850 ˚C for 30 minutes and then cooled in room temperature water. Microstructural characterization of the samples before and after heat treatment was performed by light microscopy (LM) and scanning electronic microscopy (SEM). Analyzing the microstructure of the forged samples a two-phase (α+β) microstructure was revealed, while the heat-treated samples showed a martensitic microstructure. The hardness decreases in heattreated samples in comparison to forged samples
Synthesis and characterization of modified hard metal
No full textTvrdi metali su komercijalno najstariji i najpoznatiji predstavnici materijala proizvedenih metalurgijom praha. Posjeduju izvrsna svojstva prikladan za brojne industrijske primjene.
Tvrdi metal je kompozitni materijal sastavljen od dvije glavne faze: volframovog karbida i veziva. U ovom diplomskom radu klasičnim postupcima metalurgije praha je proizveden modificirani tvrdi metal s 10 % nikla kao veziva (WC-10Ni) s ciljem dobivanja nemagnetičnog materijala koji će se moći koristiti za izradu alata za prešanje prahova u procesu proizvodnje magneta tehnologijom metalurgije praha. Korištene su tri temperature sinteriranja kako bi se utvrdile ovisnosti i povezanosti mikrostrukture i svojstava s procesnim parametrima.
Utvrđeno je da cilj, u smislu proizvodnje nemagnetičnog materijala, nije postignut, ali su dobiveni vrlo vrijedni rezultati vrlo bliski očekivanim. Daljnjim istraživanjima potrebno je ustanoviti dodatne informacije kako bi se optimirali procesni parametri koji će rezultirati proizvodnjom nemagnetičnog tvrdog metala s niklom kao alternativnim vezivom.Hard metals are commercially the oldest and the best known representatives of materials produced by powder metallurgy. They possess excellent properties that are suitable for numerous industrial applications.
Hard metal is a composite material consisting of two major phases: tungsten carbide and binder. In this master’s thesis modified hard metal with 10 % of nickel as binder (WC-10Ni) was produced by classic powder metallurgy. The goal was to obtain a nonmagnetic material that would be suitable as powder pressing tool in the production of magnets by powder metallurgy. Three different temperatures of sintering were used with purpose to determine a dependence and correlation of microstructure and properties with processing parameters.
It was established that main goal, in the context of nonmagnetic material production, was not obtained. Nevertheless, very valuable results were accomplished that are very close to the desired. Further investigations are needed to establish additionally information that could be used for an optimization of processing parameters that would be result in the production of nonmagnetic hard metal with nickel as alternative binder
Utjecaj temperature popuštanja na mikrostrukturu i tvrdoću CuAlNi legure s prisjetljivosti oblika
No full textU ovom radu prikazan je utjecaj temperature popuštanja na mikrostrukturu i tvrdoću CuAlNi legure s prisjetljivosti oblika. Legura kemijskog sastava Cu – 12,8 Al – 4,1 Ni (mas. %) je dobivena iz tehnički čistih elemenata postupkom vertikalnog kontinuiranog lijevanja. Nakon lijevanja, dobivena šipka CuAlNi promjera 8 mm, podvrgnuta je postupku toplinske obrade koji se sastojao od kaljenja na 920 °C ' hlađenje u vodi te popuštanja na 15 °C, 200 °C, 250 °C i 300 °C '/ hlađenje u vodi. Utjecaj temperature popuštanja na mikrostrukturu CuAlNi legure utvrđen je svjetlosnom i pretražnom elektronskom mikroskopijom. Utvrđena je martenzitna mikrostruktura kod svih ispitanih uzoraka te značajni porast zrna, posebice nakon popuštanja. Tvrdoća po Vickersu pokazuje značajno povećanje tvrdoće uzorka nakon popuštanja u odnosu na kaljeno stanje.In this paper, the influence of tempering temperature on the microstructure and hardness of CuAlNi alloy with shape memory effect is presented. Alloy with chemical composition Cu – 12.8 Al – 4.1 Ni (wt. %) was obtained from technically pure elements by the process of vertical continuous casting. After casting, the resulting CuAlNi bar with a diameter of 8 mm was subjected to a heat treatment procedure consisting of solution annealing at 920 °C / cooling in water and tempering at 150 °C, 200 °C, 250 °C and 300 °C '/ cooling in water. The influence of the tempering temperature on the microstructure of the CuAlNi alloy was determined by light and scanning electron microscopy. A martensitic microstructure was found in all tested samples and a significant grain growth was noticed, especially after tempering. The Vickers hardness shows a significant increase in the hardness of the sample after tempering compared to the annealed state
Assessment of risks at work in a facility for the production of animal feed
No full textU proizvodnji stočne hrane prisutni su brojni izvori unutarnjih opasnosti od fizikalnih, bioloških, kemijskih, mehaničkih, od padova, električne struje te fizičkog i psihičkog napora od dugotrajnog ponavljanja istih radnji. Istraživanje provedeno u ovom radu dati će prikaz izvora unutarnjih opasnosti u proizvodnji stočne hrane u poduzeću Agrocroatia Nova d.o.o. Opisan je tehnološki proces rada, prisutni rizici, način procjene i postupak tretmana rizika. Za upravljanje rizicima koji su prisutni u poslovanju poduzeće Agrocroatia Nova d.o.o. primjenjuje postupak smanjivanja rizika primjenom mjera, pravila i postupaka zaštite na radu. Mjere, postupke i pravila za upravljanje rizicima poduzeće je definiralo u svom vlastitom pravilniku, koji sadrži opće upute za rad na siguran način s opasnim tvarima i upute za rad na siguran način sa strojevima za rad.In the production of animal feed, there are numerous sources of internal dangers from physical, biological, chemical, mechanical, falls, electric current, and physical and mental strain from long-term repetition of the same actions. The research conducted in this paper will provide an overview of the sources of internal hazards in the production of animal feed in company Agrocroatia Nova d.o.o. The technological work process, the risk presence, the assessment method and the risk treatment procedure are described. To manage the risks that are present in the business, company Agrocroatia Nova d.o.o. applies the risk reduction procedure by applying safety at work measures, rules and procedures. Measures, procedures and rules for risk management are defined by the company in its own rulebook, which contains general instructions for working safely with dangerous substances and instructions for working safely with work machines
Establishing a quality system in the company for vehicle service and sales
No full textUpravljanje kvalitetom i ostvarivanje navedenih ciljeva nije lak zadatak, ali svaka tvrtka si ga mora postaviti i težiti njegovom ostvarenju. Tržišna konkurencija je jaka i svaka tvrtka da bi bila konkurentna mora kontinuirano poboljšavati svoj radni proces, a to se postiže dobro postavljenim sustavom kontrole koji su vezani za kvalitetu rada.
Kvaliteta nam je pokazatelj vrijednosti neke robe ili usluge s ciljem zadovoljavanja potreba potrošača i proizvođača koji na kvalitetu gledaju u različitim smjerovima, zato je vrlo bitno da se usklade potrebe i jednih i drugih. Kroz sustave upravljanja kvalitetom postiže se balans između proizvođača, pružatelja usluga i krajnjih potrošača. Da bi sustav funkcionirao trebaju se zadovoljiti određeni uvjeti pri uvođenju sustava kvalitete i održavanja istog, tu nam uveliko pomažu norme kroz koje se implementiraju sustavi upravljanja kvalitetom.
Cilj rada je objasniti kako se uspješno vodi sustav kvalitete u tvrtki za servis i prodaju vozila.Quality management and achieving the stated goals is not an easy task, but every company must set it and strive for its realization. Market competition is strong and every company in order to be competitive must continuously improve its work process, and this is achieved by a well-placed control system related to the quality of work.
For us, quality is an indicator of the value of a product or service with the aim of meeting the needs of consumers and producers who look at quality in different directions, so it is very important to harmonize the needs of both. Through the quality management system, a balance is achieved between producers, service providers and end consumers. In order for the system to function, it should meet certain conditions during the introduction of the quality system and its maintenance, the norms through which the quality management systems are implemented help us a lot.
The aim of the paper is to explain how the quality system is successfully managed in companies for the service and sale of vehicles
Nanostructured hard metals with FeNi binder and cubic crystals addition
No full textsu najvažniji predstavnici metalurgije praha. To su kompozitni materijali u kojima su čestice tvrde karbidne faze međusobno povezane metalnim vezivom, a koji najveću primjenu nalaze u industriji alata. Kako bi im se poboljšala svojstva, u zadnje vrijeme se proizvode iz ultrafinih nano čestica praha. Struktura dobivena sinteriranjem praha nanočestica osigurava značajno poboljšanje svojstava proizvoda, kao što su: veće brzine rezanja, manje tolerancije alata i duži vijek trajanja.
Cilj ovog rada bio je primjenom nano praha volframovog karbida postići homogenu sitnozrnatu mikrostrukturu koja će rezultirati visokim i ujednačenim vrijednostima tvrdoće po ispitnoj površini. Stoga je proizveden nanostrukturirani tvrdi metal WC-FeNi s dodatkom kubičnih karbida tehnologijom metalurgije praha točnije HIP postupkom, čija je sinterirana gustoća jednaka teorijskoj gustoći. Na poliranoj površini svjetlosnim mikroskopom nisu uočeni defekti, dok je pretražnom elektronskom mikroskopijom s emisijom polja uočen vrlo mali broj manjih pora. Tvrdoća proizvedenog nano tvrdog metala je izrazito visoka te ujednačena po ispitnoj površini, što je rezultat homogene mikrostrukture kao i dodatka inhibitora rasta zrna u obliku kubičnih karbida.Hard metals are the most important representatives of powder metallurgy. They are composite materials in which particles of carbide phase are bonded by metal binder. A major application of this materials are in the tool industry. Recently, to improve the properties, they are produced from ultrafine nano powders. Structure obtained by sintering of nano powders provides much improvement of product properties, such as: higher cutting rates, lower tolerances of tools as well as longer service life.
The goal of this work was to obtain the homogenous finegrain microstructure that will result in high and uniform hardness values using the nano powders of tungsten carbide. For this purpose, nanostructured hard metals WC-FeNi with cubic crystals addition was produced by powder metallurgy, i.e. by HIP. Sintered density of produced material is identical to the theoretical density. No defects were detected on the polished surface by light microscopy, while a very small number of smaller pores were detected by scanning electron microscopy with field emission. The hardness of the produced nano-hard metal is extremely high and uniform over the test surface, which is the result of homogeneous microstructure as well as the addition of grain growth inhibitors in the form of cubic carbides
Traditional quality improvement tools in foundries
No full textOsiguranje kvalitete ima veliku važnost kako bi se osigurala jednaka kvaliteta proizvoda u cijelome svijetu. Za unaprijeđivanje i održavanje trenutne kvalitete određenog proizvoda ili procesa često se koristi sedam tradicionalnih alata za upravljanje kvalitetom. U ljevačkoj industriji vrlo često se tradicionalni alati za upravljanje kvalitetom koriste kako bi se konstantno unaprijeđivali i poboljšavali postojeći procesi ili proizvodi loše kvalitete tijekom proizvodnje. U ovom završnom radu opisana je primjena sedam tradicionalnih alata za upravljanje kvalitetom u ljevaonicama. Pregled korištenja tradicionalnih alata za upravljanje kvalitetom prikazan je na problemima koji se javljaju u industriji lijevanja različitih metalnih proizvoda i odljevaka. Na primjerima pojave problema u procesima i raznih grešaka na proizvodima lijevanja objašnjena je važnost korištenja tradicionalnih alata za upravljanje kvalitetom u ljevaonicama.Quality assurance has a great importance because it assures equal quality of products all over the world. Improvement and maintenance of product and process quality are usually achieved by using seven traditional quality management tools. Traditional quality management tools are very often used in the foundries to continually improve current processes and to analyze non-compliant products during production. The application of traditional quality management tools in foundries is described and explained in this paper. Further, there is a review of tools used to solve issues that occur during the production of different metal castings. The importance of the implementation of traditional quality management tools in foundries is explained through the examples of process issues and product failures
Stress distribution at different deformation degrees in low carbon steel during cold deformation
No full textThe temperature change, i.e. stresses of low carbon steel during the cold deformation process was investigated in this study. During static tensile test, temperature changes were examined using thermography at different deformation degrees. It was found that there are temperature changes in the deformation zone during the cold deformation. The increase in temperature changes in the deformation zone during cold deformation occurs with an increase in the deformation degree. The largest localization of temperature change was measured at the moment of the test sample fracture when the maximum temperature change was 8.45 °C. A higher amount of temperature change of 5.39 °C was determined at tensile strength compared to the proportionality limit amount of -0.97 °C. It was found that there are differences between the amounts of temperature changes in the range from 0.87 °C to 1.91 °C with increasing of deformation degree of the tested steel. Calculated stress amounts proved and show the tendency that stress amounts increase as the temperature change increases in low carbon steel by increasing of deformation degree during cold deformation. It was determined deviations of the calculated stress amounts due to using the mathematical model for low carbon with niobium at the start of plastic flow
60. godina studijskih programa Metalurškog fakulteta Sveučilišta u Zagrebu - I. 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 Osvrta prikazan povijesni razvoj nastavne djelatnosti iz polja Metalurgija, počevši od 1919. godine. Uvođenjem metalurških predmeta kroz različite odsjeke i odjele Tehničke visoke škole stvoreni su preduvjeti za osnivanje Odjela za metalurgiju i rudarstvo te kasnije osamostaljivanje Odjela za metalurgiju u Sisku u okviru Tehnološkog fakulteta u Zagrebu 1960. godine. S tom godinom započinje samostalno izvođenje studijskog programa iz polja Metalurgija. Opremanjem i razvojem studijskih programa te organizacijskim reformama Odjel prerasta u Metalurški fakultet Sveučilišta u Zagrebu
Bakar
No full textOpisan je bakar i bakrene legure s njihovim svojstvima, prve upotrebe i dobivanje bakra u svijetu, počeci i dobivanje bakra u Hrvatskoj