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Casting and characterisation of binary 50Cu-50Zr alloy
No full textU ovom radu istraživana je binarna 50Cu-50Zr legura koja je služila kao predlegura za daljnji
postupak mikrolegiranja CuAlMn legure s prisjetljivosti oblika s cirkonijem. Predlegura Cu-Zr
dobivena je postupkom taljenja čistih metala u elektrolučnoj peći i lijevanja u cilindrične kalupe
promjera 8 mm i duljine 12 mm. Termodinamički proračun faznog dijagrama proveden je
Thermo-Calc programom, na osnovi pripremljene baze termodinamičkih podataka prema
optimiziranim literaturnim podacima te je utvrđeno da pripremljena predlegura pri sastavu 50
% Cu i 50 % Zr ima temperaturu solidusa 851 °C što je povoljna vrijednost za daljnju primjenu.
Mikrostrukturna analiza pokazala je dvofaznu mikrostrukturu, što je i u korelaciji s dobivenim
termodinamičkim proračunom.In this work, the 50Cu-50Zr binary alloy was studied, which served as a master alloy for the
further process of microalloying the CuAlMn shape memory alloy with zirconium. The Cu-Zr
master alloy was obtained by melting pure metals in an electric arc furnace and casting into
cylindrical molds with a diameter of 8 mm and a length of 12 mm. The thermodynamic
calculation of the phase diagram was performed using the Thermo-Calc program based on a
prepared database of thermodynamic data according to optimized literature data, and it was
found that the produced master alloy with a composition of 50 % Cu and 50 % Zr has a solidus
temperature of 851 °C, which is a favorable value for further application. The microstructural
analysis revealed a two-phase microstructure, which correlates with the thermodynamic
calculations obtained
Numerical analysis of metallographic preparation effect on the hardness of titanium alloy
No full textTitanium alloys due to their good properties are increasingly used in biomedicine. However, in order to improve certain properties, titanium-based alloys with new chemical compositions are designed. In order to be characterized in a satisfactory manner, they must first be adequately prepared. In this paper the two most influential parameters were varied: grinding time and force, while the speed of rotation of the grinding wheel was constant. After grinding with the highest gradation of grind paper, the samples were observed under a light microscope to determine the condition of the surface. Then their hardness was determined by the Vickers method with different indenter loads. After that, the samples were polished under the same conditions, and their hardness was determined again. The obtained hardness values were numerically analyzed and the corresponding functional dependences of the measured hardness on the grinding parameters (time and force) and on the indentation force were determined
Changes in structure and properties of copper wire during the production and processing
No full textIrreplaceability of copper, as an electrical conductor, makes it the most important non-ferrous metal in application. The most frequently used methods of producing the copper conductors involves continuous casting of the copper wire, subsequent cold drawing deformation and heat treatment processes to improve copper mechanical and electrical properties. In this paper the research was performed on copper wire produced by continuous casting. During production various structural changes and changes in mechanical properties occur. To investigate those changes and to clarify their influence on final product, structure and hardness were recorded and measured in all stages of production. While macrostructure and microstructure were observed by light microscopy, the hardness was measured using Vickers hardness testing method. The results indicate that the initial coarse-grained structure in as-cast condition, brakes down into a fine- grained structure during reduction. Those fine grains are orientated in the direction of cold drawing during plastic deformation. There is an increase in the hardness. The purpose of heat treatment is to achieve better conductivity while maintaining good mechanical properties. The results of microstructure analysis indicate the presence of twin crystals in the structure of the final produc
Influence of corrosive media on elution of titanium alloy metal ions
No full textThe superior mechanical properties of titanium alloys have singled out this type of alloy as an essential material for various applications, especially in the field of biomedicine. Due to the growing demand for permanent implants, it has become necessary to accelerate the growing development research of biomaterials, and thus titanium alloys. In this research, influence of corrosive media on elution of titanium-chromium- niobium alloy of new chemical composition, Ti- 10Cr-10Nb, was investigated. It was produced by melting and casting in an electric arc furnace in argon atmosphere. The alloy was tested in three different media (saline, saliva and sweet carbonated beverage) at two temperatures (37 ˚C and 39 ˚C), in the same time interval. The polished surface of the samples was observed by a light microscope and Vickers hardness was measured as well. Conductivity and pH of corrosive media were measured before and after the elution. Concentrations of eluted metal ions were determined by inductively coupled plasma spectroscopy. The obtained results showed dependence of chromium ions elution on temperature as well as on type of corrosive media
Internal occupational safety supervision in the logistic distribution centre
No full textSukladno čl. 21. st. 4. Zakona o zaštiti na radu, unutarnji nadzor nad primjenom pravila zaštite na radu je jedan od najbitnijih poslova stručnjaka zaštite na radu. S obzirom na važnost unutarnjeg nadzora nad provedbom mjera zaštite na radu koji je jedan od osnovnih, a i najbitnijih poslova stručnjaka zaštite na radu zaposlenog u nekoj tvrtki, kroz završni rad opisat će se provođenje unutarnjeg nadzora zaštite na radu u logističko distributivnom centru sukladno mini vodiču za unutarnji nadzor Ministarstva rada i mirovinskog sustava uz osvrte autora na isti. Sigurno radno mjesto koristi svima, radniku i poslodavcu, kroz smanjenje broja nezgoda i ozljeda, manji su potencijalni troškovi, lakše se postižu zadani ciljevi i rokovi, a i veća je produktivnost i motiviranost radnika zbog sigurnog radnog mjesta.In accordance with Art. 21, paragraph 4 of the Occupational Safety and Health Act, internal supervision over the application of occupational safety rules is one of the most important duties of an occupational safety specialist. Considering the importance of internal supervision over the implementation of occupational safety measures, which is one of the basic and most important jobs of an occupational safety specialist employed in a company, the final paper will describe the implementation of internal occupational safety supervision in a logistics distribution center according to the mini guide for internal supervision of the Ministry of Labor and the Pension System with some of my comments on it. A safe workplace benefits everyone, the worker and the employer, through a reduction in the number of accidents and injuries, lower potential costs, easier achievement of set goals and deadlines, and greater worker productivity and motivation due to increased safety
Effect of hard metal production on the environment
No full textThis paper deals with production of hard metal by powder metallurgy and its effect on the environment. Hard metal is a composite material that consists of tungsten carbide as the hard refractory phase and cobalt or nickel as the soft metal binder phase. It cannot be produced by classical casting technology. Owing to its excellent properties, such as high hardness, wear and heat resistance etc., hard metal can be applied in a variety of industrial fields. Powder metallurgy is a technology for production of a wide range of materials as net-shape products from a compacted and sintered powders mixture. In this paper the impact of all stages of hard metal production by powder metallurgy on the environment is analysed. The presented analysis shows that production of hard metal by powder metallurgy has a minimum effect on the environment
Opasnosti i osnove razvoja požara u zatvorenom prostoru
No full textVatrogasni posao zahtijeva visoku fizičku i psihičku razinu pripremljenosti. Da bi se
intervencija odradila na najbolji način, potrebne su vještine, znanja, iskustva te svakodnevne
vježbe koje vatrogasci prolaze zajedno jer se tako uvježbavaju. U završnom radu opisani su
plameni udari koji se javljaju u požarima zatvorenih prostora. Poznavajući teoriju i s puno
uvježbavanja, vatrogasci uvijek moraju biti spremni za nadolazeće opasnosti koje su im
prijetnja za život. Zajedničkim prikupljanjem podataka i njihovom međusobnom razmjenom,
vatrogasna učinkovitost gašenja požara je veća. To je timski posao koji je potrebno što prije i
na najbolji način odraditi. Da bi se intervencije izvele na najbolji mogući način potrebno je
koristiti zaštitnu opremu koja je neizostavni dio vatrogasnih intervencija. U završnom je radu
detaljno opisana osobna zaštitna oprema koju svaki vatrogasac zadužuje prilikom stupanja u
radni odnos.The firefighting job requires a high level of physical and mental preparation. In order to
perform the intervention in the best way, knowledge, skills and experience are needed, as
well as daily exercises that firefighters go through together and thus train themselves. In the
final paper, the flame shocks that occur in closed space fires are described. Knowing the
theory and with a lot of training, firefighters must always be ready for upcoming dangers that
are a threat to their lives. By joint collection of data and mutual exchange of the same, fire
fighting efficiency is higher. It is a team work that needs to be done as soon as possible and in
the best way. In order to perform interventions in the best possible way, it is necessary to
adhere to protective equipment, which is an indispensable part of fire interventions. The final
paper describes in detail the personal protective equipment that every firefighter is required to
wear upon entering employment
Cleaner technologies for sustainable development
No full textAnthropogenic influence on global warming is now undeniably proven scientific fact. Ever-increasing efforts directed towards cleaner technologies are needed given the fact that COVID-19 caused disturbances in global supply chains, and a record increase in natural gas prices led to coal power production revitalization, nuclear renaissance and overall hampering of the energy transition. Cleaner technologies are becoming increasingly important on our path towards sustainable development. Present work builds on contributions from this special issue dedicated to the four Sustainable Development of Energy, Water and Environment Systems Conferences held in 2020 by emphasizing the role of cleaner technologies and detecting research trends. By dissecting recent examples of cleaner technologies in environmental systems, water systems and industrial processes, circular economy principles are obeyed through the application of cleaner technologies, where the material and energy loops are closed through cross-sectoral integration. Digitalization and advanced control concepts are expected to accelerate that integration under the smart paradigm. As technology for decarbonization is maturing and becoming increasingly compatible with the market, the focus is placed more on the social dimension of sustainability
Virtulab – Integrirani laboratorij za primarne i sekundarne sirovine
No full textCilj projekta Virtulab je poboljšati znanstveno-istraživačke i nastavne kapacitete pet sastavnica Sveučilišta u Zagrebu u sektoru primarnih i sekundarnih sirovina te dosegnuti europske i svjetske standarde praktične primjene znanja u gospodarstvu. Virtulab okuplja istraživačke kapacitete koji zadovoljavaju potrebe prospekcijskih istraživanja primarnih i sekundarnih sirovina, eksploatacije, oplemenjivanja, proizvodnih procesa, recikliranja i pronalaženja zamjenskih sirovina. Projekt doprinosi: 1) jačanju kvalitete znanstvenih istraživanja uvođenjem suvremene te povećanjem dostupnosti postojeće instrumentacije, 2) povećanju produktivnosti odnosno broja znanstveno-istraživačkih radova i broja prijava kompetitivnih znanstvenih i inovativnih projekata, 3) poboljšanju kvalitete nastave uz jačanje kompetencija studenata i time njihove konkurentnosti i zapošljivosti na tržištu rada i 4) transferu znanja i inovacija prema gospodarstvu. Implementacija projekta dugoročno će poboljšati dostupnost i iskorištenost primarnih i sekundarnih sirovina, pozitivno utjecati na okoliš i gospodarstvo i smanjniti uvoznu ovisnost Republike Hrvatske i Europske Unije u sektoru ne-energetskih mineralnih sirovina
The Effect of Heat Treatment on Damping Capacity and Mechanical Properties of CuAlNi Shape Memory Alloy
No full textThis paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60’/H2O and after tempering at 300 °C/60’/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (β1’ and γ1’) influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys’ mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists