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Hazards at the production of titanium alloys in the electric arc furnace
No full textThis article describes the metal titanium, its characteristics and properties, and the types of titanium alloys with regard to its microstructure. It also describes the production processes, i.e. the melting and casting processes of titanium alloys. The focus is on the production of titanium alloys by the electric arc process, and possible hazards in the production of titanium in electric arc furnaces are also described. Suitable protective measures to be taken in the event of a particular hazard are also highlighted. Concerning the occurrence of possible accidents in the production of titanium, a calculation is also presented that shows how much needs to be invested in protection against possible accidents while maximising profit. Finally, the application and casting process of titanium alloys in dentistry is presented
A thermodynamic model for predicting Ti and Al element of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag in electroslag remelting process
No full textThe control of titanium and aluminium in nickel-base superalloy with high titanium and low aluminium during the electroslag remelting (ESR) process has not been resolved well so far. The loss of titanium (Ti) and aluminium (Al) during the ESR process is critical to improve the high-temperature performance of GH4065A superalloy. A thermodynamic model based on the ion and molecule coexistence theory (IMCT) was developed to calculate the Ti and Al content of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag system during the ESR process of GH4065A superalloy. Results show that the order of the ability of each element in the slag system to weaken the loss of Al content is in the following order Al2O3 > CaO > CaF2, enhance the loss of Al content is SiO2 > FeO > TiO2, CaF2 > MgO and enhance the loss of Ti content is FeO > SiO2 > Al2O3 > CaO. Considering the influence of the slag system on the elements Al and Ti, the optimal ratio of the slag system is CaO = 15 w%∼20 w%, CaF2 ≥ 60 w%, Al2O3 = 18 w%∼25 w%, SiO2 ≤ 0.5 w%, TiO2 = 1 w%+(0.2 w%∼0.6 w%), MgO ≥ 4 w%, FeO ≤0.1 w%
Circular economy and recalling of the aluminum beverage cans
No full textModern-day residents enjoy a wide range of widely available food and beverages, resulting in the creation of a large amount of waste. In order to achieve sustainability, the European Commission proposed a new Action Plan for the Circular Economy in March 2020. The main objectives of this plan are to prevent waste and implement better waste management. Besides glass packaging and PET, the most commonly used containers for food and beverages are aluminium containers, which account for a significant share of waste. As aluminium is very suitable for recycling, considerable efforts are being made to increase the share of recycled aluminium in the production of aluminium packaging. In this paper, the recycling process of aluminium beverage cans is illustrated with a good example. In the first part, an overview of the efforts and successes in the recycling of aluminium packaging is given. In the first part, an overview is given of the effects of recycling on the reduction of greenhouse gases as well as on the reduction of energy consumption in relation to the primary production of aluminium. In the second part, the individual stages of the preparation and processing of aluminium waste up to the final product are described. The chemical and mechanical properties of the semi-finished products obtained were tested in various processing stages. The above-mentioned investigations were carried out to determine the basic properties of the secondary aluminium obtained in order to suggest the possibility of expanding its application in other industries
Influence of free forging and heat treatment on steel properties
No full textOvaj diplomski rad sastoji se od teorijskog i eksperimentalnog dijela. U teorijskom dijelu dane su teorijske osnove mehanizama očvrsnuća metalnih materijala, kovanja, podjele kovačkih strojeva, toplinske obrade te mjerenja tvrdoće Vickersovom metodom. U eksperimentalnom dijelu rada na konstrukcijskom čeliku S275JR (Č.0451) trakastog oblika proveden je eksperiment slobodnog kovanja na mehaničkom kovačkom stroju s različitim brojem udaraca batom od: 2, 5, 10 i 20 puta. Dio uzoraka svakog stupnja deformiranosti podvrgnut je toplinskoj obradi koja se sastoji od zagrijavanja na 850 °C te naglog hlađenja u vodi. Nakon provedenog eksperimenta kovanja te kovanja i naknadne toplinske obrade na sabijenim uzorcima provedena je metalografska analiza te izmjerena tvrdoća Vickersovom metodom po uzdužnom presjeku kovanih traka. Provedena je analiza rezultata izmjerenih tvrdoća i metalografskih snimaka mikrostrukture, uzoraka nakon kovanja i uzoraka nakon kovanja i toplinske obrade. Zaključuje se da se povećanje tvrdoće i smanjenje veličine zrna dešava nakon kovanja i naknadne toplinske obrade s povećanjem stupnja deformiranosti.This master’s thesis consists of a theoretical and an experimental part. The theoretical section provides the theoretical foundations of the mechanisms of strengthening metallic materials, forging, classification of forging machines, heat treatment, and hardness measurement using the Vickers method. In the experimental part of the study, an experiment involving free forging was conducted on structural steel S275JR (Č.0451), in strip form, using a mechanical forging machine with varying numbers of hammer blows: 2, 5, 10, and 20 times. A portion of the samples from each level of deformation underwent heat treatment, which involved heating to 850°C followed by rapid quenching in water. After the forging experiment, as well as forging followed by subsequent heat treatment on compacted samples, metallographic analysis was performed, and Vickers hardness was measured along the longitudinal cross-section of the forged strips. An analysis of the measured hardness results and metallographic microstructure images was conducted for samples after forging, as well as samples after forging and subsequent heat treatment. It is concluded that an increase in hardness and a reduction in grain size occur after forging and subsequent heat treatment with an increase in the degree of deformation
SEM analiza deformirane CuAlMnZr legure s prisjetiljivosti oblika
No full textLegure s prisjetljivosti oblika (eng. ShapeMemoryAlloys- SMA) su vrlo važni inženjerski metalni materijali, koji su zbog svojih poboljšanih svojstava zastupljeni u brojnim područjima istraživanja.U diplomskom radu prikazana je mikrostrukturna analiza deformirane CuAlMnZr legure s prisjetljivosti oblika koja je dobivena postupkom lijevanja u grafitnu kokilu te kovanjem u šipke promjera 13 mm. Na uzorcima je provedena i toplinska obrada zagrijavanjem na 850 °C u trajanju od 30 minuta te hlađenjem u vodi do sobne temperature. Mikrostrukturna analiza lijevanog i kovanog stanja CuAlMnZr legure provedena je svjetlosnom i pretražnom elektronskom mikroskopijom, dok je mikrostrukturna analiza nakon toplinske obrade provedena pretražnom elektronskom mikroskopijom. Rezultati su pokazali da uzorci nakon kovanja posjeduju dvofaznu (α+β) mikrostrukturu, dok je nakon toplinske obrade utvrđena martenzitna mikrostruktura. Cirkonij se kao legirajući element pojavljuje u obliku uključaka što dovodi do zaključka da se nije u potpunosti homogenizirao u talini.Shape memory alloys (SMA) are very important engineering metal materials, which are present in numerous research areas due to their improved properties. This paper presents the microstructural analysis of a deformed CuAlMnZr shape memory alloy casting into a graphite mold and forging into 13 mm diameter bars. The samples were heat treated by heating at 850 °C for 30 minutes and then cooling in water to room temperature. Microstructural analysis of the CuAlMnZr alloy in the as-cast and forged states was performed by light and scanning electron microscopy, while microstructural analysis after heat treatment was performed by scanning electron microscopy. The results showed that after forging, the samples exhibit a two-phase (α + β) microstructure, while after heat treatment, a martensitic microstructure was determined. As an alloying element, zirconium appears in the form of inclusions, suggesting that it was not completely homogenized in the melt
Nuclear accidents
No full textU ovom radu analiziraju se posljedice ozbiljnih nuklearnih nesreća koje su se dogodile u tri ključne nuklearne elektrane: Otok Tri Milje (1979.), Černobil (1986.), i Fukushima (2011.). Rad detaljno proučava različite aspekte tih nesreća, istražujući njihov utjecaj na zdravlje ljudi, ekonomiju i okoliš, te kako su te posljedice oblikovale lokalne zajednice i širu društvenu dinamiku. S posebnim fokusom na svaku od ovih nesreća, rad razmatra broj žrtava, gubitak resursa i dugoročne ekološke implikacije koje i dalje postoje. Također se analizira važnost sigurnosnih mjera, komunikacije i suradnje svih relevantnih dionika kako bi se naučene lekcije primijenile u budućim nepredviđenim situacijama. Kroz ovaj pregled, rad naglašava ključna naučena iskustva iz spomenutih nuklearnih nesreća i ističe korake prema boljoj pripremljenosti i efikasnoj komunikaciji u slučaju budućih nuklearnih nesreća.This paper analyzes the consequences of severe nuclear accidents that occurred at three major nuclear power plants: Three Mile Island (1979), Chernobyl (1986), and Fukushima (2011). The paper examines in detail various aspects of these accidents, their impacts on human health, the economy, and the environment, and the ways in which these consequences have shaped local communities and broader social dynamics. With particular attention to each of these disasters, the paper examines the number of fatalities, the loss of resources, and the long-term ecological impacts. The importance of safety measures, communication, and collaboration among all stakeholders will also be analyzed in order to apply lessons learned to future accidents. Through this review, the paper highlights key lessons learned from the mentioned nuclear accidents and highlights steps towards better preparedness and effective communication in case of future nuclear accidents
Procjena rizika od fizikalnih štetnosti u šumarstvu
No full textProcjena rizika je postupak kojim se utvrđuje razina opasnosti, štetnosti i napora u smislu nastanka
ozljede na radu i/ili profesionalne bolesti, koja bi uzrokovala štetne posljedice za sigurnost i
zdravlje radnika. U ovom radu definirane su i opisane vrste fizikalnih štetnosti (mikroklima, buka,
vibracije, svjetlost, zračenje) s kojima se može susresti bilo koji radnik. Pobliže su navedeni
posl ovi i sredstva rada u šumarstvu s naglaskom na fizikalne štetnosti s kojima se susreću radnici
u šumarstvu. Navedene su metode procjene rizika i objašnjen je postupak izrade procjene rizika,
kao dokumenta kojeg su dužni izraditi svi posl odavci na temelju Zakon a o zaštiti na radu.
Navedene su mjere zaštite na radu od fizikalnih štetnosti općenito i u šumarstvu, sukladno
odgovarajućoj zakonskoj regulativi
Evaluation of Sample Preparation Importance for Digital Image Correlation during Cold Deformation
No full textIn this paper, tests were performed by monitoring changes of strain amounts and their distribution by digital image correlation during static tensile testing of steel. The influence of different combination of speckles application on the sample surface (white speckles on the black sample surface and black speckles on the white sample surface) during cold deformation of steel was tested with the non-contacting digital image correlation. Strain amounts obtained by digital image correlation analysis of tested samples, with white on black and black on white painted speckle patterns, were compared. Different analysis for determining and monitoring strain amounts, provided by digital image correlation software, were used in this paper. The strain amounts were compared during cold deformation until the occurrence of sample fracture in both combinations of speckles application on the sample surface. Research has shown the importance of proper sample preparation for determination strain amounts and insignificant minor differences of strain amounts, between different sample preparations for digital image correlation, during cold deformation of tested steel
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 chemical composition Ti10Cr-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 (physiological solution, saliva and sweet carbonated beverage) at two temperatures (37 C and 39 C) in the same time interval. Concentrations of eluted metal ions were determined by inductively coupled plasma spectroscopy. The surface of the samples was observed by a light microscope and Vickers hardness was measured as well. pH of corrosive media was measured before and after the elution. The obtained results showed dependence of eluted metal ions on temperature as well as on type of corrosive media
Analysis of the densification of a biomedical titanium alloy produced by powder metallurgy
No full textTitanium as a raw material for production is very expensive due to its high price and the complex production process. One of the successful alternatives for the production of titanium alloys and final products is powder metallurgy technology. In this work, a Ti-20Zr alloy for biomedical applications was produced using the powder metallurgy process. The density values determined for the compacts depend on the compression pressure. Namely, the compressibility of the powder mixture increases with increasing compaction pressure. A higher sintering temperature as well as a longer sintering time are more favourable to obtain higher values for the sintered density. Similarly, the compression coefficient is lower for samples compacted at higher pressure, while its value increases with increasing sintering temperature. The volume change in the volume of the sample is more pronounced after sintering at higher temperature and shorter time