Repository of Faculty of Metallurgy University of Zagreb
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Migracija nikla iz nakita od čelika
No full textUloga nakita u životu čovjeka vrlo malo se mijenjala kroz povijest. Uglavnom se nakit koristi za ukrašavanje ljudskog tijela, ali i kao statusni simbol ili za izražavanje pripadnosti određenim grupama ili kulturama. Međutim, procesi proizvodnje nakita značajno su napredovali. Istraživanja vezana uz utjecaj pojedinih komponenti iz nakita na zdravlje čovjeka također su značajno napredovala. Poznato je da tijekom nošenja dolazi do interakcije nakita s kožom. Znoj koji se oslobađa na koži utječe na migraciju teških metala. Ova pojava je posebno izražena kod nakita koji je napravljen od neplemenitih metala (npr. od ugljičnog čelika i sl.). U ovom radu istraživana je migracija iona nikla iz nakita napravljenog od različitih vrsta čelika koji je bio u kontaktu s modelnom otopinom znoja. Dobiveni rezultati su pokazali da dolazi do migracije navedenih iona. Koncentracija iona koja migrira uslijed kontakta nakita i modelne otopine znoja ovisi o vremenu kontakta
Analiza posuđa od nehrđajućeg čelika
No full textOd prapovijesnih dana pa sve do danas posuđe je korišteno za pripremu, čuvanje i posluživanje hrane. Nekada se izrađivalo od materijala koji su pronađeni u prirodi. Danas nove tehnologije omogućavaju izradu posuđa od sofisticiranih materijala koji su otporni na visoke temperature, oštećenja, osiguravaju neprianjanje hrane prilikom termičke obrade i sl. Sve navedeno ujedno donosi i određene opasnosti koje se odnose na migraciju elemenata iz posuđa u hranu. U ovom radu istraživana je migracija iona As, Cd, Cr, Ni, Pb i Zn iz posuđa od nehrđajućeg čelika u ovisnosti o vremenu, a uslijed kontakta posuđa s hranom. Istraživanja su provedena korištenjem dvije modelne otopine koje su simulirale kiselu hranu. Otopine i posuđe bili su u kontaktu 2 h, 24 h, 4 dana i 10 dana pri sobnoj temperaturi. Dobiveni rezultati su pokazali da dolazi do migracije nikla i kroma ovisno o vremenu kontakta posuđa s hranom, ali i o starosti posuđa. Koncentracije iona koji su migrirali bile su u rasponu od 0, 0040 do 0, 0130 mg/l za krom, odnosno od 0, 0011 do 0, 0372 mg/l za nikal
Application of characterisation methods in the development of biomedical titanium alloys
No full textBiomaterials are becoming an increasingly important research topic over time as they are used to replace parts and functions of the human body, helping to improve the quality of human life. Titanium alloys are particularly important for the development of new biomaterials. Commercial pure titanium and its alloys are used as essential structural biomaterials in the manufacture of implants due to their excellent biocompatibility, good corrosion resistance and mechanical strength. However, studies have shown that aluminum and vanadium ions are released in alloys such as Ti-6Al-4V, which can cause health problems over time. Because of the problems that occur, researchers are working to improve the properties of titanium alloys by adding new elements. In most cases, different metals are added to titanium and it is known that with the presence of different metals, the properties of titanium also change. All biomedical titanium alloys must undergo various testing procedures before they can be used. The article describes the characterisation methods used in the development of titanium alloys, such as: light and scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction analysis, differential scanning calorimetry, differential thermal analysis. The reliability of the results depends on the methods used and the avoidance of errors in the characterisation of biomedical alloys in order to reach better conclusions and produce alloys of the highest quality desirable for use in the human body
The Deformation Behavior of Niobium Microalloyed Steel during Lüders Band Formation
No full textIn microalloyed steels, plastic instabilities often appear which have been found to be associated with changes in the microstructure. In this paper, research was carried out on the influence of the microstructure in different areas of the deformation zone during the formation of Lüders bands in niobium microalloyed steel. Thermography and digital image correlation during static tensile testing were used to research deformation behavior and the area before and during the formation of the Lüders band. Different local values of temperature changes, i.e., stress changes, and strains in the examined areas during the formation of the Lüders band were determined. The highest values of the temperature changes and strains during the formation of the Lüders band were measured in the area of the initial appearance of the Lüders band. In order to clarify the observed changes, a microstructural analysis, using X-ray diffraction, scanning electron and transmission electron microscopy methods, was used. It was established that the observed temperature, i.e., stress, and strain changes are related to changes in the microstructure. The analyses of changes in the microstructure, arrangement and interaction of dislocations with precipitates revealed significant changes in the movement of dislocations and their interaction with fine niobium-containing precipitates during the formation of Lüders bands. The influence of microstructural parameters on the Lüders band formation in niobium microalloyed steel has been established based on this research
The importance of standards in personal protective equipment
No full textNorme su danas vrlo važne i predstavljaju veliku važnost na svim poljima, jer njihovo prihvaćanje i primjena u svakodnevnom životu ljudi i organizacija pridonosi kvalitetnijem životu na korist svih u cijelome svijetu. Zahtjevi za postizanjem i uspostavljanjem kvalitete propisani su normama koje se razlikuju po svojim zahtjevima, ovisno o području na koje se odnose. Prilikom odabira osobne zaštitne opreme, za zaposlenike koji obavljaju poslove s povećanim rizicima za zdravlje i sigurnost na radu, norme predstavljaju sve veću važnost obzirom da je potrebno zadovoljiti zahtjeve određenih normi kako bi se smanjio rizik ozljeđivanja zaposlenika pri čemu je jedna od važnijih normi za zaštitnu odjeću, norma HRN EN ISO 13688:2013. Uz ovu normu u pravilu se koriste i dodatno propisuju zahtjevi specifičnih normi za različitu opremu i dijelove tijela. U završnom radu prikazana je i objašnjena važnost različitih normi kod osobne zaštitne opreme, u prvom redu zaštitne odjeće i obuće, i njihove dosljedne primjene s naglaskom na osobnu zaštitnu opremu koju koriste policijski službenici pri obavljanju svakodnevnih radnih obaveza. Ispunjavanje propisanih zahtjeva različitih normi za zaštitnu odjeću, obuću i opremu za različite dijelove tijela na primjeru policijskih službenika pokazala se kao vrlo važna stavka za njihovu sigurnost i zdravlje na radu odnosno za smanjenje rizika ozljeđivanja tijekom obavljanja svakodnevnih poslova.Standards are very important today and represent great importance in all fields, because their acceptance and application in the life of people and organizations contributes to the better quality of life and benefit of everyone in the whole world. The requirements for achieving and establishing quality are prescribed by standards that differ in terms of their requirements, depending on the field of application. For employees who perform tasks with increased risks for health and safety at work, standards are increasingly important during choosing protective equipment, given that it is necessary to meet the requirements of certain standards in order to reduce the risk of injury to employee. One of the most important standards for protective clothing is HRN EN ISO 13688:2013. In addition to this standard, the requirements of specific standards for different equipment and body parts are used and prescribed. The paper shows and explains the importance of different standards for personal protective equipment, primarily protective clothing and footwear, and their consistent application with an emphasis on personal protective equipment used by police officers daily duties. The examples of fullfiling the prescribed requirements of different standards for protective clothing, footwear and equipment for different body parts of police officers proved to be very important for their safety and health at work, i.e. for reducing the risk of injury at work
The effect of noise on humans and neasures of protection against noise at the workplaces
No full textBuka je svaki neželjeni zvuk koji utječe na sluh, ali i na ljudsko zdravlje, tako što uzrokuje
psihičke i fizičke smetnje. Ona loše utječe na naše živote, kao i na našu okolinu te je moramo
pravovremeno prepoznati, analizirati i smanjiti. Buka koja na radnom mjestu utječe na
zdravlje radnika može uzrokovati profesionalne bolesti, zbog čega dolazi do narušavanja
zdravstvene sposobnosti radnika, ali i smanjenje produktivnosti industrijskih postrojenja.
Kako bi se utvrdio i vrednovao rizik kod izloženosti buci, obavezno se moraju provesti
mjerenja buke. Mjerenja je potrebno u odgovarajućim periodima planirati i provoditi od strane
ovlaštenog stručnjaka, a mjerni instrumenti moraju biti pouzdani, kalibrirani i u dobrom
stanju. Mjerenja se moraju provesti za sva radna mjesta i za sve osobe koje će možda biti
izložene buci. U okviru procjene rizika određuje se stvarna izloženost buci za svakog radnika
koji sudjeluje u radnom procesu. Ukoliko vrijednosti premašuju one određene Zakonima i
pravilnicima, preporučuju se odgovarajuće mjere zaštite od buke. U ovom radu izmjerene su
vrijednosti buke na različitim radnim mjestima u industriji za gospodarenje otpadom.
Prilikom analiziranja rezultata vidljiva su prekoračenja dopuštenih vrijednosti za buku u
zatvorenoj kabini radnog stroja i buku u otvorenoj kabini viličara na ruti kroz postrojenje te
je preporučena primjena sredstava za zaštitu sluha i upotreba osobne zaštitne opreme.Noise is any unwanted sound that affects hearing, as well as human health, by causing mental
and physcial disturbances. It has a bad effect on our lives, as well as on our environment, and
we must recognize, analyze and recude it in a timely manner. Noise that affevts the health of
woekws at the workplaces can cause occupational diseases, which can impair the health of
workes, as well as reduce the productivity of industrial plants. In order to determine and
evaluate the risk of expouse to noise, noise measurements must be carried out. Measurements
must be planned carried out at appropriate intervals by an authorized expert, and the
measuring instruments must be reliable, calibrated and in good condition.Measurements
musre be carred out for all workplaces and for all person who may be exponsed to noise. As
part of the risk assessment, the actualexposure to noise is determined by Laws and
Refulations, appropriate noise protection measures are recommended. In this work, noise
values were at diffrent workplaces in the waste managment industry. When analyzing the
results, the permissible values in the waste for noise in the closed cabin of the worrking
machine and the noise in the open cabin of the forklift on the routine through the plant werw
exceeded, and the use of hearing protection and the use of personal protective equipment were
recommended
Determining the ratio of the metal components of the charge at the cupola furnace
No full textTalilna peč je najpomembnejša oprema v livarni. Za taljenje litega železa se uporabljajo različne vrste peči. Pri pripravi taline za visoko stopnjo proizvodnje se v obratih za litje železa uporabljajo predvsem kupolke ali električne talilne peči. Glavne prednosti kupolk v primerjavi z električnimi so: enostavna in gospodarna naprava, manj škodljiva za okolje, manjša občutljivost na nizkokakovostne materiale šarže in onesnaževalce, oksidacijske in redukcijske reakcije med taljenjem v kupolki potekajo znotraj talilne cone in nad njo, kar omogoča uporabo visoko oksidiranega in nizkokakovostnega odpadnega materiala, cenejših zlitin in nekovinskih dodatkov. Ena osnovnih tehnoloških težav pri delovanju kupolke je določitev razmerij med komponentami šarže, ki jo sestavljajo koks, topilo in kovinska šarža, da bi ustvarili talino z želeno kemijsko sestavo. V praksi je masno razmerje kovinske šarže in koksa v določenih vrednostih, prav tako tudi skupna masa topila glede na maso koksa. Izkazalo se je, da je glavna težava določitev sestavin kovinskega dela šarže, ki je običajno sestavljena iz odpadkov iz lastne proizvodnje, jeklenega odpada, kupljene sive litine, nodularne litine, silicijevega mangana, ferosilicija itd. V tem prispevku smo z metodo izbire iz razpoložljivega razpona izračunali deleže kovinskih komponent kovinskega dela šarže za izdelavo taline iz sive litine, standardizirane pod oznako EN-GJL-250.The most important equipment in a foundry is the melting furnace. Various types of furnaces have been used for cast iron melting. In cases of melt preparation for production at high capacities, the primary melting methods used in iron casting plants are cupola furnaces or electric melt furnaces. The main advantages of cupola furnaces compared to electric ones are: simple and economical device, less harmful to the environment, less sensitive to low-quality charge materials and contaminants, oxidation and reduction reactions take place within and above the melt zone during cupola melting, which allows the use of highly oxidized and low-quality scrap material, lower prices of alloys and non-metallic additions. One of the basic technological problems in the work of the cupola furnace is to determine the relationships between the charge components consisting of coke, flux, and metal charge to obtain a melt of a given chemical composition. In practice, the mass ratio of metal charge and coke is in certain mass relations as well as the total mass of flux in relation to the mass of coke. It turns out that the main problem is to determine the components of the metal part of the charge, which usually consists of waste of own production, steel scrap, purchased cast iron, nodular cast iron, silicon manganese, ferrosilicon, etc. In this paper, using the method of selection from the available range, the proportions of metal components of the metal part of the charge were calculated to produce a gray cast iron melt standardized with the code EN-GJL-250
Metal Ions Release from Welded Co—Cr Dental Alloys
No full textCobalt–chromium alloys (Co-Cr) are widely used in dentistry due to their excellent mechanical properties and corrosion resistance. Since prosthetic materials must be permanently stable in the oral cavity, it is very important to determine the release of ions from alloys in the oral cavity. In dentistry today, metals and alloys are mainly joined by laser and tungsten inert gas (TIG) welding. Therefore, in this work, the release of metal ions from six different Co-Cr alloys joined by these two welding methods was quantified to determine the effects of the welding method on an ion release. Static immersion tests, atomic absorption spectrometry and statistical analysis were performed for this purpose. The results showed that laser-welded alloys release a lower amount of metal ions compared to TIG-welded alloys
Investigation of Laser-Welded Co-Cr Dental Alloys by Microscopy and Mechanical Testing
No full textIn order to improve the hold and function of dentures for the patient, various prostheses made of metal, mostly metal alloys, are used every day in dental practise. Cobalt-chromium alloys are usually the first choice because they have very good mechanical properties and satisfactory clinical conditions. Nowadays, laser welding is increasingly used in dental practise due to its numerous advantages over other technologies. In this work, therefore, six commercially available Co-Cr alloys were investigated. Three of them are used for metal-ceramic work, two for denture frameworks and one is suitable for both applications. They were joined by laser welding and subsequently analysed microscopically. Their mechanical properties were determined and statistically evaluated. The microhardness of the laser-welded alloys is in the range of 282–465 MPa in the weld zone and between 283 and 435 MPa in the heat-affected zone. The flexural strength of the laser-welded alloys is lower than the control group, but an alloy for the metal-ceramic work (I-BOND NF) shows very similar value. Furthermore, this alloy, together with two other metal-ceramic alloys, survived a maximum of cycles in dynamic tests. It was found that the laser method can be used for joining Co-Cr alloys while ensuring appropriate parameters that guarantee the quality of the dental work
Production waste management in the steel plant
No full textOtpad koji je proizveden općenito u industrijskim postrojenjima najčešće se klasificira pod opasni otpad koji je štetan za okoliš i ljudsko zdravlje. Proizvodni otpad se određuje ključnim brojevima te se na taj način identificira koliko je opasan za okoliš s obzirom na njegov kemijski sastav. Postoji nekoliko vrsta proizvodnog otpada u čeličani kao što su troska, kruti otpad (prašina) od obrade plinova koji sadrži opasne tvari, cunder i sl. Osim troske, cundera i prašine, u procesu proizvodnje čelika dolazi do istrošenosti vatrostalnog materijala i lomljenja grafitnih elektroda.
Kroz ovaj rad dotaknuti ćemo se pitanja na koji način nastaje proizvodni otpad u čeličani, što sve spada u proizvodni otpad, kako zbrinuti taj otpad odnosno postoji li način da se upotrijebi u neke druge svrhe.Waste that is generally produced in industrial plants is most often classified as hazardous waste that is harmful to the environment and human health. Production waste is determined by key numbers, and in this way, it is determined how dangerous it is for the environment with regard to its chemical composition. There are several types of production waste in steel works, such as slag, solid waste (dust) from gas processing containing hazardous substances, scale, etc. In addition to scale, slag and electric arc furnace dust, in the steel production process there is wear of refractory material and breakage of graphite electrodes.
Through this paper, we will touch upon the question of how production waste in steel works is generated, what all falls into production waste, how to dispose of that waste, or whether there is a way to use it for some other purpose