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Industrial production of the steel in ABS Sisak ltd
No full textProces proizvodnje čelika donio je napredak u gotovo svim industrijskim granama i
svakodnevnom životu ljudi. Čelik se može definirati kao legura željeza s ugljikom do 2,06 %
masenog udjela te s nizom drugih elemenata (sumpor, mangan, silicij, fosfor, titan, kalcij,
aluminij itd.). Čelik osim ugljika sadrži u sebi i brojne primjese, oligoelemente i plinove. Po
opsegu proizvodnje čelika u današnje vrijeme postupak pretaljivanja čeličnog otpada u
elektolučnim pećima je drugi po značenju odmah iza proizvodnje čelika u kisokovim
konvertorima. Tako dobiveni čelik se još obrađuje postupcima sekundarne metalurgije te se
kontinuirano lijeva.U ovom radu praćena je izrada jedne taline niskolegiranog Cr-Mo-Ni čelika u
industrijskoj proizvodnji u čeličani ABS Sisak d.o.o. Praćeni su procesni parametri svih faza
proizvodnje, počevši od pripreme uloška pa do lijevanja na postrojenju za kontinuirano lijevanje.The process of steel production has brought progress in almost all industries and people's daily lives. Steel can be defined as an alloy of iron with carbon up to 2.06 % by weight and with several other elements (sulfur, manganese, silicon, phosphorus, titanium, calcium, aluminum, etc.). In addition to carbon, steel also contains numerous impurities, trace elements and gases. According to the scope of steel production today, the process of remelting steel waste in electric arc furnaces is the second most important after steel production in oxygen converters. The steel produced like that is then processed by secondary metallurgy processes and is continuously cast. This paper will follow the production of one heat of low-alloy Cr-Mo-Ni steel in industrial production in the steel plant ABS Sisak ltd. The process parameters of all stages of production will be monitored, starting from the preparation of the scrap buckets to casting on the continuous casting machine
Effect of inoculation, cooling rate and charge composition on gray iron microstructure
No full textThis paper analyses the effect of different charge compositions for melt production, cooling rate (i.e. casting wall thickness) and inoculation on the gray iron microstructure. In this study, three gray iron melts were produced that had almost the same chemical composition. The proportions of steel scrap (SS), pig iron (PI), gray iron return (GIR) and SiC in charge were as follows: melt 1 (10 % SS, 39.4 % PI, 49.2 % GIR, 0.6 % SiC), melt 2 (38.8 % SS, 9.9 % PI, 47.9 % GIR, 1.6 % SiC) and melt 3 (0 % SS, 0 % PI, 99.2 % GIR, 0.06 % SiC). One uninoculated and one inoculated stepped test casting with walls thicknesses of 5, 10, 20, 45 and 65 mm was casted from each melt. The inoculant was added in the melt stream during pouring in the mould in an amount of 0.23 wt.%. The type, size and distribution of graphite flakes in the analysed walls did not significantly depend on the charge compositions. The structure of the metal matrix, carbides precipitation and type, size and distribution of graphite flakes were largely dependent on the wall thickness. As the wall thickness increased, the cooling rate decreased and the type of graphite flakes changed, from D and E through B to A type. Carbide formation has occurred in the edge region of the 5 mm thick walls. With the decrease of the cooling rate and increasing the proportion of D and E type graphite flakes, the ferrite content in the metal matrix increased. The carbide content in the edge region of the 5 mm thick walls was significantly reduced by inoculation. Inoculation increased the proportion of A type graphite flakes in the middle of 5 mm thick wall and in walls with a thickness from 10 to 65 mm. In addition, inoculation significantly reduced the proportion of B, D and E type graphite flakes or were completely eliminated. Wall thickness has affected this effect
Numerical simulation in optimization of thin-walled EN-GJL-200 casting
No full textGrey cast iron is frequently used in industry, due to good thermal conductivity, low price and good mechanical properties. Chemical properties and solidification conditions have significant influence on microstructure and mechanical properties development. Most common use of grey cast iron is in automotive industry and heating elements. The application in the casting of thinwalled castings requires careful elaboration of the technological casting process parameters due to the curving tendency and the burns appearance. Advantage of numerical simulations is in effective and fast calculation of pouring and solidification of castings. Economical advantage lays in fast change of more different product variations in short time. Experimental part of this paper has several versions of numerical simulation of casting process. First one is the original geometry, which has been used in regular casting process of thin-walled castings framework for fireplace doors. Other versions with optimizing geometry of the castings have been elaborated. Pouring process of all casting versions of EN GJL-200 quality was performed followed by investigation of casting quality and process parameters interaction. The influence of clamp position, ingates size and temperature distribution during casting solidification on microstructure development, hardness and tensile strength of grey cast iron EN GJL-200 casting samples was determined and compared with the results obtained by numerical simulation
Effect of sintering time and temperature on the microhardness of titanium-zirconium alloy
No full textTitanium and titanium alloys have been widely used in medicine as implant materials for the last 50 years. The reason for this could be found in a unique combination of biocompatibility and strength of these alloys. The main advantage of titanium is the ability to bind to bone and grow into the implant. Due to the high cost of production, titanium is not used in large quantities, and therefore research are focused on finding new, more economical alloys. For these reasons, the aim of this paper is to analyze the effect of powder metallurgy process parameters in the production of titanium alloy containing 20% zirconium. Starting elemental powders were a ball milled and then compacted using the hydraulic press. Sintering process was performed under the different values of time and temperature. Starting powders were characterized using the scanning electron microscope. Porosity was analyzed using the light microscope. It was found that it could be decreased by increase in sintering temperature. Microhardness of polished sintered samples was determined by Vickers method. Results showed that higher microhardness values were obtained in samples sintered at higher temperature. Finally, results show that titanium-zirconium alloy produced by this route of powder metallurgy could be potentially used in a biomedicine
Numerical simulations in the development of technological procedure of casting of gray cast castings of EN GJL-200 quality
No full textSivi lijev se tradicionalno odabire u industrijskoj primjeni zbog svoje dobre toplinske provodljivosti, povoljne cijene te širokog raspona mehaničkih svojstava. Utjecaj na konačnu mikrostrukturu i mehanička svojstva sivog lijeva imaju kemijski sastav i uvjeti skrućivanja. Sivi lijev najčešće je korištena legura iz familije željeznih ljevova u proizvodnji dijelova za automobilsku industriju te u domeni grijaćih tijela kamina i peći. Primjena u lijevanju tankostjenih odljevaka iziskuje pomnu razradu tehnološkog procesa lijevanja zbog sklonosti ka krivljenju te pojavi zapečenosti. Prednost numeričkih simulacija je učinkovito i brzo predviđanje tijeka lijevanja i skrućivanja te ekonomski isplativo modeliranje više varijanti u kratkom vremenu i njihova potencijalna utjecaja na svojstva konačnog proizvoda. U eksperimentalnom dijelu diplomskog rada provedene su simulacije za ukupno četiri verzije geometrije odljevka pri čemu je jedna verzija originalna geometrija koja se koristi za proizvodnju tankostjenog odljevka koji služi kao okvir vrata kamina, a optimiranjem geometrije razrađene su još tri verzije tog odljevka. Eksperimentalno je provedeno lijevanje i ispitivanje kvalitete odljevka i svojstva sve četiri verzije okvira vrata kamina od sivog lijeva kvalitete EN GJL-200. Utvrđen je utjecaj pozicije spone i veličine odzračnika na raspodjelu temperatura pri skrućivanju odljevka te na promjenu mikrostrukture, tvrdoću i vlačnu čvrstoću odljevaka od sivog lijeva kvalitete EN GJL-200.Gray cast iron is frequently used in industry, due to good thermal conductivity, low price and good mechanical properties. Chemical properties and solidification conditions have significant influence on microstructure and mechanical properties development. Most common use of gray cast iron is in automotive industry and heating elements. The application in the casting of thin-walled castings requires careful elaboration of the technological casting process due to the curving tendency and the burns appearance. Advantage of numerical simulations is in effective and fast calculation of pouring and solidification of castings. Economical advantage lays in fast change of more different product variations in short time. Experimental part of this paper has four versions of numerical simulation of casting process. First one is the original geometry, which has been used in casting of thin-walled castings framework for fireplace doors. With optimizing geometry other three versions of the castings have been elaborated. Pouring process of all four versions of fireplace door frameworks form grey cast iron EN GJL-200 quality was performed followed by investigation of casting quality and properties. Influence of clamp position and the vents size were determined on temperature distribution during casting solidification, as well as theirs influence on microstructure development, hardness and tensile strength of gray cast iron EN GJL-200 casting samples
Characteristics of the appearance of the Portevin-Le Chatelier effect in AlMg alloys during cold deformation
No full textAluminij i aluminijske legure su posljednjih godina postali nezamjenjiv materijal u mnogim industrijama. Neke legure aluminija pokazuju lokaliziranu deformaciju, takozvani Portevin-Le Chatelier efekt pri određenim brzinama deformacije i temperaturama. Takva lokalizirana deformacija uzrokuje razne probleme u industriji. Iz tog razloga je potrebno saznati više o Portevin-Le Chatelier efektu. U ovom radu istraživana je karakteristika pojave Portevin-Le Chatelier efekta kod AlMg legure tijekom hladne deformacije metodama statičkog vlačnog pokusa, termografije, digitalne korelacije slike (DIC) i metalografskom analizom mikrostrukture. Istraživanjem je utvrđena pojava Portevin-Le Chatelier efekta kod AlMg legure. Metodom digitalne korelacije slike je utvrđeno kako je pojava Portevin-Le Chatelier efekta brza i jasno uočljiva na DIC videu te kako dolazi do skokovitih promjena u deformaciji. Iz rezultata dobivenih metodom termografije je utvrđeno da tijekom skokovitog porasta u deformaciji dolazi do skokovitog porasta u temperaturi. Utvrđeno je da su skokovite promjene u deformaciji i temperaturi međusobno povezane. Ispitivanjem mikrostrukture je utvrđeno da je ispred PLC linije lijevana struktura, a na samoj liniji fronte dolazi do znatne deformacije i preorijentiranja zrna u smjeru razvlačenja.In recent years, aluminum and aluminum alloys have become an irreplacable material in many industries. Some aluminum alloys exhibit localized deformation, the so-called Portevin-Le Chatelier effect, at certain deformation rates and temperatures. Such localized deformation causes various problems in industry. For this reason, it is necessary to learn more about Portevin-Le Chatelier effect. In this paper, the characteristics of the appearance of the PortevinLe Chatelier effect in AlMg alloys during cold deformation were investigated by static tensile test, thermography, digital image correlation and metallographic microstructure analysis. Research determined the occurence of the Portevin-Le Chatelier effect in the investigated AlMg
alloy. Using the digital image correlation, it was determined that the appearance of the PortevinLe Chatelier effect is fast and clearly visible phenomenon on the DIC video, and that during it sudden changes in deformation occur. During analysis using thermography method, it was determined that there are sudden increase in temperature. It was determined that sudden changes in deformation and in temperature are connected. Investigation of the microstructure revealed that in front of the PLC line there is a casting structure, at the front line itself there is considerable deformation and reorienation of the grains in the direction of stretching
Characterization of applied titanium (IV) oxide photocatalyst on the carbon fibers
No full textNapretkom društva i industrije raste i potrošnja čiste vode te se stvaraju sve veće količine otpadne vode koja je onečišćena raznim organskim i anorganskim tvarima. Mikroonečišćujuće tvari predstavljaju najveću opasnost koja proizlazi od njihovih potencijalnih svojstava da uzrokuju neželjene kemijske reakcije u okolišu koje utječu na zdravlje ljudi. Vrlo ih je teško ili gotovo nemoguće ukloniti standardnim mehaničkim i biološkim procesima. Metode koje bi se mogle upotrebljavati u pročišćavanju otpadnih voda su napredni oksidacijski postupci kao što je fotokataliza. Za proces fotokatalize potrebna je prisutnost fotokatalizatora, a jedan od fotokatalizatora koji se najčešće upotrebljava je TiO2. U ovom radu istraženi su fotokatalizatori koji su pripravljeni nanošenjem TiO2 na karbonska vlakna i sol – gel metodom na staklena vlakna te je ispitan utjecaj na fotokatalitička svojstva.With the progress of society and industry, the consumption of clean water is also increasing, and increasing amounts of waste water are created that are contaminated with various organic and inorganic substances. Micropollutants represent the greatest danger arising from their potential properties to cause unwanted chemical reactions in the environment that affect human health. They are very difficult or almost impossible to remove by standard mechanical and biological processes. Methods that could be used in wastewater treatment are advanced oxidation processes such as photocatalysis. The photocatalysis process requires the presence of a photocatalyst, and one of the photocatalysts used is TiO2. In this work, photocatalysts prepared by applying TiO2 to carbon fibers and by the sol-gel method to glass fibers were investigated, and the influence on the photocatalytic properties was examined
The influence of iron impurities on the compression behavior of Al-2.24Mg-2.09Li alloy
No full textAs a major impurity element in aluminium-lithium (Al-Li) alloys, iron (Fe) reduces formability, fracture toughness, and
fatigue resistance by solidifying into Al6Fe and Al3Fe particles. The research was performed in order to estimate the
influence of Fe impurities on the compression behaviour of Al-2.24Mg-2.09Li alloy. The investigation was performed on
the samples in as cast and solution hardened condition. The solution hardening was applied to improve the mechanical
properties by dissolving intermetallic particles and enriching αAl matrix with Mg. However, the higher strength properties
and temperature increase during the compression testing were observed in as cast condition. Microstructural investigation
revealed significant differences in microstructure changes between the samples in as cast and solution hardened condition.
In as cast sample the barrelling effect led to the unequal deformation and surface texture development. The eutectic Al3Fe
particles located in the αAl interdendritic areas did not significantly impact microstructure changes. Although the solution
hardening led to enrichment of αAl matrix with Mg and Fe, the Al3Fe particles were not dissolved. The coarse morphology
of Al3Fe particles and location at the grain boundaries of αAl grains contributed to low energy intergranular fracture. The
fracture nucleation and propagation across the grain boundaries resulted in lower strength values
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
Effect of heat treatment on microstructure and thermal properties of Cu-based shape memory ribbons
No full textThe aim in this work was to investigate the change in microstructure, phase transformation temperatures, and thermal properties due to the quenching of the investigated Cu-Al-Mn and Cu-Al-Mn-Ti alloys in ribbons form. This paper presents the results of microstructure analysis and thermal properties of Cu-Al-Mn and Cu-Al-Mn-Ti shape memory alloys produced in form of ribbons by melt spinning technique. The microstructural analysis was carried out before and after quenching. After casting of the investigated alloys annealing at 900 °C for 30 min was performed, followed by water quenching. The microstructural analysis was carried out by optical and scanning electron microscopy equipped with an energy dispersive spectrometer and by X-ray diffractometer. Thermodynamic calculation of a ternary Cu-Al-Mn system in equilibrium condition was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry and by electrical resistance measuring. The results of microstructural analysis show the presence of martensite microstructures before and after quenching in the Cu-Al-Mn alloy, while in the Cu-Al-Mn-Ti alloy martensite microstructure exists only after quenching. Phase transformation temperatures were decreased after quenching and titanium addition