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Overview of casting defects in ductile cast iron
No full textObjective of this article is to provide an overview of common casting defects occurred during production of ductile cast iron (DCI) and the influence of non-metallic inclusions in the DCI. These defects are referred to slag, sand mould or other foreign substances that are imbedded in the surface, or underneath. The research was investigated on ductile cast iron samples using optical microscopy and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). With SEM image position, shape and type of inclusion could be defined while EDS analysis reveals chemical composition of particular formations. The investigation of casting defects indicates necessity of DCI production parameters control. This article deals with investigation of surface defects in DCI such as non-metallic inclusions (Al2O3, SiO2, MgO, CaO, MnO, FeO, Fe2O3) which mostly originate from slag, melt oxidation, reactions with refractory materials, mould erosion, and melt treatment interactions
Steel slags from the electric arc furnace process as by-product
Get PDFU proizvodnji čelika elektropećnim postupkom nastaju dvije različite vrste troske, crna koja nastaje u elektrolučnoj peći i bijela koja nastaje u lonac-peći. Nastale troske se prije zbrinjavanja miješaju i predaju ovlaštenom sakupljaču uz određene troškove. Da bi trosku, koja kao proizvodni ostatak ima svoju uporabnu vrijednost, tretirali kao nusproizvod, potrebno je zadovoljiti određene uvjete, od kojih je najvažniji utvrđivanje fizikalno-kemijskih karakteristika.
U ovom radu su uspoređene crna i bijela troska s obzirom na njihove fizikalno-kemijske karakteristike te, s obzirom na različitosti prikazane su mogućnosti upotrebe istih. Prema literaturnim podacima obje troske su neopasni otpad, a kao takav se mogu koristiti u razne svrhe (cementnoj industriji, cestogradnji kao zamjena prirodnih mineralnih agregata, poljoprivredi kao poboljšivači tla itd). Kemijski sastav troski je pokazao da se bijela troska od crne najviše razlikuje po sadržaju Ca i Mg zbog čega se ove troske ne bi smjele miješati. Naime, s obzirom na navedeno, svaka od njih može pronaći svoju specifičnu namjenu i mjesto na tržištu. Stoga bi trebalo navedene troske, uz zadovoljavanje zakonom propisanih uvjeta, preimenovati iz otpada u nusproizvod, a time bi se umjesto odlaganja troske, iste predale kupcima, što bi pridonijelo smanjenju troškova proizvodnje sirovog čelika te u konačnici dovelo do približavanja procesa proizvodnje čelika načelima kružnog gospodarstva.In the production of steel by the electric arc furnace (EAF) process two different types of slags were produced, EAF slag or black slag and ladle furnace (LF) slag or a white slag. Produced slags prior to disposal were mixed and handed to a licensed waste collector with certain costs. In order to treat slags, remains from production with its usage value, as a co product, it is necessary to meet certain conditions of which the most important are physico-chemical characteristics.
In this paper the black and white slag were compared through their physico-chemical characteristics, and regarding their differences, the possibilities of using them were shown. According the literature it was established that both slags are non-hazardous waste, and as such can be used for various purposes (cement industry, road construction as a substitute for natural mineral aggregates, agriculture for soil improvement etc.). The chemical composition of the slags showed that the white slag from black differs most in the content of Ca and Mg so that those slags should be collected separately. Namely, with regard to the above, each of them can find their specific purpose and a place in the market. Therefore, mentioned slags, through meeting the legal issued conditions, should be renamed from the waste to co-product, and therefore instead of disposal slag should be handed to customers, which would contribute to reducing the production cost of crude steel and at the end to the approaching of steel production process toward principles of the circular economy
Primjena najbolje raspoloživih tehnika za prevenciju i kontrolu onečišćenja voda u rafinerijama
Get PDFUporaba raznih naftnih proizvoda danas je svakodnevica, no unatoč njihovoj velikoj
primjeni, eksploatacija, transport i preradba sirove nafte predstavlja potencijalnu opasnost za
okoliš. Rafinerije prilikom preradbe sirove nafte upravljaju ogromnim količinama sirovina i
proizvoda te su intenzivni potrošači energije i vode, koje se koriste za provođenje velikog
broja rafinerijskih procesa. Procesi odvajanja, preradbe i obrade sirove nafte su izraziti izvori
emisija u zrak, vodu i tlo, a među najvećim izvorima onečišćenja su procesi katalitičkog
krekiranja, hidrokrekiranja, koksiranja te hidrodesulfurizacije.
U ovom radu, naglasak je dan na emisije u vodu koje se javljaju u okviru rafinerijskog
postrojenja te na primjenu najbolje raspoloživih tehnika, s ciljem prevencije i kontrole
onečišćenja te obrade otpadnih voda u rafinerijama. Ukazan je doprinos integriranog vodenog
toka u rafinerijama, koji omogućuje ponovnu uporabu procesne vode, smanjenje emisija u
vode pri ispuštanju te ujedno i smanjenje operativnih troškova rafinerije.Despite the big consumption of various petroleum products, the exploitation, transportation
and processing of crude oil presents a potential environmental risk. Refineries are industrial
sites that manage huge amounts of raw materials and products and are also intensive
consumers of energy and water. The separation process, processing and treatment of crude oil
are significant sources of emissions into air, water and soil, and among the largest sources of
pollution are catalytic cracking, hydrocracking, coking and hydrodesulphurization.
In this paper, the emphasis is given to water emissions that occur within the refinery and to
the application of the best available techniques for the prevention and control of pollution and
wastewater treatment. It was pointed out the integrated water flow in the refinery, which
allows reuse of process water, reduction of emissions to water as well as reduction of refinery
operational costs
The effect of rolling and heat treatment on properties of Cu-Al-Mn shape memory alloys
Get PDFU radu su istraživana svojstva Cu-8,3%Al-9,4%Mn (mas.%) legure s prisjetljivosti oblika,
nakon toplog i hladnog valjanja. Šipka promjera 8 mm iz Cu-Al-Mn legure, proizvedena je
postupkom vertikalnog kontinuiranog lijevanja. Nakon lijevanja provedeno je toplo i hladno
valjanje. Toplim valjanjem dobivena je traka debljine 1,75 mm, a hladnim valjanjem traka
debljine 1,02 mm. Nakon postupka valjanja uslijedila je toplinska obrada. Toplinska obrada se
sastojala od žarenja na 900° C, držanja 30 minuta na toj temperaturi te hlađenja u vodi.
Karakterizacija mikrostrukture ispitivane Cu-Al-Mn legure provedena je pomoću optičke
mikroskopije (OM) i pretražne elektronske mikroskopije (SEM) opremljene uređajem za
energetsko disperzijsku spektroskopiju (EDS). Temperature transformacije i fuzijske entalpije
određene su diferencijalno skenirajućom kalorimetrijom (DSC). Tvrdoća Cu-Al-Mn legure
prije i nakon valjanja i toplinske obrade određena je Vickersovom metodom (HV10).In the paper, the properties of Cu-8.3%Al-9.4%Mn (wt.%) of shape memory alloy were
investigated after hot and cold rolling. The 8 mm diameter rod of Cu-Al-Mn alloy was
produced by vertical continuous casting. After casting, hot and cold rolling was carried out.
Hot rolling produced a strip of 1.75 mm thick and a cold rolling strip of 1.02 mm thick. After
the rolling process was followed by heat treatment. Heat treatment consisted of annealing at
900 °C, holding for 30 minutes at that temperature and cooling in water. Characterization of
the microstructure of the Cu-Al-Mn alloy was performed by optical microscopy (OM) and
scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS).
Temperature transformation and fusion enthalpy were determined by differential scanning
calorimetry (DSC). The hardness of Cu-Al-Mn alloys before and after rolling and heat
treatment was determined by the Vickers method (HV10)
Influence of composition and parameters of deformation on mechanical propertis of pipes
No full textU radu su prikazani rezultati primjeneumjetnih neuronskih mreža u određivanju utjecaja kemijskog sastava čelika na mehanička svojstva toplovaljanetrake i toplovaljanih šavnih cijevi. Proveden je trening neuronske mreže na rezultatima ispitivanja kemijskih i mehaničkih svojstava od 159 uzoraka. Za zadani je problem određena najpovoljnija građa neuronske mreže. Dokazano je da je korištenjem većeg broja eksperimentalnih mjerenja, moguće pouzdano istrenirati mrežu i naučiti je da uspješno procijeni mehanička svojstva trake i cijevi. Utvrđen je utjecaj ugljika i mangana na mehanička svojstva toplovaljane trake. Posebno je istražen utjecaj kemijskog sastava čelika, mehaničkih svojstava toplovaljane trake, početne temperaturae i stupnja deformacije toplog valjanja šavnih cijevi na njihova mehanička svojstva. Utvrđeno je da ugljik ima veći utjecaj na mehanička svojstava od mangana. Provedena ispitivanja su pokazala da početna temperatura valjanja cijevi ima značajan utjecaj na njihova mehanička svojstva.The paper presents the results of the application of artificial neural networks to determine the influence of the chemical composition of steel on the mechanical properties of hot rolled strip and hot rolled welded pipes. The training of the neural network was conducted on the test results of chemical and mechanical properties of 159 samples. Best structure of neural network for given problem was defined. It has been proven that with use of large number of experimental measurments it is possible to train and learn network to predict mechanical properties of hot-rolled strip and hot rolled welded pipes. Influence of carbon and manganese on mechanical properties has been determined. Especially influence of the chemical composition of steel, hot-rolled strip mechanical properties, initial temperature detected and the degree of deformation of the hot rolling of welded pipes to their mechanical properties was inspected. It was found that the carbon has a greater influence on the mechanical properties than manganese. The conducted tests have shown that the initial temperature of the rolling of pipe has a significant impact on their mechanical properties
Use of slag from the electric arc furnace steel making process in the agriculture
No full textProizvodnjom čelika elektropećnim postupkom nastaju velike količine troske. S obzirom na elektropećni postupak nastaju dvije vrste troske, a to su crna troska koja nastaje u elektrolučnoj peći i bijela troska koja nastaje u lonac peći. Troske se prema svojim fizikalno-kemijskim karakteristikama svrstavaju u neopasni otpad te se mogu odlagati na predviđena odlagališta. Odlaganje se pokušava izbjeći s obzirom na visoke cijene, moguća onečišćenja tla, gubitka obradivih zemljišnih površina, te u slučaju troske gubitka njenih vrijednih sastojaka samim odlaganjem. U skoroj budućnosti Europska i Hrvatska politika nalažu nultu stopu odlaganja te se time pokušava pronaći kako i gdje možemo primijeniti trosku. Tako se troske danas koriste u građevini, cestogradnji pa i u poljoprivredi.
U ovom radu prikazane su fizikalno-kemijske karakteristike crne i bijele troske te kako se prema svojim karakteristikama mogu koristiti u poljoprivredi i koje su prednosti korištenja elektropećne troske u poljoprivredi.In the production of the steel by the electric arc furnace process large amounts of slags are formed. Due to the electric arc furnace process, there are two different types of slags, black slag formed in electric arc furnace and white slag formed in ladle furnace slag. Both slags according to physical-chemical characteristic are classified as non-hazardous waste and they can be disposed at the provided landfill. Disposal is attempted to avoid due to high cost, possible soil contamination, loss of landfill, and loss of slags valuable ingredients by disposal. In future European and Croatian politics are zero rate of disposal so there is a need to find how and where we can apply the slag. Thus, slags are used today in construction, road construction and agriculture.
In this paper are present physico-chemical characteristic of black and white slag, how they can be used in agriculture according to their characteristic, and the advantages of using them in agriculture
Microstructural characterization of CuAlMnNi shape memory alloy
Get PDFU ovom radu analiziran je učinak toplinske obrade na mikrostrukturu i tvrdoću Cu-13Al-2,5Mn-2Ni legure s prisjetljivosti oblika.Ingoti (promjera 8 mm i duljine 15 mm) proizvedeni su procesom taljenja i lijevanja. Taljenje je izvedeno pomoću toplinske energije proizvedene električnim lukom te su ingoti ohlađeni vodom u posebno konstruiranoj bakrenoj anodi, koja je također služila i kao kalup za lijevanje. Uzorci su analizirani u lijevanom te u kaljenom stanju (900 °C /15 min/H2O). Mikrostrukturna analiza je provedena pomoću optičke mikroskopije (OM), pretražne elektronske mikroskopije (SEM) opremljene uređajem za energetsko disperzijsku spektroskopiju (EDS) te pomoću diferencijalne skenirajuće kalorimetrije (DSC). Preliminarna metalografska analiza ispitivanog ingota potvrdila je da se mikrostruktura sastoji od martenzita u lijevanom i kaljenom stanju. Ispitivanje tvrdoće provedeno je metodom po Vickersu. Tvrdoća ingota Cu-Al-Ni-Mn legure s prisjetljivosti oblika iznosila je 260,5 HV10, a nakon toplinske obrade 285,6 HV10. DSC analizom određene su temperature faznih transformacija (As,Af,Ms,Mf).In this work the effect of heat treatment on microstructure and hardness of Cu-13Al-2,5Mn-2Ni shape memory alloy was determined.Ingots (8 mm in diameter and 15 mm in length) were produced by melting and casting process. Melting was performed using the heat produced by electric arc and by a water-cooled, specially constructed copper anode that also served as a casting mould. The samples were analysed in as-cast state and in as-quenched state (900 °C/15 min/H2 O). Microstructural analysis was performed by optical microscopy (OM), scanning electron microscopy (SEM) equipped by device for energy dispersive spectroscopy (EDS) and using differential scanning calorimeter (DSC). Preliminary metallographic analysis of investigated ingot confirmed that microstructure was consisted from martensite in both, as-cast and as-quenched state. A hardness measurement was performed by Vickers method. Hardness of Cu-Al-Ni-Mn shape memory alloy ingot was 260.5 HV10, and after heat treatment 285.6 HV10. By DSC analysis the phase transformation temperatures (As,Af,Ms,Mf) were determined
Development and implementation of multicomponent liquid wall film evaporation model for internal combustion engine applications
Get PDFVarious environmental regulations put ever stringent requirements on the automotive industry as a part of solution to the problem of global warming and climate change. Engine emissions are influenced, among others, also with quality of fuel and air mixing process. Auto ignitability of fuel in cylinder depends on detailed chemical composition of the fuel as well as on the evolution of the thermal and compositional state of the fuel mixture. The evaporation of wall film, formed by spray/wall impingement has strong effects on engine emission. This works aims at further development of the numerical model of liquid wall film by implementation and validation of mathematical models of multicomponent wall film evaporation. Two multicomponent liquid film evaporation models were developed, the first one on the basis of analogy between momentum and mass transfer, and the second one employing modified wall functions which take into account influence of the evaporation on boundary layer above liquid film. Particular scientific contribution is in implementation of the UNIFAC method for activity coefficients calculation. Finally, implemented models were compared with available experimental data in order to confirm their validity
Alternative methods of aluminium production
Get PDFU ovom radu dan je pregled alternativnih načina i procesa proizvodnje aluminija. HallHéroultov proces elektrolitičke redukcije glinice razvijen je krajem 19. stoljeća te je još uvijek jedini industrijski proces za proizvodnju aluminija. Svrstan je među energetski najintenzivnije procese i najveće proizvođače CO2. Čak 1 % od ukupne svjetske električne energije troši se na ovaj proces koji ukupnoj svjetskoj emisiji stakleničkih plinova pridonosi s 2,5 %. Kao alternativni procesi predloženi su procesi: direktna karbotermijska redukcija glinice, karbotermijska redukcija pod vakuumom i inertnim plinom, indirektna karbotermijska redukcija te redukcija kaolinita. Svaki od ovih procesa pokazuje izrazit potencijal smanjenja potrošnje energije i emisije štetnih plinova. Međutim, javljaju se određeni problemi koji sprječavaju njihovo uvođenje u industriju (mali izvadak aluminija i previsok udio karbida u aluminiju). Zamjenom HallHeroultovih ugljičnih anoda inertnim anodama, uvođenjem močivih katoda te multipolarnih ćelija troškovi HallHeroultovog procesa znatno bi se smanjili, a proces bi postao prihvatljiviji za okoliš.This paper gives an overview of alternative methods and processes for aluminium production.
The Hall-Héroult process for the electrolytic reduction of alumina was developed at the end of
the 19th century and is still currently the only industrial process for the production of
aluminium. Today this process is ranked among the most energy and CO2 intensive industrial
processes. About 1 % of the globally produced electric energy is consumed by this process
which produces 2.5 % of the World’s anthropogenetic greenhouse gases. Proposed alternative
processes include: direct carbothermic reduction of alumina, carbothermic reduction under
vacuum or inert gas conditions, indirect carbothermic reduction and kaolinite reduction. Every
one of those processes shows distinct potential to reduce energy consumption and greenhouse
gas emissions. However, there are certain problems that hinder their implementation in
industry (low yield and very high carbon content in the product). By replacing Hall Heroult
carbon anodes with inert anodes, wetted cathodes and multipolar cells costs of Hall Heroult
process would decrease considerably and process would become more environmentally
friendly
Analysis of fracture surfaces of the CuAlNi shape memory alloys
Get PDFU ovom radu analizirana je mikrostruktura CuAlNi legure s prisjetljivosti oblika. Ispitivanje
je provedeno na pripremljenim uzorcima u lijevanom i kaljenom stanju. Uzorci su
pripremljeni u vakuum indukcijskoj peći koja je spojena sa uređajem za vertikalno lijevanje.
Postupak lijevanja je proveden u zaštitnoj atmosferi argona, a zatim su pripremljeni za
mikroskopsku analizu brušenjem, poliranjem i nagrizanjem. Mikrostrukturna analiza CuAlNi
legure provedena je svjetlosnim mikroskopom te pretražnim elektronskim mikroskopom.
Rezultati su pokazali da uzorci posjeduju tipičnu martenzitnu mikrostrukturu, a martenzitne
iglice imaju različitu orijentaciju u svakom pojedinom zrnu. Radi ispitivanja mehaničkih
svojstava legure, proveden je statički vlačni pokus, te ispitivanje tvrdoće metodom po
Vickersu. Nakon loma uzorka pri statičnom vlačnom pokusu, provedena je fraktografska
analiza prijelomnih površina CuAlNi legure u lijevanom i kaljenom stanju.In this paper, the microstructure of the CuAlNi shape memory alloy has been analysed.
Examination was conducted on prepared samples in a cast and tempered state. Samples were
produced in a vacuum induction furnace which is connected with a device for vertical casting.
The process was conducted in protective atmosphere of argon, after which they were prepared
for microscopy analysis by grinding, polishing and corrosion. The microstructural analysis of
the CuAlNi shape memory alloy was performed with optical microscopy and scanning
electron microscopy. The results have shown that samples posses a typical martensitic
microstructure. Martensite laths have different orientations inside particular grains. Tensile
testing and hardness testing by the Vickers method were conducted to the determine the
mehanical properties of the CuAlNi shape memory alloy. After the samples fractured during
tensile testing, the analysis of fracture surfaces of the CuAlNi shape memory alloy in cast and
tempered state was conducted