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The steel production process as a factor of environmental pollution by radionuclides
Get PDFProizvodnja čelika oporabom čeličnog otpada u posljednji 30-tak godina predstavlja
vrlo važnu industrijsku djelatnost širom svijeta čemu je doprinijela njena društvena i ekološka
korisnost koja se ogleda u čuvanju prirodnih izvora željezne rude i štednji energije. Međutim,
istovremeno je u ovoj djelatnosti zabilježen veći broj nesretnih slučajeva uzrokovanih
pojavom radioaktivnih tvari u čeličnom otpadu namijenjenom recikliranju. Posljedice tih
nezgoda bile su vrlo ozbiljne s obzirom na zaštitu ljudskog zdravlja i okoliša od štetnih
učinaka ionizirajućeg zračenja, a jednako tako i sa gospodarskog stajališta.
U ovom radu je ukazano na razloge i potrebu uvođenja sustava za nadzor i praćenje
radionuklida u čeličanama i ljevaonicama, čime bi se unaprijedio sustav upravljanja
kvalitetom i okolišem bez kojeg se ne može zamisliti niti jedan suvremeni proizvođač čelika i
čeličnih odljevaka. Izgradnja monitoring sustava za nadzor radionuklida u proizvodnim
procesima čeličana i ljevaonica istovremeno predstavlja jamstvo konkurentnosti njihovih
proizvoda na europskom i svjetskom tržištu koja su sve zahtjevnija glede kvalitete ovih
proizvoda i sve češće se zahtjeva certifikat o sadržaju radionuklida.
U radu su prikazani osnovni tipovi sustava za nadzor i praćenje radionuklida, najčešći
zahtjevi koje trebaju ispunjavati ovakvi uređaji, te tijek provedbe mjerenja i dojavljivanja pri
monitoringu radionuklida u čeličnom otpadu. Istovremeno je ukazano i na potrebu za
monitoringom radionuklida u gotovim proizvodima čeličana, kao i stanje monitoringa
radionuklida u hrvatskim čeličanama.The steel production by recovery of steel scrap in the last 30 years is a very important
industrial activity worldwide, which has contributed to its social and ecological utility, which
is reflected in the preservation of natural sources of iron ore and energy saving. However, at
the same time, a number of incidents have been reported in this activity, caused by the
occurrence of radioactive substances in steel scrap intended for recycling. The consequences
of these incidents were very serious in terms of protecting human health and the environment
from the harmful effects of ionizing radiation, as well as from an economic point of view.
This paper presents the reasons and the need to introducing radionuclide monitoring in
steel mills to improve the quality and environmental management system without which no
modern steel manufacturer can be imagined. The construction of a monitoring system for
radionuclide in steel mills processes in the same time represents a guarantee of the
competitiveness of their products on the European and world market which is increasingly
demanding on the quality of these products and increasingly requires a certificate of
radionuclide content.
This paper presents the basic types of radionuclide monitoring systems, the most
common requirements to be met by such devices, and the process of measurement and
imaging monitoring of radionuclide in steel scrap. At the same time, the need for monitoring
of radionuclide in steel products and the status of radionuclide monitoring in Croatian steel
mills was also showed
The influence of strain rate on mechanical properties and beginning of plastic flow of low carbon steel
Get PDFČelik danas predstavlja jedan od najvažnijih tehničkih materijala. Niskougljični čelici čine važnu komponentu u raznim konstrukcijama. Niskougljični čelici uslijed zadovoljavajućih mehaničkih svojstava, dobre deformabilnosti i mogućnosti površinske obrade uvelike se koriste u proizvodnji traka, limova, i žica za gradnju u autoindustriji.Ovaj završni rad kroz teorijski dio daje osvrt na čelike, hladnu deformaciju čelika, te utjecaj brzine deformacije na granicu razvlačenja, vlačnu čvrstoću i druga mehanička svojstva niskougljičnih čelika. Kroz eksperimentalni dio istraživan je utjecaj promjene brzine razvlačenja na mehanička svojstva i početak plastičnog toka niskougljičnog konstrukcijskog čelika ST52-3N. Ispitivanja su provedena statičkim vlačnim pokusom u rasponu brzina razvlačenja uzoraka od 5 – 60 mm/min. Analiza rezultata ispitivanja provedena je korištenjem programskog paketa MATLAB. Dokazano je kakoporastbrzinerazvlačenjautječenamehaničkasvojstvaispitivanogčelika. Porastom brzine rastugranica proporcionalnosti (Rp) i vlačna čvrstoća(Rm),uz istovremeno smanjenje izduženja. Utjecaj brzine se najbolje očituje iz smanjenja omjera Rp/Rm, što pokazuje da povećanje brzine doprinosi porastu elastične deformacije. Korištenjem Matlab regression learner aplikacije kreiran je jednostavni matematički model koji nastoji prikazati korelaciju između mehaničkih svojstava čelika i različite brzine razvlačenja.Today, steel is one of the most important technical materials. Low carbon steels make important component in various constructions. Low carbon steels are widely used in construction and automotive industry for sheets, wires, or strips due to their satisfactory mechanical properties, decent deformability and possibility of surface machining. This final thesis gives an theoretical overwiev on steels, cold deformation of steels, the effects of strain rate on yield point, ultimate tensile strenght, and other mechanical properties of low carbon steels. The effects of drawing rate on mechanical properties and beginning of plastic flow of low carbon steel ST52-3N, are investigated in experimental part of thesis. Experiments are conducted by static tensile test on samples applying drawing rates in span of 5 – 60 mm/min.
The analysis of the test results was carried out using the MATLAB software package.
It has been proven that increase in stretching rate effects mechanical properties of tested steel. Rp and Rm increase with increasing strain rate, simultaneously decreasing elongation.
The effect of strain rate is best seen in the reduction of Rp / Rm ratio, which indicates that the increase in strain rate promotes elastic deformation. Using a Matlab regression learner application, a simple mathematical model was created that shows the correlation between mechanical properties of steel and different rates of stretching
Book of Abstracts of 17th International Foundrymen Conference: Hi-tech casting solution and knowledge based engineering
No full textFoundry industry as a base branch represents an important factor contributing to the economic potential of each country. Current market development as well as technical and economic objective, the production of high-quality, low- cost and environmentally friendly casting, requires application of recent and advanced materials, as well as production technologies, followed and supported by understanding of production process. Production imperative is pointed into the recent technologies and improved materials for everyday usage in our homes, workplaces, as well as materials with special requirements for specific applications such as those for the automotive or space industry. Industrial activities, which are defined as strategic activities in the Republic of Croatia are Metal Casting and Production of Final Metal Products, recognized as "economic growth drivers" because they are expected to realize higher rates of growth and employment. Hi-Tech casting solution comprehends to recent technology and educated and skilled engineers. The Conference topics were designed as presentations of the current "state of the art" research in collaboration with industry, and production innovation with the aim to improve the competitiveness. The scope of 17th International Foundrymen Conference (IFC) covers scientific, technological and practical aspects concerning research, development and application of casting technology with the common perspective – increase of competitiveness. Special attention will be focused towards the competitiveness ability of foundries, improvement of materials features and casting technologies, environmental protection as well as subjects connected to the application of castings. During this Conference 44 papers will be presented. Book of Abstracts of the 17th International Foundrymen Conference includes summaries of the papers. The Proceedings book consists of papers in extenso published in electronic format (CD). Full length papers have undergone the international review procedure, done by eminent experts from corresponding fields, but have not undergone linguistic proof reading. Sequence of papers in Proceedings book has been done by category of papers in following order: plenary lectures, invited lectures, oral and poster presentation, and inside the category alphabetically by the first author’s surname. This occasion represents the opportunity to discuss and increase the mutual collaboration between HEIs’ and industry with the aim of information exchange related to advanced experience in foundry processes and technologies, gaining the new experience in presentation and / or teaching process within lifelong learning process
Effect of casting wall thickness on graphite morfology in ferritic ductile iron strengthened by silicon
Get PDFU ovom diplomskom radu analiziran je utjecaj debljine stijenke odljevka na morfologiju grafita u feritnom silicijem očvrsnutom nodularnom lijevu. Ukupno su izrađene tri taline sa sljedećim udjelima silicija: 3,11, 3,8 i 4,22 %. Analiza je provedena na odljevcima stepenastog oblika koji sadrže sedam stijenki različite debljine: 3, 12, 25, 38, 50, 75 i 100 mm. Dobiveni rezultati pokazuju da se broj nodula/mm2 i nodularnost smanjuju s povećanjem debljine stijenke. Povećanje udjela silicija od 3,11 do 4,22 % rezultiralo je povećanjem broja nodula/mm2 i nodularnosti u stijenkama debljine 3, 12, 25 i 38 mm. Međutim, u debelim stijenkama, tj. stijenkama debljine 50, 75 i 100 mm povećanje udjela silicija rezultiralo je smanjenjem broja nodula/mm2 i nodularnosti. U tim stijenkama, s porastom udjela silicija povećavao se broj jako sitnih nepravilnih grafitnih čestica i nakupina čestica grafita koje po obliku sliče chunky grafitu.Effect of the casting wall thickness on the graphite morphology in ferritic ductile iron strengthened by silicon was analysed in this graduate thesis. Three melts with the following silicon contents were made: 3.11, 3.8 and 4.22 %. The analysis was carried out on stepped castings containing seven different wall thicknesses: 3, 12, 25, 38, 50, 75, and 100 mm. Obtained results show that the nodule count and nodularity decrease with increasing wall thickness. The increase in silicon content from 3.11 to 4.22 % resulted in an increase in nodule count and nodularity in wall thicknesses of 3, 12, 25 and 38 mm. However, in thick walls, i.e. in wall thicknesses of 50, 75 and 100 mm, the increase in silicon content resulted in a decrease in nodule count and nodularity. In these walls, the number of very small irregular graphite particles and clusters of graphite particles that look like chunky graphite increased with the increase in silicon content
Monitoring of production and casting properties investigation of EN GJL-200 quality of gray cast iron
Get PDFProizvodnja sivog lijeva složen je proces koji obuhvaća sve grane metalurgije i širok spektar aktivnosti. Prema potrebama tržišta te kvalitativnim i kvantitativnim zahtjevima pred gotovim proizvodom, sustavno se planira strategija proizvodnje i prema tome odabirekvaliteta materijala, ekonomski opravdana tehnologija proizvodnje, sastav uložnog materijala, tehnološka razrada procesa lijevanja i završna obrada odljevaka.
U eksperimentalnom dijelu praćen je postupak lijevanja i svojstva proizvoda: okvira vrata kamina od sivog lijeva kvalitete EN GJL-200. Praćena su svojstva kalupne mješavine namijenjene DISAMATIC® liniji za kalupovanje, kemijski sastav taline i parametri lijevanja te mehanička i mikrostrukturna svojstva odljevaka u sirovom (lijevanom) i površinski obrađenom (emajliranom) stanju.
Utvrđen je utjecaj visokih temperatura pri postupku emajliranja na promjenu mikrostrukture i mehanička svojstva odljevaka od kvalitete sivog lijeva EN GJL-200. Emajliranjem se povećava udio ferita, a dio perlita ide u ferit te se karbidi raspadaju. Utvrđene mikrostrukturne transformacije dovode do smanjenja vlačne čvrstoće i tvrdoće emajliranih uzoraka, ali i pojave duktilno-krhkog loma. Ne-emajlirani uzorci pokazuju krhki lom preko listića grafita i samo djelomično preko većinski feritne metalne osnove.Gray cast iron production is a complex process involving all branches of metallurgy and a wide range of activities. According to the market needs and the qualitative and quantitative requirements of the final product, the strategy of production is systematically planned and therefore material quality, the economically justified production technology, the composition of the charge material, the technological elaboration of the casting process and the final surface treatment of the castings.
In the experimental part, the casting process and product properties were followed: the cast iron frame of gray cast iron quality EN GJL-200. The characteristics of the mould mixture used for the DISAMATIC® moulding line, the chemical composition of the melt, casting parameters, as well as mechanical and microstructural properties of castings in the raw (as-cast) and surface treated (enamelled) state were observed.
The influence of high temperature in the enamelling process on the microstructure change and obtained mechanical properties of gray cast iron EN GJL-200 was determined.Enamelling results in an increase in the ferite ratio in metal matrix, part of perlite transform into ferrite and carbides experience decomposition. Such microstructural transformation resulted in reduced tensile strength and hardness of enamelled samples, as well as mixed tough – brittle fracture. Non-enamelled samples show a brittle fracture across the graphite lamellas andpartially across the mostlyferritic metal matrix
Use of the steel electric arc furnace slag as an additive for the plant nutrition
Get PDFU današnje vrijeme eksponencijalnog rasta korištenja prirodnih resursa, oporaba otpada vodi poboljšanju stanja okoliša te istovremeno može biti i okidač ekonomskog rasta. Europa 2020, specifično, Europska strategija za pametan, održiv i uključiv rast, temelji se na okretanju prema kružnoj ekonomiji koja može osigurati postizanje učinkovitosti korištenja svih prirodnih resursa. Ovome može značajnije doprinijeti učinkovitije gospodarenje otpadom pri čemu se prije svega misli na njegovo bezdeponijsko zbrinjavanje odnosno racionalnije iskorištavanje proizvodnih ostataka, a posebice njihov transfer iz kategorije otpada u kategoriju nusproizvoda. Kako se ovo odnosi na sve industrijske grane, tako je i u metalurgiji, prisutan problem neopravdanog razvrstavanja, po količini najzastupljenijeg proizvodnog ostatka – troske, u otpad umjesto u nusproizvod. Iz ovog razloga, bez obzira na činjenicu da se metalurgija ubraja na najstarije zanate ljudskog roda, još uvijek se provode intenzivna istraživanja primjene metalurške troske u drugim granama industrije i ostalih ljudskih djelatnosti. S obzirom na kemijski sastav troske i njezin relativno visok sadržaj kalcija i magnezija, istraživanja su se provodila na distrično smeđem kiselom tlu uzetog s područja Like u blizini mjesta Smiljan. Biljke su uzgajane u loncima napunjenim sa 2 kg tla bez i sa dodatkom troske. Istraživanje utjecaja troske provedeno je u kontroliranim uvjetima kroz 5 tjedana. Količina troske određena je na temelju rezultata prethodno provedenih istraživanja i primjenjena je u dozi 0, 0, 5, 1, 0, 3, 0, 6, 0 i 9, 0 g kg-1 tla. U ovom radu ispitivan je utjecaj čeličanske, tzv. crne troske na rast kukuruza (Zea mays L.) i usvajanje hranjiva. Dobiveni rezultati ukazuju na pozitivan utjecaj troske na neke pokazatelje rasta i usvajanje N, P2O5, K2O, Ca i Mg
Microscopic analysis of the Cu-Al-Mn-Ni shape memory alloy after heat treatment
No full textIn this work, the microstructure of two nickel content (2.5 and 3.5 wt.%) Cu-Al-Mn-Ni shape memory alloy (SMA) after heat treatment was analyzed. The melting of technically pure was performed in specially designed copper anode which also was used as a casting mould. By this procedure, samples of cylindrical shape, ingots of 8 mm diameter and 15 mm length, were produced. The samples with various nickel content (2.5 and 3.5 wt.%) were subjected to heat treatment procedure. Selected samples were heat treated at 900 °C, held for 15 minutes on that temperature following water quenching. Optical and scanning electron microscopy revealed the presence of β'1 martensite in the microstructure. Microhardness of the samples increase drastically by increasing the nickel content from 2.5 to 3.5%, respectively
Geochemistry of Croatian superhigh-organic- sulphur Raša coal, imported low-S coal, and bottom ash: their Se and trace metal fingerprints in seawater, clover, foliage, and mushroom specimens
Get PDFThe Labin city area has represented the major Croatian coal mining, metal industry, and coal- fired electricity centre for more than two centuries. The domestic superhigh-organic- sulphur (SHOS) Raša coal is a unique variety compared to other coal types worldwide, based on its highest organic sulphur values, up to 11%. It was utilized in the Plomin coal-fired power plant during the period 1970-2000, and was replaced by an imported low-S coal afterwards. This paper presents the levels of S, Se, V, U, Hg, Sr, Cd, Cr, Pb, Cu, and Zn in the two coal types, their bottom ash, seawater, and plant (clover, mushroom, and foliage) specimens collected from the Labin city area, while the sulphate was measured in surface stream water. Their levels were compared with relevant legislative as well as the published data from different world localities. Data analysis was interpreted in the context of past and recent coal combustion activities
Heat recovery from steel slags
Get PDFDanas se čelik najčešće dobiva elektrolučnim postupkom i putem kisikovih konvertera
gdje kao nusproizvod nastaje troska. Troska nastaje tijekom taljenja metala te zbog manje
gustoće od rastaljenog metala, pliva na površini te zaštićuje rastaljeni metal od oksidacije.
Prosječno po toni čelika nastaje 100 kg troske s temperaturom od oko 1650 °C te uzevši u
obzir da se godišnje proizvodi 1.500 milijuna tona čelika u svijetu danas se sve više istražuju
načini iskorištenja topline troske.
Prijašnjih godina, troska se odlagala na tlo ili jame gdje se hladila i skrućivala bez
pokušaja da se iskoristi njezina toplina. U ovom radu opisan je proces proizvodnje čelika
elekrolučnim postupkom i putem kisikovih konvertera te je dan pregled mogućih postupaka
oporabe topline od nastale troske. Do današnjeg dana razvijeno je nekoliko različitih tipova
uređaja za iskorištavanje topline koji se temelje na oporabi topline granuliranjem te kemijsko
faznim promjenama.Today, steel is most often produced by electric arc furnace process and through
oxygen converters, where slag is one of the major byproduct. The slag is a formed during the
melting of metals and because of its less dense than of molten metal, it floats on the surface
and protects the molten metal from oxidation. An average of 100 kg of slags per ton of steel
with a temperature of around 1650 ° C is generated, and considering that 1.500 million tons of
steel is products annually in the world, today more and more ways of using heat from the slag
are explored.
In recent years, the slag was landed on the ground or pit where it was cooled and
solidified without trying to reuse its heat. In this paper the process of steel production by
electric arc furnace process and through oxygen converters, as well as possible heat recovery
processes from the high temperature slag were described. To date, several different heat
recovery method have been developed, which are divided into heat recovery processes by
granulation and based on chemical phase transformations
The effect of annealing on properties of continuously casted Cu - Al alloy
Get PDFU ovom radu je prikazan utjecaj toplinske obrade (ţarenja na 900 °C u trajanju 15 i 30 minuta)
na mikrostrukturu, mikrotvrdoću i mehanička svojstva Cu - 9,1Al legure. Navedena legura
predstavlja predleguru za dobivanje Cu - Al - Mn - Zn legure s efektom prisjetljivosti oblika.
Najprije je proizveden ingot dimenzija Ø 110 x 180 mm koji je pretaljen te kontinuirano
lijevan u oblik cilindrične šipke promjera 8 mm. EDS analiza kemijskog sastava je potvrdila
da je lijevanje Cu - 9,1Al legure uspješno provedeno (proizvedena je legura homogenog
sastava). Optičkom i pretraţnom elektronskom mikroskopijom primijećena je prisutnost
dvofazne α + β mikrostrukture koja se zadrţava i nakon toplinske obrade iako dolazi do
odreĎene mjestimične promjene morfologije α - faze. DSC analizom je primijećena jedna
endotermna promjena toplinskog toka prilikom zagrijavanja koja vjerojatno predstavlja α→β
transformaciju i jedna egzotermna promjena toplinskog toka prilikom hlaĎenja koja vjerojatno
predstavlja β→α transformaciju. Uočene razlike mikrotvrdoće i vlačne čvrstoće su neznatne
dok istezanje opada prilikom duţeg izlaganja ţarenju. Promjene u iznosu kontrakcije
podudaraju se s promjenom vrijednosti granice razvlačenja.In this work it is shown the effect of heat treatment (annealing at 900 °C in duration 15 and 30
minutes) on microstructure, microhardness and mehanical properties of Cu - 9,1Al alloy. This
alloy represents prealloy for production of Cu - Al - Mn - Zn alloy with the shape memory
effect. At first it was produced ingot with dimensions Ø 110 x 180 mm which is remelted and
continously casted in the shape of cylindrical rod with diameter 8 mm. EDS analysis of
chemical composition has affirmed that cast of Cu - 9,1Al alloy is successfully done (alloy
with homogeneous composition is produced). With optical and scanning electron microscopy
was observed existence of dual-phase α + β microstructure which preserves after heat
treatment as well although certain sporadic shape changes of α - phase occurs. On DSC
analysis was noticed one endothermic change of the heat flow during the heating which
probably represents β→α transformation and one exothermic change of the heat flow during
the cooling which probably represents β→α transformation. Differences observed in the
microhardness and tensile strength values are insginificant while the strain decreases with
longer duration of the annealing. Changes in the amount of contraction coincides with
changes in the value of the yield strenght