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Termodinamična in kinetična optimizacija legiranja žvepla : magistrsko delo
ID Lazarević, Jelena (Author), ID Medved, Jože (Mentor) More about this mentor... This link opens in a new window, ID Burja, Jaka (Comentor)

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Abstract
V jeklarstvu je zelo pomemben vpliv žvepla tako na žlindro kot talino. Raziskovali smo jeklo PK304, njegova glavna lastnost je izboljšana obdelovalnost, kar se da doseči z legiranjem z žveplom, vselej na koncu sekundarne obdelave jeklene taline. To so jekla, ki med mehansko obdelavo z odrezovanjem tvorijo majhne ostružke, kar je ugodnejše tako za obdelovanec kot obdelovalno orodje. Ker izkoristek dodajne žveplene žice zelo niha pri posamezni šarži, smo se poglobili v razumevanje interakcije med talino in žlindro z uporabo empiričnih numeričnih modelov ter simulacijo procesne poti s programskim orodjem ThermoCalc. Iz nekaj preteklih industrijskih šarž smo računali izkoristke dodajnih žic in tako opredelili vplivne dejavnike na izkoristek dodajne žice. Nato smo iz izbranih šarž vzeli tri vzorce ,in sicer, 1. vzorec po degazaciji, 2. vzorec 5 minut po dodatku žvepla in pa 3. vzorec tik pred litjem. Vzeli smo vzorce taline in žlindre. Kemijska analiza jekla in žlindre je bila izvedena z rentgenskim fluorescenčnim spektrometrom XRF. S pomočjo teh rezultatov smo nato ovrednotili nekaj obstoječih numeričnih modelov za določanje sulfidne kapacitete, izračunali aktivnosti oksidov, kisika in žvepla, in končno izračunali tudi porazdelitveno razmerje za žveplo in bazičnost žlindre. S pomočjo izračunov smo jasneje opredelili vpliv posameznih termodinamskih in procesnih parametrov. Na podlagi rezultatov smo ugotovili velik vpliv kemijske sestave in bazičnosti žlindre na izkoristek dodanega žvepla. Eksperimentalne rezultate smo prav tako primerjali s termodinamičnimi simulacijami faznih ravnotežij, njihove vrednosti pa smiselno ovrednotili.

Language:Slovenian
Keywords:jeklo PK304, sulfidna kapaciteta, porazdelitveno razmerje žvepla, bazičnost žlindre, sulfidni vključki
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:NTF - Faculty of Natural Sciences and Engineering
Place of publishing:Ljubljana
Publisher:[J. Lazarević]
Year:2023
Number of pages:XV, 48 f.
PID:20.500.12556/RUL-145112 This link opens in a new window
UDC:669
COBISS.SI-ID:148020995 This link opens in a new window
Publication date in RUL:06.04.2023
Views:675
Downloads:83
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Secondary language

Language:English
Title:Thermodynamic and kinetic optimization of sulphur alloying : master's thesis
Abstract:
The influence of sulfur on both slag and melt is very important in steelmaking. have researched PK304 steel, its main property is improved machinability. Machinability can be achieved by alloying sulfur at the end of the secondary processing of the steel melt. These are steels that form small chips and shavings during mechanical processing by cutting, which is more appropriate and favorable for both the workpiece and the processing tool and machine. Since the yield of additional sulfur wire varies greatly in each batch, we delved into understanding the interaction between melt and slag using empirical numerical models and simulation of the process path with the ThermoCalc software tool. We calculated the yield of sulfur additions and thus defined the influencing factors on the efficiency of the sulfur addition, based on industrial batches. We then took three samples from the selected batches, namely, the 1st sample after degassing, the 2nd sample 5 minutes after the addition of sulfur and the 3rd sample just before casting. Melt and slag samples were taken. Chemical analysis of steel and slag was carried out using an X-ray fluorescence spectrometer XRF. With the help of these results, we then analyzed and evaluated some existing numerical models for determining the sulfide capacity, calculated the activities of oxides, oxygen and sulfur, then finally calculated the distribution ratio for sulfur and the basicity of the slag. With the help of calculations, we have more clearly defined the influence of individual thermodynamic and process parameters. Based on the results, we found a great influence of the slag chemical composition and basicity on the recovery of the added sulfur. The experimental results were also compared with thermodynamic simulations of phase equilibria, and their values were meaningfully evaluated.

Keywords:steel PK304, sulphide capacity, sulfur distribution ratio, slag basicity, sulphide inclusions

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