20.500.12556/RUL-184158 Vpliv načina legiranja dušika na čistost izdelanega avstenitnega nerjavnega jekla XM-19 diplomsko delo Influence of nitrogen alloying technology on cleanliness ofproduced austenitic stainless-steel XM-19 diploma work V diplomskem delu je bil obravnavan vpliv načina legiranja dušika na čistočo izdelanega avstenitnega nerjavnega jekla XM-19. Primerjane so bile tri šarže, pri katerih je bilo legiranje dušika izvedeno z vpihavanjem skozi kopje (šarža 331352), s kombinacijo kopja in argonskega kamna (šarža 331821) ter z dodatkom nitrirane ferokromove legure FeCrLC-N (šarža 334288). Namen dela je bil ugotoviti, kako izbrani načini vnosa dušika vplivajo na število, velikost in kemično sestavo oksidnih vključkov. V eksperimentalnem delu so bili analizirani končni VOD vzorci vseh treh šarž in dodatni vzorec iz vmesne ponovce naprave za kontinuirno ulivanje pri šarži 331821. Za vrednotenje čistoče jekla sta bili uporabljeni analiza skupnega kisika in avtomatska analiza vključkov z vrstičnim elektronskim mikroskopom, primerjane pa so bile tudi kemične sestave žlinder v različnih fazah izdelave. Pri vseh treh tehnoloških pristopih je bila v končnem jeklu dosežena ciljna vsebnost dušika. Avtomatska analiza je pokazala, da v vseh vzorcih prevladujejo oksidni vključki sistema CaO–Al2O3–MgO, pri čemer so pri šarži 334288 izraziteje prisotni Ca-aluminatni vključki, šarži 331352 in 331821 pa vsebujeta več trdnih aluminatnih oziroma špinelnih faz. Analiza skupnega kisika je pokazala, da je bila med končnimi VOD vzorci najčistejša šarža 334288, šarža 331352 pa je imela najvišjo vsebnost kisika; dodatni vzorec iz vmesne ponovce šarže 331821 je izkazal najnižjo vrednost skupnega kisika in s tem nadaljnje izplavanje vključkov v tej fazi procesa. Dušičenje prek argonskega kamna je doseglo višji izkoristek vnosa dušika in stabilnejši potek procesa kot dušičenje z dušikovim kopjem. Legiranje z nitrirano ferozlitino FeCrLC-N je prav tako omogočilo doseganje ciljne vsebnosti dušika, pri čemer je avtomatska analiza zaznala pomik kemije vključkov v smer kalcijevih aluminatov, rezultati skupnega kisika pa so pokazali še bolj čisto jeklo v primerjavi z ostalima šaržama. Ugotovljeno je bilo, da za zanesljivo oceno čistosti jekla XM-19 najbolje služi kombinacija analiz skupnega kisika in avtomatskih analiz vključkov, pri čemer slednje omogočajo predvsem vpogled v kemično sestavo in velikost vključkov. In this diploma thesis, the influence of nitrogen alloying technology on the cleanliness of austenitic stainless steel XM‑19 was investigated. Three industrial heats were compared in which nitrogen was introduced by different routes: by top blowing through a lance (heat 331352), by a combination of lance blowing and bottom stirring via an argon purging plug (heat 331821), and by the addition of a nitrogen‑bearing ferrochromium alloy (heat 334288). The aim of the work was to determine how the selected nitrogen alloying methods affect the number, size and chemical composition of oxide inclusions. In the experimental part, final VOD samples from all three heats were analysed, together with an additional sample taken from the intermediate tundish of the continuous casting machine for heat 331821. Steel cleanliness was evaluated by total oxygen analysis and automated inclusion analysis using a field emission scanning electron microscope. The chemical compositions of slags in different process stages were also compared. For all three technological routes, the target nitrogen content was achieved in the final steel. Automated inclusion analysis showed that oxide inclusions within the CaO Al2O3–MgO system dominate in all samples, with Ca-aluminate inclusions being more pronounced in heat 334288, while heats 331352 and 331821 contain a higher fraction of solid aluminates and spinel phases. Total oxygen analysis revealed that, among the final VOD samples, heat 334288 was the cleanest, whereas heat 331352 exhibited the highest oxygen content; the additional tundish sample from heat 331821 showed the lowest total oxygen level, confirming further inclusion flotation at this stage of the process. Nitrogen alloying via the argon purging plug achieved a higher nitrogen yield and a more stable process than nitrogen blowing with a top lance. Alloying with the nitrided ferroalloy FeCrLC-N likewise enabled the target nitrogen content to be reached, with automated analysis indicating a shift in inclusion chemistry towards Ca-aluminate compositions, while total oxygen measurements pointed to an even cleaner steel compared to the other two heats. It was found that a reliable assessment of the cleanliness of XM-19 steel is best obtained by combining total oxygen measurements with automated inclusion analysis, the latter primarily providing insight into the chemical composition and size of non-metallic inclusions. avstenitno nerjavno jeklo XM-19 legiranje dušika nekovinski vključki čistoča jekla austenitic stainless steel XM‑19 nitrogen alloying non‑metallic inclusions steel cleanliness true false false J. Cerkovnik Slovenski jezik Angleški jezik Diplomsko delo/naloga 2026-07-01 09:00:06 2026-07-01 09:00:19 2026-07-13 13:27:00 0000-00-00 00:00:00 2026 0 Ljubljana 0 Ljubljana XIII, 48 f. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 669 114136 284579587 29493.pdf 29493.pdf 1 FFE263E380AF176CD51D6021843BE1C4 58777a0cbd906cfac57d6af28ab87883f994d1d9d1601a6d2a9a73bda4bcc330 6aacce53-751a-11f1-9b0d-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=236681 Naravoslovnotehniška fakulteta 0 0 0