20.500.12556/RUL-99181 Razvoj mikrostrukture jekla X11CrNiMo12 modificiranega s Ti in Zr Development of microstructure of steel X11CrNiMo12 modified with Ti and Zr Glavni cilj doktorske naloge je bil ugotoviti vpliv cirkonija in titana na razvoj mikrostrukture ter vpliv na mehanske lastnosti jekla X11CrNiMo12. Poseben poudarek je bil na preiskavi vpliva cirkonija in titana na nekovinske vključke. V ta namen smo izdelali dve seriji laboratorijskih šarž z dodatkom cirkonija in titana. Vzorce iz teh šarž smo plastično preoblikovali ter jih ustrezno toplotno obdelali. Vzorcem smo določili kemijsko sestavo in jih pregledali s svetlobnim ter elektronskim vrstičnim mikroskopom ter jim določili mehanske lastnosti. Dodatek cirkonija in titana ima pri jeklu X11CrNiMo12 izrazit pozitiven vpliv na velikost prvotnih kristalnih zrn ter na dosežene vrednosti udarne žilavosti po Charpyu, pri tem pa ne pride do poslabšanja trdnostnih lastnosti. Z dodatkom titana in cirkonija pride do nastanka novih tipov nekovinskih vključkov. Najmanjše velikosti so oksidi na osnovi cirkonija, ki so ob enem ugodne sferične oblike. Dodatek cirkonija ima tudi največji pozitiven vpliv na izboljšanje žilavosti. S presežnim deležem titana oziroma cirkonija v mikrostrukturi nastanejo nitridi, pri tem oksidi na osnovi titana in cirkonija služijo kot heterogene kali za tvorbo nitridov, kar negativno vpliva na mehanske lastnosti. The overall focus of investigations was to identify the influence of zirconium and titanium upon development of the microstructure and mechanical properties of X11CrNiMo12 steel. Special emphasis was laid on investigations of the influence of zirconium and titanium upon non metallic inclusions. For this purpose we made two series of laboratory heats with an addition of zirconium and titanium. Samples from these heats were subjected to forging and to a proper heat treatment. We examined chemical composition of samples and tested them with the use of optical and scanning electron microscopes. We also defined their mechanical properties. The zirconium and titanium additions have a very positive influence upon the size of prior austenitic crystal grains of X11CrNiMo12 steel and upon the achieved values of Charpy notched bar impact test where strength properties do not worsen. Added titanium and zirconium result in the development of new types of non-metallic inclusions. Zirconium-based oxides, which have at the same time a favourable spherical form, are the smallest in size. Zirconium addition also has the largest positive influence upon toughness improvement. With excessive share of titanium and/or zirconium, nitrides develop in the microstructure whereby titanium and zirconium-based oxides serve as a heterogeneous nucleus for the formation of nitrides which has a negative impact upon mechanical properties. jeklo X11CrNiMo12 modifikacija s Ti in Zr nekovinski vključki mehanske lastnosti razvoj mikostrukture steel X11CrNiMo12 modification with Ti and Zr nonmetallic inclusions development of microstructure true false false Slovenski jezik Angleški jezik Doktorsko delo/naloga 2018-01-05 07:15:07 2018-01-05 07:15:22 2022-08-16 10:35:43 0000-00-00 00:00:00 2018 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 59918 1712991 590.pdf 590.pdf 1 9410B29C7A9B2CB6C9D15E955C58A01C af9cfe8b1fb657d4bee2bc0e6f84a2edd5b04a689534879e75828e9677c447eb 84c237bf-a1b4-11eb-a523-00155dcfd717 20.500.12556/rul/cb4fb874-c43c-4e32-839f-ab147ad3a009 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=108617 Naravoslovnotehniška fakulteta 0 0 0