Reakcije antimona in fosforja z redkimi zemljami v jekleni talini

Šuler, Blaž (author), Medved, Jože (mentor), Burja, Jaka (co-mentor)

V doktorski disertaciji smo raziskovali vpliv dodatka elementov redkih zemelj na mikrostrukturo in mehanske lastnosti jekla 50CrMoV13-1. Pri pregledu literature smo opisali nastanek eksogenih in endogenih nekovinskih vključkov, modifikacijo nekovinskih vključkov ter reakcije elementov redkih zemelj s kisikom, žveplom, fosforjem in oligoelementi. V okviru raziskovalnega dela smo najprej raziskali vpliv elementov redkih zemelj na morfologijo in kemično sestavo nekovinskih vključkov, kjer smo ugotovili, da nastajajo oksidi, sulfidi in oksisulfidi elementov redkih zemelj in da so ti termodinamsko bolj stabilni od oksidov aluminija, silicija, mangana, magnezija ter sulfidov mangana ipd. Novo nastali vključki imajo vpliv na mehanske lastnosti jekla in njegovo mikrostrukturo. V drugem delu doktorske disertacije smo raziskali reakcije nastanka vključkov antimona in fosforja z elementi redkih zemelj. Ugotovili smo, da nastali vključki CeLa(Sb) in CeP povišajo mehanske lastnosti jekla pri sobni temperaturi in -20 °C. Z dodatkom elementov redkih zemelj se zmanjša velikost kristalnih zrn in poveča delež žilavega preloma.

• Language: Slovenian
• Keywords: Jeklo 50CrMoV13-1, nekovinski vključki, modifikacija vključkov z elementi redkih zemelj, termodinamika, mikrostruktura, mehanske lastnosti, model nastanka vključkov z elementi redkih zemelj.
• Work type: Doctoral dissertation
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2019
• PID: 20.500.12556/RUL-108088
• COBISS.SI-ID: 1815647
• Publication date in RUL: 15.06.2019

Secondary language

• Language: English
• Title: Reactions of antimony and phosphorus with rare earth elements in steel melt

Abstract

In the doctoral thesis, we investigated the influence of rare earth element (REM) addition on microstructure and mechanical properties of 50CrMoV13-1 steel. In the literature overview, we described the evolution of exogenic and endogenic non-metallic inclusions, modification of non-metallic inclusions and reactions of rare earth elements with oxygen, sulfur, phosphorus and antimony. During the experimental work, we first investigated the influence of rare earth elements additions on the morphology and chemical composition of the non-metallic inclusions. We found that rare earth oxides, sulfides and oxysulfides are formed. They are much more thermodynamically stable than aluminium, silicon, manganese, magnesium oxides and manganese sulfides. REM inclusions have a big influence on the mechanical properties and the microstructure of steel. In the second part, we investigated the reactions between antimony, phosphorus and rare earth elements. We found out that new inclusions CeLa(Sb) and CeP are formed and that they increase the mechanical properties of the steel at room temperature and at -20 °C. The grain size is decreased and the share of ductile fracture is increased when REMs are added.

• Keywords: Steel 50CrMoV13-1, non-metallic inclusions, modification inclusions with rare earth elements, thermodynamics, microstructure, mechanical properties, evolution of inclusions with rare earth elements.