20.500.12556/RUL-183170 Primerjava popuščnih diagramov jekla 34CrAiNi7-10 iz odkovka na različnih globinah diplomsko delo Comparison of tempering diagrams of 34CralNi7-10 steel at various depths in forging diploma work V diplomskem delu so bili izdelani popuščni diagrami jekla 34CrAlNi7-10 iz industrijskega odkovka premera 340 mm. Odkovek je bil toplotno obdelan s poboljšanjem, kaljenje je potekalo s temperature 890 °C, popuščanje pa na 400 °C. Vzorci za preiskave so bili odvzeti iz treh globin preseka, in sicer 12,5 mm, 85 mm (D/4) in 170 mm (jedra), ter popuščani pri različnih temperaturah med 400 °C in 650 °C. Namen raziskave je bil primerjati vpliv različne ohlajevalne hitrosti in mikrostrukture na mehanske lastnosti ter potek popuščnih diagramov glede na globino preseka. Analize so vključevale meritve trdote, natezne preizkuse, določitev udarne žilavosti in metalografsko karakterizacijo. Rezultati so pokazali, da imajo vsi popuščni diagrami značilen potek za malolegirana jekla, da se s povečevanjem temperature popuščanja trdnostne lastnosti zmanjšujejo, žilavost pa raste, vendar se med posameznimi globinami pojavijo izrazite razlike: površina, ki ima popolnoma martenzitno strukturo, dosega največje trdnostne lastnosti in udarno žilavost, medtem ko jedro zaradi več ferita in perlita kaže nižje vrednosti. Območje D/4 predstavlja prehodno cono z vmesnimi mehanskimi lastnostmi, učinek popuščanja pa je manjši. Rezultati potrjujejo, da zaradi ohlajevalnih hitrosti in mikrostrukturne nehomogenosti mehanske lastnosti industrijskih odkovkov pogosto odstopajo, zato laboratorijski popuščni diagrami niso vedno reprezentativni za masivne industrijske izdelke. Ključne besede: konstrukcijsko jeklo 34CrAlNi7-10, popuščni diagram, toplotna obdelava, mikrostruktura, mehanske lastnosti, odkovek. In this thesis, tempering diagrams of 34CrAlNi7-10 steel were created from an industrial forging with a diameter of 340 mm. The forging was heat treated by quenching and tempering: quenching was carried out from 890 °C, followed by tempering at 400 °C. Samples for investigation were taken from three depths of the cross-section, namely 12.5 mm, 85 mm (D/4), and 170 mm (core), and tempered at different temperatures between 400 °C and 650 °C. The purpose of the research was to compare the influence of different cooling rates and microstructures on the mechanical properties and the course of tempering diagrams with respect to the cross sectional depth. The analyses included hardness measurements, tensile tests, determination of impact toughness, and metallographic characterization. The results showed that all tempering diagrams exhibit a characteristic course for low-alloy steels, with increasing tempering temperature leading to a decrease in strength properties and an increase in toughness. However, significant differences occur between the individual depths: the surface, which has a fully martensitic structure, achieves the highest strength properties and impact toughness, while the core, due to a higher content of ferrite and pearlite, shows lower values. The D/4 region represents a transitional zone with intermediate mechanical properties, and the tempering effect is less pronounced. The results confirm that, due to cooling rates and microstructural heterogeneity, the mechanical properties of industrial forgings often deviate, and therefore laboratory tempering diagrams are not always representative of massive industrial products. Keywords: structural steel 34CrAlNi7-10, tempering diagram, heat treatment, microstructure, mechanical properties, forging. Ključne besede: konstrukcijsko jeklo 34CrAlNi7-10 popuščni diagram toplotna obdelava mikrostruktura mehanske lastnosti odkovek. Keywords: structural steel 34CrAlNi7-10 tempering diagram heat treatment microstructure mechanical properties forging. true false false D. Zečić Slovenski jezik Angleški jezik Diplomsko delo/naloga 2026-06-06 09:00:16 2026-06-06 09:00:34 2026-06-11 13:31:28 0000-00-00 00:00:00 2026 0 Ljubljana 0 Ljubljana XII, 36 f. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 669 113911 281318659 29210.pdf 29210.pdf 1 9EB368F00DFFFA01CF489A00C115980B 0c5322f5c5656102fc7c8a69adcb956b03d0d71f2aff462c35af01285ddb2ff5 0b2facaa-6175-11f1-b0ab-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=235037 Naravoslovnotehniška fakulteta 0 0 0