diplomsko delo
Luka Herceg (Author), Aleš Nagode (Mentor), Matej Poročnik (Co-mentor)

Abstract

V okviru diplomskega dela smo preučevali vpliv različnih kombinacij toplotnih obdelav na mehanske lastnosti konstrukcijskega jekla SIQUAL 7765. Jeklo je bilo v obliki palic premera cca 30 – 40 mm, ki so bile izdelane po dveh postopkih vroče predelave t. j. z valjanjem in s kovanjem. S pomočjo dilatometrske analize smo določili premenske temperature Ac1 = 770 °C, Ac3 = 843 °C, ter Ms = 370 °C in Mf = 200 °C, s katerimi smo določili optimalne parametre toplotnih obdelav. Toplotno obdelavo smo izvedli na tri načine in sicer tako, da smo en par vzorcev perlitizirali in poboljšali, drugi par smo sferodizacijsko žarili in poboljšali, tretji par pa smo zgolj poboljšali. Temperature poboljšanja so bile pri vseh vzorcih enake in sicer: temperatura avstenitizacije T? = 880 °C in temperatura popuščanja Tp = 640 °C. Meritve trdote smo izvedli na jeklu v dostavljenem stanju, pred in po poboljšanju. Preizkusi udarne žilavosti so bili narejeni pri sobni temperaturi in pri temperaturi -40 °C. Prav tako smo določili napetost tečenja, trdnost, raztezek in kontrakcijo ter analizirali mikrostrukturo. Najboljše razultate, to je najvišje trdnostne lastnosti in žilavosti, smo dosegli na valjanem vzorcu, na katerem je bila izvedena kombinacija sferodizacijskega žarjenja in poboljšanja. Poleg najvišje dogovorne napetosti tečenja in natezne trdnosti, smo dobili tudi najvišjo žilavost pri temperaturi -40 °C.

Keywords

jeklo SIQUAL 7765;mehanske lastnosti;toplotna obdelava;žilavost;metalografska analiza;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL NTF - Faculty of Natural Sciences and Engineering
Publisher: [L. Herceg]
UDC: 669
COBISS: 141913347 Link will open in a new window
Views: 28
Downloads: 6
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Other data

Secondary language: English
Secondary title: ǂ theǂ effect of different heat treatments on mechanical properties of SIQUAL 7765
Secondary abstract: As a part of this thesis, we studied the influence of different combinations of heat treatments on the mechanical properties of structural steel SIQUAL 7765. The steel was in the form of bars with diameter of approx. 30 – 40 mm, which were made by two hot forming processes – rolling and forging. With the help of dilatometer analysis, we determined the variable temperatures Ac1 = 770 °C, Ac3 = 843 °C, Ms = 370 °C and Mf = 200 °C, by which the optimal methods of heat treatment was determined. The heat treatment was carried out in three ways: one pair of samples was pearlitizated, quenched and tempered, the second pair was spheroidizational annealed, quenched and tempered, and the third pair was only quenched and tempered. The temperatures of austenitisation (Tγ) and tempering (Tp) were the same for all samples, namely 880 °C and 640 °C, respectively. The hardness measurements were performed on the steel in its delivered state, before / after quenching and tempering. The impact toughness tests were done at room temperature and at -40 °C. We also determined the yield stress, tensile strength, elongation, contraction and analyzed the microstructure. The best results, i. e. the highest strength properties and toughness, were achieved on the rolled sample, where a combination of spheroidization annealing, hardening and tempering was carried out. In addition to the highest agreed yield stress and tensile strenght, we also obtained the highest toughness at a temperature of -40 °C
Secondary keywords: SIQUAL 7765 steel;mechanical properties;heat treatment;toughness;metallographic analysis;
Type (COBISS): Bachelor thesis/paper
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Naravoslovnotehniška fak., Oddelek za materiale in metalurgijo
Pages: XIII, 35 f.
ID: 17946845