Vpliv procesnih parametrov na mehanske lastnosti jekla VCNMO200 : magistrsko delo

Iglar, Boštjan (author), Fajfar, Peter (mentor)

Namen magistrskega dela je bil raziskati vpliv dveh parametrov iz proizvodnega procesa, ki lahko vplivata na razliko v lastnostih materiala v okviru ene serije izdelkov in v okviru enega izdelka. Raziskali smo vpliv plana vtikov in temperature kaljenja. Najprej smo preverili vpliv plana vtikov. Pri tem smo spreminjali velikost deformacije ob posameznem prehodu, pri čemer pa je skupna stopnja predelave ostala enaka. S tem preizkusom smo proučevali vnos napak v strukturo materiala, ter potek poprave in rekristalizacije. Prav tako smo analizirali tudi vpliv toplotne obdelave, natančneje vpliv temperature kaljenja na lastnosti materiala. Material, ki je bil predhodno kovan oz. zvaljan na določeno dimenzijo, smo kalili iz različnih temperatur. Temu pa je sledilo popuščanje v skladu s kakovostnim predpisom podjetja SIJ Metal Ravne in sicer za ves material enako. Od vseh proizvedenih materialov smo odvzeli po dve probi. Izvedli smo natezni preizkus, preizkus udarne žilavosti in metalografske analize. Ugotovil sem, da oba parametra doprineseta k razlikam v mehanskih lastnostih, vendar vsak za sebe ne v tako veliki meri. Če pa pogledamo vsoto vplivov obeh parametrov, pa lahko ugotovimo, da že malenkostne spremembe v tehnološki poti lahko pomenijo velike razlike v lastnosti materiala. Na podlagi vseh pridobljenih rezultatov lahko zaključimo, da dobimo najmanjše odstopanje lastnosti ob kombinaciji enosmernega plana vtikov in visoke temperature kaljenja. Najboljše (optimalne) rezultate pa dobimo ob kombinaciji nežnejšega in grobega plana vtikov ter srednje temperature kaljenja.

• Language: Slovenian
• Keywords: jeklo VCNMO200, plan vtikov, toplotna obdelava, mehanske lastnosti, velikost zrna, mikrostruktura
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [B. Iglar]
• Year: 2022
• Number of pages: XXIV, 83 str.
• PID: 20.500.12556/RUL-139990
• UDC: 669
• COBISS.SI-ID: 131810563
• Publication date in RUL: 09.09.2022

IGLAR, Boštjan, 2022, Vpliv procesnih parametrov na mehanske lastnosti jekla VCNMO200 : magistrsko delo [online]. Master’s thesis. Ljubljana : B. Iglar. [Accessed 16 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=139990

Secondary language

• Language: English
• Title: Effect of process parameters on mechanical properties of VCNMO200 steel : master's thesis

Abstract

The purpose of this master`s thesis was to investigate the effect of pass schedule and quenching temperature on material properties within the scope of one series of products and within the scope of one product. First, we investigated the effect of pass schedule. For each investigated pass schedule, we had different number of passes and different deformation rates for each pass. Final sum of deformation rates was the same for all pass schedules. With this experiment, we have analysed defects in the material as well as recovery and recrystallisation process. We also investigated the effect of quenching temperature on mechanical properties of the material. In the second series, bars were rolled and then quenched from different temperatures. After that, all bars were tempered according to SIJ Metal Ravne`s quality prescription. From each bar we have taken two samples. One from the front and one from the back of the bar. We have performed tensile test, toughness test and metallographic analyses on all samples. We have concluded, that both parameters had effect on mechanical properties, but neither had a significant effect on its own. If we look at the sum of all effects, then we can conclude that even a small deviation in process plans can cause large differences in material properties. We can conclude that minimum deviation occurs when forging is conducted according to 'one way' pass schedule and when quenching is performed from higher temperature. On the other hand, we obtained optimal results with combination of 'soft' and 'rough' pass schedule and medium quenching temperature.

• Keywords: VCNMO200 steel, pass schedule, heat treatment, mechanical properties, grain size, microstructure