Visokotemperaturna oksidacija orodnega jekla SITHERM S140R : diplomsko delo

Broder, Kim (author), Medved, Jožef (mentor), Balaško, Tilen (comentor)

V diplomskem delu smo preiskovali visokotemperaturno oksidacijo orodnega jekla za delo v vročem, SITHERM S140R, proizvajalca SIJ Metal Ravne. Jeklo smo preiskovali v mehko žarjenem stanju, saj ga v takšni obliki dobavlja tudi proizvajalec. Kot primerjalni material smo uporabili čisto železo (99,9 mas. % Fe). Za jeklo smo najprej s termodinamičnem modeliranjem, po metodi CALPHAD, naredili izračun ravnotežnih sestav nastalih oksidnih plasti, nato pa smo dva vzorca oksidirali v napravi za simultano termično analizo (STA naprava), pri temperaturah 500 in 700 °C. Vzorce primerjalnega materiala – železa, smo oksidirali v komorni peči pri temperaturi 700 °C, ki smo jih iz peči vzeli po treh različnih časih, in tako s pomočjo tehtanja izmerili spremembo mase, nastale med oksidacijo. Oksidiranima vzorcema jekla smo s pomočjo metalografske analize izmerili debeline nastalih oksidnih plasti. Na podlagi dobljenih rezultatov, smo izdelali termodinamični model za preiskovano jeklo pri posameznih temperaturah. Z izračuni s Thermo-Calcom smo dobili rezultate vsebnosti posameznih oksidov in njihove kemijske sestave, pri določeni temperaturi. Rezultate kinetike oksidacije, pa smo pridobili z oksidacijo v STA napravi. Kinetiko oksidacije preiskovanega jekla, je možno opisati tudi s tremi matematičnimi funkcijami: eksponentno, parabolno, oziroma kubično funkcijo. Od kemijske sestave jekla in temperature oksidacije pa je odvisno, katera matematična funkcija najboljše opiše kinetiko oksidacije. S preizkusi je bilo ugotovljeno, da imajo legirni elementi velik vpliv na kinetiko oksidacije.

• Language: Slovenian
• Keywords: Visokotemperaturna oksidacija, orodna jekla za delo v vročem, kinetika oksidacije, termodinamično modeliranje, termogravimetrična analiza.
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [K. Broder]
• Year: 2022
• Number of pages: XII, 42 f.
• PID: 20.500.12556/RUL-142045
• UDC: 669
• COBISS.SI-ID: 133423107
• Publication date in RUL: 18.10.2022

BRODER, Kim, 2022, Visokotemperaturna oksidacija orodnega jekla SITHERM S140R : diplomsko delo [online]. Bachelor’s thesis. Ljubljana : K. Broder. [Accessed 11 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=142045

Secondary language

• Language: English
• Title: High temperature oxidation of tool steel SITHERM S140R : diploma work

Abstract

In this thesis we investigated the high temperature oxidation of hot work steel SITHERM S140R, manufactured by SIJ Metal Ravne. We studied the steel in the condition of soft annealing, as it is also issued in this form by the manufacturer. We used pure iron (99.9 wt. % Fe) as a comparative material. For steel, we first calculated the equilibrium compositions of the resulting oxide layers by thermodynamic modelling using the CALPHAD method. Subsequently, two samples were oxidised in a simultaneous thermal analysis apparatus (STA) at temperatures of 500 and 700 °C. Samples of the reference material - iron - were oxidised in a chamber furnace at a temperature of 700 °C and removed from the furnace after three different times. Subsequently, the change in mass that occurred during oxidation was measured by means of weighing. Metallographic analysis was used to measure the thicknesses of the oxide layers that had formed on two oxidised steel samples. Based on the results obtained, we created a thermodynamic model for the steel studied at each temperature. The model developed describes the kinetics of high-temperature oxidation, which is also described by the results of the analysis performed with Thermo-Calc. The kinetics of the investigated steel can also be described with three mathematical functions: exponential, parabolic or cubic function. Which mathematical function best describes the oxidation kinetics depends on the chemical composition of the steel and the oxidation temperature. Through tests, it was found that alloying elements have a great influence on the oxidation kinetics.

• Keywords: High temperature oxidation, hot work tool steels, oxidation kinetics, thermodynamic modelling, thermogravimetric analysis.