Razogljičenje podevtektoidnih ogljikovih jekel med izotermnim žarjenjem v zračni atmosferi na temperaturah Ac1 < T < Ac3

Zorc, Matija (author), Nagode, Aleš (mentor)

Raziskovalo se je razogljičenje svetlo brušene površine nelegiranih podevtektoidnih jekel C22, C45 in C60 pri različno dolgem žarjenju na temperaturah AC1 < Tž < AC3 v zračni atmosferi. Na teh temperaturah je mikrostruktura omenjenih jekel feritno-avstenitna. Raziskan je bil vpliv temperature in časa žarjenja na debeline razogljičenih plasti v vzorcih omenjenih jekel. Primarni način preiskave vzorcev se je izvajal metalografsko. Opravljena je bila tudi EDS analiza, s katero je bil raziskan vpliv izcej nekaterih legirnih elementov na kinetiko razogljičenja. Teoretična ocena globine razogljičenja je bila izračunana z Van-Ostrand-Deweyevo enačbo. Ugotovljeno je, da ta ustreza tudi za opis razogljičenja na temperaturah AC1 < Tž < AC3, čeprav je bila razvita za razogljičenje avstenita na T > TG. Pri tem je potrebno upoštevati najmanjši znani difuzijski koeficient ogljika v avstenitu. Za eksperimentalne pogoje žarjenj jekel C22, C45 in C60 so bile iz omenjene enačbe razvite poenostavljene enačbe za izračun debelin razogljičenih plasti. Primerjava med izmerjenimi in teoretično izračunanimi debelinami razogljičenja je pokazala zelo veliko ujemanje rezultatov.

• Language: Slovenian
• Keywords: podevtektoidna jekla, razogljičenje, oksidacija, žarjenje, dvofazno področje
• Work type: Master's thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2018
• PID: 20.500.12556/RUL-103299
• COBISS.SI-ID: 1747807
• Publication date in RUL: 15.09.2018

Secondary language

• Language: English
• Title: Decarburization of hypoeutectoid carbon steels during isothermal annealing in air at temperatures Ac1 < T < Ac3

Abstract

Decarburization of hypoeutectoid carbon steels during isothermal annealing in air at temperatures Ac1 < T < AC3 and different annealing times was researched. Aforementioned steels have a dual-phased ferrite-austenite microstructure at these temperatures. The effects of annealing temperatures and times on the depth of decarburization of C22, C45 and C60 steels were researched. Decarburization of samples was primarily researched metallographically. Also the EDS analysis was made, to determine the effects of segregations of certain alloying elements on the kinetics of decarburization. Theoretical calculation of the depth of decarburization was made by Van-Ostrand-Dewey equation. It was found out that this equation is also suitable for calculating the decarburization at AC1 < Tž < AC3 even though it was primarily meant for the decarburization of austenite at T > TG. The lowest known value of the diffusion coefficient of carbon needs to be used with this equation. Equations, that can be used for calculation of the theoretical depths of decarburization for experimental conditions used in this thesis, were created from Van-Ostrand-Dewey equation. The comparison between measured and calculated results shows high levels of matching.

• Keywords: hypoeutectoid steels, decarburization, oxidation, annealing, dual-phased region