Utjecaj vremena žarenja na svojstva austenitnog nehrđajućeg čelika

master's thesis

• Title (english): The effect of annealing time on properties of austenitic stainless steel
• Author: Katarina Pavičić
• Mentor: Stjepan Kožuh (mentor)
• Committee member: Mirko Gojić (predsjednik povjerenstva)
• Committee member: Stjepan Kožuh (član povjerenstva)
• Committee member: Ivan Jandrlić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2019-09-23, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract

U ovom radu provedena je mikrostrukturna analiza, ispitivanje mikrotvrdoće i udarne radnje
loma austenitnog nehrđajućeg čelika AISI 316L. Ispitivanja su provedena prije i nakon
žarenja na 850 °C. Vrijeme žarenja tijekom ispitivanja je bilo od 30 do 90 minuta. Nakon
žarenja, uzorci su ohlađeni na sobnoj temperaturi. Mikrostrukturna analiza ispitivanih uzoraka
provedena je optičkom mikroskopijom (OM) i pretražnom elektronskom mikroskopijom
(SEM) opremljenom uređajem za energetsko disperzijsku spektroskopiju (EDS). Ispitivanja
udarne radnje loma provedena su na uređaju Charpyju na sobnoj temperaturi. Početno valjano
stanje ispitivanog čelika pokazalo je prisutnost tipičnih izduženih poligonalnih zrna austenita i
delta ferita, dok uzorci nakon žarenja pokazuju prisutnost i razvoj sigma faze u mikrostrukturi
tijekom žarenja. Mikrotvrdoća je mjerena Vickersovom metodom te je utvrđeno da porast
vremena žarenja nema značajniji utjecaj na mikrotvrdoću. Porastom vremena žarenja smanjila
se udarna radnja loma što se može povezati s mikrostrukurnim promjenama. Nakon
ispitivanja udarne radnje loma provedena je fraktografska analiza prijelomnih površina
pomoću pretražnog elektronskog mikroskopa.

Abstract (english)

In this paper, microstructural analysis, microhardness testing and fracture impact tests of
austenitic stainless steel AISI 316L were performed. Investigations were performed before
and after annealing at 850 °C. The annealing time during the investigation was 30 to 90
minutes. After annealing, the samples were cooled down to room temperature.
Microstructural analysis of the investigated samples was performed by optical microscopy
(OM) and scanning electron microscopy (SEM) equipped with device for energy dispersive
spectroscopy (EDS). Impact energy tests were performed on a Charpy device at room
temperature. The initial rolled state of the test steel showed the presence of typical elongated
polygonal grains of austenite and delta ferrite, while after-annealing samples showed the
presence and development of sigma phase in the microstructure during annealing.
Microhardness was measured by the Vickers method and it was found that an increase in
annealing time had no significant effect on microhardness. With increasing annealing time,
the impact energy, which can be associated with microstructural changes, has decreased. After
impact energy testing, fractographic analysis of fracture surfaces was performed using a
scanning electron microscope.

• Keywords: austenitni nehrđajući čelik; mikrostruktura; toplinska obrada; žarenje; udarna radnja loma; mikrotvrdoća
• Keywords (english): austenitic stainless steel; microstructure; heat treatment; annealing; impact energy; microhardness
• Language: croatian
• URN:NBN: urn:nbn:hr:115:687530
• Study programme: Title: Graduate study program Metallurgy; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka metalurgije (magistar/magistra inženjer/inženjerka metalurgije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-10-10 09:20:39