Mikrostrukturna karakterizacija zavarenog spoja nehrđajućeg super dupleks čelika

undergraduate thesis

• Title (english): Microstructural characterization of super duplex stainless steel welded joint
• Author: Matija Đurasek
• Mentor: Vera Rede (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2019-02-28, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Zbog velikog unosa topline tijekom zavarivanja dupleks čelika narušava se izbalansirana mikrostruktura sastavljena od ferita i austenita u podjednakim udjelima. To može negativno utjecati na korozijsku postojanost i mehanička svojstva ovih čelika. U ovom radu provedena je kvalitativna i kvantitativna analiza mikrostrukture zavarenog spoja super dupleks čelika oznake X2CrNiMoN 25-7-4. Makroanalizom je utvrđeno da zavar ima pravilan oblik i da nema nepravilnosti u zavarenom spoju. Mikrostruktura osnovnog materijala sastoji se od ferita i austenita u podjednakim udjelima. Zona utjecaja topline je izrazito uska, došlo je do raspada dupleks strukture i volumni udio ferita je porastao preko 60%. Metal zavara ima tipičnu ljevačku mikrostrukturu, a udjeli ferita i austenita su u granicama dopuštenog. Najveća mikrotvrdoća izmjerena je u osnovnom materijalu, a najniža u metalu zavara.

Abstract (english)

Because of the great input of heat during welding, the carefuly balanced microstructure, made up of ferrite and austenite in equal parts, is disturbed. This can affect the corrosion resistance and mechanical properties of these steels negatively. In this assignment, qualitative and quantitative analysis of the microstructure of the welded joint of the super-duplex steel grade X2CrNiMoN 25-7-4 was carried out. It was determined by macroanalysis that the weld has the right shape and that there are no irregularities in the welded joint. The microstructure of the base material is made up of equal parts of ferrite and austenite. The heat-affected zone is exceptionally thin, decay of the duplex structure occured and the volume ratio of ferrite increased over 60%. The weld metal has a typical cast microstructure, and the ratios of ferrite and austenite are within allowed limits. The biggest microhardness was measured in the base material, and the lowest in the weld metal.

• Keywords: super dupleks čelik; mikrostruktura; zavareni spoj
• Keywords (english): super-duplex steel; microstructure; welded joint
• Language: croatian
• URN:NBN: urn:nbn:hr:235:514298
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-23 00:12:17