Konstitucijske značilnosti jekel za elektroindustrijo

Kvasič, Brina (author), Markoli, Boštjan (mentor), Foder, Jan (comentor)

V diplomski nalogi smo obravnavali konstitucijske lastnosti jekel v elektroindustriji. Elektroindustrija je hitro rastoča in razvijajoča se industrija, ki se ukvarja z proizvodnjo, transportom, razdelitvijo in prodajo električne energije. V nalogi smo se skoncentrirali na tri vrste jekel podjetja SIJ Acroni d.o.o., ki so ključna za vsako izmed omenjenih področij elektroindustrije. Obravnavali smo neorientirano elektropločevino tipa EV22Al10, avstenitno nerjavno jeklo tipa 316 L in visokotrdnostno poboljšano konstrukcijsko jeklo tipa S690QL. Predstavljene so bile lastnosti posameznih jekel, po katerih se najbolj ločijo od ostalih vrst ter so razlog, zakaj se odločamo zanje. Poseben povdarek je bil na mikrostrukturi, kako le-ta vpliva na razvoj lastnosti ter njeno spreminjanje tekom različnih toplotnih obdelav. Poznavanje mikrostrukture in njenega vpliva je namreč ključno za doseganje želenih lastnosti in kakovosti izdelka ter načrtovanje njegove nadaljnje obdelave ali uporabe. V okviru eksperimentalnega dela so bili metalografsko pripravljeni vzorci obravnavanih jekel, ki so bili vzeti iz različnih stopenj izdelave posameznega jekla. Nato pa so bili opazovani pod svetlobnim mikroskopom in primerjani med seboj. Opazovali smo mikrostrukture kontinuirno ulitih slabov, vroče valjanih ter toplotno obdelanih plošč in trakov. Z opazovanjem mikrostrukturnih sprememb tekom posameznih stopenj lahko napovemo tudi spremembe drugih mehanskih lastnosti, kot so trdnost, trdota, duktilnost, žilavost, preoblikovalnost in podobno. Pri neorientirani elektropločevini smo spremljali nastanek feritnih zrn, deformacijo tekom valjanja ter nazadnje še žarjenje z namenom rekristalizacije. Pri nerjavnem jeklu smo imeli sprva v mikrostrukturi velike dendrite, nato pa smo z valjanjem in raztopnim žarjenjem dobili jeklo s homogeno avstenitno mikrostrukturo. Začetna mikrostruktura visokotrdnostnega poboljšanega konstrukcijskega jekla je bil bainit. Jeklo je bilo nato valjano, kaljeno ter popuščano, dokler vzorec z zadnje stopnje ni vseboval bainitno – martenzitne mikrostrukture.

• Language: Slovenian
• Keywords: neorientirana elektropločevina, nerjavno jeklo, visokotrdnostno jeklo, mikrostruktura, metalografska analiza
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2024
• PID: 20.500.12556/RUL-162271
• Publication date in RUL: 20.09.2024

Secondary language

• Language: English
• Title: Constitutional characteristics of steel for electrical industry

Abstract

The diploma thesis studies the constitutional characteristics of steel for electrical industry. The electrical industry is a rapidly growing and evolving industry involved in the generation, transport, distribution and sale of electricity. In this thesis, we concentrated on three types of steel from SIJ Acroni d.o.o., which are key in each of these areas of electrical industry. We focused on the non-oriented electrical steel sheet type EV22Al10, the austenitic stainless steel type 316 L and the high-strength low-alloyed steel type S690QL. Specifically, the characteristics of each steel, which most distinguish them from the other types and are the reason why we choose them for specific applications. Particular emphasis was placed on the microstructure, how it influences the development of properties and how it changes during different heat treatments. Knowing the microstructure and its influence is key to achieving the desired properties and quality of the product and to planning its further processing or use. During the experimental work, metallographic samples of the steels in question were prepared and taken from different stages of the production of each steel. They were then observed under a light microscope and compared with each other. The microstructures of continuously cast slabs, hot-rolled and heat-treated plates and strips were observed. By observing the microstructural changes during each stage, changes in other mechanical properties such as strength, hardness, ductility, toughness, formability, etc. can be predicted. In the case of non-oriented electrical sheet, we monitored the formation of ferrite grains, deformation during rolling and lastly annealing for recrystallization. In the case of stainless steel, initially, we had large dendritic branches in the microstructure, and then rolling and solution annealing resulted in a steel with a homogeneous austenitic microstructure. The initial microstructure of the high - strength low - alloyed improved structural steel was martensite. The steel was then rolled, quenched and tempered until the last stage sample contained a bainitic-martensitic microstructure.

• Keywords: non-oriented electrical steel sheets, austenitic stainless steel, high - strength low - alloyed steel, light microscopy, metallographic analysis