Napoved mehanskih lastnosti jekel pri kaljenju na osnovi akustične emisije

doktorsko delo

Bor Mojškerc (Author), Janez Grum (Mentor), Tomaž Kek (Co-mentor)

Abstract

Direktno potopno kaljenje se uporablja za izboljšanje mehanskih lastnosti različnih jeklenih strojnih delov. Postopek poteka na način, da se obdelovance segreje na temperaturo avstenitizacije in nato ohladi z gašenjem v gasilnem sredstvu. V okviru disertacije je razvita neporušna metoda nadzora kaljenja jekel na osnovi akustične emisije (AE). V skladu z načrtom eksperimentov so izvedeni številni preizkusi pri različnih pogojih kaljenja in različnih vzorcih. Uporabljena so gasilna sredstva, kot so voda, polimerno-vodna raztopina z različno koncentracijo, deionizirana voda ali slanica. Pri gašenju oddana AE je zajeta z različnimi piezoelektričnimi senzorji. Analizirane so številne karakteristike signalov AE. Poleg zajema AE so izvedene meritve ohlajevalnih krivulj s termoelementi, metalografska analiza, meritve trdote, natezni preizkus, Charpyjev preizkus udarne žilavosti in meritve zaostalih napetosti po metodi rentgenske difrakcije. Vzpostavljena je korelacija karakteristik AE in mehanskih lastnosti pri različnih pogojih kaljenja. Prikazan je vpliv spremembe razmerja med površino in volumnom vzorcev na signale AE. Prikazani sta metodi zaznavanja nečistoč v gasilni kopeli in nastanka razpok na vzorcih. Eksperimentalni rezultati potrjujejo uporabnost metode za nadzor direktnega potopnega kaljenja jekel v industriji.

Keywords

neporušne preiskave;akustična emisija;analiza signalov;kaljenje;mehanske lastnosti;

Data

Language:	Slovenian
Year of publishing:	2019
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FS - Faculty of Mechanical Engineering
Publisher:	[B. Mojškerc]
UDC:	669.18:620.179.17(043.3)
COBISS:	16932379
Views:	1096
Downloads:	230
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	Prediction of mechanical properties of steel during the quenching process, based on acoustic emission
Secondary abstract:	The direct immersion quenching process is used in order to improve mechanical properties of different steel machine parts. During the process, workpieces are heated to a specific austenitization temperature and then quenched in a quenching bath. In this dissertation, a non-destructive method of monitoring the steel quenching process using acoustic emission (AE) technology is developed. Numerous experiments for different quenching conditions and specimens are performed. Quenchants such as water, aqueous-polymer solution with different concentration, deionized water or aqueous-brine solution are used. The emitted AE is recorded using different piezoelectric sensors. Numerous AE signal characteristics are analysed. In addition to AE recordings, cooling curves, metallographic analysis, hardness measurements, tensile tests, Charpy impact toughness tests and residual stress x-ray diffraction measurements are performed. A correlation of AE characteristics and mechanical properties is established for different quenching conditions. The influence of specimen surface area to volume ratio on emitted AE signals is presented. Methods for detection of quenching bath contamination and specimen cracking are developed. The experimental results confirm the applicability of the presented method for monitoring the direct immersion steel quenching process in the heat treatment industry.
Secondary keywords:	dissertations;non-destructive testing;acoustic emission;signal analysis;quenching;mechanical properties;Jeklo;Disertacije;Kaljenje;Mehanske lastnosti;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za strojništvo
Pages:	XXVI, [133] str.
ID:	11287898