Staranje jekla SINOXX 4542

Foder, Jan (author), Nagode, Aleš (mentor)

Namen diplomske naloge je bil raziskati vpliv staranja izločevalno utrjevalnega nerjavnega jekla SINOXX 4542, na mikrostrukturo in mehanske lastnosti. V teoretičnem delu so predstavljene osnove fizikalne metalurgije jekel, s poudarkom na izločevalnem utrjevanju. Eksperimentalno delo smo razdelili na dva dela. Prvi del obsega matrico preizkusov za popis vseh šestih staranih stanj, ki jih za jeklo 17-4 PH (SINOXX 4542) predpisuje standard SAE AMS5604G. Na vzorcih vzetih iz valjane plošče v raztopno žarjenem stanju smo opravili mehanske preizkuse, ki so zajemali natezni preizkus pri sobni in povišanih temperaturah, preizkus udarne žilavosti po Charpyju, upogibni preizkus in meritve trdote. Dobljene rezultate smo primerjali z vrednostmi, ki jih za starana stanja predpisuje standard. Poleg mehanskih preizkusov je bila izvedena tudi metalografska analiza na svetlobnem in vrstičnem elektronskem mikroskopu (SEM). Drugi del predstavlja občutljivostna analiza določenega staranega stanja (H900). Pri toplotni obdelavi smo variirali čas in temperaturo staranja, nato po opravili mehanske preizkuse, ki so zajemali meritve trdote in natezni preizkus. Dobljene rezultate smo primerjali s predpisanimi vrednostmi. Rezultati podajajo izmerjene mehanske lastnosti, primerjane s standardnimi vrednostmi. Predstavljeni in analizirani so tudi rezultati metalografske analize. Pozorni smo bili na to, kako mikrostrukturne spremembe vplivajo na mehanske lastnosti. Pri popisu staranih stanj smo ugotovili, da večina dobljenih mehanskih lastnosti ustreza vrednostim, ki jih pripisuje standard, z izjemo napetosti tečenja Rp0,2 pri staranem stanju H1150 in raztezka A50 pri staranem stanju H900. Pri občutljivostni analizi smo ugotovili, da v časovnem intervalu med 50 in 65 minut dobimo ustrezne mehanske lastnosti, medtem ko pri 70 minutah vrednost kontrakcije pade pod minimalno predpisano vrednost. Pri variaciji temperature smo dobili ustrezne mehanske lastnosti le pri 490 °C, pri 466 °C in 498 °C pa niso ustrezale standardnim vrednostim.

• Language: Slovenian
• Keywords: jeklo SINOXX 4542, staranje, mehanske lastnosti, metalografija, občutljivostna analiza
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2017
• PID: 20.500.12556/RUL-96418
• COBISS.SI-ID: 1700191
• Publication date in RUL: 02.10.2017

Secondary language

• Language: English
• Title: Ageing of SINOXX 4542 steel

Abstract

Main objective of thesis has been to discover the influence of ageing temperature and time on mechanical properties and microstructure of SINOXX 4542 precipitation hardening stainless steel. Theoretical part explains the basic principles of physical metallurgy of steel with emphasis on precipitation hardening kinetics in Fe-Cu binary phase system. The experimental part is divided into two parts. First part includes heat treatment (ageing) and mechanical testing of specimen, cut from hot rolled plate in solution annealed condition. American standard SAE AMS5604G prescribes 6 ageing conditions for 17-4 PH (SINOXX 4542) stainless steel and mechanical properties for each of them. Mechanical testing included tensile test, Charpy impact test, bending test, hardness test and hot tensile test. Measured mechanical properties were compared to prescribed values. Samples for each of 6 aged and solution treated conditions were metallographically examined with light and scanning electron microscope (SEM). Second part of experimental work was focused on sensitivity analysis for one of aged conditions (H900). Ageing temperature and time were variated. After heat treatment, mechanical tests were conducted. The results from testing were compared with values prescribed by American standard SAE AMS5604G. Results from light and scanning electron microscopy were analysed. The influences of microstructural changes on mechanical properties were studied. Final results showed that most of the measured mechanical properties were within the prescribed values, except yield strength Rp0,2 for aged condition H1150 and elongation A50 for H900. Results for sensitivity analysis of aged condition H900 showed that, we can age from 50 to 65 minutes at 482 °C, or 60 minutes at 490 °C and still reach prescribed values, but we didn’t reach them, when we aged our samples at 498 °C and 466 °C for 60 minutes and at 482 °C for 70 minutes.

• Keywords: SINOXX 4542 steel, ageing, mechanical properties, metallography, sensitivity analysis