Vpliv deformacijske hitrosti na mehanske lastnosti jekla PK11SP mikrolegiranega s titanom

Tomažič, Tanja (author), Fajfar, Peter (mentor), Šuler, Blaž (comentor)

Namen diplomskega dela z naslovom Vpliv deformacijske hitrosti na mehanske lastnosti jekla PK11SP mikrolegiranega s titanom je bilo ugotoviti kakšen je vpliv deformacijske hitrosti na mehanske lastnosti jekla PK11SP pri enaki kemijski sestavi, začetni temperaturi kovanja/valjanja, stopnji deformacije in enakem postopku toplotne obdelave. Jeklo PK11SP je avstenitno nerjavno jeklo, stabilizirano s titanom. Glavni namen titana je, da se preprečuje vezavo ogljika s kromom v kromov karbid, pri čemer se prepreči nastajanje kromovih karbidov na mejah kristalnih zrn. Glavni cilj je nastajanje titanovega karbida, saj ima titan višjo afiniteto do ogljika kot krom. S tem se poveča odpornost jekla na interkristalno korozijo. Kot vhodni material smo uporabili ingot iste šarže. Iz ingota smo zvaljali gredico in jo razdelili na štiri kose. Vsakega od kosov smo preoblikovali z drugim tehnološkim postopkom: valjanje na srednji progi, kovanje na kovaškem kladivu in kovanje na kovaški stiskalnici. V vseh primerih so bile začetne temperature preoblikovanja enake. Prav tako so bile enake končne dimenzije palic premera 35 mm. Razlika je bila le v končnih temperaturah in deformacijskih hitrostih. Po izdelavi smo polizdelke gasili v vodi. Iz polizdelkov bomo naredili preizkušance za mehanske preizkuse: natezni preizkus (pri sobni temperaturi), test žilavosti ter izmerili trdote po Brinellu. Z metalografskimi raziskavami smo določili velikost kristalnih zrn. Najvišje vrednosti natezne trdnosti dosegamo z hitrostjo deformacije 7 s-1 pri isti hitrosti deformacije pa zabeležimo tudi na splošno najvišje vrednosti žilavosti. Pri hitrosti 5 s-1 pa zabeležimo najvišje vrednosti napetosti tečenja, kontrakcije, raztezka in trdote.

• Language: Slovenian
• Keywords: avstenitno nerjavno jeklo, PK11SP, deformacijska hitrost, mehanske lastnosti.
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2020
• PID: 20.500.12556/RUL-120909
• COBISS.SI-ID: 32974851
• Publication date in RUL: 26.09.2020

TOMAŽIČ, Tanja, 2020, Vpliv deformacijske hitrosti na mehanske lastnosti jekla PK11SP mikrolegiranega s titanom [online]. Bachelor’s thesis. [Accessed 30 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=120909

Secondary language

• Language: English
• Title: Effect of strain rate on mechanical properties of PK11SP steel microalloyed with titanium

Abstract

The purpose of this diploma thesis entitled The Effects of strain rate on mechanical properties of PK11SP steel microalloyed with titanium was to determine the influence of strain rate on mechanical properties of PK11SP steel at the same chemical composition, initial forging/rolling temperature, deformation rate and the same heat treatment. PK11SP is an austenitic stainless steel, stabilized with titanium. The main purpose of titanium as a microalloying element is to prevent the binding of chromium and carbon and the formation of chromium carbides which would if the formation occurred form on the boundaries of the crystal grains and would have caused corrosion on the grain boundaries (intergranular corrosion). As input material we used an ingot of the same batch. We rolled the ingot into a billet and divided it into four pieces. Then every piece was processed with a different technological process. We used rolling (on the middle track), forging with a forging hammer and forging with a forging press. In all cases (all of four pieces) the initial temperature stayed the same. So were the final dimensions of the rods (35 mm in the diameter). The difference was only in the final temperatures and the strain rates. After production, the semi-finished products were quenched in water. From the semi-finished products, the specimens for mechanical tests were produced. The tests that have been performed were tensile test at room temperature, toughness test and Brinell hardness measurements were taken. At the end the grain size measurements were made with the use of metallographic techniques for determination of grain size. After the tests we concluded that the highest tensile strengths were obtained after strain rate 7 s-1. At the same strain rate we also obtained the highest values of toughness. At the strain rate 5 s-1 we obtained the highest values of yield stress, contraction, elongation and hardness.

• Keywords: austenitic stainless steel, PK11SP, strain rate, mechanical properties.